Patent Application
20170360875
The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Dec. 17, 2015, is named 504.00030201_SL.txt and is 22,591 bytes in size.
Humoral immune responses are triggered when an antigen binds specifically to an antibody. The combination of an antibody molecule and an antigen forms a small, relatively soluble immune complex. Antigens either can be foreign substances, such as viral or bacterial polypeptides, or can be “self-antigens” such as polypeptides normally found in the human body. The immune system normally distinguishes foreign antigens from self-antigens. “Autoimmune” disease can occur, however, when this system breaks down, such that the immune system turns upon the body and destroys tissues or organ systems as if they were foreign substances. Larger immune complexes are more pathogenic than small, more soluble immune complexes. The formation of large, relatively insoluble immune complexes can result from both the interaction of antibody molecules with antigen and the interaction of antibody molecules with each other. Such immune complexes also can result from interactions between antibodies in the absence of antigen.
Antibodies can prevent infections by coating viruses or bacteria, but otherwise are relatively harmless by themselves. In contrast, organ specific tissue damage can occur when antibodies combine with antigens and the resulting immune complexes bind to certain effector molecules in the body. Effector molecules are so named because they carry out the pathogenic effects of immune complexes. By inhibiting the formation of large, insoluble immune complexes, or by inhibiting the binding of immune complexes to effector molecules, the tissue damaging effects of immune complexes may be prevented.
This document is based in part on the discovery that polypeptides having amino acid sequences based on those set forth in SEQ ID NO:2 and SEQ ID NO:20 (also referred to herein as NB406) can bind specifically and with high affinity to the CH2-CH3 domain of immunoglobulin molecules, thus inhibiting the formation of insoluble immune complexes containing antibodies and antigens, and preventing the binding of such complexes to effector molecules. This document provides such polypeptides, other CH2-CH3 binding compounds, compositions containing the polypeptides and/or compounds, and methods for using the polypeptides and compositions to inhibit immune complex formation and therapeutic use in treating viral infections.
In some embodiments, the polypeptides may inhibit or prevent the formation of an Fc receptor to an immune complex that includes an antibody and an antigen. That is, polypeptides may inhibit or prevent the binding of a protein that could otherwise bind to the Fc-portion of an antibody, including an antibody bound to an antigen, to the Fc-portion of the antibody.
In one aspect, this document features a method for inhibiting immune complex formation in a subject, the method comprising administering to the subject a composition comprising a purified polypeptide, the polypeptide comprising the amino acid sequence (Xaa1)m-Cys-Ala-Xaa2-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-(Xaa3)n (SEQ ID NO:60), wherein Xaa1 is any amino acid, Xaa2 is Trp, Tyr or Phe, 5-Hydroxytrphophan (5-HTP), 5-hydroxytryptamine (5-HT), or another amino acid derivative, Xaa3 is any amino acid, and m and n independently are 0, 1, 2, 3, 4, or 5, and wherein the immune complex formation is associated with a viral infection. The immune complex formation can be associated with Antibody Dependent Enhancement (ADE) of Ebola Fever or infection by Ebola Virus (EBOV), or contributes to the enhancement of an EBOV infection. The peptide can cause clinical or histiological improvement of an EBOV infection. The peptide can cause an improvement in or delay the onset of one or more of the histiological characteristics of an EBOV infection. The peptide can decrease the ADE of an EBOV infection. In some embodiments, the subject may have been diagnosed as having or may be suspected of having an EBOV infection. As used herein, the terms “EBOV infection” and “Ebola virus infection” are inclusive of Ebola Virus Disease (EVD) and the more severe manifestation of EVD, Ebola Hemorrhagic Fever (EHF). In one or more embodiments, the subject may be exhibiting symptoms of an EBOV infection, the subject may be at risk of contracting an EBOV infection, and/or the subject may have been exposed to EBOV infection. The EBOV may include, for example, Ebola virus Zaire (Zaire ebolavirus; ZEBOV); Sudan virus (Sudan ebolavirus; SUDV or SEBOV); Tai Forest virus (Taï Forest ebolavirus; TAFV); Bundibugyo virus (Bundibugyo ebolavirus; BDBV); or Reston virus (Reston ebolavirus; RESTV or REBOV). In one or more embodiments, the subject may be a human. Additionally, the subject may have or be suspected of having a coinfection with a pathogen other than EBOV including, for example, human immunodeficiency virus (HIV), human cytomegalovirus (HCMV), herpes simplex virus (HSV), hepatitis C virus, human papilloma virus (HPV), Mycobacterium tuberculosis, malaria/Plasmodium falciparum, and/or Schistosoma haematobium. In one or more embodiments, the subject may be a pig or non-human primate. Additionally, the subject may have or be suspected of having a coinfection with a pathogen other than EBOV including, for example porcine reproductive and respiratory syndrome virus (PRRSV).
In some embodiments, the subject may have been diagnosed as having or may be suspected of having an influenza virus infection. In one or more embodiments, the subject may be exhibiting symptoms of an influenza infection, the subject may be at risk of contracting an influenza infection, and/or the subject may have been exposed to influenza. Additionally, the subject may have or be suspected of having an autoimmune disease. In one or more embodiments, the subject may be a human.
In some embodiments where the subject has been diagnosed as having or is suspected of having an influenza virus infection and where immune complex formation contributes to the enhancement of the influenza virus infection, the method includes administering to the subject a composition including a purified polypeptide. The polypeptide can include the amino acid sequence Xaa-Pro-Pro-Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 19), wherein Xaa is any amino acid.
In some embodiments where the subject who has been diagnosed as having or is suspected of having a hepatitis virus infection and where immune complex formation contributes to the enhancement of the hepatitis virus infection, the method includes administering to the subject a composition including a purified polypeptide. The polypeptide can include the amino acid sequence Xaa-Pro-Pro-Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 19), wherein Xaa is any amino acid.
In some embodiments, the subject may have been diagnosed as having or may be suspected of having a hepatitis virus infection. In one or more embodiments, the subject may be exhibiting symptoms of a hepatitis infection, the subject may be at risk of contracting a hepatitis infection, and/or the subject may have been exposed to a hepatitis virus. Additionally, the subject may have or be suspected of having an autoimmune disease. In one or more embodiments, the subject may be a human.
The peptide can inhibit binding of a heterologous immune complex (IC), that is, a complex formed between a non-Ebola antibody and a non-Ebola antigen, to an FcγR. The peptide can inhibit binding of an EBOV-IgG IC, that is, an IC formed between an anti-Ebola antibody and an Ebola antigen, to an FcγR. The peptide can inhibit formation of ICs that contribute to immunopathogenesis of the ADE of EBOV infections. The peptide can inhibit binding of EBOV virions to IgG IC. The peptide can inhibit binding of an EBOV protein (e.g., glycoprotein (GP)) to an IgG immune complex. The peptide can inhibit binding of a heterologous IC and/or an EBOV-IgG IC to FcγI, FcγIIa H131 allele, FcγIIa R131 allele, FcγRIIb, Fc.γRIIc, FcγRIIIa, or FcγIIIb. The peptide can inhibit binding of a heterologous IC and/or EBOV-IgG IC to mC1q, sC1q, or FcRn.
The polypeptide can comprise a terminal stabilizing group. The terminal stabilizing group can be at the amino terminus of the polypeptide and can be a tripeptide having the amino acid sequence Xaa-Pro-Pro, wherein Xaa is any amino acid (e.g., Ala). The terminal stabilizing group can be at the carboxy terminus of the polypeptide and can be a tripeptide having the amino acid sequence Pro-Pro-Xaa, wherein Xaa is any amino acid (e.g., Ala).
The method can further comprise the step of monitoring the subject for one or more clinical, histiopathological or molecular characteristics of hemorrhagic fever, influenza virus infection, or hepatitis virus infection. The one or more clinical, histiopathological, or molecular characteristics of hemorrhagic fever can be selected from the group consisting of a decrease in platelets, hemoconcentration, or an increase in FcγR+ effector cells.
The polypeptide can comprise the amino acid sequence Xaa-Pro-Pro-Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 19), wherein Xaa is any amino acid. The polypeptide can comprise the amino acid sequence Ala-Pro-Pro-Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:20). The polypeptide can comprise the amino acid sequence Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:2).
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although methods and materials similar or equivalent to those described herein can be used to practice the invention, suitable methods and materials are described below.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims.
This document provides polypeptides and other compounds capable of interacting with the CH2-CH3 cleft of an immunoglobulin molecule, such that interaction of the immunoglobulin with other molecules (e.g., effectors or other immunoglobulins) is blocked. Methods for identifying such polypeptides and other compounds also are described, along with compositions and articles of manufacture containing the polypeptides and compounds. In addition, this document provides methods for using the polypeptides and compounds to inhibit immune complex formation and to treat diseases (e.g., viral diseases such as Ebola Virus Disease) in which IgG immune complexes bind to effector molecules, such as membrane bound C1q (mC1q), soluble C1q (sC1q), and FcγR5 (including, but not limited to FcγRI (and isoforms of FcγRs), FcγRIIa, FcγRIIb/c, FcγRIIIa, FcγRIIIb, and FcRn).
This document further provides methods of treating a subject diagnosed as having or suspected of having a hepatitis virus infection, an influenza virus infection, and/or an Ebola virus infection. Unexpectedly, and as further described in the Examples, Ebola virus, hepatitis virus, influenza virus and/or a surface protein of Ebola virus, hepatitis virus, and influenza virus can act as an Fc Receptor. The Fc receptor (FcR) activity of these viruses can facilitate interactions between the virus and a host cell receptor.
As used herein, an “Fc receptor” refers to a protein that can bind to the Fc-portion of an antibody, including an antibody bound to an antigen and/or an antibody that is not bound to an antigen. The Fc receptor (FcR) activity of these viruses can facilitate interactions between the virus and a host cell receptor. As used herein, an “immune complex” or “IC” refers both a complex between an immunoglobulin and an antigen and a complex between an immunoglobulin Fc region and other antibodies or factors. Specifically, an “Fc-mediated immune complex” refers to a complex between an immunoglobulin Fc region and other antibodies or factors including, for example, an Fc receptor. The Fc-mediated immune complex may, optionally, include bound antigen. As used herein, the terms “heterologous immune complex” and “heterologous IC” mean a complex formed between a non-Ebola antibody and a non-Ebola antigen.
An immunoglobulin that is bound to both a host cell Fc receptor and a viral Fc receptor can enhance binding and/or entry of a virus into to a host cells. Because the interaction between the host cell and the virus is facilitated by interactions with the Fc-portion of the antibody in an immunoglobulin complex, a heterologous immune complex, not just an anti-viral immune complex, can bridge a host cell-virus interaction. The previously unreported and surprising ability of hepatitis virus, influenza virus, and Ebola virus to interact with heterologous immune complexes may contribute to accelerated disease progression and increased infectivity, particularly in subjects having an increased number of circulating immune complexes.
By administering polypeptides and other compounds capable of interacting with the CH2-CH3 cleft of an immunoglobulin molecule, including, for example, SEQ ID NO: 19, SEQ ID NO:20, or SEQ ID NO:2, the interaction of the immunoglobulin with other molecules, including a host cell Fc receptor and/or a viral Fc receptor can be blocked or abrogated. When an immunoglobulin is part of an antibody-antigen immune complex, such abrogation can interfere with the immune complex's ability to bridge virus-host cell interactions.
The immunoglobulins make up a class of proteins found in plasma and other bodily fluids that exhibit antibody activity and bind to other molecules (e.g., antigens and certain cell surface receptors) with a high degree of specificity. Based on their structure and biological activity, immunoglobulins can be divided into five classes: IgM, IgG, IgA, IgD, and IgE. IgG is the most abundant antibody class in the body; this molecule assumes a twisted “Y” shape configuration. With the exception of the IgMs, immunoglobulins are composed mainly of four peptide chains that are linked by several intrachain and interchain disulfide bonds. For example, the IgGs are composed of two polypeptide heavy chains (H chains) and two polypeptide light chains (L chains), which are coupled by disulfide bonds and non-covalent bonds to form a protein molecule with a molecular weight of approximately 150,000 daltons (Saphire et al., “Crystal Structure of a Neutralizing Human IgG Against HIV-1: A Template for Vaccine Design,” Science, 2001, 293:1155-1159). The average IgG molecule contains approximately 4.5 interchain disulfide bonds and approximately 12 intrachain disulfide bonds (Frangione and Milstein (1968) J. Mol. Biol. 33:893-906).
The light and heavy chains of immunoglobulin molecules are composed of constant regions and variable regions (see, e.g., Padlan (1994) Mol. Immunol. 31:169-217). For example, the light chains of an IgG1 molecule each contain a variable domain (VL) and a constant domain (CL). The heavy chains each have four domains: an amino terminal variable domain (VH), followed by three constant domains (CH1, CH2, and the carboxy terminal CH3). A hinge region corresponds to a flexible junction between the CH1 and CH2 domains. Papain digestion of an intact IgG molecule results in proteolytic cleavage at the hinge and produces an Fc fragment that contains the CH2 and CH3 domains, and two identical Fab fragments that each contain a CH1, CL, VH, and VL domain. The Fc fragment has complement- and tissue-binding activity, while the Fab fragments have antigen-binding activity.
Immunoglobulin molecules can interact with other polypeptides through various regions. The majority of antigen binding, for example, occurs through the VL/VH region of the Fab fragment. The hinge region also is thought to be important, as immunological dogma states that the binding sites for Fc receptors (FcR) are found in the hinge region of IgG molecules (see, e.g., Raghavan and Bjorkman (1996) Annu. Rev. Dev. Biol. 12:181-200). More recent evidence, however, suggests that FcR interacts with the hinge region primarily when the immunoglobulin is monomeric (i.e., not immune-complexed). Such interactions typically involve the amino acids at positions 234-237 of the Ig molecule (Wiens et al. (2000) J. Immunol. 164:5313-5318).
Immunoglobulin molecules also can interact with other polypeptides through a cleft within the CH2-CH3 domain. The “CH2-CH3 cleft” typically includes the amino acids at positions 251-255 within the CH2 domain and the amino acids at positions 424-436 within the CH3domain. As used herein, numbering is with respect to an intact IgG molecule as in Kabat et al. (Sequences of Proteins of Immunological Interest, 5th ed., Public Health Service, U.S. Department of Health and Human Services, Bethesda, Md.). The corresponding amino acids in other immunoglobulin classes can be readily determined by those of ordinary skill in the art.
The CH2-CH3 cleft is unusual in that it is characterized by both a high degree of solvent accessibility and a predominantly hydrophobic character, suggesting that burial of an exposed hydrophobic surface is an important driving force behind binding at this site. A three-dimensional change occurs at the IgG CH2-CH3 cleft upon antigen binding, allowing certain residues (e.g., a histidine at position 435) to become exposed and available for binding. Direct evidence of three-dimensional structural changes that occur upon antigen binding was found in a study using monoclonal antibodies sensitive to conformational changes in the Fc region of human IgG. Five IgG epitopes were altered by antigen binding: two within the hinge region and three within the CH2-CH3 cleft (Girkontraite et al. (1996) Cancer Biother. Radiopharm. 11:87-96). Antigen binding therefore can be important for determining whether an immunoglobulin binds to other molecules through the hinge or the Fc CH2-CH3 region.
The Fc region can bind to a number of effector molecules and other proteins, including the following:
The formation of immune complexes via interactions between immunoglobulin Fc regions and other antibodies or other factors (e.g., those described above) is referred to herein as “Fc-mediated immune complex formation” or “the Fc-mediated formation of an immune complex.” Immune complexes containing such interactions are termed “Fc-mediated immune complexes.” Fc-mediated immune complexes can include immunoglobulin molecules with or without bound antigen, and typically include CH2-CH3 cleft-specific ligands that have higher binding affinity for immune complexed antibodies than for monomeric antibodies.
As used herein, a “polypeptide” is any chain of amino acid residues, regardless of post-translational modification (e.g., phosphorylation or glycosylation). The polypeptides provided herein typically are between 10 and 50 amino acids in length (e.g., 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, or 50 amino acids in length). Polypeptides that are between 10 and 20 amino acids in length (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 amino acids in length) can be particularly useful.
The amino acid sequences of the polypeptides provided herein are somewhat constrained, but can have some variability. For example, the polypeptides provided herein typically include the amino acid sequence Xaa1-Cys-Ala-Xaa2-His-Xaa3-Xaa4-Xaa5-Leu-Val-Trp-Cys-Xaa6 (SEQ ID NO: 1), wherein the residues denoted by Xaan can display variability. For example, Xaa1 can be absent or can be any amino acid (e.g., Arg or Asp). Xaa2 can be Phe, Tyr, Trp, 5-Hydroxytryptophan (5-HTP), or Arg. Xaa3 can be any amino acid. Xaa4 can be Gly or Ala, while Xaa5 can be Glu or Ala. Like Xaa1, Xaa6 also can be absent or can be any amino acid (SEQ ID NO:57).
In one embodiment, a polypeptide can include the amino acid sequence Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:2). Alternatively, a polypeptide can include the amino acid sequence Asp-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:3) or Asp-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:4). In another embodiment, a polypeptide can include the amino acid sequence Arg-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:5), Arg-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:6), or Arg-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:7).
In another embodiment, a polypeptide can include the amino acid sequence Cys-Ala-Xaa-His-Leu-Gly-Glu-Leu-Val-Trp-Cys (SEQ ID NO:8), in which Xaa can be Phe, Tyr, Trp, or Arg. For example, this document provides polypeptides that include the following amino acid sequences: Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:9), Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 10), and Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 11).
The polypeptides provided herein can be modified for use in vivo by the addition, at the amino- or carboxy-terminal end, of a stabilizing agent to facilitate survival of the polypeptide in vivo. This can be useful in situations in which peptide termini tend to be degraded by proteases prior to cellular uptake. Such blocking agents can include, without limitation, additional related or unrelated peptide sequences that can be attached to the amino- and/or carboxy-terminal residues of the polypeptide (e.g., an acetyl group attached to the N-terminal amino acid or an amide group attached to the C-terminal amino acid). Such attachment can be achieved either chemically, during the synthesis of the polypeptide, or by recombinant DNA technology using methods familiar to those of ordinary skill in the art. Alternatively, blocking agents such as pyroglutamic acid or other molecules known in the art can be attached to the amino- and/or carboxy-terminal residues, or the amino group at the amino terminus or the carboxy group at the carboxy terminus can be replaced with a different moiety.
A proline or an Xaa-Pro-Pro (e.g., Ala-Pro-Pro) sequence at the amino terminus can be particularly useful (see, e.g., WO 00/22112). For example, a polypeptide can include the amino acid sequence Xaa1-Pro-Pro-Cys-Ala-Xaa2-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 12), where Xaa1 is any amino acid (e.g., Ala), and Xaa2 is Trp, Tyr, Phe, or Arg. For example, a polypeptide can include the amino acid sequence Xaa-Pro-Pro-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 13), Ala-Pro-Pro-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 14), Xaa-Pro-Pro-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 15), Ala-Pro-Pro-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 16), Xaa-Pro-Pro-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 17), or Ala-Pro-Pro-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:18). Alternatively, a polypeptide can include the amino acid sequence Xaa-Pro-Pro-Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 19), Ala-Pro-Pro-Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:20), Xaa-Pro-Pro-Asp-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:21), Ala-Pro-Pro-Asp-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:22), Xaa-Pro-Pro-Asp-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:23), Ala-Pro-Pro-Asp-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:24), Xaa-Pro-Pro-Arg-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:25), Ala-Pro-Pro-Arg-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:26), Xaa-Pro-Pro-Arg-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:27), Ala-Pro-Pro-Arg-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:28), Xaa-Pro-Pro-Arg-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:29), or Ala-Pro-Pro-Arg-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:30), wherein Xaa at the first position is any amino acid.
The polypeptides provided herein can have a Pro-Pro-Xaa (e.g., Pro-Pro-Ala) sequence at their carboxy termini. For example, a polypeptide can include the amino acid sequence Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Xaa (SEQ ID NO:31), Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Ala (SEQ ID NO:32), Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Xaa (SEQ ID NO:33), Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Ala (SEQ ID NO:34), Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Xaa (SEQ ID NO:35), Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Ala (SEQ ID NO:36), Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Xaa (SEQ ID NO:37), Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Ala (SEQ ID NO:38), Asp-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Xaa (SEQ ID NO:39), Asp-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Ala (SEQ ID NO:40), Asp-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Xaa (SEQ ID NO:41), Asp-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Ala (SEQ ID NO:42), Arg-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Xaa (SEQ ID NO:43), Arg-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Ala (SEQ ID NO:44), Arg-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Xaa (SEQ ID NO:45), Arg-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Ala (SEQ ID NO:46), Arg-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Xaa (SEQ ID NO:47), or Arg-Cys-Ala-Phe-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Pro-Pro-Ala (SEQ ID NO:48), wherein Xaa can be any amino acid.
In some embodiments, the polypeptides provided herein can include additional amino acid sequences at the amino terminus of the sequence set forth in SEQ ID NO: 1, the carboxy terminus of the sequence set forth in SEQ ID NO: 1, or both. For example, a polypeptide can contain the amino acid sequence Trp-Glu-Ala-Xaa1-Cys-Ala-Xaa2-His-Xaa3-Xaa4-Xaa5-Leu-Val-Trp-Cys-Xaa6-Lys-Val-Glu-Glu (SEQ ID NO:49), wherein the residues denoted by Xaan can display variability. As for the amino acid sequence set forth in SEQ ID NO:49, Xaa1 can be absent or can be any amino acid (e.g., Arg or Asp); Xaa2 can be Phe, Tyr, 5-HTP, Trp, or Arg; Xaa3 can be any amino acid; Xaa4 can be Gly or Ala; Xaa5 can be Glu or Ala; and Xaa6 can be absent or can be any amino acid (SEQ ID NO:58). In one embodiment, a polypeptide can include the amino acid sequence Trp-Glu-Ala-Asp-Cys-Ala-Xaa-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Lys-Val-Glu-Glu (SEQ ID NO:50), where Xaa is Arg, Trp, 5-HTP, Tyr, or Phe. For example, a polypeptide can include the amino acid sequence Trp-Glu-Ala-Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Lys-Val-Glu-Glu (SEQ ID NO:51).
