Patent Application
20150030600
Botulism is caused by botulinum neurotoxin secreted by members of the genus Clostridium and is characterized by flaccid paralysis, which if not immediately fatal requires prolonged hospitalization in an intensive care unit and mechanical ventilation. Naturally occurring botulism is found in infants or adults whose gastrointestinal tracts become colonized by Clostridial bacteria (infant or intestinal botulism), after ingestion of contaminated food products (food botulism), or in anaerobic wound infections (wound botulism) (Center for Disease Control (1998) Botulism in the United States, 1899-1998. Handbook for epidemiologists, clinicians, and laboratory workers. Atlanta, Ga. U.S. Department of Health and Human Services, Public Health Service: downloadable at “bt.cdc.gov/agent/botulism/index.asp”). Botulinum neurotoxins (BoNTs) are also classified by the Centers for Disease Control (CDC) as one of the six highest-risk threat agents for bioterrorism (the “Category A agents”), due to their extreme potency and lethality, ease of production and transport, and need for prolonged intensive care (Amon et al. (2001) JAMA 285: 1059-1070). As a result of these threats, specific pharmaceutical agents are needed for prevention and treatment of intoxication.
No specific small molecule drugs exist for prevention or treatment of botulism, but an investigational pentavalent toxoid vaccine is available from the CDC (Siegel (1988) J. Clin. Microbiol. 26: 2351-2356) and a recombinant vaccine is under development (Smith (1998) Toxicon 36: 1539-1548). Regardless, mass civilian or military vaccination is unlikely due to the rarity of disease or exposure and the fact that vaccination would prevent subsequent medicinal use of BoNT. Toxin neutralizing antibody (Ab) can be used for pre- or post-exposure prophylaxis or for treatment (Franz et al. (1993) Pp. 473-476 In B. R. DasGupta (ed.), Botulinum and Tetanus Neurotoxins: Neurotransmission and Biomedical Aspects. Plenum Press, New York). Small quantities of both equine antitoxin and human botulinum immune globulin exist and are currently used to treat adult (Black and Gunn. (1980) Am. J. Med., 69: 567-570; Hibbs et al. (1996) Clin. Infect. Dis., 23: 337-340) and infant botulism (Amon (1993). Clinical trial of human botulism immune globulin, p. 477-482. In B. R. DasGupta (ed.), Botulinum and Tetanus Neurotoxins: Neurotransmission and Biomedical Aspects. Plenum Press, New York) respectively.
The development of monoclonal antibody (mAb) therapy for botulism is complicated by the fact that there are at least seven BoNT serotypes (A-G) (Hatheway (1995) Curr. Top. Microbio. Immunol, 195: 55-75) that show little, if any, antibody cross-reactivity. While only four of the BoNT serotypes routinely cause human disease (A, B, E, and F), there has been one reported case of infant botulism caused by BoNT/C (Oguma et al. (1990) Lancet 336: 1449-1450), one outbreak of foodborne botulism linked to BoNT/D (Demarchi, et al. (1958) Bull. Acad. Nat. Med., 142: 580-582), and several cases of suspicious deaths where BoNT/G was isolated (Sonnabend et al. (1981) J. Infect. Dis., 143: 22-27). Aerosolized BoNT/C, D, and G have also been shown to produce botulism in primates by the inhalation route (Middlebrook and Franz (1997) Botulinum Toxins, chapter 33. In F. R. Sidell, E. T. Takafuji, D. R. Franz (eds.), Medical Aspects of Chemical and Biological Warfare. TMM publications, Washington, D.C.), and would most likely also affect humans. Thus, it is likely that any one of the seven BoNT serotypes can be used as a biothreat agent.
Variability of the BoNT gene and protein sequence within serotypes has also been reported and there is evidence that such variability can affect the binding of monoclonal antibodies to BoNT/A (Kozaki et al. (1998) Infect. Immun., 66: 4811-4816; Kozaki et al. (1995) Microbiol. Immunol., 39: 767-774).
Antibodies that bind to and neutralize and/or otherwise clear botulinum neurotoxin(s) are disclosed herein. Particularly effective neutralization of a BoNT serotype can be achieved by the use of neutralizing antibodies that bind two or more subtypes of the particular neurotoxin serotype with particularly high affinity and/or by combinations of such antibodies. The present disclosure provides antibodies that bind BoNT serotypes BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, BoNT/G, or mosaics. BoNT subtypes include pure BoNT/A1 (Hall hyper), BoNT/A2 (FRI-H1A2), BoNT/B1, BoNT/B2, BoNT/B3, BoNT/B4, BoNT/C1, BoNT/F1, BoNT/F2, BoNT/F3, BoNT/F4, BoNT/F5, BoNT/F6, BoNT/F7, BoNT/202F. BoNT mosaics include BoNT/CD and BoNT/DC. Compositions comprising neutralizing antibodies that bind two or more BoNT subtypes (e.g., BoNT/F1, BoNT/F2, BoNT/F3, etc.) with high affinity are also provided herein.
An antibody for Botulinum neurotoxin (BoNT) is provided herein. The antibody typically comprises at least one VH complementarity determining region (CDR) selected from an antibody from a clone listed in
The antibody may be a single chain Fv (scFv), a Fab, a (Fab′)2, an (ScFv)2, and the like. The antibody may be an IgG. The antibody may also be in a pharmaceutically acceptable excipient (e.g., in a unit dosage formulation).
Methods of inhibiting and/or neutralizing the activity of BoNT in a mammal may involve administering to a mammal in need thereof a composition comprising at least one neutralizing anti-BoNT antibody as described herein. The composition may include at least two different antibodies, each of which binds to different BoNT subtypes. The composition may also include at least three, at least four, or more different antibodies, each of which may bind to different BoNT epitopes.
Compositions provided herein may partially or fully neutralize a BoNT. The compositions typically include a first antibody that binds one or more serotypes, e.g., one or more antibodies as described above, can optionally include a second antibody, a third antibody, or a fourth antibody, or more that bind one or more BoNT serotypes.
Nucleic acids provided herein encode one or more antibodies that are described herein. Cells containing such nucleic acids are also provided herein. Kits provided for neutralizing a BoNT may include a composition containing one or more antibodies as described herein. The kits optionally also include instructional materials teaching the use of the composition to neutralize a BoNT. The composition may be stored in a disposable syringe.
A “BoNT polypeptide” refers to a Botulinum neurotoxin polypeptide (e.g., a BoNT/A polypeptide, a BoNT/B polypeptide, a BoNT/C polypeptide, and so forth). The BoNT polypeptide can refer to a full-length polypeptide or to a fragment thereof. Thus, for example, the term “BoNT/A polypeptide” refers to either a full-length BoNT/A (a neurotoxin produced by Clostridium botulinum of the type A serotype) or a fragment thereof (e.g. the HC fragment). The HC fragment of BoNT/A is an approximately 50 kDa C-terminal fragment (residues 873-1296) of BoNT/A (Lacy and Stevens (1999) J. Mol. Biol., 291: 1091-1104).
A “BoNT serotype” refers one of the standard known BoNT serotypes (e.g. BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, BoNT/G etc.).
The term “BoNT subtype” (e.g., a BoNT/A1 subtype) refers to botulinum neurotoxin gene sequences of a particular serotype (e.g., A, B, C, D, E, F, G etc.) that differ from each other sufficiently to produce differential antibody binding.
A “mosaic BoNT”, as used herein, refers to a BoNT polypeptide that contains at least two contiguous amino acid sequences, each of which is derived from a different serotype or subtype.
“Derived from” in the context of an amino acid sequence or polynucleotide sequence (e.g., an amino acid sequence “derived from” BoNT/F) is meant to indicate that the polypeptide or nucleic acid has a sequence that is based on that of a reference polypeptide or nucleic acid (e.g., a naturally occurring BoNT/F or encoding nucleic acid), and is not meant to be limiting as to the source or method in which the protein or nucleic acid is made.
An “anti-BoNT antibody” refers to an antibody that binds a BoNT polypeptide, specifically binds a BoNT polypeptide with a KD less than about 10−7, less than about 10−8, less than about 10−9, less than about 10−10, less than about 10−11, or less than about 10−12 or less.
“Neutralization” refers to a measurable decrease in the toxicity and/or circulating level of a Botulinum neurotoxin (e.g., BoNT/C) in in vitro testing, animals, or human patient.
By “treatment” it is meant that at least an amelioration of the symptoms associated with the condition afflicting the host is achieved, where amelioration refers to at least a reduction in the magnitude of a parameter, e.g. symptom, associated with the condition being treated. As such, treatment includes situations where the condition, or at least symptoms associated therewith, are reduced or avoided. Thus treatment includes: (i) prevention, that is, reducing the risk of development of clinical symptoms, including causing the clinical symptoms not to develop, e.g., preventing disease progression to a harmful or otherwise undesired state; (ii) inhibition, that is, arresting the development or further development of clinical symptoms, e.g., mitigating or completely inhibiting an active disease.
“Potency” refers to the degree of protection from challenge with BoNT. This can be measured/quantified for example, as an increase in the LD50 of a Botulinum neurotoxin (BoNT). In toxicology, the median lethal dose, LD50 (abbreviation for “Lethal Dose, 50%”), or LCt50 (Lethal Concentration & Time) of a toxic substance or radiation is the dose required to kill half the members of a tested population. The LD50 usually expressed as the mass of substance administered per unit mass of test subject, such as grams of substance per kilogram of body mass. Stating it this way allows the relative toxicity of different substances to be compared, and normalizes for the variation in the size of the animals exposed (although toxicity does not always scale simply with body mass). Typically, the LD50 of a substance is given in milligrams per kilogram of body weight. In the case of some toxins, the LD50 may be more conveniently expressed as micrograms per kilogram (μg/kg) of body mass.
The term “high affinity” when used with respect to an antibody refers to an antibody that specifically binds to its target(s) with an affinity (KD) of at least about 10−7 M at least about 10−8 M, preferably at least about 10−9 M, at least about 10−10 M, and at least about 10−11 M. “High affinity” antibodies may have a KD that ranges from about 1 nM to about 0.01 pM.
The following abbreviations are used herein: BoNT; Botulinum neurotoxin, BoNT/A; BoNT serotype A, BoNT/B; BoNT serotype B, BoNT/C; BoNT serotype C, BoNT/D; BoNT serotype D, BoNT/F; BoNT serotype F, BoNT/G; BoNT serotype G, Fc; fragment crystallizable, Fab′2; fragment, antigen binding, mAb; monoclonal antibody, IgG; immunoglobulin G, LD50; lethal dose 50%, scFv; single chain variable fragment, VH; heavy chain variable region, Vk; kappa light chain variable region, PCR; polymerase chain reaction, AgaII or Aga2; yeast agglutinin receptor II, BoNT/A LC; BoNT/A light chain, BoNT/B LC; BoNT/B light chain, BoNT/B HC; C-terminal domain of the BoNT/B heavy chain, pM; picomolar, fM; femtomolar, IU; International Unit, SD-CAA; selective dextrose casamino acids media, SG-CAA; selective galactose casamino acids media, CHO; Chinese hamster ovary cells, FACS; fluorescent activated cell sorting, KD; equilibrium dissociation constant, kon; association rate constant, koff; dissociation rate constant, MFI: mean fluorescent intensity
The terms “polypeptide”, “peptide”, and “protein” are used interchangeably herein to designate a linear series of amino acid residues connected one to the other by peptide bonds between the alpha-amino and carboxy groups of adjacent residues. The amino acid residues are usually in the natural “L” isomeric form. However, residues in the “D” isomeric form can be substituted for any L-amino acid residue, as long as the desired functional property is retained by the polypeptide. In addition, the amino acids, in addition to the 20 “standard” amino acids, include modified and unusual amino acids, which include, but are not limited to those listed in 37 CFR (§1.822(b)(4)). Furthermore, it should be noted that a dash at the beginning or end of an amino acid residue sequence indicates either a peptide bond to a further sequence of one or more amino acid residues or a covalent bond to a carboxyl or hydroxyl end group. However, the absence of a dash should not be taken to mean that such peptide bonds or covalent bond to a carboxyl or hydroxyl end group is not present, as it is conventional in representation of amino acid sequences to omit such.
The term “antibody” (also used interchangeably with “immunoglobulin”) encompasses polyclonal and monoclonal antibody preparations where the antibody may be of any class of interest (e.g., IgM, IgG, and subclasses thereof), as well as preparations including hybrid antibodies, altered antibodies, F(ab′)2 fragments, F(ab) molecules, Fv fragments, scFv fragments, single chain antibodies, single domain antibodies, chimeric antibodies, humanized antibodies, and functional fragments thereof which exhibit immunological binding properties of the parent antibody molecule. The antibodies may be conjugated to other moieties, and/or may be bound to a support (e.g., a solid support), such as a polystyrene plate or bead, test strip, and the like.
Immunoglobulin polypeptides include the kappa and lambda light chains and the alpha, gamma (IgG1, IgG2, IgG3, IgG4), delta, epsilon and mu heavy chains or equivalents in other species. Full-length immunoglobulin “light chains” (usually of about 25 kDa or about 214 amino acids) comprise a variable region of about 110 amino acids at the NH2-terminus and a kappa or lambda constant region at the COOH-terminus. Full-length immunoglobulin “heavy chains” (of about 50 kDa or about 446 amino acids), similarly comprise a variable region (of about 116 amino acids) and one of the aforementioned heavy chain constant regions, e.g., gamma (of about 330 amino acids).
An immunoglobulin light or heavy chain variable region is composed of a “framework” region (FR) interrupted by three hypervariable regions, also called “complementarity determining regions” or “CDRs”. The extent of the framework region and CDRs have been defined (see, “Sequences of Proteins of Immunological Interest,” E. Kabat et al., U.S. Department of Health and Human Services, (1991 and Lefranc et al. IMGT, the international ImMunoGeneTics information System®. Nucl. Acids Res., 2005, 33, D593-D597)). A detailed discussion of the IMGTS system, including how the IMGTS system was formulated and how it compares to other systems, is provided on the World Wide Web at imgt.cines.fr/textes/IMGTScientificChart/Numbering/IMGTnumberingsTable.html. The sequences of the framework regions of different light or heavy chains are relatively conserved within a species. The framework region of an antibody, that is the combined framework regions of the constituent light and heavy chains, serves to position and align the CDRs. The CDRs are primarily responsible for binding to an epitope of an antigen. All CDRs and framework provided by the present disclosure are defined according to Kabat et al, supra, unless otherwise indicated.
An “antibody” thus encompasses a protein having one or more polypeptides that can be genetically encodable, e.g., by immunoglobulin genes or fragments of immunoglobulin genes. The recognized immunoglobulin genes include the kappa, lambda, alpha, gamma, delta, epsilon and mu constant region genes, as well as myriad immunoglobulin variable region genes. Light chains are classified as either kappa or lambda. Heavy chains are classified as gamma, mu, alpha, delta, or epsilon, which in turn define the immunoglobulin classes, IgG, IgM, IgA, IgD and IgE, respectively.
A typical immunoglobulin (antibody) structural unit is known to comprise a tetramer. Each tetramer is composed of two identical pairs of polypeptide chains, each pair having one “light” (about 25 kD) and one “heavy” chain (about 50-70 kD). The N-terminus of each chain defines a variable region of about 100 to 110 or more amino acids primarily responsible for antigen recognition. The terms variable light chain (VL) and variable heavy chain (VH) refer to these light and heavy chains respectively.
Antibodies encompass intact immunoglobulins as well as a number of well characterized fragments produced by digestion with various peptidases. Thus, for example, pepsin digests an antibody below the disulfide linkages in the hinge region to produce F(ab)′2, a dimer of Fab which itself is a light chain joined to VH-CHI by a disulfide bond. The F(ab)′2 may be reduced under mild conditions to break the disulfide linkage in the hinge region thereby converting the (Fab′)2 dimer into an Fab′ monomer. The Fab′ monomer is essentially an Fab with part of the hinge region (see, Fundamental Immunology, W. E. Paul, ed., Raven Press, N.Y. (1993), for a more detailed description of other antibody fragments). While various antibody fragments are defined in terms of the digestion of an intact antibody, one of skill will appreciate that such Fab′ fragments may be synthesized de novo either chemically or by utilizing recombinant DNA methodology. Thus, the term antibody, as used herein also includes antibody fragments either produced by the modification of whole antibodies or synthesized de novo using recombinant DNA methodologies, including, but are not limited to, Fab′2, IgG, IgM, IgA, scFv, dAb, nanobodies, unibodies, and diabodies.
Antibodies and fragments of the present disclosure encompass those that are bispecific. Bispecific antibodies or fragments can be of several configurations. For example, bispecific antibodies may resemble single antibodies (or antibody fragments) but have two different antigen binding sites (variable regions). Bispecific antibodies may be produced by chemical techniques (Kranz et al. (1981) Proc. Natl. Acad. Sci., USA, 78: 5807), by “polydoma” techniques (see, e.g., U.S. Pat. No. 4,474,893), or by recombinant DNA techniques. Bispecific antibodies may have binding specificities for at least two different epitopes, at least one of which is an epitope of BoNT. The BoNT binding antibodies and fragments can also be heteroantibodies. Heteroantibodies are two or more antibodies, or antibody binding fragments (e.g., Fab) linked together, each antibody or fragment having a different specificity.
An “antigen-binding site” or “binding portion” refers to the part of an immunoglobulin molecule that participates in antigen binding. The antigen binding site is formed by amino acid residues of the N-terminal variable (“V”) regions of the heavy (“H”) and light (“L”) chains. Three highly divergent stretches within the V regions of the heavy and light chains are referred to as “hypervariable regions” which are interposed between more conserved flanking stretches known as “framework regions” or “FRs”. Thus, the term “FR” refers to amino acid sequences that are naturally found between and adjacent to hypervariable regions in immunoglobulins. In an antibody molecule, the three hypervariable regions of a light chain and the three hypervariable regions of a heavy chain are disposed relative to each other in three dimensional space to form an antigen binding “surface”. This surface mediates recognition and binding of the target antigen. The three hypervariable regions of each of the heavy and light chains are referred to as “complementarity determining regions” or “CDRs” and are characterized, for example by Kabat et al. Sequences of proteins of immunological interest, 4th ed. U.S. Dept. Health and Human Services, Public Health Services, Bethesda, Md. (1987).
A 4C4.1 antibody refers to an antibody expressed by clone 4C4.1 or to an antibody synthesized in other manners, but having the same CDRs and optionally, the same framework regions as the antibody expressed by clone 4C4.1. Similarly, antibody 4C4.2 and any other shown in
As used herein, the terms “immunological binding” and “immunological binding properties” refer to the non-covalent interactions of the type which occur between an immunoglobulin molecule and an antigen for which the immunoglobulin is specific. The strength or affinity of immunological binding interactions can be expressed in terms of the dissociation constant (KD) of the interaction, wherein a smaller KD represents a greater affinity. Immunological binding properties of selected polypeptides can be quantified using methods well known in the art. One such method entails measuring the rates of antigen binding site/antigen complex formation and dissociation, wherein those rates depend on the concentrations of the complex partners, the affinity of the interaction, and on geometric parameters that equally influence the rate in both directions. Thus, both the “on rate constant” (kon) and the “off rate constant” (koff) can be determined by calculation of the concentrations and the actual rates of association and dissociation. The ratio of koff/kon enables cancellation of all parameters not related to affinity and is thus equal to the equilibrium dissociation constant KD (see, generally, Davies et al. Ann. Rev. Biochem. 1990, 59: 439-15 473).
An “anti-BoNT antibody” refers to an antibody that binds to one or more Botulinum neurotoxin(s) (e.g., BoNT/C, BoNT/CD, etc.) Thus, for example the term “anti-BoNT/F— antibody”, as used herein refers to an antibody that specifically binds to a BoNT/F polypeptide (e.g, a BoNT/F1 polypeptide). An example of an antibody of the present disclosure may bind to an HC domain of a BoNT/C1 polypeptide.
