Patent Application
20230065377
The present disclosure relates generally to the fields of medicine, infectious disease, and immunology. More particular, the disclosure relates to human antibodies binding to alphaviruses such as EEEV, WEEV and VEEV.
The Alphavirus genus consists of three major encephalitic viruses: Eastern equine encephalitis virus (EEEV), Venezuelan equine encephalitis virus (VEEV), and Western equine encephalitis virus (WEEV). As indicated by their names, these encephalitic alphaviruses were identified as the cause of several epidemics of fatal encephalitis among horses (Calisher, 1994; Go et al., 2014; Markoff, 2015). Humans can acquire infection with these viruses, in which the mortality rate is approximately 30-70%, 10%, and 1% for EEEV, WEEV, and VEEV, respectively (Griffin, 2013; 2016; Markoff, 2015). EEEV and VEEV are considered category B priority pathogens due to their threat or previous use as bioterrorism agents (Griffin, 2013; 2015; Sidwell and Smee, 2003).
Additionally, the high mortality rate of up to 70% for EEEV and transmission capabilities for VEEV make these viruses of interest in regard to preventative or therapeutic treatment options (Griffin, 2013; 2015). Currently, there are no antiviral drugs or licensed human vaccines available for these viruses (Griffin, 2013; 2015; Reichert et al., 2009). However, experimental vaccines are available, and several vaccination strategies are in clinical trials (Griffin, 2013; 2015; Markoff, 2015). The antibody response to alphaviruses has been shown to be an important part of the immune response in conferring protective immunity and aiding in the clearance and recovery from infection (Matthews and Roehrig, 1982; Hunt et al., 2011; Levin et al., 1991; Griffin et al., 1997). However, the fundamental molecular and structural mechanisms of action of antibodies in humans to the encephalitic alphaviruses, in particular EEEV, remain poorly defined. Comprehensive characterization of potent monoclonal antibodies (mAbs) within the human antibody repertoire to these viruses is of high clinical significance and will help inform vaccine and therapeutic design against these clinically relevant alphaviruses.
Alphaviruses are classified into at least eight antigenic complexes (Calisher et al., 1980) and consist of up to six potential structural proteins: the capsid protein, E3 protein, E2 glycoprotein, E1 glycoprotein, 6K protein, and the TF protein (Griffin, 2013). The E1 and E2 glycoproteins heterodimerize to form trimeric knobs on the surface of the virus and are tethered via transmembrane domains to the capsid protein beneath the viral membrane (Zhang et al., 2002; Mukhopadhyay et al., 2006). Within these trimers, the E2 glycoprotein radially projects from the viral surface and forms the top of the trimeric knobs while the E1 glycoprotein lies tangential to the virus membrane (Li et al., 2010; Kielian et al., 2010; Zhang et al., 2011). The E2 glycoprotein is involved in receptor binding and the E1 glycoprotein contains the fusion loop for fusion of the virus with the endosomal membrane (Li et al., 2010; Kielian et al., 2010; Zhang et al., 2011). For many alphaviruses, the two glycoproteins are the major targets of murine antibodies (Griffin, 2013; 2015; 1995; Voss et al., 2010). As the more surface exposed glycoprotein, the E2 glycoprotein is the primary target for potent neutralizing murine antibodies (Griffin, 2013; 1995). In particular, murine antibodies bind to the E2 glycoprotein and are suspected to interfere with steps in the virus replication cycle from receptor attachment to viral egress (Sun et al., 2013; Porta et al., 2014; Fox et al., 2015; Long et al., 2015; Jin et al., 2015). Murine antibodies have also been isolated against the E1 glycoprotein (Hunt and Roehrig, 1985). However, most of these antibodies are non-neutralizing (Griffin, 2013; Hunt and Roehrig, 1985).
Of the murine neutralizing antibodies to the E1 glycoprotein, these antibodies rely on proximity to the E2 glycoprotein (Griffin, 2013; Roehrig et al., 1982) to do so or recognize transitional epitopes either exposed during low pH conditions or on the surface of an infected cell (Griffin, 1995).
In comparison to the characterization of murine and human antibodies to alphaviruses such as VEEV, WEEV and CHIKV (Selvarajah et al., 2013; Roehrig and Matthews, 1985; Rico-Hesse et al., 1988; Roehrig et al., 1988; Johnson et al., 1990; Hunt et al., 1990; 1991; Agapov et al., 1994; Hunt and Roehrig, 1985; 1995; Hunt et al., 2010; Smith et al., 2015; Hunt et al., 2006; Hulseweh et al., 2014; Pal et al., 2013; Jin et al., 2015), little is known about how antibodies neutralize or interact with EEEV. Previous research focuses on identification of linear epitopes of EEEV for murine and avian antibodies generated through animal immunization with recombinant E2 glycoprotein (Calisher et al., 1986; Pereboev et al., 1996; Zhao et al., 2012; EnCheng et al., 2013a; 2013b). Thus, knowledge of conformational epitopes that are recognized by human antibodies in the context of natural infection of EEEV is lacking. There are many other gaps in knowledge regarding the human antibody response to EEEV. Some questions that have yet to be addressed involve what are the human immunodominant antigenic determinants, are there correlates of protection and/or therapeutic potential, what are the neutralization mechanism(s) utilized by human mAbs, are there cross-reactive mAbs and, if so, are there cross-neutralizing or cross-protective mAbs, and are Fc-mediated effector functions involved?
Thus, in accordance with the present disclosure, a method of detecting an alphavirus infection in a subject comprising (a) contacting a sample from said subject with an antibody or antibody fragment having clone-paired heavy and light chain CDR sequences from Tables 3 and 4, respectively; and (b) detecting alphavirus in said sample by binding of said antibody or antibody fragment to an alphavirus antigen in said sample. The sample may be is a body fluid, such as blood, sputum, tears, saliva, mucous or serum, semen, cervical or vaginal secretions, amniotic fluid, placental tissues, urine, exudate, transudate, tissue scrapings or feces. The alphavirus may be eastern equine encephalitis virus, western equine encephalitis virus, or Venezuelan equine encephalitis virus. Detection may comprise ELISA, RIA, lateral flow assay or Western blot. The method may further comprise performing steps (a) and (b) a second time and determining a change in alphavirus antigen levels as compared to the first assay.
The antibody or antibody fragment may be encoded by clone-paired variable sequences as set forth in Table 1, may be encoded by light and heavy chain variable sequences having 70%, 80%, or 90% identity to clone-paired variable sequences as set forth in Table 1, or may be encoded by light and heavy chain variable sequences having 95% identity to clone-paired sequences as set forth in Table 1. The antibody or antibody fragment may comprise light and heavy chain variable sequences according to clone-paired sequences from Table 2, may comprise light and heavy chain variable sequences having 70%, 80% or 90% identity to clone-paired sequences from Table 2, or may comprise light and heavy chain variable sequences having 95% identity to clone-paired sequences from Table 2. The antibody fragment may be a recombinant scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, or Fv fragment.
In another embodiment, there is provided a method of treating a subject infected with alphavirus or reducing the likelihood of infection of a subject at risk of contracting alphavirus, comprising delivering to said subject an antibody or antibody fragment having clone-paired heavy and light chain CDR sequences from Tables 3 and 4, respectively. The antibody or antibody fragment may be encoded by clone-paired variable sequences as set forth in Table 1, may be encoded by light and heavy chain variable sequences having 70%, 80%, or 90% identity to clone-paired variable sequences as set forth in Table 1, or may be encoded by light and heavy chain variable sequences having 95% identity to clone-paired sequences as set forth in Table 1. The antibody or antibody fragment may comprise light and heavy chain variable sequences according to clone-paired sequences from Table 2, may comprise light and heavy chain variable sequences having 70%, 80% or 90% identity to clone-paired sequences from Table 2, or may comprise light and heavy chain variable sequences having 95% identity to clone-paired sequences from Table 2.
The antibody may be a chimeric antibody or a bispecific antibody, or wherein the antibody fragment is a recombinant scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, or Fv fragment. The antibody may be an IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody or a recombinant IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody or IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody fragment comprising an Fc portion mutated to alter (eliminate or enhance) FcR interactions, to increase half-life and/or increase therapeutic efficacy, such as a LALA, N297, GASD/ALIE, YTE or LS mutation or glycan modified to alter (eliminate or enhance) FcR interactions such as enzymatic or chemical addition or removal of glycans or expression in a cell line engineered with a defined glycosylating pattern.
The antibody or antibody fragment may be administered prior to infection or after infection. The subject may be a pregnant female, a sexually active female, or a female undergoing fertility treatments. Delivering may comprise antibody or antibody fragment administration, or genetic delivery with an RNA or DNA sequence or vector encoding the antibody or antibody fragment. The alphavirus may be an eastern equine encephalitis virus, western equine encephalitis virus, or Venezuelan equine encephalitis virus.
In yet another embodiment, there is provided a monoclonal antibody, wherein the antibody or antibody fragment is characterized by clone-paired heavy and light chain CDR sequences from Tables 3 and 4, respectively. The antibody or antibody fragment may be encoded by clone-paired variable sequences as set forth in Table 1, may be encoded by light and heavy chain variable sequences having 70%, 80%, or 90% identity to clone-paired variable sequences as set forth in Table 1, or may be encoded by light and heavy chain variable sequences having 95% identity to clone-paired sequences as set forth in Table 1. The antibody or antibody fragment may comprise light and heavy chain variable sequences according to clone-paired sequences from Table 2, may comprise light and heavy chain variable sequences having 70%, 80% or 90% identity to clone-paired sequences from Table 2, or may comprise light and heavy chain variable sequences having 95% identity to clone-paired sequences from Table 2.
The antibody may be a chimeric antibody or a bispecific antibody, or wherein the antibody fragment is a recombinant scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, or Fv fragment. The antibody may be an IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody, or a recombinant IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody or IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody fragment comprising an Fc portion mutated to alter (eliminate or enhance) FcR interactions, to increase half-life and/or increase therapeutic efficacy, such as a LALA, N297, GASD/ALIE, YTE or LS mutation or glycan modified to alter (eliminate or enhance) FcR interactions such as enzymatic or chemical addition or removal of glycans or expression in a cell line engineered with a defined glycosylating pattern. The antibody may be a chimeric antibody, or is bispecific antibody, or wherein said antibody or antibody fragment further comprises a cell penetrating peptide and/or is an intrabody. The alphavirus may be an eastern equine encephalitis virus, western equine encephalitis virus, or Venezuelan equine encephalitis virus.
The monoclonal antibody or antibody fragment may further comprise a domain that facilitates transfer across the blood brain barrier by binding to a transport molecule, thereby facilitating transport into the brain. The transport molecule may be transferrin receptor, heparin-binding EGF, a scavenger receptor AI or BI, EGF receptor, tumor necrosis factor, insulin or insulin-like growth factor receptor, apolipoprotein E receptor 2, leptin receptor, melanotransferrin receptor, or LDL receptor. The domain may be a peptide or an scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, Fv fragment, single domain antibody (nanobody) or wherein said domain is a distinct binding specificity as part of a chimeric or bispecific antibody structure. They may further comprise a domain that facilitates transfer across a mucosal surface, such as the respiratory tract barrier, by binding to a transport molecule, thereby facilitating transport across the mucosal surface.
In still yet another embodiment, there is provided a hybridoma or engineered cell encoding an antibody or antibody fragment wherein the antibody or antibody fragment is characterized by clone-paired heavy and light chain CDR sequences from Tables 3 and 4, respectively. The antibody or antibody fragment may be encoded by clone-paired variable sequences as set forth in Table 1, may be encoded by light and heavy chain variable sequences having 70%, 80%, or 90% identity to clone-paired variable sequences as set forth in Table 1, or may be encoded by light and heavy chain variable sequences having 95% identity to clone-paired sequences as set forth in Table 1. The antibody or antibody fragment may comprise light and heavy chain variable sequences according to clone-paired sequences from Table 2, may comprise light and heavy chain variable sequences having 70%, 80% or 90% identity to clone-paired sequences from Table 2, or may comprise light and heavy chain variable sequences having 95% identity to clone-paired sequences from Table 2.
The antibody may be a chimeric antibody or a bispecific antibody, or wherein the antibody fragment is a recombinant scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, or Fv fragment. The antibody may be an IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody, or a recombinant IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody or IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody fragment comprising an Fc portion mutated to alter (eliminate or enhance) FcR interactions, to increase half-life and/or increase therapeutic efficacy, such as a LALA, N297, GASD/ALIE, YTE or LS mutation or glycan modified to alter (eliminate or enhance) FcR interactions such as enzymatic or chemical addition or removal of glycans or expression in a cell line engineered with a defined glycosylating pattern. The antibody may be a chimeric antibody, or is bispecific antibody, or wherein said antibody or antibody fragment further comprises a cell penetrating peptide and/or is an intrabody. The alphavirus may be an eastern equine encephalitis virus, western equine encephalitis virus, or Venezuelan equine encephalitis virus.
In a further embodiment, there is provided a vaccine formulation comprising one or more antibodies or antibody fragments characterized by clone-paired heavy and light chain CDR sequences from Tables 3 and 4, respectively. The antibody or antibody fragment may be encoded by clone-paired variable sequences as set forth in Table 1, may be encoded by light and heavy chain variable sequences having 70%, 80%, or 90% identity to clone-paired variable sequences as set forth in Table 1, or may be encoded by light and heavy chain variable sequences having 95% identity to clone-paired sequences as set forth in Table 1. The antibody or antibody fragment may comprise light and heavy chain variable sequences according to clone-paired sequences from Table 2, may comprise light and heavy chain variable sequences having 70%, 80% or 90% identity to clone-paired sequences from Table 2, or may comprise light and heavy chain variable sequences having 95% identity to clone-paired sequences from Table 2.
The antibody may be a chimeric antibody or a bispecific antibody, or wherein the antibody fragment is a recombinant scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, or Fv fragment. The antibody may be an IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody, or a recombinant IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody or IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody fragment comprising an Fc portion mutated to alter (eliminate or enhance) FcR interactions, to increase half-life and/or increase therapeutic efficacy, such as a LALA, N297, GASD/ALIE, YTE or LS mutation or glycan modified to alter (eliminate or enhance) FcR interactions such as enzymatic or chemical addition or removal of glycans or expression in a cell line engineered with a defined glycosylating pattern. The antibody may be a chimeric antibody, or is bispecific antibody, or wherein said antibody or antibody fragment further comprises a cell penetrating peptide and/or is an intrabody. The alphavirus may be eastern equine encephalitis virus, western equine encephalitis virus, or Venezuelan equine encephalitis virus.
In yet a further embodiment there is provided a vaccine formulation comprising one or more expression vectors encoding a first antibody or antibody fragment as defined above. The expression vector(s) may be Sindbis virus or VEE vector(s). The vaccine may be formulated for delivery by needle injection, jet injection, or electroporation. The vaccine formulation may further comprise one or more expression vectors encoding for a second antibody or antibody fragment, such as a distinct antibody or antibody fragment of claims 26-34.
In still yet a further embodiment, there is provided a method of protecting the health of a placenta and/or fetus of a pregnant a subject infected with or at risk of infection with an alphavirus comprising delivering to said subject an antibody or antibody fragment having clone-paired heavy and light chain CDR sequences from Tables 3 and 4, respectively.
The antibody or antibody fragment may be encoded by clone-paired variable sequences as set forth in Table 1, may be encoded by light and heavy chain variable sequences having 70%, 80%, or 90% identity to clone-paired variable sequences as set forth in Table 1, or may be encoded by light and heavy chain variable sequences having 95% identity to clone-paired sequences as set forth in Table 1. The antibody or antibody fragment may comprise light and heavy chain variable sequences according to clone-paired sequences from Table 2, may comprise light and heavy chain variable sequences having 70%, 80% or 90% identity to clone-paired sequences from Table 2, or may comprise light and heavy chain variable sequences having 95% identity to clone-paired sequences from Table 2.
The antibody may be a chimeric antibody or a bispecific antibody, or wherein the antibody fragment is a recombinant scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, or Fv fragment. The antibody may be an IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody, or a recombinant IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody or IgG, IgA, IgM, polymeric IgA, or polymeric IgM antibody fragment comprising an Fc portion mutated to alter (eliminate or enhance) FcR interactions, to increase half-life and/or increase therapeutic efficacy, such as a LALA, N297, GASD/ALIE, YTE or
LS mutation or glycan modified to alter (eliminate or enhance) FcR interactions such as enzymatic or chemical addition or removal of glycans or expression in a cell line engineered with a defined glycosylating pattern. The antibody may be a chimeric antibody, or is bispecific antibody, or wherein said antibody or antibody fragment further comprises a cell penetrating peptide and/or is an intrabody.
The antibody or antibody fragment may be administered prior to infection or after infection. The subject may be a pregnant female, a sexually active female, or a female undergoing fertility treatments. Delivering may comprise antibody or antibody fragment administration, or genetic delivery with an RNA or DNA sequence or vector encoding the antibody or antibody fragment. The antibody or antibody fragment may increase the size of the placenta as compared to an untreated control. The antibody or antibody fragment may reduce viral load and/or pathology of the fetus as compared to an untreated control.
In an additional embodiment, there is provided a method of determining the antigenic integrity, correct conformation and/or correct sequence of an alphavirus antigen comprising (a) contacting a sample comprising said antigen with a first antibody or antibody fragment having clone-paired heavy and light chain CDR sequences from Tables 3 and 4, respectively; and (b) determining antigenic integrity, correct conformation and/or correct sequence of said antigen by detectable binding of said first antibody or antibody fragment to said antigen. The sample may comprise recombinantly produced antigen, or a vaccine formulation or vaccine production batch. Detection may comprise ELISA, RIA, western blot, a biosensor using surface plasmon resonance or biolayer interferometry, or flow cytometric staining.
The first antibody or antibody fragment may be encoded by clone-paired variable sequences as set forth in Table 1, may be encoded by light and heavy chain variable sequences having 70%, 80%, or 90% identity to clone-paired variable sequences as set forth in Table 1, or may be encoded by light and heavy chain variable sequences having 95% identity to clone-paired sequences as set forth in Table 1. The first antibody or antibody fragment may comprise light and heavy chain variable sequences according to clone-paired sequences from Table 2, may comprise light and heavy chain variable sequences having 70%, 80% or 90% identity to clone-paired sequences from Table 2, or may comprise light and heavy chain variable sequences having 95% identity to clone-paired sequences from Table 2. The first antibody fragment may be a recombinant scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, or Fv fragment. The method may further comprise performing steps (a) and (b) a second time to determine the antigenic stability of the antigen over time.
The method may further comprise (c) contacting a sample comprising said antigen with a second antibody or antibody fragment having clone-paired heavy and light chain CDR sequences from Tables 3 and 4, respectively; and (d) determining antigenic integrity of said antigen by detectable binding of said second antibody or antibody fragment to said antigen. The second antibody or antibody fragment may be encoded by clone-paired variable sequences as set forth in Table 1, may be encoded by light and heavy chain variable sequences having 70%, 80%, or 90% identity to clone-paired variable sequences as set forth in Table 1, or may be encoded by light and heavy chain variable sequences having 95% identity to clone-paired sequences as set forth in Table 1. The second antibody or antibody fragment may comprise light and heavy chain variable sequences according to clone-paired sequences from Table 2, may comprise light and heavy chain variable sequences having 70%, 80% or 90% identity to clone-paired sequences from Table 2, or may comprise light and heavy chain variable sequences having 95% identity to clone-paired sequences from Table 2. The second antibody fragment may be a recombinant scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, or Fv fragment. The method may further comprise performing steps (c) and (d) a second time to determine the antigenic stability of the antigen over time.
In an additional embodiment, there is provided a human monoclonal antibody or antibody fragment, or hybridoma or engineered cell producing the same, wherein said antibody binds to alphavirus glycoprotein E1 or E2 and (a) reacts with one, two or all three of EEEV, VEEV and WEEV; (b) reacts with at least one of EEEV, VEEV, and WEEV, and also reacts with an arthritogenic virus, such as CHIKV; (c) neutralizes alphavirus at pre-attachment or post-attachment; (d) recognizes a neutralizing antigenic site in domain B at the tip of EEEV E2 glycoprotein or a neutralizing antigenic site in domain A of EEEV E2 glycoprotein; and/or (e) is therapeutic for alphavirus infection and/or is prophylactic for alphavirus infection, wherein the antibody may be neutralizing and prophylactic/therapeutic, or may be neutralizing and therapeutic, or non-neutralizing and prophylactic.
The monoclonal antibody or antibody fragment may further comprise a domain that facilitates transfer across the blood brain barrier by binding to a transport molecule, thereby facilitating transport into the brain. The transport molecule may be transferrin receptor, heparin-binding EGF, a scavenger receptor AI or BI, EGF receptor, tumor necrosis factor, insulin or insulin-like growth factor receptor, apolipoprotein E receptor 2, leptin receptor, melanotransferrin receptor, or LDL receptor. The domain may be a peptide or an scFv (single chain fragment variable) antibody, Fab fragment, F(ab′)2 fragment, Fv fragment, single domain antibody (nanobody) or wherein said domain is a distinct binding specificity as part of a chimeric or bispecific antibody structure. They may further comprise a domain that facilitates transfer across a mucosal surface, such as the respiratory tract barrier, by binding to a transport molecule, thereby facilitating transport across the mucosal surface.
The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The word “about” means plus or minus 5% of the stated number.
It is contemplated that any method or composition described herein can be implemented with respect to any other method or composition described herein. Other objects, features and advantages of the present disclosure will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description.
The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present disclosure. The disclosure may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.
As discussed above, there remains a need to better understand the protective immune response against alphaviruses. The objective of this the work described here was to address how human mAbs neutralize and interact with the encephalitic alphaviruses, with primary focus on EEEV. The inventors isolated human mAbs to Eastern equine encephalitis virus (EEEV), Venezuelan equine encephalitis virus (VEEV), and Western equine encephalitis virus (WEEV). The initial focus was on EEEV as the inventors isolated a large panel of human monoclonal antibodies (mAbs) from a naturally infected EEEV survivor. From this panel, they have elucidated the reactivity, breadth, basis of neutralization, and prophylactic and therapeutic capabilities of the human antibody repertoire towards EEEV. In addition, they made progress in the isolation and characterization of human mAbs against EEEV, VEEV, and WEEV with a primary focus on the cross-reactivity and potential cross-neutralization of these mAbs from donors vaccinated with all three viruses (Special Immunizations Program—SIP) or VEEV alone. These mAbs in particular helped in the identification of conserved targets of antibody recognition and neutralization towards the encephalitic alphaviruses.
From the first human EEEV mAb panel, the inventors identified the diversity of human mAb reactivity and breadth to EEEV and other clinically relevant alphaviruses: VEEV, WEEV and CHIKV. The inventors elucidated the basis of neutralization and identified an extremely potent neutralizing human mAb towards BSL-2 SINV/EEEV and BSL-3 EEEV. They found this mAb to exhibit prophylactic and therapeutic activity in a stringent aerosol challenge in vivo small animal model. Through epitope mapping, they determined the diverse epitopes and the distinct neutralizing antigenic determinants recognized by human mAbs on EEEV.
Additionally, the inventors have begun to isolate human mAbs against EEEV, VEEV, and WEEV from SIP donors or those vaccinated with VEEV alone. Characterization of these mAbs will aim to determine the cross-reactive and potential cross-neutralization capabilities of human mAbs and identify potential correlates of protection against the encephalitic alphaviruses.
These and other aspects of the disclosure are described in detail below.
Alphavirus belongs to group IV of the Baltimore classification of the Togaviridae family of viruses, according to the system of classification based on viral genome composition introduced by David Baltimore in 1971. Alphaviruses, like all other group IV viruses, have a positive sense, single-stranded RNA genome. There are thirty alphaviruses able to infect various vertebrates such as humans, rodents, fish, birds, and larger mammals such as horses as well as invertebrates. Transmission between species and individuals occurs mainly via mosquitoes, making the alphaviruses a member of the collection of arboviruses—or arthropod-borne viruses. Alphavirus particles are enveloped, have a 70 nm diameter, tend to be spherical (although slightly pleomorphic), and have a 40 nm isometric nucleocapsid.
The alphaviruses are small, spherical, enveloped viruses with a genome of a single positive sense strand RNA. The total genome length ranges between 11,000 and 12,000 nucleotides, and has a 5′ cap, and 3′ poly-A tail. The four non-structural protein genes are encoded in the 5′ two-thirds of the genome, while the three structural proteins are translated from a subgenomic mRNA colinear with the 3′ one-third of the genome.
There are two open reading frames (ORF's) in the genome, non-structural and structural. The first is non-structural and encodes proteins (nsP1-nsP4) necessary for transcription and replication of viral RNA. The second encodes three structural proteins: the core nucleocapsid protein C, and the envelope proteins P62 and E1 that associate as a heterodimer. The viral membrane-anchored surface glycoproteins are responsible for receptor recognition and entry into target cells through membrane fusion.
The proteolytic maturation of P62 into E2 and E3 causes a change in the viral surface. Together the E1, E2, and sometimes E3, glycoprotein “spikes” form an E1/E2 dimer or an E1/E2/E3 trimer, where E2 extends from the centre to the vertices, E1 fills the space between the vertices, and E3, if present, is at the distal end of the spike. Upon exposure of the virus to the acidity of the endosome, E1 dissociates from E2 to form an E1 homotrimer, which is necessary for the fusion step to drive the cellular and viral membranes together. The alphaviral glycoprotein E1 is a class II viral fusion protein, which is structurally different from the class I fusion proteins found in influenza virus and HIV. The structure of the Semliki Forest virus revealed a structure that is similar to that of flaviviral glycoprotein E, with three structural domains in the same primary sequence arrangement. The E2 glycoprotein functions to interact with the nucleocapsid through its cytoplasmic domain, while its ectodomain is responsible for binding a cellular receptor. Most alphaviruses lose the peripheral protein E3, but in Semliki viruses it remains associated with the viral surface.
Four nonstructural proteins (nsP1-4) which are produced as a single polyprotein constitute the virus' replication machinery. The processing of the polyprotein occurs in a highly regulated manner, with cleavage at the P2/3 junction influencing RNA template use during genome replication. This site is located at the base of a narrow cleft and is not readily accessible. Once cleaved nsP3 creates a ring structure that encircles nsP2. These two proteins have an extensive interface.
Mutations in nsP2 that produce noncytopathic viruses or a temperature sensitive phenotypes cluster at the P2/P3 interface region. P3 mutations opposite the location of the nsP2 noncytopathic mutations prevent efficient cleavage of P2/3. This in turn affects RNA infectivity altering viral RNA production levels.
The virus has a 60-70 nanometer diameter. It is enveloped, spherical and has a positive-strand RNA genome of ˜12 kilobases. The genome encodes two polyproteins. The first polyprotein consists of four non-structural units: in order from the N terminal to the C terminal—nsP1, nsP2, nsP3, and nsP4. The second is a structural polyprotein composed of five expression units: from the N terminal to the C terminal—Capsid, E3, E2, 6K and E1. A sub genomic positive strand RNA—the 26S RNA—is replicated from a negative-stranded RNA intermediate. This serves as template for the synthesis of viral structural proteins. Most alphaviruses have conserved domains involved in regulation of viral RNA synthesis.
The nucleocapsid, 40 nanometers in diameter, contains 240 copies of the capsid protein and has a T=4 icosahedral symmetry. The E1 and E2 viral glycoproteins are embedded in the lipid bilayer. Single E1 and E2 molecules associate to form heterodimers. The E1-E2 heterodimers form one-to-one contacts between the E2 protein and the nucleocapsid monomers. The E1 and E2 proteins mediate contact between the virus and the host cell.
Several receptors have been identified. These include prohibitin, phosphatidylserine, glycosaminoglycans and ATP synthase 13 subunit.
Replication occurs within the cytoplasm and virions mature by budding through the plasma membrane, where virus-encoded surface glycoproteins E2 and E1 are assimilated. These two glycoproteins are the targets of numerous serologic reactions and tests including neutralization and hemagglutination inhibition. The alphaviruses show various degrees of antigenic cross-reactivity in these reactions and this forms the basis for the seven antigenic complexes, 30 species and many subtypes and varieties. The E2 protein is the site of most neutralizing epitopes, while the E1 protein contains more conserved, cross-reactive epitopes.
There are many alphaviruses distributed around the world with the ability to cause human disease. Infectious arthritis, encephalitis, rashes and fever are the most commonly observed symptoms. Larger mammals such as humans and horses are usually dead-end hosts or play a minor role in viral transmission; however, in the case of Venezuelan equine encephalitis the virus is mainly amplified in horses. In most other cases the virus is maintained in nature in mosquitoes, rodents and birds.