In another embodiment, a polypeptide can consist of the amino acid sequence (Xaa1)m-Xaa2-Cys-Ala-Xaa3-His-Xaa4-Xaa5-Xaa6-Leu-Val-Trp-Cys-(Xaa7)n (SEQ ID NO:52), wherein the residues denoted by Xaa can display variability, and m and n can be, independently, integers from 0 to 10 (e.g., 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10). For example, Xaa1 can be any amino acid; Xaa2 can be absent or can be any amino acid (e.g., Arg or Asp); Xaa3 can be Phe, Tyr, 5-HTP, Trp, or Arg; Xaa4 can be any amino acid; Xaa5 can be Gly or Ala; Xaa6 can be Glu or Ala; Xaa7 can be any amino acid; and m and n can be from 0 to 5 (e.g., 0, 1, 2, 3, 4, or 5) (SEQ ID NO:59). Alternatively, a polypeptide can consist of the amino acid sequence (Xaa1)m-Cys-Ala-Xaa2-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-(Xaa3)n(SEQ ID NO:53), wherein Xaa1 is any amino acid, Xaa2 is Phe or Arg, Xaa3 is any amino acid, and m and n are, independently, integers from 0 to 5 (e.g., 0, 1, 2, 3, 4, or 5). Examples of polypeptides within these embodiments, without limitation, include polypeptides consisting of the amino acid sequence Ala-Ala-Ala-Ala-Ala-Asp-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Ala-A-la-Ala-Ala-Ala (SEQ ID NO:54), Ala-Ala-Arg-Cys-Ala-Arg-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Ala-Ala (SEQ ID NO:55), or Ala-Ala-Ala-Asp-Cys-Ala-Phe-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr-Ala-A-la (SEQ ID NO:56).
The amino acid sequences of the polypeptides described herein typically contain two cysteine residues. Polypeptides containing these amino acid sequences can cyclize due to formation of a disulfide bond between the two cysteine residues. A person having ordinary skill in the art can, for example, use Ellman's Reagent to determine whether a peptide containing multiple cysteine residues is cyclized. In some embodiments, these cysteine residues can be substituted with other natural or non-natural amino acid residues that can form lactam bonds rather than disulfide bonds. For example, one cysteine residue could be replaced with aspartic acid or glutamic acid, while the other could be replaced with ornithine or lysine. Any of these combinations could yield a lactam bridge. By varying the amino acids that form a lactam bridge, a polypeptide provided herein can be generated that contains a bridge approximately equal in length to the disulfide bond that would be formed if two cysteine residues were present in the polypeptide.
The polypeptides provided herein can contain an amino acid tag. A “tag” is generally a short amino acid sequence that provides a ready means of detection or purification through interactions with an antibody against the tag or through other compounds or molecules that recognize the tag. For example, tags such as c-myc, hemagglutinin, polyhistidine, or FLAG.® (an eight amino acid peptide tag; Sigma-Aldrich Corp., St. Louis, Mo.) can be used to aid purification and detection of a polypeptide. As an example, a polypeptide with a polyhistidine tag can be purified based on the affinity of histidine residues for nickel ions (e.g., on a Ni—NTA column), and can be detected in western blots by an antibody against polyhistidine (e.g., the Penta-His antibody; Qiagen, Valencia, Calif.). Tags can be inserted anywhere within the polypeptide sequence, although insertion at the amino- or carboxy-terminus is particularly useful.
The term “amino acid” refers to natural amino acids, unnatural amino acids, and amino acid analogs, all in their D and L stereoisomers if their structures so allow. Natural amino acids include alanine (Ala), arginine (Arg), asparagine (Asn), aspartic acid (Asp), cysteine (Cys), glutamine (Gln), glutamic acid (Glu), glycine (Gly), histidine (His), isoleucine (Ile), leucine (Leu), lysine (Lys), methionine (Met), phenylalanine (Phe), proline (Pro), serine (Ser), threonine (Thr), tryptophan (Trp), tyrosine (Tyr), and valine (Val). Unnatural amino acids include, but are not limited to 5-Hydroxytryptophan, azetidinecarboxylic acid, 2-aminoadipic acid, 3-aminoadipic acid, beta-alanine, aminopropionic acid, 2-aminobutyric acid, 4-aminobutyric acid, 6-aminocaproic acid, 2-aminoheptanoic acid, 2-aminoisobutyric acid, 3-aminoisobutyric acid, 2-aminopimelic acid, 2,4-diaminoisobutyric acid, desmosine, 2,2′-diaminopimelic acid, 2,3-diaminopropionic acid, N-ethylglycine, N-ethylasparagine, hydroxylysine, allo-hydroxylysine, 3-hydroxyproline, 4-hydroxyproline, isodesmosine, allo-isoleucine, N-methylglycine, N-methylisoleucine, N-methylvaline, norvaline, norleucine, ornithine, and pipecolic acid.
An “analog” is a chemical compound that is structurally similar to another but differs slightly in composition (as in the replacement of one atom by an atom of a different element or in the presence of a particular functional group). An “amino acid analog” therefore is structurally similar to a naturally occurring amino acid molecule as is typically found in native polypeptides, but differs in composition such that either the C-terminal carboxy group, the N-terminal amino group, or the side-chain functional group has been chemically modified to another functional group. Amino acid analogs include natural and unnatural amino acids which are chemically blocked, reversibly or irreversibly, or modified on their N-terminal amino group or their side-chain groups, and include, for example, methionine sulfoxide, methionine sulfone, S-(carboxymethyl)-cysteine, S-(carboxymethyl)-cysteine sulfoxide and S-(carboxymethyl)-cysteine sulfone. Amino acid analogs may be naturally occurring, or can be synthetically prepared. Non-limiting examples of amino acid analogs include 5-Hydroxytryptophan (5-HTP), aspartic acid-(beta-methyl ester), an analog of aspartic acid; N-ethylglycine, an analog of glycine; and alanine carboxamide, an analog of alanine Other examples of amino acids and amino acids analogs are listed in Gross and Meienhofer, The Peptides: Analysis, Synthesis, Biology, Academic Press, Inc., New York (1983).
The stereochemistry of a polypeptide can be described in terms of the topochemical arrangement of the side chains of the amino acid residues about the polypeptide backbone, which is defined by the peptide bonds between the amino acid residues and the α-carbon atoms of the bonded residues. In addition, polypeptide backbones have distinct termini and thus direction. The majority of naturally occurring amino acids are L-amino acids. Naturally occurring polypeptides are largely comprised of L-amino acids.
D-amino acids are the enantiomers of L-amino acids and can form peptides that are herein referred to as “inverso” polypeptides (i.e., peptides corresponding to native peptides but made up of D-amino acids rather than L-amino acids). A “retro” polypeptide is made up of L-amino acids, but has an amino acid sequence in which the amino acid residues are assembled in the opposite direction of the native peptide sequence.
“Retro-inverso” modification of naturally occurring polypeptides involves the synthetic assembly of amino acids with α-carbon stereochemistry opposite to that of the corresponding L-amino acids (i.e., D- or D-allo-amino acids), in reverse order with respect to the native polypeptide sequence. A retro-inverso analog thus has reversed termini and reversed direction of peptide bonds, while approximately maintaining the topology of the side chains as in the native peptide sequence. The term “native” refers to any sequence of L-amino acids used as a starting sequence for the preparation of partial or complete retro, inverso or retro-inverso analogs.
Partial retro-inverso polypeptide analogs are polypeptides in which only part of the sequence is reversed and replaced with enantiomeric amino acid residues. Since the retro-inverted portion of such an analog has reversed amino and carboxyl termini, the amino acid residues flanking the retro-inverted portion can be replaced by side-chain-analogous α-substituted geminal-diaminomethanes and malonates, respectively. Alternatively, a polypeptide can be a complete retro-inverso analog, in which the entire sequence is reversed and replaced with D-amino acids.
This document also provides peptidomimetic compounds that are designed on the basis of the amino acid sequences of polypeptides. Peptidomimetic compounds are synthetic, non-peptide compounds having a three-dimensional conformation (i.e., a “peptide motif,”) that is substantially the same as the three-dimensional conformation of a selected peptide, and can thus confer the same or similar function as the selected peptide. Peptidomimetic compounds can be designed to mimic any of the polypeptides provided herein.
Peptidomimetic compounds that are protease resistant are particularly useful. Furthermore, peptidomimetic compounds may have additional characteristics that enhance therapeutic utility, such as increased cell permeability and prolonged biological half-life. Such compounds typically have a backbone that is partially or completely non-peptide, but with side groups that are identical or similar to the side groups of the amino acid residues that occur in the peptide upon which the peptidomimetic compound is based. Several types of chemical bonds (e.g., ester, thioester, thioamide, retroamide, reduced carbonyl, dimethylene and ketomethylene) are known in the art to be useful substitutes for peptide bonds in the construction of peptidomimetic compounds.
The interactions between a polypeptide as described herein and an immunoglobulin molecule typically occur through the CH2-CH3 cleft of the immunoglobulin. Such interactions are engendered through physical proximity and are mediated by, for example, hydrophobic interactions. The “binding affinity” of a polypeptide for an immunoglobulin molecule refers to the strength of the interaction between the polypeptide and the immunoglobulin. Binding affinity typically is expressed as an equilibrium dissociation constant (Kd), which is calculated as Kd=koff/kon, where koff=the kinetic dissociation constant of the reaction, and kon=the kinetic association constant of the reaction. Kd is expressed as a concentration, with a low Kd value (e.g., less than 100 nM) signifying high affinity. Polypeptides that can interact with an immunoglobulin molecule typically have a binding affinity of at least 1 LM (e.g., at least 500 nM, at least 100 nM, at least 50 nM, or at least 10 nM) for the CH2-CH3 cleft of the immunoglobulin.
Polypeptides provided herein can bind with substantially equivalent affinity to immunoglobulin molecules that are bound by antigen and to monomeric immunoglobulins. Alternatively, the polypeptides described herein can have a higher binding affinity (e.g., at least 10-fold, at least 100-fold, or at least 1000-fold higher binding affinity) for immunoglobulin molecules that are bound by antigen than for monomeric immunoglobulins. Conformational changes that occur within the Fc region of an immunoglobulin molecule upon antigen binding to the Fab region are likely involved in a difference in affinity. The crystal structures of bound and unbound NC6.8 Fab (from a murine monoclonal antibody) showed that the tail of the Fab heavy chain was displaced by 19 angstroms in crystals of the antigen/antibody complex, as compared to its position in unbound Fab (Guddat et al. (1994) J. Mol. Biol. 236-247-274). Since the C-terminal tail of the Fab region is connected to the Fc region in an intact antibody, this shift would be expected to affect the conformation of the CH2-CH3 cleft. Furthermore, examination of several three-dimensional structures of intact immunoglobulins revealed a direct physical connection between the Fab heavy chain and the Fc CH2-CH3 (Harris et al. (1997) Biochemistry 36:1581-1597; Saphire et al. (2001) Science 293:1155-1159).
Molecular modeling of the CH2-CH3 cleft of monomeric (i.e., unbound) and immune-complexed IgG reveal that the monomeric Fc CH2-CH3 cleft has a closed configuration, which can prevent binding to critical amino acid residues (e.g., H is 435; see, for example, O'Brien et al. (1994) Arch. Biochem. Biophys. 310:25-31; Jefferies et al. (1984) Immunol. Lett. 7:191-194; and West et al. (2000) Biochemistry 39:9698-9708). Immune-complexed (antigen-bound) IgG, however, has a more open configuration and thus is more conducive to ligand binding. The binding affinity of RF for immune-complexed IgG, for example, is much greater than the binding affinity of RF for monomeric IgG (Corper et al. (1997) Nat. Struct. Biol. 4:374; Sohi et al. (1996) Immunol. 88:636). The same typically is true for the polypeptides provided herein.
Because the polypeptides described herein can bind to the CH2-CH3 cleft of immunoglobulin molecules, they can be useful for blocking the interaction of other factors (e.g., FcRn, FcR, C1q, histones, MBP, SOD1 and other immunoglobulins) to the Fc region of the immunoglobulin, and thus can inhibit Fc-mediated immune complex formation. By “inhibit” is meant that Fc-mediated immune complex formation is reduced in the presence of a polypeptide provided herein, as compared to the level of immune complex formation in the absence of the polypeptide. Such inhibiting can occur in vitro (e.g., in a test tube) or in vivo (e.g., in an individual). Any suitable method can be used to assess the level of immune complex formation. Many such methods are known in the art, and some of these are described herein.
The polypeptides described herein typically interact with the CH2-CH3 cleft of an immunoglobulin molecule in a monomeric fashion (i.e., interact with only one immunoglobulin molecule and thus do not link two or more immunoglobulin molecules together) with a 1:2 IgG Fc to peptide stoichiometry. Interactions with other immunoglobulin molecules through the Fc region therefore are precluded by the presence of the polypeptide. The inhibition of Fc-mediated immune complex formation can be assessed in vitro, for example, by incubating an IgG molecule with a labeled immunoglobulin molecule (e.g., a fluorescently or enzyme (ELISA) labeled Fc Receptor or C1q in the presence and absence of a polypeptide, and measuring the amount of labeled immunoglobulin that is incorporated into an immune complex. Other methods suitable for detecting immune complex formation also may be used, as discussed below.
Polypeptides can be produced by a number of methods, many of which are well known in the art. By way of example and not limitation, a polypeptide can be obtained by extraction from a natural source (e.g., from isolated cells, tissues or bodily fluids), by expression of a recombinant nucleic acid encoding the polypeptide (as, for example, described below), or by chemical synthesis (e.g., by solid-phase synthesis or other methods well known in the art, including synthesis with an ABI peptide synthesizer; Applied Biosystems, Foster City, Calif.). Methods for synthesizing retro-inverso polypeptide analogs (Bonelli et al. (1984) Int. J. Peptide Protein Res. 24:553-556; and Verdini and Viscomi (1985) J. Chem. Soc. Perkin Trans. 1:697-701), and some processes for the solid-phase synthesis of partial retro-inverso peptide analogs also have been described (see, for example, European Patent number EP0097994).
This document provides isolated nucleic acid molecules encoding the polypeptides described herein. As used herein, “nucleic acid” refers to both RNA and DNA, including cDNA, genomic DNA, and synthetic (e.g., chemically synthesized) DNA. The nucleic acid can be double-stranded or single-stranded (i.e., a sense or an antisense single strand). The term “isolated” as used herein with reference to a nucleic acid refers to a naturally-occurring nucleic acid that is not immediately contiguous with both of the sequences with which it is immediately contiguous (one at the 5′ end and one at the 3′ end) in the naturally-occurring genome of the organism from which it is derived. The term “isolated” as used herein with respect to nucleic acids also includes any non-naturally-occurring nucleic acid sequence, since such non-naturally-occurring sequences are not found in nature and do not have immediately contiguous sequences in a naturally-occurring genome.
An isolated nucleic acid can be, for example, a DNA molecule, provided one of the nucleic acid sequences that is normally immediately contiguous with the DNA molecule in a naturally-occurring genome is removed or absent. Thus, an isolated nucleic acid includes, without limitation, a DNA molecule that exists as a separate molecule (e.g., a chemically synthesized nucleic acid, or a cDNA or genomic DNA fragment produced by PCR or restriction endonuclease treatment) independent of other sequences as well as DNA that is incorporated into a vector, an autonomously replicating plasmid, a virus (e.g., a retrovirus, lentivirus, adenovirus, or herpes virus), or into the genomic DNA of a prokaryote or eukaryote. In addition, an isolated nucleic acid can include an engineered nucleic acid such as a recombinant DNA molecule that is part of a hybrid or fusion nucleic acid. A nucleic acid existing among hundreds to millions of other nucleic acids within, for example, cDNA libraries or genomic libraries, or gel slices containing a genomic DNA restriction digest, is not considered an isolated nucleic acid.
This document also provides vectors containing the nucleic acids described herein. As used herein, a “vector” is a replicon, such as a plasmid, phage, or cosmid, into which another DNA segment may be inserted so as to bring about the replication of the inserted segment. Polypeptides can be developed using phage display, for example. Methods well known to those skilled in the art may use phage display to develop the polypeptides described herein. The vectors can be, for example, expression vectors in which the nucleotides encode the polypeptides provided herein with an initiator methionine, operably linked to expression control sequences. As used herein, “operably linked” means incorporated into a genetic construct so that expression control sequences effectively control expression of a coding sequence of interest. An “expression control sequence” is a DNA sequence that controls and regulates the transcription and translation of another DNA sequence, and an “expression vector” is a vector that includes expression control sequences, so that a relevant DNA segment incorporated into the vector is transcribed and translated. A coding sequence is “operably linked” and “under the control” of transcriptional and translational control sequences in a cell when RNA polymerase transcribes the coding sequence into mRNA, which then is translated into the protein encoded by the coding sequence.
Methods well known to those skilled in the art may be used to subclone isolated nucleic acid molecules encoding polypeptides of interest into expression vectors containing relevant coding sequences and appropriate transcriptional/translational control signals. See, for example, Sambrook et al., Molecular Cloning: A Laboratory Manual (2nd edition), Cold Spring Harbor Laboratory, New York (1989); and Ausubel et al., Current Protocols in Molecular Biology, Green Publishing Associates and Wiley Interscience, New York (1989). Expression vectors can be used in a variety of systems (e.g., bacteria, yeast, insect cells, and mammalian cells), as described herein. Examples of suitable expression vectors include, without limitation, plasmids and viral vectors derived from, for example, herpes viruses, retroviruses, vaccinia viruses, adenoviruses, and adeno-associated viruses. A wide variety of suitable expression vectors and systems are commercially available, including the pET series of bacterial expression vectors (Novagen, Madison, Wis.), the Adeno-X expression system (Clontech), the Baculogold baculovirus expression system (BD Biosciences Pharmingen, San Diego, Calif.), and the pCMV-Tag vectors (Stratagene, La Jolla, Calif.).
Expression vectors that encode the polypeptides described herein can be used to produce the polypeptides. Expression systems that can be used for small or large scale production of polypeptides include, without limitation, microorganisms such as bacteria (e.g., E. coli and B. subtilis) transformed with recombinant bacteriophage DNA, plasmid DNA, or cosmid DNA expression vectors containing the nucleic acid molecules provided herein; yeast (e.g., S. cerevisiae) transformed with recombinant yeast expression vectors containing the nucleic acid molecules of the invention; insect cell systems infected with recombinant virus expression vectors (e.g., baculovirus) containing the nucleic acid molecules provided herein; plant cell systems infected with recombinant virus expression vectors (e.g., tobacco mosaic virus) or transformed with recombinant plasmid expression vectors (e.g., Ti plasmid) containing the nucleic acid molecules provided herein; or mammalian cell systems (e.g., primary cells or immortalized cell lines such as COS cells, CHO cells, HeLa cells, HEK 293 cells, and 3T3 L1 cells) harboring recombinant expression constructs containing promoters derived from the genome of mammalian cells (e.g., the metallothionein promoter) or from mammalian viruses (e.g., the adenovirus late promoter and the cytomegalovirus promoter), along with the nucleic acids provided herein.
The term “purified polypeptide” as used herein refers to a polypeptide that either has no naturally occurring counterpart (e.g., a peptidomimetic), or has been chemically synthesized and is thus uncontaminated by other polypeptides, or that has been separated or purified from other cellular components by which it is naturally accompanied (e.g., other cellular proteins, polynucleotides, or cellular components). Typically, the polypeptide is considered “purified” when it is at least 70%, by dry weight, free from the proteins and naturally occurring organic molecules with which it naturally associates. A preparation of purified polypeptide therefore can be, for example, at least 80%, at least 90%, or at least 99%, by dry weight, the polypeptide. Suitable methods for purifying polypeptides can include, for example, affinity chromatography, immunoprecipitation, size exclusion chromatography, and ion exchange chromatography. The extent of purification can be measured by any appropriate method, including but not limited to: column chromatography, polyacrylamide gel electrophoresis, or high-performance liquid chromatography.
This document provides methods for designing, modeling, and identifying compounds that can bind to the CH2-CH3 cleft of an immunoglobulin molecule and thus serve as inhibitors of Fc-mediated immune complex formation. Such compounds also are referred to herein as “ligands.” Compounds designed, modeled, and identified by these methods typically can interact with an immunoglobulin molecule through the CH2-CH3 cleft, and typically have a binding affinity of at least 1 μM (e.g., at least 500 nM, at least 100 nM, at least 50 nM, or at least 10 nM) for the CH2-CH3 cleft of the immunoglobulin. Such compounds generally have higher binding affinity (e.g., at least 10-fold, at least 100-fold, or at least 1000-fold higher binding affinity) for immune-complexed immunoglobulin molecules than for monomeric immunoglobulin molecules.
Compounds typically interact with the CH2-CH3 cleft of an immunoglobulin molecule in a monomeric fashion (i.e., interact with only one immunoglobulin molecule and thus do not link two or more immunoglobulin molecules together). The interactions between a compound and an immunoglobulin molecule typically involve the amino acid residues at positions 252, 253, 435, and 436 of the immunoglobulin (number according to Kabat, supra). For example, SEQ ID NO:20 (NB406) may have hydrophobic packing with IgG Fc Met-252, Ile-253, Ser-254, His-435 and Tyr-436 (e.g., the indole ring of Trp-14 in SEQ ID NO:20 can have a hydrophobic interaction with IgG Fc His-435). Alanine substitution of IgG Fc Asn-434, His-435 or Tyr-436 can disrupt binding (ΔΔG≧1.5 kcal/mol). In addition, alanine substitution of SEQ ID NO:20 Val-13 or Trp-14 can result in disruption of binding (ΔΔG≧2.0 kcal/mol).