Antibodies derived from anti-BoNT antibodies have a binding affinity of about 1.6×10−8 or better and can be derived by screening libraries of single chain Fv fragments displayed on phage or yeast constructed from heavy (VH) and light (VL) chain variable region genes obtained from mammals, including mice and humans, immunized with botulinum toxoid, toxin, or BoNT fragments. Antibodies can also be derived by screening phage or yeast display libraries in which a known BoNT-neutralizing variable heavy (VH) chain is expressed in combination with a multiplicity of variable light (VL) chains or conversely a known BoNT-neutralizing variable light chain is expressed in combination with a multiplicity of variable heavy (VH) chains. BoNT-neutralizing antibodies also include those antibodies produced by the introduction of mutations into the variable heavy or variable light complementarity determining regions (CDR1, CDR2 or CDR3) as described herein. Finally BoNT-neutralizing antibodies include those antibodies produced by any combination of these modification methods as applied to the BoNT-neutralizing antibodies described herein and their derivatives.
An “epitope” is a site on an antigen (e.g. BoNT) to which an antibody binds. Epitopes can be formed both from contiguous amino acids or noncontiguous amino acids juxtaposed by tertiary folding of a protein. Epitopes formed from contiguous amino acids are typically retained on exposure to denaturing solvents whereas epitopes formed by tertiary folding are typically lost on treatment with denaturing solvents. An epitope typically includes at least 3, and more usually, at least 5 or 8-10 amino acids in a spatial conformation. Methods of determining spatial conformation of epitopes include, for example, x-ray crystallography and 2-dimensional nuclear magnetic resonance. See, e.g., Epitope Mapping Protocols in Methods in Molecular Biology, Vol. 66, Glenn E. Morris, Ed (1996).
A neutralizing epitope refers to the epitope specifically bound by a neutralizing antibody.
“Isolated” refers to an entity of interest that is in an environment different from that in which the compound may naturally occur. An “isolated” compound (e.g., an “isolated” antibody) is separated from all or some of the components that accompany it in nature and may be substantially enriched, e.g., may be purified so that the compound is at least about 70% pure, at least about 80% pure, at least about 90% pure, at least about 95% pure, at least about 98% pure, at least about 99%, or greater than 99% pure, or free of impurities, contaminants, and/or components other than the compound. “Isolated” also refers to the state of a compound separated from all or some of the components that accompany it during manufacture (e.g., chemical synthesis, recombinant expression, culture medium, and the like).
A single chain Fv (“scFv”) polypeptide is a covalently linked VH::VL heterodimer which may be expressed from a nucleic acid including VH- and VL-encoding sequences either joined directly or joined by a peptide-encoding linker (Huston, et al. (1988) Proc. Nat. Acad. Sci. USA, 85: 5879-5883). A number of structures are available for converting the light and heavy polypeptide chains from an antibody V region into an scFv molecule which will fold into a three dimensional structure substantially similar to the structure of an antigen-binding site. See, e.g. U.S. Pat. Nos. 5,091,513 and 5,132,405 and 4,956,778.
Recombinant design methods may be used to develop suitable chemical structures (linkers) for converting two heavy and light polypeptide chains from an antibody variable region into a scFv molecule which will fold into a three-dimensional structure that is substantially similar to native antibody structure.
Design criteria include determination of the appropriate length to span the distance between the C-terminal of one chain and the N-terminal of the other, wherein the linker is generally formed from small hydrophilic amino acid residues that do not tend to coil or form secondary structures. Such methods have been described in the art. See, e.g., U.S. Pat. Nos. 5,091,513 and 5,132,405 to Huston et al.; and U.S. Pat. No. 4,946,778 to Ladner et al.
In this regard, the first general step of linker design involves identification of plausible sites to be linked. Appropriate linkage sites on each of the VH and VL polypeptide domains include those which will result in the minimum loss of residues from the polypeptide domains, and which will necessitate a linker comprising a minimum number of residues consistent with the need for molecule stability. A pair of sites defines a “gap” to be linked. Linkers connecting the C-terminus of one domain to the N-terminus of the next generally comprise hydrophilic amino acids which assume an unstructured configuration in physiological solutions and may be free of residues having large side groups which might interfere with proper folding of the VH and VL chains. Thus, suitable linkers generally comprise polypeptide chains of alternating sets of glycine and serine residues, and may include glutamic acid and lysine residues inserted to enhance solubility. One particular linker has the amino acid sequence (Gly4Ser)3 (SEQ ID NO:450). Another particularly preferred linker has the amino acid sequence comprising 2 or 3 repeats of [(Ser)4Gly] (SEQ ID NO:451), such as [(Ser)4Gly]3 (SEQ ID NO:452), and the like. Nucleotide sequences encoding such linker moieties can be readily provided using various oligonucleotide synthesis techniques known in the art (see, e.g., Sambrook, supra.).
The phrase “specifically binds to” or “specifically immunoreactive with”, when referring to an antibody refers to a binding reaction which is determinative of the presence of the protein in the presence of a heterogeneous population of proteins and other biologics. Thus, under designated immunoassay conditions, the specified antibodies bind to a particular protein and do not bind in a significant amount to other proteins present in the sample. Specific binding to a protein under such conditions may require an antibody that is selected for its specificity for a particular protein. For example, BoNT/F-neutralizing antibodies can be raised to BoNT/F protein(s) that specifically bind to BoNT/F protein(s), and not to other proteins present in a tissue sample. A variety of immunoassay formats may be used to select antibodies specifically immunoreactive with a particular protein. For example, solid-phase enzyme-linked immunosorbent assay (ELISA) immunoassays are routinely used to select monoclonal antibodies specifically immunoreactive with a protein. See Harlow and Lane (1988) Antibodies, A Laboratory Manual, Cold Spring Harbor Publications, New York, for a description of immunoassay formats and conditions that can be used to determine specific immunoreactivity.
The term “conservative substitution” is used in reference to proteins or peptides to reflect amino acid substitutions that do not substantially alter the activity (specificity or binding affinity) of the molecule. Typically conservative amino acid substitutions involve substituting one amino acid for another amino acid with similar chemical properties (e.g. charge or hydrophobicity). The following six groups each contain amino acids that are typical conservative substitutions for one another: 1) Alanine (A), Serine (S), Threonine (T); 2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N), Glutamine (Q); 4) Arginine (R), Lysine (K); 5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); and 6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W).
This disclosure provides antibodies that specifically bind to botulinum neurotoxin. Botulinum neurotoxin is produced by the anaerobic bacterium Clostridium botulinum. Botulinum neurotoxin poisoning (botulism) arises in a number of contexts including, but not limited to food poisoning (food borne botulism), infected wounds (wound botulism), “infant botulism” from ingestion of spores and production of toxin in the intestine of infants, and as a chemical/biological warfare agent. Botulism is a paralytic disease that typically begins with cranial nerve involvement and progresses caudally to involve the extremities. In acute cases, botulism can prove fatal.
For each BoNT serotype, there can be multiple subtypes of BoNT. Antibodies of the present disclosure encompass antibodies that specifically bind one subtype (e.g. the BoNT/A1 subtype) but not a different subtype (BoNT/A2 subtype) and also antibodies that can bind more than one subtype/serotype.
The present disclosure is related to the discovery of high affinity antibodies. The antibodies are particularly efficient in the neutralization of a botulism neurotoxin (BoNT) subtype. The antibodies have a high affinity for BoNT and each of the various antibodies is either highly specific for a serotype/subtype or can cross-react with two, three, or more serotypes/subtypes.
Neutralizations of BoNT may also be accomplished by using one, two, three, four, or more different antibodies directed against each of the subtypes, or alternatively, by the use of antibodies that are cross-reactive for different BoNT subtypes, or by bispecific or polyspecific antibodies with specificities for two, three, or four or more BoNT epitopes, and/or serotypes, and/or subtypes.
Compositions containing at least two, or at least three high affinity antibodies that bind overlapping (partial or complete overlapping) or non-overlapping epitopes on the BoNT are contemplated herein.
Thus, compositions contemplated herein may include one, two or more, three or more, four or more, five or more different antibodies selected from the antibodies described herein (see, e.g.,
Compositions contemplated herein may include antitoxins for BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, and/or BoNT/G (or mosaics thereof). Compositions containing trivalent BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, and/or BoNT/G antibodies (e.g. comprising antibodies selected from those described in PCT Pub. Nos. WO 07/094,754, WO 05/016232, WO 09/008,916, and WO 2010/014854) are also contemplated.
As indicated above, the antibodies provided by the present disclosure bind to one or more botulinum neurotoxin serotypes B, C, D, E, F, G (or mosaics thereof) and in certain instances Bont/A subtypes, and, in some embodiments, can neutralize the neurotoxin. Neutralization, in this context, refers to a measurable decrease in the toxicity and/or circulating level of the target neurotoxin. Such a decrease in toxicity can also be measured in vitro by a number of methods well known to those of skill in the art. One such assay involves measuring the time to a given percentage (e.g., 50%) twitch tension reduction in a hemidiaphragm preparation. Toxicity reduction can be determined in vivo, e.g. as an LD50 in a test animal (e.g. mouse) BoNT in the presence of one or more putative neutralizing antibodies. The neutralizing antibody or antibody combination can be combined with the botulinum neurotoxin prior to administration, or the animal can be administered the antibody prior to, simultaneous with, or after administration of the neurotoxin. The rate of clearance of BoNT mediated by a test antibody, or combination of test antibodies, can be measured (e.g. in mice) by administering labeled BoNT (e.g. radiolabeled BoNT) and measuring the levels of BoNT in the serum and the liver and other organs over time in the presence or absence of test antibody or antibodies (see, e.g., Ravichandran et al. (2006) J Pharmacol Exp Ther 318: 1343-1351 (2006).
The present disclosure also contemplates an antibody that specifically binds an epitope shared by two or more (e.g., two, three, four, five, six, or seven) BoNT serotypes and/or subtypes and/or mosaics, e.g., BoNT polypeptides that share at least about 45%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, at least about 98%, or at least about 99%, amino acid sequence identity over the complete holotoxin, over the light chain only, over the translocation domain only, or over the C-terminal third of the protein that includes the receptor-binding domain. See, e.g.,
As the antibodies of the present disclosure act to neutralize botulinum neurotoxins, they are useful in the treatment of pathologies associated with botulinum neurotoxin poisoning. The treatments essentially comprise administering to the poisoned organism (e.g. human or non-human mammal) a quantity of one or more neutralizing antibodies sufficient to neutralize (e.g. mitigate or eliminate) symptoms of BoNT poisoning.
Such treatments are most desired and efficacious in acute cases (e.g. where vital capacity is less than 30-40 percent of predicted and/or paralysis is progressing rapidly and/or hypoxemia with absolute or relative hypercarbia is present. These antibodies can also be used to treat early cases with symptoms milder than indicated (to prevent progression) or even prophylactically (a use the military envisions for soldiers going in harm's way). Treatment with the neutralizing antibody can be provided as an adjunct to other therapies (e.g. antibiotic treatment).
The antibodies provided by this disclosure can also be used for the rapid detection/diagnosis of botulism and thereby supplement and/or replace previous laboratory diagnostics.
This disclosure also provides the epitopes specifically bound by botulinum neurotoxin antibodies described herein. These epitopes can be used to isolate, and/or identify and/or screen for other antibodies BoNT neutralizing antibodies as described herein.
Anti-BoNT antibodies may be selected based on their affinity to one or more BoNT serotypes/subtypes. Numbering system used herein for toxins is based on Lacy et al. (1999) J. Mol. Biol. 291:1091-1104. A number of subtypes are known for each BoNT serotype. Thus, for example, BoNT/A subtypes include, but are not limited to, BoNT/A1, BoNT/A2, BoNT/A3, and the like. It is also noted, for example, that the BoNT/A1 subtype includes, but is not limited to 62A, NCTC 2916, ATCC 3502, and Hall hyper (Hall Allergan) and are identical (99.9-100% identity at the amino acid level.) and have been classified as subtype A1. The BoNT/A2 sequences (Kyoto-F and FRI-A2H) (Willems, et al. (1993) Res. Microbiol. 144:547-556) are 100% identical at the amino acid level. Another BoNT/A subtype, e.g. A3, is produced by a strain called Loch Maree that killed a number of people in an outbreak in Scotland.
Similarly, a number of subtypes are also known for BoNT/B, BoNT/E and BoNT/F and there exist mosaics of BoNT/C and of BoNT/D. The subject antibodies encompass high affinity antibodies that are cross-reactive with two or more subtypes within a serotype. The disclosure further provides antibodies that are cross-reactive with two or more serotypes (such as BoNT/E and BoNT/F). For example, antibody from clone 4E17.2 binds all subtypes of BoNT/A, BoNT/B, BoNT/E, BoNT/F).
Serotypes that can be bound by the subject antibodies include BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, BoNT/G, or mosaics thereof. Other BoNT subtypes/serotypes include pure BoNT/A1 (Hall hyper), BoNT/A2 (FRI-H1A2), BoNT/B1, BoNT/B2, BoNT/B3, BoNT/B4, BoNT/C1, BoNT/CD, BoNT/DC, BoNT/F1, BoNT/F2, BoNT/F3, BoNT/F4, BoNT/F5, BoNT/F6, and BoNT/F7. Moreover, without being bound to a particular theory, these cross-reactive antibodies can be more efficient in neutralizing Botulinum neurotoxin, particularly when used in combination one or more different neutralizing antibodies.
The sequences of the variable heavy (VH) and variable light (VL) domains for a number of BoNT (e.g. BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/F, BoNT/G) antibodies are illustrated in
The relationship of certain antibodies specific for each subtype from each serotype is described in the example section below.
The antibodies of the present disclosure can be used individually, and/or in combination with each other, and/or in combination with other known anti-BoNT antibodies (see, e.g., Application Pub. No: 20080124328, 20020155114, 20040175385, 20020155114, and PCT Pub. Nos. WO 07/094,754, WO 05/016232, WO 09/008,916, and WO 2010/014854, which are incorporated herein by reference for all purposes). These antibodies can be used individually, and/or in combination with each other, and/or in combination with other known anti-BoNT antibodies to form bispecific or polyspecific antibodies.
Amino acid sequences of various antibodies, as well as each CDR and framework region, are shown in
Using the teachings and the sequence information provided herein, the variable light and variable heavy chains can be joined directly or through a linker (e.g., (Gly4Ser)3, SEQ ID NO:450) to form a single-chain Fv antibody. The various CDRs and/or framework regions can be used to form human antibodies, chimeric antibodies, antibody fragments, polyvalent antibodies, and the like.
Anti-BoNT antibodies of the present disclosure have a binding affinity (KD) for a BoNT protein of at most 10−7, of at most 10−8, at most 10−9, at most 10−10, and most preferably at most 10−11, 10−12M or less. Some examples of KDs (M−1) for BoNT/C or BoNT/D fall in the following ranges: between about 2×10−12 to about 5×10−1°, between about 5×10−10 to about 1×10−9, between 1×10−9 to 5×10−9, between 5×10−9 to 1×10−8, between 4×10−9 to 2×10−8. Certain antibodies (e.g. 8DC4) have a KD of more than 20 nM.
Some examples of KDs (M−1) for BoNT/F fall in the following ranges: between about 5×10−11 to about 1×10−10, between about 1×10−10 to about 5×10−1°, between about 5×10−10 to about 1×10−9, between 1×10−9 to about 5×10−9. Certain antibodies can have a KD for BoNT/F in the range between about 1×10−8 to about 4×10−8. For example, antibody from clone 4E17.2, also referred herein as 6F5, can be described as having a KD of about 0.39 nM for BoNT/F.
As noted above, the antibody may also be defined by the serotypes and/or subtypes with which it is cross-reactive. Some antibodies have an affinity that is specific for only one serotype or subtype. Others are cross-reactive for two or more subtypes and/or serotypes. Examples of cross-reactive antibodies include 4C4.1, 4C4.2, 4C4, 4C10, 4C10.1, 4C10.2, 8DC1, 8DC1.2, 8DC2, 8DC4, and 8DC4.1. Other antibodies that are cross-reactive for two or more subtypes include certain antibodies designated as BoNT/F binders: 4E17.2 (also referred herein as 6F5), 6F8, 6F10, 38B8, 38F8, 39A1, 39D1.1, 41C2, etc. See Tables 1-8 for more details. Antibodies can also be reactive across two or more serotypes. For example, antibodies from clone 4E17.2 binds all subtypes of BoNT/A, BoNT/B, BoNT/E, and BoNT/F.
The antibody of the present disclosure may be defined by the epitope or the domain of BoNT bound by the antibody. The antibodies provided here may encompass those that bind to one or more epitopes or a specific domain of a BoNT to which an antibody containing one or more of the CDRs set forth in
For example, based on Table 8, an antibody such as 4C4, may be described by its affinity to the HN domain and its cross reactivity with BoNT/C1, BoNT/CD, BoNT/D, and BoNT/DC.
The subject antibody may also be defined by the epitope shared by one or more antibodies. The ability of a particular antibody to recognize the same and/or overlapping epitope as another antibody can be determined by the ability of one antibody to competitively inhibit binding of the second antibody to the antigen. Competitive inhibition of binding may also be referred to as cross-reactivity of antibodies. For example, 4C4 also binds to an epitope that overlaps with 4C10. Any of a number of competitive binding assays can be used to measure competition between two antibodies to the same antigen. For example, a sandwich ELISA assay can be used for this purpose. Additional methods for assaying for cross-reactivity are described later below.
A first antibody is considered to competitively inhibit binding of a second antibody, if binding of the second antibody to the antigen is reduced by at least 30%, usually at least about 40%, 50%, 60% or 75%, and often by at least about 90%, in the presence of the first antibody using any of the assays used to assess competitive binding.
Accordingly, antibodies provided by the present disclosure encompass those that compete for binding to a BoNT with an antibody that includes one or more of the VH CDRs set forth in
For example, an antibody may have the binding specificity (i.e., in this context, the same CDRs, or substantially the same CDRs) of an antibody having one or more VH and VL CDRs or full length VH and/or VL as set forth in
Examples of antibodies of the present disclosure are presented in Table 6 below. Although classified as a binder for a serotype, each antibody may be cross-reactive with more than one subtype/serotype, as described above. Details of cross-reactive antibodies can be found in Tables 1-5, 7, and 8.
Without being bound to a particular theory, it is believed that the current antitoxins used to treat botulism (horse and human) have a potency of about 5000 mouse LD50s/mg (human) and 55,000 mouse LD50s/mg (horse).
Based on calculation, a commercially desirable antitoxin may generally have a potency greater than about 10,000 to 100,000 LD50s/mg. Combinations of the antibodies described herein (e.g., two or three antibodies) can meet this potency. Thus, this disclosure provides antibodies and/or antibody combinations that neutralize at least about 10,000 mouse LD50s/mg of antibody, preferably at least about 15,000 mouse LD50s/mg of antibody, more preferably at least about 20,000 mouse LD50s/mg of antibody, and most preferably at least about 25,000 or more mouse LD50s/mg of antibody.
A) Recombinant Expression of Anti-BoNT Antibodies.
Using the information provided herein, the botulinum neurotoxin binding antibodies of the present disclosure are prepared using standard techniques well known to those of skill in the art.
For example, the polypeptide sequences provided herein (see, e.g.,
Using the sequence information provided, the nucleic acids may be synthesized according to a number of standard methods known to those of skill in the art. Oligonucleotide synthesis, is preferably carried out on commercially available solid phase oligonucleotide synthesis machines (Needham-VanDevanter et al. (1984) Nucleic Acids Res. 12:6159-6168) or manually synthesized using, for example, the solid phase phosphoramidite triester method described by Beaucage et. al. (1981) Tetrahedron Letts. 22(20): 1859-1862.
Once a nucleic acid encoding an anti-BoNT antibody is synthesized it can be amplified and/or cloned according to standard methods. Molecular cloning techniques to achieve these ends are known in the art. A wide variety of cloning and in vitro amplification methods suitable for the construction of recombinant nucleic acids are known to persons of skill Examples of these techniques and instructions sufficient to direct persons of skill through many cloning exercises are found in Berger and Kimmel, Guide to Molecular Cloning Techniques, Methods in Enzymology volume 152 Academic Press, Inc., San Diego, Calif. (Berger); Sambrook et al. (1989) Molecular Cloning—A Laboratory Manual (2nd ed.) Vol. 1-3, Cold Spring Harbor Laboratory, Cold Spring Harbor Press, NY, (Sambrook); and Current Protocols in Molecular Biology, F. M. Ausubel et al., eds., Current Protocols, a joint venture between Greene Publishing Associates, Inc. and John Wiley & Sons, Inc., (1994 Supplement) (Ausubel). Methods of producing recombinant immunoglobulins are also known in the art. See, Cabilly, U.S. Pat. No. 4,816,567; and Queen et al. (1989) Proc. Nat'l Acad. Sci. USA 86: 10029-10033.