Alphavirus infections are spread by insect vectors such as mosquitoes. Once a human is bitten by the infected mosquito, the virus can gain entry into the bloodstream, causing viremia. The alphavirus can also get into the CNS where it is able to grow and multiply within the neurones. This can lead to encephalitis, which can be fatal.
When an individual is infected with this particular virus, its immune system can play a role in clearing away the virus particles. Alphaviruses are able to cause the production of interferons. Antibodies and T cells are also involved. The neutralizing antibodies also play an important role to prevent further infection and spread.
Diagnoses is based on clinical samples from which the virus can be easily isolated and identified. There are no alphavirus vaccines currently available. Vector control with repellents, protective clothing, breeding site destruction, and spraying are the preventive measures of choice.
An “isolated antibody” is one that has been separated and/or recovered from a component of its natural environment. Contaminant components of its natural environment are materials that would interfere with diagnostic or therapeutic uses for the antibody, and may include enzymes, hormones, and other proteinaceous or non-proteinaceous solutes. In particular embodiments, the antibody is purified: (1) to greater than 95% by weight of antibody as determined by the Lowry method, and most particularly more than 99% by weight; (2) to a degree sufficient to obtain at least 15 residues of N-terminal or internal amino acid sequence by use of a spinning cup sequenator; or (3) to homogeneity by SDS-PAGE under reducing or non-reducing conditions using Coomassie blue or silver stain. Isolated antibody includes the antibody in situ within recombinant cells since at least one component of the antibody's natural environment will not be present. Ordinarily, however, isolated antibody will be prepared by at least one purification step.
The basic four-chain antibody unit is a heterotetrameric glycoprotein composed of two identical light (L) chains and two identical heavy (H) chains. An IgM antibody consists of 5 basic heterotetramer units along with an additional polypeptide called J chain, and therefore contain 10 antigen binding sites, while secreted IgA antibodies can polymerize to form polyvalent assemblages comprising 2-5 of the basic 4-chain units along with J chain. In the case of IgGs, the 4-chain unit is generally about 150,000 daltons. Each L chain is linked to an H chain by one covalent disulfide bond, while the two H chains are linked to each other by one or more disulfide bonds depending on the H chain isotype. Each H and L chain also has regularly spaced intrachain disulfide bridges. Each H chain has at the N-terminus, a variable region (VH) followed by three constant domains (CH) for each of the alpha and gamma chains and four CH domains for mu and isotypes. Each L chain has at the N-terminus, a variable region (VL) followed by a constant domain (CL) at its other end. The VL is aligned with the VH and the CL is aligned with the first constant domain of the heavy chain (CH1). Particular amino acid residues are believed to form an interface between the light chain and heavy chain variable regions. The pairing of a VH and VL together forms a single antigen-binding site. For the structure and properties of the different classes of antibodies, see, e.g., Basic and Clinical Immunology, 8th edition, Daniel P. Stites, Abba I. Terr and Tristram G. Parslow (eds.), Appleton & Lange, Norwalk, Conn., 1994, page 71, and Chapter 6.
The L chain from any vertebrate species can be assigned to one of two clearly distinct types, called kappa and lambda based on the amino acid sequences of their constant domains (CL). Depending on the amino acid sequence of the constant domain of their heavy chains (CH), immunoglobulins can be assigned to different classes or isotypes. There are five classes of immunoglobulins: IgA, IgD, IgE, IgG, and IgM, having heavy chains designated alpha, delta, epsilon, gamma and mu, respectively. They gamma and alpha classes are further divided into subclasses on the basis of relatively minor differences in CH sequence and function, humans express the following subclasses: IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2.
The term “variable” refers to the fact that certain segments of the V domains differ extensively in sequence among antibodies. The V domain mediates antigen binding and defines specificity of a particular antibody for its particular antigen. However, the variability is not evenly distributed across the 110-amino acid span of the variable regions. Instead, the V regions consist of relatively invariant stretches called framework regions (FRs) of 15-30 amino acids separated by shorter regions of extreme variability called “hypervariable regions” that are each 9-12 amino acids long. The variable regions of native heavy and light chains each comprise four FRs, largely adopting a beta-sheet configuration, connected by three hypervariable regions, which form loops connecting, and in some cases forming part of, the beta-sheet structure. The hypervariable regions in each chain are held together in close proximity by the FRs and, with the hypervariable regions from the other chain, contribute to the formation of the antigen-binding site of antibodies (see Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991)). The constant domains are not involved directly in binding an antibody to an antigen, but exhibit various effector functions, such as participation of the antibody in antibody dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), antibody-dependent neutrophil phagocytosis (ADNP), and antibody-dependent complement deposition (ADCD).
The term “hypervariable region” when used herein refers to the amino acid residues of an antibody that are responsible for antigen binding. The hypervariable region generally comprises amino acid residues from a “complementarity determining region” or “CDR” (e.g., around about residues 24-34 (L1), 50-56 (L2) and 89-97 (L3) in the VL, and around about 31-35 (H1), 50-65 (H2) and 95-102 (H3) in the VH when numbered in accordance with the Kabat numbering system; Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991)); and/or those residues from a “hypervariable loop” (e.g., residues 24-34 (L1), 50-56 (L2) and 89-97 (L3) in the VL, and 26-32 (H1), 52-56 (H2) and 95-101 (H3) in the VH when numbered in accordance with the Chothia numbering system; Chothia and Lesk, J. Mol. Biol. 196:901-917 (1987)); and/or those residues from a “hypervariable loop”/CDR (e.g., residues 27-38 (L1), 56-65 (L2) and 105-120 (L3) in the VL, and 27-38 (H1), 56-65 (H2) and 105-120 (H3) in the VH when numbered in accordance with the IMGT numbering system; Lefranc, M. P. et al. Nucl. Acids Res. 27:209-212 (1999), Ruiz, M. et al. Nucl. Acids Res. 28:219-221 (2000)). Optionally the antibody has symmetrical insertions at one or more of the following points 28, 36 (L1), 63, 74-75 (L2) and 123 (L3) in the VL, and 28, 36 (H1), 63, 74-75 (H2) and 123 (H3) in the VsubH when numbered in accordance with AHo; Honneger, A. and Plunkthun, A. J. Mol. Biol. 309:657-670 (2001)).
By “germline nucleic acid residue” is meant the nucleic acid residue that naturally occurs in a germline gene encoding a constant or variable region. “Germline gene” is the DNA found in a germ cell (i.e., a cell destined to become an egg or in the sperm). A “germline mutation” refers to a heritable change in a particular DNA that has occurred in a germ cell or the zygote at the single-cell stage, and when transmitted to offspring, such a mutation is incorporated in every cell of the body. A germline mutation is in contrast to a somatic mutation which is acquired in a single body cell. In some cases, nucleotides in a germline DNA sequence encoding for a variable region are mutated (i.e., a somatic mutation) and replaced with a different nucleotide.
The term “monoclonal antibody” as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic site. Furthermore, in contrast to polyclonal antibody preparations that include different antibodies directed against different determinants (epitopes), each monoclonal antibody is directed against a single determinant on the antigen. In addition to their specificity, the monoclonal antibodies are advantageous in that they may be synthesized uncontaminated by other antibodies. The modifier “monoclonal” is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies useful in the present disclosure may be prepared by the hybridoma methodology first described by Kohler et al., Nature, 256:495 (1975), or may be made using recombinant DNA methods in bacterial, eukaryotic animal or plant cells (see, e.g., U.S. Pat. No. 4,816,567) after single cell sorting of an antigen specific B cell, an antigen specific plasmablast responding to an infection or immunization, or capture of linked heavy and light chains from single cells in a bulk sorted antigen specific collection. The “monoclonal antibodies” may also be isolated from phage antibody libraries using the techniques described in Clackson et al., Nature, 352:624-628 (1991) and Marks et al., J. Mol. Biol., 222:581-597 (1991), for example.
A. General Methods
It will be understood that monoclonal antibodies binding to alpahvirus will have several applications. These include the production of diagnostic kits for use in detecting and diagnosing alphavirus infection, as well as for treating the same. In these contexts, one may link such antibodies to diagnostic or therapeutic agents, use them as capture agents or competitors in competitive assays, or use them individually without additional agents being attached thereto. The antibodies may be mutated or modified, as discussed further below. Methods for preparing and characterizing antibodies are well known in the art (see, e.g., Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory, 1988; U.S. Pat. No. 4,196,265).
The methods for generating monoclonal antibodies (MAbs) generally begin along the same lines as those for preparing polyclonal antibodies. The first step for both these methods is immunization of an appropriate host or identification of subjects who are immune due to prior natural infection or vaccination with a licensed or experimental vaccine. As is well known in the art, a given composition for immunization may vary in its immunogenicity. It is often necessary therefore to boost the host immune system, as may be achieved by coupling a peptide or polypeptide immunogen to a carrier. Exemplary and preferred carriers are keyhole limpet hemocyanin (KLH) and bovine serum albumin (BSA). Other albumins such as ovalbumin, mouse serum albumin or rabbit serum albumin can also be used as carriers. Means for conjugating a polypeptide to a carrier protein are well known in the art and include glutaraldehyde, m-maleimidobencoyl-N-hydroxysuccinimide ester, carbodiimyde and bis-biazotized benzidine. As also is well known in the art, the immunogenicity of a particular immunogen composition can be enhanced by the use of non-specific stimulators of the immune response, known as adjuvants. Exemplary and preferred adjuvants in animals include complete Freund's adjuvant (a non-specific stimulator of the immune response containing killed Mycobacterium tuberculosis), incomplete Freund's adjuvants and aluminum hydroxide adjuvant and in humans include alum, CpG, MFP59 and combinations of immunostimulatory molecules (“Adjuvant Systems”, such as AS01 or AS03). Additional experimental forms of inoculation to induce alphavirus-specific B cells is possible, including nanoparticle vaccines, or gene-encoded antigens delivered as DNA or RNA genes in a physical delivery system (such as lipid nanoparticle or on a gold biolistic bead), and delivered with needle, gene gun, transcutaneous electroporation device. The antigen gene also can be carried as encoded by a replication competent or defective viral vector such as adenovirus, adeno-associated virus, poxvirus, herpesvirus, or alphavirus replicon, or alternatively a virus like particle.
In the case of human antibodies against natural pathogens, a suitable approach is to identify subjects that have been exposed to the pathogens, such as those who have been diagnosed as having contracted the disease, or those who have been vaccinated to generate protective immunity against the pathogen or to test the safety or efficacy of an experimental vaccine. Circulating anti-pathogen antibodies can be detected, and antibody encoding or producing B cells from the antibody-positive subject may then be obtained.
The amount of immunogen composition used in the production of polyclonal antibodies varies upon the nature of the immunogen as well as the animal used for immunization. A variety of routes can be used to administer the immunogen (subcutaneous, intramuscular, intradermal, intravenous and intraperitoneal). The production of polyclonal antibodies may be monitored by sampling blood of the immunized animal at various points following immunization. A second, booster injection, also may be given. The process of boosting and titering is repeated until a suitable titer is achieved. When a desired level of immunogenicity is obtained, the immunized animal can be bled and the serum isolated and stored, and/or the animal can be used to generate MAbs.
Following immunization, somatic cells with the potential for producing antibodies, specifically B lymphocytes (B cells), are selected for use in the MAb generating protocol. These cells may be obtained from biopsied spleens, lymph nodes, tonsils or adenoids, bone marrow aspirates or biopsies, tissue biopsies from mucosal organs like lung or GI tract, or from circulating blood. The antibody-producing B lymphocytes from the immunized animal or immune human are then fused with cells of an immortal myeloma cell, generally one of the same species as the animal that was immunized or human or human/mouse chimeric cells. Myeloma cell lines suited for use in hybridoma-producing fusion procedures preferably are non-antibody-producing, have high fusion efficiency, and enzyme deficiencies that render then incapable of growing in certain selective media which support the growth of only the desired fused cells (hybridomas). Any one of a number of myeloma cells may be used, as are known to those of skill in the art (Goding, pp. 65-66, 1986; Campbell, pp. 75-83, 1984). HMMA2.5 cells or MFP-2 cells are particularly useful examples of such cells.
Methods for generating hybrids of antibody-producing spleen or lymph node cells and myeloma cells usually comprise mixing somatic cells with myeloma cells in a 2:1 proportion, though the proportion may vary from about 20:1 to about 1:1, respectively, in the presence of an agent or agents (chemical or electrical) that promote the fusion of cell membranes. In some cases, transformation of human B cells with Epstein Barr virus (EBV) as an initial step increases the size of the B cells, enhancing fusion with the relatively large-sized myeloma cells. Transformation efficiency by EBV is enhanced by using CpG and a Chk2 inhibitor drug in the transforming medium. Alternatively, human B cells can be activated by co-culture with transfected cell lines expressing CD40 Ligand (CD154) in medium containing additional soluble factors, such as IL-21 and human B cell Activating Factor (BAFF), a Type II member of the TNF superfamily Fusion methods using Sendai virus have been described by Kohler and Milstein (1975; 1976), and those using polyethylene glycol (PEG), such as 37% (v/v) PEG, by Gefter et al. (1977). The use of electrically induced fusion methods also is appropriate (Goding, pp. 71-74, 1986) and there are processes for better efficiency (Yu et al., 2008). Fusion procedures usually produce viable hybrids at low frequencies, about 1×10−6 to 1×10−8, but with optimized procedures one can achieve fusion efficiencies close to 1 in 200 (Yu et al., 2008). However, relatively low efficiency of fusion does not pose a problem, as the viable, fused hybrids are differentiated from the parental, infused cells (particularly the infused myeloma cells that would normally continue to divide indefinitely) by culturing in a selective medium. The selective medium is generally one that contains an agent that blocks the de novo synthesis of nucleotides in the tissue culture medium. Exemplary and preferred agents are aminopterin, methotrexate, and azaserine. Aminopterin and methotrexate block de novo synthesis of both purines and pyrimidines, whereas azaserine blocks only purine synthesis. Where aminopterin or methotrexate is used, the medium is supplemented with hypoxanthine and thymidine as a source of nucleotides (HAT medium). Where azaserine is used, the medium is supplemented with hypoxanthine. Ouabain is added if the B cell source is an EBV-transformed human B cell line, in order to eliminate EBV-transformed lines that have not fused to the myeloma.
The preferred selection medium is HAT or HAT with ouabain. Only cells capable of operating nucleotide salvage pathways are able to survive in HAT medium. The myeloma cells are defective in key enzymes of the salvage pathway, e.g., hypoxanthine phosphoribosyl transferase (HPRT), and they cannot survive. The B cells can operate this pathway, but they have a limited life span in culture and generally die within about two weeks. Therefore, the only cells that can survive in the selective media are those hybrids formed from myeloma and B cells. When the source of B cells used for fusion is a line of EBV-transformed B cells, as here, ouabain may also be used for drug selection of hybrids as EBV-transformed B cells are susceptible to drug killing, whereas the myeloma partner used is chosen to be ouabain resistant.
Culturing provides a population of hybridomas from which specific hybridomas are selected. Typically, selection of hybridomas is performed by culturing the cells by single-clone dilution in microtiter plates, followed by testing the individual clonal supernatants (after about two to three weeks) for the desired reactivity. The assay should be sensitive, simple and rapid, such as radioimmunoassays, enzyme immunoassays, cytotoxicity assays, plaque assays dot immunobinding assays, and the like. The selected hybridomas are then serially diluted or single-cell sorted by flow cytometric sorting and cloned into individual antibody-producing cell lines, which clones can then be propagated indefinitely to provide mAbs. The cell lines may be exploited for MAb production in two basic ways. A sample of the hybridoma can be injected (often into the peritoneal cavity) into an animal (e.g., a mouse). Optionally, the animals are primed with a hydrocarbon, especially oils such as pristane (tetramethylpentadecane) prior to injection. When human hybridomas are used in this way, it is optimal to inject immunocompromised mice, such as SCID mice, to prevent tumor rejection. The injected animal develops tumors secreting the specific monoclonal antibody produced by the fused cell hybrid. The body fluids of the animal, such as serum or ascites fluid, can then be tapped to provide MAbs in high concentration. The individual cell lines could also be cultured in vitro, where the MAbs are naturally secreted into the culture medium from which they can be readily obtained in high concentrations. Alternatively, human hybridoma cells lines can be used in vitro to produce immunoglobulins in cell supernatant. The cell lines can be adapted for growth in serum-free medium to optimize the ability to recover human monoclonal immunoglobulins of high purity.
MAbs produced by either means may be further purified, if desired, using filtration, centrifugation and various chromatographic methods such as FPLC or affinity chromatography. Fragments of the monoclonal antibodies of the disclosure can be obtained from the purified monoclonal antibodies by methods which include digestion with enzymes, such as pepsin or papain, and/or by cleavage of disulfide bonds by chemical reduction. Alternatively, monoclonal antibody fragments encompassed by the present disclosure can be synthesized using an automated peptide synthesizer.
It also is contemplated that a molecular cloning approach may be used to generate monoclonal antibodies. Single B cells labelled with the antigen of interest can be sorted physically using paramagnetic bead selection or flow cytometric sorting, then RNA can be isolated from the single cells and antibody genes amplified by RT-PCR. Alternatively, antigen-specific bulk sorted populations of cells can be segregated into microvesicles and the matched heavy and light chain variable genes recovered from single cells using physical linkage of heavy and light chain amplicons, or common barcoding of heavy and light chain genes from a vesicle. Matched heavy and light chain genes form single cells also can be obtained from populations of antigen specific B cells by treating cells with cell-penetrating nanoparticles bearing RT-PCR primers and barcodes for marking transcripts with one barcode per cell. The antibody variable genes also can be isolated by RNA extraction of a hybridoma line and the antibody genes obtained by RT-PCR and cloned into an immunoglobulin expression vector. Alternatively, combinatorial immunoglobulin phagemid libraries are prepared from RNA isolated from the cell lines and phagemids expressing appropriate antibodies are selected by panning using viral antigens. The advantages of this approach over conventional hybridoma techniques are that approximately 104 times as many antibodies can be produced and screened in a single round, and that new specificities are generated by H and L chain combination which further increases the chance of finding appropriate antibodies.
Other U.S. patents, each incorporated herein by reference, that teach the production of antibodies useful in the present disclosure include U.S. Pat. No. 5,565,332, which describes the production of chimeric antibodies using a combinatorial approach; U.S. Pat. No. 4,816,567 which describes recombinant immunoglobulin preparations; and U.S. Pat. No. 4,867,973 which describes antibody-therapeutic agent conjugates.
B. Antibodies of the Present Disclosure
Antibodies according to the present disclosure may be defined, in the first instance, by their binding specificity. Those of skill in the art, by assessing the binding specificity/affinity of a given antibody using techniques well known to those of skill in the art, can determine whether such antibodies fall within the scope of the instant claims. For example, the epitope to which a given antibody bind may consist of a single contiguous sequence of 3 or more (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0, 18, 19, 20) amino acids located within the antigen molecule (e.g., a linear epitope in a domain). Alternatively, the epitope may consist of a plurality of non-contiguous amino acids (or amino acid sequences) located within the antigen molecule (e.g., a conformational epitope).
Various techniques known to persons of ordinary skill in the art can be used to determine whether an antibody “interacts with one or more amino acids” within a polypeptide or protein. Exemplary techniques include, for example, routine cross-blocking assays, such as that described in Antibodies, Harlow and Lane (Cold Spring Harbor Press, Cold Spring Harbor, N.Y.). Cross-blocking can be measured in various binding assays such as ELISA, biolayer interferometry, or surface plasmon resonance. Other methods include alanine scanning mutational analysis, peptide blot analysis (Reineke, Methods Mol. Biol. 248: 443-63, 2004), peptide cleavage analysis, high-resolution electron microscopy techniques using single particle reconstruction, cryoEM, or tomography, crystallographic studies and NMR analysis. In addition, methods such as epitope excision, epitope extraction and chemical modification of antigens can be employed (Tomer, Prot. Sci. 9: 487-496, 2000). Another method that can be used to identify the amino acids within a polypeptide with which an antibody interacts is hydrogen/deuterium exchange detected by mass spectrometry. In general terms, the hydrogen/deuterium exchange method involves deuterium-labeling the protein of interest, followed by binding the antibody to the deuterium-labeled protein. Next, the protein/antibody complex is transferred to water and exchangeable protons within amino acids that are protected by the antibody complex undergo deuterium-to-hydrogen back-exchange at a slower rate than exchangeable protons within amino acids that are not part of the interface. As a result, amino acids that form part of the protein/antibody interface may retain deuterium and therefore exhibit relatively higher mass compared to amino acids not included in the interface. After dissociation of the antibody, the target protein is subjected to protease cleavage and mass spectrometry analysis, thereby revealing the deuterium-labeled residues which correspond to the specific amino acids with which the antibody interacts. See, e.g., Ehring (1999) Analytical Biochemistry 267: 252-259; Engen and Smith (2001) Anal. Chem. 73: 256A-265A. When the antibody neutralizes alphavirus, antibody escape mutant variant organisms can be isolated by propagating alphavirus in vitro or in animal models in the presence of high concentrations of the antibody. Sequence analysis of the alphavirus gene encoding the antigen targeted by the antibody, such as glycoprotein E1 or E2, reveals the mutation(s) conferring antibody escape, indicating residues in the epitope or that affect the structure of the epitope allosterically.
The term “epitope” refers to a site on an antigen to which B and/or T cells respond. B-cell epitopes can be formed both from contiguous amino acids or noncontiguous amino acids juxtaposed by tertiary folding of a protein. Epitopes formed from contiguous amino acids are typically retained on exposure to denaturing solvents, whereas epitopes formed by tertiary folding are typically lost on treatment with denaturing solvents. An epitope typically includes at least 3, and more usually, at least 5 or 8-10 amino acids in a unique spatial conformation.
Modification-Assisted Profiling (MAP), also known as Antigen Structure-based Antibody Profiling (ASAP) is a method that categorizes large numbers of monoclonal antibodies (mAbs) directed against the same antigen according to the similarities of the binding profile of each antibody to chemically or enzymatically modified antigen surfaces (see US 2004/0101920, herein specifically incorporated by reference in its entirety). Each category may reflect a unique epitope either distinctly different from or partially overlapping with epitope represented by another category. This technology allows rapid filtering of genetically identical antibodies, such that characterization can be focused on genetically distinct antibodies. When applied to hybridoma screening, MAP may facilitate identification of rare hybridoma clones that produce mAbs having the desired characteristics. MAP may be used to sort the antibodies of the disclosure into groups of antibodies binding different epitopes.
The present disclosure includes antibodies that may hind to the same epitope, or a portion of the epitope. Likewise, the present disclosure also includes antibodies that compete for binding to a target or a fragment thereof with any of the specific exemplary antibodies described herein. One can easily determine whether an antibody binds to the same epi tope as, or competes for binding with, a reference antibody by using routine methods known in the art. For example, to determine if a test antibody binds to the same epitope as a reference, the reference antibody is allowed to bind to target under saturating conditions. Next, the ability of a test antibody to bind to the target molecule is assessed. If the test antibody is able to bind to the target molecule following saturation binding with the reference antibody, it can be concluded that the test antibody binds to a different epitope than the reference antibody. On the other hand, if the test antibody is not able to bind to the target molecule following saturation binding with the reference antibody, then the test antibody may bind to the same epitope as the epitope bound by the reference antibody.
To determine if an antibody competes for binding with a reference anti-alphavirus antibody, the above-described binding methodology is performed in two orientations: In a first orientation, the reference antibody is allowed to bind to the alphavirus antigen under saturating conditions followed by assessment of binding of the test antibody to the alphavirus antigen. In a second orientation, the test antibody is allowed to bind to the alphavirus antigen under saturating conditions followed by assessment of binding of the reference antibody to the alphavirus antigen. If, in both orientations, only the first (saturating) antibody is capable of binding to the alphavirus, then it is concluded that the test antibody and the reference antibody compete for binding to the alphavirus. As will be appreciated by a person of ordinary skill in the art, an antibody that competes for binding with a reference antibody may not necessarily bind to the identical epitope as the reference antibody but may sterically block binding of the reference antibody by binding an overlapping or adjacent epitope.
Two antibodies bind to the same or overlapping epitope if each competitively inhibits (blocks) binding of the other to the antigen. That is, a 1-, 5-, 10-, 20- or 100-fold excess of one antibody inhibits binding of the other by at least 50% but preferably 75%, 90% or even 99% as measured in a competitive binding assay (see, e.g., Junghans et al., Cancer Res. 1990 50:1495-1502). Alternatively, two antibodies have the same epitope if essentially all amino acid mutations in the antigen that reduce or eliminate binding of one antibody reduce or eliminate binding of the other. Two antibodies have overlapping epitopes if some amino acid mutations that reduce or eliminate binding of one antibody reduce or eliminate binding of the other.
Additional routine experimentation (e.g., peptide mutation and binding analyses) can then be carried out to confirm whether the observed lack of binding of the test antibody is in fact due to binding to the same epi tope as the reference antibody or if steric blocking (or another phenomenon) is responsible for the lack of observed binding. Experiments of this sort can be performed using ELISA, RIA, surface plasmon resonance, flow cytometry or any other quantitative or qualitative antibody-binding assay available in the art. Structural studies with EM or crystallography also can demonstrate whether or not two antibodies that compete for binding recognize the same epitope.
In another aspect, there are provided monoclonal antibodies having clone-paired CDRs from the heavy and light chains as illustrated in Tables 3 and 4, respectively. Such antibodies may be produced by the clones discussed below in the Examples section using methods described herein.
In another aspect, the antibodies may be defined by their variable sequence, which include additional “framework” regions. These are provided in Tables 1 and 2 that encode or represent full variable regions. Furthermore, the antibodies sequences may vary from these sequences, optionally using methods discussed in greater detail below. For example, nucleic acid sequences may vary from those set out above in that (a) the variable regions may be segregated away from the constant domains of the light and heavy chains, (b) the nucleic acids may vary from those set out above while not affecting the residues encoded thereby, (c) the nucleic acids may vary from those set out above by a given percentage, e.g., 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% homology, (d) the nucleic acids may vary from those set out above by virtue of the ability to hybridize under high stringency conditions, as exemplified by low salt and/or high temperature conditions, such as provided by about 0.02 M to about 0.15 M NaCl at temperatures of about 50° C. to about 70° C., (e) the amino acids may vary from those set out above by a given percentage, e.g., 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% homology, or (1) the amino acids may vary from those set out above by permitting conservative substitutions (discussed below). Each of the foregoing applies to the nucleic acid sequences set forth as Table 1 and the amino acid sequences of Table 2.
When comparing polynucleotide and polypeptide sequences, two sequences are said to be “identical” if the sequence of nucleotides or amino acids in the two sequences is the same when aligned for maximum correspondence, as described below. Comparisons between two sequences are typically performed by comparing the sequences over a comparison window to identify and compare local regions of sequence similarity. A “comparison window” as used herein, refers to a segment of at least about 20 contiguous positions, usually 30 to about 75, 40 to about 50, in which a sequence may be compared to a reference sequence of the same number of contiguous positions after the two sequences are optimally aligned.
Optimal alignment of sequences for comparison may be conducted using the Megalign program in the Lasergene suite of bioinformatics software (DNASTAR, Inc., Madison, Wis.), using default parameters. This program embodies several alignment schemes described in the following references: Dayhoff, M. O. (1978) A model of evolutionary change in proteins—Matrices for detecting distant relationships. In Dayhoff, M. O. (ed.) Atlas of Protein Sequence and Structure, National Biomedical Research Foundation, Washington D.C. Vol. 5, Suppl. 3, pp. 345-358; Hein J. (1990) Unified Approach to Alignment and Phylogeny pp. 626-645 Methods in Enzymology vol. 183, Academic Press, Inc., San Diego, Calif.; Higgins, D. G. and Sharp, P. M. (1989) CABIOS 5:151-153; Myers, E. W. and Muller W. (1988) CABIOS 4:11-17; Robinson, E. D. (1971) Comb. Theor 11:105; Santou, N. Nes, M. (1987) Mol. Biol. Evol. 4:406-425; Sneath, P. H. A. and Sokal, R. R. (1973) Numerical Taxonomy—the Principles and Practice of Numerical Taxonomy, Freeman Press, San Francisco, Calif.; Wilbur, W. J. and Lipman, D. J. (1983) Proc. Natl. Acad., Sci. USA 80:726-730.