The interaction between compounds and the CH2-CH3 cleft renders the compounds capable of inhibiting the Fc-mediated formation of immune complexes by blocking the binding of other factors (e.g., Fc:Fc interactions, FcγRs, FcRn, histones, MBP, MOG, RF, Tau protein, α-synuclein, SOD 1, TNF and C1q) to the CH2-CH3 cleft.
Compounds identified by the methods provided herein can be polypeptides such as, for example, those described herein. Alternatively, a compound can be any suitable type of molecule that can specifically bind to the CH2-CH3 cleft of an immunoglobulin molecule.
By “modeling” is meant quantitative and/or qualitative analysis of receptor-ligand structure/function based on three-dimensional structural information and receptor-ligand interaction models. This includes conventional numeric-based molecular dynamic and energy minimization models, interactive computer graphic models, modified molecular mechanics models, distance geometry and other structure-based constraint models. Modeling typically is performed using a computer and may be further optimized using known methods.
Methods of designing ligands that bind specifically (i.e., with high affinity) to the CH2-CH3 cleft of an immunoglobulin molecule having bound antigen typically are computer-based, and involve the use of a computer having a program capable of generating an atomic model. Computer programs that use X-ray crystallography data are particularly useful for designing ligands that can interact with an Fc CH2-CH3 cleft. Programs such as RasMol, for example, can be used to generate a three dimensional model of a CH2-CH3 cleft and/or determine the structures involved in ligand binding. Computer programs such as INSIGHT (Accelrys, Burlington, Mass.), GRASP (Anthony Nicholls, Columbia University), Dock (Molecular Design Institute, University of California at San Francisco), and Auto-Dock (Accelrys) allow for further manipulation and the ability to introduce new structures.
Methods can include, for example, providing to a computer the atomic structural coordinates for amino acid residues within the CH2-CH3 cleft (e.g., amino acid residues at positions 252, 253, 435, and 436 of the cleft) of an immunoglobulin molecule in an Fc-mediated immune complex, using the computer to generate an atomic model of the CH2-CH3 cleft, further providing the atomic structural coordinates of a candidate compound and generating an atomic model of the compound optimally positioned within the CH2-CH3 cleft, and identifying the candidate compound as a ligand of interest if the compound interacts with the amino acid residues at positions 252, 253, 435, and 436 of the cleft. The data provided to the computer also can include the atomic coordinates of amino acid residues at positions in addition to 252, 253, 435, and 436. By “optimally positioned” is meant positioned to optimize hydrophobic interactions between the candidate compound and the amino acid residues at positions 252, 253, 435, and 436 of the CH2-CH3 cleft.
Alternatively, a method for designing a ligand having specific binding affinity for the CH2-CH3 cleft of an immunoglobulin molecule can utilize a computer with an atomic model of the cleft stored in its memory. The atomic coordinates of a candidate compound then can be provided to the computer, and an atomic model of the candidate compound optimally positioned can be generated. As described herein, a candidate compound can be identified as a ligand having specific binding affinity for the CH2-CH3 cleft of an immunoglobulin molecule if, for example, the compound interacts with the amino acid residues at positions 252, 253, 435, and 436 of the cleft.
Such methods have shown that monomeric (non-antigen bound) IgG Fc binds at a site distinct from the IgG Fc CH2-CH3 cleft, such as the lower hinge region (Wines et al. (2000) J. Immunol. 164:5313-5318), while immune complexed (antigen bound) IgG Fc binding to FcγIIa is inhibited by an IgM rheumatoid factor (RF-AN), which has been shown by 3D structure to only bind to the IgG Fc CH2-CH3 interface cleft (Sohi et al. (1996) Immunology 88:636-641; and Corper et al. (1997) Nature Struct. Biol. 4(5):374-381). Soluble FcγIIa inhibits the binding of immune complexed (but not monomeric, non-immune complexed) IgG Fc to RF-AN (Wines et al. (2003) Immunol. 109:246-254), and inhibitors that bind to the IgG Fc CH2-CH3 cleft, such as the peptides described herein, inhibit the binding of immune complexed (antigen-bound) IgG Fc to FcγRs.
Compounds also can be interactively designed from structural information of the compounds described herein using other structure-based design/modeling techniques (see, e.g., Jackson (1997) Seminars in Oncology 24:L164-172; and Jones et al. (1996) J. Med. Chem. 39:904-917).
Compounds and polypeptides also can be identified by, for example, identifying candidate compounds by computer modeling as fitting spatially and preferentially (i.e., with high affinity) into the CH2-CH3 cleft of an immunoglobulin molecule, and then screening those compounds in vitro or in vivo for the ability to inhibit Fc-mediated immune complex formation. Suitable methods for such in vitro and in vivo screening include those described herein.
This document provides compositions and articles of manufacture that can be used in methods for treating conditions that arise from abnormal Fc-mediated immune complex formation (e.g., over-production of Fc-mediated immune complexes). The polypeptides, compounds, and compositions provided herein can be administered to a subject (e.g., a human or another mammal) having an viral infection, for example, that can be alleviated by modulating Fc-mediated immune complex formation and inhibit immune complexed IgG Fc to mC1q, sC1q, FcγRs, and FcRn. Typically, one or more polypeptides or compounds can be administered to a subject suspected of having a disease or condition associated with immune complex formation. Compositions generally contain one or more polypeptides and compounds described herein. A CH2-CH3 binding polypeptide, for example, can be in a pharmaceutically acceptable carrier or diluent, and can be administered in amounts and for periods of time that will vary depending upon the nature of the particular disease, its severity, and the subject's overall condition. Typically, the polypeptide is administered in an inhibitory amount (i.e., in an amount that is effective for inhibiting the production of immune complexes in the cells or tissues contacted by the polypeptide). The polypeptides and methods described herein also can be used prophylactically, e.g., to minimize immunoreactivity in a subject at risk for abnormal or over-production of immune complexes (e.g., a transplant recipient).
The ability of a polypeptide to inhibit Fc-mediated immune complex formation can be assessed by, for example, measuring immune complex levels in a subject before and after treatment. A number of methods can be used to measure immune complex levels in tissues or biological samples, including those that are well known in the art. If the subject is a research animal, for example, immune complex levels in the joints can be assessed by immunostaining following euthanasia. The effectiveness of an inhibitory polypeptide also can be assessed by direct methods such as measuring the level of circulating immune complexes in serum samples. Alternatively, indirect methods can be used to evaluate the effectiveness of polypeptides in live subjects. For example, reduced immune complex formation can be inferred from clinical improvement of immune mediated diseases or in vitro or in vivo models of which have been shown to be essential in the therapeutic use in treating Atherosclerosis.
Methods for formulating and subsequently administering therapeutic compositions are well known to those skilled in the art. Dosing is generally dependent on the severity and responsiveness of the disease state to be treated, with the course of treatment lasting from several days to several months, or until a cure is effected or a diminution of the disease state is achieved. Persons of ordinary skill in the art routinely determine optimum dosages, dosing methodologies and repetition rates. Optimum dosages can vary depending on the relative potency of individual polypeptides, and can generally be estimated based on EC50 found to be effective in in vitro and in vivo animal models. Typically, dosage is from 0.01 ug to 100 g per kg of body weight, and may be given once or more daily, biweekly, weekly, monthly, or even less often. Following successful treatment, it may be desirable to have the patient undergo maintenance therapy to prevent the recurrence of the disease state.
The present document provides pharmaceutical compositions and formulations that include the polypeptides and/or compounds described herein. Polypeptides therefore can be admixed, encapsulated, conjugated or otherwise associated with other molecules, molecular structures, or mixtures of compounds such as, for example, liposomes, polyethylene glycol, receptor targeted molecules, or oral, rectal, topical or other formulations, for assisting in uptake, distribution and/or absorption.
A “pharmaceutically acceptable carrier” (also referred to herein as an “excipient”) is a pharmaceutically acceptable solvent, suspending agent, or any other pharmacologically inert vehicle for delivering one or more therapeutic compounds (e.g., CH2-CH3 binding polypeptides) to a subject. Pharmaceutically acceptable carriers can be liquid or solid, and can be selected with the planned manner of administration in mind so as to provide for the desired bulk, consistency, and other pertinent transport and chemical properties, when combined with one or more of therapeutic compounds and any other components of a given pharmaceutical composition. Typical pharmaceutically acceptable carriers that do not deleteriously react with amino acids include, by way of example and not limitation: water; saline solution; binding agents (e.g., polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g., lactose and other sugars, gelatin, or calcium sulfate); lubricants (e.g., starch, polyethylene glycol, or sodium acetate); disintegrates (e.g., starch or sodium starch glycolate); and wetting agents (e.g., sodium lauryl sulfate).
Pharmaceutical compositions can be administered by a number of methods, depending upon whether local or systemic treatment is desired and upon the area to be treated. Administration can be, for example, topical (e.g., transdermal, sublingual, ophthalmic, or intranasal); pulmonary (e.g., by inhalation or insufflation of powders or aerosols); oral; or parenteral (e.g., by subcutaneous, intrathecal, intraventricular, intramuscular, or intraperitoneal injection, or by intravenous drip). Administration can be rapid (e.g., by injection) or can occur over a period of time (e.g., by slow infusion or administration of slow release formulations). For treating tissues in the central nervous system, CH2-CH3 binding polypeptides can be administered by injection or infusion into the cerebrospinal fluid, preferably with one or more agents capable of promoting penetration of the polypeptides across the blood-brain barrier.
Formulations for topical administration of CH2-CH3 binding polypeptides include, for example, sterile and non-sterile aqueous solutions, non-aqueous solutions in common solvents such as alcohols, or solutions in liquid or solid oil bases. Such solutions also can contain buffers, diluents and other suitable additives. Pharmaceutical compositions and formulations for topical administration can include transdermal patches, ointments, lotions, creams, gels, drops, suppositories, sprays, liquids, and powders. Nasal sprays are particularly useful, and can be administered by, for example, a nebulizer or another nasal spray device. Administration by an inhaler also is particularly useful. Conventional pharmaceutical carriers, aqueous, powder or oily bases, thickeners and the like may be necessary or desirable.
Compositions and formulations for oral administration include, for example, powders or granules, suspensions or solutions in water or non-aqueous media, capsules, sachets, or tablets. Such compositions also can incorporate thickeners, flavoring agents, diluents, emulsifiers, dispersing aids, or binders.
Compositions and formulations for parenteral, intrathecal or intraventricular administration can include sterile aqueous solutions, which also can contain buffers, diluents and other suitable additives (e.g., penetration enhancers, carrier compounds and other pharmaceutically acceptable carriers).
Pharmaceutical compositions include, without limitation, solutions, emulsions, aqueous suspensions, and liposome-containing formulations. These compositions can be generated from a variety of components that include, for example, preformed liquids, self-emulsifying solids and self-emulsifying semisolids. Emulsions are often biphasic systems comprising of two immiscible liquid phases intimately mixed and dispersed with each other; in general, emulsions are either of the water-in-oil (w/o) or oil-in-water (o/w) variety. Emulsion formulations have been widely used for oral delivery of therapeutics due to their ease of formulation and efficacy of solubilization, absorption, and bioavailability.
Liposomes are vesicles that have a membrane formed from a lipophilic material and an aqueous interior that can contain the composition to be delivered. Liposomes can be particularly useful due to their specificity and the duration of action they offer from the standpoint of drug delivery. Liposome compositions can be formed, for example, from phosphatidylcholine, dimyristoyl phosphatidylcholine, dipalmitoyl phosphatidylcholine, dimyristoyl phosphatidylglycerol, or dioleoyl phosphatidylethanolamine. Numerous lipophilic agents are commercially available, including LIPOFECTIN® (a 1:1 (w/w) liposome formulation of the cationic lipid N-[1-(2,3-dioleyloxy)propyl]-n,n,n-trimethylammonium chloride (DOTMA) and dioleoyl phophotidylethanolamine (DOPE) in membrane-filtered water; Invitrogen/Life Technologies, Carlsbad, Calif.) and EFFECTENE™ (a non-liposomal lipid formulation in conjunction with a DNA-condensing enhancer; Qiagen, Valencia, Calif.).
Polypeptides can further encompass any pharmaceutically acceptable salts, esters, or salts of such esters, or any other compound which, upon administration to an animal including a human, is capable of providing (directly or indirectly) the biologically active metabolite or residue thereof. Accordingly, for example, this document provides pharmaceutically acceptable salts of polypeptides, prodrugs and pharmaceutically acceptable salts of such prodrugs, and other bioequivalents. The term “prodrug” indicates a therapeutic agent that is prepared in an inactive form and is converted to an active form (i.e., drug) within the body or cells thereof by the action of endogenous enzymes or other chemicals and/or conditions. The term “pharmaceutically acceptable salts” refers to physiologically and pharmaceutically acceptable salts of the polypeptides provided herein (i.e., salts that retain the desired biological activity of the parent polypeptide without imparting undesired toxicological effects). Examples of pharmaceutically acceptable salts include, but are not limited to, salts formed with cations (e.g., sodium, potassium, calcium, or polyamines such as spermine); acid addition salts formed with inorganic acids (e.g., hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, or nitric acid); and salts formed with organic acids (e.g., acetic acid, citric acid, oxalic acid, palmitic acid, or fumaric acid).
Pharmaceutical compositions containing the polypeptides provided herein also can incorporate penetration enhancers that promote the efficient delivery of polypeptides to the skin of animals. Penetration enhancers can enhance the diffusion of both lipophilic and non-lipophilic drugs across cell membranes. Penetration enhancers can be classified as belonging to one of five broad categories, i.e., surfactants (e.g., sodium lauryl sulfate, polyoxyethylene-9-lauryl ether and polyoxyethylene-20-cetyl ether); fatty acids (e.g., oleic acid, lauric acid, myristic acid, palmitic acid, and stearic acid); bile salts (e.g., cholic acid, dehydrocholic acid, and deoxycholic acid); chelating agents (e.g., disodium ethylenediaminetetraacetate, citric acid, and salicylates); and non-chelating non-surfactants (e.g., unsaturated cyclic ureas). Alternatively, inhibitory polypeptides can be delivered via iontophoresis, which involves a transdermal patch with an electrical charge to “drive” the polypeptide through the dermis.
Some embodiments provided herein include pharmaceutical compositions containing (a) one or more polypeptides and (b) one or more other agents that function by a different mechanism. For example, anti-inflammatory drugs, including but not limited to nonsteroidal anti-inflammatory drugs and corticosteroids, and antiviral drugs, including but not limited to ribivirin, vidarabine, acyclovir and ganciclovir, can be included in compositions. Other non-polypeptide agents (e.g., chemotherapeutic agents) also are within the scope of this document. Such combined compounds can be used together or sequentially.
Compositions additionally can contain other adjunct components conventionally found in pharmaceutical compositions. Thus, the compositions also can include compatible, pharmaceutically active materials such as, for example, antipruritics, astringents, local anesthetics or anti-inflammatory agents, or additional materials useful in physically formulating various dosage forms of the compositions provided herein, such as dyes, flavoring agents, preservatives, antioxidants, opacifiers, thickening agents and stabilizers. Furthermore, the composition can be mixed with auxiliary agents, e.g., lubricants, preservatives, stabilizers, wetting agents, emulsifiers, salts for influencing osmotic pressure, buffers, colorings, flavorings, and aromatic substances. When added, however, such materials should not unduly interfere with the biological activities of the polypeptide components within the compositions provided herein. The formulations can be sterilized if desired.
The pharmaceutical formulations, which can be presented conveniently in unit dosage form, can be prepared according to conventional techniques well known in the pharmaceutical industry. Such techniques include the step of bringing into association the active ingredients (e.g., the CH2-CH3 binding polypeptides provided herein) with the desired pharmaceutical carrier(s) or excipient(s). Typically, the formulations can be prepared by uniformly and bringing the active ingredients into intimate association with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product. Formulations can be sterilized if desired, provided that the method of sterilization does not interfere with the effectiveness of the polypeptide contained in the formulation.
The compositions described herein can be formulated into any of many possible dosage forms such as, but not limited to, tablets, capsules, liquid syrups, soft gels, suppositories, and enemas. The compositions also can be formulated as suspensions in aqueous, non-aqueous or mixed media. Aqueous suspensions further can contain substances that increase the viscosity of the suspension including, for example, sodium carboxymethylcellulose, sorbitol, and/or dextran. Suspensions also can contain stabilizers.
CH2-CH3 binding polypeptides can be combined with packaging material and sold as kits for reducing Fc-mediated immune complex formation. Components and methods for producing articles of manufacture are well known. The articles of manufacture may combine one or more of the polypeptides and compounds set out in the above sections. In addition, the article of manufacture further may include, for example, buffers or other control reagents for reducing or monitoring reduced immune complex formation. Instructions describing how the polypeptides are effective for reducing Fc-mediated immune complex formation can be included in such kits.
The influenza virus causes influenza, which is more commonly known as the flu. Each year 3,000,000-5,000,000 severe cases of flu occur worldwide that results in 250,000-500,000 deaths, primarily in the very young, the very old or in people with health issues. Periodically, influenza pandemics occur that kill more than 1,000,000 people. During the 20th century, three influenza pandemics have occurred, the Spanish influenza in 1918, the Asian influenza in 1958 and the Hong Kong influenza in 1968. The influenza A virus is the usual cause of flu and several different serotypes have been identified, including H1N1, which causes Spanish Flu and Swine Flu, H2N2, which causes Asian Flu, H3N2, which causes Hong Kong Flu and H5N1, which causes Bird Flu.
The influenza virus envelope contains two main glycoproteins, hemagglutinin and neuraminidase, which encapsulates 7-8 RNA segments, each of which encode one or two proteins. The influenza vaccine is highly effective; however, vaccinated people are still at risk of infection due to the highly variable serotypes of the virus and the inherent high mutation rate of the virus. Two different types of antivirals, the neuraminidase inhibitors, oseltamivir and zanavir, and the M2 proton channel protein inhibitors, amantadine and rimantadine, are available to treat patients with the flu, however, there are significant risks associated with the use of these antivirals. Given the great number of people that succumb to the flu each year and the resulting fatality rate, 5-17%, better treatment options for those patients with severe cases of flu are desperately needed.
A connection between the severity of flu and autoimmune disease has been observed in patients suffering from autoimmune diseases and is well documented (Blumentals et al., Musculoskelet Disord., 2012, 13:158; http://www.flu.gov/at-risk/health-conditions/arthritis/ and http://www.cdc.gov/arthritis/flu.htm). Moreover, some studies suggest that circulating immune complexes (ICs) could enhance the ability of the influenza virus to spread in infected individuals (Monsalvo et al., Nat Med., 2011, 17(2):195-9).
While most researchers argue that the greater susceptibility of patients with autoimmune diseases to influenza infections is due to their compromised health, unexpectedly, as described in Example 7, influenza virus contains Fc receptors (FcRs) that can bind to ICs. Thus, influenza virus could be using immune complexes as a mechanism to hijack the immune system and proliferate more rapidly. Moreover, as shown in Example 7, NB406 peptide prevents this binding from occurring and is expected to function as a therapeutic agent to prevent the proliferation or mitigate the severity of influenza virus infections.
The hepatitis C virus infects the liver and can cause cirrhosis, liver failure and liver cancer. An estimated 150,000,000-200,000,000 people are estimated to be infected with hepatitis C worldwide and more than 500,000 hepatitis C related deaths occur each year. There is no vaccine for hepatitis C. The two best treatments for hepatitis C infections are Harvoni and Sovaldi, but they are incredibly expensive. Given the severity of hepatitis C viral infections and the expense of the current drugs that are available to treat it, a more reasonably priced drug is desperately needed. There are 6 different hepatitis virus that can cause liver infections, hepatitis A, B, C, D, E and F. While they are distinctly different viruses, their epidemiology and physiology are very similar.
An increased risk of hepatitis viral infections has been observed in patients suffering from autoimmune diseases. (Csepregi et al., J Rheumatol., 2001, 28:474-7; Ramos-Casals et al, Med Clin (Barc)., 2001, 19; 116(18):701-9). Some studies suggest that circulating immune complexes (ICs) could enhance the ability of hepatitis virus to spread in infected individuals (Araki et al, Acta Med Okayama., 1980, 34(2):131-8; Pfueller et al., Clin Exp Immunol., 1983, 54(3):655-60; Margolis et al., Hepatology, 1990, 11(1):31-7; Du et al., Zhonghua Zhong Liu Za Zhi, 2011 33(12):905-10)
While most researchers argue that the greater susceptibility of patients with autoimmune diseases to hepatitis viral infections is due to their compromised health, unexpectedly, as shown in Example 8, hepatitis A and C viruses contain Fc receptors (FcRs) that bind to ICs. Thus hepatitis virus could be using immune complexes as a mechanism to bridge (hijack) the immune system and proliferate more rapidly. Moreover, as shown in Example 8, the NB406 peptide can prevent this binding from occurring and thus can be expected to function as potential therapeutic agent to prevent the proliferation of hepatitis infections.