Examples of techniques sufficient to direct persons of skill through in vitro amplification methods, including the polymerase chain reaction (PCR), the ligase chain reaction (LCR), Qβ-replicase amplification and other RNA polymerase mediated techniques are found in Berger, Sambrook, and Ausubel, as well as Mullis et al., (1987) U.S. Pat. No. 4,683,202; PCR Protocols A Guide to Methods and Applications (Innis et al. eds) Academic Press Inc. San Diego, Calif. (1990) (Innis); Arnheim & Levinson (Oct. 1, 1990) C&EN 36-47; The Journal Of NIH Research (1991) 3, 81-94; (Kwoh et al. (1989) Proc. Natl. Acad. Sci. USA 86, 1173; Guatelli et al. (1990) Proc. Natl. Acad. Sci. USA 87, 1874; Lomell et al. (1989) J. Clin. Chem. 35, 1826; Landegren et al., (1988) Science 241, 1077-1080; Van Brunt (1990) Biotechnology 8, 291-294; Wu and Wallace, (1989) Gene 4, 560; and Barringer et al. (1990) Gene 89, 117. Improved methods of cloning in vitro amplified nucleic acids are described in Wallace et al., U.S. Pat. No. 5,426,039.
Once the nucleic acid for an anti-BoNT antibody is isolated and cloned, one can express the gene in a variety of recombinantly engineered cells known to those of skill in the art. Examples of such cells include bacteria, yeast, filamentous fungi, insect (especially employing baculoviral vectors), plant, and mammalian cells. It is expected that those of skill in the art are knowledgeable in the numerous expression systems available for expression of antibodies.
In brief summary, the expression of natural or synthetic nucleic acids encoding anti-BoNT antibodies will typically be achieved by operably linking a nucleic acid encoding the antibody to a promoter (which is either constitutive or inducible), and incorporating the construct into an expression vector. The vectors can be suitable for replication and integration in prokaryotes, eukaryotes, or both. Typical cloning vectors contain transcription and translation terminators, initiation sequences, and promoters useful for regulation of the expression of the nucleic acid encoding the anti-BoNT antibody. The vectors optionally comprise generic expression cassettes containing at least one independent terminator sequence, sequences permitting replication of the cassette in both eukaryotes and prokaryotes, i.e., shuttle vectors, and selection markers for both prokaryotic and eukaryotic systems. See Sambrook et al (1989) supra.
To obtain high levels of expression of a cloned nucleic acid it is common to construct expression plasmids which typically contain a strong promoter to direct transcription, a ribosome binding site for translational initiation, and a transcription/translation terminator. Examples of regulatory regions suitable for this purpose in E. coli are the promoter and operator region of the E. coli tryptophan biosynthetic pathway as described by Yanofsky (1984) J. Bacteriol., 158:1018-1024, and the leftward promoter of phage lambda (PL) as described by Herskowitz and Hagen (1980) Ann. Rev. Genet., 14:399-445 and the L-arabinose (araBAD) operon (Better (1999) Gene Exp Systems pp 95-107 Academic Press, Inc., San Diego, Calif.). The inclusion of selection markers in DNA vectors transformed in E. coli is also useful. Examples of such markers include genes specifying resistance to ampicillin, tetracycline, or chloramphenicol. See Sambrook et al (1989) supra for details concerning selection markers, e.g., for use in E. coli.
Expression systems for expressing anti-BoNT antibodies are available using, for example, E. coli, Bacillus sp. (see, e.g., Palva, et al. (1983) Gene 22:229-235; Mosbach et al. (1983) Nature, 302: 543-545), and Salmonella. E. coli systems may also be used.
The anti-BoNT antibodies produced by prokaryotic cells may require exposure to chaotropic agents for proper folding. During purification from, e.g., E. coli, the expressed protein is optionally denatured and then renatured. This can be accomplished, e.g., by solubilizing the bacterially produced antibodies in a chaotropic agent such as guanidine HCl. The antibody is then renatured, either by slow dialysis or by gel filtration (see, e.g., U.S. Pat. No. 4,511,503). Alternatively, nucleic acid encoding the anti-BoNT antibodies may be operably linked to a secretion signal sequence such as pelB so that the anti-BoNT antibodies are secreted into the medium in correctly-folded form (Better et al (1988) Science 240: 1041-1043).
Methods of transfecting and expressing genes in mammalian cells are known in the art (see e.g. Birch and Racher Adv. Drug Deliv. Rev. 2006, 58: 671-685). Transducing cells with nucleic acids can involve, for example, incubating viral vectors containing anti-BoNT nucleic acids with cells within the host range of the vector (see, e.g., Goeddel (1990) Methods in Enzymology, vol. 185, Academic Press, Inc., San Diego, Calif. or Krieger (1990) Gene Transfer and Expression—A Laboratory Manual, Stockton Press, New York, N.Y. and the references cited therein).
The culture of cells used in the present disclosure, including cell lines and cultured cells from tissue or blood samples is well known in the art (see, e.g., Freshney (1994) Culture of Animal Cells, a Manual of Basic Technique, third edition, Wiley-Liss, N.Y. and the references cited therein).
Techniques for using and manipulating antibodies are found in Coligan (1991) Current Protocols in Immunology Wiley/Greene, NY; Harlow and Lane (1989) Antibodies: A Laboratory Manual Cold Spring Harbor Press, NY; Stites et al. (eds.) Basic and Clinical Immunology (4th ed.) Lange Medical Publications, Los Altos, Calif., and references cited therein; Goding (1986) Monoclonal Antibodies: Principles and Practice (2d ed.) Academic Press, New York, N.Y.; and Kohler and Milstein (1975) Nature 256: 495-497.
The anti-BoNT antibody gene(s) (e.g. anti-BoNT scFv gene) may be subcloned into the expression vector pUC119mycHis (Tomlinson et al. (1996) J. Mol. Biol., 256: 813-817) or pSYN3, resulting in the addition of a hexahistidine tag at the C-terminal end of the scFv to facilitate purification. Detailed protocols for the cloning and purification of certain anti-BoNT antibodies are found, for example, in Amersdorfer et al. (1997) Infect. Immunity, 65(9): 3743-3752, and the like.
B) Preparation of Whole Polyclonal or Monoclonal Antibodies.
The anti-BoNT antibodies of the present disclosure include individual, allelic, strain, or species variants, and fragments thereof, both in their naturally occurring (full-length) forms and in recombinant forms. Certain antibodies may be selected to bind one or more epitopes bound by the antibodies described herein (as seen in
1) Polyclonal Antibody Production.
Methods of producing polyclonal antibodies are known to those of skill in the art. In brief, an immunogen (e.g., BoNT/A, BoNT/B, BoNT/E, etc.), subsequences including, but not limited to subsequences comprising epitopes specifically bound by antibodies expressed by clones disclosed herein, preferably a purified polypeptide, a polypeptide coupled to an appropriate carrier (e.g., GST, keyhole limpet hemanocyanin, etc.), or a polypeptide incorporated into an immunization vector such as a recombinant vaccinia virus (see, U.S. Pat. No. 4,722,848) is mixed with an adjuvant and animals are immunized with the mixture. The animal's immune response to the immunogen preparation is monitored by taking test bleeds and determining the titer of reactivity to the polypeptide of interest. When appropriately high titers of antibody to the immunogen are obtained, blood is collected from the animal and antisera are prepared. Further fractionation of the antisera to enrich for antibodies reactive to the BoNT polypeptide is performed where desired (see, e.g., Coligan (1991) Current Protocols in Immunology Wiley/Greene, NY; and Harlow and Lane (1989) Antibodies: A Laboratory Manual Cold Spring Harbor Press, NY).
Antibodies that specifically bind to the epitopes described herein can be selected from polyclonal sera using the selection techniques described herein.
2) Monoclonal Antibody Production.
In some instances, it is desirable to prepare monoclonal antibodies from various mammalian hosts, such as mice, rodents, primates, humans, etc. Descriptions of techniques for preparing such monoclonal antibodies are found in, e.g., Stites et al. (eds.) Basic and Clinical Immunology (4th ed.) Lange Medical Publications, Los Altos, Calif., and references cited therein; Harlow and Lane, supra; Goding (1986) Monoclonal Antibodies: Principles and Practice (2d ed.) Academic Press, New York, N.Y.; and Kohler and Milstein (1975) Nature 256: 495-497.
Summarized briefly, monoclonal antibody production using hybridomas may proceed by injecting an animal with an immunogen (e.g., BoNT/A, BoNT/B, BoNT/E, etc.) subsequences including, but not limited to subsequences comprising epitopes specifically bound by antibodies expressed by clones disclosed herein. The animal is then sacrificed and cells taken from its spleen, which are fused with myeloma cells. The result is a hybrid cell or “hybridoma” that is capable of reproducing antibodies in vitro. The population of hybridomas is then screened to isolate individual clones, each of which secretes a single antibody species to the immunogen. In this manner, the individual antibody species obtained are the products of immortalized and cloned single B cells from the immune animal generated in response to a specific site recognized on the immunogenic substance.
Alternative methods of immortalization include transformation with Epstein Barr Virus, oncogenes, or retroviruses, or other methods known in the art. Colonies arising from single immortalized cells are screened for production of antibodies of the desired specificity and affinity for the BoNT antigen, and yield of the monoclonal antibodies produced by such cells is enhanced by various techniques, including injection into the peritoneal cavity of a vertebrate (preferably mammalian) host. The antibodies of the present disclosure are used with or without modification, and include chimeric antibodies such as humanized murine antibodies.
Techniques for creating recombinant DNA versions of the antigen-binding regions of antibody molecules which bypass the generation of hybridomas are contemplated for the present BoNT binding antibodies and fragments. DNA is cloned into a bacterial expression system. One example of a suitable technique uses a bacteriophage lambda vector system having a leader sequence that causes the expressed Fab protein to migrate to the periplasmic space (between the bacterial cell membrane and the cell wall) or to be secreted. One can rapidly generate and screen great numbers of functional Fab fragments for those which bind BoNT. Such BoNT binding agents (Fab fragments with specificity for a BoNT polypeptide) are specifically encompassed within the BoNT binding antibodies and fragments of the present disclosure. Other methods for screening and production of antibodies may employ one or more of display systems such as phage display, yeast display, ribosome, etc., and an antibody production system such as that derived from transgenic mice.
The present disclosure provides an isolated nucleic acid comprising a nucleotide sequence encoding an amino acid sequence of a VH of a subject antibody. The present disclosure provides an isolated nucleic acid comprising a nucleotide sequence encoding an amino acid sequence of a VL of a subject antibody. The present disclosure provides an isolated nucleic acid comprising a nucleotide sequence encoding an amino acid sequence of a VH and a VL of a subject antibody. In some instances, a subject nucleic acid comprises a nucleotide sequence encoding VH CDR1, CDR2, and CDR3 of a subject antibody and/or a VL CDR1, CDR2, and CDR3 of a subject antibody.
The present disclosure provides an isolated nucleic acid comprising a nucleotide sequence encoding an amino acid sequence of a VH of an antibody selected from the group consisting of a VH comprising a CDR1, CDR2 and CDR3, wherein the CDR1, CDR2 and CDR3 are selected from a VH of an antibody selected from the group consisting of 4C4.2, 8DC1.2, 4C10.2, 8DC4.1, 4C2, 8DC2, 8D1, 87C78, 8DC8, 4C10.1, 2B23EK4, 6F5, 6F5.1, hu6F8, hu6F10, 7G1.1, 7G2.1, 6A1M, 6A2M, 6A3M, 6A4M, 6A5M, 6A6M, 6A7M, 6A8M, 6A9M, 1C7, 1C10, 1D8, 1G11, 1H5, 9B2, 10C9, 10H10, 16B3, 16D5, 18A6, 18D10, 18E5, 18F2, 19A9, 19B6, 19D2, 19D22, 19D22.4, 19G6, 31A5, 31A5.1, 31C3, 31C3.6, 31E2, 31E2.20, 31G2, 31H3, 34E8, 34E8B12, 26A10, 26B2, 26C2, 26C4, 26D1, 26D9, 26D10, 26D11, 26E1, 26E2, 26E6, 26G5, 26G11, 26H11, 1B12.3, 1B12.4, 1C1, 1C1.1, 1C2, 1C3, 1C4, 1C8, 87C1, 87C2, 87C78, 4C1, 4C3, 4C4.1, 4C4, 4C5, 4C6, 4C7, 4C8, 4C9, 4C10, 8C1, 8C2, 8C3, 8C4, 8C5, 8C6, 8D2, 8DC1, 8DC3, 8DC4, 8DC5, 8DC6, 8DC7, 8DC10, 8DC11, 8DC12, 8DC13, 8DC14, 8DC15, 6F1, 6F3, 6F4, 39A1, 41C2, 43D3, 39H6, 41E2, 41F7, 42G8, 39D1.1, 41A4, 41B7, 39D5.1, 41G8, 6F6, 6F7, 6F8, 6F9, hu6F9, 6F10, 28C9, 28H4, 29A2, 29B8, 30C8, 32G2, 37B4, 37B6, 38B8, 38C1, 38D11, 38F8, 4B19, 4B19.1, 7G1, 7G2, 2B23K1, 2B23K2, 2B23K4, 2B23K7, 2B23K11, 7G3, 7G4, 7G5, 7G6, 7G7, 7G8, 7G9, 7G10, 7G11, 2B23EK1, 2B23EK5, 2B23EK6, 2B23EK7, 2B23EK10, 2B23EK11, 2B23EK12, 8D2.2, 8D2.3, 8DC3.1, 8DC8.3, 8DC8.6, B4, A9, and/or A2S; and/or
a VL comprising a CDR1, CDR2 and CDR3, wherein the CDR1, CDR2 and CDR3 are selected from a VL of an antibody selected from the group consisting of 4C4.2, 8DC1.2, 4C10.2, 8DC4.1, 4C2, 8DC2, 8D1, 87C78, 8DC8, 4C10.1, 2B23EK4, 6F5, 6F5.1, hu6F8, hu6F10, 7G1.1, 7G2.1, 6A1M, 6A2M, 6A3M, 6A4M, 6A5M, 6A6M, 6A7M, 6A8M, 6A9M, 1C7, 1C10, 1D8, 1G11, 1H5, 9B2, 10C9, 10H10, 16B3, 16D5, 18A6, 18D10, 18E5, 18F2, 19A9, 19B6, 19D2, 19D22, 19D22.4, 31A5, 31A5.1, 31C3, 31C3.6, 31E2, 31E2.20, 31G2, 31H3, 34E8B12, 26A10, 26B2, 26C2, 26C4, 26D1, 26D9, 26D10, 26D11, 26E2, 26E6, 26G5, 26G11, 26H11, 1B12.3, 1B12.4, 1C1, 1C1.1, 1C2, 1C3, 1C4, 1C8, 87C1, 87C2, 87C78, 4C1, 4C3, 4C4.1, 4C4, 4C5, 4C6, 4C7, 4C8, 4C9, 4C10, 4C10.2, 8C1, 8C2, 8C3, 8C4, 8C5, 8C6, 8D1, 8D2, 8DC1, 8DC3, 8DC4, 8DC5, 8DC6, 8DC7, 8DC10, 8DC11, 8DC12, 8DC13, 8DC14, 8DC15, 6F1, 6F3, 6F4, 39A1, 41C2, 43D3, 39H6, 41E2, 41F7, 42G8, 39D1.1, 41A4, 41B7, 39D5.1, 41G8, 6F6, 6F7, 6F8, 6F9, hu6F9, 6F10, 28C9, 28H4, 29A2, 29B8, 30C8, 32G2, 37B4, 37B6, 38B8, 38C1, 38D11, 38F8, 4B19, 4B19.1, 7G1, 7G2, 7G7, 7G8, 7G9, 7G10, 7G11, 2B23EK1, 2B23EK4, 2B23EK5, 2B23EK6, 2B23EK7, 2B23EK10, 2B23EK11, 2B23EK12, 8D2.2, 8D2.3, 8DC3.1, 8DC8.3, 8DC8.6, B4, A9, and/or A2S.
The nucleic acid can be a recombinant vector, as described above, which provides for amplification and/or expression (synthesis) of the encoded antibody. The recombinant vector can be suitable for expression in prokaryotic and/or eukaryotic cells.
The present disclosure also provides a cell, e.g., a genetically modified cell, that comprises a subject nucleic acid. A subject genetically modified cell can be a prokaryotic cell (e.g., a bacterial cell); or a eukaryotic cell (e.g., an insect cell; a mammalian cell, such as a mammalian cell line suitable for in vitro cell culture; a yeast cell; etc.), where the cell may produce the encoded antibody.
IV. Modification of anti-BoNT antibodies.
A) Display techniques can be used to increase antibody affinity.
To create higher affinity antibodies, mutant scFv gene repertories, based on the sequence of a binding scFv (see, e.g.,
Since the antibody fragments on the surface of the phage are functional, those phage bearing antigen binding antibody fragments can be separated from non-binding or lower affinity phage by antigen affinity chromatography (McCafferty et al. (1990) Nature, 348: 552-554). Mixtures of phage are allowed to bind to the affinity matrix, non-binding or lower affinity phage are removed by washing, and bound phage are eluted by treatment with acid or alkali.
By infecting bacteria with the eluted phage or modified variants of the eluted phage as described below, more phage can be grown and subjected to another round of selection. In this way, an enrichment of 1000 fold in one round may become 1,000,000 fold in two rounds of selection (see, e.g., McCafferty et al. (1990) Nature, 348: 552-554). Thus, even when enrichments in each round are low, multiple rounds of affinity selection leads to the isolation of rare phage and the genetic material contained within which encodes the sequence of the binding antibody (see, e.g., Marks et al. (1991) J. Mol. Biol., 222: 581-597). The physical link between genotype and phenotype provided by phage display makes it possible to test every member of an antibody fragment library for binding to antigen, even with libraries as large as 100,000,000 clones. For example, after multiple rounds of selection on antigen, a binding scFv that occurred with a frequency of only 1/30,000,000 clones was recovered (Marks et al. (1991) J. Mol. Biol., 222: 581-597.).
Yeast display may also be utilized to increase antibody affinity and has the ability to finely discriminate between mutants of close affinity. Antibody variable region genes (V-genes) may be diversified either randomly or using spiked oligonucleotides, and higher affinity mutants selected using various types of affinity chromatography or flow cytometry (see, e.g, Razai A. et al. (2005) J. Mol. Biol. 351:158-169. Lou J. et al. (2010). Protein Engineering, Design & Selection, 23(4):311-319).
1) Chain Shuffling.
One approach for creating mutant scFv gene repertoires involves replacing either the VH or VL gene from a binding scFv with a repertoire of VH or VL genes (chain shuffling) (see, e.g., Clackson et al. (1991) Nature, 352: 624-628). Such gene repertoires contain numerous variable genes derived from the same germline gene as the binding scFv, but with point mutations (see, e.g., Marks et al. (1992) Bio/Technology, 10: 779-783, Lou J. et al. (2010). Protein Engineering, Design & Selection, 23(4):311-319). Using light or heavy chain shuffling and phage display or yeast display, the binding avidities of, e.g., BoNT/E or BoNT/B binding antibody fragment can be dramatically increased (see, e.g., Marks et al. (1992) Bio/Technology, 10: 779-785).
Thus, to alter the affinity of anti-BoNT antibody a mutant scFv gene repertoire may be created containing the VH gene of a known anti-BoNT antibody and a VL gene repertoire (light chain shuffling). Alternatively, an scFv gene repertoire is created containing the VL gene of a known anti-BoNT antibody and a VH gene repertoire (heavy chain shuffling). The scFv gene repertoire may be cloned into a phage display vector (e.g., pHEN-1, Hoogenboom et al. (1991) Nucleic Acids Res., 19: 4133-4137) or yeast display vector (e.g., pYD2. Razai A. et al. (2005) J. Mol. Biol. 351:158-169), and after transformation a library of transformants is obtained. Phage or yeasts are prepared and selections are performed accordingly. In addition to chain shuffling, it is also possible to shuffle individual complementarity determining regions (CDRs).
The antigen concentration may be decreased in each round of selection, reaching a concentration less than the desired Kd by the final rounds of selection. This results in the selection of phage or yeast clones which expressed antibody on the basis of affinity with the antigen (Hawkins et al. (1992) J. Mol. Biol. 226: 889-896).