Alternatively, optimal alignment of sequences for comparison may be conducted by the local identity algorithm of Smith and Waterman (1981) Add. APL. Math 2:482, by the identity alignment algorithm of Needleman and Wunsch (1970) J. Mol. Biol. 48:443, by the search for similarity methods of Pearson and Lipman (1988) Proc. Natl. Acad. Sci. USA 85: 2444, by computerized implementations of these algorithms (GAP, BESTFIT, BLAST, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group (GCG), 575 Science Dr., Madison, Wis.), or by inspection.
One particular example of algorithms that are suitable for determining percent sequence identity and sequence similarity are the BLAST and BLAST 2.0 algorithms, which are described in Altschul et al. (1977) Nucl. Acids Res. 25:3389-3402 and Altschul et al. (1990) J. Mol. Biol. 215:403-410, respectively. BLAST and BLAST 2.0 can be used, for example with the parameters described herein, to determine percent sequence identity for the polynucleotides and polypeptides of the disclosure. Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information. The rearranged nature of an antibody sequence and the variable length of each gene requires multiple rounds of BLAST searches for a single antibody sequence. Also, manual assembly of different genes is difficult and error-prone. The sequence analysis tool IgBLAST (world-wide-web at ncbi.nlm.nih.gov/igblast/) identifies matches to the germline V, D and J genes, details at rearrangement junctions, the delineation of Ig V domain framework regions and complementarity determining regions. IgBLAST can analyze nucleotide or protein sequences and can process sequences in batches and allows searches against the germline gene databases and other sequence databases simultaneously to minimize the chance of missing possibly the best matching germline V gene.
In one illustrative example, cumulative scores can be calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always >0) and N (penalty score for mismatching residues; always <0). Extension of the word hits in each direction are halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below, due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. The BLAST algorithm parameters W, T and X determine the sensitivity and speed of the alignment. The BLASTN program (for nucleotide sequences) uses as defaults a wordlength (W) of 11, and expectation (E) of 10, and the BLOSUM62 scoring matrix (see Henikoff and Henikoff (1989) Proc. Natl. Acad. Sci. USA 89:10915) alignments, (B) of 50, expectation (E) of 10, M=5, N=−4 and a comparison of both strands.
For amino acid sequences, a scoring matrix can be used to calculate the cumulative score. Extension of the word hits in each direction are halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below, due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. The BLAST algorithm parameters W, T and X determine the sensitivity and speed of the alignment.
In one approach, the “percentage of sequence identity” is determined by comparing two optimally aligned sequences over a window of comparison of at least 20 positions, wherein the portion of the polynucleotide or polypeptide sequence in the comparison window may comprise additions or deletions (i.e., gaps) of 20 percent or less, usually 5 to 15 percent, or 10 to 12 percent, as compared to the reference sequences (which does not comprise additions or deletions) for optimal alignment of the two sequences. The percentage is calculated by determining the number of positions at which the identical nucleic acid bases or amino acid residues occur in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the reference sequence (i.e., the window size) and multiplying the results by 100 to yield the percentage of sequence identity.
Yet another way of defining an antibody is as a “derivative” of any of the below-described antibodies and their antigen-binding fragments. The term “derivative” refers to an antibody or antigen-binding fragment thereof that immunospecifically binds to an antigen, but which comprises, one, two, three, four, five or more amino acid substitutions, additions, deletions or modifications relative to a “parental” (or wild-type) molecule. Such amino acid substitutions or additions may introduce naturally occurring (i.e., DNA-encoded) or non-naturally occurring amino acid residues. The term “derivative” encompasses, for example, as variants having altered CH1, hinge, CH2, CH3 or CH4 regions, so as to form, for example antibodies, etc., having variant Fc regions that exhibit enhanced or impaired effector or binding characteristics. The term “derivative” additionally encompasses non-amino acid modifications, for example, amino acids that may be glycosylated (e.g., have altered mannose, 2-N-acetylglucosamine, galactose, fucose, glucose, sialic acid, 5-N-acetylneuraminic acid, 5-glycolneuraminic acid, etc. content), acetylated, pegylated, phosphorylated, amidated, derivatized by known protecting/blocking groups, proteolytic cleavage, linked to a cellular ligand or other protein, etc. In some embodiments, the altered carbohydrate modifications modulate one or more of the following: solubilization of the antibody, facilitation of subcellular transport and secretion of the antibody, promotion of antibody assembly, conformational integrity, and antibody-mediated effector function. In a specific embodiment, the altered carbohydrate modifications enhance antibody mediated effector function relative to the antibody lacking the carbohydrate modification. Carbohydrate modifications that lead to altered antibody mediated effector function are well known in the art (for example, see Shields, R. L. et al. (2002) “Lack Of Fucose On Human IgG N-Linked Oligosaccharide Improves Binding To Human Fcgamma RIII And Antibody-Dependent Cellular Toxicity,” J. Biol. Chem. 277(30): 26733-26740; Davies J. et al. (2001) “Expression Of GnTIII In A Recombinant Anti-CD20 CHO Production Cell Line: Expression Of Antibodies With Altered Glycoforms Leads To An Increase In ADCC Through Higher Affinity For FC Gamma RIII,” Biotechnology & Bioengineering 74(4): 288-294). Methods of altering carbohydrate contents are known to those skilled in the art, see, e.g., Wallick, S. C. et al. (1988) “Glycosylation Of A VH Residue Of A Monoclonal Antibody Against Alpha (1 - - - - 6) Dextran Increases Its Affinity For Antigen,” J. Exp. Med. 168(3): 1099-1109; Tao, M. H. et al. (1989) “Studies Of Aglycosylated Chimeric Mouse-Human IgG. Role Of Carbohydrate In The Structure And Effector Functions Mediated By The Human IgG Constant Region,” J. Immunol. 143(8): 2595-2601; Routledge, E. G. et al. (1995) “The Effect Of Aglycosylation On The Immunogenicity Of A Humanized Therapeutic CD3 Monoclonal Antibody,” Transplantation 60(8):847-53; Elliott, S. et al. (2003) “Enhancement Of Therapeutic Protein In Vivo Activities Through Glycoengineering,” Nature Biotechnol. 21:414-21; Shields, R. L. et al. (2002) “Lack Of Fucose On Human IgG N-Linked Oligosaccharide Improves Binding To Human Fcgamma Rill And Antibody-Dependent Cellular Toxicity,” J. Biol. Chem. 277(30): 26733-26740).
A derivative antibody or antibody fragment can be generated with an engineered sequence or glycosylation state to confer preferred levels of activity in antibody dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), antibody-dependent neutrophil phagocytosis (ADNP), or antibody-dependent complement deposition (ADCD) functions as measured by bead-based or cell-based assays or in vivo studies in animal models.
A derivative antibody or antibody fragment may be modified by chemical modifications using techniques known to those of skill in the art, including, but not limited to, specific chemical cleavage, acetylation, formulation, metabolic synthesis of tunicamycin, etc. In one embodiment, an antibody derivative will possess a similar or identical function as the parental antibody. In another embodiment, an antibody derivative will exhibit an altered activity relative to the parental antibody. For example, a derivative antibody (or fragment thereof) can bind to its epitope more tightly or be more resistant to proteolysis than the parental antibody.
C. Engineering of Antibody Sequences
In various embodiments, one may choose to engineer sequences of the identified antibodies for a variety of reasons, such as improved expression, improved cross-reactivity or diminished off-target binding. Modified antibodies may be made by any technique known to those of skill in the art, including expression through standard molecular biological techniques, or the chemical synthesis of polypeptides. Methods for recombinant expression are addressed elsewhere in this document. The following is a general discussion of relevant goals techniques for antibody engineering.
Hybridomas may be cultured, then cells lysed, and total RNA extracted. Random hexamers may be used with RT to generate cDNA copies of RNA, and then PCR performed using a multiplex mixture of PCR primers expected to amplify all human variable gene sequences. PCR product can be cloned into pGEM-T Easy vector, then sequenced by automated DNA sequencing using standard vector primers. Assay of binding and neutralization may be performed using antibodies collected from hybridoma supernatants and purified by FPLC, using Protein G columns.
Recombinant full-length IgG antibodies can be generated by subcloning heavy and light chain Fv DNAs from the cloning vector into an IgG plasmid vector, transfected into 293 (e.g., Freestyle) cells or CHO cells, and antibodies can be collected and purified from the 293 or CHO cell supernatant. Other appropriate host cells systems include bacteria, such as E. coli, insect cells (S2, Sf9, Sf29, High Five), plant cells (e.g., tobacco, with or without engineering for human-like glycans), algae, or in a variety of non-human transgenic contexts, such as mice, rats, goats or cows.
Expression of nucleic acids encoding antibodies, both for the purpose of subsequent antibody purification, and for immunization of a host, is also contemplated. Antibody coding sequences can be RNA, such as native RNA or modified RNA. Modified RNA contemplates certain chemical modifications that confer increased stability and low immunogenicity to mRNAs, thereby facilitating expression of therapeutically important proteins. For instance, N1-methyl-pseudouridine (N1mΨ) outperforms several other nucleoside modifications and their combinations in terms of translation capacity. In addition to turning off the immune/eIF2α phosphorylation-dependent inhibition of translation, incorporated N1mΨ nucleotides dramatically alter the dynamics of the translation process by increasing ribosome pausing and density on the mRNA. Increased ribosome loading of modified mRNAs renders them more permissive for initiation by favoring either ribosome recycling on the same mRNA or de novo ribosome recruitment. Such modifications could be used to enhance antibody expression in vivo following inoculation with RNA. The RNA, whether native or modified, may be delivered as naked RNA or in a delivery vehicle, such as a lipid nanoparticle.
Alternatively, DNA encoding the antibody may be employed for the same purposes. The DNA is included in an expression cassette comprising a promoter active in the host cell for which it is designed. The expression cassette is advantageously included in a replicable vector, such as a conventional plasmid or minivector. Vectors include viral vectors, such as poxviruses, adenoviruses, herpesviruses, adeno-associated viruses, and lentiviruses are contemplated. Replicons encoding antibody genes such as alphavirus replicons based on VEE virus or Sindbis virus are also contemplated. Delivery of such vectors can be performed by needle through intramuscular, subcutaneous, or intradermal routes, or by transcutaneous electroporation when in vivo expression is desired.
The rapid availability of antibody produced in the same host cell and cell culture process as the final cGMP manufacturing process has the potential to reduce the duration of process development programs. Lonza has developed a generic method using pooled transfectants grown in CDACF medium, for the rapid production of small quantities (up to 50 g) of antibodies in CHO cells. Although slightly slower than a true transient system, the advantages include a higher product concentration and use of the same host and process as the production cell line. Example of growth and productivity of GS-CHO pools, expressing a model antibody, in a disposable bioreactor: in a disposable bag bioreactor culture (5 L working volume) operated in fed-batch mode, a harvest antibody concentration of 2 g/L was achieved within 9 weeks of transfection.
Antibody molecules will comprise fragments (such as F(ab′), F(ab′)2) that are produced, for example, by the proteolytic cleavage of the mAbs, or single-chain immunoglobulins producible, for example, via recombinant means. F(ab′) antibody derivatives are monovalent, while F(ab′)2 antibody derivatives are bivalent. In one embodiment, such fragments can be combined with one another, or with other antibody fragments or receptor ligands to form “chimeric” binding molecules. Significantly, such chimeric molecules may contain substituents capable of binding to different epitopes of the same molecule.
In related embodiments, the antibody is a derivative of the disclosed antibodies, e.g., an antibody comprising the CDR sequences identical to those in the disclosed antibodies (e.g., a chimeric, or CDR-grafted antibody). Alternatively, one may wish to make modifications, such as introducing conservative changes into an antibody molecule. In making such changes, the hydropathic index of amino acids may be considered. The importance of the hydropathic amino acid index in conferring interactive biologic function on a protein is generally understood in the art (Kyte and Doolittle, 1982). It is accepted that the relative hydropathic character of the amino acid contributes to the secondary structure of the resultant protein, which in turn defines the interaction of the protein with other molecules, for example, enzymes, substrates, receptors, DNA, antibodies, antigens, and the like.
It also is understood in the art that the substitution of like amino acids can be made effectively on the basis of hydrophilicity. U.S. Pat. No. 4,554,101, incorporated herein by reference, states that the greatest local average hydrophilicity of a protein, as governed by the hydrophilicity of its adjacent amino acids, correlates with a biological property of the protein. As detailed in U.S. Pat. No. 4,554,101, the following hydrophilicity values have been assigned to amino acid residues: basic amino acids: arginine (+3.0), lysine (+3.0), and histidine (−0.5); acidic amino acids: aspartate (+3.0±1), glutamate (+3.0±1), asparagine (+0.2), and glutamine (+0.2); hydrophilic, nonionic amino acids: serine (+0.3), asparagine (+0.2), glutamine (+0.2), and threonine (−0.4), sulfur containing amino acids: cysteine (−1.0) and methionine (−1.3); hydrophobic, nonaromatic amino acids: valine (−1.5), leucine (−1.8), isoleucine (−1.8), proline (−0.5±1), alanine (−0.5), and glycine (0); hydrophobic, aromatic amino acids: tryptophan (−3.4), phenylalanine (−2.5), and tyrosine (−2.3).
It is understood that an amino acid can be substituted for another having a similar hydrophilicity and produce a biologically or immunologically modified protein. In such changes, the substitution of amino acids whose hydrophilicity values are within ±2 is preferred, those that are within ±1 are particularly preferred, and those within ±0.5 are even more particularly preferred.
As outlined above, amino acid substitutions generally are based on the relative similarity of the amino acid side-chain substituents, for example, their hydrophobicity, hydrophilicity, charge, size, and the like. Exemplary substitutions that take into consideration the various foregoing characteristics are well known to those of skill in the art and include: arginine and lysine; glutamate and aspartate; serine and threonine; glutamine and asparagine; and valine, leucine and isoleucine.
The present disclosure also contemplates isotype modification. By modifying the Fc region to have a different isotype, different functionalities can be achieved. For example, changing to IgG1 can increase antibody dependent cell cytotoxicity, switching to class A can improve tissue distribution, and switching to class M can improve valency.
Alternatively or additionally, it may be useful to combine amino acid modifications with one or more further amino acid modifications that alter C1q binding and/or the complement dependent cytotoxicity (CDC) function of the Fc region of an IL-23p19 binding molecule. The binding polypeptide of particular interest may be one that binds to C1q and displays complement dependent cytotoxicity. Polypeptides with pre-existing C1q binding activity, optionally further having the ability to mediate CDC may be modified such that one or both of these activities are enhanced Amino acid modifications that alter C1q and/or modify its complement dependent cytotoxicity function are described, for example, in WO/0042072, which is hereby incorporated by reference.
One can design an Fc region of an antibody with altered effector function, e.g., by modifying C1q binding and/or FcγR binding and thereby changing CDC activity and/or ADCC activity. “Effector functions” are responsible for activating or diminishing a biological activity (e.g., in a subject). Examples of effector functions include, but are not limited to: C1q binding; complement dependent cytotoxicity (CDC); Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC); phagocytosis; down regulation of cell surface receptors (e.g., B cell receptor; BCR), etc. Such effector functions may require the Fc region to be combined with a binding domain (e.g., an antibody variable domain) and can be assessed using various assays (e.g., Fc binding assays, ADCC assays, CDC assays, etc.).
For example, one can generate a variant Fc region of an antibody with improved C1q binding and improved FcγRIII binding (e.g., having both improved ADCC activity and improved CDC activity). Alternatively, if it is desired that effector function be reduced or ablated, a variant Fc region can be engineered with reduced CDC activity and/or reduced ADCC activity. In other embodiments, only one of these activities may be increased, and, optionally, also the other activity reduced (e.g., to generate an Fc region variant with improved ADCC activity, but reduced CDC activity and vice versa).
FcRn binding. Fc mutations can also be introduced and engineered to alter their interaction with the neonatal Fc receptor (FcRn) and improve their pharmacokinetic properties. A collection of human Fc variants with improved binding to the FcRn have been described (Shields et al., (2001). High resolution mapping of the binding site on human IgG1 for FcγRI, FcγRII, FcγRIII, and FcRn and design of IgG1 variants with improved binding to the FcγR, (J. Biol. Chem. 276:6591-6604). A number of methods are known that can result in increased half-life (Kuo and Aveson, (2011)), including amino acid modifications may be generated through techniques including alanine scanning mutagenesis, random mutagenesis and screening to assess the binding to the neonatal Fc receptor (FcRn) and/or the in vivo behavior. Computational strategies followed by mutagenesis may also be used to select one of amino acid mutations to mutate.
The present disclosure therefore provides a variant of an antigen binding protein with optimized binding to FcRn. In a particular embodiment, the said variant of an antigen binding protein comprises at least one amino acid modification in the Fc region of said antigen binding protein, wherein said modification is selected from the group consisting of 226, 227, 228, 230, 231, 233, 234, 239, 241, 243, 246, 250, 252, 256, 259, 264, 265, 267, 269, 270, 276, 284, 285, 288, 289, 290, 291, 292, 294, 297, 298, 299, 301, 302, 303, 305, 307, 308, 309, 311, 315, 317, 320, 322, 325, 327, 330, 332, 334, 335, 338, 340, 342, 343, 345, 347, 350, 352, 354, 355, 356, 359, 360, 361, 362, 369, 370, 371, 375, 378, 380, 382, 384, 385, 386, 387, 389, 390, 392, 393, 394, 395, 396, 397, 398, 399, 400, 401 403, 404, 408, 411, 412, 414, 415, 416, 418, 419, 420, 421, 422, 424, 426, 428, 433, 434, 438, 439, 440, 443, 444, 445, 446 and 447 of the Fc region as compared to said parent polypeptide, wherein the numbering of the amino acids in the Fc region is that of the EU index in Kabat. In a further aspect of the disclosure the modifications are M252Y/S254T/T256E.
Additionally, various publications describe methods for obtaining physiologically active molecules whose half-lives are modified, see for example Kontermann (2009) either by introducing an FcRn-binding polypeptide into the molecules or by fusing the molecules with antibodies whose FcRn-binding affinities are preserved but affinities for other Fc receptors have been greatly reduced or fusing with FcRn binding domains of antibodies.
Derivatized antibodies may be used to alter the half-lives (e.g., serum half-lives) of parental antibodies in a mammal, particularly a human. Such alterations may result in a half-life of greater than 15 days, preferably greater than 20 days, greater than 25 days, greater than 30 days, greater than 35 days, greater than 40 days, greater than 45 days, greater than 2 months, greater than 3 months, greater than 4 months, or greater than 5 months. The increased half-lives of the antibodies of the present disclosure or fragments thereof in a mammal, preferably a human, results in a higher serum titer of said antibodies or antibody fragments in the mammal, and thus reduces the frequency of the administration of said antibodies or antibody fragments and/or reduces the concentration of said antibodies or antibody fragments to be administered. Antibodies or fragments thereof having increased in vivo half-lives can be generated by techniques known to those of skill in the art. For example, antibodies or fragments thereof with increased in vivo half-lives can be generated by modifying (e.g., substituting, deleting or adding) amino acid residues identified as involved in the interaction between the Fc domain and the FcRn receptor.
Beltramello et al. (2010) previously reported the modification of neutralizing mAbs, due to their tendency to enhance dengue virus infection, by generating in which leucine residues at positions 1.3 and 1.2 of CH2 domain (according to the IMGT unique numbering for C-domain) were substituted with alanine residues. This modification, also known as “LALA” mutation, abolishes antibody binding to FcγRI, FcγRII and FcγRIIIa, as described by Hessell et al. (2007). The variant and unmodified recombinant mAbs were compared for their capacity to neutralize and enhance infection by the four dengue virus serotypes. LALA variants retained the same neutralizing activity as unmodified mAb but were completely devoid of enhancing activity. LALA mutations of this nature are therefore contemplated in the context of the presently disclosed antibodies.
Altered Glycosylation. A particular embodiment of the present disclosure is an isolated monoclonal antibody, or antigen binding fragment thereof, containing a substantially homogeneous glycan without sialic acid, galactose, or fucose. The monoclonal antibody comprises a heavy chain variable region and a light chain variable region, both of which may be attached to heavy chain or light chain constant regions respectively. The aforementioned substantially homogeneous glycan may be covalently attached to the heavy chain constant region.
Another embodiment of the present disclosure comprises a mAb with a novel Fc glycosylation pattern. The isolated monoclonal antibody, or antigen binding fragment thereof, is present in a substantially homogenous composition represented by the GNGN or G1/G2 glycoform. Fc glycosylation plays a significant role in anti-viral and anti-cancer properties of therapeutic mAbs. The disclosure is in line with a recent study that shows increased anti-lentivirus cell-mediated viral inhibition of a fucose free anti-HIV mAb in vitro. This embodiment of the present disclosure with homogenous glycans lacking a core fucose, showed increased protection against specific viruses by a factor greater than two-fold. Elimination of core fucose dramatically improves the ADCC activity of mAbs mediated by natural killer (NK) cells but appears to have the opposite effect on the ADCC activity of polymorphonuclear cells (PMNs).
The isolated monoclonal antibody, or antigen binding fragment thereof, comprising a substantially homogenous composition represented by the GNGN or G1/G2 glycoform exhibits increased binding affinity for Fc gamma RI and Fc gamma RIII compared to the same antibody without the substantially homogeneous GNGN glycoform and with G0, G1F, G2F, GNF, GNGNF or GNGNFX containing glycoforms. In one embodiment of the present disclosure, the antibody dissociates from Fc gamma RI with a Kd of 1×10−8 M or less and from Fc gamma RIII with a Kd of 1×10−7 M or less.
Glycosylation of an Fc region is typically either N-linked or O-linked. N-linked refers to the attachment of the carbohydrate moiety to the side chain of an asparagine residue. O-linked glycosylation refers to the attachment of one of the sugars N-acetylgalactosamine, galactose, or xylose to a hydroxyamino acid, most commonly serine or threonine, although 5-hydroxyproline or 5-hydroxylysine may also be used. The recognition sequences for enzymatic attachment of the carbohydrate moiety to the asparagine side chain peptide sequences are asparagine-X-serine and asparagine-X-threonine, where X is any amino acid except proline. Thus, the presence of either of these peptide sequences in a polypeptide creates a potential glycosylation site.
The glycosylation pattern may be altered, for example, by deleting one or more glycosylation site(s) found in the polypeptide, and/or adding one or more glycosylation site(s) that are not present in the polypeptide. Addition of glycosylation sites to the Fc region of an antibody is conveniently accomplished by altering the amino acid sequence such that it contains one or more of the above-described tripeptide sequences (for N-linked glycosylation sites). An exemplary glycosylation variant has an amino acid substitution of residue Asn 297 of the heavy chain. The alteration may also be made by the addition of, or substitution by, one or more serine or threonine residues to the sequence of the original polypeptide (for O-linked glycosylation sites). Additionally, a change of Asn 297 to Ala can remove one of the glycosylation sites.
In certain embodiments, the antibody is expressed in cells that express beta (1,4)-N-acetylglucosaminyltransferase III (GnT III), such that GnT III adds GlcNAc to the IL-23p19 antibody. Methods for producing antibodies in such a fashion are provided in WO/9954342, WO/03011878, patent publication 20030003097A1, and Umana et al., Nature Biotechnology, 17:176-180, February 1999. Cell lines can be altered to enhance or reduce or eliminate certain post-translational modifications, such as glycosylation, using genome editing technology such as Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR). For example, CRISPR technology can be used to eliminate genes encoding glycosylating enzymes in 293 or CHO cells used to express recombinant monoclonal antibodies.
Elimination of monoclonal antibody protein sequence liabilities. It is possible to engineer the antibody variable gene sequences obtained from human B cells to enhance their manufacturability and safety. Potential protein sequence liabilities can be identified by searching for sequence motifs associated with sites containing:
1) Unpaired Cys residues,
2) N-linked glycosylation,
3) Asn deamidation,
4) Asp isomerization,
5) SYE truncation,
6) Met oxidation,
7) Trp oxidation,
8) N-terminal glutamate,
9) Integrin binding,
10) CD11c/CD18 binding, or
11) Fragmentation
Such motifs can be eliminated by altering the synthetic gene for the cDNA encoding recombinant antibodies.
Protein engineering efforts in the field of development of therapeutic antibodies clearly reveal that certain sequences or residues are associated with solubility differences (Fernandez-Escamilla et al., Nature Biotech., 22 (10), 1302-1306, 2004; Chennamsetty et al., PNAS, 106 (29), 11937-11942, 2009; Voynov et al., Biocon. Chem., 21(2), 385-392, 2010) Evidence from solubility-altering mutations in the literature indicate that some hydrophilic residues such as aspartic acid, glutamic acid, and serine contribute significantly more favorably to protein solubility than other hydrophilic residues, such as asparagine, glutamine, threonine, lysine, and arginine.
Stability. Antibodies can be engineered for enhanced biophysical properties. One can use elevated temperature to unfold antibodies to determine relative stability, using average apparent melting temperatures. Differential Scanning calorimetry (DSC) measures the heat capacity, Cp, of a molecule (the heat required to warm it, per degree) as a function of temperature. One can use DSC to study the thermal stability of antibodies. DSC data for mAbs is particularly interesting because it sometimes resolves the unfolding of individual domains within the mAb structure, producing up to three peaks in the thermogram (from unfolding of the Fab, CH2, and CH3 domains). Typically unfolding of the Fab domain produces the strongest peak. The DSC profiles and relative stability of the Fc portion show characteristic differences for the human IgG1, IgG2, IgG3, and IgG4 subclasses (Garber and Demarest, Biochem. Biophys. Res. Commun. 355, 751-757, 2007). One also can determine average apparent melting temperature using circular dichroism (CD), performed with a CD spectrometer. Far-UV CD spectra will be measured for antibodies in the range of 200 to 260 nm at increments of 0.5 nm. The final spectra can be determined as averages of 20 accumulations. Residue ellipticity values can be calculated after background subtraction. Thermal unfolding of antibodies (0.1 mg/mL) can be monitored at 235 nm from 25-95° C. and a heating rate of 1° C./min One can use dynamic light scattering (DLS) to assess for propensity for aggregation. DLS is used to characterize size of various particles including proteins. If the system is not disperse in size, the mean effective diameter of the particles can be determined. This measurement depends on the size of the particle core, the size of surface structures, and particle concentration. Since DLS essentially measures fluctuations in scattered light intensity due to particles, the diffusion coefficient of the particles can be determined. DLS software in commercial DLA instruments displays the particle population at different diameters. Stability studies can be done conveniently using DLS. DLS measurements of a sample can show whether the particles aggregate over time or with temperature variation by determining whether the hydrodynamic radius of the particle increases. If particles aggregate, one can see a larger population of particles with a larger radius. Stability depending on temperature can be analyzed by controlling the temperature in situ. Capillary electrophoresis (CE) techniques include proven methodologies for determining features of antibody stability. One can use an iCE approach to resolve antibody protein charge variants due to deamidation, C-terminal lysines, sialylation, oxidation, glycosylation, and any other change to the protein that can result in a change in pI of the protein. Each of the expressed antibody proteins can be evaluated by high throughput, free solution isoelectric focusing (IEF) in a capillary column (cIEF), using a Protein Simple Maurice instrument. Whole-column UV absorption detection can be performed every 30 seconds for real time monitoring of molecules focusing at the isoelectric points (pIs). This approach combines the high resolution of traditional gel IEF with the advantages of quantitation and automation found in column-based separations while eliminating the need for a mobilization step. The technique yields reproducible, quantitative analysis of identity, purity, and heterogeneity profiles for the expressed antibodies. The results identify charge heterogeneity and molecular sizing on the antibodies, with both absorbance and native fluorescence detection modes and with sensitivity of detection down to 0.7 μg/mL.
Solubility. One can determine the intrinsic solubility score of antibody sequences. The intrinsic solubility scores can be calculated using CamSol Intrinsic (Sormanni et al., J Mol Biol 427, 478-490, 2015). The amino acid sequences for residues 95-102 (Kabat numbering) in HCDR3 of each antibody fragment such as a scFv can be evaluated via the online program to calculate the solubility scores. One also can determine solubility using laboratory techniques. Various techniques exist, including addition of lyophilized protein to a solution until the solution becomes saturated and the solubility limit is reached, or concentration by ultrafiltration in a microconcentrator with a suitable molecular weight cut-off. The most straightforward method is induction of amorphous precipitation, which measures protein solubility using a method involving protein precipitation using ammonium sulfate (Trevino et al., J Mol Biol, 366: 449-460, 2007). Ammonium sulfate precipitation gives quick and accurate information on relative solubility values. Ammonium sulfate precipitation produces precipitated solutions with well-defined aqueous and solid phases and requires relatively small amounts of protein. Solubility measurements performed using induction of amorphous precipitation by ammonium sulfate also can be done easily at different pH values. Protein solubility is highly pH dependent, and pH is considered the most important extrinsic factor that affects solubility.