Ebola or Ebola Virus Disease (EVD), and the more severe manifestation of EVD, Ebola hemorrhagic fever (EHF), are caused by infection with an Ebola virus strain. The Ebola virus causes an acute, febrile hemorrhagic illness which is often fatal if untreated. (Wiwanitkit, N. Am. J. Med. Sci., 2014, 6(11):549-552.) The Ebola virus can cause disease in humans and nonhuman primates (monkeys, gorillas, and chimpanzees). (CDC, About Ebola Virus Disease, available on the world wide web at cdc.gov/vhf/ebola/about.html) EVD first appeared in 1976 in two simultaneous outbreaks, one in Nzara, Sudan, and the other in Yambuku, Democratic Republic of Congo. The average EVD case fatality rate is around 50%. During outbreaks, case fatality rates have varied from 25% to 90%. (WHO Fact Sheet, Ebola Virus Disease, available on the world wide web at who.int/mediacentre/factsheets/fs103/en/#) As of January 2015, in the most recent outbreak, more than 20,000 cases of EVD had resulted in more than 8600 deaths. (CDC, 2014 Ebola Outbreak in West Africa—Case Counts, available on the world wide web at cdc.gov/vhf/ebola/outbreaks/2014-west-africa/case-counts.html)
There are five identified Ebola virus (EBOV) species, four of which are known to cause disease in humans: Ebola virus Zaire (Zaire ebolavirus; ZEBOV); Sudan virus (Sudan ebolavirus; SUDV or SEBOV); Taï Forest virus (Taï Forest ebolavirus; TAFV—formerly Côte d'Ivoire ebolavirus); and Bundibugyo virus (Bundibugyo ebolavirus; BDBV). The fifth, Reston virus (Reston ebolavirus; RESTV or REBOV), has been reported to cause disease in nonhuman primates and pigs, but not in humans. The natural reservoir host of Ebola virus and its means of transmission to humans from that host to humans remain unknown. (CDC, About Ebola Virus Disease, available on the world wide web at cdc.gov/vhf/ebola/about.html; Ansari et al., J. Autoimm., 2014, 55:1-9; Barrette et al., Science, 2009, 325(5937):204-206.)
Ebola virus and Marburg virus constitute the family Filoviridae in the order of Mononegvirales. Filoviruses are enveloped, non-segmented, negative-stranded RNA viruses. (Feldmann et al., Lancet, 2011, 377:849-62.) These filoviruses have characteristic filamentous particles that give the virus family its name.
The Ebola virus genome consists of seven genes: nucleoprotein (NP), virion protein (VP) 35, VP40, glycoprotein (GP), VP30, VP24, RNA-dependent RNA polymerase (L). With the exception of the glycoprotein gene, all genes are monocistronic, encoding for one structural protein. (Feldmann et al., Lancet, 2011, 377:849-62.) The glycoprotein is the only transmembrane surface protein of the virus and forms trimeric spikes consisting of two subunits, glycoprotein 1 (GP1) and glycoprotein 2 (GP2), linked by a disulfide bond. (Feldmann et al., Lancet, 2011, 377:849-62; Jiang et al., Virol. Sin., 2009, 24(2): 121-135.) Ebola virus is distinguished from other Mononegavirales by its production of a soluble glycoprotein (sGP), which is the primary product of the GP gene, and gets secreted in large quantities from infected cells. (Feldmann et al., Lancet, 2011, 377:849-62.) The glycoprotein of Ebola virus mediates viral entry into host cells, augmentation of budding of viral particles, and interference with the expression of host cellular adhesion molecules. (Kuhl et al., J Infect. Dis., 2011, 204:S840-S849.) The characteristic filamentous shape of Ebola and Marburg viruses is largely determined by the matrix protein VP40. (Hartleib et al. Virology, 2006, 344:64-70.)
To date, the filovirus receptor on host cells has been elusive, but a variety of distinct and unrelated cell surface proteins have been implicated in viral entry including C-Type lectins, asialoglycoprotein receptor (ASGP-R), dendritic cell-specific ICAM-3 grabbin non-integrin (DC-SIGN), human macrophage galactose- and-acetylgalactosamine-specific C-type lectin (hMGL), and β1 integrin adhesion receptors. (Dolnik et al., Cell. Mol. Life Sci., 2008, 65:756-776; Barlbaud et al. Informa Healthcare, 2002 6(4):423 431.) Recently, the Niemann-Pick C1 (NPC1) receptor has been identified as an important mediator of Ebola infection of macrophages. (Dahlmann et al., J. Infect. Dis., published online Apr. 14, 2015.) None of the receptors identified to date explain the virus's ability to gain entry into diverse cell types and the resulting fast replication rate of Ebola virus in infected subjects.
Initially, Ebola virus primarily targets cells of the monocytes/macrophage and dendritic cell lineages; later in infection, the virus is able to gain entry into endothelial cells and hepatocytes. (Ansari et al., J. Autoimm., 2014, 55:1-9.) The virus is capable of replicating in a variety of cell types, including macrophages, epithelial cells, hepatocytes, and endothelial cells. (Gupta et al., J. Virol., 2004, 78(2):958-967.)
The detailed pathogenesis of Ebola virus infection is not well understood. In some cases, the infection can result in no symptoms or a mild infection characterized by transient flu like symptoms associated with mild coagulopathy, thrombocytopenia and leukocytosis, and full recovery. (Ansari et al., J. Autoimm., 2014, 55:1-9; Becquart et al., PLOS One, 2010, 5(2):e9126.) In other cases, the infection causes severe illness followed by hemorrhage, disseminated intravascular coagulation (DIC), shock, and death. The reasons for such varied outcomes are assumed to be secondary to the level of viral replication, with uncontrolled viral replication being associated with more serious illness. (Ansari et al., J. Autoimm., 2014, 55:1-9.)
In comparison to other hemorrhagic viral infections, patients having an Ebola virus infection have a higher viral load. Moreover, a higher viral load correlates with worse patient prognosis. For example, a recent study of 288 Ebola patients found that patients with a viral load of >106 copies/ml had a higher case fatality rate than patients with <106 copies/ml (Li et al., Int. J. Infect. Dis., 2016, 42:34-39 (published online Oct. 30, 2015)).
Circulating immune complexes (CICs) have been shown to play a role in other viral infections, including dengue fever and dengue hemorrhagic fever (DHF). Immune complexes (IC) can form between anti-viral antibodies and viral antigens; between anti-viral antibodies and viral antigens from a different strain of the same virus; or between non-viral antibodies and non-viral antigens.
For example, during a second dengue infection with a different strain of the virus, dengue antibodies that bind but do not neutralize viral particles of the second strain of the virus are believed to bring circulating immune complexes into close proximity with the cell surface Fc receptors, which in turn facilitate viral entry into the cells, driving antibody-dependent enhancement (ADE) of dengue virus infection. (Boonak et al., J. Immunol., 2013, 190(11):5659-5665; Guzman et al., Arch Virol., 2013, 158(7):1445-1459; Chan et al., PNAS, 2011 108(30): 12479-12484.) Binding of dengue virus to non-dengue virus immune complexes has also been reported and suggested as a possible mechanism for ADE in DHF. (U.S. Pat. No. 8,815,813).
Additionally, in a subject infected with a first virus or disease, the immune response to a second, different virus or disease can include an antibody response, resulting in the formation of immune complexes between antibodies to the second virus or disease and antigens from the second virus or disease. In the case of an Ebola virus infection, an immune response to a second, different virus or disease could occur before or simultaneously with the Ebola virus infection. As used herein, the terms “heterologous immune complex” and “heterologous IC” mean a complex formed between a non-Ebola antibody and a non-Ebola antigen.
Reports have previously suggested that anti-Ebola virus immune complexes may enhance Ebola virus infection. (Johnson et al., Antiviral Res., 2014, 107:102-109; Takeda et al., J. Infect. Dis. 2007, 196:S347-56.) But Ebola virus disease has not been previously associated with heterologous immune complexes or circulating heterologous immune complexes. Moreover, the role of immune complexes in Ebola virus infection is controversial. Passive immunization, using antibodies produced in animals or sera/immunoglobulins from individuals who have survived infection has been used as a therapeutic vaccine post-infection. (Ansari et al., J. Autoimm., 2014, 55:1-9.) And use of an immune complex consisting of Ebola glycoprotein and a monoclonal antibody that recognizes an epitope in the glycoprotein has been suggested as an Ebola vaccine candidate. (Phoolcharoen et al., PNAS USA, 2011, 108(51):20695-700.) Such treatments could be ineffective (Oswald et al., PLOS Pathog., 2007, 3(1):e9) or even deleterious if immune complexes exacerbated Ebola virus disease.
Unexpectedly, as further described in the Examples, Ebola Virus and Ebola Virus glycoprotein (GP) can act as an Fc Receptor. Ebola Virus secretory glycoprotein (sGP) may also be able to act as an Fc Receptor. The viral Fc receptor (FcR) activity of Ebola virus could, therefore, permit binding of Ebola to an immune complex which is also bound to a host cell Fc receptor, enhancing entry of Ebola into host cells. That is, a heterologous immune complex, not just an anti-Ebola virus immune complex, could bridge a host cell-Ebola virus interaction. The results of Ebola virus GP binding to non-Ebola virus related immune complexes of peroxidase-rabbit anti-peroxidase IgG (“PAP-IC”) are shown in Example 5 below. These results demonstrate that Ebola GP may interact with heterologous immune complexes. Ebola's ability to interact with heterologous immune complexes may contribute to antibody dependent enhancement that accelerates disease progression, increasing Ebola virus infectivity and contributing to the pathogenicity of hemorrhagic fever and shock seen in Ebola virus infections.
The filamentous shape of Ebola virus and the number of Ebolaviral Fc receptor-functional glycoproteins differentiate it from other viruses expressing viral Fc-receptors, including Dengue virus. For example, a single Ebola virion may express on its surface thousands of trimeric glycoprotein spikes. (Tran et al. J. Virol., 2014, 88(18):10958-62; Beniac et al., PLOS One, 2012, 7(1): e29608.) In contrast, a Dengue virion has an icosahedral scaffold of just 90 glycoprotein E dimers. (Kuhn et al., Cell, 2002, 108(5):717-725.) Because an Ebola virion is may express many more viral Fc Receptor-functional surface proteins than a Dengue virion, Ebola may infect cells more quickly and replicate more quickly, increasing viral load.
The filamentous shape of Ebola virus may further enhance the ability of the glycoprotein of Ebola virus to act as a bridge. Because the glycoprotein binds to an IC which can also bind to cellular Fc receptors or complement receptors, a filamentous Ebola virion may attach to a host cell along the virion's length via a large number of interactions, promoting virus-host interaction, internalization, and/or infection. The long, filamentous shape of Ebola provides more points of contact with a host cell than the shorter, spherical or polyhedral shape of many other viruses including dengue.
In humans, co-infection with other diseases can cause an antibody response which results in the formation of heterologous immune complexes. Circulating immune complexes may cause antibody-dependent enhancement (ADE). The observed geographic correlation of serious malaria cases and the Ebola outbreak is consistent with the proposition that coinfection with other serious pathogenic agents may exacerbate Ebola virus infection. As described in Example 1, West Africa, the site of the unprecedented 2014 Ebola outbreak, represents a region having one of the highest numbers of serious Malaria cases (see Hay et al, PLOS Med., 2010, 7(6):e1000290). Also consistent with the exacerbation by coinfection proposition are the observations that some Ebola virus infections are asymptomatic (Becquart et al., PLOS One, 2010, 5(2):e9126), and that Ebola outbreaks have not occurred in other parts of the world, especially in the West where the incidence of co-infection other pathogenic agents is substantially lower. As described in Example 2, the observed incidence of porcine reproductive and respiratory syndrome virus (PRRSV) coinfection in REBOV-infected pig populations is likewise consistent with a proposed disease mechanism wherein REBOV replication is enhanced by coinfection, for example by immune complex (IC) formation induced by a non-related virus, PRRSV.
Exemplary diseases that can cause an antibody response resulting in the formation of heterologous immune complexes in humans include, for example, human immunodeficiency virus (HIV), human cytomegalovirus (HCMV), herpes simplex virus (HSV), hepatitis C virus, human papilloma virus (HPV), Mycobacterium tuberculosis, malaria/Plasmodium falciparum, and Schistosoma haematobium.
While many Fc receptors in humans are expressed only on immune cells including, for example, monocytes, macrophages, neutrophils, dendritic cells, mast cells, basophils, B cells, NK cells, NKT cells, etc., the neonatal Fc Receptor (FcRn) is expressed on both immune cells including, for example, antigen-presenting cells, monocytes/macrophages, neutrophils, and non-immune cells including, for example, vascular endothelial cells, and intestinal epithelial cells. (Bruhns, Blood, 2012, 119(24):5560-5649.) The viral Fc receptor of Ebola virus could, therefore, once bound to an IC, mediate entry into the cell types in which Ebola virus is known to replicate, including, for example, macrophages, epithelial cells, and endothelial cells. (Gupta et al., J. Virol., 2004, 78(2):958-967.) Polypeptides that bind to the CH2-CH3 cleft of an immunoglobulin molecule and inhibit Fc-mediated immune complex formation have been suggested as useful for treatment of ADE in dengue fever and dengue hemorrhagic fever. (U.S. Pat. No. 8,815,813.) Due to the unexpected finding that Ebola Virus and Ebola Virus glycoprotein (GP) can act as an Fc Receptor, such polypeptides may also affect interactions between Ebola Virus and ICs. Indeed, due to the fundamental differences in viral shape, in the number of surface receptors with Fc Receptor function, and in viral replication during disease progression, polypeptides that inhibit Fc-mediated immune complex formation may be significantly more effective when applied in the context of Ebola virus infections than for treatment of dengue virus infections.
Example 3 demonstrates that the binding of Ebola virus GP binding to heterologous immune complexes is inhibited by NB406 (SEQ ID NO:20; APPDCAWHLGELVWCT). In addition, SEQ ID NO:20 inhibited binding of either FcγRIIa or FcγRIIb to immune complexed IgG Fc by more than 70%, suggesting that SEQ ID NO:20 may abrogate antibody dependent enhancement (ADE) in Ebola virus disease caused by heterologous immune complexes (such as PAP-IC).
Methods for Using CH2-CH3 Binding Polypeptides to Inhibit Fc-Mediated Immune Complex Formation
CH2-CH3 binding polypeptides can be used in in vitro assays of Fc-mediated immune complex (IC) formation. Such methods are useful to, for example, evaluate the ability of a CH2-CH3 cleft-binding polypeptide to block Fc-mediated immune complex formation. In vitro methods can involve, for example, contacting an immunoglobulin molecule (e.g., an antigen bound immunoglobulin molecule) with an effector molecule (e.g., mC1q, sC1q, FcRs and FcRn, or another antibody) in the presence and absence of a polypeptide as provided herein, and determining the level of IC formation in each sample. Levels of IC formation can be evaluated by, for example, polyacrylamide gel electrophoresis with Coomassie blue or silver staining, or by co-immunoprecipitation. Such methods are known to those of ordinary skill in the art, and can be used to test the ability of a candidate polypeptide or compound to inhibit IC formation associated with an infectious disease, for example.
Methods provided herein also can be used to inhibit complement- or Fc-mediated immune complex formation in a subject, and to treat an infectious viral disease in a subject by inhibiting complement- or Fc-mediated immune complex formation. Such methods can include, for example, administering any of the polypeptides described herein, or a composition containing any of the polypeptides described herein, to a subject having or being at risk for having or developing an infectious viral disease (e.g., Ebola Virus Disease, influenza virus infection, hepatitis virus infection). For example, a method can include administering to an individual a composition containing a polypeptide that includes the amino acid sequence Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 10). Alternatively, a method can include administering to a subject a polypeptide that contains the amino acid sequence Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:2), Xaa-Pro-Pro-Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO: 19; where Xaa is any amino acid), or Ala-Pro-Pro-Asp-Cys-Ala-Trp-His-Leu-Gly-Glu-Leu-Val-Trp-Cys-Thr (SEQ ID NO:20).
In some embodiments, when the viral disease is Ebola virus infection, a polypeptide can be administered to inhibit immune complex formation that is associated with antibody dependent enhancement (ADE), including complement-mediated antibody-dependent enhancement, of Ebola virus infection or contributes to the enhancement of an Ebola virus infection. The polypeptide can, for example, result in clinical or histiological improvement of an Ebola virus infection, result in an improvement or delay of onset of one or more of the histiological characteristics of an Ebola virus infection, and/or decrease the ADE of an Ebola virus infection. In some cases, the polypeptide can inhibit binding of a heterologous IC to an FcγR, inhibit formation of IC that contribute to immunopathogenesis of the ADE of EBOV infections, inhibit binding of EBOV virions to IgG IC, inhibit binding of a EBOV protein (e.g., GP) to an IgG immune complex, inhibit binding of EBOV and/or TNF-α to IgG IC, inhibit binding of a EBOV-IgG IC to FcγI, a FcγIIa H131 allele, a FcγIIa R131 allele, FcγRIIb, FcγRIIc, FcγRIIIa, FcγIIIb, or FcRn, and/or inhibit binding of EBOV-IgG IC to mC1q or sC1q.
In some embodiments, a polypeptide can be administered to a subject that has been diagnosed as having an Ebola virus infection, a subject suspected of having an Ebola virus infection, a subject exhibiting symptoms of an Ebola virus infection, a subject that is at risk of contracting an Ebola virus infection, and/or a subject that has been exposed to an Ebola virus. In some embodiments, a polypeptide can be administered to minimize the risk of a subject developing an Ebola virus infection. In one aspect, a polypeptide could be administered to a subject in a hospitalized population wherein one or more other subjects in the same hospitalized population has an Ebola virus infection, is suspected of having an Ebola virus infection, and/or is exhibiting symptoms of an Ebola virus infection.
In some embodiments, a polypeptide can be administered to a subject that has been diagnosed as having or is suspected of having a coinfection with a coinfective pathogen and has an Ebola virus infection, is suspected of having an Ebola virus infection, is exhibiting symptoms of an Ebola virus infection, is at risk of contracting an Ebola virus infection, and/or has been exposed to an Ebola virus. The coinfective pathogen may include, for example, human immunodeficiency virus (HIV), human cytomegalovirus (HCMV), herpes simplex virus (HSV), hepatitis C virus, human papilloma virus (HPV), Mycobacterium tuberculosis, malaria/Plasmodium falciparum, Schistosoma haematobium, and/or other disease associated with antibody production and/or immune complex formation. Such administration may be particularly helpful in co-infected individuals or individuals at risk of being co-infected because of the potential for non-Ebola virus related immune complexes to allow Ebola virus association with and entry into host cells.
In some embodiments, a polypeptide can be administered as soon as a subject is diagnosed with an Ebola virus infection, is suspected of having an Ebola virus infection, is exhibiting symptoms of an Ebola virus infection, is determined to be at risk of contracting an Ebola virus infection, and/or has been exposed to an Ebola virus. In some embodiments, a polypeptide can be administered to a subject who has or is suspected of having hemorrhagic fever resulting from an Ebola virus infection. In some embodiments, a polypeptide can be administered to a subject having a replicating Ebola virus. In some embodiments, a polypeptide can be administered to a subject in the later stages of Ebola virus infection or who is suspected of being in the advanced or later stages of Ebola virus infection or who is exhibiting hemorrhagic symptoms. In contrast to other viral infections, including, for example Dengue Fever infections and Dengue Hemorrhagic Fever, administration of a polypeptide to a subject in the advanced or later stages of Ebola virus infection, including to a subject having hemorrhagic fever, may still alleviate the symptoms and detrimental effects of Ebola virus infection because Ebola virus continues to replicate during the hemorrhagic fever stage and/or when a subject is exhibiting hemorrhagic symptoms.
In some embodiments, a polypeptide can be administered to a subject that has been diagnosed as having an influenza virus infection, a subject suspected of having an influenza virus infection, a subject exhibiting symptoms of an influenza virus infection, a subject that is at risk of contracting an influenza virus infection, and/or a subject that has been exposed to an influenza virus. In some embodiments, a polypeptide can be administered to minimize the risk of a subject developing an influenza virus infection. In one aspect, a polypeptide could be administered to a subject in a hospitalized population wherein one or more other subjects in the same hospitalized population has an influenza virus infection, is suspected of having an influenza virus infection, and/or is exhibiting symptoms of an influenza virus infection.
In some embodiments, a polypeptide can be administered as soon as a subject is diagnosed with an influenza virus infection, is suspected of having an influenza virus infection, is exhibiting symptoms of an influenza virus infection, is determined to be at risk of contracting an influenza virus infection, and/or has been exposed to an influenza virus.
In some embodiments, a polypeptide can be administered to a subject that has been diagnosed as having or is suspected of having an autoimmune disease and as having or is suspected of having an influenza virus infection, is suspected of having an influenza virus infection, is exhibiting symptoms of an influenza virus infection, is at risk of contracting an influenza virus infection, and/or has been exposed to an influenza virus. The autoimmune disease may include, for example, systemic lupus erythematosus, cryoglobulinemia, rheumatoid arthritis, scleroderma, Sjögren's syndrome, and/or another autoimmune disease associated with antibody production and/or immune complex formation. Such administration may be particularly helpful in individuals having an autoimmune disease because of the potential for non-virus related immune complexes to allow virus association with and entry into host cells.
In some embodiments, a polypeptide can be administered to a subject that has been diagnosed as having a hepatitis virus infection, a subject suspected of having a hepatitis virus infection, a subject exhibiting symptoms of a hepatitis virus infection, a subject that is at risk of contracting a hepatitis virus infection, and/or a subject that has been exposed to a hepatitis virus. In some embodiments, a polypeptide can be administered to minimize the risk of a subject developing a hepatitis virus infection.
In some embodiments, a polypeptide can be administered as soon as a subject is diagnosed with a hepatitis virus infection, is suspected of having a hepatitis virus infection, is exhibiting symptoms of a hepatitis virus infection, is determined to be at risk of contracting a hepatitis virus infection, and/or has been exposed to a hepatitis virus. In some embodiments, the hepatitis virus can include Hepatitis A and/or Hepatitis C.
In some embodiments, a polypeptide can be administered to a subject that has been diagnosed as having or is suspected of having an autoimmune disease and as having or is suspected of having a hepatitis virus infection, is suspected of having a hepatitis virus infection, is exhibiting symptoms of a hepatitis virus infection, is at risk of contracting a hepatitis virus infection, and/or has been exposed to a hepatitis virus. The autoimmune disease may include, for example, systemic lupus erythematosus, cryoglobulinemia, rheumatoid arthritis, scleroderma, Sjögren's syndrome, and/or another autoimmune disease associated with antibody production and/or immune complex formation. Such administration may be particularly helpful in individuals having an autoimmune disease because of the potential for non-virus related immune complexes to allow virus association with and entry into host cells.