Chain shuffling may be combined with the stringent selections made possible by yeast display and flow cytometry. This novel approach was found to be particularly powerful for increasing antibody affinity (see example 1).
2) Increasing the Affinity of Anti-BoNT Antibodies by Site Directed Mutagenesis.
The majority of antigen contacting amino acid side chains are located in the complementarity determining regions (CDRs), three in the VH (CDR1, CDR2, and CDR3) and three in the VL (CDR1, CDR2, and CDR3) (see, e.g., Chothia et al. (1987) J. Mol. Biol., 196: 901-917; Chothia et al. (1986) Science, 233: 755-8; Nhan et al. (1991) J. Mol. Biol., 217: 133-151). Without being bound to a theory, it is believed that these residues contribute the majority of binding energetics responsible for antibody affinity for antigen. In other molecules, mutating amino acids that contact ligand has been shown to be an effective means of increasing the affinity of one protein molecule for its binding partner (Lowman et al. (1993) J. Mol. Biol., 234: 564-578; Wells (1990) Biochemistry, 29: 8509-8516). Thus mutation (randomization) of the CDRs and screening against, for example, BoNT/A, BoNT/B, BoNT/F, or the epitopes thereof, can be used to generate anti-BoNT antibodies having improved binding affinity.
Each CDR is randomized in a separate library, using a selected antibody as a template. To simplify affinity measurement, a lower affinity anti-BoNT antibody is used as a template, rather than a higher affinity scFv. The CDR sequences of the highest affinity mutants from each CDR library are combined to obtain an additive increase in affinity. A similar approach has been used to increase the affinity of human growth hormone (hGH) for the growth hormone receptor over 1500 fold from 3.4×10−10 to 9.0×10−13 M (see, e.g., Lowman et al. (1993) J. Mol. Biol., 234: 564-578).
To increase the affinity of anti-BoNT antibodies, amino acid residues located in one or more CDRs (e.g., 9 amino acid residues located in VL CDR3) are partially randomized by synthesizing a “doped” oligonucleotide in which the wild type nucleotide occurred with a frequency of, e.g. 49%. The oligonucleotide is used to amplify the remainder of the anti-BoNT scFv gene(s) using PCR.
For example, to create a library in which VH CDR3 is randomized, an oligonucleotide is synthesized which anneals to the anti-BoNT antibody VH framework 3 and encodes VH CDR3 and a portion of framework 4. At the four positions to be randomized, the sequence NNS can be used, where N is any of the 4 nucleotides, and S is “C” or “T”. The oligonucleotide is used to amplify the anti-BoNT antibody VH gene using PCR, creating a mutant anti-BoNT antibody VH gene repertoire. PCR is used to splice the VH gene repertoire with the anti-BoNT antibody light chain gene, and the resulting scFv gene repertoire cloned into a phage display vector (e.g., pHEN-1 or pCANTAB5E). Ligated vector DNA is used to transform electrocompetent E. coli to produce a phage antibody library.
To select higher affinity mutant scFv, each round of selection of the phage antibody libraries is conducted on decreasing amounts of one or more BoNT subtypes. Clones from the third and fourth round of selection can be screened for binding to the desired antigen(s) (e.g., BoNT/B, BoNT/F, BoNT/G, etc.) by ELISA on 96 well plates. The scFv from, e.g., twenty to forty ELISA positive clones can be expressed, e.g. in 10 ml cultures, the periplasm harvested, and the scFv koff determined by BIAcore. Clones with the slowest koff are sequenced, and each unique scFv subcloned into an appropriate vector (e.g., pUC119 mycHis). The scFv are expressed in culture, and purified. Affinities of purified scFv can be determined by BIAcore.
Instead of using phage display, yeast display can also be used for affinity maturation. By way of illustration,
3) Creation of Anti-BoNT (scFv′)2 Homodimers.
To create anti-BoNT (scFv′)2 antibodies, two anti-BoNT scFvs are joined, either through a linker (e.g., a carbon linker, a peptide, etc.) or through a disulfide bond between, for example, two cysteines. Thus, for example, to create disulfide linked scFv, a cysteine residue can be introduced by site directed mutagenesis between a myc tag and a hexahistidine tag at the carboxy-terminus of an anti-BoNT/B. Introduction of the correct sequence can be verified by DNA sequencing. The construct may be in pUC119, so that the pelB leader directs expressed scFv to the periplasm and cloning sites (Ncol and Notl) exist to introduce anti-BoNT mutant scFv. Expressed scFv has the myc tag at the C-terminus, followed by two glycines, a cysteine, and then 6 histidines to facilitate purification by IMAC. After disulfide bond formation between the two cysteine residues, the two scFv can be separated from each other by 26 amino acids (two 11 amino acid myc tags and three repeats of a unit with 4 glycines plus one serine). An scFv expressed from this construct, purified by IMAC may predominantly comprise monomeric scFv. To produce (scFv′)2 dimers, the cysteine can be reduced by incubation with 1 mM beta-mercaptoethanol, and half of the scFv blocked by the addition of DTNB. Blocked and unblocked scFvs can be incubated together to form (scFv′)2 and the resulting material can optionally be analyzed by gel filtration. The affinity of the anti-BoNT scFv′ monomer and (scFv′)2 dimer can optionally be determined by BIAcore.
The (scFv′)2 dimer may be created by joining the scFv fragments through a linker, more preferably through a peptide linker. This can be accomplished by a wide variety of means well known to those of skill in the art. For example, one preferred approach is described by Holliger et al. (1993) Proc. Natl. Acad. Sci. USA, 90: 6444-6448 (see also WO 94/13804).
Typically, linkers are introduced by PCR cloning. For example, synthetic oligonucleotides encoding the 5 amino acid linker (Gly4Ser, SEQ ID NO:451) can be used to PCR amplify the anti-BoNT antibody VH and VL genes which are then spliced together to create the anti-BoNT diabody gene. The gene can then be cloned into an appropriate vector, expressed, and purified according to standard methods well known to those of skill in the art.
4) Preparation of Anti-BoNT (scFv)2, Fab, and (Fab′)2 Molecules.
Anti-BoNT antibodies such as anti-BoNT/F or anti-BoNT/B scFv, or variant(s) with higher affinity, are suitable templates for creating size and valency variants. For example, an anti-BoNT (scFv′)2 can be created from the parent scFv as described above. An scFv gene can be excised using appropriate restriction enzymes and cloned into another vector as described herein.
Expressed scFv may include a myc tag at the C-terminus, followed by two glycines, a cysteine, and six histidines to facilitate purification. After disulfide bond formation between the two cystine residues, the two scFv may be separated from each other by 26 amino acids (e.g., two eleven amino acid myc tags and four glycines). Single-chain Fv (scFv) can be expressed from this construct and purified.
To produce (scFv′)2 dimers, the cysteine is reduced by incubation with 1 mM β-mercaptoethanol, and half of the scFv blocked by the addition of DTNB. Blocked and unblocked scFv are incubated together to form (scFv′)2, which is purified. As higher affinity scFv are isolated, their genes are similarly used to construct (scFv′)2.
Anti-BoNT Fab may also be expressed in E. coli using an expression vector similar to the one described by Better et. al. (1988) Science, 240: 1041-1043. For example, to create a BoNT/B or BoNT/F binding Fab, the VH and VL genes are amplified from the scFv using PCR. The VH gene is cloned into an expression vector (e.g., a pUC119 based bacterial expression vector) that provides an IgG CH1 domain downstream from, and in frame with, the VH gene. The vector also contains the lac promoter, a pelB leader sequence to direct expressed VH-CH1 domain into the periplasm, a gene 3 leader sequence to direct expressed light chain into the periplasm, and cloning sites for the light chain gene. Clones containing the correct VH gene are identified, e.g., by PCR fingerprinting. The VL gene is spliced to the CL gene using PCR and cloned into the vector containing the VH CH1 gene.
B) Selection of Antibodies.
Selection of anti-BoNT antibodies (whether produced by phage display, yeast display, immunization methods, hybridoma technology, etc.) involves screening the resulting antibodies for specific binding to an appropriate antigen(s). In the instant case, suitable antigens can include, but are not limited to BoNT/G, BoNT/F1, BoNT/F3, BoNT/E1, BoNT/E2, BoNT/E3, BoNT/B1, BoNT/B2, BoNT/B3, BoNT/B4, BoNT/A1, BoNT/A2, BoNT/A3, a C-terminal domain of BoNT heavy chain (binding domain) of BoNT holotoxins, recombinant BoNT domains such as HC (binding domain), HN (translocation domain), or LC (light chain), and the like. The antibodies may be selected for specific binding of an epitope recognized by one or more of the antibodies described herein.
Selection can be by any of a number of methods well known to those of skill in the art. In one example, selection is by immunochromatography (e.g., using immunotubes, Maxisorp, Nunc) against the desired target, e.g., BoNT/G, BoNT/B, etc. In a related example, selection is against a BoNT protein in a surface plasmon resonance system (e.g., BIAcore, Pharmacia) either alone or in combination with an antibody that binds to an epitope specifically bound by one or more of the antibodies described herein. Selection can also be done using flow cytometry for yeast display libraries. Yeast display libraries are sequentially selected, first on BoNT/B1, then on other BoNT/B subtypes (BoNT/B2, B3 and B4) to obtain antibodies that bind with high affinity to all subtypes of BoNT/B. This can be repeated for other subtypes.
For phage display, analysis of binding can be simplified by including an amber codon between the antibody fragment gene and gene III. This makes it possible to easily switch between displayed and soluble antibody fragments simply by changing the host bacterial strain. When phage are grown in a supE suppresser strain of E. coli, the amber stop codon between the antibody gene and gene III is read as glutamine and the antibody fragment is displayed on the surface of the phage. When eluted phage are used to infect a non-suppressor strain, the amber codon is read as a stop codon and soluble antibody is secreted from the bacteria into the periplasm and culture media (Hoogenboom et al. (1991) Nucleic Acids Res., 19: 4133-4137). Binding of soluble scFv to antigen can be detected, e.g., by ELISA using a murine IgG monoclonal antibody (e.g., 9E10) which recognizes a C-terminal myc peptide tag on the scFv (Evan et al. (1985) Mol. Cell. Biol., 5: 3610-3616; Munro et al. (1986) Cell, 46: 291-300), e.g., followed by incubation with polyclonal anti-mouse Fc conjugated to a detectable label (e.g., horseradish peroxidase).
As indicated above, purification of the anti-BoNT antibody can be facilitated by cloning of the scFv gene into an expression vector (e.g., expression vector pUC119mycHIS) that results in the addition of the myc peptide tag followed by a hexahistidine tag at the C-terminal end of the scFv. The vector also preferably encodes the pectate lyase leader sequence that directs expression of the scFv into the bacterial periplasm where the leader sequence is cleaved. This makes it possible to harvest native properly folded scFv directly from the bacterial periplasm. The anti-BoNT antibody is then expressed and purified from the bacterial supernatant using immobilized metal affinity chromatography.
C) Measurement of Anti-BoNT Antibody Affinity for One or More BoNT Subtypes.
As explained above, selection for increased avidity involves measuring the affinity of an anti-BoNT antibody (e.g. a modified anti-BoNT antibody) for one or more targets of interest (e.g. BoNT/E subtype(s) or domains thereof. For example, the KD of a BoNT/F-binding antibody and the kinetics of binding to BoNT/F are determined in a BIAcore, a biosensor based on surface plasmon resonance. For this technique, antigen is coupled to a derivatized sensor chip capable of detecting changes in mass. When antibody is passed over the sensor chip, antibody binds to the antigen resulting in an increase in mass that is quantifiable. Measurement of the rate of association as a function of antibody concentration can be used to calculate the association rate constant (kon). After the association phase, buffer is passed over the chip and the rate of dissociation of antibody (koff) determined. Kon is typically measured in the range 1.0×102 to 5.0×106 M and koff in the range 1.0×10−1 to 1.0×10−6M. The equilibrium constant Kd is then calculated as koff/kon and thus is typically measured in the range 10−5 to 10−12M. Affinities measured in this manner usually correlate well with affinities measured in solution by fluorescence quench titration.
Phage display and selection generally results in the selection of higher affinity mutant scFvs (Marks et al. (1992) Bio/Technology, 10: 779-783; Hawkins et al. (1992) J. Mol. Biol. 226: 889-896; Riechmann et al. (1993) Biochemistry, 32: 8848-8855; Clackson et al. (1991) Nature, 352: 624-628), but probably does not result in the separation of mutants with less than a 6 fold difference in affinity (Riechmann et al. (1993) Biochemistry, 32: 8848-8855). Thus a rapid method can be used to estimate the relative affinities of mutant scFvs isolated after selection. Since increased affinity results primarily from a reduction in the koff, measurement of koff should identify higher affinity scFv. koff can be measured in the BIAcore on unpurified scFv in bacterial periplasm, since expression levels are high enough to give an adequate binding signal and koff is independent of concentration. The value of koff for periplasmic and purified scFv is typically in close agreement.
The present BoNT binding antibodies and fragments can be humanized or human engineered antibodies. As used herein, a humanized antibody, or antigen binding fragment thereof, is a recombinant polypeptide that comprises a portion of an antigen binding site from a non-human antibody and a portion of the framework and/or constant regions of a human antibody. A human engineered antibody or antibody fragment may be derived from a human or non-human (e.g., mouse) source that has been engineered by modifying (e.g., deleting, inserting, or substituting) amino acids at specific positions so as to alter certain biophysical properties or to reduce any detectable immunogenicity of the modified antibody in a human.
Humanized antibodies also encompass chimeric antibodies and CDR-grafted antibodies in which various regions may be derived from different species. Chimeric antibodies may be antibodies that include a non-human antibody variable region linked to a human constant region. Thus, in chimeric antibodies, the variable region is mostly non-human, and the constant region is human. Chimeric antibodies and methods for making them are described in Morrison, et al., Proc. Natl. Acad. Sci. USA, 81: 6841-6855 (1984), Boulianne, et al., Nature, 312: 643-646 (1984), and PCT Application Publication WO 86/01533. Although, they can be less immunogenic than a mouse monoclonal antibody, administrations of chimeric antibodies have been associated with human anti-mouse antibody responses (HAMA) to the non-human portion of the antibodies. Chimeric antibodies can also be produced by splicing the genes from a mouse antibody molecule of appropriate antigen-binding specificity together with genes from a human antibody molecule of appropriate biological activity, such as the ability to activate human complement and mediate ADCC. Morrison et al. (1984), Proc. Natl. Acad. Sci., 81: 6851; Neuberger et al. (1984), Nature, 312: 604. One example is the replacement of an Fc region with that of a different isotype.
CDR-grafted antibodies are antibodies that include the CDRs from a non-human “donor” antibody linked to the framework region from a human “recipient” antibody. Generally, CDR-grafted antibodies include more human antibody sequences than chimeric antibodies because they include both constant region sequences and variable region (framework) sequences from human antibodies. Thus, for example, a CDR-grafted humanized antibody may comprise a heavy chain that comprises a contiguous amino acid sequence (e.g., about 5 or more, 10 or more, or even 15 or more contiguous amino acid residues) from the framework region of a human antibody (e.g., FR-1, FR-2, or FR-3 of a human antibody) or, optionally, most or all of the entire framework region of a human antibody. CDR-grafted antibodies and methods for making them are described in, Jones et al., Nature, 321: 522-525 (1986), Riechmann et al., Nature, 332: 323-327 (1988), and Verhoeyen et al., Science, 239: 1534-1536 (1988)). Methods that can be used to produce humanized antibodies also are described in U.S. Pat. Nos. 4,816,567, 5,721,367, 5,837,243, and 6,180,377. CDR-grafted antibodies are considered less likely than chimeric antibodies to induce an immune reaction against non-human antibody portions. However, it has been reported that framework sequences from the donor antibodies are required for the binding affinity and/or specificity of the donor antibody, presumably because these framework sequences affect the folding of the antigen-binding portion of the donor antibody. Therefore, when donor, non-human CDR sequences are grafted onto unaltered human framework sequences, the resulting CDR-grafted antibody can exhibit, in some cases, loss of binding avidity relative to the original non-human donor antibody. See, e.g., Riechmann et al., Nature, 332: 323-327 (1988), and Verhoeyen et al., Science, 239: 1534-1536 (1988).
Human engineered antibodies include for example “veneered” antibodies and antibodies prepared using H
“Veneered” antibodies are non-human or humanized (e.g., chimeric or CDR-grafted antibodies) antibodies that have been engineered to replace certain solvent-exposed amino acid residues so as to further reduce their immunogenicity or enhance their function. As surface residues of a chimeric antibody are presumed to be less likely to affect proper antibody folding and more likely to elicit an immune reaction, veneering of a chimeric antibody can include, for instance, identifying solvent-exposed residues in the non-human framework region of a chimeric antibody and replacing at least one of them with the corresponding surface residues from a human framework region. Veneering can be accomplished by any suitable engineering technique, including the use of the above-described H
In a different approach, a recovery of binding avidity can be achieved by “de-humanizing” a CDR-grafted antibody. De-humanizing can include restoring residues from the donor antibody's framework regions to the CDR grafted antibody, thereby restoring proper folding. Similar “de-humanization” can be achieved by (i) including portions of the “donor” framework region in the “recipient” antibody or (ii) grafting portions of the “donor” antibody framework region into the recipient antibody (along with the grafted donor CDRs).
For a further discussion of antibodies, humanized antibodies, human engineered, and methods for their preparation, see Kontermann and Dubel, eds., Antibody Engineering, Springer, New York, N.Y., 2001.
The present antibodies and fragments encompass human antibodies, such as antibodies which bind BoNT polypeptides and are encoded by nucleic acid sequences which are naturally occurring somatic variants of human germline immunoglobulin nucleic acid sequence, and fragments, synthetic variants, derivatives and fusions thereof. Such antibodies may be produced by any method known in the art, such as through the use of transgenic mammals (such as transgenic mice) in which the native immunoglobulin repertoire has been replaced with human V-genes in the mammal chromosome. Such mammals appear to carry out VDJ recombination and somatic hypermutation of the human germline antibody genes in a normal fashion, thus producing high affinity antibodies with completely human sequences.
Human antibodies to target protein can also be produced using transgenic animals that have no endogenous immunoglobulin production and are engineered to contain human immunoglobulin loci. For example, WO 98/24893 discloses transgenic animals having a human Ig locus wherein the animals do not produce functional endogenous immunoglobulins due to the inactivation of endogenous heavy and light chain loci. WO 91/00906 also discloses transgenic non-primate mammalian hosts capable of mounting an immune response to an immunogen, wherein the antibodies have primate constant and/or variable regions, and wherein the endogenous immunoglobulin encoding loci are substituted or inactivated. WO 96/30498 and U.S. Pat. No. 6,091,001 disclose the use of the Cre/Lox system to modify the immunoglobulin locus in a mammal, such as to replace all or a portion of the constant or variable region to form a modified antibody molecule. WO 94/02602 discloses non-human mammalian hosts having inactivated endogenous Ig loci and functional human Ig loci. U.S. Pat. No. 5,939,598 discloses methods of making transgenic mice in which the mice lack endogenous heavy chains, and express an exogenous immunoglobulin locus comprising one or more xenogeneic constant regions. See also, U.S. Pat. Nos. 6,114,598, 6,657,103 and 6,833,268.
Using a transgenic animal described above, an immune response can be produced to a selected antigenic molecule, and antibody producing cells can be removed from the animal and used to produce hybridomas that secrete human monoclonal antibodies. Immunization protocols, adjuvants, and the like are known in the art, and are used in immunization of, for example, a transgenic mouse as described in WO 96/33735. The monoclonal antibodies can be tested for the ability to inhibit or neutralize the biological activity or physiological effect of the corresponding protein. Human monoclonal antibodies with specificity for the antigen used to immunize transgenic animals are also disclosed in WO 96/34096 and U.S. patent application no. 20030194404; and U.S. patent application no. 20030031667.
Additional transgenic animals useful to make monoclonal antibodies include the Medarex HuMAb-MOUSE®, described in U.S. Pat. No. 5,770,429 and Fishwild, et al. (Nat. Biotechnol. 14:845-851, 1996), which contains gene sequences from unrearranged human antibody genes that code for the heavy and light chains of human antibodies. Immunization of a HuMAb-MOUSE® enables the production of fully human monoclonal antibodies to the target protein.