Autoreactivity. Generally, it is thought that autoreactive clones should be eliminated during ontogeny by negative selection, however it has become clear that many human naturally occurring antibodies with autoreactive properties persist in adult mature repertoires, and the autoreactivity may enhance the antiviral function of many antibodies to pathogens. It has been noted that HCDR3 loops in antibodies during early B cell development are often rich in positive charge and exhibit autoreactive patterns (Wardemann et al., Science 301, 1374-1377, 2003). One can test a given antibody for autoreactivity by assessing the level of binding to human origin cells in microscopy (using adherent HeLa or HEp-2 epithelial cells) and flow cytometric cell surface staining (using suspension Jurkat T cells and 293S human embryonic kidney cells). Autoreactivity also can be surveyed using assessment of binding to tissues in tissue arrays.
Preferred residues (“Human Likeness”). B cell repertoire deep sequencing of human B cells from blood donors is being performed on a wide scale in many recent studies. Sequence information about a significant portion of the human antibody repertoire facilitates statistical assessment of antibody sequence features common in healthy humans. With knowledge about the antibody sequence features in a human recombined antibody variable gene reference database, the position specific degree of “Human Likeness” (HL) of an antibody sequence can be estimated. HL has been shown to be useful for the development of antibodies in clinical use, like therapeutic antibodies or antibodies as vaccines. The goal is to increase the human likeness of antibodies to reduce potential adverse effects and anti-antibody immune responses that will lead to significantly decreased efficacy of the antibody drug or can induce serious health implications. One can assess antibody characteristics of the combined antibody repertoire of three healthy human blood donors of about 400 million sequences in total and created a novel “relative Human Likeness” (rHL) score that focuses on the hypervariable region of the antibody. The rHL score allows one to easily distinguish between human (positive score) and non-human sequences (negative score). Antibodies can be engineered to eliminate residues that are not common in human repertoires.
Blood brain barrier. The blood brain barrier regulates the traverse of blood-circulating substances into the brain with selectivity. This barrier may reduce the entry of antibodies into the central nervous system necessary for diagnosis or therapy of central nervous system infection with alphaviruses. It may be possible to exploit the naturally occurring cellular trafficking systems and the receptor-mediated transfer machinery to move antibodies across the blood brain barrier safely to tissue site where the antibodies will be most effective. There have been a large number of studies of molecules that mediate active transport into the brain, including at least 20 receptors, including transferrin receptor, heparin-binding EGF, scavenger receptors AI, BI, EGF receptor, tumor necrosis factor, insulin and insulin-like growth factor receptors, apolipoprotein E receptor 2, leptin receptor, melanotransferrin receptor, or LDL receptors (Preston et al., Adv. Pharmacol. 71: 147-163, 2014). Here, the inventors propose to use one or more of these active transport systems to deliver an alphavirus inhibiting antibody by making a chimeric or bispecific molecule that targets a transporting receptor and possesses a separate domain that targets an alphavirus protein.
pIgR. Encephalitic alphaviruses may enter the brain through the olfactory bulb, which is exposed in the nasal passages. The efficacy of antibody prevention or treatment for encephalitic alphaviruses may be enhanced by delivering a high concentration of the antibody to the nasal passage, especially around the area of the olfactory bulb. Serum immunoglobulins that circulate after parenteral administration may have limited access to the nasal passages because of the inefficiency of passive transudation across this mucosal barrier. Dimerized IgA and IgM can react with the polymeric immunoglobulin receptor (pIgR) produced by respiratory tract epithelial cells. Under normal conditions, the pIgR acts as a transport receptor for IgA and becomes part of the secreted IgA molecule. It renders the IgA molecule less susceptible to proteolytic digestion and more mucophilic, and it the ability of the IgA molecule to interact with potential pathogens and to prevent their attachment to cell surfaces. Here, the inventor proposes to use the pIgR active transport system to deliver an alphavirus inhibiting antibody by making a chimeric or bispecific molecule that targets a transporting receptor and possesses a separate domain that targets an alphavirus protein.
D. Single Chain Antibodies
A single chain variable fragment (scFv) is a fusion of the variable regions of the heavy and light chains of immunoglobulins, linked together with a short (usually serine, glycine) linker. This chimeric molecule retains the specificity of the original immunoglobulin, despite removal of the constant regions and the introduction of a linker peptide. This modification usually leaves the specificity unaltered. These molecules were created historically to facilitate phage display where it is highly convenient to express the antigen binding domain as a single peptide. Alternatively, scFv can be created directly from subcloned heavy and light chains derived from a hybridoma or B cell. Single chain variable fragments lack the constant Fc region found in complete antibody molecules, and thus, the common binding sites (e.g., protein A/G) used to purify antibodies. These fragments can often be purified/immobilized using Protein L since Protein L interacts with the variable region of kappa light chains.
Flexible linkers generally are comprised of helix- and turn-promoting amino acid residues such as alanine, serine and glycine. However, other residues can function as well. Tang et al. (1996) used phage display as a means of rapidly selecting tailored linkers for single-chain antibodies (scFvs) from protein linker libraries. A random linker library was constructed in which the genes for the heavy and light chain variable domains were linked by a segment encoding an 18-amino acid polypeptide of variable composition. The scFv repertoire (approx. 5×106 different members) was displayed on filamentous phage and subjected to affinity selection with hapten. The population of selected variants exhibited significant increases in binding activity but retained considerable sequence diversity. Screening 1054 individual variants subsequently yielded a catalytically active scFv that was produced efficiently in soluble form. Sequence analysis revealed a conserved proline in the linker two residues after the VH C terminus and an abundance of arginines and prolines at other positions as the only common features of the selected tethers.
The recombinant antibodies of the present disclosure may also involve sequences or moieties that permit dimerization or multimerization of the receptors. Such sequences include those derived from IgA, which permit formation of multimers in conjunction with the J-chain. Another multimerization domain is the Gal4 dimerization domain. In other embodiments, the chains may be modified with agents such as biotin/avidin, which permit the combination of two antibodies.
In a separate embodiment, a single-chain antibody can be created by joining receptor light and heavy chains using a non-peptide linker or chemical unit. Generally, the light and heavy chains will be produced in distinct cells, purified, and subsequently linked together in an appropriate fashion (i.e., the N-terminus of the heavy chain being attached to the C-terminus of the light chain via an appropriate chemical bridge).
Cross-linking reagents are used to form molecular bridges that tie functional groups of two different molecules, e.g., a stabilizing and coagulating agent. However, it is contemplated that dimers or multimers of the same analog or heteromeric complexes comprised of different analogs can be created. To link two different compounds in a step-wise manner, hetero-bifunctional cross-linkers can be used that eliminate unwanted homopolymer formation.
An exemplary hetero-bifunctional cross-linker contains two reactive groups: one reacting with primary amine group (e.g., N-hydroxy succinimide) and the other reacting with a thiol group (e.g., pyridyl disulfide, maleimides, halogens, etc.). Through the primary amine reactive group, the cross-linker may react with the lysine residue(s) of one protein (e.g., the selected antibody or fragment) and through the thiol reactive group, the cross-linker, already tied up to the first protein, reacts with the cysteine residue (free sulfhydryl group) of the other protein (e.g., the selective agent).
It is preferred that a cross-linker having reasonable stability in blood will be employed. Numerous types of disulfide-bond containing linkers are known that can be successfully employed to conjugate targeting and therapeutic/preventative agents. Linkers that contain a disulfide bond that is sterically hindered may prove to give greater stability in vivo, preventing release of the targeting peptide prior to reaching the site of action. These linkers are thus one group of linking agents.
Another cross-linking reagent is SMPT, which is a bifunctional cross-linker containing a disulfide bond that is “sterically hindered” by an adjacent benzene ring and methyl groups. It is believed that steric hindrance of the disulfide bond serves a function of protecting the bond from attack by thiolate anions such as glutathione which can be present in tissues and blood, and thereby help in preventing decoupling of the conjugate prior to the delivery of the attached agent to the target site.
The SMPT cross-linking reagent, as with many other known cross-linking reagents, lends the ability to cross-link functional groups such as the SH of cysteine or primary amines (e.g., the epsilon amino group of lysine). Another possible type of cross-linker includes the hetero-bifunctional photoreactive phenylazides containing a cleavable disulfide bond such as sulfosuccinimidyl-2-(p-azido salicylamido) ethyl-1,3′-dithiopropionate. The N-hydroxy-succinimidyl group reacts with primary amino groups and the phenylazide (upon photolysis) reacts non-selectively with any amino acid residue.
In addition to hindered cross-linkers, non-hindered linkers also can be employed in accordance herewith. Other useful cross-linkers, not considered to contain or generate a protected disulfide, include SATA, SPDP and 2-iminothiolane (Wawrzynczak & Thorpe, 1987). The use of such cross-linkers is well understood in the art. Another embodiment involves the use of flexible linkers.
U.S. Pat. No. 4,680,338 describes bifunctional linkers useful for producing conjugates of ligands with amine-containing polymers and/or proteins, especially for forming antibody conjugates with chelators, drugs, enzymes, detectable labels and the like. U.S. Pat. Nos. 5,141,648 and 5,563,250 disclose cleavable conjugates containing a labile bond that is cleavable under a variety of mild conditions. This linker is particularly useful in that the agent of interest may be bonded directly to the linker, with cleavage resulting in release of the active agent. Particular uses include adding a free amino or free sulfhydryl group to a protein, such as an antibody, or a drug.
U.S. Pat. No. 5,856,456 provides peptide linkers for use in connecting polypeptide constituents to make fusion proteins, e.g., single chain antibodies. The linker is up to about 50 amino acids in length, contains at least one occurrence of a charged amino acid (preferably arginine or lysine) followed by a proline, and is characterized by greater stability and reduced aggregation. U.S. Pat. No. 5,880,270 discloses aminooxy-containing linkers useful in a variety of immunodiagnostic and separative techniques.
E. Multispecific Antibodies
In certain embodiments, antibodies of the present disclosure are bispecific or multispecific. Bispecific antibodies are antibodies that have binding specificities for at least two different epitopes. Exemplary bispecific antibodies may bind to two different epitopes of a single antigen. Other such antibodies may combine a first antigen binding site with a binding site for a second antigen. Alternatively, an anti-pathogen arm may be combined with an arm that binds to a triggering molecule on a leukocyte, such as a T-cell receptor molecule (e.g., CD3), or Fc receptors for IgG (FcγR), such as FcγRI (CD64), FcγRII (CD32) and Fc gamma RIII (CD16), so as to focus and localize cellular defense mechanisms to the infected cell. Bispecific antibodies may also be used to localize cytotoxic agents to infected cells. These antibodies possess a pathogen-binding arm and an arm that binds the cytotoxic agent (e.g., saporin, anti-interferon-α, vinca alkaloid, ricin A chain, methotrexate or radioactive isotope hapten). Bispecific antibodies can be prepared as full-length antibodies or antibody fragments (e.g., F(ab′)2 bispecific antibodies). WO 96/16673 describes a bispecific anti-ErbB2/anti-Fc gamma RIII antibody and U.S. Pat. No. 5,837,234 discloses a bispecific anti-ErbB2/anti-Fc gamma RI antibody. A bispecific anti-ErbB2/Fc alpha antibody is shown in WO98/02463. U.S. Pat. No. 5,821,337 teaches a bispecific anti-ErbB2/anti-CD3 antibody.
Methods for making bispecific antibodies are known in the art. Traditional production of full-length bispecific antibodies is based on the co-expression of two immunoglobulin heavy chain-light chain pairs, where the two chains have different specificities (Millstein et al., Nature, 305:537-539 (1983)). Because of the random assortment of immunoglobulin heavy and light chains, these hybridomas (quadromas) produce a potential mixture of ten different antibody molecules, of which only one has the correct bispecific structure. Purification of the correct molecule, which is usually done by affinity chromatography steps, is rather cumbersome, and the product yields are low. Similar procedures are disclosed in WO 93/08829, and in Traunecker et al., EMBO J., 10:3655-3659 (1991).
According to a different approach, antibody variable regions with the desired binding specificities (antibody-antigen combining sites) are fused to immunoglobulin constant domain sequences. Preferably, the fusion is with an Ig heavy chain constant domain, comprising at least part of the hinge, CH2, and CH3 regions. It is preferred to have the first heavy-chain constant region (CH1) containing the site necessary for light chain bonding, present in at least one of the fusions. DNAs encoding the immunoglobulin heavy chain fusions and, if desired, the immunoglobulin light chain, are inserted into separate expression vectors, and are co-transfected into a suitable host cell. This provides for greater flexibility in adjusting the mutual proportions of the three polypeptide fragments in embodiments when unequal ratios of the three polypeptide chains used in the construction provide the optimum yield of the desired bispecific antibody. It is, however, possible to insert the coding sequences for two or all three polypeptide chains into a single expression vector when the expression of at least two polypeptide chains in equal ratios results in high yields or when the ratios have no significant effect on the yield of the desired chain combination.
In a particular embodiment of this approach, the bispecific antibodies are composed of a hybrid immunoglobulin heavy chain with a first binding specificity in one arm, and a hybrid immunoglobulin heavy chain-light chain pair (providing a second binding specificity) in the other arm. It was found that this asymmetric structure facilitates the separation of the desired bispecific compound from unwanted immunoglobulin chain combinations, as the presence of an immunoglobulin light chain in only one half of the bispecific molecule provides for a facile way of separation. This approach is disclosed in WO 94/04690. For further details of generating bispecific antibodies see, for example, Suresh et al., Methods in Enzymology, 121:210 (1986).
According to another approach described in U.S. Pat. No. 5,731,168, the interface between a pair of antibody molecules can be engineered to maximize the percentage of heterodimers that are recovered from recombinant cell culture. The preferred interface comprises at least a part of the CH3 domain. In this method, one or more small amino acid side chains from the interface of the first antibody molecule are replaced with larger side chains (e.g., tyrosine or tryptophan). Compensatory “cavities” of identical or similar size to the large side chain(s) are created on the interface of the second antibody molecule by replacing large amino acid side chains with smaller ones (e.g., alanine or threonine). This provides a mechanism for increasing the yield of the heterodimer over other unwanted end-products such as homodimers.
Bispecific antibodies include cross-linked or “heteroconjugate” antibodies. For example, one of the antibodies in the heteroconjugate can be coupled to avidin, the other to biotin. Such antibodies have, for example, been proposed to target immune system cells to unwanted cells (U.S. Pat. No. 4,676,980), and for treatment of HIV infection (WO 91/00360, WO 92/200373, and EP 03089). Heteroconjugate antibodies may be made using any convenient cross-linking methods. Suitable cross-linking agents are well known in the art, and are disclosed in U.S. Pat. No. 4,676,980, along with a number of cross-linking techniques.
Techniques for generating bispecific antibodies from antibody fragments have also been described in the literature. For example, bispecific antibodies can be prepared using chemical linkage. Brennan et al., Science, 229: 81 (1985) describe a procedure wherein intact antibodies are proteolytically cleaved to generate F(ab′)2 fragments. These fragments are reduced in the presence of the dithiol complexing agent, sodium arsenite, to stabilize vicinal dithiols and prevent intermolecular disulfide formation. The Fab′ fragments generated are then converted to thionitrobenzoate (TNB) derivatives. One of the Fab′-TNB derivatives is then reconverted to the Fab′-thiol by reduction with mercaptoethylamine and is mixed with an equimolar amount of the other Fab′-TNB derivative to form the bispecific antibody. The bispecific antibodies produced can be used as agents for the selective immobilization of enzymes.
Techniques exist that facilitate the direct recovery of Fab′-SH fragments from E. coli, which can be chemically coupled to form bispecific antibodies. Shalaby et al., J. Exp. Med., 175: 217-225 (1992) describe the production of a humanized bispecific antibody F(ab′)2 molecule. Each Fab′ fragment was separately secreted from E. coli and subjected to directed chemical coupling in vitro to form the bispecific antibody. The bispecific antibody thus formed was able to bind to cells overexpressing the ErbB2 receptor and normal human T cells, as well as trigger the lytic activity of human cytotoxic lymphocytes against human breast tumor targets.
Various techniques for making and isolating bispecific antibody fragments directly from recombinant cell culture have also been described (Merchant et al., Nat. Biotechnol. 16, 677-681 (1998). doi:10.1038/nbt0798-677pmid:9661204). For example, bispecific antibodies have been produced using leucine zippers (Kostelny et al., J. Immunol., 148(5):1547-1553, 1992). The leucine zipper peptides from the Fos and Jun proteins were linked to the Fab′ portions of two different antibodies by gene fusion. The antibody homodimers were reduced at the hinge region to form monomers and then re-oxidized to form the antibody heterodimers. This method can also be utilized for the production of antibody homodimers. The “diabody” technology described by Hollinger et al., Proc. Natl. Acad. Sci. USA, 90:6444-6448 (1993) has provided an alternative mechanism for making bispecific antibody fragments. The fragments comprise a VH connected to a VL by a linker that is too short to allow pairing between the two domains on the same chain. Accordingly, the VH and VL domains of one fragment are forced to pair with the complementary VL and VH domains of another fragment, thereby forming two antigen-binding sites. Another strategy for making bispecific antibody fragments by the use of single-chain Fv (sFv) dimers has also been reported. See Gruber et al., J. Immunol., 152:5368 (1994).
In a particular embodiment, a bispecific or multispecific antibody may be formed as a DOCK-AND-LOCK™ (DNL™) complex (see, e.g., U.S. Pat. Nos. 7,521,056; 7,527,787; 7,534,866; 7,550,143 and 7,666,400, the Examples section of each of which is incorporated herein by reference.) Generally, the technique takes advantage of the specific and high-affinity binding interactions that occur between a dimerization and docking domain (DDD) sequence of the regulatory (R) subunits of cAMP-dependent protein kinase (PKA) and an anchor domain (AD) sequence derived from any of a variety of AKAP proteins (Baillie et al., FEBS Letters. 2005; 579: 3264; Wong and Scott, Nat. Rev. Mol. Cell Biol. 2004; 5: 959). The DDD and AD peptides may be attached to any protein, peptide or other molecule. Because the DDD sequences spontaneously dimerize and bind to the AD sequence, the technique allows the formation of complexes between any selected molecules that may be attached to DDD or AD sequences.
Antibodies with more than two valencies are contemplated. For example, trispecific antibodies can be prepared (Tutt et al., J. Immunol. 147: 60, 1991; Xu et al., Science, 358(6359):85-90, 2017). A multivalent antibody may be internalized (and/or catabolized) faster than a bivalent antibody by a cell expressing an antigen to which the antibodies bind. The antibodies of the present disclosure can be multivalent antibodies with three or more antigen binding sites (e.g., tetravalent antibodies), which can be readily produced by recombinant expression of nucleic acid encoding the polypeptide chains of the antibody. The multivalent antibody can comprise a dimerization domain and three or more antigen binding sites. The preferred dimerization domain comprises (or consists of) an Fc region or a hinge region. In this scenario, the antibody will comprise an Fc region and three or more antigen binding sites amino-terminal to the Fc region. The preferred multivalent antibody herein comprises (or consists of) three to about eight, but preferably four, antigen binding sites. The multivalent antibody comprises at least one polypeptide chain (and preferably two polypeptide chains), wherein the polypeptide chain(s) comprise two or more variable regions. For instance, the polypeptide chain(s) may comprise VD1-(X1)n-VD2-(X2)n-Fc, wherein VD1 is a first variable region, VD2 is a second variable region, Fc is one polypeptide chain of an Fc region, X1 and X2 represent an amino acid or polypeptide, and n is 0 or 1. For instance, the polypeptide chain(s) may comprise: VH-CH1-flexible linker-VH-CH1-Fc region chain; or VH-CH1-VH-CH1-Fc region chain. The multivalent antibody herein preferably further comprises at least two (and preferably four) light chain variable region polypeptides. The multivalent antibody herein may, for instance, comprise from about two to about eight light chain variable region polypeptides. The light chain variable region polypeptides contemplated here comprise a light chain variable region and, optionally, further comprise a CL domain.
Charge modifications are particularly useful in the context of a multispecific antibody, where amino acid substitutions in Fab molecules result in reducing the mispairing of light chains with non-matching heavy chains (Bence-Jones-type side products), which can occur in the production of Fab-based bi-/multispecific antigen binding molecules with a VH/VL exchange in one (or more, in case of molecules comprising more than two antigen-binding Fab molecules) of their binding arms (see also PCT publication no. WO 2015/150447, particularly the examples therein, incorporated herein by reference in its entirety).
Accordingly, in particular embodiments, an antibody comprised in the therapeutic agent comprises
In another embodiment of the antibody, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 or the amino acid at position 213 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).
In a further embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).
In a particular embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)) and the amino acid at position 123 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat) (in one preferred embodiment independently by lysine (K) or arginine (R)), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to Kabat EU index).
In a more particular embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by lysine (K) or arginine (R) (numbering according to Kabat), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted by glutamic acid (E) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index).
In an even more particular embodiment, in the constant domain CL of the first Fab molecule under a) the amino acid at position 124 is substituted by lysine (K) (numbering according to Kabat) and the amino acid at position 123 is substituted by arginine (R) (numbering according to Kabat), and in the constant domain CH1 of the first Fab molecule under a) the amino acid at position 147 is substituted by glutamic acid (E) (numbering according to Kabat EU index) and the amino acid at position 213 is substituted by glutamic acid (E) (numbering according to Kabat EU index).
F. Chimeric Antigen Receptors
Artificial T cell receptors (also known as chimeric T cell receptors, chimeric immunoreceptors, chimeric antigen receptors (CARs)) are engineered receptors, which graft an arbitrary specificity onto an immune effector cell. Typically, these receptors are used to graft the specificity of a monoclonal antibody onto a T cell, with transfer of their coding sequence facilitated by retroviral vectors. In this way, a large number of target-specific T cells can be generated for adoptive cell transfer. Phase I clinical studies of this approach show efficacy.
The most common form of these molecules are fusions of single-chain variable fragments (scFv) derived from monoclonal antibodies, fused to CD3-zeta transmembrane and endodomain Such molecules result in the transmission of a zeta signal in response to recognition by the scFv of its target. An example of such a construct is 14g2a-Zeta, which is a fusion of a scFv derived from hybridoma 14g2a (which recognizes disialoganglioside GD2). When T cells express this molecule (usually achieved by oncoretroviral vector transduction), they recognize and kill target cells that express GD2 (e.g., neuroblastoma cells). To target malignant B cells, investigators have redirected the specificity of T cells using a chimeric immunoreceptor specific for the B-lineage molecule, CD19.
The variable portions of an immunoglobulin heavy and light chain are fused by a flexible linker to form a scFv. This scFv is preceded by a signal peptide to direct the nascent protein to the endoplasmic reticulum and subsequent surface expression (this is cleaved). A flexible spacer allows to the scFv to orient in different directions to enable antigen binding. The transmembrane domain is a typical hydrophobic alpha helix usually derived from the original molecule of the signaling endodomain which protrudes into the cell and transmits the desired signal.
Type I proteins are in fact two protein domains linked by a transmembrane alpha helix in between. The cell membrane lipid bilayer, through which the transmembrane domain passes, acts to isolate the inside portion (endodomain) from the external portion (ectodomain). It is not so surprising that attaching an ectodomain from one protein to an endodomain of another protein results in a molecule that combines the recognition of the former to the signal of the latter.
Ectodomain. A signal peptide directs the nascent protein into the endoplasmic reticulum. This is essential if the receptor is to be glycosylated and anchored in the cell membrane. Any eukaryotic signal peptide sequence usually works fine. Generally, the signal peptide natively attached to the amino-terminal most component is used (e.g., in a scFv with orientation light chain-linker-heavy chain, the native signal of the light-chain is used
The antigen recognition domain is usually an scFv. There are however many alternatives. An antigen recognition domain from native T-cell receptor (TCR) alpha and beta single chains have been described, as have simple ectodomains (e.g., CD4 ectodomain to recognize HIV infected cells) and more exotic recognition components such as a linked cytokine (which leads to recognition of cells bearing the cytokine receptor). In fact, almost anything that binds a given target with high affinity can be used as an antigen recognition region.
A spacer region links the antigen binding domain to the transmembrane domain. It should be flexible enough to allow the antigen binding domain to orient in different directions to facilitate antigen recognition. The simplest form is the hinge region from IgG1. Alternatives include the CH2CH3 region of immunoglobulin and portions of CD3. For most scFv based constructs, the IgG1 hinge suffices. However, the best spacer often has to be determined empirically.
Transmembrane domain. The transmembrane domain is a hydrophobic alpha helix that spans the membrane. Generally, the transmembrane domain from the most membrane proximal component of the endodomain is used. Interestingly, using the CD3-zeta transmembrane domain may result in incorporation of the artificial TCR into the native TCR a factor that is dependent on the presence of the native CD3-zeta transmembrane charged aspartic acid residue. Different transmembrane domains result in different receptor stability. The CD28 transmembrane domain results in a brightly expressed, stable receptor.
Endodomain. This is the “business-end” of the receptor. After antigen recognition, receptors cluster and a signal is transmitted to the cell. The most commonly used endodomain component is CD3-zeta which contains 3 ITAMs. This transmits an activation signal to the T cell after antigen is bound. CD3-zeta may not provide a fully competent activation signal and additional co-stimulatory signaling is needed.
“First-generation” CARs typically had the intracellular domain from the CD3 chain, which is the primary transmitter of signals from endogenous TCRs. “Second-generation” CARs add intracellular signaling domains from various costimulatory protein receptors (e.g., CD28, 41BB, ICOS) to the cytoplasmic tail of the CAR to provide additional signals to the T cell. Preclinical studies have indicated that the second generation of CAR designs improves the antitumor activity of T cells. More recent, “third-generation” CARs combine multiple signaling domains, such as CD3z-CD28-41BB or CD3z-CD28-OX40, to further augment potency.
G. ADCs
Antibody Drug Conjugates or ADCs are a new class of highly potent biopharmaceutical drugs designed as a targeted therapy for the treatment of people with infectious disease. ADCs are complex molecules composed of an antibody (a whole mAb or an antibody fragment such as a single-chain variable fragment, or scFv) linked, via a stable chemical linker with labile bonds, to a biological active cytotoxic/anti-viral payload or drug. Antibody Drug Conjugates are examples of bioconjugates and immunoconjugates.
By combining the unique targeting capabilities of monoclonal antibodies with the cancer-killing ability of cytotoxic drugs, antibody-drug conjugates allow sensitive discrimination between healthy and diseased tissue. This means that, in contrast to traditional systemic approaches, antibody-drug conjugates target and attack the infected cell so that healthy cells are less severely affected.
In the development ADC-based anti-tumor therapies, an anticancer drug (e.g., a cell toxin or cytotoxin) is coupled to an antibody that specifically targets a certain cell marker (e.g., a protein that, ideally, is only to be found in or on infected cells). Antibodies track these proteins down in the body and attach themselves to the surface of cancer cells. The biochemical reaction between the antibody and the target protein (antigen) triggers a signal in the tumor cell, which then absorbs or internalizes the antibody together with the cytotoxin. After the ADC is internalized, the cytotoxic drug is released and kills the cell or impairs viral replication. Due to this targeting, ideally the drug has lower side effects and gives a wider therapeutic window than other agents.
A stable link between the antibody and cytotoxic/anti-viral agent is a crucial aspect of an ADC. Linkers are based on chemical motifs including disulfides, hydrazones or peptides (cleavable), or thioethers (noncleavable) and control the distribution and delivery of the cytotoxic agent to the target cell. Cleavable and noncleavable types of linkers have been proven to be safe in preclinical and clinical trials. Brentuximab vedotin includes an enzyme-sensitive cleavable linker that delivers the potent and highly toxic antimicrotubule agent Monomethyl auristatin E or MMAE, a synthetic antineoplastic agent, to human specific CD30-positive malignant cells. Because of its high toxicity MMAE, which inhibits cell division by blocking the polymerization of tubulin, cannot be used as a single-agent chemotherapeutic drug. However, the combination of MMAE linked to an anti-CD30 monoclonal antibody (cAC10, a cell membrane protein of the tumor necrosis factor or TNF receptor) proved to be stable in extracellular fluid, cleavable by cathepsin and safe for therapy. Trastuzumab emtansine, the other approved ADC, is a combination of the microtubule-formation inhibitor mertansine (DM-1), a derivative of the Maytansine, and antibody trastuzumab (Herceptin®/Genentech/Roche) attached by a stable, non-cleavable linker.