In some embodiments, a polypeptide can be administered to a subject in combination with another suitable therapy. For example, in some embodiments, a polypeptide can be administered to a subject in combination with a composition comprising a therapeutic antibody. In some embodiments, a therapeutic antibody can include a monoclonal antibody to FcγRIIb including, for example, SuppreMol SM201 or Xencor XmAb5871. The composition comprising monoclonal antibody to FcγRIIb can be administered to a subject before, during, or after administration of a composition comprising the polypeptide.
In some embodiments, a polypeptide can be administered to a subject in combination with an composition including an antiretroviral including, for example, oseltamivir, zanamivir, peramivir, etc. The composition comprising the antiretroviral can be administered to a subject before, during, or after administration of a composition comprising the polypeptide.
In some embodiments, a polypeptide can be administered to a subject in combination with an composition including a drug approved for treating hepatitis including sofosbuvir and/or ledipasvir. The composition comprising the drug approved for treating hepatitis can be administered to a subject before, during, or after administration of a composition comprising the polypeptide.
Ebola is a filamentous and pleomorphic virus, attributes that are important in creating a “Velcro effect” possibly contributing to viral replication and immunopathogenicity. There have been five different viral sub-types that have been recognized: Ebolavirus Zaire (ZEBOV), Sudan Ebolavirus (SUDV or SEBOV), the Tai Forest Ebolavirus (TAFV), the Reston Ebolavirus (RESTV or REBOV) and the Bundibugyo Ebolavirus (BDBV). Each of these is pathogenic for humans except RESTV that so far has only been shown to be pathogenic for nonhuman primates (Journal of Autoimmunity xxx (2014) 1e9 Article in Press Ansari. Clinical features and pathobiology of Ebolavirus infection Review). Another filovirus, Lloviu virus (LLOV) appears to be pathogenic in bats (PLoS Pathog. 2011 7(10) e1002304 Negredo et al Discovery of an ebolavirus-like filovirus in Europe). Pathogenicity varies among Ebola viruses, from ZEBOV, which is highly lethal in humans, to REBOV, which causes disease in pigs and macaques but asymptomatically infects humans (Emerg Infect Dis. 2013 19(2) 270-3 Olival et al Ebola virus antibodies in fruit bats, Bangladesh).
Despite relatively a large population living in areas of risk and the widespread practice of bush-meat hunting in these predicted areas, Ebolavirus is rare both in suspected animal reservoirs and in terms of human outbreaks. It has been shown that the human population living within this niche is larger, more mobile and better internationally connected than when the pathogen was first observed. As a result, when spillover events do occur, the likelihood of continued spread amongst the human population is greater, particularly in areas with poor healthcare infrastructure. Whilst rare in comparison to other high burden diseases prevalent in this region, such as malaria, Ebola outbreaks can have a considerable economic and political impact, and the subsequent destabilization of basic health care provisioning in affected regions increases the toll of unrecorded morbidity and mortality of more common infectious diseases, throughout and after the epidemic period. The number of concurrent infections during the present outbreak represents a significant strain on healthcare systems that are already poorly provisioned (eLife 2014 3 e04395 Pigott et al Mapping the zoonotic niche of Ebola virus disease in Africa and references incorporated therein). No Ebola outbreaks were recorded prior to 1976, and the frequency of Ebola outbreaks has increased since 2000 (supra). At the same time, Globally, malaria cases and deaths grew rapidly from 1990 reaching a peak of 232 million cases (143 million to 387 million) in 2003 and 1.2 million deaths (1.1 million to 1.4 million) in 2004 (Murray et al Lancet 2014 384 9947 1005-1070 Global regional and national incidence and mortality for HIV tuberculosis and malaria during 1990 2013 a systematic analysis for the Global Burden Study 2013).
It has recently been shown that host genetics plays a very important role in the pathogenicity of EBOV infections, as a single strain of mouse adapted EBOV caused pathogenicity ranging from asymptomatic infections to fulminant infections closely resembling viral hemorrhagic fever, depending on the genetic makeup of the mice (Rasmussen et al Science Express 30 Oct. 2014 Page 1-10 Host genetic diversity enables Ebola hemorrhagic fever pathogenesis and resistance). Mice from the Collaborative Cross exhibit distinct disease phenotypes following mouse-adapted Ebola virus infection. Phenotypes range from complete resistance to lethal disease to severe hemorrhagic fever characterized by prolonged coagulation times and 100% mortality. Inflammatory signaling was associated with vascular permeability and endothelial activation, and resistance to lethal infection arose by induction of lymphocyte differentiation and cellular adhesion, likely mediated by the susceptibility allele Tek. These data indicate that genetic background determines susceptibility to Ebola hemorrhagic fever (supra).
These data suggest that EHF is characterized by earlier induction of a larger magnitude transcriptional response. In susceptible mice relative to resistant mice, genes associated with EBOV infection were differentially induced. Early in infection in the spleens of susceptible mice at day 1 p.i., we observed enrichment of p38 MAPK and ERK signaling processes that stimulate productive EBOV infection (supra). This observation suggests that activation of the immune system by p38 MARK and EKR should be conducive to EBOV replication, and a lack of immune activation by p38 MARK and EKR should contribute to abortive EBOV replication, possibly causing asymptomatic EBOV infections.
Consistent with this conclusion is the observation that the number of EBOV seropositive apparently asymptomatic individuals is much higher than previously thought (PLoS One. 2010 5(2) e9126 Becquart et al High prevalence of both humoral and cellular immunity to Zaire ebolavirus among rural populations in Gabon). The evidence that mild or asymptomatic EBOV infections occur can be found in several observations. First was the observations that in the 1976 SEBOV outbreak in Southern Sudan, the WHO found Ebola virus antibodies in 25 (19%) of 131 Maridi case-contacts and in 7 (19%) of 64 hospital staff contacts (that did not show any clinical signs of EBOV infection) indicates that Ebola virus can cause mild illness and even subclinical infections. . . . The antibody results with sera collected from the Nzara cotton factory indicate that 9 (37%) of the 24 staff . . . were infected . . . 7 (of the nine) gave no history of illness (WHO bulletin_1978_56(2)_247-270).
Further evidence of widespread asymptomatic Ebola infections has been found in a large Ebola seroprevalence study performed in Gabon. To better understand Zaire ebolavirus (ZEBOV) circulation and transmission to humans, Becquart et al. conducted a large serological survey of rural populations in Gabon, a country characterized by both epidemic and non-epidemic regions. The survey lasted three years and covered 4,349 individuals from 220 randomly selected villages, representing 10.7% of all villages in Gabon. Using a sensitive and specific ELISA method, Becquart et al. found a ZEBOV-specific IgG seroprevalence of 15.3% overall, the highest ever reported. The seroprevalence rate was significantly higher in forested areas (19.4%) than in other ecosystems, namely grassland (12.4%), savannah (10.5%), and lake land (2.7%). No other risk factors for seropositivity were found. The specificity of anti-ZEBOV IgG was confirmed by Western blot in 138 individuals, and CD8 T cells from seven IgG+ individuals were shown to produce IFN-c after ZEBOV stimulation. Together, these findings show that a large fraction of the human population living in forested areas of Gabon has both humoral and cellular immunity to ZEBOV (PLoS One. 2010 5(2) e9126 Becquart et al High prevalence of both humoral and cellular immunity to Zaire ebolavirus among rural populations in Gabon).
It is important to realize that the high mortality rate associated with Ebola Zaire may require other factors than simply exposure to an extremely pathogenic virus. It is generally accepted that ZEBOV is associated with a case fatality rate of about 90%, but this may be an overestimate. First, seven cases of asymptomatic infection were identified during the 1996 Booué outbreak in Gabon. Second, some ELISA-based serosurveys have shown high antibody prevalence rates among populations living in areas where no cases of EHF have ever been reported, suggesting that ZEBOV might also be capable of causing mild illness or even asymptomatic infection in humans. The IgG seroprevalence was 9.3% in villages located in the 1995 outbreak area around Kikwit, DRC, where no EHF cases were reported. Likewise, a seroprevalence of 13.2% was found in the Aka Pygmy population of Central African Republic, where no ZEBOV outbreaks have ever been reported (supra).
Certainly it can be argued that these numbers represent naturally immune individuals, however in the case of dengue viral infections (DENV), first infections without any evidence of antibody dependent enhancement of infection (ADE) rarely develop into Dengue Hemorrhagic Fever (DHF) and most cases of DHF involve ADE as part of the immunopathogenesis of DHF, possibility suggesting that ADE maybe a factor in the immunopathogenesis of other VHFs.
The other two examples of more widespread EBOV infections/prevalence than was previously thought come from the observations of Ebola Reston (REBOV) infection in domestic swine in both the Philippines and China co-infected with porcine reproductive and respiratory syndrome virus (PRRSV) demonstrating REBOV in Asia and the report that ZEBOV and Marburg virus (MARV) has been found in fruit bats in Bangladesh (Olival et al. Emerg Infect Dis. 2013 19(2) 270-3, Olival et al, Ebola virus antibodies in fruit bats, Bangladesh). To determine geographic range for Ebola virus, Olival et al. tested 276 bats in Bangladesh. Five (3.5%) bats were positive for antibodies against Ebola Zaire and Reston viruses; no virus was detected by PCR. These bats might be a reservoir for Ebola or Ebola-like viruses, and extend the range of filoviruses to mainland Asia (supra).
The presence of high seroprevalence rate in very geographically diverse areas and serological evidence of past EBOV mild or symptomatic infections suggests that EBOV is much more prevalent than thought and the occurrence of widespread EHF may involve factors other than simply exposure to a highly virulent pathogen (supra).
Another key to understanding the immunopathogenesis of EBOV infection is the observation that B cell knock-out (KO) mice, which express no antibodies, have partial immunity and develop persistent Ebola infections. Using a mouse model, Gupta et al. determined the role of the immune system in clearance of and protection against Ebola virus. All CD8 T-cell-deficient mice succumbed to subcutaneous infection and had high viral antigen titers in tissues, whereas mice deficient in B cells or CD4 T cells cleared infection and survived, suggesting that CD8 T cells, independent of CD4 T cells and antibodies, are critical to protection against subcutaneous Ebola virus infection. B-cell-deficient mice that survived the primary subcutaneous infection (vaccinated mice) transiently depleted or not depleted of CD4 T cells also survived lethal intraperitoneal rechallenge for >25 days. However, all vaccinated B-cell-deficient mice depleted of CD8 T cells had high viral antigen titers in tissues following intraperitoneal rechallenge and died within 6 days, suggesting that memory CD8 T cells by themselves can protect mice from early death. Surprisingly, vaccinated B-cell-deficient mice, after initially clearing the infection, were found to have viral antigens in tissues later (day 120 to 150 post-intraperitoneal infection). Furthermore, following intraperitoneal rechallenge, vaccinated B-cell-deficient mice that were transiently depleted of CD4 T cells had high levels of viral antigen in tissues earlier (days 50 to 70) than vaccinated undepleted mice. This demonstrates that under certain immunodeficiency conditions, Ebola virus can persist and that loss of primed CD4 T cells accelerates the course of persistent infections. These data show that CD8 T cells play an important role in protection against acute disease, while both CD4 T cells and antibodies are required for long-term protection, and they provide evidence of persistent infection by Ebola virus suggesting that under certain conditions of immunodeficiency a host can harbor virus for prolonged periods, potentially acting as a reservoir (J Virol 2004 78 2 958-967 Gupta et al Persistent Infection with Ebola Virus under Conditions of Partial Immunity).
Previous reports suggest that one of two outcomes occurs with Ebola virus infection in humans and nonhuman primates: either the virus produces an overwhelming infection that rapidly leads to death of the host, or it is cleared by a vigorous immune response that results in complete recovery of the host. Thus, Ebola hemorrhagic fever is characteristically an acute illness, and the outcome usually becomes apparent fairly early in the course of infection; a prolonged course of infection has not been reported (supra).
The virus replicates in a variety of cell types, including macrophages, epithelial cells, hepatocytes, and endothelial cells. Viral replication in these cells induces high levels of inflammatory chemokines and cytokines that may be responsible for the inflammatory pathology observed during the early phase of infection. However, alpha/beta interferon responses, which would normally inhibit viral replication and dissemination, are suppressed by the virus. Binding of the Ebola virus viral glycoprotein to endothelial cells induces cytotoxic effects and increases vascular permeability, which may provide a mechanism for endothelial cell leakage in later stages of infection. Evidence from human studies suggests that a poor cellular immune response (as measured by low levels of gamma interferon and CD8 T-cell activation markers in serum) and low levels of anti-Ebola virus immunoglobulin G are associated with fatal infections. In contrast, convalescent patients have high levels of anti-Ebola virus immunoglobulin G and typically clear the infection within 3 weeks after onset of symptoms. Studies in animal models suggest that the presence of high titers of antibodies can protect the host from fatal infection. However, neither the mechanisms of protection during natural infection nor the elements of the immune response that are responsible for viral clearance are well understood (supra).
A mouse model of Ebola virus infection has been developed for use in studying immune responses to the virus in an attempt to understand the correlates of protective immunity. In this model, subcutaneous infection with an adapted Ebola virus results in a nonfatal infection associated with long term immunity against lethal rechallenge. Using this model, we show that CD8 T cells play a crucial role in the initial clearance of the virus following primary and secondary (rechallenge) infections and that CD4 T cells and antibodies are not required for short-term protection. However, in the absence of B cells and antigen-specific CD4 T cells, Ebola virus establishes a persistent asymptomatic infection, with disease symptoms appearing only during the late stage of infection. These data indicate that short-term control of the virus is achieved by CD8 T cells alone, but long-term control requires the presence of antibodies and CD4 T cells (supra).
Passive transfer of high-titer polyclonal antibodies from vaccinated Ebola virus-immune cynomolgus macaques to naive macaques failed to confer protection against disease, suggesting a limited role of humoral immunity. In contrast, depletion of CD8(+) T cells in vivo after vaccination and immediately before challenge eliminated immunity in two vaccinated macaques, indicating a crucial requirement for T cells in this setting. The protective effect was mediated largely by CD8(+) cells, as depletion of CD8(+) cells in vivo using the cM-T807 monoclonal antibody (mAb), which does not affect CD4(+) T cell or humoral immune responses, abrogated protection in four out of five subjects (Nat Med. 2011 17(9) 1128-31 Sullivan et at CD8+ cellular immunity mediates rAd5 vaccine protection against Ebola virus infection of nonhuman primates).
Consistent with the observation that activation of mitogen-activated protein kinase (MAPK) is conducive to Ebola viral replication is the finding that inhibitors of p38 MAPK can abort fatal Ebola infections: Antigen presenting cells (APCs), including macrophages and dendritic cells, are early and sustained targets of Ebola virus (EBOV) infection in vivo. EBOV activates mitogen-activated protein kinase (MAPK) signaling upon infection of APCs. Pyridinyl imidazole inhibitors of p38 MAPK on EBOV infection of human APCs and EBOV mediated cytokine production from human DCs. The p38 MAPK inhibitors reduced viral replication in PMA-differentiated macrophage-like human THP-1 cells and primary human monocyte-derived dendritic cells (MDDCs) and cytokine production from EBOV-treated MDDCs was inhibited in a dose-dependent manner (Antiviral Res 2014 107 102-9 Johnson et al Pyridinyl imidazole inhibitors of p38 MAP kinase impair viral entry and reduce cytokine induction by Zaire ebolavirus in human dendritic cells). These results suggest that activation of p38 MAPK and ERK is necessary for productive EBOV infection. Since activation of macrophages/DC in the presence of immune complexes (IC) results in the activation of p38 MAPK and ERK, EBOV IC would be expected to enhance EBOV infection (supra).
It is important to realize that IC by themselves do not trigger activation of the immune system, rather activation of MAPK requires both IC and an antigenic stimulus:
Strong et al. reported a model system in which infection of mouse and bat cell lines with EBOV leads to persistence, which can be broken with low levels of lipopolysaccharide or phorbol-12-myristate-13-acetate (PMA). This reactivation depends on the Ras/MAPK pathway through inhibition of RNA-dependent protein kinase and eukaryotic initiation factor 2α phosphorylation and occurs at the level of protein synthesis. EBOV also can be evoked from mice 7 days after infection by PMA treatment, indicating that a similar mechanism occurs in vivo. Our findings suggest that EBOV may persist in nature through subclinical infection of a reservoir species, such as bats, and that appropriate physiological stimulation may result in increased replication and transmission to new hosts. Identification of a presumptive mechanism responsible for EBOV emergence from its reservoir underscores the “hit-and-run” nature of the initiation of human and/or nonhuman primate EBOV outbreaks (PNAS 2008 105(46) 17982-7 Strong et al Stimulation of Ebola virus production from persistent infection through activation of the Ras-MAPK pathway).
An obvious trigger for productive EBOV replication in bats is blood parasites belonging to Haemosporida: Bats are the hosts to a large array of blood parasites (e.g. Bartonella, piroplasms, trypanosomes and microfillaria). In particular, bats are host to a unique collection of Haemosporida (Apicomplexa). Besides Plasmodium spp. and the rarer Hepatocystis spp., which infect several orders of Mammalia, bats host at least two unique genera not found outside the Chiroptera, Nycteria and Polychromophilus, plus two additional genera known from a single record (Dionisia and Biguetellia). The diversity of haemosporidian parasites of bats suggests, together with a recent phylogeny, that the Chiroptera might have been the original host of all mammalian Haemosporida (Parasit Vectors. 2014 7(1) 566 Witsenburg et al Epidemiological traits of the malaria-like parasite Polychromophilus murinus in the Daubenton's bat Myotis daubentonii). If both weaker condition and younger age are associated with higher infection intensity, then the highest selection pressure exerted by P. murinus should be at the juvenile stage (supra).
This finding is consistent with the seasonal pulses of Marburg in bats: Marburg virus, like its close relative Ebola virus, can cause large outbreaks of hemorrhagic fever with case fatalities nearing 90%. For decades the identity of the natural reservoir was unknown. However, in 2007 Marburg viruses were isolated directly from Egyptian fruit bats (Rousettus aegyptiacus) that inhabited a Ugandan gold mine where miners were previously infected. Soon after, two tourists became infected with Marburg virus after visiting nearby Python Cave, a popular attraction in Queen Elizabeth National Park, Uganda. This cave also contained R. aegyptiacus bats (40,000 animals). These events prompted a long-term investigation of Python Cave to determine if, 1) R. aegyptiacus in the cave carried infectious Marburg virus genetically similar to that found in the tourists, and 2) what ecological factors might influence virus spillover to humans. In the study, we found that, 1) approximately 2.5% of the bat colony is actively infected at any one time and that virus isolates from bats are genetically similar to those from infected tourists, and 2) specific age groups of bats (juveniles, six months of age) are particularly likely to be infected at specific times of the year that roughly coincide with historical dates of Marburg virus spillover into humans (Author summary, Amman et al PLos Pathogens October 2012 Volume 8 Issue 10 e1002877 Seasonal Pulses of Marburg Virus Circulation in Juvenile Rousettus aegyptiacus Bats Coincide with Periods of Increased Risk of Human Infection).
The approximate dates of 13 suspected Marburg virus spillover events were determined from the literature. . . . When all 13 Marburg virus spillover events are listed by month of occurrence, the data show a temporal clustering of human infections, coinciding with the summer (mid-June through mid-September) and winter months (mid-December through mid-March) of the northern hemisphere. The majority of spillover events (7/13) involved resident African miners, suggesting that the clustering effect was not due to seasonal tourism. More importantly, when the dates of these 13 spillover events are compared to a sinusoidal curve derived from the field collection data showing the seasonal incidence of juvenile R. aegyptiacus infections (
Ebola outbreaks in humans also have a similar seasonality, Ebola outbreaks in great apes have always been reported at the beginning of the dry seasons (December 1995 in Mayibout, July 1996 in Booué, July 2001 in Mekambo, December 2001 in Kelle, and December 2002 in the second Kelle outbreak). Thus, Ebola outbreaks probably do not occur as a single outbreak spreading throughout the Congo basin as others have proposed, but are due to multiple episodic infection of great apes from the reservoir (Science 2004 303 5656 387-390 Leroy et al Multiple Ebola virus transmission events and rapid decline of central African wildlife).
Ebola infections are characterized by high levels of IL-10 (Journal of Autoimmunity xxx (2014) 1e9 Article in Press Ansari. Clinical features and pathobiology of Ebolavirus infection Review), suggesting that an immune mechanism that stimulates high levels of IL-10 would be conducive to Ebola virus replication:
Activation of macrophages in the presence of immune complexes increases the production of IL-10 and reduces IL-12 production (J Immunol. 2005 175(1) 469-77 Lucas et al ERK activation following macrophage FcγR ligation leads to chromatin modifications at the IL-10 locus). Enhanced production of IL-10 correlates with a rapid and enhanced activation of two MAPKs, ERK and p38 (supra). We feel that this response to FcγR ligation is a universal response that is a general property of most, if not all, macrophages. In the present work we sought to determine the mechanism whereby IL-10 was induced in response to immune complexes. Immune complexes alone were not sufficient to induce IL-10. Rather cytokine production required both the stimulation (such as LPS) and the addition of immune complexes (IC). Only the combination of these two stimuli resulted in high levels of IL-10 production (supra). This observation suggests that a pathogen that increases circulating immune complexes and presents an antigenic stimulus may favor EBOV replication and therefore be a cofactor for Filoviruses via ADE.
Since it has been suggested that activation of the immune system by p38 MARK and EKR should be conducive to EBOV replication (Rasmussen et al Science Express 2014 1 10 1126 Host genetic diversity enables Ebola hemorrhagic fever pathogenesis and resistance), the effect of high circulating IC, or more importantly, the presence of antigenic stimulus and IC in REBOV/PRRSV co-infected pigs may be conducive to REBOV infection in pigs and serves as an in vivo example of an Ebola cofactor, wherein the cofactor facilitates Ebola viral replication and infection.