Also, Ishida et al. (Cloning Stem Cells. 4:91-102, 2002) describes the TransChromo Mouse (TCMOUSE™) which comprises megabase-sized segments of human DNA and which incorporates the entire human immunoglobulin (hIg) loci. The TCMOUSE™ has a fully diverse repertoire of hIgs, including all the subclasses of IgGs (IgG1-G4). Immunization of the TC MOUSE™ with various human antigens produces antibody responses comprising human antibodies. See also Jakobovits et al., Proc. Natl. Acad. Sci. USA, 90:2551 (1993); Jakobovits et al., Nature, 362:255-258 (1993); Bruggermann et al., Year in Immunol., 7:33 (1993); and U.S. Pat. Nos. 5,591,669; 5,589,369; 5,545,807; and U.S Patent Publication Nos. 20020199213 and 20030092125, which describe methods for biasing the immune response of an animal to the desired epitope. Human antibodies may also be generated by in vitro activated B cells (see U.S. Pat. Nos. 5,567,610 and 5,229,275).
Human antibodies can also be generated through the in vitro screening of antibody display libraries. See Hoogenboom et al. (1991), J. Mol. Biol. 227: 381; and Marks et al. (1991), J. Mol. Biol. 222: 581. Various antibody-containing phage display libraries have been described and may be readily prepared. Libraries may contain a diversity of human antibody sequences, such as human Fab, Fv, and scFv fragments that may be screened against an appropriate target. Phage display libraries may comprise peptides or proteins other than antibodies which may be screened to identify selective binding agents of BoNT.
The development of technologies for making repertoires of recombinant human antibody genes, and the display of the encoded antibody fragments on the surface of filamentous bacteriophage, has provided a means for making human antibodies directly. The antibodies produced by phage technology are produced as antigen binding fragments-usually Fv or Fab fragments-in bacteria and thus lack effector functions. Effector functions can be introduced by one of two strategies: The fragments can be engineered either into complete antibodies for expression in mammalian cells, or into bispecific antibody fragments with a second binding site capable of triggering an effector function.
Methods for display of peptides on the surface of yeast and microbial cells have also been used to identify antigen specific antibodies. See, for example, U.S. Pat. No. 6,699,658. Antibody libraries may be attached to yeast proteins, such as agglutinin, effectively mimicking the cell surface display of antibodies by B cells in the immune system.
In addition to phage display methods, antibodies may be isolated using ribosome mRNA display methods and microbial cell display methods. Selection of polypeptide using ribosome display is described in Hanes et al., (Proc. Nat.l Acad. Sc.i USA, 94:4937-4942, 1997) and U.S. Pat. Nos. 5,643,768 and 5,658,754 issued to Kawasaki. Ribosome display is also useful for rapid large scale mutational analysis of antibodies. The selective mutagenesis approach also provides a method of producing antibodies with improved activities that can be selected using ribosomal display techniques.
Human BoNT-binding antibodies of the present disclosure may be produced in trioma cells. Genes encoding the antibodies are then cloned and expressed in other cells, particularly, nonhuman mammalian cells.
The general approach for producing human antibodies by trioma technology has been described by Ostberg et al. (1983) Hybridoma 2: 361-367, Ostberg, U.S. Pat. No. 4,634,664, and Engelman et al., U.S. Pat. No. 4,634,666. The antibody-producing cell lines obtained by this method are called triomas because they are descended from three cells; two human and one mouse. Triomas have been found to produce antibody more stably than ordinary hybridomas made from human cells.
Other approaches to antibody production include in vitro immunization of human blood. In this approach, human blood lymphocytes capable of producing human antibodies are produced. Human peripheral blood is collected from the patient and is treated to recover mononuclear cells. The suppressor T-cells then are removed and remaining cells are suspended in a tissue culture medium to which is added the antigen and autologous serum and, preferably, a nonspecific lymphocyte activator. The cells then are incubated for a period of time so that they produce the specific antibody desired. The cells then can be fused to human myeloma cells to immortalize the cell line, thereby to permit continuous production of antibody (see U.S. Pat. No. 4,716,111).
In another approach, mouse-human hybridomas which produce human anti-BoNT antibodies are prepared (see, e.g., U.S. Pat. No. 5,506,132). Other approaches include immunization of murines transformed to express human immunoglobulin genes, and phage display screening (Vaughan et al. supra.).
Sequence provided herein can be used to generate other antibody forms, including but not limited to nanobodies, UniBodies, and/or affibodies.
VHH and/or Nanobodies.
The Camelidae heavy chain antibodies are found as homodimers of a single heavy chain, dimerized via their constant regions. The variable domains of these camelidae heavy chain antibodies are referred to as VHH domains or VHH, and can be either used per se as nanobodies and/or as a starting point for obtaining nanobodies. Isolated VHH retain the ability to bind antigen with high specificity (see, e.g., Hamers-Casterman et al. (1993) Nature 363: 446-448). VHH domains, or nucleotide sequences encoding them, can be derived from antibodies raised in Camelidae species, for example in camel, dromedary, llama, alpaca and guanaco. Other species besides Camelidae (e.g, shark, pufferfish) can produce functional antigen-binding heavy chain antibodies, from which (nucleotide sequences encoding) such naturally occurring VHH can be obtained, e.g. using the methods described in U.S. Patent Publication US 2006/0211088.
Human proteins may be used in therapy primarily because they are not as likely to provoke an immune response when administered to a patient. Comparisons of camelid VHH with the VH domains of human antibodies reveals several key differences in the framework regions of the camelid VHH domain corresponding to the VH/VL interface of the human VH domains. Mutation of these human residues to VHH resembling residues has been performed to produce “camelized” human VH domains that retain antigen binding activity, yet have improved expression and solubility.
Libraries of single VH domains have also been derived for example from VH genes amplified from genomic DNA or from mRNA came from the spleens of immunized mice and expressed in E. coli (Ward et al. (1989) Nature 341: 544-546) and similar approaches can be performed using the VH domains and/or the VL domains described herein. The isolated single VH domains are called “dAbs” or domain antibodies. A “dAb” is an antibody single variable domain (VH or VL) polypeptide that specifically binds antigen. A “dAb” binds antigen independently of other V domains; however, as the term is used herein, a “dAb” can be present in a homo- or heteromultimer with other VH or VL domains where the other domains are not required for antigen binding by the dAb, i.e., where the dAb binds antigen independently of the additional VH or VL domains.
As described in U.S. Patent Publication No. 2006/0211088 methods are known for the cloning and direct screening of immunoglobulin sequences (including but not limited to multivalent polypeptides comprising: two or more variable domains—or antigen binding domains—and in particular VH domains or VHH domains; fragments of VL, VH or VHH domains, such as CDR regions, for example CDR3 regions; antigen-binding fragments of conventional 4-chain antibodies such as Fab fragments and scFv′s, heavy chain antibodies and domain antibodies; and in particular of VH sequences, and more in particular of VHH sequences) that can be used as part of and/or to construct such nanobodies.
Methods and procedures for the production of VHH/nanobodies can also be found for example in WO 94/04678, WO 96/34103, WO 97/49805, WO 97/49805 WO 94/25591, WO 00/43507 WO 01/90190, WO 03/025020, WO 04/062551, WO 04/041863, WO 04/041865, WO 04/041862, WO 04/041867, PCT/BE2004/000159, Hamers-Casterman et al. (1993) Nature 363: 446; Riechmann and Muyldermans (1999) J. Immunological Meth., 231: 25-38; Vu et al. (1997) Molecular Immunology, 34(16-17): 1121-1131; Nguyen et al. (2000) EMBO J., 19(5): 921-930; Arbabi Ghahroudi et al. (19997) FEBS Letters 414: 521-526; van der Linden et al. (2000) J. Immunological Meth., 240: 185-195; Muyldermans (2001) Rev. Molecular Biotechnology 74: 277-302; Nguyen et al. (2001) Adv. Immunol. 79:261, and the like, which are all incorporated herein by reference.
UniBodies.
UniBodies are generated by an antibody technology that produces a stable, smaller antibody format with an anticipated longer therapeutic window than certain small antibody formats. UniBodies may be produced from IgG4 antibodies by eliminating the hinge region of the antibody. Unlike the full size IgG4 antibody, the half molecule fragment is very stable and is termed a UniBody. Halving the IgG4 molecule left only one area on the UniBody that can bind to a target. Methods of producing UniBodies are described in detail in PCT Publication WO2007/059782, which is incorporated herein by reference in its entirety (see, also, Kolfschoten et al. (2007) Science 317: 1554-1557).
Affibodies.
Affibody molecules are class of affinity proteins based on a 58-amino acid residue protein domain, derived from one of the IgG-binding domains of staphylococcal protein A. This three helix bundle domain has been used as a scaffold for the construction of combinatorial phagemid libraries, from which affibody variants that target the desired molecules can be selected using phage display technology (see, e.g., Nord et al. (1997) Nat. Biotechnol. 15: 772-777; Ronmark et al. (2002) Eur. J. Biochem., 269: 2647-2655.). Details of affibodies and methods of production are known to those of skill (see, e.g., U.S. Pat. No. 5,831,012 which is incorporated herein by reference in its entirety).
The antibodies of the present disclosure encompass those that specifically bind to one or more epitopes recognized by antibodies described herein (as seen in
This can be ascertained by providing one or more isolated target BoNT polypeptide(s) (e.g. BoNT/B1 and/or BoNT/B2, or recombinant domains of said toxin, such as HC) attached to a solid support and assaying the ability of a test antibody to compete with, an antibody described herein for binding to the target BoNT peptide. Thus, immunoassays in a competitive binding format are preferably used for cross-reactivity determinations. For example, a BoNT/E and/or BoNT/B polypeptide may be immobilized to a solid support. Antibodies to be tested (e.g. generated by selection from a phage-display library) added to the assay compete with any antibody from clones as shown in
If the test antibody competes with one or more of the antibodies listed in
Cross-reactivity may be performed by using surface plasmon resonance in a BIAcore. In a BIAcore flow cell, the BoNT polypeptide(s) (e.g., BoNT/C and/or BoNT/F) are coupled to a sensor chip (e.g. CM5) as described in WO 09/008,916, disclosure of which is incorporated herein by reference. With a flow rate of 5 μl/min, a titration of 100 nM to 1 μM antibody is injected over the flow cell surface for about 5 minutes to determine an antibody concentration that results in near saturation of the surface. Epitope mapping or cross-reactivity is then evaluated using pairs of antibodies at concentrations resulting in near saturation and at least 100 relative units (RU) of antibody bound. The amount of antibody bound is determined for each member of a pair, and then the two antibodies are mixed together to give a final concentration equal to the concentration used for measurements of the individual antibodies. Antibodies recognizing different epitopes show an essentially additive increase in the RU bound when injected together, while antibodies recognizing identical epitopes show only a minimal increase in RU. Antibodies may be said to be cross-reactive if, when “injected” together they show an essentially additive increase (e.g., an increase by at least a factor of about 1.4, an increase by at least a factor of about 1.6, or an increase by at least a factor of about 1.8 or 2).
Cross-reactivity may also be determined by incubating a yeast displayed scFv with a BoNT domain polypeptide followed by incubation with an epitope-tagged scFv. Bound scFv is detected with an antibody recognizing the epitope tag and the level of BoNT domain display quantitated by incubation with anti-SV5 (see example 1).
Cross-reactivity at the desired epitopes can be ascertained by a number of other standard techniques (see, e.g., Geysen et al (1987) J. Immunol. Meth. 102, 259-274). This technique involves the synthesis of large numbers of overlapping BoNT peptides. The synthesized peptides are then screened against one or more of the prototypical antibodies (e.g., 4C10.1, 8DC1.2, etc.) and the characteristic epitopes specifically bound by these antibodies can be identified by binding specificity and affinity. The epitopes thus identified can be conveniently used for competitive assays as described herein to identify cross-reacting antibodies.
The peptides for epitope mapping can be conveniently prepared using “Multipin” peptide synthesis techniques (see, e.g., Geysen et al (1987) Science, 235: 1184-1190). Using the known sequence of one or more BoNT subtypes (see, e.g., Atassi et al. (1996) J. Prot. Chem., 7: 691-700 and references cited therein), overlapping BoNT polypeptide sequences can be synthesized individually in a sequential manner on plastic pins in an array of one or more 96-well microtest plate(s).
The procedure for epitope mapping using this multipin peptide system is described in U.S. Pat. No. 5,739,306. Briefly, the pins are first treated with a pre-coat buffer containing 2% bovine serum albumin and 0.1% Tween 20 in phosphate-buffered saline (PBS) for 1 hour at room temperature. Then the pins are then inserted into the individual wells of 96-well microtest plate containing the antibodies in the pre-coat buffer, e.g. at 2 μg/ml. The incubation is preferably for about 1 hour at room temperature. The pins are washed in PBST (e.g., 3 rinses for every 10 minutes), and then incubated in the wells of a 96-well microtest plate containing 100 of horse radish peroxidase (HRP)-conjugated goat anti-mouse IgG (Fc) (Jackson ImmunoResearch Laboratories) at a 1:4,000 dilution for 1 hour at room temperature. After the pins are washed as before, the pins are put into wells containing peroxidase substrate solution of diammonium 2,2′-azino-bis[3-ethylbenzthiazoline-b-sulfonate] (ABTS) and H2O2 (Kirkegaard & Perry Laboratories Inc., Gaithersburg, Md.) for 30 minutes at room temperature for color reaction. The plate is read at 405 nm by a plate reader (e.g., BioTek ELISA plate reader) against a background absorption wavelength of 492 nm. Wells showing color development indicate reactivity of the BoNT peptides in such wells with the test antibodies.
Preferred antibodies of the present disclosure act, individually or in combination, to neutralize (reduce or eliminate) the toxicity of botulinum neurotoxin type. Neutralization can be evaluated in vivo or in vitro. In vivo neutralization measurements simply involve measuring changes in the lethality (e.g., LD50 or other standard metric) due to a BoNT neurotoxin administration with the presence of one or more antibodies being tested for neutralizing activity. The neurotoxin can be directly administered to the test organism (e.g. mouse) or the organism can harbor a botulism infection (e.g., be infected with Clostridium botulinum). The antibody can be administered before, during, or after the injection of BoNT neurotoxin or infection of the test animal. A decrease in the rate of progression, or mortality rate indicates that the antibody(s) have neutralizing activity.
One suitable in vitro assay for neutralizing activity uses a hemidiaphragm preparation (Deshpande et al. (1995) Toxicon, 33: 551-557). Briefly, left and right phrenic nerve hemidiaphragm preparations are suspended in physiological solution and maintained at a constant temperature (e.g. 36° C.). The phrenic nerves are stimulated supramaximally (e.g. at 0.05 Hz with square waves of 0.2 ms duration). Isometric twitch tension is measured with a force displacement transducer (e.g., GrassModel FT03) connected to a chart recorder.
Purified antibodies are incubated with purified BoNT (e.g. BoNT/A1, BoNT/C, BoNT/F1, etc.) for 30 min at room temperature and then added to the tissue bath, resulting in a final antibody concentration of about 2.0×10−8 M and a final BoNT concentration of about 2.0×10−11 M. For each antibody studied, time to 50% twitch tension reduction is determined (e.g., three times for BoNT alone and three times for antibody plus BoNT). Differences between times to a given (arbitrary) percentage (e.g. 50%) twitch reduction are determined by standard statistical analyses (e.g. two-tailed t test) at standard levels of significance (e.g., a P value of <0.05 considered significant).
As explained above, the anti-BoNT antibodies of the present disclosure can be used for the in vivo or in vitro detection of BoNT toxin and thus, are useful in the diagnosis (e.g. confirmatory diagnosis) of botulism. The detection and/or quantification of BoNT in a biological sample obtained from an organism is indicative of a Clostridium botulinum infection of that organism.
The BoNT antigen can be quantified in a biological sample derived from a patient such as a cell, or a tissue sample derived from a patient. As used herein, a biological sample is a sample of biological tissue or fluid that contains a BoNT concentration that may be correlated with and indicative of a Clostridium botulinum infection. Preferred biological samples include blood, urine, saliva, and tissue biopsies.
Although the sample is typically taken from a human patient, the assays can be used to detect BoNT antigen in samples from mammals in general, such as dogs, cats, sheep, cattle and pigs, and most particularly primates such as humans, chimpanzees, gorillas, macaques, and baboons, and rodents such as mice, rats, and guinea pigs.
Tissue or fluid samples are isolated from a patient according to standard methods well known to those of skill in the art, most typically by biopsy or venipuncture. The sample is optionally pretreated as necessary by dilution in an appropriate buffer solution or concentrated, if desired. Any of a number of standard aqueous buffer solutions, employing one of a variety of buffers, such as phosphate, Tris, or the like, at physiological pH can be used.
A) Immunological Binding Assays
The BoNT polypeptide (e.g., BoNT/C, BoNT/F, etc.) can be detected in an immunoassay utilizing only one or more than one of the anti-BoNT antibodies of the present disclosure as a capture agent that specifically binds to the BoNT polypeptide.
As used herein, an immunoassay is an assay that utilizes only one or more than one antibody (e.g. one or more anti-BoNT/F antibodies listed in
The BoNT marker can be detected and quantified using any of a number of well recognized immunological binding assays. For example, the antibody of the present disclosure may be immobilized on a substrate (e.g. bead) and/or be the capture antibody in an ELISA. The detection step may take one of many formats known in the art, such as using a labeled secondary antibody or PCR amplification. Where PCR amplification is the method of detection, the antibody is conjugated to a nucleic acid, the antigen may optionally be first attached to a substrate, and the antibody is allowed to be bound to the antigen. The bound antibody-nucleic acid fusion then undergoes PCR amplification of the nucleic acid sequence attached to the antibody. The amplified sequences can in turn be detected via a fluorophore bound to the incorporated nucleotides. The amplified sequences can also be first hybridized to an array before fluorescence is measured to enable multiplexing. Multiplexing encompasses processing and detecting two or more samples and/or two or more analytes in parallel. Details of an assay using antibody-nucleic acid fusion may be found in US 20060141505, disclosure of which is incorporated by reference.
Single assay or multiplex assay can also take the form of an array where signal is detected only by electro-stimulation. In this format, the antibody of the present disclosure is conjugated to an electrochemiluminescent moiety and immobilized on an electrode. A signal (e.g. fluorescence) is emitted due to electrical stimulation at a particular electrode. Details of an assay using electrochemiluminescent moiety in an array may be found in US 20100140086, disclosure of which is incorporated by reference.
A fluorescent compound may be also added later to the assay for visualization by either Luminex type or other type of detection (see, e.g., U.S. Pat. Nos. 4,366,241; 4,376,110; 4,517,288; and 4,837,168, and the like). For a review of the general immunoassays, see also Methods in Cell Biology Volume 37: Antibodies in Cell Biology, Asai, ed. Academic Press, Inc. New York (1993); Basic and Clinical Immunology 7th Edition, Stites & Terr, eds. (1991)).
The immunoassays of the present disclosure can be performed in any of a number of configurations (see, e.g., those reviewed in Maggio (ed.) (1980) Enzyme Immunoassay CRC Press, Boca Raton, Fla.; Tijan (1985) “Practice and Theory of Enzyme Immunoassays,” Laboratory Techniques in Biochemistry and Molecular Biology, Elsevier Science Publishers B.V., Amsterdam; Harlow and Lane, supra; Chan (ed.) (1987) Immunoassay: A Practical Guide Academic Press, Orlando, Fla.; Price and Newman (eds.) (1991) Principles and Practice of Immunoassays Stockton Press, NY; and Ngo (ed.) (1988) Non isotopic Immunoassays Plenum Press, NY).
Immunoassays often utilize a labeling agent to specifically bind to and label the binding complex formed by the capture agent and the analyte (e.g., an anti-BoNT/F antibody/BoNT/F complex). The labeling agent can itself be one of the moieties comprising the antibody/analyte complex. Thus, for example, the labeling agent can be a labeled BoNT/F polypeptide or a labeled anti-BoNT/F antibody. Alternatively, the labeling agent is optionally a third moiety, such as another antibody, that specifically binds to the BoNT antibody, the BoNT peptide(s), the antibody/polypeptide complex, or to a modified capture group (e.g., biotin) which is covalently linked to BoNT polypeptide or to the anti-BoNT antibody.