The availability of better and more stable linkers has changed the function of the chemical bond. The type of linker, cleavable or noncleavable, lends specific properties to the cytotoxic (anti-cancer) drug. For example, a non-cleavable linker keeps the drug within the cell. As a result, the entire antibody, linker and cytotoxic agent enter the targeted cancer cell where the antibody is degraded to the level of an amino acid. The resulting complex-amino acid, linker and cytotoxic agent—now becomes the active drug. In contrast, cleavable linkers are catalyzed by enzymes in the host cell where it releases the cytotoxic agent.
Another type of cleavable linker, currently in development, adds an extra molecule between the cytotoxic/anti-viral drug and the cleavage site. This linker technology allows researchers to create ADCs with more flexibility without worrying about changing cleavage kinetics. Researchers are also developing a new method of peptide cleavage based on Edman degradation, a method of sequencing amino acids in a peptide. Future direction in the development of ADCs also include the development of site-specific conjugation (TDCs) to further improve stability and therapeutic index and a emitting immunoconjugates and antibody-conjugated nanoparticles.
H. BiTES
Bi-specific T-cell engagers (BiTEs) are a class of artificial bispecific monoclonal antibodies that are investigated for the use as anti-cancer drugs. They direct a host's immune system, more specifically the T cells' cytotoxic activity, against infected cells. BiTE is a registered trademark of Micromet AG.
BiTEs are fusion proteins consisting of two single-chain variable fragments (scFvs) of different antibodies, or amino acid sequences from four different genes, on a single peptide chain of about 55 kilodaltons. One of the scFvs binds to T cells via the CD3 receptor, and the other to an infected cell via a specific molecule.
Like other bispecific antibodies, and unlike ordinary monoclonal antibodies, BiTEs form a link between T cells and target cells. This causes T cells to exert cytotoxic/anti-viral activity on infected cells by producing proteins like perforin and granzymes, independently of the presence of MHC I or co-stimulatory molecules. These proteins enter infected cells and initiate the cell's apoptosis. This action mimics physiological processes observed during T cell attacks against infected cells.
I. Intrabodies
In a particular embodiment, the antibody is a recombinant antibody that is suitable for action inside of a cell—such antibodies are known as “intrabodies.” These antibodies may interfere with target function by a variety of mechanism, such as by altering intracellular protein trafficking, interfering with enzymatic function, and blocking protein-protein or protein-DNA interactions. In many ways, their structures mimic or parallel those of single chain and single domain antibodies, discussed above. Indeed, single-transcript/single-chain is an important feature that permits intracellular expression in a target cell, and also makes protein transit across cell membranes more feasible. However, additional features are required.
The two major issues impacting the implementation of intrabody therapeutic are delivery, including cell/tissue targeting, and stability. With respect to delivery, a variety of approaches have been employed, such as tissue-directed delivery, use of cell-type specific promoters, viral-based delivery and use of cell-permeability/membrane translocating peptides. With respect to the stability, the approach is generally to either screen by brute force, including methods that involve phage display and may include sequence maturation or development of consensus sequences, or more directed modifications such as insertion stabilizing sequences (e.g., Fc regions, chaperone protein sequences, leucine zippers) and disulfide replacement/modification.
An additional feature that intrabodies may require is a signal for intracellular targeting. Vectors that can target intrabodies (or other proteins) to subcellular regions such as the cytoplasm, nucleus, mitochondria and ER have been designed and are commercially available (Invitrogen Corp.; Persic et al., 1997).
By virtue of their ability to enter cells, intrabodies have additional uses that other types of antibodies may not achieve. In the case of the present antibodies, the ability to interact with the MUC1 cytoplasmic domain in a living cell may interfere with functions associated with the MUC1 CD, such as signaling functions (binding to other molecules) or oligomer formation. In particular, it is contemplated that such antibodies can be used to inhibit MUC1 dimer formation.
J. Purification
In certain embodiments, the antibodies of the present disclosure may be purified. The term “purified,” as used herein, is intended to refer to a composition, isolatable from other components, wherein the protein is purified to any degree relative to its naturally-obtainable state. A purified protein therefore also refers to a protein, free from the environment in which it may naturally occur. Where the term “substantially purified” is used, this designation will refer to a composition in which the protein or peptide forms the major component of the composition, such as constituting about 50%, about 60%, about 70%, about 80%, about 90%, about 95% or more of the proteins in the composition.
Protein purification techniques are well known to those of skill in the art. These techniques involve, at one level, the crude fractionation of the cellular milieu to polypeptide and non-polypeptide fractions. Having separated the polypeptide from other proteins, the polypeptide of interest may be further purified using chromatographic and electrophoretic techniques to achieve partial or complete purification (or purification to homogeneity). Analytical methods particularly suited to the preparation of a pure peptide are ion-exchange chromatography, exclusion chromatography; polyacrylamide gel electrophoresis; isoelectric focusing. Other methods for protein purification include, precipitation with ammonium sulfate, PEG, antibodies and the like or by heat denaturation, followed by centrifugation; gel filtration, reverse phase, hydroxylapatite and affinity chromatography; and combinations of such and other techniques.
In purifying an antibody of the present disclosure, it may be desirable to express the polypeptide in a prokaryotic or eukaryotic expression system and extract the protein using denaturing conditions. The polypeptide may be purified from other cellular components using an affinity column, which binds to a tagged portion of the polypeptide. As is generally known in the art, it is believed that the order of conducting the various purification steps may be changed, or that certain steps may be omitted, and still result in a suitable method for the preparation of a substantially purified protein or peptide.
Commonly, complete antibodies are fractionated utilizing agents (i.e., protein A) that bind the Fc portion of the antibody. Alternatively, antigens may be used to simultaneously purify and select appropriate antibodies. Such methods often utilize the selection agent bound to a support, such as a column, filter or bead. The antibodies are bound to a support, contaminants removed (e.g., washed away), and the antibodies released by applying conditions (salt, heat, etc.).
Various methods for quantifying the degree of purification of the protein or peptide will be known to those of skill in the art in light of the present disclosure. These include, for example, determining the specific activity of an active fraction, or assessing the amount of polypeptides within a fraction by SDS/PAGE analysis. Another method for assessing the purity of a fraction is to calculate the specific activity of the fraction, to compare it to the specific activity of the initial extract, and to thus calculate the degree of purity. The actual units used to represent the amount of activity will, of course, be dependent upon the particular assay technique chosen to follow the purification and whether or not the expressed protein or peptide exhibits a detectable activity.
It is known that the migration of a polypeptide can vary, sometimes significantly, with different conditions of SDS/PAGE (Capaldi et al., 1977). It will therefore be appreciated that under differing electrophoresis conditions, the apparent molecular weights of purified or partially purified expression products may vary.
A. Formulation and Administration
The present disclosure provides pharmaceutical compositions comprising anti-alphavirus antibodies and antigens for generating the same. Such compositions comprise a prophylactically or therapeutically effective amount of an antibody or a fragment thereof, or a peptide immunogen, and a pharmaceutically acceptable carrier. In a specific embodiment, the term “pharmaceutically acceptable” means approved by a regulatory agency of the Federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in animals, and more particularly in humans. The term “carrier” refers to a diluent, excipient, or vehicle with which the therapeutic is administered. Such pharmaceutical carriers can be sterile liquids, such as water and oils, including those of petroleum, animal, vegetable or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil and the like. Water is a particular carrier when the pharmaceutical composition is administered intravenously. Saline solutions and aqueous dextrose and glycerol solutions can also be employed as liquid carriers, particularly for injectable solutions. Other suitable pharmaceutical excipients include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, sodium chloride, dried skim milk, glycerol, propylene, glycol, water, ethanol and the like.
The composition, if desired, can also contain minor amounts of wetting or emulsifying agents, or pH buffering agents. These compositions can take the form of solutions, suspensions, emulsion, tablets, pills, capsules, powders, sustained-release formulations and the like. Oral formulations can include standard carriers such as pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharine, cellulose, magnesium carbonate, etc. Examples of suitable pharmaceutical agents are described in “Remington's Pharmaceutical Sciences.” Such compositions will contain a prophylactically or therapeutically effective amount of the antibody or fragment thereof, preferably in purified form, together with a suitable amount of carrier so as to provide the form for proper administration to the patient. The formulation should suit the mode of administration, which can be oral, intravenous, intraarterial, intrabuccal, intranasal, nebulized, bronchial inhalation, intra-rectal, vaginal, topical or delivered by mechanical ventilation.
Active vaccines are also envisioned where antibodies like those disclosed are produced in vivo in a subject at risk of alphavirus infection. Such vaccines can be formulated for parenteral administration, e.g., formulated for injection via the intradermal, intravenous, intramuscular, subcutaneous, or even intraperitoneal routes Administration by intradermal and intramuscular routes are contemplated. The vaccine could alternatively be administered by a topical route directly to the mucosa, for example by nasal drops, inhalation, by nebulizer, or via intrarectal or vaginal delivery. Pharmaceutically acceptable salts include the acid salts and those which are formed with inorganic acids such as, for example, hydrochloric or phosphoric acids, or such organic acids as acetic, oxalic, tartaric, mandelic, and the like. Salts formed with the free carboxyl groups may also be derived from inorganic bases such as, for example, sodium, potassium, ammonium, calcium, or ferric hydroxides, and such organic bases as isopropylamine, trimethylamine, 2-ethylamino ethanol, histidine, procaine, and the like.
Passive transfer of antibodies, known as artificially acquired passive immunity, generally will involve the use of intravenous or intramuscular injections. The forms of antibody can be human or animal blood plasma or serum, as pooled human immunoglobulin for intravenous (IVIG) or intramuscular (IG) use, as high-titer human IVIG or IG from immunized or from donors recovering from disease, and as monoclonal antibodies (MAb). Such immunity generally lasts for only a short period of time, and there is also a potential risk for hypersensitivity reactions, and serum sickness, especially from gamma globulin of non-human origin. However, passive immunity provides immediate protection. The antibodies will be formulated in a carrier suitable for injection, i.e., sterile and syringeable.
Generally, the ingredients of compositions of the disclosure are supplied either separately or mixed together in unit dosage form, for example, as a dry lyophilized powder or water-free concentrate in a hermetically sealed container such as an ampoule or sachette indicating the quantity of active agent. Where the composition is to be administered by infusion, it can be dispensed with an infusion bottle containing sterile pharmaceutical grade water or saline. Where the composition is administered by injection, an ampoule of sterile water for injection or saline can be provided so that the ingredients may be mixed prior to administration.
The compositions of the disclosure can be formulated as neutral or salt forms. Pharmaceutically acceptable salts include those formed with anions such as those derived from hydrochloric, phosphoric, acetic, oxalic, tartaric acids, etc., and those formed with cations such as those derived from sodium, potassium, ammonium, calcium, ferric hydroxides, isopropylamine, triethylamine, 2-ethylamino ethanol, histidine, procaine, etc.
2. ADCC
Antibody-dependent cell-mediated cytotoxicity (ADCC) is an immune mechanism leading to the lysis of antibody-coated target cells by immune effector cells. The target cells are cells to which antibodies or fragments thereof comprising an Fc region specifically bind, generally via the protein part that is N-terminal to the Fc region. By “antibody having increased/reduced antibody dependent cell-mediated cytotoxicity (ADCC)” is meant an antibody having increased/reduced ADCC as determined by any suitable method known to those of ordinary skill in the art.
As used herein, the term “increased/reduced ADCC” is defined as either an increase/reduction in the number of target cells that are lysed in a given time, at a given concentration of antibody in the medium surrounding the target cells, by the mechanism of ADCC defined above, and/or a reduction/increase in the concentration of antibody, in the medium surrounding the target cells, required to achieve the lysis of a given number of target cells in a given time, by the mechanism of ADCC. The increase/reduction in ADCC is relative to the ADCC mediated by the same antibody produced by the same type of host cells, using the same standard production, purification, formulation and storage methods (which are known to those skilled in the art), but that has not been engineered. For example, the increase in ADCC mediated by an antibody produced by host cells engineered to have an altered pattern of glycosylation (e.g., to express the glycosyltransferase, GnTIII, or other glycosyltransferases) by the methods described herein, is relative to the ADCC mediated by the same antibody produced by the same type of non-engineered host cells.
3. CDC
Complement-dependent cytotoxicity (CDC) is a function of the complement system. It is the processes in the immune system that kill pathogens by damaging their membranes without the involvement of antibodies or cells of the immune system. There are three main processes. All three insert one or more membrane attack complexes (MAC) into the pathogen which cause lethal colloid-osmotic swelling, i.e., CDC. It is one of the mechanisms by which antibodies or antibody fragments have an anti-viral effect.
Antibodies of the present disclosure may be linked to at least one agent to form an antibody conjugate. In order to increase the efficacy of antibody molecules as diagnostic or therapeutic agents, it is conventional to link or covalently bind or complex at least one desired molecule or moiety. Such a molecule or moiety may be, but is not limited to, at least one effector or reporter molecule. Effector molecules comprise molecules having a desired activity, e.g., cytotoxic activity. Non-limiting examples of effector molecules which have been attached to antibodies include toxins, anti-tumor agents, therapeutic enzymes, radionuclides, antiviral agents, chelating agents, cytokines, growth factors, and oligo- or polynucleotides. By contrast, a reporter molecule is defined as any moiety which may be detected using an assay. Non-limiting examples of reporter molecules which have been conjugated to antibodies include enzymes, radiolabels, haptens, fluorescent labels, phosphorescent molecules, chemiluminescent molecules, chromophores, photoaffinity molecules, colored particles or ligands, such as biotin.
Antibody conjugates are generally preferred for use as diagnostic agents. Antibody diagnostics generally fall within two classes, those for use in in vitro diagnostics, such as in a variety of immunoassays, and those for use in vivo diagnostic protocols, generally known as “antibody-directed imaging.” Many appropriate imaging agents are known in the art, as are methods for their attachment to antibodies (see, for e.g., U.S. Pat. Nos. 5,021,236, 4,938,948, and 4,472,509). The imaging moieties used can be paramagnetic ions, radioactive isotopes, fluorochromes, NMR-detectable substances, and X-ray imaging agents.
In the case of paramagnetic ions, one might mention by way of example ions such as chromium (III), manganese (II), iron (III), iron (II), cobalt (II), nickel (II), copper (II), neodymium (III), samarium (III), ytterbium (III), gadolinium (III), vanadium (II), terbium (III), dysprosium (III), holmium (III) and/or erbium (III), with gadolinium being particularly preferred. Ions useful in other contexts, such as X-ray imaging, include but are not limited to lanthanum (III), gold (III), lead (II), and especially bismuth (III).
In the case of radioactive isotopes for therapeutic and/or diagnostic application, one might mention astatine211, 14carbon, 51chromium, 36chlorine, 57cobalt, 58cobalt, copper67, 152Eu, gallium67, 3hydrogen, iodine123, iodine125, iodine131, indium111, 59iron, 32phosphorus, rhenium186, rhenium188, 75selenium, 35sulphur, technicium99m and/or yttrium99. 125I is often being preferred for use in certain embodiments, and technicium99m and/or indium111 are also often preferred due to their low energy and suitability for long range detection. Radioactively labeled monoclonal antibodies of the present disclosure may be produced according to well-known methods in the art. For instance, monoclonal antibodies can be iodinated by contact with sodium and/or potassium iodide and a chemical oxidizing agent such as sodium hypochlorite, or an enzymatic oxidizing agent, such as lactoperoxidase. Monoclonal antibodies according to the disclosure may be labeled with technetium99m by ligand exchange process, for example, by reducing pertechnate with stannous solution, chelating the reduced technetium onto a Sephadex column and applying the antibody to this column. Alternatively, direct labeling techniques may be used, e.g., by incubating pertechnate, a reducing agent such as SNCl2, a buffer solution such as sodium-potassium phthalate solution, and the antibody. Intermediary functional groups which are often used to bind radioisotopes which exist as metallic ions to antibody are diethylenetriaminepentaacetic acid (DTPA) or ethylene diaminetetracetic acid (EDTA).
Among the fluorescent labels contemplated for use as conjugates include Alexa 350, Alexa 430, AMCA, BODIPY 630/650, BODIPY 650/665, BODIPY-FL, BODIPY-R6G, BODIPY-TMR, BODIPY-TRX, Cascade Blue, Cy3, Cy5,6-FAM, Fluorescein Isothiocyanate, HEX, 6-JOE, Oregon Green 488, Oregon Green 500, Oregon Green 514, Pacific Blue, REG, Rhodamine Green, Rhodamine Red, Renographin, ROX, TAMRA, TET, Tetramethylrhodamine, and/or Texas Red.
Additional types of antibodies contemplated in the present disclosure are those intended primarily for use in vitro, where the antibody is linked to a secondary binding ligand and/or to an enzyme (an enzyme tag) that will generate a colored product upon contact with a chromogenic substrate. Examples of suitable enzymes include urease, alkaline phosphatase, (horseradish) hydrogen peroxidase or glucose oxidase. Preferred secondary binding ligands are biotin and avidin and streptavidin compounds. The use of such labels is well known to those of skill in the art and are described, for example, in U.S. Pat. Nos. 3,817,837, 3,850,752, 3,939,350, 3,996,345, 4,277,437, 4,275,149 and 4,366,241.
Yet another known method of site-specific attachment of molecules to antibodies comprises the reaction of antibodies with hapten-based affinity labels. Essentially, hapten-based affinity labels react with amino acids in the antigen binding site, thereby destroying this site and blocking specific antigen reaction. However, this may not be advantageous since it results in loss of antigen binding by the antibody conjugate.
Molecules containing azido groups may also be used to form covalent bonds to proteins through reactive nitrene intermediates that are generated by low intensity ultraviolet light (Potter and Haley, 1983). In particular, 2- and 8-azido analogues of purine nucleotides have been used as site-directed photoprobes to identify nucleotide binding proteins in crude cell extracts (Owens & Haley, 1987; Atherton et al., 1985). The 2- and 8-azido nucleotides have also been used to map nucleotide binding domains of purified proteins (Khatoon et al., 1989; King et al., 1989; Dholakia et al., 1989) and may be used as antibody binding agents.
Several methods are known in the art for the attachment or conjugation of an antibody to its conjugate moiety. Some attachment methods involve the use of a metal chelate complex employing, for example, an organic chelating agent such a diethylenetriaminepentaacetic acid anhydride (DTPA); ethylenetriaminetetraacetic acid; N-chloro-p-toluenesulfonamide; and/or tetrachloro-3α-6α-diphenylglycouril-3 attached to the antibody (U.S. Pat. Nos. 4,472,509 and 4,938,948). Monoclonal antibodies may also be reacted with an enzyme in the presence of a coupling agent such as glutaraldehyde or periodate. Conjugates with fluorescein markers are prepared in the presence of these coupling agents or by reaction with an isothiocyanate. In U.S. Pat. No. 4,938,948, imaging of breast tumors is achieved using monoclonal antibodies and the detectable imaging moieties are bound to the antibody using linkers such as methyl-p-hydroxybenzimidate or N-succinimidyl-3-(4-hydroxyphenyl)propionate.
In other embodiments, derivatization of immunoglobulins by selectively introducing sulfhydryl groups in the Fc region of an immunoglobulin, using reaction conditions that do not alter the antibody combining site are contemplated. Antibody conjugates produced according to this methodology are disclosed to exhibit improved longevity, specificity and sensitivity (U.S. Pat. No. 5,196,066, incorporated herein by reference). Site-specific attachment of effector or reporter molecules, wherein the reporter or effector molecule is conjugated to a carbohydrate residue in the Fc region have also been disclosed in the literature (O'Shannessy et al., 1987). This approach has been reported to produce diagnostically and therapeutically promising antibodies which are currently in clinical evaluation.
In still further embodiments, the present disclosure concerns immunodetection methods for binding, purifying, removing, quantifying and otherwise generally detecting alphavirus and its associated antigens. While such methods can be applied in a traditional sense, another use will be in quality control and monitoring of vaccine and other virus stocks, where antibodies according to the present disclosure can be used to assess the amount or integrity (i.e., long term stability) of antigens in viruses. Alternatively, the methods may be used to screen various antibodies for appropriate/desired reactivity profiles.
Other immunodetection methods include specific assays for determining the presence of alphavirus in a subject. A wide variety of assay formats are contemplated, but specifically those that would be used to detect alphavirus in a fluid obtained from a subject, such as saliva, blood, plasma, sputum, semen or urine. In particular, semen has been demonstrated as a viable sample for detecting alphavirus (Purpura et al., 2016; Mansuy et al., 2016; Barzon et al., 2016; Gornet et al., 2016; Duffy et al., 2009; CDC, 2016; Halfon et al., 2010; Elder et al. 2005). The assays may be advantageously formatted for non-healthcare (home) use, including lateral flow assays (see below) analogous to home pregnancy tests. These assays may be packaged in the form of a kit with appropriate reagents and instructions to permit use by the subject of a family member.
Some immunodetection methods include enzyme linked immunosorbent assay (ELISA), radioimmunoassay (RIA), immunoradiometric assay, fluoroimmunoassay, chemiluminescent assay, bioluminescent assay, and Western blot to mention a few. In particular, a competitive assay for the detection and quantitation of alphavirus antibodies directed to specific parasite epitopes in samples also is provided. The steps of various useful immunodetection methods have been described in the scientific literature, such as, e.g., Doolittle and Ben-Zeev (1999), Gulbis and Galand (1993), De Jager et al. (1993), and Nakamura et al. (1987). In general, the immunobinding methods include obtaining a sample suspected of containing alphavirus and contacting the sample with a first antibody in accordance with the present disclosure, as the case may be, under conditions effective to allow the formation of immunocomplexes.
These methods include methods for purifying alphavirus or related antigens from a sample. The antibody will preferably be linked to a solid support, such as in the form of a column matrix, and the sample suspected of containing the alphavirus or antigenic component will be applied to the immobilized antibody. The unwanted components will be washed from the column, leaving the alphavirus antigen immunocomplexed to the immobilized antibody, which is then collected by removing the organism or antigen from the column.
The immunobinding methods also include methods for detecting and quantifying the amount of alphavirus or related components in a sample and the detection and quantification of any immune complexes formed during the binding process. Here, one would obtain a sample suspected of containing alphavirus or its antigens and contact the sample with an antibody that binds alphavirus or components thereof, followed by detecting and quantifying the amount of immune complexes formed under the specific conditions. In terms of antigen detection, the biological sample analyzed may be any sample that is suspected of containing alphavirus or alphavirus antigen, such as a tissue section or specimen, a homogenized tissue extract, a biological fluid, including blood and serum, or a secretion, such as feces or urine.
Contacting the chosen biological sample with the antibody under effective conditions and for a period of time sufficient to allow the formation of immune complexes (primary immune complexes) is generally a matter of simply adding the antibody composition to the sample and incubating the mixture for a period of time long enough for the antibodies to form immune complexes with, i.e., to bind to alphavirus or alphavirus antigens present. After this time, the sample-antibody composition, such as a tissue section, ELISA plate, dot blot or Western blot, will generally be washed to remove any non-specifically bound antibody species, allowing only those antibodies specifically bound within the primary immune complexes to be detected.
In general, the detection of immunocomplex formation is well known in the art and may be achieved through the application of numerous approaches. These methods are generally based upon the detection of a label or marker, such as any of those radioactive, fluorescent, biological and enzymatic tags. Patents concerning the use of such labels include U.S. Pat. Nos. 3,817,837, 3,850,752, 3,939,350, 3,996,345, 4,277,437, 4,275,149 and 4,366,241. Of course, one may find additional advantages through the use of a secondary binding ligand such as a second antibody and/or a biotin/avidin ligand binding arrangement, as is known in the art.
The antibody employed in the detection may itself be linked to a detectable label, wherein one would then simply detect this label, thereby allowing the amount of the primary immune complexes in the composition to be determined. Alternatively, the first antibody that becomes bound within the primary immune complexes may be detected by means of a second binding ligand that has binding affinity for the antibody. In these cases, the second binding ligand may be linked to a detectable label. The second binding ligand is itself often an antibody, which may thus be termed a “secondary” antibody. The primary immune complexes are contacted with the labeled, secondary binding ligand, or antibody, under effective conditions and for a period of time sufficient to allow the formation of secondary immune complexes. The secondary immune complexes are then generally washed to remove any non-specifically bound labeled secondary antibodies or ligands, and the remaining label in the secondary immune complexes is then detected.
Further methods include the detection of primary immune complexes by a two-step approach. A second binding ligand, such as an antibody that has binding affinity for the antibody, is used to form secondary immune complexes, as described above. After washing, the secondary immune complexes are contacted with a third binding ligand or antibody that has binding affinity for the second antibody, again under effective conditions and for a period of time sufficient to allow the formation of immune complexes (tertiary immune complexes). The third ligand or antibody is linked to a detectable label, allowing detection of the tertiary immune complexes thus formed. This system may provide for signal amplification if this is desired.
One method of immunodetection uses two different antibodies. A first biotinylated antibody is used to detect the target antigen, and a second antibody is then used to detect the biotin attached to the complexed biotin. In that method, the sample to be tested is first incubated in a solution containing the first step antibody. If the target antigen is present, some of the antibody binds to the antigen to form a biotinylated antibody/antigen complex. The antibody/antigen complex is then amplified by incubation in successive solutions of streptavidin (or avidin), biotinylated DNA, and/or complementary biotinylated DNA, with each step adding additional biotin sites to the antibody/antigen complex. The amplification steps are repeated until a suitable level of amplification is achieved, at which point the sample is incubated in a solution containing the second step antibody against biotin. This second step antibody is labeled, as for example with an enzyme that can be used to detect the presence of the antibody/antigen complex by histo-enzymology using a chromogen substrate. With suitable amplification, a conjugate can be produced which is macroscopically visible.
Another known method of immunodetection takes advantage of the immuno-PCR (Polymerase Chain Reaction) methodology. The PCR method is similar to the Cantor method up to the incubation with biotinylated DNA, however, instead of using multiple rounds of streptavidin and biotinylated DNA incubation, the DNA/biotin/streptavidin/antibody complex is washed out with a low pH or high salt buffer that releases the antibody. The resulting wash solution is then used to carry out a PCR reaction with suitable primers with appropriate controls. At least in theory, the enormous amplification capability and specificity of PCR can be utilized to detect a single antigen molecule.
A. ELISAs
Immunoassays, in their most simple and direct sense, are binding assays. Certain preferred immunoassays are the various types of enzyme linked immunosorbent assays (ELISAs) and radioimmunoassays (RIA) known in the art Immunohistochemical detection using tissue sections is also particularly useful. However, it will be readily appreciated that detection is not limited to such techniques, and western blotting, dot blotting, FACS analyses, and the like may also be used.
In one exemplary ELISA, the antibodies of the disclosure are immobilized onto a selected surface exhibiting protein affinity, such as a well in a polystyrene microtiter plate. Then, a test composition suspected of containing the alphavirus or alphavirus antigen is added to the wells. After binding and washing to remove non-specifically bound immune complexes, the bound antigen may be detected. Detection may be achieved by the addition of another anti-alphavirus antibody that is linked to a detectable label. This type of ELISA is a simple “sandwich ELISA.” Detection may also be achieved by the addition of a second anti-alphavirus antibody, followed by the addition of a third antibody that has binding affinity for the second antibody, with the third antibody being linked to a detectable label.
In another exemplary ELISA, the samples suspected of containing the alphavirus or alphavirus antigen are immobilized onto the well surface and then contacted with the anti-alphavirus antibodies of the disclosure. After binding and washing to remove non-specifically bound immune complexes, the bound anti-alphavirus antibodies are detected. Where the initial anti-alphavirus antibodies are linked to a detectable label, the immune complexes may be detected directly. Again, the immune complexes may be detected using a second antibody that has binding affinity for the first anti-alphavirus antibody, with the second antibody being linked to a detectable label.
Irrespective of the format employed, ELISAs have certain features in common, such as coating, incubating and binding, washing to remove non-specifically bound species, and detecting the bound immune complexes. These are described below.
In coating a plate with either antigen or antibody, one will generally incubate the wells of the plate with a solution of the antigen or antibody, either overnight or for a specified period of hours. The wells of the plate will then be washed to remove incompletely adsorbed material. Any remaining available surfaces of the wells are then “coated” with a nonspecific protein that is antigenically neutral with regard to the test antisera. These include bovine serum albumin (BSA), casein or solutions of milk powder. The coating allows for blocking of nonspecific adsorption sites on the immobilizing surface and thus reduces the background caused by nonspecific binding of antisera onto the surface.