An in vivo example of such an enhancement due to co-infection with PRRSV can be found in REBOV infection in pigs. An example of a concurrent viral infection as a possible cofactor for Ebola infectivity can be found in Ebola Reston infection of pigs in both the Philippines and China. The only instances of clinical (not experimental) Ebola Reston (REBOV) infection in domestic swine in both the Philippines and China have been when the pigs were also co-infected with porcine reproductive and respiratory syndrome virus (PRRSV) that were experiencing a severe respiratory disease syndrome (Science 2009 325(5937) 204-6 Barrette et al Discovery of swine as a host for the Reston ebolavirus Arch Virol. 2014 159(5) 1129-32, Pan et al Reston virus in domestic pigs in China). Since there have been no clinical reports of REBOV infection without co-infection of swine with PRRSV it appears that the co-infection REBOV with PRRSV maybe an obligate part of clinical REBOV infection in pigs.
Polyclonal B cell activation and hypergammaglobulinemia occur in association with various viral infections that stimulate type I IFNs that in turn enhance B cell proliferation. This hypergammaglobulinemia is often associated with autoimmunity perhaps because of nonspecific proliferation of B cells expressing a preimmune-like repertoire that is known to be polyreactive and to recognize autoantigens. Although previous spectratypic analyses show that B cell CDR3s from PRRSV infected piglets were a signature for polyclonal activation, certain HCDR3 lengths were pronounced (JI 2007 178 6320-6331 Bulter et al Antibody Repertoire Development in Fetal Cells with Hydrophobic HCDR3s and Neonatal Piglets-XIX. Undiversified B Antibody Repertoire Development in Fetal Cells Preferentially Proliferate in the PRRSV and references incorporated therein).
Data presented herein show that so-called polyclonal B cell activation in this viral infection is instead selective expansion of B cells with hydrophobic HCDR3s that are normally deselected during development to yield an oligoclonal population with hydrophobic HCDR3s. This biased expansion means that the normally dominant, neutral-charged HCDR3 population seen in newborns and other treatment groups is poorly represented in the VH repertoire, consistent with immune dysregulation in this disease. This effect appears to be due to selective proliferation of naive B cells of the preimmune repertoire that do not diversify We assume that the Igs responsible for the hypergammaglobulinemia in PRRSV-infected piglets result from the B cells with hydrophobic HCDR3s that we report here. The alternative is that the secreted Igs are not derived from the predominant B cells but rather from a minor population within the hydropathicity spectrum (supra).
There are few clues to explain B cell selection during PRRSV infection and no published evidence that PRRSV infects B cells. Viral epitopes are generally hydrophilic glycoproteins, but amphipathic helices that can be hydrophobic are present in ORF proteins including PRRSV (supra).
The polyclonal expansion of B cells by PRRSV is a classic example of a B cell superantigen: The fact that B cells recognize Ag differently than T cells-soluble Ag versus MHC class I1-associated peptides-suggests that Ig-SAg will structurally and functionally differ from T-SAg. Nevertheless, we can use the T-SAg as a model to predict the minimum requirements for an Ig-SAg. First, an Ig-SAg would be expected to bind primarily to the F(ab) region of the Ig molecule (i.e., VH-DH-JH and/or VL-JL). Second, an Ig-SAg would bind to a family of Ig based on a common sequence and/or tertiary structure of the F(ab). This would predict that analogous to a T-SAg an Ig-SAg would bind to a substantially larger B cell population than a conventional Ag (Am J Pathol. 1994 144(4) 623-36 Goodglick et al Revenge of the microbes: Superantigens of the T and B cell lineage). The first example of an Ig-SAg is a phage-encoded membrane protein of S. aureus, protein A. In addition to the well characterized binding site of protein A on the Fc portion of IgG molecules, there is an independent binding site for protein A in the F(ab) region of a subfraction of Ig molecules. Surprisingly, the alternate binding site of protein A was found to be specific for VH3 family Ig. VH3 is the largest VH family consisting of 30 or more members. Binding of protein A to VH3 was independent of isotype (heavy chain constant region) or light chain usage (supra).
S. aureus Cowan (SAC) is a well-known mitogen and differentiative agent for B cells, and protein A is a necessary component of this activity. Recent studies have demonstrated that SAC and purified protein A specifically activate VH3-expressing human B cells. A second example of a putative Ig-SAg is the outer envelope glycoprotein of the HIV, gp120 (supra, Int Immunol. 2000 12(3) 305-12 Neshat et al Mapping the B cell superantigen binding site for HIV-1 gp120 on a V(H)3 Ig). This protein is responsible for the binding of HIV to CD4 on the surface of T cells and other CD4-expressing cells and is therefore critical to the infection of CD4 cells. An important and poorly explained feature of HIV infection is the striking polyclonal activation of B lymphocytes in this disease, resulting in clinical manifestations including lymphoid hyperplasia, hypergammaglobulinemia, autoantibody-mediated autoimmune disorders, and in late infection a dramatically increased frequency of B cell lymphoma. HIV gp120 binds to a subpopulation (4 to 8%) of normal B cells from uninfected, seronegative individuals. This subpopulation of B cells did not express CD4, but rather bound gp120 via membrane Ig of the VH3 gene family. The direct interaction of gp120 with VH3 was confirmed by cell-free binding studies of gp120 with purified VH3 antibodies. Functionally, gp120 served as a surrogate Ag for the in vitro activation and Ig secretion by VH3 B cells. In clinical HIV infection, this interaction is correlated with selective expansion of the VH3 B cells and serum VH3 IgM (in healthy seropositive individuals), followed by a profound VH3 B cell deletion (in individuals with AIDS). This array of findings strongly implicates HIV gp120 as an Ig-SAg for the VH3 Ig family (supra). Since HIV infection creates similar immunological conditions as PRRSV, HIV is very likely a co-factor accelerating EBOV replication and pathogenicity.
It is also important to realize that anti-SIV gp120 antibodies can cross react with VH3 immunoglobulins, which has to be taken into account when designing a vaccine for Ebola (Scand J Immunol. 2003 57(3) 239-45 Zigment-Reed et al Cross-reaction of anti-simian immunodeficiency virus envelope protein antibodies with human immunoglobulins). This is important in that any EBOV vaccine candidate that stimulates autoimmunity will likely fail to protect against actual Ebola infections.
Another example of a viral expansion of self-reactive VH CDR3s is found in HCV infections. Analysis of the immunoglobulin receptor (IGR) variable heavy- and light-chain sequences on 17 hepatitis C virus (HCV)-associated non-Hodgkin lymphomas (NHLs) (9 patients also had type II mixed cryoglobulinaemia [MC] syndrome and 8 had NHL unrelated to MC) and analysis of intraclonal diversity on 8 of them suggest that such malignant lymphoproliferations derive from an antigen-driven pathologic process, with a selective pressure for the maintenance of a functional IgR and a negative pressure for additional amino acid mutations in the framework regions (FRs). For almost all NHLs, both heavy- and light-chain complementarity-determining regions (CDR3) showed the highest similarity to antibodies with rheumatoid factor (RF) activity that have been found in the MC syndrome, thus suggesting that a common antigenic stimulus is involved in MC syndrome and in HCV-associated lymphomagenesis. Moreover, because HCV is the recognized pathologic agent of MC and the CDR3 amino acid sequences of some HCV-associated NHLs also present a high homology for antibody specific for the E2 protein of HCV, it may be reasonable to speculate that HCV E2 protein is one of the chronic antigenic stimuli involved in the lymphomagenetic process. Finally, the use of specific segments, in particular the D segment, in assembling the IgH chain of IgR seems to confer B-cell disorders with the property to produce antibody with RF activity, which may contribute to the manifestation of an overt MC syndrome (Blood. 2000 96(10) 3578-84 De Re et al Sequence analysis of the immunoglobulin antigen receptor of HCV-associated non-Hodgkin lymphomas suggests that the malignant cells are derived from the RF-producing cells and type II cryoglobulinea). The presence of both IC and superantigen activity in HCV infections suggests that HCV may be a cofactor in Ebola infections.
It is important to note that HCV core protein also expresses a viral FcγR, capable of binding any IC: Maillard et al. have previously demonstrated that viral particles with the properties of nonenveloped hepatitis C virus (HCV) nucleocapsids occur in the serum of HCV-infected individuals. We show here that nucleocapsids purified directly from serum or isolated from HCV virions have FcγR-like activity and bind nonimmune IgG via its Fcγ domain. HCV core proteins produced in Escherichia coli and in the baculovirus expression system also bound nonimmune IgG and their Fcγ fragments. Folded conformation was required for IgG binding because the FcγR-like site of the core protein was inactive in denaturing conditions. Studies with synthetic core peptides showed that the region spanning amino acids 3-75 was essential for formation of the IgG-binding site. The interaction between the HCV core and human IgG is more efficient in acidic (pH 6.0) than in neutral conditions. The core protein-binding site on the IgG molecule differs from those for C1q, FcγRII (CD32), and FcγRIII (CD16) but overlaps with that for soluble protein A from Staphylococcus aureus (SpA), which is located in the CH2-CH3 interface of IgG. These characteristics of the core-IgG interaction are very similar to those of the neonatal FcRn.
Surface plasmon resonance studies suggested that the binding of an anti-core antibody to HCV core protein might be bipolar through its paratope to the corresponding epitope and by its Fcγ region to the FcγR-like motif on this protein. These features of HCV nucleocapsids and HCV core protein may confer an advantage for HCV in terms of survival by interfering with host defense mechanisms mediated by the Fcγ part of IgG (J Biol Chem. 2004 279(4) 2430-7 Maillard et al Fc gamma receptor-like activity of hepatitis C virus core protein).
The observation that REBOV replication appears to be enhanced in the presence of hydrophobic IC, similar to the immunopathology of HCV infections/MC syndrome, where the immune response is not simply diverted away from the Ebola virus, but directed towards self-antigens, particularly those with RF specificity, has important ramifications in understanding Ebola immunopathogenesis. An analysis of immunoglobulin binding proteins from a variety of pathogens suggests that the use of hydrophobic amino acid anchor residues present on a viral FcγR are likely to be directed towards the IgG Fc CHγ2-CHγ3 cleft may be a common denominator in the immunopathogenesis of these pathogens.
A similar immunopathology of superantigen, IC and viral FcγR/immunoglobulin binding protein can be found in herpes viral infections: A T cell superantigen and selective activation of certain Plasma Cells by the Viral M2 Superantigen has been described for herpes virus (Plos One 2014 10 8 e1004302 O'Flaherty et al The Murine Gammaherpesvirus Immediate-Early Rta Synergizes with IRF4, Targeting Expression of the Viral M1 Superantigen to Plasma Cells).
Based on the analysis of M2 function, we propose that M2 falls into a new class of herpesvirus genes that do not directly impact virus replication, but rather facilitate virus reactivation from latency by manipulating cellular differentiation/activation leading to a reactivation competent cellular environment. We have adopted the term reactivation conditioner for such genes. In the case of viruses that establish latency in memory lymphocytes, it is attractive to speculate that it may be necessary to encode functions that drive quiescent memory B or T cells into a state which is more conducive to virus replication. With respect to latency established in memory B cells, plasma cells would appear particularly well suited to support herpesvirus replication. As such, we hypothesize that manipulation of plasma cell differentiation leading to virus reactivation from latently infected memory B cells is relevant to reactivation of the human gammaherpesviruses. Although there is no obvious M2 homolog in either EBV or KSHV, there are several well documented examples of conserved functions encoded by gammaherpesvirus latency-associate gene products that lack obvious sequence homology. Indeed, our previous observation that M2 expression in primary murine B cells triggers IL-6 and IL-10 expression, recapitulates functions modulated by both EBV and KSHV, and provides further evidence of pathogenic strategies that are conserved among this family of viruses (supra).
Herpes Simplex Virus 1 (HSV-1) infects 40-80% of adults worldwide. HSV-1 initiates infection at mucosal surfaces and spreads along sensory neurons to establish a life-long latent infection that can lead to neurological diseases. Humans usually develop IgG antibodies that specifically recognize pathogens via fragment antigen binding (Fab) variable regions. HSV-1 can avoid the protective effects of antibodies by producing gE-gI, a receptor that binds to the constant portion of IgGs (Fc), thereby tethering the antibody in a position where it cannot trigger downstream immune functions. A gE-gI-bound IgG can participate in antibody bipolar bridging (ABB) such that the Fabs bind a viral antigen and the Fc binds gE-gI. The fate of ABB complexes had been unknown. We used live cell fluorescent imaging to follow ABB complexes during their formation and transport within a cell. We demonstrated that ABB assemblies were internalized into acidic intracellular compartments, where gE-gI dissociated from IgG-viral antigen complexes and the IgG and antigen were targeted for degradation within lysosomes. These results suggest that gE-gI mediates clearance of infected cell surfaces of both anti-viral IgGs and viral antigens, a general mechanism to facilitate latent infection by evading IgG mediated responses (Ndjamen et al PLoS Pathogens 2014 10 3 e1003961 the Herpes Virus Fc Receptor gE gl mediates Antibody Bipolar Bridging to Clear Viral Antigens from the Cell Surface).
Herpes Simplex Virus (HSV), Varicella-Zoster Virus (VZV), and Pseudorabies Virus (PrV) are members of the alpha herpes virus family, which are characterized by a relatively short replicative cycle in epithelial tissues and egression to and latent infection of the sensory neurons. Alpha herpes viruses have evolved many strategies to evade the host immune system. For example, antibodies do not appear to function effectively in clearance of HSV-1. It has been shown that the severity and persistence of HSV-1 lesions do not correlate with serum levels of neutralizing antibodies in infected individuals. HSV-1 encodes type 1 transmembrane glycoproteins, glycoprotein E (gE) and glycoprotein I (gI), that are displayed on the surface of infected cells and virions. Together they function as a receptor for the Fc region of human immunoglobulin G (IgG) and have also been implicated in cell-to-cell spread of virus. In addition, gE is required for HSV-1 movement inside both neuronal and epithelial cells. The Fc receptor function of gE-gI, which hinders access to the IgG Fc region and thus allows HSV-infected cells to escape recognition by Fc-dependent effector cells, may serve as a mechanism to block antibody-related host defenses (Ndjamen et al PLoS Pathogens 2014 10 3 e1003961 the Herpes Virus Fc Receptor gE gl mediates Antibody Bipolar Bridging to Clear Viral Antigens from the Cell Surface and references incorporated therein).
Antibody bipolar bridging (ABB), in which an anti-viral IgG bound to a cell surface antigen also binds to an Fc receptor, has the potential to protect virions and infected cells from IgG mediated immune responses. gE-gI is an HSV-1 heterodimeric complex that can function as a receptor for human IgGs by binding to their Fc regions, thus it can mediate ABB in HSV-1-infected cells. Experiments performed in HSV-1-infected cells to compare the efficacy of IgGs that can or cannot form ABB complexes suggested that bipolar bridging protects HSV-1 and HSV-1-infected cells from antibody- and complement-dependent neutralization, antibody-dependent cell-mediated cytotoxicity, and granulocyte attachment (supra). These observations suggest that the presence of a superantigen, IC and a viral FcγR/IBP found in herpes viral infections would be conducive to Ebola viral replication and that herpes viral infections may be cofactors for Ebola infections.
Similar to Ebola, B cell deficient mice are resistant to Malaria infections and developing cerebral Malaria, an important aspect of serious Malaria contributing to the morbidity and mortality of Malaria infected individuals. B-cell-deficient mice, devoid of immunoglobulins, exhibited increased survival and delayed onset of disease. Histopathology revealed striking differences, with a lower degree of microvascular hemorrhage in the B-cell-deficient mice (M Bio. 2014 5(2) e00949-14 Oliveria et al Increased survival in B-cell-deficient mice during experimental cerebral malaria suggests a role for circulating immune complexes).
ICs have proinflammatory properties, and indeed, studies currently being carried out by Oliveria et al have shown that human peripheral blood mononuclear cells stimulated with ICs isolated from the serum of individuals with Plasmodium vivax malaria secrete interleukin-6, tumor necrosis factor, and IL-1 (D. Golenbock and R. Gazzinelli, unpublished observations). The loss of CR1 that Oliveria et al proposed coincides with a rise in IgG- and IgM containing ICs and may represent an attempt to clear these proinflammatory complexes from the circulation (supra). Altogether, we propose that CIC plays a major role in the pathogenesis of cerebral Malaria and that immunoglobulin deficiency alters the disease outcome following P. berghei ANKA infection (supra).
Complement receptor 1 (CR1) expressed on the surface of phagocytic cells binds complement bound IC (C3b opsonized) playing an important role in the clearance of circulating immune complexes (IC). This receptor is critical to prevent accumulation of IC, which can contribute to inflammatory pathology.
Accumulation of circulating IC is frequently observed during malaria, although the factors contributing to this accumulation are not clearly understood. Oliveria et al observed that the surface expression of CR1 on monocyte/macrophages and B cells is strongly reduced in mice infected with Plasmodium yoelii, a rodent malaria model. Monocyte/macrophages from these infected mice present a specific inhibition of complement-mediated internalization of IC caused by the decreased CR1 expression. Accordingly, mice show accumulation of circulating IC and deposition of IC in the kidneys that inversely correlates with the decrease in CR1 surface expression. The results reported by Oliveria et al indicate that malaria induces a significant decrease on surface CR1 expression in the monocyte/macrophage population that results in deficient internalization of IC by monocyte/macrophages. To determine whether this phenomenon is found in human malaria patients, Oliveria et al analyzed 92 patients infected with either P. falciparum or P. vivax, the most prevalent human malaria parasites. The levels of surface CR1 on peripheral monocyte/macrophages and B cells of these patients show a significant decrease compared to uninfected control individuals in the same area. Oliveria et al proposed that this decrease in CR1 plays an essential role in impaired IC clearance during malaria (supra).
TCR Vβ usage was examined in C57BL/6 mice infected with Plasmodium yoelii. In addition to a polyclonal T cell activation, already described, a superantigenic-like activity was observed during the acute infection. This superantigenic activity induces a preferential deletion without prior expansion of CD4+ and CD8+ T cells bearing the TCR Vβ9 segment. The superantigen could be released by the parasite at different stages of its development since the deletion of Vβ9+ T cells was observed in blood and lymph nodes of mice infected either with sporozoites or with erythrocytic stages. Injection of sporozoite or parasitized erythrocytes to newborn mice led to a deletion and anergy of peripheral Vβ9+ T cells, without affecting thymic T cell populations. These observations suggest that the superantigen is released at very low concentrations during parasite development (International Immunology 1996 9 117-125 Pied et al Evidence for superantigenic activity during murine malaria infection).
Profound perturbations of the immune system are observed during the infection such as (i) hypergammaglobulinemia, with a lack of plasmodial specificity resulting from a polyclonal B cell activation, and (ii) induction of hyporesponsiveness of T cells to plasmodial and non-plasmodial antigens, and perturbation of the CD4/CD8 ratio. The cause of this phenomenon is not known, nevertheless there is evidence of a defect in both production of IL-2 and expression of IL-2 receptor by peripheral blood lymphocytes in response to stimulation with malaria-specific antigen during acute Plasmodium falciparum malaria in humans). It has been suggested that the strong polyclonal activation of all lymphocyte populations observed during malaria infection is due to a mitogen released by Plasmodium (supra).
In general, superantigens from a number of pathogens stimulate T lymphocytes through particular TCR Vβ chains. The recognition of T cells depends almost exclusively on the Vβ domain and, consequently, a superantigen can interact with a large fraction of the T cell repertoire, because the number of Vβ genes is low. In contrast to conventional antigens, superantigens bind specifically with a region of TCR located on the Vβ chain, outside of the specific site which combines with the MHC-peptide complex. When superantigens are encountered during T cell development they usually induce a clonal deletion, or an anergy, of T cells bearing the appropriate Vβ. In order to identify T cell populations and define the T cell repertoire involved in the host response to malaria infection, we have studied TCR Vβ chain usage in different cell compartments of C57BL/6 mice infected either with sporozoites or erythrocytic stages of Plasmodium. We describe here superantigenic-like activity associated with the parasite (supra).
The in vivo response to bacterial toxins usually results in preferential deletion, or anergy, in the responding CD4+ subpopulation; although some exceptions have been observed where both CD4+ and CD8+ subsets are affected. The infection with exogenous Murine Mammary Tumor Virus is dominated by deletion or anergy in the responding CD4+ lymphocytes. In the murine model of Chagas' disease, the in vivo Trypanosoma cruzi superantigenic effect was observed in the CD8 compartment. In a second parasitic system which concerns Toxoplasma gondi, the in vitro response to a superantigen is restricted to CD8+ lymphocytes. By contrast, the P. yoelii superantigenic activity affects both Vβ9+ CD4+ and CD8+ subsets. Again, by analogy with the effects obtained in the chronic exposure to low dose of SEA (staphylococcal enterotoxin A—discussed in reference) which results in the disappearance of CD4+ and CD8+ T cells bearing Vβ3, we can hypothesize that the plasmodial superantigen is expressed at low levels during the time of the infection (supra).
Aberrant immune activation induced by chronic infections with Plasmodium falciparum: leads to polyclonal B cell activation characterized by the presence of hyperglobulinemia, elevated titers of autoantibodies, and frequent occurrence of Burkitt's lymphoma and splenic lymphoma. The mechanisms that lead to this polyclonal B cell activation are poorly understood. The marked effect of malaria infection on B cells is related both to the biology of the infection, and to the nature of the malarial Ags. P. falciparum-infected erythrocytes (IE) have the potential to directly interact with B cells in different anatomical sites and to induce B cell proliferation and differentiation into Ab-secreting cells. We have shown that a large proportion (83%) of fresh isolates of IE bind nonimmune Igs, suggesting that in the peripheral blood IE could interact with B cells through their surface Igs. Moreover, blood borne antigens (and thus malarial Ags related to the erythrocytic phase) are trapped in the spleen where B cells represent about 40% of the splenocytes. Thus, IE and their constituent Ags could interact in the spleen with B cells displaying a variety of surface phenotypes, Ag-binding repertoires and signaling profiles. Among malarial Ags, the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family of proteins often display Ig binding properties. The Ig binding activity of the PfEMP1, cloned from two different P. falciparum strains, resides in two different variable domains, the Duffy binding-like domain 2β (DBL2β) and the cysteine-rich interdomain region 1α (CIDR1α). The latter domain has been identified as a polyclonal B cell activator and an Ig binding protein (IBP) with a binding pattern similar to that of another microbial IBP, the protein A of Staphylococcus aureus. Microbial IBPs are produced by protozoa, viruses, and bacteria, and play important physiological roles. During an infectious process, IBPs may act as an evasion mechanism to divert specific Ab responses. CIDR1α binds to and activates purified B lymphocytes in vitro, an interaction partially mediated through the binding to surface Ig (J Immunol. 2006 177(5) 3035-44 Donati et al Increased B cell survival and preferential activation of the memory compartment by a malaria polyclonal B cell activator).