The labeling agent encompasses an antibody that specifically binds to the anti-BoNT antibody. Such agents are well known to those of skill in the art, and most typically comprise labeled antibodies that specifically bind antibodies of the particular animal species from which the anti-BoNT antibody is derived (e.g., an anti-species antibody). Thus, for example, where the capture agent is a human derived BoNT/F antibody, the label agent may be a mouse anti-human IgG, i.e., an antibody specific to the constant region of the human antibody.
Other proteins capable of specifically binding immunoglobulin constant regions, such as streptococcal protein A or protein G are also used as the labeling agent. These proteins are normal constituents of the cell walls of streptococcal bacteria. They exhibit a strong non immunogenic reactivity with immunoglobulin constant regions from a variety of species (see generally Kronval, et al., (1973) J. Immunol., 111:1401-1406, and Akerstrom, et al., (1985) J. Immunol., 135:2589-2542, and the like).
Throughout the assays, incubation and/or washing steps may be required after each combination of reagents. Incubation steps can vary from about 5 seconds to several hours, preferably from about 5 minutes to about 24 hours. However, the incubation time will depend upon the assay format, analyte, volume of solution, concentrations, and the like. Usually, the assays are carried out at ambient temperature, although they can be conducted over a range of temperatures, such as 5° C. to 45° C.
1) Non Competitive Assay Formats.
Immunoassays for detecting BoNT neurotoxins (e.g. BoNT serotypes and/or subtypes) may be either competitive or noncompetitive. Noncompetitive immunoassays are assays in which the amount of captured analyte (in this case, BoNT polypeptide) is directly measured. In one preferred “sandwich” assay, for example, the capture agent (e.g., an anti-BoNT antibody) is bound directly or indirectly to a solid substrate where it is immobilized. These immobilized anti-BoNT antibodies capture BoNT polypeptide(s) present in a test sample (e.g., a blood sample). The BoNT polypeptide(s) thus immobilized are then bound by a labeling agent, e.g., an anti-BoNT antibody bearing a label. Alternatively, the second antibody may lack a label, but it may, in turn, be bound by a labeled third antibody specific to antibodies of the species from which the second antibody is derived. Free labeled antibody is washed away and the remaining bound labeled antibody is detected (e.g., using a gamma detector where the label is radioactive).
2) Competitive Assay Formats.
In competitive assays, the amount of analyte (e.g., BoNT) present in the sample is measured indirectly by measuring the amount of an added (exogenous) analyte displaced (or competed away) from a capture agent (e.g., anti-BoNT antibody) by the analyte present in the sample. For example, in one competitive assay, a known amount of BoNT is added to a test sample with an unquantified amount of BoNT, and the sample is contacted with a capture agent, e.g., an anti-BoNT antibody that specifically binds BoNT/F. The amount of added BoNT that binds to the anti-BoNT antibody is inversely proportional to the concentration of BoNT/F present in the test sample.
The anti-BoNT antibody can be immobilized on a solid substrate. The amount of BoNT bound to the anti-BoNT antibody is determined either by measuring the amount of BoNT present in a BoNT-anti-BoNT antibody complex, or alternatively by measuring the amount of remaining uncomplexed BoNT.
B) Reduction of Non Specific Binding.
One of skill will appreciate that it is often desirable to reduce non specific binding in immunoassays and during analyte purification. Where the assay involves, for example BoNT/E polypeptide(s), BoNT/E-binding antibody, or other capture agent(s) immobilized on a solid substrate, it is desirable to minimize the amount of non specific binding to the substrate. Means of reducing such non specific binding are well known to those of skill in the art. Typically, this involves coating the substrate with a proteinaceous composition. In particular, protein compositions such as bovine serum albumin (BSA), nonfat powdered milk, and gelatin are widely used.
C) Substrates.
As mentioned above, depending upon the assay, various components, including the BoNT polypeptide(s), anti-BoNT antibodies, etc., are optionally bound to a solid surface. Many methods for immobilizing biomolecules to a variety of solid surfaces are known in the art. For instance, the solid surface may be a membrane (e.g., nitrocellulose), a microtiter dish (e.g., PVC, polypropylene, or polystyrene), a test tube (glass or plastic), a dipstick (e.g., glass, PVC, polypropylene, polystyrene, latex, and the like), a microcentrifuge tube, or a glass, silica, plastic, metallic or polymer bead. The desired component may be covalently bound, or noncovalently attached through nonspecific bonding.
A wide variety of organic and inorganic polymers, both natural and synthetic may be employed as the material for the solid surface. Illustrative polymers include polyethylene, polypropylene, poly(4-methylbutene), polystyrene, polymethacrylate, poly(ethylene terephthalate), rayon, nylon, poly(vinyl butyrate), polyvinylidene difluoride (PVDF), silicones, polyformaldehyde, cellulose, cellulose acetate, nitrocellulose, and the like. Other materials which may be employed include paper, glasses, ceramics, metals, metalloids, semiconductive materials, cements or the like. In addition, substances that form gels, such as proteins (e.g., gelatins), lipopolysaccharides, silicates, agarose and polyacrylamides can be used. Polymers which form several aqueous phases, such as dextrans, polyalkylene glycols or surfactants, such as phospholipids, long chain (12-24 carbon atoms) alkyl ammonium salts and the like are also suitable. Where the solid surface is porous, various pore sizes may be employed depending upon the nature of the system.
In preparing the surface, a plurality of different materials may be employed, e.g., as laminates, to obtain various properties. For example, protein coatings, such as gelatin can be used to avoid non specific binding, simplify covalent conjugation, and enhance signal detection or the like.
If covalent bonding between a compound and the surface is desired, the surface will usually be polyfunctional or be capable of being polyfunctionalized. Functional groups which may be present on the surface and used for linking can include carboxylic acids, aldehydes, amino groups, cyano groups, ethylenic groups, hydroxyl groups, mercapto groups and the like. The manner of linking a wide variety of compounds to various surfaces is well known and is amply illustrated in the literature. See, for example, Immobilized Enzymes, Ichiro Chibata, Halsted Press, New York, 1978, and Cuatrecasas, (1970) J. Biol. Chem. 245 3059.
In addition to covalent bonding, various methods for noncovalently binding an assay component can be used. Noncovalent binding is typically nonspecific absorption of a compound to the surface. Typically, the surface is blocked with a second compound to prevent nonspecific binding of labeled assay components. Alternatively, the surface is designed such that it nonspecifically binds one component but does not significantly bind another. For example, a surface bearing a lectin such as concanavalin A will bind a carbohydrate containing compound but not a labeled protein that lacks glycosylation. Various solid surfaces for use in noncovalent attachment of assay components are reviewed in U.S. Pat. Nos. 4,447,576 and 4,254,082, which is incorporated herein by reference.
D) Other Assay Formats
BoNT polypeptides or anti-BoNT antibodies (e.g. BoNT neutralizing antibodies) can also be detected and quantified by any of a number of other means well known to those of skill in the art. These include analytic biochemical methods such as spectrophotometry, radiography, electrophoresis, capillary electrophoresis, high performance liquid chromatography (HPLC), thin layer chromatography (TLC), hyperdiffusion chromatography, and the like, and various immunological methods such as fluid or gel precipitin reactions, immunodiffusion (single or double), immunoelectrophoresis, radioimmunoassays (RIAs), enzyme-linked immunosorbent assays (ELISAs), immunofluorescent assays, and the like.
Western blot analysis and related methods can also be used to detect and quantify the presence of BoNT polypeptides in a sample. The technique generally comprises separating sample products by gel electrophoresis on the basis of molecular weight, transferring the separated products to a suitable solid support, (such as a nitrocellulose filter, a nylon filter, or derivatized nylon filter), and incubating the sample with the antibodies that specifically bind either the BoNT polypeptide. The antibodies specifically bind to the biological agent of interest on the solid support. These antibodies are directly labeled or alternatively are subsequently detected using labeled antibodies (e.g., labeled sheep anti-human antibodies where the antibody to a marker gene is a human antibody) which specifically bind to the antibody which binds the BoNT polypeptide.
Other assay formats include liposome immunoassays (LIAs), which use liposomes designed to bind specific molecules (e.g., antibodies) and release encapsulated reagents or markers. The released chemicals are then detected according to standard techniques (see, Monroe et al., (1986) Amer. Clin. Prod. Rev. 5:34-41).
E) Labeling of Anti-BoNT Antibodies.
Anti-BoNT antibodies can be labeled by any of a number of methods known to those of skill in the art. Thus, for example, the labeling agent can be, e.g., a monoclonal antibody, a polyclonal antibody, a protein or complex such as those described herein, or a polymer such as an affinity matrix, carbohydrate or lipid. Detection proceeds by any known method, including immunoblotting, western analysis, gel-mobility shift assays, tracking of radioactive or bioluminescent markers, nuclear magnetic resonance, electron paramagnetic resonance, stopped-flow spectroscopy, column chromatography, capillary electrophoresis, or other methods which track a molecule based upon an alteration in size and/or charge. The detectable group can be any material having a detectable physical or chemical property. Such detectable labels have been well-developed in the field of immunoassays and, in general, any label useful in such methods can be applied in the various embodiments of the present disclosure. Thus, a label is any composition detectable by spectroscopic, photochemical, biochemical, immunochemical, electrical, optical or chemical means. Useful labels in the present disclosure include magnetic beads (e.g. Dynabeads™), fluorescent dyes (e.g., fluorescein isothiocyanate, Texas red, rhodamine, Alexa fluor dyes and the like), radiolabels (e.g., 3H, 125I, 35S, 14C, or 32P), enzymes (e.g., LacZ, CAT, horse radish peroxidase, luciferase, alkaline phosphatase and others, commonly used as detectable enzymes, either as marker gene products or in an ELISA), and colorimetric labels such as colloidal gold or colored glass or plastic (e.g. polystyrene, polypropylene, latex, etc.) beads. For example, an antibody can include a fluorescent label, a chemiluminescent label, a radiolabel, a chromogenic label, or other suitable label.
The label may be coupled directly or indirectly to the desired component of the assay according to methods well known in the art. As indicated above, a wide variety of labels may be used, with the choice of label depending on the sensitivity required, ease of conjugation of the compound, stability requirements, available instrumentation, and disposal provisions.
Non radioactive labels are often attached by indirect means. Generally, a ligand molecule (e.g., biotin) is covalently bound to the molecule. The ligand then binds to an anti-ligand (e.g., streptavidin) molecule which is either inherently detectable or covalently bound to a signal system, such as a detectable enzyme, a fluorescent compound, or a chemiluminescent compound. A number of ligands and anti-ligands can be used. Where a ligand has a natural anti-ligand, for example, biotin, thyroxine, and cortisol, it can be used in conjunction with the labeled, naturally occurring anti-ligands. Alternatively, any haptenic or antigenic compound can be used in combination with an antibody.
The molecules can also be conjugated directly to signal generating compounds, e.g., by conjugation with an enzyme or fluorophore. Enzymes of interest as labels will primarily be hydrolases, particularly phosphatases, esterases and glycosidases, or oxidoreductases, particularly peroxidases. Fluorescent compounds include fluorescein and its derivatives, rhodamine and its derivatives, dansyl, umbelliferone, etc. Chemiluminescent compounds include luciferin, and 2,3-dihydrophthalazinediones, e.g., luminol. For a review of various labeling or signal producing systems which may be used, see, U.S. Pat. No. 4,391,904, which is incorporated herein by reference.
Means of detecting labels are well known to those of skill in the art. Thus, for example, where the label is a radioactive label, means for detection include a scintillation counter or photographic film as in autoradiography. Where the label is a fluorescent label, it may be detected by exciting the fluorochrome with the appropriate wavelength of light and detecting the resulting fluorescence, e.g., by microscopy, visual inspection, via photographic film, by the use of electronic detectors such as charge coupled devices (CCDs) or photomultipliers and the like. Similarly, enzymatic labels may be detected by providing appropriate substrates for the enzyme and detecting the resulting reaction product. Finally, simple colorimetric labels may be detected simply by observing the color associated with the label. Thus, in various dipstick assays, conjugated gold often appears pink, while various conjugated beads appear the color of the bead.
Some assay formats do not require the use of labeled components. For instance, agglutination assays can be used to detect the presence of BoNT peptides. In this case, antigen-coated particles are agglutinated by samples comprising the target antibodies. In this format, none of the components need be labeled and the presence of the target antibody is detected by simple visual inspection.
The BoNT-binding antibodies of this disclosure are useful in preventing or mitigating the progression of botulism produced, e.g., by endogenous disease processes or by chemical/biological warfare agents. Typically compositions containing one, two, or more different antibodies can be provided as a pharmaceutical composition and administered to a mammal (e.g., to a human) in need thereof.
As disclosed herein, particularly efficient neutralization of a botulism neurotoxin (BoNT) can be achieved by the use of antibodies that bind two or more BoNT subtypes/serotypes/mosaics with high affinity. This can be accomplished by using one, two or more different antibodies. Where there is more than one type of antibody, each can be directed against a different subtype. One or more of the antibodies can also be cross-reactive. Cross-reactive antibodies can bind two or more BoNT serotypes/subtypes (e.g., BoNT/CD, BoNT/D, BoNT/DC, BoNT/G etc.) with high affinity.
Different neutralizing antibodies when combined, exhibit a potency that is increased dramatically. This increase makes it possible to generate a botulinum antibody composition of the required potency for therapeutic use. Compositions comprising at least two, at least three, or more high affinity antibodies that bind overlapping or non-overlapping epitopes on the BoNT are contemplated herein.
Compositions contemplated herein may contain two, three, or more different antibodies selected from antibodies of the present disclosure (e.g. any of the clones as shown in
The subject composition encompasses compositions that specifically bind to one or more serotypes/subtypes/mosaics. The composition can contain one or more antibodies that are cross-reactive. The composition may also contain any first combination of antibodies described above that specifically bind to one serotype together with a second combination of antibodies that specifically neutralizes a different serotype. The subject composition may contain multiple combinations such that that composition may bind and/or neturalize two, three, or more serotypes/subtypes (e.g. BoNT/CD, BoNT/D, BoNT/DC, etc.).
A composition that neutralizes multiple serotypes may include any of the combinations described above or one or more of the antibodies disclosed in Tables 1-8 and/or
Where combinations of antibodies are disclosed herein, such combinations can be provided in a single formulation or can be provided as separate formulations in a kit, where the separate formulations may contain a single antibody or two antibodies. Such separate formulations of a kit may be combined prior to administration or administered by separate injection.
The anti-BoNT antibodies provided by the present disclosure are useful for parenteral, topical, oral, or local administration, such as by aerosol or transdermally, for prophylactic and/or therapeutic treatment. The pharmaceutical compositions can be administered in a variety of unit dosage forms depending upon the method of administration. For example, unit dosage forms suitable for oral administration include powder, tablets, pills, capsules and lozenges. The antibodies comprising the pharmaceutical compositions of the present disclosure, when administered orally, are preferably protected from digestion. This is typically accomplished either by complexing the antibodies with a composition to render them resistant to acidic and enzymatic hydrolysis or by packaging the antibodies in an appropriately resistant carrier such as a liposome. Means of protecting proteins from digestion are well known in the art.
The pharmaceutical compositions of the present disclosure are particularly useful for parenteral administration, such as intravenous administration or administration into a body cavity or lumen of an organ. The compositions for administration can comprise a solution of one or more anti-BoNT antibody dissolved in a pharmaceutically acceptable carrier, which may be an aqueous carrier. A variety of aqueous carriers can be used, e.g., buffered saline and the like.
Non-aqueous pharmaceutically acceptable carriers (excipients) are known to those of skill in the art. Such excipients can comprise any substance that is biocompatible and liquid or soft enough at the subject's body temperature to release the active agent(s) (e.g., Anti-BoNT antibodies) into the subject's bloodstream at a desired rate. Non-aqueous carriers are usually hydrophobic and commonly organic, e.g., an oil or fat of vegetable, animal, mineral or synthetic origin or derivation. The carrier may include at least one chemical moiety of the kind that typifies “fatty” compounds, e.g., fatty acids, alcohols, esters, etc., i.e., a hydrocarbon chain, an ester linkage, or both. “Fatty” acids in this context include, but are not limited to, acetic, propionic and butyric acids through straight- or branched-chain organic acids containing up to 30 or more carbon atoms. The non-aqueous carrier may be immiscible in water and/or soluble in the substances commonly known as fat solvents. The non-aqueous carrier can correspond to a reaction product of a “fatty” compound or compounds with a hydroxy compound, e.g., a mono-hydric, di-hydric, trihydric or other polyhydric alcohol, e.g., glycerol, propanediol, lauryl alcohol, polyethylene or -propylene glycol, etc. These compounds include, but are not limited to, the fat-soluble vitamins, e.g., tocopherols and their esters, e.g., acetates sometimes produced to stabilize tocopherols. Sometimes, for economic reasons, the carrier can comprise a natural, unmodified vegetable oil such as sesame oil, soybean oil, peanut oil, palm oil, or an unmodified fat. Alternatively the vegetable oil or fat may be modified by hydrogenation or other chemical means which is compatible with the present disclosure. The appropriate use of hydrophobic substances prepared by synthetic means is also envisioned. Non-aqueous excipient compositions can also comprise, in addition to a biocompatible oil, an “antihydration agent” which term as used herein means a substance that retards hydration of the active agent(s) and/or the biocompatible oil or fat and thereby further decreases and/or stabilizes the rate of release of the active agent(s) from that composition following administration to an animal (e.g. human). A great variety of non-toxic antihydration agents are known. By way of example there are “gelling” agents that, when dispersed, and in some cases heated to dissolve them in the oil, give the body of oil greater visco-elasticity (and therefore greater structural stability) and thereby slow down penetration of the oil by body fluids.
Illustrative antihydration agents include various polyvalent metal salts or complexes of organic acids, for instance fatty acids having from about 8 or 10 to about 20 or 22 carbon atoms, e.g. aluminum, zinc, magnesium or calcium salts of lauric acid, palmitic acid, stearic acid and the like. Such salts can be mono-, di- or tri-substituted, depending on the valence of the metal and the degree of oxidation of the metal by the acid. Of common usage are the aluminum salts of such fatty acids. Aluminum monostearate and distearate are frequently used anti-hydration agents. Others that are useful include aluminum tristearate, calcium mono- and distearate, magnesium mono- and distearate and the corresponding palmitates, laurates and the like. The concentration of such an antihydration agent, based on the weight of the oil plus that agent, may be between about 1% and about 10% (most typically between about 2% and about 5%), although other concentrations may be suitable in some cases.
The various solutions are sterile and generally free of undesirable matter. These compositions may be sterilized by conventional, well known sterilization techniques. The compositions may contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions such as pH adjusting and buffering agents, toxicity adjusting agents and the like, for example, sodium acetate, sodium chloride, potassium chloride, calcium chloride, sodium lactate and the like. The concentration of anti-BoNT antibody in these formulations can vary widely, and will be selected primarily based on fluid volumes, viscosities, body weight and the like in accordance with the particular mode of administration selected and the patient's needs. In some instances, the solutions may be stored in lyophilized or frozen form. Examples of suitable anti-BoNT antibody formulations are described in WO 2011/028961.
Thus, a typical pharmaceutical composition for intravenous administration would be about 0.1 to 10 mg per patient per day. Dosages from about 1 mg up to about 200 mg per patient per day can be used. Methods for preparing parenterally administrable compositions will be known or apparent to those skilled in the art and are described in more detail in such publications as Remington's Pharmaceutical Science, 15th ed., Mack Publishing Company, Easton, Pa. (1980).
The compositions containing the anti-BoNT antibodies of the present disclosure or a cocktail thereof can be administered for therapeutic and/or prophylactic treatments. Preferred pharmaceutical compositions are administered in a dosage sufficient to neutralize (mitigate or eliminate) the BoNT toxin(s) (i.e., reduce or eliminate a symptom of BoNT poisoning (botulism)). An amount adequate to accomplish this is defined as a “therapeutically effective dose.” Amounts effective for this use will depend upon the severity of the disease and the general state of the patient's health.
Single or multiple administrations of the compositions may be administered depending on the dosage and frequency as required and tolerated by the patient. In any event, the composition should provide a sufficient quantity of the antibodies of the present disclosure to effectively treat the patient.