In ELISAs, it is probably more customary to use a secondary or tertiary detection means rather than a direct procedure. Thus, after binding of a protein or antibody to the well, coating with a non-reactive material to reduce background, and washing to remove unbound material, the immobilizing surface is contacted with the biological sample to be tested under conditions effective to allow immune complex (antigen/antibody) formation. Detection of the immune complex then requires a labeled secondary binding ligand or antibody, and a secondary binding ligand or antibody in conjunction with a labeled tertiary antibody or a third binding ligand.
“Under conditions effective to allow immune complex (antigen/antibody) formation” means that the conditions preferably include diluting the antigens and/or antibodies with solutions such as BSA, bovine gamma globulin (BGG) or phosphate buffered saline (PBS)/Tween. These added agents also tend to assist in the reduction of nonspecific background.
The “suitable” conditions also mean that the incubation is at a temperature or for a period of time sufficient to allow effective binding. Incubation steps are typically from about 1 to 2 to 4 hours or so, at temperatures preferably on the order of 25° C. to 27° C. or may be overnight at about 4° C. or so.
Following all incubation steps in an ELISA, the contacted surface is washed so as to remove non-complexed material. A preferred washing procedure includes washing with a solution such as PBS/Tween, or borate buffer. Following the formation of specific immune complexes between the test sample and the originally bound material, and subsequent washing, the occurrence of even minute amounts of immune complexes may be determined.
To provide a detecting means, the second or third antibody will have an associated label to allow detection. Preferably, this will be an enzyme that will generate color development upon incubating with an appropriate chromogenic substrate. Thus, for example, one will desire to contact or incubate the first and second immune complex with a urease, glucose oxidase, alkaline phosphatase or hydrogen peroxidase-conjugated antibody for a period of time and under conditions that favor the development of further immune complex formation (e.g., incubation for 2 hours at room temperature in a PBS-containing solution such as PBS-Tween).
After incubation with the labeled antibody, and subsequent to washing to remove unbound material, the amount of label is quantified, e.g., by incubation with a chromogenic substrate such as urea, or bromocresol purple, or 2,2′-azino-di-(3-ethyl-benzthiazoline-6-sulfonic acid (ABTS), or H2O2, in the case of peroxidase as the enzyme label. Quantification is then achieved by measuring the degree of color generated, e.g., using a visible spectra spectrophotometer.
In another embodiment, the present disclosure contemplates the use of competitive formats. This is particularly useful in the detection of alphavirus antibodies in sample. In competition-based assays, an unknown amount of analyte or antibody is determined by its ability to displace a known amount of labeled antibody or analyte. Thus, the quantifiable loss of a signal is an indication of the amount of unknown antibody or analyte in a sample.
Here, the inventor proposes the use of labeled alphavirus monoclonal antibodies to determine the amount of alphavirus antibodies in a sample. The basic format would include contacting a known amount of alphavirus monoclonal antibody (linked to a detectable label) with alphavirus antigen or particle. The alphavirus antigen or organism is preferably attached to a support. After binding of the labeled monoclonal antibody to the support, the sample is added and incubated under conditions permitting any unlabeled antibody in the sample to compete with, and hence displace, the labeled monoclonal antibody. By measuring either the lost label or the label remaining (and subtracting that from the original amount of bound label), one can determine how much non-labeled antibody is bound to the support, and thus how much antibody was present in the sample.
B. Western Blot
The Western blot (alternatively, protein immunoblot) is an analytical technique used to detect specific proteins in a given sample of tissue homogenate or extract. It uses gel electrophoresis to separate native or denatured proteins by the length of the polypeptide (denaturing conditions) or by the 3-D structure of the protein (native/non-denaturing conditions). The proteins are then transferred to a membrane (typically nitrocellulose or PVDF), where they are probed (detected) using antibodies specific to the target protein.
Samples may be taken from whole tissue or from cell culture. In most cases, solid tissues are first broken down mechanically using a blender (for larger sample volumes), using a homogenizer (smaller volumes), or by sonication. Cells may also be broken open by one of the above mechanical methods. However, it should be noted that bacteria, virus or environmental samples can be the source of protein and thus Western blotting is not restricted to cellular studies only. Assorted detergents, salts, and buffers may be employed to encourage lysis of cells and to solubilize proteins. Protease and phosphatase inhibitors are often added to prevent the digestion of the sample by its own enzymes. Tissue preparation is often done at cold temperatures to avoid protein denaturing.
The proteins of the sample are separated using gel electrophoresis. Separation of proteins may be by isoelectric point (pI), molecular weight, electric charge, or a combination of these factors. The nature of the separation depends on the treatment of the sample and the nature of the gel. This is a very useful way to determine a protein. It is also possible to use a two-dimensional (2-D) gel which spreads the proteins from a single sample out in two dimensions. Proteins are separated according to isoelectric point (pH at which they have neutral net charge) in the first dimension, and according to their molecular weight in the second dimension.
In order to make the proteins accessible to antibody detection, they are moved from within the gel onto a membrane made of nitrocellulose or polyvinylidene difluoride (PVDF). The membrane is placed on top of the gel, and a stack of filter papers placed on top of that. The entire stack is placed in a buffer solution which moves up the paper by capillary action, bringing the proteins with it. Another method for transferring the proteins is called electroblotting and uses an electric current to pull proteins from the gel into the PVDF or nitrocellulose membrane. The proteins move from within the gel onto the membrane while maintaining the organization they had within the gel. As a result of this blotting process, the proteins are exposed on a thin surface layer for detection (see below). Both varieties of membrane are chosen for their non-specific protein binding properties (i.e., binds all proteins equally well). Protein binding is based upon hydrophobic interactions, as well as charged interactions between the membrane and protein. Nitrocellulose membranes are cheaper than PVDF but are far more fragile and do not stand up well to repeated probings. The uniformity and overall effectiveness of transfer of protein from the gel to the membrane can be checked by staining the membrane with Coomassie Brilliant Blue or Ponceau S dyes. Once transferred, proteins are detected using labeled primary antibodies, or unlabeled primary antibodies followed by indirect detection using labeled protein A or secondary labeled antibodies binding to the Fc region of the primary antibodies.
C. Lateral Flow Assays
Lateral flow assays, also known as lateral flow immunochromatographic assays, are simple devices intended to detect the presence (or absence) of a target analyte in sample (matrix) without the need for specialized and costly equipment, though many laboratory-based applications exist that are supported by reading equipment. Typically, these tests are used as low resources medical diagnostics, either for home testing, point of care testing, or laboratory use. A widely spread and well-known application is the home pregnancy test.
The technology is based on a series of capillary beds, such as pieces of porous paper or sintered polymer. Each of these elements has the capacity to transport fluid (e.g., urine) spontaneously. The first element (the sample pad) acts as a sponge and holds an excess of sample fluid. Once soaked, the fluid migrates to the second element (conjugate pad) in which the manufacturer has stored the so-called conjugate, a dried format of bio-active particles (see below) in a salt-sugar matrix that contains everything to guarantee an optimized chemical reaction between the target molecule (e.g., an antigen) and its chemical partner (e.g., antibody) that has been immobilized on the particle's surface. While the sample fluid dissolves the salt-sugar matrix, it also dissolves the particles and in one combined transport action the sample and conjugate mix while flowing through the porous structure. In this way, the analyte binds to the particles while migrating further through the third capillary bed. This material has one or more areas (often called stripes) where a third molecule has been immobilized by the manufacturer. By the time the sample-conjugate mix reaches these strips, analyte has been bound on the particle and the third ‘capture’ molecule binds the complex. After a while, when more and more fluid has passed the stripes, particles accumulate and the stripe-area changes color. Typically, there are at least two stripes: one (the control) that captures any particle and thereby shows that reaction conditions and technology worked fine, the second contains a specific capture molecule and only captures those particles onto which an analyte molecule has been immobilized. After passing these reaction zones, the fluid enters the final porous material—the wick—that simply acts as a waste container. Lateral Flow Tests can operate as either competitive or sandwich assays. Lateral flow assays are disclosed in U.S. Pat. No. 6,485,982.
D. Immunohistochemistry
The antibodies of the present disclosure may also be used in conjunction with both fresh-frozen and/or formalin-fixed, paraffin-embedded tissue blocks prepared for study by immunohistochemistry (IHC). The method of preparing tissue blocks from these particulate specimens has been successfully used in previous IHC studies of various prognostic factors and is well known to those of skill in the art (Brown et al., 1990; Abbondanzo et al., 1990; Allred et al., 1990).
Briefly, frozen-sections may be prepared by rehydrating 50 ng of frozen “pulverized” tissue at room temperature in phosphate buffered saline (PBS) in small plastic capsules; pelleting the particles by centrifugation; resuspending them in a viscous embedding medium (OCT); inverting the capsule and/or pelleting again by centrifugation; snap-freezing in −70° C. isopentane; cutting the plastic capsule and/or removing the frozen cylinder of tissue; securing the tissue cylinder on a cryostat microtome chuck; and/or cutting 25-50 serial sections from the capsule. Alternatively, whole frozen tissue samples may be used for serial section cuttings.
Permanent-sections may be prepared by a similar method involving rehydration of the 50 mg sample in a plastic microfuge tube; pelleting; resuspending in 10% formalin for 4 hours fixation; washing/pelleting; resuspending in warm 2.5% agar; pelleting; cooling in ice water to harden the agar; removing the tissue/agar block from the tube; infiltrating and/or embedding the block in paraffin; and/or cutting up to 50 serial permanent sections. Again, whole tissue samples may be substituted.
E. Immunodetection Kits
In still further embodiments, the present disclosure concerns immunodetection kits for use with the immunodetection methods described above. As the antibodies may be used to detect alphavirus or alphavirus antigens, the antibodies may be included in the kit. The immunodetection kits will thus comprise, in suitable container means, a first antibody that binds to alphavirus or alphavirus antigen, and optionally an immunodetection reagent.
In certain embodiments, the alphavirus antibody may be pre-bound to a solid support, such as a column matrix and/or well of a microtiter plate. The immunodetection reagents of the kit may take any one of a variety of forms, including those detectable labels that are associated with or linked to the given antibody. Detectable labels that are associated with or attached to a secondary binding ligand are also contemplated. Exemplary secondary ligands are those secondary antibodies that have binding affinity for the first antibody.
Further suitable immunodetection reagents for use in the present kits include the two-component reagent that comprises a secondary antibody that has binding affinity for the first antibody, along with a third antibody that has binding affinity for the second antibody, the third antibody being linked to a detectable label. As noted above, a number of exemplary labels are known in the art and all such labels may be employed in connection with the present disclosure.
The kits may further comprise a suitably aliquoted composition of the alphavirus or alphavirus antigens, whether labeled or unlabeled, as may be used to prepare a standard curve for a detection assay. The kits may contain antibody-label conjugates either in fully conjugated form, in the form of intermediates, or as separate moieties to be conjugated by the user of the kit. The components of the kits may be packaged either in aqueous media or in lyophilized form.
The container means of the kits will generally include at least one vial, test tube, flask, bottle, syringe or other container means, into which the antibody may be placed, or preferably, suitably aliquoted. The kits of the present disclosure will also typically include a means for containing the antibody, antigen, and any other reagent containers in close confinement for commercial sale. Such containers may include injection or blow-molded plastic containers into which the desired vials are retained.
F. Vaccine and Antigen Quality Control Assays
The present disclosure also contemplates the use of antibodies and antibody fragments as described herein for use in assessing the antigenic integrity of a viral antigen in a sample. Biological medicinal products like vaccines differ from chemical drugs in that they cannot normally be characterized molecularly; antibodies are large molecules of significant complexity and have the capacity to vary widely from preparation to preparation. They are also administered to healthy individuals, including children at the start of their lives, and thus a strong emphasis must be placed on their quality to ensure, to the greatest extent possible, that they are efficacious in preventing or treating life-threatening disease, without themselves causing harm.
The increasing globalization in the production and distribution of vaccines has opened new possibilities to better manage public health concerns but has also raised questions about the equivalence and interchangeability of vaccines procured across a variety of sources. International standardization of starting materials, of production and quality control testing, and the setting of high expectations for regulatory oversight on the way these products are manufactured and used, have thus been the cornerstone for continued success. But it remains a field in constant change, and continuous technical advances in the field offer a promise of developing potent new weapons against the oldest public health threats, as well as new ones—malaria, pandemic influenza, and HIV, to name a few—but also put a great pressure on manufacturers, regulatory authorities, and the wider medical community to ensure that products continue to meet the highest standards of quality attainable.
Thus, one may obtain an antigen or vaccine from any source or at any point during a manufacturing process. The quality control processes may therefore begin with preparing a sample for an immunoassay that identifies binding of an antibody or fragment disclosed herein to a viral antigen. Such immunoassays are disclosed elsewhere in this document, and any of these may be used to assess the structural/antigenic integrity of the antigen. Standards for finding the sample to contain acceptable amounts of antigenically correct and intact antigen may be established by regulatory agencies.
Another important embodiment where antigen integrity is assessed is in determining shelf-life and storage stability. Most medicines, including vaccines, can deteriorate over time. Therefore, it is critical to determine whether, over time, the degree to which an antigen, such as in a vaccine, degrades or destabilizes such that is it no longer antigenic and/or capable of generating an immune response when administered to a subject. Again, standards for finding the sample to contain acceptable amounts of antigenically intact antigen may be established by regulatory agencies.
In certain embodiments, viral antigens may contain more than one protective epitope. In these cases, it may prove useful to employ assays that look at the binding of more than one antibody, such as 2, 3, 4, 5 or even more antibodies. These antibodies bind to closely related epitopes, such that they are adjacent or even overlap each other. On the other hand, they may represent distinct epitopes from disparate parts of the antigen. By examining the integrity of multiple epitopes, a more complete picture of the antigen's overall integrity, and hence ability to generate a protective immune response, may be determined.
Antibodies and fragments thereof as described in the present disclosure may also be used in a kit for monitoring the efficacy of vaccination procedures by detecting the presence of protective alphavirus antibodies. Antibodies, antibody fragment, or variants and derivatives thereof, as described in the present disclosure may also be used in a kit for monitoring vaccine manufacture with the desired immunogenicity.
The following examples are included to demonstrate preferred embodiments. It should be appreciated by those of skill in the art that the techniques disclosed in the examples that follow represent techniques discovered by the inventor to function well in the practice of embodiments, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the disclosure.
Analysis of donor serum reactivity and neutralization activity to EEEV. To select donors for isolation of human mAbs, the inventors tested 13 donors for serum reactivity and neutralization activity to SINV/EEEV and recombinant EEEV structural proteins. From binding and neutralization assays, they observed interesting trends in response that were dependent on previous donor history. Donors with the greatest serum reactivity and neutralization activity to EEEV were those that survived natural infection and had endpoint titers of at least >1:4,096 (
Analysis of donor serum reactivity to recombinant EEEV, VEEV, and WEEV virus-like particles (VLPs). To further characterize donor serum, the inventors determined donor serum reactivity to recombinant EEEV, VEEV, and WEEV VLPs. A similar trend based off of previous donor infection or vaccination history was observed for serum reactivity to the VLPs as was observed to SINV/EEEV and recombinant EEEV structural proteins. As expected, serum from donors that survived natural infection reacted primarily with EEEV VLPs (
Identification of human B-cell responses to the encephalitic alphaviruses. To generate human mAbs, the inventors used an established human hybridoma technique developed in the lab (Smith and Crowe, 2015; Yu et al., 2008). Briefly, from blood samples provided by donors, peripheral blood mononuclear cells (PBMCs) are isolated and transformed with Epstein-Barr virus (EBV). This generates lymphoblastoid cell lines (LCLs), in which antibody is produced. Through screening of the supernatant taken from these LCLs via binding assays, such as ELISA or cell surface display, provides an indication of whether there is antibody reactive to the antigen of interest present. The frequency of memory B cell population within PBMCs is approximately 0.1-1%. By taking into account the number of PBMCs, average number of LCLs, and reactivity of the LCLs, a relative B-cell frequency can be calculated. From EBV-transformation of several donors either naturally infected with EEEV or vaccinated against all three of the encephalitic alphaviruses (SIP), the inventors can compare the relative B-cell frequencies, for each donor. In the case of the naturally infected EEEV survivor (Donor 1069), all three EBV transformations from the same donor were relatively consistent and a high relative B-cell frequency (average 0.94%) to SINV/EEEV and recombinant EEEV structural proteins was observed (
Current human hybridoma status of three EBV-transformed donors. To date, the inventors have EBV-transformed three donors for generation of human mAbs. Two of these donors were naturally infected with EEEV (Donors 982 and 1069) whereas one donor was vaccinated against all three encephalitic viruses as part of the SIP (Donor 1047). From Donor 1069, the inventors isolated 64 human mAbs. Of this panel, a majority of the human mAbs are reactive to recombinant EEEV E2 glycoprotein (x49), several are reactive to recombinant EEEV E1 glycoprotein (x10), and one is specific for a virus-dependent epitope (x1) (
Characterization of human EEEV-reactive mAbs isolated from a naturally infected EEEV survivor to SINV/EEEV and recombinant EEEV structural proteins. From a donor naturally infected with EEEV (Donor 1069), the inventors isolated the first human EEEV mAb panel. The 64 mAbs isolated were selected for based off of reactivity to SINV/EEEV and recombinant EEEV structural proteins (E2 and E1 glycoproteins) via ELISA. Further characterization of the human EEEV mAb panel, revealed that most of the human mAbs (x49) are reactive to the EEEV E2 glycoprotein (
Specific reactivity of four mAbs is yet to be determined. There is diverse binding affinity of human EEEV mAbs to SINV/EEEV and recombinant EEEV E2 and E1 glycoproteins with tight binders (<10 ng/mL half-maximal effective concentration (EC50) values) to weaker binders (<2 μg/mL EC50 values) as determined by ELISA (
Characterization of cross-reactive human EEEV mAbs. For isolation of the first human EEEV mAb panel, initial screening was based off of reactivity to SINV/EEEV and recombinant EEEV structural proteins. However, by further characterization, the inventors identified several human EEEV mAbs that cross-react with the other encephalitic alphaviruses, VEEV and WEEV, and the arthritogenic alphavirus, CHIKV (
Determination of neutralization activity of human EEEV-reactive mAbs to SINV/EEEV and EEEV. To determine the neutralization activity of human EEEV mAbs, the inventors performed FRNTs against SINV/EEEV. They found 15 human EEEV mAbs with neutralization activity against SINV/EEEV (
Small animal model studies to determine the prophylactic or therapeutic efficacy of EEEV-33 in vivo. The inventors initiated small animal model studies in collaboration with Dr. William Klimstra to assess the potential prophylactic and therapeutic activity for EEEV-33 in vivo. They found EEEV-33 to exhibit prophylactic (83%) and therapeutic (33%) activity in vivo when mice were given 100 μg of EEEV-33 i.p. 24 hours prior or after, respectively, in a stringent aerosol challenge model (
Small animal model studies to determine the prophylactic or therapeutic efficacy of EEEV-30 in vivo. As a non-neutralizing control human mAb for small animal model studies, EEEV-30 was found to possess prophylactic activity (50%) in an in vivo aerosol BSL-3 EEEV challenge model (
Characterization of the neutralization mechanism(s) of human neutralizing EEEV mAbs. Antibodies are able to neutralize viruses at multiple stages in the viral replication cycle from prevention of receptor attachment to viral egress (Klasse, 2014; Burton et al., 2002). Previous studies regarding the mechanism of neutralization for alphavirus antibodies suggest that through binding to the E2 glycoprotein inhibition of viral entry, fusion, or viral egress occurs (Sun et al., 2013; Porta et al., 2014; Fox et al., 2015; Long et al., 2015; Jin et al., 2015). To identify step(s) in the replication cycle in which human mAbs neutralize SINV/EEEV, the inventors sought to test different neutralization mechanistic assays. To assess inhibition of virus attachment and/or entry, they compared differences in neutralization activity of several human EEEV mAbs through pre- and post-attachment entry inhibition assays. In the pre-attachment entry inhibition assay, mAb and virus are mixed together and added to cells at 4° C. to allow for virus attachment but not entry. In the post-attachment entry inhibition assay, virus is added to cells at 4° C. followed by addition of the mAb. A shift to 37° C. for 15 minutes allows for the virus to enter the cell. Foci are stained to detect the presence of virus. Comparison between these two assays helps provide insight into whether the mAb is able to neutralize through prevention of receptor attachment and/or entry or whether the mAb neutralizes at a post-attachment step in the replication cycle. From initial characterization of several human neutralizing mAbs through these assays, it appears that most mAbs neutralize at a step post-attachment in the replication cycle (
Identification of human antigenic determinants on EEEV. The E2 glycoprotein consists of three domains: domain B at the apical surface, followed by domain A, which contains the putative receptor-binding site, and domain C that lies proximal to the viral membrane (Griffin, 2013; Voss et al., 2010). There are also three domains of the E1 glycoprotein: domain II at the apical end contains the fusion loop, followed by domain I, and domain III that lies proximal to the membrane-spanning region (Griffin, 2013; Voss et al., 2010). To epitopes recognized by human EEEV mAbs, the inventors performed competition-binding studies via biolayer interferometry. Binding of human EEEV mAbs in competition with murine EEEV mAbs with known epitopes provides an indication of which epitopes are recognized. For the human EEEV mAbs that recognize recombinant EEEV E2 glycoprotein, they observed several competition-binding groups (
To further determine the epitopes recognized by human EEEV mAbs, the inventors performed hydrogen-deuterium exchange mass spectrometry (HDX-MS). Through HDX-MS, differences in Fab bound versus unbound E2 glycoprotein can identify the residues in which the Fab binds. They determined that Fab7 binds to 242-257 and 271-281 residues on the E2 glycoprotein, which corresponds to domain B (
Structural studies of human EEEV mAbs in complex with SINV/EEEV and recombinant EEEV structural proteins. To determine the structural basis of neutralization by human EEEV mAbs, the inventors initiated structural studies through X-ray crystallography and electron microscopy (EM). Optimization of crystallization conditions for X-ray crystallography of E2-E1 heterodimer in complex with Fab molecules is ongoing. They initiated EM studies with Dr. Melanie Ohi for structural analyses of SINV/EEEV in complex with Fab molecules.
Isolation of human mAbs from SIP donors. To identify human mAbs that target conserved regions amongst the encephalitic alphaviruses, the inventors began isolation of human mAbs from donors immunized against EEEV, VEEV, and WEEV as part of the Special Immunizations Program (SIP). The primary focus of this work is on the cross-reactivity and potential cross-neutralization of these mAb for the identification of conserved targets of antibody recognition and neutralization towards the encephalitic alphaviruses. However, isolation of mAbs to date from a SIP donor (Donor 1047) were characterized as either EEEV (x5) or VEEV-specific (x1) (
Summary. The studies conducted over the past year address many questions in the field relating to the human antibody repertoire against the encephalitic alphaviruses, with primary focus on Eastern equine encephalitis virus (EEEV). The inventors isolated and characterized the first human EEEV mAb panel to elucidate the diverse reactivity and breadth of the human antibody repertoire to SINV/EEEV and recombinant EEEV structural proteins. They identified several antigenic determinants on the EEEV E2 glycoprotein and revealed neutralizing antigenic sites. They characterized several potently neutralizing, protective, and therapeutic human EEEV mAbs to BSL-2 SINV/EEEV and BSL-3 EEEV that will aid in the revelation of the molecular and structural basis of neutralization against EEEV. These studies reveal the first human pan-alphavirus mAbs that can aid in the identification of conserved targets of antibody recognition and neutralization towards the encephalitic alphaviruses for potential diagnostic, vaccine, and therapeutic development.
The inventors identified three donors with natural EEEV infection, two of which were seropositive to the chimeric virus Sindbis/Eastern equine encephalitis virus (SINV/EEEV) as determined through serum reactivity and neutralization. They identified 10 donors with vaccination against the encephalitic alphaviruses—EEEV, VEEV and/or WEEV from the Special Immunizations Program (SIP; x6) or VEEV vaccinated donors (x4). They determined that there is variation in donor reactivity to SINV/EEEV depending on prior vaccination history and found that those vaccinated against all three encephalitic alphaviruses have a corresponding increase in serum reactivity and neutralization activity to SINV/EEEV compared to those vaccinated against VEEV alone.
The inventors also showed that donor serum reactivity varied also in response to recombinant EEEV proteins. Donors naturally infected or vaccinated against EEEV reacted with varying degrees to the more surface exposed structural protein, the E2 glycoprotein. There was an increase in serum cross-reactivity from donors vaccinated with VEEV alone to the more conserved and less exposed structural protein, the E1 glycoprotein. Further, it was demonstrated that donor serum reactivity varies in response to virus-like particles (VLPs) for EEEV, VEEV, and WEEV. Again, the reactivity of serum corresponds with prior infection or vaccination history. Naturally infected EEEV survivors were primarily reactive to EEEV VLPs. Higher serum endpoint titers were observed for SIP donors vaccinated with EEEV, VEEV, and WEEV compared to VEEV vaccines alone.
To further test donor serum reactivity and human mAb characterization, the inventors acquired multiple additional chimeric alphaviruses including SINV/MADV (formally SA-EEEV), SINV/VEEV, SINV/WEEV, SINV/CHIKV, and SINV/MAYV. They found the average relative B-cell frequency to be 1.0% for EEEV from two EBV-transformed naturally infected EEEV survivors. The inventors showed there is lower average relative B-cell frequencies to EEEV (0.21%), VEEV (0.26%), and WEEV (0.01%) from EBV-transformed SIP donors. Comparison between the average relative B-cell frequencies to EEEV may indicate low immunogenicity of the formalin-inactivated EEEV vaccine.
Using their established human hybridoma technology, the inventors isolated 64 human monoclonal antibodies (mAbs) from a naturally infected EEEV survivor (Donor 1069). The human mAbs were screened and selected for reactivity to recombinant EEEV structural proteins (E2 and E1 glycoproteins) and SINV/EEEV. Through characterization of this first human mAb panel to EEEV, they found that most of the human mAbs react to the EEEV E2 glycoprotein (x49). In addition, they showed that some human mAbs are reactive to the EEEV E1 glycoprotein (x10) and one is dependent on a virus-specific epitope (x1). Specific reactivity of four mAbs is yet to be determined. They also showed that there is diversity in reactivity to specified antigen from <10 ng/mL to <2 μg/mL half-maximal effective concentration (EC50) values.
The inventors identified several human mAbs from the panel that are cross-reactive (x6) with other encephalitic (VEEV and/or WEEV) and arthritogenic alphaviruses (CHIKV). They acquired multiple alphavirus full-length structural polyproteins (i.e., NA-EEEV, MADV, VEEV subtypes, WEEV, and CHIKV) to detect binding reactivity of human mAbs through cell surface display. Through focus reduction neutralization tests (FRNTs), the inventors found 6 human mAbs with potent neutralization activity (<10 ng/mL half-maximal inhibitory concentration (IC50 values) and 9 human mAbs with moderate neutralization activity (<2 μg/mL IC50 values) against SINV/EEEV. By further characterization, they identified one extremely potent neutralizing mAb, EEEV-33, with <10 ng/mL IC50 value against BSL-3 EEEV as determined through a CPE assay. Additionally, they identified one potent neutralizing mAb, EEEV-147, and 5 moderate neutralizing mAbs with <1 μg/mL and <6 μg/mL IC50 values against BSL-33 EEEV, respectively. The inventors found EEEV-33 to exhibit prophylactic (83%) and therapeutic (33%) activity in an in vivo aerosol BSL-3 EEEV challenge model, while they found a non-neutralizing human mAbs, EEEV-30, to possess prophylactic activity (50%) in an in vivo aerosol BSL-3 EEEV challenge model.
To identify steps in the replication cycle in which human mAbs neutralize SINV/EEEV, the inventors sought to test different neutralization mechanistic assays. As this is still in progress, it is not entirely clear the precise mechanism(s) of neutralization. However, it appears that most neutralizing human mAbs inhibit SINV/EEEV at a step post-attachment in the replication cycle. Some mAbs were found to show differences in pre- versus post-attachment entry neutralization assays, indicating the contribution of neutralization by these mAbs at attachment and/or entry steps in the replication cycle. This suggests that multiple mechanisms of neutralization are involved against SINV/EEEV in this diverse human mAb panel.
The inventors identified distinct antigenic determinants through competition-binding analysis and hydrogen-deuterium exchange mass spectrometry (HDX-MS). They found diverse epitopes recognized by the panel of human EEEV mAbs present on recombinant EEEV E2 glycoprotein. This further suggests the diversity in recognition of human mAbs to EEEV. Of the neutralizing mAbs, at least 3 neutralizing antigenic determinants were exposed. They showed that one main neutralizing antigenic site corresponds to domain B at the tip of the EEEV E2 glycoprotein, whereas the other minor neutralizing antigenic sites correspond to domain A of the EEEV E2 glycoprotein.