Up-regulated genes induced by CIDR1α includes several genes previously described as mitogen-activated, involved in pathways that control cell growth/apoptosis, transcription/translation, and that are normally induced during immune responses. The up-regulation of both TRAF3 and TRAF4 suggests activation of the NF-KB pathway. The increased expression of two of the most important protein kinases, PKC and the PKA related forms (PRKAG3, PRKX), is in line with the observed CIDR1α-mediated up-regulation of genes involved in different signaling pathways; among them: the MEK/ERK pathway (EIF2B5), the MEKK/JNK pathway (TRAF3, GPS1), and the MKK/MAPK pathways (MAPK4K5, IQGAP1, IQGAP2) (supra).
Antigen presenting cells (APCs), including macrophages and dendritic cells, are early and sustained targets of Ebola virus (EBOV) infection in vivo. EBOV activates mitogen-activated protein kinase (MAPK) signaling upon infection of APCs. Pyridinyl imidazole inhibitors of p38 MAPK on EBOV infection of human APCs and EBOV mediated cytokine production from human DCs. The p38 MAPK inhibitors reduced viral replication in PMA-differentiated macrophage-like human THP-1 cells and primary human monocyte-derived dendritic cells (MDDCs) and cytokine production from EBOV-treated MDDCs was inhibited in a dose-dependent manner (Antiviral Res 2014 107 102-9 Johnson et al Pyridinyl imidazole inhibitors of p38 MAP kinase impair viral entry and reduce cytokine induction by Zaire ebolavirus in human dendritic cells). These results suggest that activation of p38 MAPK and ERK is necessary for productive EBOV infection. Since activation of macrophages/DC in the presence of immune complexes (IC) results in the activation of p38 MAPK and ERK, EBOV IC would be expected to enhance EBOV infection (supra).
Since productive EBOV infection is dependent on the activation of p38 MAPK and ERK, this suggests that Malaria can act as a cofactor accelerating EBOV replication. Evidence exists for superantigen activity in EBOV infections, the archetype B cell superantigen is Staph Protein A (SpA):
Superantigen activity has also been described for Ebola: human ZEBOV infection is associated with mRNA downregulation of three TCR Vβ subsets, indicating either anergy or deletion of the three corresponding T-lymphocyte populations. These results are consistent with ZEBOV Sag activity, the first time that it is suggested in the Filoviridae family (Baize et al Journal of Virology April 2011 p 4041 4042 Letter to the Editor: Evidence for Ebola Virus Superantigen Activity). These findings may represent the missing link in our understanding of ZEBOV pathogenicity. The SAg activity of ZEBOV might contribute to the extraordinarily rapid and profound T-lymphocyte depletion observed during fatal infection. The high viral load observed during fatal ZEBOV infection, together with the simultaneous targeting of three Vβ T-cell subsets observed here, would elicit massive lymphocyte activation, rapidly resulting in the deletion of large populations of Vβ12-, Vβ13.2-, and Vβ17-bearing T cells (supra).
Widespread activation of T and B cells in Ebola patients with acute Ebola infection suggests both T and B cell superantigen activity (McElroy et al PNAS 2015 112 15 4719-4724). Polyclonal non-specific B-cell activation was observed in patients with acute Ebola infection, which suggests the presence of a B cell superantigen which is followed by widespread apoptosis (supra).
Marburg virus (MARV) and Ebola virus (EBOV) cause severe hemorrhagic fever in primates. Earlier studies demonstrated that antibodies to particular epitopes on the glycoprotein (GP) of EBOV enhanced virus infectivity in vitro. Using MARV strains Angola and Musoke, Nakayama et al demonstrated that the infectivity of MARV-Angola in K562 cells was enhanced notably in the presence of Angola GP antisera (ie, FcR-dependent ADE), whereas Musoke GP antisera did not significantly enhance the infectivity of MARV-Angola or MARV-Musoke. This difference between the two MARV strains was also supported by the observation that immunization with Angola GP induced significantly higher numbers of B-cell clones with infectivity-enhancing properties than did immunization with Musoke GP. These results may suggest that the potential difference in the pathogenicity between the MARV strains Angola and Musoke might be partially explained by the ability to induce infectivity-enhancing antibodies, as was proposed for the distinct pathogenicity seen with ZEBOV and Reston EBOV (Nakayama et al J Infect Dis. 2011 Nov. 1 204(Suppl 3) S978-S985). This observation suggests that the difference in the pathogenicity of ZEBOV and REBOV appears to be related to the B cell superantigen activity of ZEBOV verses REBOV and further suggests that ADE is of clinical importance in Ebola infections. Both B cell superantigen and pathogen immunoglobulin binding factors appear to play a role in the pathogenicity and that blocking the immunoglobulin binding factors appears to abrogate the increased pathogenicity associated with ADE.
The invention will be further described in the following examples, which do not limit the scope of the invention described in the claims.
The clinical burden for serious Malaria in the countries of Liberia, Sierra Leone, and Guinea is shown in
The observed geographic correlation of serious Malaria cases and the Ebola outbreak is consistent with the proposition that coinfection with other serious pathogenic agents may function as a cofactor for Ebola. West Africa, the site of the unprecedented 2014 Ebola outbreak, represents a region having one of the highest numbers of serious Malaria cases (Hay et al., PLOS Med., 2010, 7(6):e1000290). Also consistent with the coinfection cofactor proposition are the observations that some Ebola infections are asymptomatic (Becquart et al., PLOS One, 2010, 5(2):e9126), and that Ebola outbreaks have not occurred in other parts of the world, especially in the West where the incidence of co-infection other pathogenic agents is substantially lower.
The disruption of health services in the three Ebola outbreak affected countries has been shown to contribute to a higher number of malaria deaths in those countries (Walker et al., Lancet Infectious Dis., 2015, Epub Apr. 24, 2015 “Malaria morbidity and mortality in Ebola-affected countries caused by decreased health-care capacity, and the potential effect of mitigation strategies: a modelling analysis”). In addition, a seasonal or temporal relationship was found to exist between malaria deaths and Ebola cases in Guinea, Sierra Leone and Liberia.
The seasonal/temporal relationship reinforces the geographic relationship between serious malaria/malaria deaths and Ebola cases.
Reston Ebola virus (Reston ebolavirus; RESTV or REBOV), has been reported to cause disease in nonhuman primates and pigs, but not in humans. REBOV has been found to exist in domestic swine co-infected with porcine reproductive and respiratory syndrome virus (PRRSV). (Barrette et al., Science, 2009, 325(5937):204-206; Pan et al., Arch Virol., 2014, 159(5):1129-1132.) The observed incidence of PRRSV coinfection in REBOV-infected pig populations is likewise consistent with a proposed disease mechanism wherein REBOV replication is enhanced by coinfection, for example by immune complex (IC) formation induced by a non-related virus, PRRSV.
In vitro assays involving enzyme-linked immunosorbent assay (ELISA) can be used to demonstrate competitive inhibition of immune complexed IgG Fc binding to immune mediating factors such as Fc receptors (FcRs), (e.g., FcγRI, FcγIIa, FcγRIIb/c, FcγRIIIa/b), FcRn, mC1q, and sC1q by the polypeptides and compounds described herein. See, e.g., the examples described herein, as well as U.S. Patent Publication Nos. 20070225231 and 20070276125, and PCT Publication No. WO2007/030475. Standardized reagents and ELISA kits are useful to reduce costs and increase the reproducibility of the experiments.
Because SEQ ID NO:20 is a classic noncompetitive allosteric inhibitor designed to bind to the Fc region of IgG immune complexes (IC) and prevents IgG-IC from binding to Fc receptors (FcRs), we were able to develop an enzyme-linked immunosorbent assay (ELISA) to measure the bioactivity of SEQ ID NO:20. In a standard ELISA, an antigen is immunoadsorbed onto a plastic microwell. After suitable blocking and washing steps, a primary antibody with specificity directed toward the antigen is added to the microwell. After another wash phase, a secondary antibody that is directed toward the primary antibody and conjugated to an enzyme marker, such as horseradish peroxidase (HRP), is added to the microwell. Following another wash cycle, the appropriate enzyme substrate, such as 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) in the case of HRP, is added. If an antigen to primary antibody to secondary antibody/HRP conjugate is formed, the conjugated enzyme catalyzes a colorimetric chemical reaction with the substrate, which is read with a microplate reader or spectrophotometer. By standardizing the levels of the antigen and secondary antibody/HRP conjugate, a titer of the primary antibody (the variable) is established. In a standard ELISA, the primary antibody binds to the antigen through its complementarily determining regions (CDR) located on the Fab arms. Because HRP is conjugated to the Fc region of the secondary antibody, direct Fc binding is very limited or abrogated.
A “reverse” ELISA technique is used to assess binding of the Fc receptor ligands that bind to IgG-IC. In the reverse ELISA, the enzyme (e.g., HRP) is not covalently conjugated to the Fc portion of the secondary antibody. Rather, a preformed immune complex of peroxidase-rabbit anti-peroxidase IgG (“PAP” complex) is used. SEQ ID NO:20 was designed to bind to human IgG-IC and since rabbit IgG is virtually identical to human IgG at the binding site for SEQ ID NO:20, rabbit IgG-IC can be used as a substitute for human IgG-IC, which are not commercially available. In this method, HRP serves both as the antigen and the enzyme marker but does not block the Fc region. In the reverse ELISA system, a Fc CH2-CH3 cleft binding ligand or FcR (e.g., human FcRIIa or C1q) is bound to microwell plates. In the absence of competitor, PAP IC complexes bind to the immobilized ligand and the reaction between HRP and its substrate produces a signal (“negative control”). This signal is reduced by the pre-incubation of inhibitors (e.g., FcRIIa, C1q or rheumatoid factor) or peptides such as SEQ ID NO:20 that inhibits PAP IC from binding to the immobilized FcR ligand. In a “reverse” inhibitive ELISA, less color development is indicative of greater inhibition. See, e.g., U.S. Pat. Nos. 6,916,904, 7,714,104, 8,362,202 and 8,815,813.
All steps are performed at room temperature unless noted otherwise.
Preparing the FcR Coated Microwell Plates.
100 uL of a 0.05 ug/uL solution of human FcRIIA (rhFcRIIa) or C1q is used to coat each well that is to be used of a standard microwell plate that has 96 0.32 cm2 wells. The rhFcRIIa is prepared by mixing 0.1 mL of 100 ug/200 uL rhFcRIIa, Santa Cruz Biotechnology, catalogue number sc-174810, or R&D Systems, catalogue number 1330-CD-050/CF, with 0.1 mL of 10× ELISA Plate Coating Buffer, AlphaDiagnostic International, catalogue number 80050, and 0.8 mL of 1×PBS. After allowing the microwell plate to incubate long enough to allow the rhFcRIIa to be immunoadsorbed onto the wells of the microwell plate (≧12 hours @ 4° C.), the rhFcRIIa solution is manually removed from the microwells. The plates are blocked from any further non-specific protein adsorption by adding 100 uL of 1 mg/mL bovine serum albumin (BSA), Cohn fraction V, Sigma-Aldrich, catalogue number A5611, to each of the wells. The 1 mg/mL BSA solution is prepared by dissolving the BSA in 1×PBS and then filter sterilizing. After allowing the plate to incubate for 1 hour @ 4° C., the BSA solution is manually removed and each well is washed four more times with 100 uL of the 1 mg/mL BSA solution with no additional time between washes. One final wash with 100 uL of 1×PBS is then done to remove any residual BSA. If the plate is sealed it can be used for up to several days later.
Forming the PAP Immune Complex (IC).
10 mg of HRP, Sigma-Aldrich, catalogue number P6782, is dissolved in 2 mL of 1×PBS. Lyophilized rabbit anti-peroxidase antibody, Sigma-Aldrich, catalogue number P7899, is dissolved in 2.1 mL of ice cold 1×PBS and filtered using a 0.22 μm pore size 13 mm PVDF syringe filter and a 3 mL sterile syringe. The resuspended rabbit anti-peroxidase antibody is stored at 4° C. The rabbit antibody must be handed using sterile techniques to avoid bacterial contamination since the Sigma P7899 antibody does not contain a preservative agent. The resuspended antibody can be used up to one year as long as no contamination occurs as judged by an increase in turbidity. To form the PAP complex, 20 uL of the resuspended rabbit anti-peroxidase antibody is added to 950 μl of 1×PBS, followed by the addition of 50 μl of the 5 mg/mL HRP solution. The PAP complex must be used immediately. It cannot be stored, because even with antigen excess, larger immune complexes will be formed upon storage. The extreme antigen excess guarantees that any single antibody is bound to two HRP molecules and prevents larger immune complexes from forming, thus eliminating the bridging of larger immune complexes. Potential inhibitors are dissolved in 1×PBS and 100 uL of the inhibitor to be tested is then added to 100 uL of the PAP complex and allowed to incubate for 1 hour. For a control, 100 uL of 1×PBS is added to 100 uL of the PAP complex instead of the inhibitor.
Performing the Reaction.
100 uL of each inhibitor/PAP complex mixture is added to a well of the coated microwell plate as well as the control PAP complex without the added inhibitor. After allowing the plate to incubate for 1 hour, the inhibitor/PAP complex mixture is manually removed and each well is washed four more times with 100 uL of 1×PBS with no additional time between washes. 100 uL of SUB4 ABTS 1-Component HRP Microwell Substrate, ImmunoChemistry Technologies, catalogue number 6278, is added to each well and after 30 minutes of incubation, 100 uL of Stop Solution for ABTS Microwell Substrate STOP2, ImmunoChemistry Technologies, catalogue number 6283, is added to each well and the color development is read at OD 405 nm on a microwell ELISA reader or spectrophotometer.
B. Inhibition of C1q Binding to PAP Immune Complex (see U.S. Pat. No. 8,815,813)
Exemplary materials and methods are described in more detail above. Briefly, C1q was immobilized on the microwell plates. PAP immune complexes were formed by mixing 2 μl of rabbit anti-peroxidase (Sigma Chemicals Product P 7899) with 50 μl of peroxidase (Sigma-Aldrich P6782) in 1 ml distilled water. PAP (100 μl) were pre-incubated with 100 μl of human C1q (Quidel Corp.) or 100 μl of peptide (see Table 1) for one hour. Like FcR, C1q is known to bind to the Fc region on IgG. The ability of PAP immune complexes to bind to the immobilized C1q in the presence or absence of inhibitors was determined. The C1q/PAP mixture served as a positive control; PAP immune complexes bind to soluble C1q, and the premixed C1q/PAP immune complexes are therefore not expected to bind to the C1q-containing plate, resulting in low signal levels, similar to what would be observed in the presence of an inhibitor. The PAP immune complex alone serves as the negative control; in the absence of inhibitors, the PAP immune complex is expected to bind to the C1q-containing plate, resulting in high signal levels.
C1q/PAP mixture, peptide/PAP mixtures, and PAP alone were incubated with C1q coated plates for 30 minutes. After washing, plates were incubated with ATBS (Quidel Corp.) for 15 minutes and read at 405 nm. Results are shown in Table 1.
APPDCAWHLGELVWCT
APPDCAWHLGELVWCT (SEQ ID NO:20) resulted in the greatest inhibition of C1q binding, almost equaling C1q itself. Peptide APPCARHLGELVWCT (SEQ ID NO:16) gave the next best result.
Once the reverse ELISA protocol was established using the C1q assay, the assay was redesigned using FcγIIa, FcγIIb and FcγIII in place of C1q. Highly purified FcγIIa, FcγIIb and FcγIII (R&D Systems, Minneapolis, Minn.) were immunoadsorbed onto plastic microwells. After optimizing the FcγR reverse ELISA system, simple competitive inhibition experiments using polypeptides provided herein were conducted to investigate their ability to inhibit binding of immune complexes to purified FcγR.
Exemplary materials and methods are described in more detail above. Briefly, Falcon microtiter plates were coated with 1:10 dilutions of highly purified FcγIIa, FcγIIb and FcγIII and incubated for 24 hours. The plates were washed and then blocked with 5.times.BSA blocking solution (Alpha Diagnostic International, San Antonio, Tex.) for 24 hours. PAP immune complexes were formed by mixing 2 μl of rabbit anti-peroxidase (Sigma Chemicals Product P 7899) with 50 μl of peroxidase (Sigma-Aldrich P6782) in 1 ml distilled water. PAP (100 μl) were pre-incubated with 100 l of peptide for one hour. PAP/peptide mixtures were added to the FcγR coated plates and incubated for one hour. After washing, plates were incubated with ABTS substrate (Quidel Corp.) for 15 minutes and read at 405 nm. Results are shown in Table 2.
Peptide APPDCAWHLGELVWCT (SEQ ID NO:20) appeared to result in the greatest overall inhibition of FcR binding to PAP, followed by peptide DCAWHLGELVWCT (SEQ ID NO:2). Experiments with SEQ ID NO:20 were repeated. Costar microtiter plates were coated with 1:10 dilutions of highly purified FcγIIa (H is 131 allele aka H161), FcγIIb and FcγIIIb and incubated for 24 hours. The plates were washed and then blocked with 10 mg/ml BSA blocking solution for 24 hours. PAP immune complexes were formed as described in Example 2. PAP (100 μl) were pre-incubated with 100 μl of peptide for one hour. PAP/peptide mixtures were added to the FcγR coated plates and incubated for one hour. After washing, plates were incubated with ABTS substrate for 15 minutes and read at 405 nm. Results are shown in Table 3.
Thus, SEQ ID NO:20 inhibited binding of all three major classes of Fc receptor (FcγI, FcγIIa/FcγIIb, and FcγIII) to soluble PAP immune complexes.
Demonstration that Ebolavirus Contains a Viral FcR and that NB406 (SEQ ID NO:20) can Prevent the Binding of IC to Ebolavirus
To test whether the Ebolavirus contained an FcR and whether SEQ ID NO:20 could inhibit the binding of IC to the FcR of the Ebolavirus, we used the reverse ELISA assay. Instead of binding a known FcR to the plate, such as human FcRIIa, or C1q, Sudan Ebolavirus, Boniface, was used, which was obtained from Bei Resources, Number NR-31810. 100 uL of a 1:100 dilution from 100 uL of sonicated Vero E6 cell pellets that had been infected with Sudan Ebolavirus, Boniface, frozen and then gamma-irradiated were used to coat each well of the microplate. The standard reverse ELISA protocol was implemented with the inhibitor SEQ ID NO:20 used at a concentration of 10 mg/mL, 3 mg/mL, and 1 mg/mL; OD was read at 405 nm.
Sudan Ebolavirus (SEBOV) was tested at several concentrations and either 1:100, 1:1,000 or 1:10,000 dilutions of the stock virus was used in the standard reverse ELISA.
The results demonstrate that Ebolavirus contains a viral FcR that can bind IC and that SEQ ID NO:20 can effectively prevent the binding of IC to the Ebola virus.
Demonstration that Ebolavirus Glycoprotein is a Viral FcR and that NB406 (SEQ ID NO:20) can Prevent the Binding of IC to Ebolavirus Glycoprotein
Once it was established that whole Ebolavirus can bind an IC and thus acts as a viral Fc receptor (FcR), it was of interest to determine which protein constituent of Ebolavirus contains the viral FcR binding activity. Ebolavirus glycoprotein (GP) was investigated as a candidate viral FcR. The reverse ELISA assay was used to test whether the Ebolavirus glycoprotein was the viral FcR and whether SEQ ID NO:20 could inhibit the binding of IC to the glycoprotein viral FcR of the Ebolavirus. Instead of binding a known FcR to the plate, such as human FcRIIa, C1q, or whole Ebolavirus, as in the preceding section, recombinant Sudan Ebolavirus glycoprotein from IBT Bioservices, Catologue Number 0501-015, was used. 100 uL of a 10 ug/mL solution of Sudan Ebolavirus glycoprotein was used to coat each well of the microplate. The standard reverse ELISA protocol was implemented with the inhibitor SEQ ID NO:20 used at a concentration of 10 mg/mL, 3 mg/mL, and 1 mg/mL; OD was read at 405 nm.
Sudan Ebolavirus Glycoprotein (GP) was tested at several concentrations and either 10 ug/mL, 3 ug/mL or 1 ug/mL concentrations were used in the standard reverse ELISA.
The results demonstrate that Ebolavirus glycoprotein (GP) is a viral FcR that can bind IC and that SEQ ID NO:20 can effectively prevent the binding of IC to the Ebolavirus glycoprotein.
In this experiment, Ebolavirus (Sudan) immune complexes are evaluated for binding to immobilized recombinant human FcγRIIa.