The present disclosure thus provides a method of neutralizing a Botulinum neurotoxin in an individual (e.g., a human; or a non-human mammal), the method generally involving administering to the individual an effective amount of a subject anti-BoNT antibody, or an effective amount of a subject composition comprising a subject anti-BoNT antibody. The treatments essentially comprise administering to the poisoned organism (e.g. human or non-human mammal) a quantity of one or more neutralizing antibodies sufficient to neutralize (e.g. mitigate or eliminate) symptoms of BoNT poisoning. Administering the antibody, or the composition comprising the antibody, provides for neutralization of Botulinum neurotoxin present in the individual. The BoNT poisoning can be due to ingestion of contaminated food products (food botulism), can result from an anaerobic wound infection (wound botulism), or can result from an act of biological warfare or bioterrorism.
The present disclosure also provides methods of reducing the likelihood that an individual at risk of exposure to Botulinum neurotoxin will experience symptoms of Botulinum neurotoxin poisoning following exposure to the Botulinum neurotoxin (e.g., where the exposure is via inhalation, via ingestion, via a wound infection, or via another route/mode of exposure). Administration of a subject antibody or subject composition reduces the likelihood that the individual will experience symptoms of Botulinum neurotoxin poisoning. Thus, e.g., a subject anti-BoNT antibody, or a subject composition comprising a subject anti-BoNT antibody, can be administered to an individual before the individual has Botulinum neurotoxin poisoning, e.g., before a BoNT is present in the individual. For example, a subject anti-BoNT antibody, or a subject composition comprising a subject anti-BoNT antibody, can be administered to an individual who is at risk of BoNT exposure, e.g., an individual who is at greater risk than the general population of experiencing Botulinum neurotoxin exposure and poisoning. Such individuals include, e.g., military personnel, e.g., military personnel in a combat setting; personnel involved in investigation or clean up of a site suspected of involving Botulinum neurotoxin exposure (e.g., hazardous materials (“hazmat”) personnel) and other individuals who are at risk of Botulinum neurotoxin exposure, either accidental or intentional.
Kits for the treatment of botulism or for the detection/confirmation of a Clostridium botulinum infection are also provided. Kits will typically comprise one or more anti-BoNT antibodies (e.g., anti-BoNT antibodies in a composition for pharmaceutical use). For diagnostic purposes, the antibody(s) can optionally be labeled. In addition the kits will typically include instructional materials disclosing means of use anti-BoNT antibodies in the treatment of symptoms of botulism. The kits may also include additional components to facilitate the particular application for which the kit is designed. Thus, for example, where a kit contains one or more anti-BoNT antibodies for detection of diagnosis of BoNT subtype, the antibody can be labeled, and the kit can additionally contain means of detecting the label (e.g. enzyme substrates for enzymatic labels, filter sets to detect fluorescent labels, appropriate secondary labels such as a sheep anti-human antibody, or the like). The kits may additionally include buffers and other reagents routinely used for the practice of a particular method. Such kits and appropriate contents are well known to those of skill in the art.
Kits provided for the treatment of botulism may contain one or more anti-BoNT antibodies. The antibodies can be provided separately or mixed together. Typically the antibodies will be provided in a sterile pharmacologically acceptable excipient. The antibodies can also be provided pre-loaded into a delivery device (e.g., a disposable syringe).
The kits can optionally include instructional materials teaching the use of the antibodies, recommended dosages, contraindications, and the like.
The following examples are offered to illustrate, but not to limit any embodiments provided by the present disclosure.
The use of yeast display to generate and affinity or specificity mature antibodies from immunized humans or mice is reported herein. Repertoires of 6 human donor or 13 immunized mice antibody variable genes were displayed as single chain Fv (scFv) on the surface of yeast and a total of 175 scFv leads (17 specific for BoNT/A LC, 3 for BoNT/A HC, 37 for BoNT/B LC, 16 for BoNT/B HC, 52 for BoNT/C, BoNT/D, BoNT/DC and BoNT/CD, 37 for BoNT/F, 13 for BoNT/G) isolated, engineered and characterized. These scFvs were epitopically diverse, binding one or more of the three different BoNT functional domains of each serotype with an average KD in the low nanomolar to picomolar range. The converted IgG antibodies from some of those scFv leads bound multiple subtypes of BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, BoNT/G and should prove to be useful for the development of sensitive and specific diagnostics or potent therapeutics for botulism either in human or in animals.
Primary human library construction in pYD2 vector
Light chain shuffled human library construction in pYD2 vector
TCCTCA-3′
TTCA-3′
CCTCA-3
CCTCA-3
Underlined region anneals to JH gene, bolded sequence is the NcoI restriction site
Primers for Mouse scfv Library Construction with pYD4 Vector
For VH gene amplification from pYD2 vector
As an example for toxin epitope mapping for selected antibodies, BoNT/B domains are subcloned in pYD2 vector and expressed on the yeast surface. The following primers are used for PCR amplification of each domain before they were subcloned into pYD2 vector. Each underlined segment corresponds to the DNA sequence of each BoNT/B toxin domain. Similar primers with the underlined DNA sequence changed to match the sequence of other BoNT serotypes (e.g, BoNT/C, BoNT/D, BoNT/F, BoNT/G, etc) could be used to get their toxin domain expressed on the yeast surface. These yeast displayed toxin domains could be used for epitope mapping the selected antibodies.
TG-3′
Unique linker sequence between VH and VL with designed cutting sites in pYD4 vector
The sequence of HA tag (underlined) between Aga2 linker and VH in pYD4 vector
TATCCATACGATGTTCCTGACTATGCAGCTAGCGGTGCCATGGCAC
Yeast strain Saccharomyces cerevisiae EBY100 (GAL1-AGA1TURA3 ura3-52 trp1 leu2Δ1 his3A200 pep4::HIS3 prb1Δ1.6R can1) was maintained in YPD medium (1% yeast extract, 2% peptone, 2% dextrose) (Current Protocols in Molecular Biology, John Wiley and Sons, Chapter 13.1.2). EBY100 transformed with expression vector pYD2 (Razai A et al. (2005) J. Mol. Biol. 351:158-169) was selected on SD-CAA medium (0.7% yeast nitrogen base, 0.1M Sodium phosphate, 0.5% casamino acids, 2% dextrose, 0.006% Leucine). ScFv yeast surface display was induced by transferring yeast cultures from SD-CAA to SG-CAA medium (identical to SD-CAA medium except the glucose was replaced by galactose) and growing at 18° C. for 24˜48 hr as described previously (Feldhaus, M J et al. (2003) Nature Biotechnol. 21:163-170). Bacteria strain E. coli DH5α, (K12, Δ(lac-pro), supE, thi, hsdD5/F′ traD36, proA+B+, lacIq, lacZΔM15) was used for cloning and preparation of plasmid DNA. Pure or Crude BoNT/A1 (Hall hyper), BoNT/A2 (FRI-H1A2), BoNT/B1, BoNT/B2, BoNT/B3, BoNT/B4, BoNT/C1, BoNT/CD, BoNT/DC, BoNT/D, BoNT/F1, BoNT/F6, BoNT/G were either purchased from Metabiologics (Madison, Wis.) or purified from their respective strains by researchers at USARMIID. Mouse anti-SV5 and anti-myc 9E10 antibody and BoNT/A antibodies 7C1 and 9D8 were purified from hybridoma supernatant using Protein G and directly labeled with Alexa-488 or Alexa-647 using a kit provided by the manufacturer (Molecular Probes). Other recombinant human antibodies (Razai A et al. (2005) J. Mol. Biol. 351:158-169; Nowakowski A et al. (2002) Proc. Natl. Acad. Sci. USA 99:11346-11350; Kalb S R et al. International Journal of Mass Spectrometry 278:101-108; Kalb S R et al. PLoS ONE 4(4): e5355. doi:10.1371/journal.pone.0005355; Lou J. et al (2010) Protein Engineering, Design & Selection. 23(4):311-319) specific for BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F or BoNT/G were prepared from stable cell line production of Chinese hamster ovary cells (CHO) supernatants as described before ((Razai A et al. (2005) J. Mol. Biol. 351:158-169; Nowakowski A et al. (2002) Proc. Natl. Acad. Sci. USA 99:11346-11350). For flow cytometry (FACS), purified human or mouse IgGs were directly labeled with either Alexa-647 or Alexa-488 using a kit provided by the manufacturer (Molecular Probes).
Immune scFv Yeast Antibody Library Generation in Bacteria and in Yeast
Six scFv yeast libraries were constructed in pYD2 vector using V-genes isolated from human volunteers immunized with pentavalent toxoid, and thirteen scFv yeast libraries were constructed in pYD4 vector with V-genes from mice immunized either with purified recombinant toxin domain (ALC, BLC, FHC) or with monovalent toxin of BoNT/F. For human scFv library construction, briefly, approximately 25 ml of blood was drawn 7 days after immunization and PBLs isolated using Lymphoprep tubes (Axis-Shield PoC AS, Norway). Blood was drawn after obtaining informed consent and under a protocol reviewed and approved by the USAMRIID and UCSF IRBs. Total RNA was isolated from PBLs using an RNAgents® kit (Promega). cDNA was synthesized from total RNA by using AMV reverse transcriptase (Invitrogen) and HuIgG1-4-C1FOR, HuCK1FOR primers (Marks, J D et al. (1991) J Mol Biol 222:581-97; Amersdorfer P et al. (2002) Vaccine. 20: 1640-1648). VH and VK gene fragments were amplified by PCR from cDNA by using Pfu polymerase (Stratagene) and a mixture of HuVH1-6BACK, HuVH2bBACK, HuVH5bBACK, HuVH7aBACK and HuJH1-5FOR mix primers for the VH gene and HuVK1-6BACK, HuVK2aBACK, HuVK2bBACK and HuJK1-5FOR primers or the Vk gene (Marks, J D et al. (1991) Eur. J. Immunol. 21:985-991). scFv linker DNA template for pYD2 vector was prepared as previously described (Marks, J D et al. (1991) J Mol Biol 222:581-97), but the unique linker with cloning sites designed was synthesized for pYD4 vector, and pYD4 vector was used for construction of 13 mouse immune libraries and for individual clone affinity or specificity maturation. The whole library construction process was very similar to the ones used for human library, except total RNA was prepared from mouse spleen instead of human PBL, and all the primers used are those for mouse V-gene amplification (described in the Material and Methods section with a name start as “MM”, e.g, MMVH1pYD4Gap5′). PCR amplified VH or VK DNA fragments were gel purified, isolated from the gel using GENECLEAN® Turbo (Q.BIOgene). Human scFv gene repertoires were constructed by using PCR to splice together the VH and VK gene repertoires with scFv linker DNA (Marks, J D et al. (1991) J Mol Biol 222:581-97). The scFv genes were gel purified, isolated from the gel and reamplified using HuVHBACK and HuJkFOR primer mixes which appended NcoI and NotI site restriction sites (Marks, J D et al. (1991) J Mol Biol 222:581-97). scFv genes were digested with NcoI an NotI and ligated into NcoI-NotI digested pYD2 (Razai A et al. (2005) J. Mol. Biol. 351:158-169). For pYD2 gap-repair transformation, scFv gene repertoires were amplified from the ligation mixtures using primers GAP5 and GAP3 (Razai A et al. (2005) J. Mol. Biol. 351:158-169) to append homologous overlaps with pYD2. Appended scFv PCR products were ethanol precipitated, combined with NcoI-NotI digested pYD2 and used to transform EBY100 (Gietz, R D and Schiestl, R H (1991) Yeast 7:253-263; Orr-Weaver, T L et al. (1983) Proc. Natl. Acad. Sci. USA 80:4417-4421). The mouse scFv gene repertoires with the unique linker and HA tag at the N-terminal of scFv were prepared by two step sequential cloning into pYD4 vector, and the libraries were kept both in bacterial and in yeast. After PCR amplification of the mouse V-gene using the mouse primers with Gap tail, the 5′ end of the amplified VL gene repertoire were cut with BamHI or BssHII, and the 3′ end of the same VL gene repertoire cut with Not I, Apa I or BstBI, then the double cut VL genes were ligated into pYD4 vector which has been cut with the same sets of enzymes. The ligation product was used to transform E. coli DH5 cc to get a library with VL-only in pYD4 vector, this VL gene library is kept in bacteria. Alternatively the VL gene repertoire with the gap tail was used to transform yeast EBY100 directly to get a VL-only library in pYD4 vector, this library is created in yeast. The second cloning step is to insert the VH gene repertoire into this VL-only library. The VH gene repertoire is inserted into this VL library either by gap-repair or by cut and ligation. Using gap-repair method, the PCR amplified VH gene repertoire is mixed with the above mentioned VL library plasmids which was cut with Nco I and Sal I first, then the mixture used to transform yeast strain EBY 100 as described before (Gietz, R D and Schiestl, R H (1991) Yeast 7:253-263). So, the scFv display library is prepared and kept in yeast directly. Alternatively, based on the unique design, the VH gene repertoire was cut with NheI or NcoI at the 5′ end, and with Afl II or BspE1 at the 3′ end of the same VH, this double cut VH gene was then ligated into the VL-only library prepared with same double cutting method. The ligation product was used to transform E. coli, and a scFv yeast display library was created and kept in bacteria, milligram quantities of plasmid DNA covering the whole library was easily prepared from those transformed bacteria. These plasmid DNA was then used to transform yeast strain EBY100 to get a library in yeast. Transformed yeast were cultured and subcultured in SD-CAA and library size calculated by serially diluting and plating the transformed culture on SD-CAA plates. Final library size was calculated as the product of the number of transformants and the percentage of clones with full length scFv insert as determined by PCR (Razai A et al. (2005) J. Mol. Biol. 351:158-169). Library sizes of 4.1 to 25.7×107 were obtained for the 13 murine scFv libraries.
Selection and Characterization of scFv Antibodies for BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F or BoNT/G
For antibody selection from yeast displayed library, a total amount of yeast that was ten to forty times the library size was grown and scFv display induced. For sorting, libraries were incubated with either recombinant produced toxin domain (ALC, BLC, BHC, etc) or holotoxin (BoNT/C, BoNT/D, BoNT/E, BoNT/F, BoNT/G, etc) in five times excess of antigen molecular, assuming each yeast expresses 1×105 scFv on the cell surface, at room temperature (RT) for 1 hr. The first two rounds were usually done by staining with 100-200 nM of each toxin or toxin domain, and the third and fourth round of staining were done by staining with lower (1-10 nM) concentration of the same toxin or another subtype of the same BoNT serotype. Libraries were washed once with ice cold FACS buffer (PBS (1.9 mM NaH2PO4, 8.1 mM Na2HPO4, 154 mM NaCl, pH7.4), 0.5% BSA, 1 mM MgCl2, 0.5 mM CaCl2) before reacting with the properly diluted toxin or toxin domain at room temperature for 1-2 hrs. BoNT binding was detected either by staining with Alexa-647 labeled human antibodies developed in the lab previously (such as ING2 for BoNT/A, B6.1 for BoNT/B, etc) or by using commercial polyclonal rabbit antibody before any human antibody was developed (such as for BoNT/C and BoNT/F, polyclonal rabbit antibody from Metabiologics (Madison, Wis.)). The staining reaction is normally performed at 4° C. for an hour, and simultaneously, scFv display level was quantitated by staining with 2.5 μg/ml anti-SV5 mAb labeled with Alexa-488. When rabbit polyclonal antibody was used for detection (i.e, to get the first human antibody for BoNT/C, BoNT/F, or BoNT/G), PE labeled goat anti-rabbit IgG (Jackson ImmunoResearch) is followed. Yeast libraries were washed as described, re-suspended in 200 to 700 μl of FACS buffer and were sorted on a FACS Aria (Becton-Dickinson) with sort gates set to collect all SV5 positive BoNT binding yeast. After the last round of sorting, yeast were plated on SD-CAA plates and individual clones grown and induced. Individual clones were screened to identify BoNT binding scFv and unique clones identified by DNA sequencing (Amersdorfer P et al. (2002) Vaccine. 20:1640-1648). For each unique clone, the affinity of the yeast displayed scFv for either the target toxin domain (ALC, BLC or BHC, etc) or for all the subtypes of the corresponding BoNT (BoNT/A1, A2, A3, BoNT/B1, B2, B3, B4, BoNT/C, CD, DC, D, BoNT/F1, 202F, BoNT/G etc) was determined exactly as previously described (Razai A et al. (2005) J. Mol. Biol. 351:158-169; Lou J. et al. (2010) Protein Engineering, Design & Selection, 23:311-319).
As an example for the BoNT toxin domain yeast display, primers BoNTB1-HC5-NcoI, BoNTB1-HC3-NotI, BoNTB1-HN5-NcoI, BoNTB1-HN3-NotI, and BoNTB1-LC5-NcoI and BoNTB1-LC3-NotI were designed to PCR amplify the BoNT/B1 (NCBI accession number YP—001693307) HC (amino acids N853-E1290) HN (amino acids P443-F854), or LC (amino acids M1-K441) gene fragment respectively adding the restriction sites NcoI and NotI. Each gene fragment was amplified by using PCR from a synthetic gene construct (Gilsdorf, J et al. (2006) Protein Expr Purif 46:256-67; Smith, L. A. & Henderson, I. (2006). Vaccines to protect against the neurotoxins. In Treatments from Toxins: The therapeutic potential of Clostridial neurotoxins (Foster, K., Hambleton, I. & Shone, C., eds.), pp. 75-106. CRC Press, Boca Raton, Fla.). Following digestion of both pYD2 and the resulting PCR amplification product with NcoI and Nod, the BoNT/B gene fragments were gel-purified and ligated into pYD2. Ligation mixtures were used to transform E. coli DH5α and correct transformed clones identified by DNA sequencing of the purified plasmid DNA. The same plasmid DNA was later used to transform LiAc-treated EBY100 cells. Yeast cultures were then grown and induced, as described above. Similarly primers HCFor, HCRev, HNFor, HNRev, and LCFor and LCRev were designed to PCR amplify the BoNT/A, BoNT/C, BoNT/D, BoNT/E, BoNT/F and BoNT/G HC, HN, or LC gene fragment respectively from synthetic gene constructs as reported (Levy R. et al. (2007) J. Mol. Biol. 365:196-210).
For mapping scFv binding to yeast displayed BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F or BoNT/G domains, scFv genes in pYD2 were excised by digestion with Nco1 and Not1, ligated into pSYN1, and the ligation mixture used to transform E. coli DH5 cc. Soluble scFv expression was induced and the periplasmic fraction containing the scFv prepared as previously described (Schier, R et al. (1995) Immunotechnology 1:73-81). Periplasmic fractions containing scFv were incubated for 1 hour at RT with yeast displaying BoNT domains. After washing with phosphate buffered saline (PBS), yeast were incubated with 1 μg/ml of mAb 9E10 which recognizes an epitope tag at the scFv C-terminus. After washing, 9E10 binding was detected using 1 μg/ml anti-mouse gamma1 specific antibody (Jackson ImmunoResearch) and the level of BoNT domain display quantitated by incubation with 1 μg/ml of anti-SV5-Alexa-488. For some antibodies, mapping was performed by staining with 1 μg/ml of the respective IgG conjugated to Alexa-647. The IgG was converted from the scFv lead and produced in CHO cells as described below.
Each yeast displayed scFv was grown and induced and incubated with 20˜100 nM BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F or BoNT/G for 1 hour at RT followed by washing with PBS. After re-suspension, yeasts were incubated with either scFv containing periplasmic preparations (see above) or purified IgG, followed by washing and then incubation with 1 μg/ml 9E10. After washing, 9E10 binding was detected using 1 μg/ml anti-mouse gamma1 specific antibody (Jackson ImmunoResearch) and the level of BoNT domain display quantitated by incubation with 1 μg/ml of anti-SV5-Alexa-488. For some antibodies, mapping was performed by staining with 1 μg/ml of the respective IgG conjugated to Alexa-647.