The inventors identified 40 additional human clonal hybridomas reactive to SINV/EEEV, recombinant EEEV structural proteins, and VLPs from an additional naturally infected EEEV survivor (Donor 982). These mAbs will soon be isolated for complete characterization. From initial characterization of hybridoma supernatants, there appears to be diverse reactivity to SINV/EEEV (x11), recombinant EEEV structural proteins (x21), and EEEV, VEEV, and WEEV VLPs or structural proteins (x8). Of these hybridomas, 10 exhibit neutralization activity (>70% reduction) against SINV/EEEV.
Six additional human mAbs were identified that are EEEV-specific (x5), or VEEV-specific (x1) from SIP donor (Donor 1047). These mAbs do not exhibit neutralization activity against SINV/EEEV (>5 μg/mL IC50 value). The VEEV-specific mAb will soon be characterized for neutralization activity against SINV/VEEV. The decrease in number of isolated human mAbs reflects the lower relative B-cell frequency of SIP donors compared to naturally infected EEEV survivors. Future isolation of human mAbs from SIP donors will be performed to identify VEEV-specific and potential cross-reactive/neutralizing human mAbs against the encephalitic alphaviruses.
Through the use of an established human hybridoma technique (described above), a large panel of human mAbs from a naturally-infected survivor of EEEV were isolated based on binding to a chimeric Sindbis virus expressing the EEEV surface proteins (SINV/EEEV). Specific binding and neutralization potency against SINV/EEEV were determined for the panel of human anti-EEEV mAbs. Of the panel of 57 human anti-EEEV mAbs isolated, 47 mAbs recognize the E2 glycoprotein. These mAbs recognize diverse epitopes on the E2 glycoprotein surface and display differences in affinity for virus-specific epitopes. From this panel, 12 exhibited neutralizing activity, 7 of which have very potent IC50 values (under 10 ng/mL) for neutralization and recognize at least three neutralizing antigenic determinants on the EEEV E2 glycoprotein. The neutralizing mAbs utilize multiple molecular mechanisms of virus inhibition; however, most of the mAbs appear to inhibit virus entry into host cells. An extremely potent neutralizing mAb (EEEV-33) exhibited prophylactic and therapeutic activity against lethal aerosol challenge in mice with WT EEEV. Through comprehensive characterization of 57 human anti-EEEV mAbs, several potent neutralizing mAbs were identified. These mAbs appear to inhibit virus entry and recognize several neutralizing antigenic determinants on the EEEV E2 glycoprotein to do so. The understanding of how these mAbs neutralize and interact with EEEV will help to facilitate the design of efficient therapeutics and vaccines against this clinically relevant alphavirus. The supporting data are shown in
SINV/EEEV production. BHK-21 cells were plated the day before using 3×107 cells per T-225 cm2 flask (Corning). The following day, cells were inoculated with SINV/EEEV at a MOI of 0.2 in DMEM/2% FBS. After incubation at 37° C. in 5% CO2 for 48 hours, SINV/EEEV was harvested by clarification of infected BHK-21 cell supernatants through a 0.2-μm pore size filter (Nalgene). Virus then was used fresh or stored at −80° C. until use. For cryo-EM studies, BHK-21 cells were inoculated with SINV/EEEV at a MOI of 5 in DMEM/2% FBS. After incubation at 37° C. in 5% CO2 for 16 hours, SINV/EEEV was harvested by centrifugation at 2,000×g at 4° C. for 10 minutes. Virus supernatant was precipitated in 14% (w/v) PEG 6000 (Sigma-Aldrich) and 4.6% (w/v) NaCl (Corning) overnight at 4° C., followed by centrifugation at 2,500×g at 4° C. for 30 minutes. A linear, continuous 10 to 50% OptiPrep (Sigma-Aldrich) gradient was used to purify the SINV/EEEV particles further at 136,873×g (rmax) for 1.5 hours at 4° C. using an AH-650 swinging bucket rotor (Sorvall). SINV/EEEV particles were collected and buffer exchanged into THE buffer (50 mM Tris-HCl pH 7.5 (Sigma), 100 mM NaCl, 0.1 mM EDTA (Corning)) via 100K MWCO Amicon® Ultra Centrifugal Filter Units (Millipore) to a concentration of ˜0.1 mg/mL total protein content, as determined by a Bradford assay (Thermo Fisher Scientific) or BCA assay (Thermo Fisher Scientific). Virus then was used fresh or stored at 4° C. until use.
Recombinant EEEV E1 ectodomain expression. The EEEV E1 ectodomain was produced in Expi293F cells using the ExpiFectamine 293 transfection kit (Gibco) according to the manufacturer's protocol. Briefly, 1 μg/mL of pcDNA3.1(+)-EEEV E1 ectodomain was diluted in Opti-MEM medium (Gibco) with ExpiFectamine 293 reagent (Gibco) for 15 to 20 minutes at room temperature before addition to the Expi293F cells. Cells were incubated at 37° C. in a humidified atmosphere of 8% CO2 and supernatant was harvested by centrifugation and subsequent filtering through a 0.45-μm pore size filter (Nalgene) 2 to 6 days after transfection. Cell supernatant was purified through a HisTrap excel column (GE Healthcare Life Sciences) according to the manufacturer's protocol on an ÄKTA pure 25M chromatography system.
Human hybridoma generation. PBMCs previously cryopreserved were thawed rapidly and transformed with Epstein-Barr virus (EBV), as previously described (Yu et al., 2008a; Yu et al., 2008b). Briefly, in B cell growth medium (ClonaCell-HY Medium A (Stem Cell Technologies), CpG (Invitrogen), Chk2 inhibitor (Sigma-Aldrich), cyclosporin A (Sigma-Aldrich), and EBV filtrate from the B95.8 cell line), 5 to 7 million PBMCs were added at 50 μL/well to 384-well plates (Thermo Fisher Scientific) and incubated at 37° C. in a humidified atmosphere of 7% CO2. After 7-10 days, cells were expanded to 96-well plates in B cell expansion medium (Medium A, CpG, Chk2 inhibitor, and irradiated heterologous human PBMCs (Nashville Red Cross) at a density of 10 million cells/mL). The plates were incubated at 37° C. in a humidified atmosphere of 7% CO2 for an additional 4-5 days prior to screening by ELISA, as described below. Cells from wells containing reactive supernatants were fused with the non-secreting myeloma cell line, HMMA2.5, using an electrofusion protocol as previously described (Yu et al., 2008a). Fused hybridomas were selected by plating in HAT medium (Medium A, ClonaCell™-HY Medium E (Stem Cell Technologies), 50×HAT medium supplement (Sigma-Aldrich), ouabain octahydrate; Sigma-Aldrich) at 50 μL/well in 384-well plates. The plates were incubated for a total of 14 to 21 days at 37° C. in a humidified atmosphere of 7% CO2 prior to screening by ELISA.
Human mAb generation. Wells containing reactive hybridomas were cloned by single-cell fluorescence-activated cell sorting. These hybridoma clones were expanded in Medium E serially into 48-well plates, 12-well plates, and T-75 cm2 flasks, respectively. Hybridoma clones were expanded further into T-225 cm2 flasks or G-Rex® devices (Wilson Wolf) in serum-free medium (Hybridoma SFM; Gibco). Supernatants were harvested after approximately 21 days, or in sets of 3 to 5 days, respectively, through a 0.2-μm pore size filter. Antibodies were purified from the filtrate using HiTrap Protein G (GE Healthcare Life Sciences), HiTrap MabSelect SuRe (GE Healthcare Life Sciences), HiTrap KappaSelect (GE Healthcare Life Sciences), HiTrap LambdaFabSelect (GE Healthcare Life Sciences), or CaptureSelect™ IgA affinity matrix (Thermo Fisher Scientific) columns on an ÄKTA pure 25M chromatography system. Antibodies were concentrated using 50K MWCO Amicon® Ultra centrifugal filter units (Millipore) followed by desalting and buffer exchange with 7K MWCO Zeba desalting columns (Thermo Fisher Scientific).
Hybridoma supernatant protein ELISA. Recombinant EEEV E2 glycoprotein (E3E2) (strain V105; IBT Bioservices) was diluted to 0.5 μg/mL in 1× D-PBS to coat 384-well ELISA plates (Thermo Fisher Scientific) at 25 μL/well and incubated at 4° C. overnight. The plates were washed 3× with D-PBS-T (1×D-PBS+0.05% Tween 20; Cell Signaling Technology) and blocked for 1 hour at room temperature with 25 μL/well blocking solution (2% non-fat dry milk (Bio-Rad), 2% goat serum (Gibco) in D-PBS-T). After blocking, the plates then were washed 3× with D-PBS-T and a volume of 10 to 25 μL/well of supernatant from each well containing EBV-transformed B cells or hybridoma cell lines was added. Plates were incubated for 2 hours at room temperature or overnight at 4° C. Plates then were washed 3× with D-PBS-T and a suspension of secondary antibodies (goat anti-human IgG-AP (Meridian Life Science) and goat anti-human IgA-AP; Southern Biotech) at a 1:4,000 dilution in 1% blocking solution (1% non-fat dry milk, 1% goat serum) was added at 25 μL/well for 1 hour at room temperature. Alkaline phosphatase substrate solution (phosphatase substrate tablets (Sigma-Aldrich) in AP substrate buffer (1M Tris aminomethane (Fisher Scientific), 30 mM MgCl2 (Sigma-Aldrich) was added at 25 μL/well following plate washing 4× with D-PBS-T. Plates were incubated at room temperature in the dark for 1-2 hours and then read at an optical density of 405 nm with a BioTek™ plate reader.
Hybridoma supernatant SINV/EEEV ELISA. A murine mAb (EEEV-66; MSD and ASK (Kim et al., 2019)) was diluted to 0.5 μg/mL in 1× D-PBS to coat 384-well ELISA plates at 25 μL/well and incubated at 4° C. overnight. The remainder of the ELISA protocol follows as described above for the protein ELISA. However, after blocking, clarified SINV/EEEV supernatant diluted 1:10 in 1× D-PBS (approximately 1×106 to 1×107 FFU/mL as determined through focus reduction test (FRT) with BHK-21 cells) at 25 μL/well was added. After incubation for 1-2 hours at room temperature, the plates then were washed 6× with D-PBS-T (the first 2-3 washes were conducted under BSL-2 conditions in a laminar flow biosafety cabinet).
5′ RACE nucleotide sequence analysis. Antibody heavy and light-chain variable region genes were sequenced from antigen-specific hybridoma lines that had been cloned biologically using single-cell flow cytometric sorting. Total RNA was extracted using the RNeasy Mini kit (Qiagen). A modified 5′ RACE (Rapid Amplification of cDNA Ends) approach was similar to that previously reported (Turchaninova et al., 2016). Briefly, 5 μL of total RNA was mixed with cDNA synthesis primer mix (10 μM each) and incubated for 2 min at 70° C. and then the incubation temperature was decrease to 42° C. to anneal the synthesis primers (1 to 3 min). After incubation, a mix containing 5× first-strand buffer (Clontech), DTT (20 mM), 5′ template switch oligo (10 μM), dNTP solution (10 mM each) and 10× SMARTScribe Reverse Transcriptase (Clontech) was added to the primer-annealed total RNA reaction and incubated for 60 min at 42° C. The first-strand synthesis reaction was purified using the AMPure Size Select Magnetic Bead Kit at a ratio of 0.6× (Beckman Coulter). Following, a single PCR amplification reaction containing 5 μL first-strand cDNA, 2×Q5 High Fidelity Mastermix (NEB), dNTP (10 mM each), forward universal primer (10 μM) and reverse primer mix (0.2 μM each in heavy-chain mix, 0.2 μM each in light-chain mix) were subjected to thermal cycling with the following conditions: initial denaturation for 1 min 30 s followed by 30 cycles of denaturation at 98° C. for 10 s, annealing at 60° C. for 20 s, and extension at 72° C. for 40 s, followed by a final extension step at 72° C. for 4 min. The first PCR reaction was purified using the AMPure Size Select Magnetic Bead Kit at a ratio of 0.6× (Beckman Coulter). Amplicon libraries then were prepared according to the Pacific Biosciences Multiplex SMRT Sequencing protocol and sequenced on a Pacific Biosciences Sequel system platform. Raw sequencing data was demultiplexed and circular consensus sequences (Cardoso et al., 2019). were determined using the Pacific Biosciences SMRT Analysis tool suite. The identities of gene segments and mutations from germlines were determined by alignment using the ImMunoGenetics (IMGT) database (Brochet et al., 2008; Giudicelli and Lefranc, 2011).
Recombinant human Fab, IgG1, and IgA1 production. Recombinant human anti-EEEV mAb or Fab molecules were produced in Expi293F cells using the ExpiFectamine 293 transfection kit according to the manufacturer's protocol. Briefly, 1 μg/mL of DNA was diluted in Opti-MEM I medium with ExpiFectamine 293 reagent for 15 to 20 minutes at room temperature before addition to the Expi293F cells. Cells were incubated at 37° C. in a humidified atmosphere of 8% CO2 and supernatant was harvested by centrifugation and subsequent filtering through a 0.45-μm pore size filter 6 to 7 days after transfection. For IgG1, IgA1, Fab molecules, cell supernatant was purified through a HiTrap MabSelect SuRe, CaptureSelect™ IgA affinity matrix, or CaptureSelect™ CH1-XL affinity column, respectively, according to the manufacturer's protocol on an ÄKTA pure 25M chromatography system. Antibodies were concentrated using 30K or 50K MWCO Amicon® Ultra Centrifugal Filter Units followed by desalting and buffer exchange with 7K MWCO Zeba desalting columns.
Protein EC50 ELISA. Recombinant EEEV E2 glycoprotein (E3E2) (strain V105; IBT BioServices), EEEV E1 ectodomain (strain FL93-939), or CHIKV E1 protein (Meridian Life Science) was diluted to 0.5, 2, or 2 μg/mL, respectively, in 1× D-PBS to coat 384-well ELISA plates at 25 μL/well and incubated at 4° C. overnight. A protein screening ELISA was performed as previously described above. However, instead of hybridoma supernatant, purified mAb was diluted to 10 μg/mL in blocking solution (1% non-fat dry milk, 1% goat serum) and added at 25 μL/well for 2 hours at room temperature. Additionally, plates were incubated at room temperature in the dark for 2 hours and then read at an optical density of 405 nm with a BioTek™ plate reader. For recombinant anti-EEEV mAbs and Fab molecules, a suspension of secondary antibodies (goat anti-human kappa-HRP (Southern Biotech) and goat anti-human lambda-HRP (Southern Biotech)) at a 1:4,000 dilution in 1% blocking solution (1% non-fat dry milk, 1% goat serum) was added at 25 μL/well for 1 hour at room temperature. 1-Step Ultra TMB-ELISA substrate solution (Thermo Fisher Scientific) was added at 25 μL/well following plate washing 4× with D-PBS-T. The reaction was stopped after 10 minutes at room temperature by addition of 25 μL/well of 1N HCl (Fisher Scientific). The plates then were read at an optical density of 450 nm with a BioTek™ plate reader. EC50 values were determined after log transformation of concentration values and non-linear regression analysis using sigmoidal dose-response (variable slope) using GraphPad Prism software version 8.
SINV/EEEV EC50 ELISA. A mouse anti-EEEV mAb (EEEV-66; MSD and ASK (Kim et al., 2019)) was coated onto 384-well plates and incubated at 4° C. overnight, as previously described above. After the blocking step, SINV/EEEV was diluted in 1× D-PBS to a titer of approximately 2.2×107 FFU/mL as determined through FRT with BHK-21 cells. After incubation for 2 hours at room temperature, the plates then were washed 6× with D-PBS-T (the first 2-3 washes were conducted under BSL-2 conditions in a laminar flow biosafety cabinet).
Focus reduction test (FRT). BHK-21 or Vero cells were plated at 2.5×106 cells/96-well plate in DMEM/5% FBS/10 mM HEPES (Corning) at 150 μL/well. Cells were incubated at 37° C. in 5% CO2 overnight. Cells plated approximately 24 hours prior were washed 2× with 1× D-PBS. Serial three-fold dilutions of SINV/EEEV were diluted in DMEM/2% FBS/10 mM HEPES and added at 100 μL/well to the cells. The virus and cells were incubated at 37° C. in 5% CO2 for 1.5 hours. A 2% methylcellulose (Sigma-Aldrich):2×DMEM (Millipore):4% FBS:20 mM HEPES overlay then was added to the cells at 100 μL/well. Cells then were incubated at 37° C. in 5% CO2 for 18 hours. Plates were fixed with 1% PFA (diluted in 1× D-PBS; Alfa Aesar) at 100 μL/well for 1 hour at room temperature. Plates then were washed 3× with 1× D-PBS followed by 1× Perm Wash (1× D-PBS, 0.1% saponin (Sigma-Aldrich), 0.1% BSA (Sigma-Aldrich)) at 200 μL/well. Immune EEEV ascites fluid (ATCC) at 1:6,000 dilution in 1× Perm Wash was then added at 50 μL/well. The plates were incubated either at room temperature for 2 hours with rocking or overnight at 4° C. Plates were washed 3× with 1× D-PBS-T followed by the addition of a suspension of secondary antibodies (goat anti-mouse IgG-Fc-specific-HRP (Jackson ImmunoResearch)) at 1:2,000 dilution in 1× Perm Wash. Plates were incubated for 1 hour at room temperature with rocking. Plates were washed 3× with 1× D-PBS-T followed by addition of TrueBlue™ peroxidase substrate solution (SeraCare) at 40 μL/well. Plates were incubated for ˜15 minutes at room temperature followed by a rinse with MilliQ water. The plates then were air dried and imaged on an ImmunoSpot S6 Universal machine (CTL).
Focus reduction neutralization test (FRNT). Vero cells were plated at 2.5×106 cells/96-well plate in DMEM/5% FBS/10 mM HEPES at 150 μL/well. Cells were incubated at 37° C. in 5% CO2 overnight. Purified mAb was diluted to 20 μg/mL (final concentration 10 μg/mL) in DMEM/2% FBS/10 mM HEPES. Serial three-fold dilutions of the mAb were performed. MAb-only dilutions were separated to serve as a negative control. SINV/EEEV was diluted to ˜100 focus-forming units (ffu)/well in DMEM/2% FBS/10 mM HEPES and added to the mAb serial dilutions. The mAb:virus mixture was incubated at 37° C. in 5% CO2 for 1 hour. Vero cells plated approximately 24 hours prior were washed 2× with 1× D-PBS. The mAb:virus mixture then was added at 100 μL/well to the cells and incubated at 37° C. in 5% CO2 for 1.5 hours. A 2% methylcellulose:2×DMEM/4% FBS/20 mM HEPES overlay then was added to the cells at 100 μL/well. Cells were incubated at 37° C. in 5% CO2 for 18 hours. Plates were fixed and immunostained as described for FRT.
Post-attachment neutralization assay. Vero cells were plated at 2.5×106 cells/96-well plate in DMEM/5% FBS/10 mM HEPES at 150 μL/well. Cells were incubated at 37° C. in 5% CO2 overnight. Vero cells plated approximately 24 hours prior the media was replaced with chilled DMEM/2% FBS/10 mM HEPES and cells were chilled at 4° C. for 15 minutes. SINV/EEEV was diluted to ˜100 ffu per well in chilled DMEM/2% FBS/10 mM HEPES and added to the cells at 4° C. for 1 hour. Purified mAb was diluted to 10 μg/mL in chilled DMEM/2% FBS/10 mM HEPES. Serial three-fold dilutions of the mAb were performed. MAb-only dilutions were separated to serve as a negative control. Cells were washed 3× with chilled DMEM/2% FBS/10 mM HEPES. mAb then was added at 100 μL/well to the cells and incubated at 4° C. for 1 hour. Cells were washed 3× with DMEM/2% FBS/10 mM HEPES and incubated at 37° C. for 15 minutes. A 2% methylcellulose:2×DMEM/4% FBS/20 mM HEPES overlay then was added to the cells at 100 μL/well. Cells were incubated at 37° C. in 5% CO2 for 18 hours. Plates were fixed and immunostained as described for FRT.
Entry inhibition assay. A FRNT was performed as previously described. However, prior to addition of overlay, the cells were washed 4× with DMEM/2% FBS/10 mM HEPES and incubated at 37° C. in 5% CO2 for 15 minutes. A 2% methylcellulose:2×DMEM/4% FBS/20 mM HEPES overlay then was added to the cells at 100 μL/well. Cells were incubated at 37° C. in 5% CO2 for 18 hours. Plates were fixed and immunostained as described for FRT.
EEEV plaque reduction neutralization test. Antibody preparations were diluted serially (using 2-fold dilutions) and incubated with ˜100 pfu of EEEV FL93-939 for 1 h at 37° C. Anti-EEEV ascites serum (ATCC) was used as a positive control. After incubation, Vero cell monolayer cultures in 6-well plates were inoculated and incubated for 1 h at 37° C. After overlay with agarose immunodiffusion grade (MP Biomedicals), plates were incubated for 2 days followed by overlay with neutral red for at least 6 h to count plaques. Percent neutralization was calculated based on the number of plaques in each serum dilution compared to the number of plaques in untreated control wells inoculated with virus.
Competition-binding analysis using biolayer interferometry. Anti-penta his (HIS1K) biosensor tips (ForteBio) on an Octet Red96 or HTX biolayer interferometry instrument (ForteBio) were soaked for 10 minutes in 1× kinetics buffer (ForteBio), followed by a baseline signal measurement for 60 seconds. Recombinant EEEV E2 glycoprotein (5 μg/mL; IBT BioServices) was immobilized onto the biosensor tips for 60 seconds. After a wash step in 1× kinetics buffer for 30 to 60 seconds, the first antibody (50 μg/mL) was incubated with the antigen-containing biosensor for 600 seconds. After a wash step in 1× kinetics buffer for 30 to 60 seconds, the biosensor tips then were immersed into the second antibody (50 μg/mL) for 180 seconds. Comparison between the maximal signal of each antibody compared to a buffer-only control was used to determine the percent binding of each antibody. A reduction in maximum signal to <33% of un-competed signal was considered full competition of binding for the second antibody in the presence of the first antibody. A reduction in maximum signal to between 33 to 67% of un-competed was considered intermediate competition of binding for the second antibody in the presence of the first antibody. Percent binding of the maximum signal >67% was considered absence of competition of binding for the second antibody in the presence of the first antibody.
Alanine-scanning mutagenesis analysis. WT EEEV (strain FL93-939) structural proteins (capsid-E3-E2-6K-E1) and E2 mutants were expressed on the surface of Expi293F cells using the ExpiFectamine 293 transfection kit according to the manufacturer's protocol as previously described. Cells were incubated at 37° C. in a humidified atmosphere of 8% CO2, were harvested 24 hours after transfection, and fixed with 1% PFA/PBS. Cells were washed twice with 1×DPBS and stored at 4° C. in FACS buffer (1×DPBS, 2% FBS, 2 mM EDTA) until use or used immediately. Cells were plated at 40,000-50,000 cells/well in 96-well V-bottom plates (Corning). Anti-EEEV mAbs or the irrelevant mAb negative control, rDENV-2D22, were diluted to 1 μg/mL in FACS buffer and incubated with the cells for 1 hour at 4° C. Cells were washed with FACS buffer and then incubated with secondary antibodies (anti-human IgG-PE (Southern Biotech) and anti-human IgA-PE (Southern Biotech) or anti-mouse IgG-PE (Southern Biotech)) diluted 1:1,000 in FACS buffer for 1 hour at 4° C. Cells were washed with FACS buffer and resuspended in 25 μL/well of FACS buffer. Number of events were collected on an IntelliCyt® iQue Screener PLUS flow cytometer (Sartorius). For analysis, mock transfected Expi293F cells were included as a negative control and subtracted as background. The percent binding of each mAb to the alanine mutants was compared to the WT EEEV structural protein control. An initial screen of residues D1-L267 was performed to identify residues with <25% binding and at least two mAbs with >70% binding to control for expression. These residues were further assessed for loss-of-binding phenotype for at least two additional biological replicates. Critical residues were defined as at least two mAbs with >70% binding to control for expression and <25% binding relative to WT protein.
Cryo-EM sample preparation and data acquisition. Purified SINV/EEEV particles and recombinant anti-EEEV Fab (EEEV-33 or EEEV-143) (1:10 molar ratio) were incubated on ice for 30 minutes. 3 μL of mixture was applied on Lacy 400 mesh copper grids (TED PELLA) or carbon coated R2/2 copper Quantifoil holey grids (Electron Microscopy Sciences). The samples were vitrified in liquid ethane using a Vitrobot (Thermo Fisher Scientific) set at 4° C. and 100% relative humidity under BSL-2 containment conditions. Images for SINV/EEEV:EEEV-33 Fab were collected on a Titan Krios electron microscope (Thermo Fisher Scientific) equipped with a K2 Summit Direct Electron Detector (Gatan) operated at 300 kV and having a nominal pixel size of 1.64 Å per pixel. Images for SINV/EEEV:EEEV-143 Fab were collected on a Glacios electron microscope (Thermo Fisher Scientific) equipped with a K2 Summit Direct Electron Detector operated at 200 kV and having a nominal pixel size of 2.0 Å per pixel. Micrographs were acquired automatically using Leginon software (Carragher et al., 2000). The total exposure time for both samples was 10 sec and frames were recorded every 0.2 sec. Defocus values ranged from 1.0 to 2.5 μm. The total accumulated does was ˜50 e−/Å2 for SINV/EEEV:EEEV-33 Fab and ˜25 e−/Å2 for and SINV/EEEV: EEEV-143 Fab samples.
Cryo-EM data processing. Cryo-EM movies (50 frames, 200 msec exposure per frame) were corrected for beam-induced motion and dose-weighted using MotionCor2 (Zheng et al., 2017) resulting in global motion-corrected frame stacks and summed micrographs. Contrast transfer function (CTF) parameters was estimated using Gctf (Zhang, 2016). EEEV particles manually picked from selected micrographs in RELION 3.0 (Zivanov et al., 2018) using a box size of 800 pixels (1.64 Å) or 700 pixels (2.0 Å). Approximately 18,000 particles were picked from 2,111 micrographs of SINV/EEEV:EEEV-33 Fab and 10,000 particles were picked from 2,501 micrographs of SINV/EEEV:EEEV-143 Fab. The particles were subjected to reference-free 2D classification in RELION 3.0 and selected particles associated with good classes were exported to cisTEM (Grant et al., 2018). The de-novo initial model was generated without imposing any symmetry (C1 symmetry) which was subjected for 3D auto refinement (It symmetry) without mask in cisTEM. Further, the 3D model and associated particles obtained from cisTEM were exported to RELION 3.0 and used for the final masked 3D refinement (It symmetry) and postprocessing (
EEEV VLP negative stain grid preparation and imaging. For screening and imaging of negatively stained (NS) EEEV VLP (Ko et al., 2019) or EEEV VLP:EEEV-143 Fab samples, ˜3 μL of the sample at concentrations of 10-15 μg/mL was applied to glow discharged grid with continuous carbon film on 400 square mesh copper EM grids (Electron Microscopy Sciences). The grids were stained with 0.75% uranyl formate (Ohi et al., 2004). Images were recorded on a 4 k×4 k CCD camera using an FEI TF20 transmission electron microscope (Thermo Fisher Scientific) operated at 200 keV and control with SerialEM (Mastronarde, 2005). All images were taken at 50,000× magnification with a pixel size of 2.18 Å/pix in low-dose mode at a defocus of 1.5 to 1.8 μm. Image processing was performed using the Scipion software package (de la Rosa-Trevin et al., 2016) Images were import and particles were CTF estimated (Rohou and Grigorieff, 2015), then picked (Sorzano et al., 2013). 2D class averages were performed using Xmipp3.0 c12d (de la Rosa-Trevin et al., 2013; Sorzano et al., 2013).
EEEV VLP cryo-EM sample preparation and data collection. For the EEEV VLP:EEEV-143 Fab complex, EEEV VLP at concentration of 0.2 mg/mL was mixed with EEEV-143 Fab in a molar ratio of 720:1 (Fab:VLP) and incubated on ice for 1 hour. Then, 2.2 μL of either EEEV VLP or EEEV VLP/EEEV-143 Fab was applied 2× to a 300 mesh Lacey grid that was glow discharged for 25 s at 25 milliamperes. The grid was blotted for 2 s before being plunged into liquid ethane using a FEI Vitrobot Mark4 (Thermo Fisher Scientific) at 8° C. and 100% humidity. The grids were imaged in Titan Krios (Thermo Fisher Scientific) operated at 300 keV equipped with Falcon 3EC Direct Electron Detector (Thermo Fisher Scientific) using counting mode. Movies collected at a nominal magnification of 96,000×, pixel size of 0.8608 A/pix for the EEEV VLP and at 75,000×, pixel size of 1.11 A/pix for the EEEV VLP:EEEV-143 Fab complex. Both data set were in a defocus range of 0.8 to 2.8 μm. Grids were exposed at 1e−/Å2/frame over 30 frames resulting in a total dose of ˜30 e−/Å2 (see also Table S1).