Highly purified recombinant human FcγRIIa (R&D Systems, 1 μg/ml) are immunoadsorbed onto plastic microwells (Costar Microtiter plates) using ELISA coating buffer (Alpha Diagnostic International) for 24 hours at 4° C. After 24 hours, the plates were washed 5 times with ELISA wash solution (Quidel Corp.), blocked with highly purified BSA for 1 hour, and washed 5 times. Rabbit anti-SEBOV IC are formed by combining whole inactivated Sudan Ebola virus (SEBOV-Sudan Ebolavirus, Boniface, Gamma-Irradiated—SEBOV BEI RESOURCES) with IBT Bioservices 0302-020 Rabbit Polyclonal anti-Sudan GP. Rabbit anti-SEBOV GP IC (100 μl) is pre-incubated with and without of SEQ ID NO:20 (100 μl) for one hour. Next, either rabbit-anti-SEBOV IgG IC (100 μl) or rabbit-anti-SEBOV IgG-NB406 (100 μl) is added to the FcγRIIa coated plates. After one half hour incubation, the plates are washed five times. After one hour, the plates are washed and 100 μl of 1:1,000 dilution of Pierce Mouse anti-Rabbit IgG (H+L) Cross Adsorbed Secondary Antibody, HRP conjugate Cat #31464 is added to the microwells and incubated for one hour. 100 μl of ABTS are added to each micro-well, after ½ hour incubation, the plates are read at 405 nm.
As shown in
As shown in
U937 or K562 Monocyte cell types expressing both FcγRIIa and FcγRIIb are infected with vesicular stomatitis virus pseudotyped with EBOV GP in the manner described by Takada et al 2007 (J Infect Dis 2007 196 S2 S347). Diluted convalescent Ebola sera are added to produce antibody dependent enhancement (ADE) of infection of the U937 or K562 cells.
Monoclonal antibodies to FcγRIIb (SuppreMol SM201 or Xencor XmAb5871) are added to the VSV-EBOV GP/immune complex/cell cultures, and ligation of FcγRIIb is expected to result in an inhibition of ADE in cell culture.
A major difference in antibody dependent enhancement (ADE) of filoviruses (Ebola and Marburg) and flaviviruses (dengue and West Nile Virus (WNV)) is that both C1q and FcγR cause or exacerbate ADE in filoviruses (Takada et al., J. Infect. Dis. 2007, 196(S2):S347-56; Nakayama et al., J. Infect. Dis., 2011, 204(S3):S978-85), whereas C1q decreases or inhibits ADE in dengue and WNV infections (Mehlhop et al., Cell Host Microbe, 2007, 2(6):417-26). Complement protein C1q inhibits antibody-dependent enhancement of flavivirus infection in an IgG subclass-specific manner (Mehlhop et al., Cell HostMicrobe, 2009, 6(4):381-91). There are both stoichiometric and conformational reasons for this difference. For example, Ebola GP consists of three GP1/GP2 molecules forming a trimer. The trimer forms a “chalice” (
C1q binds IgG hexamers (Diebolder et al., Science, 2014, 343(6176): 1260-3). The IgG hexamers form a ring structure that allows high affinity binding by C1q (
The hexametric C1q binds to these IgG hexamers. The mechanism of action for SEQ ID NO:20 (NB406) inhibition of C1q to IC binding does not appear to be due to allosteric inhibition, but rather disruption of the IgG Fc-Fc interactions required to form the IgG hexamer. In examining the structure of Ebola GP, we surmised that two Ebola GP trimers could be mimicking C1q and the mechanism of action for inhibiting Ebola GP binding to IgG IC may be due to disruption of Fc-Fc interactions.
In this model, SEQ ID NO:20 (NB406) inhibits Ebola GP to IgG (hexamer) binding by disrupting the Fc-Fc interactions required to form the IgG hexamer. The idea that Ebola GP is mimicking C1q is consistent with the experimental data disclosed herein, but is completely unexpected.
This Example describes evaluation of whether the influenza virus could bind to an immune complex (IC) and whether NB406 (SEQ ID NO:20) could prevent this binding from occurring. While most researchers argue that the greater susceptibility of patients with autoimmune diseases to influenza infections is due to their compromised health, we believe that the influenza virus uses immune complexes as a mechanism to hijack the immune system and proliferate more rapidly. For this reason we wanted to determine whether the influenza virus contained Fc receptors (FcRs) that would bind to ICs and whether the NB406 peptide (SEQ ID NO:20) could prevent this binding from occurring and thus act a potential therapeutic agent to prevent the proliferation of influenza infections.
A. Detecting and Quantifying the Binding of ICs to FcRs and Inhibitors that can Prevent this Binding from Occurring.
ICs are key to the immune response and occur when an IgG binds to an antigen. ICs are prevalent in any disease or condition that stimulates an immune response, including autoimmune diseases. The ICs that are formed then bind to FcRs or C1q, which causes the immune response to progress. A multitude of approaches and methods have been developed to detect and quantify ICs, since they are a hallmark of a variety of diseases. We have developed a simple but robust reverse ELISA method for quantifying the ability of potential inhibitor compounds to prevent the binding of ICs to FcRs and to determine whether an entity, such as a virus or cell, contains any FcRs. In this method horseradish peroxidase (HRP) and anti-HRP IgG antibody is mixed to form an IC, which is then bound to an FcR, such as human FcRIIa or C1q, or a cell or virus that is suspected to contain a FcR. The reverse ELISA was originally described in U.S. Pat. No. 6,916,904 and implemented in U.S. Pat. No. 6,916,904. The experiments described here were performed using the protocols described in U.S. Pat. Nos. 6,916,904 and 7,714,104, with an expanded explanation of the principles and protocols used in the bioassay.
In a standard ELISA, an antigen is immunoadsorbed onto a plastic microwell. After suitable blocking and washing steps, a primary antibody with specificity directed toward the antigen is added to the microwell. After another wash phase, a secondary antibody that is directed toward the primary antibody and conjugated to an enzyme marker, such as horseradish peroxidase (HRP), is added to the microwell. Following another wash cycle, the appropriate enzyme substrate, such as 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) in the case of HRP, is added. If an antigen to primary antibody to secondary antibody/HRP conjugate is formed, the conjugated enzyme catalyzes a colorimetric chemical reaction with the substrate, which is read with a microplate reader or spectrophotometer. By standardizing the levels of the antigen and secondary antibody/HRP conjugate, a titer of the primary antibody (the variable) is established. In a standard ELISA, the primary antibody binds to the antigen through its complementarily determining regions (CDR) located on the Fab arms. Because HRP is conjugated to the Fc region of the secondary antibody, direct Fc binding is very limited or abrogated.
In our reverse ELISA technique, the enzyme (e.g., HRP) is not covalently conjugated to the Fc portion of the secondary antibody. Rather, a preformed immune complex of peroxidase-rabbit anti-peroxidase IgG (“PAP” complex) is used. In this method, HRP serves both as the antigen and the enzyme marker but does not block the Fc region. In the reverse ELISA system, a Fc CH2-CH3 cleft binding ligand or FcR (e.g., human FcRIIa or C1q) is bound to microwell plates. In the absence of a competitor, PAP IC complexes bind to the immobilized ligand and the reaction between HRP and its substrate produces a signal (“Positive Control”). This signal is reduced by the pre-incubation of inhibitors (e.g., FcRIIa, C1q, rheumatoid factor or peptides, such as SEQ ID NO:20) that prevent PAP IC from binding to the immobilized FcR ligand. In our reverse ELISA, less color development is indicative of greater inhibition.
NB406 (SEQ ID NO:20) is a classic noncompetitive allosteric inhibitor designed to bind to the Fc region of human IgG IC and prevent IgG-IC from binding to FcRs (U.S. Pat. No. 6,916,904 and U.S. Pat. No. 6,916,904). Because NB406 (SEQ ID NO:20) was designed to bind to human IgG-IC and since rabbit IgG is virtually identical to human IgG at the NB406 binding site, rabbit IgG-IC can be used as a substitute for human IgG-IC, which are not commercially available, in either in vitro or in vivo testing.
100 uL of a 0.05 ug/uL solution of human FcRIIA (rhFcRIIa) or C1q is used to coat each well that is to be used of a standard microwell plate that has 96 0.32 cm2 wells. The rhFcRIIa is prepared by mixing 0.1 mL of 100 ug/200 uL rhFcRIIa, Santa Cruz Biotechnology, catalogue number sc-174810, with 0.1 mL of 10× ELISA Plate Coating Buffer, AlphaDiagnostic International, catalogue number 80050, and 0.8 mL of 1×PBS. After allowing the microwell plate to incubate long enough to allow the rhFcRIIa to be immunoadsorbed onto the wells of the microwell plate (>12 hours @ 4° C.), the rhFcRIIa solution is manually removed from the microwells. The plates are blocked from any further non-specific protein adsorption by adding 100 uL of 1 mg/mL bovine serum albumin (BSA), Cohn fraction V, Sigma-Aldrich, catalogue number A5611, to each of the wells. The 1 mg/mL BSA solution is prepared by dissolving the BSA in 1×PBS and then filter sterilizing. After allowing the plate to incubate for 1 hour @ 4° C., the BSA solution is manually removed and each well is washed four more times with 100 uL of the 1 mg/mL BSA solution with no additional time between washes. One final wash with 100 uL of 1×PBS is then done to remove any residual BSA. If the plate is sealed it can be used for up to several days later.
10 mg of HRP, Sigma-Aldrich, catalogue number P6782, is dissolved in 2 mL of 1×PBS. Lyophilized rabbit anti-peroxidase antibody, Sigma-Aldrich, catalogue number P7899, is dissolved in 2.1 mL of ice cold 1×PBS and filtered using a 0.22 μm pore size 13 mm PVDF syringe filter and a 3 mL sterile syringe. The resuspended rabbit anti-peroxidase antibody is stored at 4° C. The rabbit antibody must be handed using sterile techniques to avoid bacterial contamination since the Sigma P7899 antibody does not contain a preservative agent. The resuspended antibody can be used up to one year as long as no contamination occurs as judged by an increase in turbidity. To form the PAP complex, 20 uL of the resuspended rabbit anti-peroxidase antibody is added to 950 μl of 1×PBS, followed by the addition of 50 μl of the 5 mg/mL HRP solution. The PAP complex must be used immediately. It cannot be stored, because even with antigen excess, larger immune complexes will be formed upon storage. The extreme antigen excess guarantees that any single antibody is bound to two HRP molecules and prevents larger immune complexes from forming, thus eliminating the bridging of larger immune complexes. Potential inhibitors are dissolved in 1×PBS and 100 uL of the inhibitor to be tested is then added to 100 uL of the PAP complex and allowed to incubate for 1 hour. For a control, 100 uL of 1×PBS is added to 100 uL of the PAP complex instead of the inhibitor.
100 uL of each inhibitor/PAP complex mixture is added to a well of the coated microwell plate as well as the control PAP complex without the added inhibitor. After allowing the plate to incubate for 1 hour, the inhibitor/PAP complex mixture is manually removed and each well is washed four more times with 100 uL of 1×PBS with no additional time between washes. 100 uL of SUB4 ABTS 1-Component HRP Microwell Substrate, ImmunoChemistry Technologies, catalogue number 6278, is added to each well and after 30 minutes of incubation, 100 uL of Stop Solution for ABTS Microwell Substrate STOP2, ImmunoChemistry Technologies, catalogue number 6283, is added to each well and the color development is read at OD 405 nm on a microwell ELISA reader or spectrophotometer.
C. Demonstration that Influenza Virus Contains a FcR and that NB406 (SEQ ID NO:20) can Prevent the Binding of IC to Influenza Virus
To test whether the influenza virus contained a FcR and whether NB406 (SEQ ID NO:20) could inhibit the binding of IC to the FcR of influenza virus, we used the reverse ELISA assay. Instead of binding a known FcR to the plate, such as human FcRIIa or C1q, influenza virus, was used. 100 uL of a 1:10 or 1:100 dilution of Influenza A/MAL/NY/6750/78 H2N2 virus at a titer of 1.2×106 used to coat each well of the microplate. The standard reverse ELISA protocol was implemented with the inhibitor NB406 used at a concentration of 10, 3.33 or 1.11 mg/mL. The assay was repeated three times and a typical result is shown in Table 4. Influenza A virus is abbreviated as IAV in Table 4.
The results demonstrate that influenza virus contains a FcR that can bind IC and that NB406 can effectively prevent the binding of IC to the influenza virus.
This Example describes evaluation of whether the hepatitis virus could bind to an immune complex (IC) and whether NB406 (SEQ ID NO:20) could prevent this binding from occurring. While most researchers argue that the greater susceptibility of patients with autoimmune diseases to hepatitis viral infections is due to their compromised health, we believe that the hepatitis virus uses immune complexes as a mechanism to bridge the immune system and proliferate more rapidly. For this reason we wanted to determine whether the hepatitis A and C viruses contained Fc receptors (FcRs) that would bind to ICs and whether the NB406 peptide could prevent this binding from occurring and thus act a potential therapeutic agent to prevent the proliferation of hepatitis infections.
A. Detecting and Quantifying the Binding of ICs to FcRs and Inhibitors that can Prevent this binding from occurring.
ICs are key to the immune response and occur when an IgG binds to an antigen. ICs are prevalent in any disease or condition that stimulates an immune response, including autoimmune diseases. The ICs that are formed then bind to FcRs or C1q, which causes the immune response to progress. A multitude of approaches and methods have been developed to detect and quantify ICs, since they are a hallmark of a variety of diseases. We have developed a simple but robust reverse ELISA method for quantifying the ability of potential inhibitor compounds to prevent the binding of ICs to FcRs and to determine whether an entity, such as a virus or cell, contains any FcRs. In this method horseradish peroxidase (HRP) and anti-HRP IgG antibody is mixed to form an IC, which is then bound to an FcR, such as human FcRIIa or C1q, or a cell or virus that is suspected to contain a FcR. The reverse ELISA was originally described in U.S. Pat. No. 6,916,904 and implemented in U.S. Pat. No. 6,916,904. The experiments described here were performed using the protocols described in U.S. Pat. Nos. 6,916,904 and 7,714,104, with an expanded explanation of the principles and protocols used in the bioassay.
In a standard ELISA, an antigen is immunoadsorbed onto a plastic microwell. After suitable blocking and washing steps, a primary antibody with specificity directed toward the antigen is added to the microwell. After another wash phase, a secondary antibody that is directed toward the primary antibody and conjugated to an enzyme marker, such as horseradish peroxidase (HRP), is added to the microwell. Following another wash cycle, the appropriate enzyme substrate, such as 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) in the case of HRP, is added. If an antigen to primary antibody to secondary antibody/HRP conjugate is formed, the conjugated enzyme catalyzes a colorimetric chemical reaction with the substrate, which is read with a microplate reader or spectrophotometer. By standardizing the levels of the antigen and secondary antibody/HRP conjugate, a titer of the primary antibody (the variable) is established. In a standard ELISA, the primary antibody binds to the antigen through its complementarily determining regions (CDR) located on the Fab arms. Because HRP is conjugated to the Fc region of the secondary antibody, direct Fc binding is very limited or abrogated.
In our reverse ELISA technique, the enzyme (e.g., HRP) is not covalently conjugated to the Fc portion of the secondary antibody. Rather, a preformed immune complex of peroxidase-rabbit anti-peroxidase IgG (“PAP” complex) is used. In this method, HRP serves both as the antigen and the enzyme marker but does not block the Fc region. In the reverse ELISA system, a Fc CH2-CH3 cleft binding ligand or FcR (e.g., human FcRIIa or C1q) is bound to microwell plates. In the absence of a competitor, PAP IC complexes bind to the immobilized ligand and the reaction between HRP and its substrate produces a signal (“Positive Control”). This signal is reduced by the pre-incubation of inhibitors (e.g., FcRIIa, C1q, rheumatoid factor or peptides, such as SEQ ID NO:20) that prevent PAP IC from binding to the immobilized FcR ligand. In our reverse ELISA, less color development is indicative of greater inhibition.
NB406 (SEQ ID NO:20) is a classic noncompetitive allosteric inhibitor designed to bind to the Fc region of human IgG IC and prevent IgG-IC from binding to FcRs (U.S. Pat. No. 6,916,904 and U.S. Pat. No. 6,916,904). Because NB406 (SEQ ID NO:20) was designed to bind to human IgG-IC and since rabbit IgG is virtually identical to human IgG at the NB406 binding site, rabbit IgG-IC can be used as a substitute for human IgG-IC, which are not commercially available, in either in vitro or in vivo testing.
100 uL of a 0.05 ug/uL solution of human FcRIIA (rhFcRIIa) or C q is used to coat each well that is to be used of a standard microwell plate that has 96 0.32 cm2 wells. The rhFcRIIa is prepared by mixing 0.1 mL of 100 ug/200 uL rhFcRIIa, Santa Cruz Biotechnology, catalogue number sc-174810, with 0.1 mL of 10× ELISA Plate Coating Buffer, AlphaDiagnostic International, catalogue number 80050, and 0.8 mL of 1×PBS. After allowing the microwell plate to incubate long enough to allow the rhFcRIIa to be immunoadsorbed onto the wells of the microwell plate (>12 hours @ 4° C.), the rhFcRIIa solution is manually removed from the microwells. The plates are blocked from any further non-specific protein adsorption by adding 100 uL of 1 mg/mL bovine serum albumin (BSA), Cohn fraction V, Sigma-Aldrich, catalogue number A5611, to each of the wells. The 1 mg/mL BSA solution is prepared by dissolving the BSA in 1×PBS and then filter sterilizing. After allowing the plate to incubate for 1 hour @ 4° C., the BSA solution is manually removed and each well is washed four more times with 100 uL of the 1 mg/mL BSA solution with no additional time between washes. One final wash with 100 uL of 1×PBS is then done to remove any residual BSA. If the plate is sealed it can be used for up to several days later.
10 mg of HRP, Sigma-Aldrich, catalogue number P6782, is dissolved in 2 mL of 1×PBS. Lyophilized rabbit anti-peroxidase antibody, Sigma-Aldrich, catalogue number P7899, is dissolved in 2.1 mL of ice cold 1×PBS and filtered using a 0.22 μm pore size 13 mm PVDF syringe filter and a 3 mL sterile syringe. The resuspended rabbit anti-peroxidase antibody is stored at 4° C. The rabbit antibody must be handed using sterile techniques to avoid bacterial contamination since the Sigma P7899 antibody does not contain a preservative agent. The resuspended antibody can be used up to one year as long as no contamination occurs as judged by an increase in turbidity. To form the PAP complex, 20 uL of the resuspended rabbit anti-peroxidase antibody is added to 950 μl of 1×PBS, followed by the addition of 50 μl of the 5 mg/mL HRP solution. The PAP complex must be used immediately. It cannot be stored, because even with antigen excess, larger immune complexes will be formed upon storage. The extreme antigen excess guarantees that any single antibody is bound to two HRP molecules and prevents larger immune complexes from forming, thus eliminating the bridging of larger immune complexes. Potential inhibitors are dissolved in 1×PBS and 100 uL of the inhibitor to be tested is then added to 100 uL of the PAP complex and allowed to incubate for 1 hour. For a control, 100 uL of 1×PBS is added to 100 uL of the PAP complex instead of the inhibitor.
100 uL of each inhibitor/PAP complex mixture is added to a well of the coated microwell plate as well as the control PAP complex without the added inhibitor. After allowing the plate to incubate for 1 hour, the inhibitor/PAP complex mixture is manually removed and each well is washed four more times with 100 uL of 1×PBS with no additional time between washes. 100 uL of SUB4 ABTS 1-Component HRP Microwell Substrate, ImmunoChemistry Technologies, catalogue number 6278, is added to each well and after 30 minutes of incubation, 100 uL of Stop Solution for ABTS Microwell Substrate STOP2, ImmunoChemistry Technologies, catalogue number 6283, is added to each well and the color development is read at OD 405 nm on a microwell ELISA reader or spectrophotometer.
C. Demonstration that Hepatitis a Virus Contains a FcR and that NB406 (SEQ ID NO:20) can Prevent the Binding of IC to the Hepatitis a Virus
To test whether the hepatitis A virus contained a FcR and whether NB406 (SEQ ID NO:20) could inhibit the binding of IC to the FcR of the hepatitis A virus, we used the reverse ELISA assay. Instead of binding a known FcR to the plate, such as human FcRIIa or C1q, hepatitis A virus was used. 100 uL of a 1:10 or 1:100 dilution of hepatitis A virus at a titer of 1.5×106 used to coat each well of the microplate. The standard reverse ELISA protocol was implemented with the inhibitor NB406 used at a concentration of 10, 3.33 or 1.11 mg/mL. The assay was repeated three times and the average of the three replicate experiments is shown in Table 5. Hepatitis A virus is abbreviated as HAV in the table.
The results demonstrate that the hepatitis A virus contains a FcR that can bind IC and that NB406 can effectively prevent the binding of IC to the hepatitis A virus.
D. Demonstration that Hepatitis C Virus Core Protein is an FcR and that NB406 (SEQ ID NO:20) can Prevent the Binding of IC to Hepatitis C Virus Core Protein
We also tested whether the hepatitis C virus core protein was a FcR using the reverse ELISA assay. Instead of binding a known FcR to the plate, the hepatitis C virus core protein was used. The standard reverse ELISA protocol was implemented with the inhibitor NB406 used at a concentration of 10 mg/mL. The assay was repeated three times and the average of the three replicate experiments is shown in Table 6. Hepatitis C virus is abbreviated as HCV in the table.
It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.
All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
The complete disclosures of all patents, patent applications including provisional patent applications, publications including patent publications and nonpatent publications, and electronically available material (including, for example, nucleotide sequence submissions in, e.g., GenBank and RefSeq, and amino acid sequence submissions in, e.g., SwissProt, PIR, PRF, PDB, and translations from annotated coding regions in GenBank and RefSeq) cited herein are incorporated by reference. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for variations obvious to one skilled in the art will be included within the invention defined by the claims.
Munakata et al., Human parvovirus B19 infection of monocytic cell line U937 and antibody-dependent enhancement Virology, 2006; 345(1):251-7.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/124,485, filed Dec. 22, 2014, and U.S. Provisional Application Ser. No. 62/208,301, filed Aug. 21, 2015, each of which is incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/067433 | 12/22/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62208301 | Aug 2015 | US | |
| 62124485 | Dec 2014 | US |