Affinity and Specificity Maturation of Selected Lead scFv by Chain Shuffling
Since the lead scFvs selected from the original library may not always have high enough affinity or broad enough specificity, we used chain shuffling to engineer the lead antibody before change them into full length IgG. Two different versions of a yeast display vector were created and used as: pYD2 and pYD4. The key differences between these two vectors are the linker between the VH and VL of the antibody and an HA tag following the leader sequence. The pYD2 vector has the traditional (G4S)3 linker as reported (Schier, R et al. (1995) Immunotechnology 1:73-81), but the pYD4 has a new 20 amino acid linker (SGGSTSGSGKPGSGEGSSGS; SEQ ID NO:507) with 4 designed cloning sites (Afl II, BspE 1, BamHI and BssH II) integrated, and it has HA tag following the V gene leader sequence, so either the VH or the VL can easily shuffled by cloning. For a human library, a light chain library was created in the pYD2 by cloning in VL gene repertoires from donors six, nine, and ten. cDNA was synthesized from total RNA prepared from donor PBLs by using AMV reverse transcriptase (Invitrogen) and HuCK1FOR primers as published (Marks, J D et al. (1991). J Mol Biol 222:581-97; Amersdorfer P et al. (2002) Vaccine. 20: 1640-1648). VK gene fragments were amplified by PCR from cDNA by using Pfu polymerase (Stratagene) and an equimolar mixture of the four GAP5-HuRJHBACK primers and the primer pYDForVL (Marks, J D et al. (1991) J Mol Biol 222:581-97). To further increase light chain diversity, the light chain repertoire cloned into pYD2 from a large non-immune scFv phage antibody library was also utilized (Sheets, M D et al. (1998) Proc Nail Acad Sci USA 95:6157-62). PCR fragments were gel purified, digested with Nco1 and NotI, and ligated into NcoI-NotI digested pYD2. The ligation mixture was used to transform E. coli DH5α, creating a light chain shuffling library of size 4.2×107 that was determined to be diverse by PCR fingerprinting and DNA sequencing, and it is created and kept in bacteria. To create light chain shuffled scFv libraries, light chain library DNA was prepared and digested with either NheI or HindIII and NcoI. It was determined that when cutting with Nhe1-Not1, recombination could occur between the scFv linker DNA and the Gly-Ser linker after the AgaII protein, resulting in approximately 1-20% of transformants having no light chain. Digesting with HindIII cuts in AgaII, eliminating this problem. The VH gene was amplified from its respective scFv gene in pYD2 using primers that annealed upstream of the VH gene (pYDFOR) and a primer than annealed in the framework 4 linker region (LinkRev). Gel purified VH gene was mixed with digested vector DNA and used to transform LiAc-treated EBY100 yeast cells. Alternatively, scFv chain shuffled libraries were created by amplifying the VH FR4-scFv linker-VL gene repertoire from pYD2 and splicing it to a specific VH gene by overlap extension. The chain shuffled scFv gene repertoire was then cloned into pYD2. A total of twenty chain shuffled libraries were created from the VH genes of scFv lead as previously described (Marks J D et al. (1992) Bio/Technology 10:779-783) to get the affinity and cross reactivity maturated clones of 1B12.3, 1B12.4, 1C1.1, 4C2, 4C4, 4C4.1, 4C4.2, 4C5, 4C10, 4C10.1, 4C10.2 87C78, 8DC1, 8DC1.2, 8DC2, 8DC3, 8DC4, 8DC4.1, 8DC5, 4E17.2, 43D3, etc. The library size ranged from 2.0×106 to 4.0×107. Owing to the unique design of pYD4 vector, it is relative easy to chain shuffle the lead scFv by either cut and ligation or gap-repair. So, all the lead scFv with double digit nM or worse affinity are chain shuffled similarly before they were converted into full length IgG, such as 6F8.
To select higher affinity scFv, light chain shuffled libraries were grown and scFv display on the yeast surface induced. Induced yeast were stained with BoNT/A1, BoNT/B1, BoNT/C, BoNT/D, BoNT/E, BoNT/F, or BoNT/G at a concentration 10 times greater than or equal to the KD for the first two rounds of sorting respectively with the majority of BoNT binding yeast collected. Subsequent rounds of sorting were increasingly stringent with the antigen concentration decreased and less than 1% of the yeast collected. A total of four to six rounds of sorting were performed for each chain shuffled library, after which the sort output was plated to allow for characterization of individual yeast displayed scFv. Ten individual clones were characterized by DNA sequencing of the scFv gene and the affinity for each serotype or subtype of BoNT determined as previously described (Razai A et al. (2005) J. Mol. Biol. 351:158-169; Lou J. et al. (2010) Protein Engineering, Design & Selection, 23:311-319).
The VH and VK genes of lead scFv were amplified with primers annealing to the 5′ and 3′ ends of the full length VH and VL genes, and then cloned into vectors for stable expression in CHO cells as previously described (Razai A et al. (2005) J. Mol. Biol. 351:158-169; Nowakowski A et al. (2002) Proc. Natl. Acad. Sci. USA 99:11346-11350). These vector results in expression of IgG of the γ1/kappa or γ1/lambda isotype from the transformed CHO cells. Clones containing the correct VH and VL genes were identified by DNA sequencing, and vector DNA was used to transfect CHO DG44 cells by electroporation. Stable cell lines were established by selection in G418 and expanded into 1L spinner flasks or 10L wavebags. Supernatant containing IgG were collected, concentrated by ultra filtration, and purified on Protein G (Pharmacia) column as described in Kehoe J et al. (2006) Molecular & Cellular Proteomics 5:2350-2362.
Equilibrium binding studies were conducted at room temperature (˜25° C.) using a KinExA 3000 flow fluorimeter to quantify the free BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F or BoNT/G at equilibrium using varying concentrations of antibody (Blake, R C et al. (1999) Anal Biochem 272:123-34; Ohmura, N et al. (2001) Anal Chem 73:3392-9) as previously described (Razai A et al. (2005) J. Mol. Biol. 351:158-169). Studies of antibody antigen reaction were performed in PBS (pH 7.4), with 1 mg/ml BSA and 0.02% (w/v) sodium azide as a preservative in the reaction mixture. Antibody was serially diluted into a constant concentration of pure BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, or BoNT/G sufficient to produce a reasonable signal, where the antibody concentration was varied from less than 0.1 to greater than 10-fold above the value of the apparent KD. The BoNT concentrations were no more than 4-fold above the KD to ensure a KD controlled experiment. Samples were allowed to reach equilibrium for as long as three days, then each of the 12 dilutions were passed over a flow cell with a 4 mm column of Azlactone beads (Sapidyne Instruments) covalently coated with the corresponding antibody to capture the free BoNT. Passing an Alexa-647 labeled BoNT antibody binding a non-overlapping epitope over the beads produced a signal relative to the amount of free BoNT bound to the beads. All data points were run in duplicate and sample volume varied from 4 to 25 ml depending on antibody affinity. The equilibrium titration data were fit to a 1:1 reversible binding model using KinExA Pro Software (version 1.0.2; Sapidyne Instruments) to determine the KD (Drake, A W et al. (2004) Anal Biochem 328:35-43).
Measurement of mAb Inhibition of SNAP25 Cleavage by BoNT/A Lc
As one of the many functional tests for the selected mAbs, an SDS-PAGE and a fluorescent resonance energy transfer (FRET) assay of ALC inhibition was performed as published (Dong, J., et al. (2010) Journal of Molecular Biology 397:1106-1118, Pires-Alves, M. et al. (2009) Toxicon 53:392-399). Briefly, for the SDS-PAGE assay, BoNT/A Lc 448 was mixed with or without testing mAb in 50 mM Tris buffer, pH 8.0. SNAP25 substrate as added into the mixture to initiate the reaction. The final volume was 40 μl, and final concentration was approximately 20 nM for BoNT/A Lc and 5 mM for SNAP25. The concentration of each mAb varies but was at least 1× fold higher than the BoNT/A Lc concentration. The reaction was run at room temperature for 1˜30 min or for the indicated time, stopped by adding SDS-PAGE loading buffer and heated for 10 min at 99° C., then analyzed by SDS-PAGE. The gel was stained in 0.1% Coomassie Blue R-250 (see
Yeast displayed scFv antibody libraries were constructed from V-genes isolated either from human volunteers immunized with pentavalent botulinum toxoid (serotypes BoNT/A1, BoNT/B1, BoNT/C, BoNT/D, and BoNT/E) or mice selectively immunized with monovalent toxin fragment (BoNT/A LC, BoNT/B LC, BoNT/B HC, BoNT/F HC, etc) or BoNT holotoxin. RNA was prepared from the peripheral blood lymphocytes of 6 different human donors or from the spleens of 13 immunized mice, and the immunoglobulin heavy (VH) and light (VL) chain variable regions amplified using the polymerase chain reaction (PCR) as previously described (Marks, J D et al. (1991) J Mol Biol 222, 581-97; Marks, J D et al. (1991) Eur. J. Immunol. 21, 985-991. Amersdorfer P et al. (1997) Infection Immunity 65: 3743-3752). VH and VL gene repertoires from each donor or mouse were spliced together to create scFv gene repertoires which were cloned for display as N-terminal fusions to the agglutinin receptor (Aga II) protein on the surface of yeast (Boder, ET (1997) Nat. Biotechnol. 15:553-557). A total of 19 yeast displayed scFv libraries (13 mouse V-gene+6 human V-gene) were generated, ranging in size from 4.1 to 25.7×107 members. Each library was diverse as determined by PCR fingerprinting and DNA sequencing of 10 randomly selected clones from the library. After induction of scFv display, the percentage of yeast displaying scFv ranged from 45-55% as determined by staining with SV5 antibody binding the C-terminal SV5 tag fused to each scFv.
To generate BoNT/A LC specific mAbs, three different yeast displayed scFv libraries were constructed using pYD4 vector and V-genes from BoNT/A LC-immunized mouse spleen RNA, and were subjected to several rounds of sorting using different concentrations of purified BoNT/A LC. Sorts were performed using relatively high concentrations in the initial rounds (100-200 nM) to ensure collection of all antigen-binding scFv. In later rounds, the antigen concentration was decreased to between 1-10 nM to select higher affinity antibodies. Libraries were sorted a total of three to six rounds, and yeast displayed scFv from individual colonies were screened for binding to both the BoNT/A LC and BoNT/A1 holotoxin. Antigen-binding clones were further characterized with respect to the diversity of scFv present using colony PCR and DNA sequencing. In this manner, 17 scFv were isolated, each with a unique VH and/or VL (Table 1,
indicates data missing or illegible when filed
Similar to the procedures used for BoNT/A LC specific mAbs generation, BoNT/B LC specific mAbs were screened and selected from three different yeast displayed scFv libraries which were constructed from BoNT/B LC-immunized mouse spleen RNA and the yeast display vector pYD4. Each library was subjected to several rounds of sorting using different concentrations of purified BoNT/B LC. 22 scFv were isolated, each with a unique VH and/or VL (Table 2,
Similar to the procedures used for BoNT/A LC specific mAb generation, BoNT/B HC specific mAbs were screened and selected from three different yeast displayed scFv libraries which were constructed from BoNT/B HC immunized mice spleen RNA using pYD4 vector. Each library was subjected to several rounds of sorting using different concentrations of purified BoNT/B HC. 14 scFv were isolated, each with a unique VH CDR3 (Table 3,
To generate additional anti BoNT/F mAbs, procedures similar to those used for BoNT/A LC specific mAb generation were employed. BoNT/F specific mAbs were screened and selected from four different yeast displayed scFv libraries which were constructed from BoNT/F holotoxin-immunized mouse spleen RNA and pYD4 vector, and subjected to several rounds of sorting using different concentrations of BoNT/F. 36 scFv were isolated or engineered after the initial leads were found, each with a unique VH or VL (Table 4,
A human BoNT/F antibody that binds a translocation domain epitope that is conserved in all BoNT/F subtypes was identified. Using chain shuffling, the affinity of this antibody for BoNT/F was increased from approximately 10 nM to less than 1 nM (scFv 4E17.2, Table 5). A fully human IgG (6F5) has been constructed from this scFv with a KD of 0.66 nM for BoNT/F1 and which binds all of the BoNT/F subtypes. To increase the potency of this mAb, the affinity of the scFv was further increased approximately 6 fold using error prone mutagenesis and an IgG (6F5.1) was constructed from the affinity matured scFv.
Table 5. Properties of BoNT/F Antibodies.
Antibody name and VH CDR3 sequence are provided. For cross reactivity, the KD of the yeast displayed scFv for BoNT/F1 (proteolytic BoNT/F) is indicated, as well as whether it binds the other BoNT/F subtypes. Epitope bound (HC, HN, or LC) is indicated. Where IgG has been produced, the IgG KD for proteolytic BoNT/F1 is provided. “Yes” means binding; “No” means no clear binding at the maximum toxin concentration tested; “NM” means not measured.
The antibodies were shown to have the requisite potency for development as a therapeutic antitoxin (Table 7). The combination of 6F5:6 F9:6 F10 protected 7/10 mice challenged with 40,000 mouse LD50s of BoNT/F1.
Table 7. In Vivo Protection of Mice Challenged with the Indicated Number of Mouse LD50s of BoNT/F1.
The combination of 6F5:6 F9:6 F10 protected 7/10 mice challenged with 40,000 mouse LD50s of BoNT/F1. The number of mice surviving/number of mice challenged is indicated. “NM” means “not measured.”
To generate a panel of human antibodies to type C and/or D botulinum neurotoxins, six different yeast displayed scFv libraries were constructed using pYD2 or pYD4 vectors and sorted separately on holotoxin BoNT/C, BoNT/D, BoNT/CD, or BoNT/DC. Those libraries were constructed with V-genes isolated from pentavalent botulinum toxoid (BoNT/A to BoNT/E alphabetically)-immunized human donors. Similar to the process used to select antibody leads for BoNT/A LC, sorts were performed using relatively high concentrations of BoNT/C1 or other holotoxin in the initial rounds (100-200 nM) to ensure collection of all antigen binding scFv. In later rounds, the antigen concentration was decreased to between 1-25 nM to select for higher affinity antibodies, and sorts were also performed using other BoNT/C or BoNT/D or mosaic subtypes (BoNT/CD, BoNT/DC) to select cross reactive antibodies. Libraries were sorted using a total of three to six rounds until a positive binding population of over 10% was present during the sorting, and yeast displayed scFv from individual colonies were screened for binding to BoNT/C, BoNT/D, BoNT/CD or BoNT/DC. Antigen binding clones were further characterized with respect to the diversity of scFv present using colony PCR and DNA sequencing. In this manner, 47 scFv were isolated or engineered, each with a unique VH and/or VL (Table 8,
Similar to the procedure used for the selection of human antibodies against BoNT/C and D, five of the same six human donor yeast displayed antibody libraries described in Example 1 were sorted with BoNT/F1 or BoNT/G toxin, and 8 scFv were isolated specific for BoNT/F, 11 scFv were isolate specific for BoNT/G, each with a unique VH CDR3 (Table 4,
To determine which BoNT functional domains were bound by selected scFv leads, the HC, HN, and LC genes and some combination of them (e.g, LCHN) of BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, and BoNT/G were cloned into pYD2 and displayed on the surface of Saccarhomyces cerevisiae using methods similar to those as previously reported for BoNT/A domains (Levy R. et al. (2007) J. Mol. Biol. 365:196-210). Each domain was well displayed on the yeast surface, as quantitated using a C-terminal SV5 tag fused to each domain. The domain recognized by each of the scFvs was determined by incubating yeast displayed BoNT domains with either native soluble scFv expressed in E. coli, or with whole IgG constructed from the scFv lead gene and produced from CHO cells (see below). Native scFv was generated by subcloning the scFv lead genes into the bacterial secretion vector pSYN1 (Schier, R. et al. (1995) Immunotechnology 1:73-81). To determine how many non-overlapping BoNT epitopes were recognized by all the lead antibodies, yeast displayed scFv were incubated with BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, or BoNT/G holotoxin, followed by incubation with purified native scFv. scFv recognizing overlapping epitopes showed no yeast staining while scFv binding non-overlapping epitopes stained the yeast surface (
8) that some of the 175 scFv leads bind only one subtype of the selected BoNT serotype (e.g. mAb 4C8 binds BoNT/C1 only). Others bind more than one subtype or serotype (e.g., mAb 4C4 binds BoNT/C, BoNT/CD, BoNT/DC and BoNT/D; mAb 4E17.2 and 6F5.1 bind all subtypes of BoNT/A, BoNT/B, BoNT/E and BoNT/F).
A panel of 52 yeast-displayed scFv binding to BoNT/C, BoNT/D, BoNT/CD, or BoNT D/C was isolated (Table 6, 9). Yeast-displayed scFv were first selected with one serotype (BoNT/C or BoNT/CD), then screened for binding to pure or crude culture supernatants prepared from Clostridial strains producing BoNT/CD, BoNT/DC or BoNT/D (Table 6, 9). The results identified four lead antibodies, 4C4, 4C10, 8DC1, and 8DC4, that each bound to BoNT/C, CD, DC, and D. Other antibodies were generated (e.g. 4C2, 87C1, 8DC8) that each bound to a pair of BoNT's, such as C and CD, or DC and D. Using yeast-displayed domains of LC, HN, and HC, it proved possible to map the binding of most of these antibodies to their cognate BoNT domain (Table 9). 4C4, 4C10, and 8DC1 bind non-overlapping epitopes on the HN, LC, and HN, respectively. 8DC 1 and 8DC4 bind overlapping epitopes on the HN. These studies identified four antibodies binding three non-overlapping epitopes shared by BoNT/C, CD, DC and D that could serve as lead molecules for an antitoxin for BoNT/C and BoNT/D.
The affinities and cross-reactivities of antibodies 4C4, 4C10, 8DC1, and 8DC4 were increased by using yeast-displayed mutant scFv libraries and selecting for higher affinity and better cross-reactivity using previously described methods (Garcia et al. (2007) Nat. Biotechnol. 25:107; Razai A. et al. (2005) J. Mol. Biol. 351:158-169. Lou J. et al. (2010) Protein Engineering, Design & Selection, 23(4):311-319). For each antibody, these initial efforts resulted in an increase in scFv affinity of at least 10-fold. For animal studies, scFv were converted to full length human IgG1 molecules which were expressed from CHO cells and purified using protein G. Solution affinities of the affinity matured antibodies (and in some instances the parental antibody) were measured by using flow fluorimetry (Table 10).
The ability of selected antibodies to protect mice against challenge with BoNT was evaluated in vivo using a standard mouse neutralization assay. As observed with other BoNT serotypes, single antibodies only protected mice against very low dose challenge with toxin. BoNT/C or BoNT/DC toxins were used for challenge as they were the only commercially available BoNT/C or BoNT/D serotypes. A combination of three antibodies binding BoNT/C with very high affinity (1C1.1:4 C2:4 C10, see affinities in Table 10) at a dose of 50 μg of total antibody completely protected mice against challenge with 20,000 mouse LD50 of BoNT/C (Table 11). This combination was not evaluated on BoNT/DC, since one of these antibodies (1C1.1) did not bind BoNT/DC. Using combinations of four antibodies (among 4C2, 4C4.2, 8DC1.2, 4C10.2, and 8DC4.1) binding both BoNT/C, BoNT/D and their mosaic toxins, comparable potencies could be achieved against both BoNT/C and BoNT/DC (Table 11). Note that the cross-reactive antibodies are of lower affinity than 1C1.1 and 4C2, which potently neutralize BoNT/C in a three antibody combination.
Antibodies grouped together are clonally related, differing primarily by affinity for the different toxin subtypes. Epitopes are indicated as toxin domain bound and by unique epitope number. Subtype cross reactivity is indicated. A1>>>A2, significantly higher affinity for BoNT/A1 compared to BoNT/A2; A2>>A1, significantly higher affinity for BoNT/A2 compared to BoNT/A1. Antibodies shown as ‘binding’ BoNT/A4 are assumed to bind based on identity of the epitope in BoNT/A4 compared to the other subtypes.
Species: M=mouse; H=human; HZ=humanized, AM=affinity matured; SP=specificity improved
It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes.
While the subject antibody, method, and composition have been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
This application claims the benefit of U.S. Provisional Patent Application No. 61/378,862, filed Aug. 31, 2010, U.S. Provisional Patent Application No. 61/430,084, filed Jan. 5, 2011, which applications are incorporated herein by reference in their entirety.
This invention was made with government support under Grant No. A1075443 awarded by the National Institutes of Health, Grant No. HDTRA1-07-C-0030 awarded by the Department of Defense, Defense Threat Reduction Agency, and Grant No. 200-2006-16697 awarded by the Centers for Disease Control. The government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US11/50050 | 8/31/2011 | WO | 00 | 8/9/2013 |
| Number | Date | Country | |
|---|---|---|---|
| 61378862 | Aug 2010 | US | |
| 61430084 | Jan 2011 | US |