EEEV VLP cryo-EM data processing. Movies were pre-processed on-the fly (MotionCor2 (Zheng, 2017 #89), Gctf (Zhang, 2016), using RELION (Scheres, 2012; Zivanov et al., 2018). Micrographs with low resolution, high astigmatism and defocus were removed from the data set. Further processing was done using RELION 3.1 beta. A small subset of micrographs were autopicked first by RELION LoG (Fernandez-Leiro and Scheres, 2017) and 2D class averages were determined. Representative classes were selected and used as templates for another round of autopicking. The particles were then subjected to multiple rounds of 2D class averages and 3D classification (with and without symmetry). The particles from the selected classes were re-extracted, 3D classified and subjected to 3D auto refinement. The data was processed further with Ctfrefine, polished and postprocessing was done (detailed statistics are provided in Table S1 and Figure S7).
EEEV VLP model building. For the EEEV VLP, a homology model of SINV/EEEV (PDB: 6MX4) was used for docking to the cryoEM map with PHENIX (Adams et al., 2010). To improve coordinate fitting, the model was subjected to iterative refinement of manual building in Coot (Emsley and Cowtan, 2004) and PHENIX real-space refine (Adams et al., 2010). The model was validated with Molprobity (Chen et al., 2010). For the EEEV VLP:EEEV-143 Fab complex, the refined model of the VLP was used as starting model and was docked to the EM map with UCSF Chimera (Pettersen et al., 2004). The model was then refined in PHENIX (phenix real-space refine) by rigid body and a homology model of EEEV-143 Fab (PDB: 6MWX) was mutated to the EEEV-143 Fab sequence, docked, and rigid body refined to the EM map.
Mouse aerosol challenge with EEEV. Mice were inoculated with EEEV strain FL93-939 by aerosol, as previously described (Trobaugh et al., 2019). Briefly, mice were challenged with ˜10 LD50 (˜2,500 PFU) of 20% sucrose-purified WT EEEV FL93-nLuc TaV using the AeroMP exposure system (Biaera Technologies, Hagerstown, Md.) inside a class III biological safety cabinet and either an Aeroneb nebulizer (Aerogen) or 3-jet Collison nebulizer (CH Technologies). All mice were monitored twice daily for morbidity and mortality.
In vivo imaging At different times after challenge, mice were injected with 10 mg of Nano-Glo substrate (Promega) subcutaneously in 500 mL PBS, as previously described (Gardner et al., 2017). Four minutes after substrate injection, the mice were imaged using the IVIS Spectrum CT Instrument (PerkinElmer) using the autoexposure setting. The total flux (photons per second) in the head region was calculated for each animal using Living Image Software 4.5.1, with all images set to the same scale.
Quantification and statistical analysis. Statistical details can be found in the figure legends. EC50 values for binding and IC50 values for neutralization were determined after log transformation of concentration values and non-linear regression analysis using sigmoidal dose-response (variable slope). Direct comparison of differences in mAb binding to virion particle-specific epitopes versus sites in recombinant E2 glycoprotein cannot be performed on a molar basis. The precise total number of epitopes present on SINV/EEEV particles is unknown in an antibody-based capture ELISA format and may be greater than that on the recombinant EEEV E2 glycoprotein. To describe the differences in mAb binding, a virus/protein EC50 ratio was used. Survival curves were generated using the Kaplan-Meier method and curves compared the log-rank test with Bonferroni multiple comparison correction (n=number of mice, *=p<0.05, **=p<0.01, ns=not statistically significant). A one-way ANOVA with Dunnett's multiple comparison correction was used to compare luminescence intensity of IVIS images (*=p<0.01). All statistical analyses were performed using Prism software version 8 (GraphPad).
Human anti-EEEV mAbs isolated from a naturally infected EEEV survivor potently neutralize EEEV. The inventor isolated a panel of forty-eight human anti-EEEV mAbs from the B cells in a peripheral blood sample of a donor who had a prior documented, naturally-acquired EEEV infection. To down-select mAbs from this panel, the inventor focused on those that could efficiently neutralize Sindbis virus (SINV)/EEEV, a chimeric virus for use in BSL2 conditions containing the nonstructural proteins of SINV and displaying the structural proteins of EEEV strain FL93-939 (Kim et al., 2019). Twelve human anti-EEEV mAbs exhibited neutralization activity against SINV/EEEV (
The activity of human anti-EEEV mAbs also was tested against the pathogenic EEEV strain FL93-939 under BSL-3 conditions. Overall, the neutralization potency with EEEV was consistent with results obtained with SINV/EEEV, supporting the use of chimeric virus for functional analysis (
Neutralizing human anti-EEEV mAbs bind to SINV/EEEV particles and/or recombinant EEEV E2 glycoprotein. To identify the antigen specificity of the neutralizing human anti-EEEV mAbs, the inventor assessed binding to SINV/EEEV particles and EEEV E2 or E1 glycoproteins (
Optimal neutralization of SINV/EEEV requires bivalent interactions. The neutralization potency of Fab and IgG molecules has been compared previously for several alphaviruses (Hasan et al., 2018; Long et al., 2015). In some cases, the neutralizing activity of the Fab form of the mAb is substantially lower than the intact IgG (Hasan et al., 2018). However, the inventor found that the Fab forms for some neutralizing human anti-EEEV mAbs (EEEV-33, EEEV-94, EEEV-106, EEEV-129, EEEV-143) still neutralized SINV/EEEV efficiently with <1 nM (<300 ng/mL) IC50 values (
In contrast, EEEV-27 and EEEV-93 exhibited greatly reduced neutralization potency when expressed as Fab molecules, compared to IgG, and showed a corresponding reduction in binding to SINV/EEEV particles (>1,000-fold reduction in IC50 and EC50 values) (
The IC50 values of neutralization and EC50 values for binding to SINV/EEEV did not correspond for all of the inhibitory human anti-EEEV mAbs or Fabs. EEEV-7, EEEV-12, EEEV-21, EEEV-97, and EEEV-147 bound SINV/EEEV particles with similar strength as Fab molecules, compared to IgG. However, a reduction in neutralization potency was observed for EEEV-7, EEEV-12, EEEV-21, EEEV-97, and EEEV-147 as Fab molecules, suggesting that the bivalent interactions as an IgG may enable cross-linking of two E2 protomers for optimal neutralization of SINV/EEEV.
Neutralizing human anti-EEEV mAbs recognize three antigenic determinants on the EEEV E2 glycoprotein. The E2 glycoprotein consists of three structural domains: 1) a flexible domain B at the apical surface that shields the fusion loop at the distal tip of the E1 glycoprotein, 2) domain A, which is suspected to contain the putative receptor binding site, and 3) domain C that lies proximal to the viral membrane and contains the transmembrane domain (Voss et al., 2010); Chen et al., 2020; Gardner et al., 2013; Gardner et al., 2011; Hasan et al., 2018; Zhang et al., 2011; (Fox et al., 2015). To determine the number of major antigenic sites recognized by neutralizing human anti-EEEV mAbs, the inventor performed competition-binding studies utilizing biolayer interferometry. Binding of human anti-EEEV mAbs was performed in competition with previously described domain B-specific murine anti-EEEV mAbs, including mEEEV-69 and mEEEV-86 (Kim et al., 2019). From this analysis, the inventor identified at least three competition-binding groups on the EEEV E2 glycoprotein corresponding to three neutralizing antigenic determinants (
To identify critical interaction residues for neutralizing human anti-EEEV mAbs, the inventor generated an alanine-scanning mutagenesis library for the EEEV E2 glycoprotein. Each E2 protein residue was mutated to alanine, or alanine residues to serine, and the library was used to map residues for which a loss-of-binding phenotype of the antibody occurred. An initial screen (D1-L267) using this mutant E2 library was performed to identify residues with low level (<25%) of mAb binding either due to a loss-of-binding phenotype or reduced expression of the E2 glycoprotein (
SINV/EEEV neutralization escape mutant viruses with the mutations M68T, G192R, or L227R of the E2 glycoprotein were identified previously using domain A/B murine anti-EEEV mAbs. The mutated residues affected the neutralization potency of domain A and A/B specific murine anti-EEEV mAbs to SINV/EEEV. Domain B-specific murine anti-EEEV mAbs inhibited the escaped viruses as efficiently as WT SINV/EEEV (Kim et al., 2019). To assess whether viral escape also occurred for the neutralizing human anti-EEEV mAbs, the inventor tested activity of the mAbs against these viruses (
EEEV-33 and EEEV-143 inhibit SINV/EEEV entry into cells. To begin to elucidate the mechanism of neutralization for human anti-EEEV mAbs, the inventor focused on two potently inhibitory mAbs, EEEV-33 (IgG1; domain A) and EEEV-143 (IgA1; domain B). Entry blockade was assessed by incubating mAbs with SINV/EEEV, allowing the virus to bind and internalize into cells at 37° C., and followed by extensive washing to remove unbound virus and mAb (
Next, to assess whether EEEV-33 or EEEV-143 block virus attachment to cells, a post-attachment neutralization assay was performed (
EEEV-33 binds to a critical epitope within domain A of the E2 trimer of SINV/EEEV particles. The inventor characterized the structural basis for EEEV-33 recognition of SINV/EEEV using single particle cryo-electron microscopy (cryo-EM) and determined a three-dimensional structure of the complex at ˜7.2 Å resolution (
EEEV-143 binds to a critical epitope within domain B of the E2 trimer of SINV/EEEV particles and EEEV virus-like particles (VLPs). The inventor also characterized the structural basis of neutralization of EEEV-143 by studying the mAb in complex with SINV/EEEV particles using single particle cryo-EM. The inventor determined a three-dimensional structure at ˜8.3 Å resolution (
EEEV-33 protects against EEEV aerosol challenge in mice. The inventor next assessed the efficacy for EEEV-33 in vivo using an aerosol-challenge mouse model and a nanoLuciferase-expressing strain of EEEV FL93-939 (Sun et al., 2014). This model is more stringent than parenteral inoculation models, as aerosolization facilitates rapid entry into the brain via infection of epithelial cells and neurons in the cribriform plate and spread to the olfactory bulb (Phelps et al., 2019). In this model, prophylaxis with a 100-μg dose of EEEV-33 resulted in 91% survival, when administered by the intraperitoneal (i.p.) route 24 hours prior to virus exposure (
EEEV-143 protects and treats against WT EEEV aerosol challenge in mice. The mucosal IgA response is suspected to play a role in protection because mice with low IgG serum titers following vaccination with EEEV live attenuated virus candidates still were protected against lethal EEEV aerosol challenge (Trobaugh et al., 2019). Active transport of polymeric IgA into the lumen of mucosal respiratory tissue sites may increase the relative concentration of IgA antibodies in mucosal secretions and might enhance the therapeutic efficacy of a mAb for EEEV administered via the aerosol route. To assess this possibility, the inventor studied the treatment efficacy of the IgA isotype form of the neutralizing mAb EEEV-143. EEEV-143 mediated 100% survival when a 100-μg dose was administered i.p. route 24 hours prior to virus exposure compared to rDENV-2D22 (
aSurface-exposed critical alanine residues (<25% binding relative to WT) are identified as determined through alanine-scanning mutagenesis library analyses for each mAb. See FIG. 3B for a heat map representation of average percent binding of human anti-EEEV mAbs to critical residues and FIG. S2 for bar graph representation of human anti-EEEV mAb binding to critical residues.
bCritical alanine residues (<25% binding relative to WT) that are not surface exposed, as determined through alanine-scanning mutagenesis library analyses for each mAb are identified. The identified residues may result in a loss of binding phenotype due to allosteric effects on the epitope. N/A = not applicable
cNeutralization potency of human anti-EEEV mAbs for the SINV/EEEV escape mutant viruses (M68T, G192R, and L227R). Minimal reduction indicates that neutralization potency of respective human anti-EEEV mAb is similar to neutralization activity against WT SINV/EEEV. Escape mutants with a >10-fold reduction in neutralization potency are indicated for each mAb. Parentheses include escape mutants with >5-fold reduction in neutralization potency. See Figure S3 for neutralization curves of human anti-EEEV mAbs to SINV/EEEV escape mutant viruses (M68T, G192R, and L227R).
In this study, the inventor describes human mAbs isolated against EEEV from the B cells of an EEEV-immune individual with prior natural infection. Isolation of human anti-EEEV mAbs with moderate or potent neutralization activity against the chimeric virus Sindbis (SINV)/EEEV allowed for the characterization of the molecular and structural basis of neutralization against EEEV and addressed important questions relating to the human anti-EEEV antibody response. With identified a panel of 12 moderately and potently neutralizing human anti-EEEV mAbs to SINV/EEEV and WT EEEV. The inventor observed diverse patterns of reactivity and dependence on valency for binding and/or neutralization of SINV/EEEV. Potent mAbs neutralized SINV/EEEV as Fab molecules, suggesting bivalency or tetravalency is not necessary but may be required for optimal neutralization of SINV/EEEV. Two mAbs, EEEV-27 and EEEV-93, displayed reduced binding and neutralization potency as Fab molecules, indicating the requirement for bivalent interactions. Additionally, EEEV-7, EEEV-12, EEEV-21, EEEV-97, and EEEV-147 displayed reduced neutralization potency but not reduced binding as Fab molecules, indicating the neutralization mechanism for these mAbs may involve cross-linking of two E2 protomers as IgG molecules. Recognition of three neutralizing antigenic determinants (domains A, B, and A/B) was observed, with a majority of neutralizing mAbs isolated from this individual recognizing the E2 structural domain B. Further characterization of EEEV-33 and EEEV-143 identified the molecular and structural basis of neutralization, which enabled these mAbs to exhibit in vivo efficacy against highly pathogenic EEEV in an aerosol challenge model.
EEEV-33 is a potently neutralizing human anti-EEEV mAb, with 3.1 pM or <37 pM IC50 values for neutralization against SINV/EEEV or EEEV, respectively. EEEV-33 preferentially binds SINV/EEEV particles compared to recombinant EEEV E2 glycoprotein, suggesting recognition of a quaternary epitope on the viral surface. A ˜7.2 Å three-dimensional structure of SINV/EEEV bound to EEEV-33 Fab molecules helped elucidate the basis of neutralization by this antibody. The high neutralization potency of EEEV-33, which has similar potency as a Fab molecule, was consistent with the ability of three Fabs to bind each domain A binding site in the E2 trimer. The ability of three EEEV-33 Fabs to bind to each E2 trimer in the virus is unusual, compared to previous structural analyses of murine anti-EEEV mAbs in complex with SINV/EEEV particles (Hasan et al., 2018). From the murine antibody structural analysis, it was observed that steric clashes between Fab molecules, which target domain A of the E2 glycoprotein in a radial orientation, would limit the capacity for complete occupancy of the E2 trimer. However, EEEV-33 binds a unique epitope compared to the murine anti-EEEV mAbs, and the neutralization potency of EEEV-33 even as a Fab molecule is consistent with the occupancy observed in the cryo-EM model. Fab constant domain contacts were observed between Fabs bound within the trimeric spike, indicating that as an IgG molecule steric hindrance may limit occupancy. However, this feature may allow for intra-spike cross-linking to occur for neutralization. The inventor also observed that the protomers of the E2 trimer do not change conformation upon EEEV-33 Fab binding. Together, these data suggest that EEEV-33 recognizes a critical conformational epitope present on domain A of the E2 trimer of SINV/EEEV particles. Binding to this epitope, EEEV-33 may stabilize or sterically hinder the E2 trimer, in which inhibition of viral entry into cells or prevention of conformational changes necessary for virus fusion with cells could occur.
A neutralizing VEEV-specific human mAb similar to EEEV-33, designated F5, was characterized previously (Hunt et al., 2010; Porta et al., 2014). Antibody F5 was isolated using phage display from B cells of VEEV-immune donors. This antibody binds to residues 115-119 in domain A of the E2 glycoprotein, analogous to those recognized by EEEV-33. In contrast to EEEV-33, F5 Fab molecules bind this region of VEEV in a radial orientation and occupy one third of the binding sites. F5 was shown to stabilize the E2 trimer via intra-spike cross-linking (Porta et al., 2014). The similarity in binding and neutralization activity for two human mAbs (EEEV or VEEV) suggests a conserved antigenic site (residues 115-120) that may be targeted through unique mechanisms for neutralization of the encephalitic alphaviruses in humans.
EEEV-143 is another potently neutralizing human anti-EEEV mAb with 2.8 pM or 315 pM IC50 values against SINV/EEEV or EEEV, respectively. EEEV-143 was isolated from a human B cell as an IgA1 antibody. In mice vaccinated with live-attenuated EEEV vaccine candidates, protection against aerosol challenge was observed even in some mice with low serum PRNT80 values (Trobaugh et al., 2019). This observation suggests that other immune responses may be involved, such as mucosal IgA for protection against aerosol challenge (Trobaugh et al., 2019). Strategies to prevent and/or treat EEEV through antibody-based methods that specifically target mucosal sites could be an important approach. Naturally occurring polymeric IgA (pIgA) molecules are transported actively across mucosal surfaces via the polymeric immunoglobulin receptor (pIgR) (Turula and Wobus, 2018). Transcytosis of neutralizing antibodies across the mucosa may block EEEV infection at or near the site of inoculation to prevent dissemination to the brain.
The structural basis of neutralization for EEEV-143 was determined using single particle cryo-EM of SINV/EEEV bound to EEEV-143 Fab molecules. The resulting ˜8.3 Å structure showed that three Fabs also bound to each protomer in the E2 trimer. Fab constant domain contacts were observed around the two-fold axis and ˜11 Å distance between Fabs bound to the q3 and i3 spikes across the three-fold axis. These contacts suggest that EEEV-143 forms inter-spike cross-links between adjacent E2 trimers as an IgG or IgA molecule. This inter-E2 trimer cross-linking could stabilize or sterically hinder the trimer to inhibit viral entry or prevent conformational changes necessary for virus fusion with host cells. Again, the binding of three EEEV-143 Fab molecules to each E2 trimer is unusual when compared to studies of neutralizing antibodies generated in mice, where steric clashes between Fab molecules that target domain B of the E2 glycoprotein in a tangential orientation limited the capacity for complete occupancy of the E2 trimer. However, the neutralization potency of EEEV-143 as Fab molecules is consistent with the inventor's structural analysis. The inventor suggests that steric clashes still will occur in the context of EEEV-143 expressed as a polymeric IgA molecule (dimeric IgA complex with joining chain) as suggested by the reduction in the detected binding strength of this molecule compared to recombinant IgG1 or Fab molecules. The bulkiness of a polymeric IgA may reduce the occupancy of SINV/EEEV particle binding sites. Optimal in vitro neutralization of SINV/EEEV occurs as a polymeric IgA compared to Fab molecule, as there is >200-fold reduction in neutralization potency. Thus, the inter-spike cross-linking observed for EEEV-143 may require a bivalent (IgG) or tetravalent (IgA) antibody interaction for optimal neutralization of SINV/EEEV.
A neutralizing CHIKV mAb similar to EEEV-143, designated CHK-265, was characterized previously (Fox et al., 2015). CHK-265 is a broadly neutralizing and protective arthritogenic alphavirus mAb that inhibits viral entry and egress from cells. The ˜16 Å cryo-EM reconstruction of CHIKV 181/25 particles in complex with CHKV-265 Fab molecules displays binding of three Fab molecules to each trimeric spike (q3 and i3). Inter-spike cross-linking was observed between two E2 protomers through recognition of domain B residues on one protomer and contacts domain A residues on an adjacent protomer. This binding leads to movement of domain B further over the E1 fusion loop and repositioning of domain A upon binding. CHK-265 Fab constant domain contacts also were observed across the two-fold axis further supporting the cross-liking mechanism of virus particles by CHK-265 as an IgG molecule. In contrast, EEEV-143 recognizes residues within domain B on one protomer and does not appear to induce conformational changes upon binding. Similarly, the constant domain Fab contacts observed for EEEV-143 around the 2-fold axis suggests that EEEV-143 may form inter-spike cross-links as an IgG or IgA molecule. The reduction in neutralization of EEEV-143 as a Fab molecule suggests that this mechanism is important for optimal neutralization of EEEV-143 at this site.
EEEV is classified as a USDA/CDC Select Agent due to potential for aerosolization and use as a bioterrorism agent. To mimic potential exposure of EEEV as a bioterrorism agent, aerosol challenge has been studied in mice and non-human primates (Phelps et al., 2019; Trobaugh et al., 2019; Wirawan et al., 2019). In this approach, mice were inoculated with EEEV via the aerosol route to assess the pre- or post-exposure treatment efficacy of EEEV-33 (IgG1) and EEEV-143 (IgA1). When given 24 hours before infection, EEEV-33 or EEEV-143 each protected mice with 91 or 100% survival compared to the control, respectively. When administered 24 hours after EEEV inoculation, EEEV-33 treated mice with 27% survival whereas EEEV-143 treated mice with 20 to 80% survival compared to the control. This experimental animal aerosol challenge model is stringent, since the rapid kinetics of viral replication in the central nervous system quickly decreases the likelihood of antibody-mediated protection. These studies suggest that there is need to study the in vivo efficacy in more detail, as multiple factors could affect efficacy including the timing for antibody administration, virus inoculation timing and concentration, route of virus infection, and antibody isotype and transcytosis across the mucosa and blood-brain barrier to achieve post-exposure treatment of EEEV via the aerosol route. As EEEV-33 and EEEV-143 recognize two different antigenic sites on the E2, a potential combination therapy with EEEV-33 and EEEV-143 might have greater efficacy and decrease the likelihood of viral escape mutant viruses generated in vivo.
Soon after EEEV aerosol challenge, virus-induced lesions are observed in the olfactory bulb (Phelps et al., 2019). The spread and course of EEEV infection within the brain parenchyma corresponds with the severity of olfactory bulb lesions (Phelps et al., 2019). Once virus entry into the brain occurs, it becomes challenging to neutralize the virus sufficiently to allow for control of spread and survival (Morens et al., 2019). One of the difficulties in treatment of EEEV is the requirement for antibodies to cross the blood-brain barrier (BBB) (Morens et al., 2019), which limits transport of molecules >400 Da (Neves V, 2016). During viral infection, disruption of the BBB occurs, allowing for infiltration of immune cells and larger molecules, such as antibodies (Metcalf et al., 2013; Metcalf and Griffin, 2011). However, with alphaviruses in the mouse model, the breakdown of the BBB is a late event in the disease course (Salimi et al., 2020) and the inflammatory consequences of viral replication result in neurological deterioration, making it difficult to recover after extensive infection (Griffin, 2016; Metcalf and Griffin, 2011). Developing molecules that cross this barrier more efficiently, such as through receptor-mediated transcytosis, might enhance the efficacy of therapeutic antibodies for EEEV infection (Pulgar, 2018).
Here, the inventor describes the isolation and characterization of a neutralizing human antibodies against EEEV. These studies provide molecular and structural bases of neutralization of EEEV by human mAbs and suggest several future research directions that could provide treatment options for patients. These include defining the importance of mucosal IgA and avidity interactions for optimal neutralization of EEEV, the correlates of antibody-mediated protection, and mechanisms for enhancing antibody transport across the BBB in vivo.
Overall, the studies described here may help inform rationale structure-guided vaccine design and identify possible correlates of protection for lead therapeutic candidates against EEEV, and possibly other encephalitic alphaviruses.
Summary Various monoclonal antibodies with specificity to eastern equine encephalitis virus (EEEV) were generated and some show protective activity after aerosol challenge of mice with EEEV. Neutralizing and non-neutralizing antibodies have been shown to be protective in mouse models. The purpose of this study is to evaluate these antibodies in an EEEV peripheral challenge model.
C57BL/6 mice, challenged s.c. with the FL93-939 strain of EEEV demonstrate morbidity and mortality. The mice succumb to disease by around 9 days post-virus injection and show various signs of neurological disease. This model has been used to identify effective intervention strategies to prevent or treat infection. Survival, weight change, viremia and viral titer in the brain are used as disease parameters to determine the efficacy of treatment with antiviral agents.
Animals. 115 C57BL/6 mice supplied by Jackson Laboratories were used. Mice were assigned by weight to experimental groups and individually marked with ear tags.
Virus. Eastern equine encephalitis virus (strain FL93-939). A challenge dose of 103.3 CCID50 was administered via bilateral s.c. injections in a total volume of 0.2 mL. Test agent: rEEEV-33, rEEEV-143, rEEEV-106, rEEEV-27, rEEEV-21, EEEV-373, EEEV-352, EEEV-346, EEEV-138, EEEV-109, and rDENV-2D22 were provided by Vanderbilt University Medical Center for testing in the mouse model.
Infectious cell culture assay. Virus titer was quantified using an infectious cell culture assay where a specific volume of either tissue homogenate or serum was added to the first tube of a series of dilution tubes. Serial dilutions were made and added to Vero cells. Three days later cytopathic effect (CPE) was used to identify the end-point of infection. Four replicates were used to calculate the 50% cell culture infectious doses (CCID50) per mL of plasma or gram of tissues.
Experiment Design. Mice were challenged with EEEV via bilateral SC injections. Animals were treated with antibodies at doses of 10 mg/kg or 100 μg/kg via a single IP injection 24 hours post-virus challenge. Animals were monitored until 21 days post-virus inoculation (dpi) for disease signs and survival. Individual weights were recorded daily 0-10 dpi and on 14 and 18 dpi. Serum was collected from all mice 3 dpi for assessment of serum viremia.
Statistical analysis. Survival data were analyzed using the Wilcoxon log-rank survival analysis and all other statistical analyses were done using one-way ANOVA using a Bonferroni group comparison (Prism 5, GraphPad Software, Inc).
Ethics regulation of Laboratory animals. This study was conducted in accordance with the approval of the Institutional Animal Care and Use Committee of Utah State University (Protocol #10025). The work was done in the AAALAC-accredited Laboratory Animal Research Center of Utah State University. The U. S. Government (National Institutes of Health) approval was renewed 9 Mar. 2018 (PHS Assurance no. D16-00468) in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals (Revision; 2015).
Results and Discussion. Mice were infected with EEEV, followed by treatment 24 hours later. Ten antibodies were tested to verify in vivo efficacy. Animals were monitored for survival, weight change and viremia for 21 days after virus challenge.
Treatment with 7 of the 10 antibodies resulted in complete protection at a dose of 10 mg/kg administered as a single IP treatment 24 h after virus challenge (
Weight change curves correlated with morality, where groups that had mortality greater than or equal to 70% had average weight curves similar to the isotype control-treated group (
Virus titers were generally undetectable in groups treated with effective antibodies (
Conclusions. Treatment of EEEV-infected mice with rEEEV-33, rEEEV-143, rEEEV-106, rEEEV-27, rEEEV-21, EEEV-373, EEEV-352 and EEEV-109 resulted in significant improvement in all measured disease parameters and suggest these antibodies are effective in vivo against lethal EEEV. Further studies may investigate certain of these to determine minimal effective doses as well as efficacy of combination of antibodies that have different targets. Low or no efficacy was observed for EEEV-346 and EEEV-138, which in general were similar to treatment with the isotype control.
aMean day of death.
bDifference between weight on 0 and 6 days post-virus challenge representing maximal weight change within this study.
cSerum was collected 3 dpi. Values are mean virus titer ± SD.
All of the compositions and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this disclosure have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the disclosure. More specifically, it will be apparent that certain agents which are both chemically and physiologically related may be substituted for the agents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the disclosure as defined by the appended claims.
The following references, to the extent that they provide exemplary procedural or other details supplementary to those set forth herein, are specifically incorporated herein by reference.
The present application claims priority to U.S. Provisional Application Nos. 62/894,740, 62/896,382 and 62/933,735, filed Aug. 31, 2019, Sep. 5, 2019, and Nov. 11, 2019, respectively, the entire contents of each application being hereby incorporated by reference.
This invention was made with government support under grant number HDTRA1-13-1-0034 awarded by the Department of Defense. The government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/048708 | 8/31/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62933735 | Nov 2019 | US | |
| 62896382 | Sep 2019 | US | |
| 62894740 | Aug 2019 | US |
