METHOD FOR OBTAINING RECEPTOR AGONIST ANTIBODIES

Abstract: A method is provided for generating antibodies which demonstrate the agonist properties of the naturally occuring ligand of a receptor molecule by using as an immunogen a recombinant immunogen which corresponds to a multimeric form of a receptor. In this immunogen the extracellular domains are in a similar disposition to that expected for receptors having two or more subunits on the surface of the cell.

Description: METHOD FOR OBTAINING RECEPTOR AGONIST ANTIBODIES Cross Reference to Related Applications This application is a continuation-in-part of co-pending U.S. application serial number 08/474,673, filed June 7, 1995, the contents of which is incoφorated hereby by reference. Field of the Invention The present invention relates generally to the generation of monoclonal antibodies by use of a selected antigen; and more particularly to the generation of monoclonal antibodies which are receptor agonists. Background of the Invention A vast majority of receptors of the single transmembrane class respond to ligand binding by some form of aggregation. This aggregation can be between identical receptor subunits (as in homodimerization, homotrimerization, etc.) or between different receptor subunits (as is heterodimerization, heterotrimerization, etc). This aggregation appears to be part of the signal for the target cell to respond biologically, in that mutants of the ligand which are unable to interact with the second subunit are still able to bind, but no longer cause dimerization and biological activation of the receptor [P. R. Young, Curr. Opin. Biotech.. 3:408-421 (1992)]. For example, there is evidence in the literature that suggests dimerization of the erythropoietin receptor (EpoR) upon ligand binding [S. S. Watowich et al, Molec. Cell Biol.. 14:3535-3549 (1992) and S. S. Watowich et al, Proc. Natl. Acad. Sci.. USA. 89:2140-2144 (1992)]. Reports about IL-6 have indicated that its second subunit gpl30 may dimerize upon IL-6 binding [M. Murkami et al, Science. 260: 1808-1810 (1993)]. For some receptors in which homodimerization is induced by ligand binding, monoclonal antibodies (mAbs) were discovered which had agonist properties. These include mAbs to EGF, TNF and growth hormone receptors [A. B. Schrieber et al, J. Biol. Chem.. 258:846-853 (1983); L. H. K. Defize et al, EMBO J.. 5: 1187-1192 (1986); H. Engelmann et al, J. Biol. Chem.. 265:14497-14504 (1990); and G. Fuh et al, Science. 256:1677-1680 (1992)]. In each case, these mAbs, by virtue of their two antigen recognition sites, were able to bring together two receptors and thus activate them. Fab fragments made from these mAbs were inactive. In some cases, the apparent affinity of the antibody for receptor was comparable to that of the ligand, e.g., growth hormone [Fuh et al, cited above]. It has also been discovered that antibodies to IL-3 receptor have agonist properties [Suguwara et al, J. Immunol..140:526-530 (1988)]. Previous literature has described the production of anti-erythropoietin receptor antibodies [A. D'Andrea et al, Blood. £2:46-52 (1993); A. D'Andrea et al, Blood. 4:1982-1991 (1994) and M-G Yet et al, Blood. 82: 1713-1719 (1993). See also, PCT Application WO96/03438 published 8 Feburary 1996. While the Yet et al, reference suggests the occurrence of possible EPO-like activity in one mAb, the mAb is not characterized. Neither Yet et al, nor the other literature provides any reproducible manner of generating agonist mAbs. There remains a need in the art for the development of additional mAbs which have an affinity for receptors comparable to that of the ligand, and which can act as agonists of the receptor. Summary of the Invention In one aspect, the present invention provides a method for reliably generating an antibody which is an agonist of a receptor. This method employs as the immunizing antigen, a recombinant immunogen which consists of a first extracellular domain of a receptor molecule spaced apart from a second extracellular domain from that receptor by a bridging moiety. The bridging moiety places the first domain and the second domain into a functional proximity which mimics the functional domain orientation and proximity of the naturally occurring multimeric receptor. The bridging moiety can be an amino acid spacer peptide, an organic molecule, an Fc portion of a human immunoglobulin or an amphipathic helix, for example. In another aspect, the invention includes antibodies produced by the above- described method. The antibodies so generated are characterized by the ability to bind to the naturally occurring receptor and by such binding initiate the biological activity of the receptor. The antibodies of the invention may be chimeric antibodies, humanized antibodies, monoclonal antibodies or polyclonal antibodies. In still another aspect, the invention provides a recombinant polynucleotide sequence comprising a nucleotide sequence encoding the extracellular domain of a receptor molecule fused in frame to a nucleotide sequence encoding a specific proteolytic cleavage site, said cleavage sequence associated with a bridging moiety. Yet a further aspect of the invention is the recombinant multimeric immunogen itself. Additional aspects of this invention include a vector comprising a polynucleotide sequence described above under the control of suitable regulatory sequences capable of directing replication and expression of the polynucleotide sequence in a host cell, and a transformed host cell. Still other aspects of the invention include therapeutic reagents comprising the antibodies produced by the method of this invention, as well as a method of treating a disease condition by administering a pharmaceutical composition of the invention. Other aspects and advantages of the present invention are described further in the following detailed description of the preferred embodiments thereof. Brief Description of the Drawings Fig. 1 is a graph illustrating the effects of the dimeric fusion protein EpoRFc and the monomeric protein mEpoR on erythropoietin stimulation of UT-7 Epo cells, which plots % positive control vs. concentration (ng/ml). Fig. 2 is a graph illustrating the effects of the dimeric fusion protein EpoRFc and the monomeric protein mEpoR on erythropoietin stimulation of DA3Epowt cells, which plots % positive control vs. concentration (ng/ml). Fig. 3 is a graph illustrating the effects of the dimeric fusion protein EpoRFc and the monomeric protein mEpoR on erythropoietin stimulation in an CFU-E assay, which plots % positive control vs. concentration (ng/ml). Fig.4 is a bar graph demonstrating the binding of antibodies developed in response to immunization with the EpoRFc fusion protein to 32D/Epo wt and parental 32D Fig. (4a) and UT7-EPO, cells, plotting %Isotyρe control log fluorescence vs. control (CTL) and supernatant designations. Fig. 5 is a bar graph demonstrating the results of an UT7-Epo proliferation assay with three mAbs to EpoRFc, plotting %Epo maximum vs. dilutions of supernatants. The supernatant designations are listed above the bars. Fig. 6 is a bar graph demonstrating the ability of 4 mAbs to EPORF c to stimulate the proliferation and differentiation of human bone marrow progenitor cells to form red blood cell colonies (CFU-E), plotting Numbers of CFU-E vs. positive and negative EPO controls and supernatant dilutions. The supernatant designations are listed above the bars. Fig. 7 is the DNA sequence [SEQ ID NO: 1] for plasmid mtalsEpoRFc containing the sequence encoding the EpoRFc fusion protein under control of a Drosophila S2 mtn promoter. Nucleotides 1 to 897 contain the promoter sequence. The EpoRFc fusion protein [SEQ ID NO: 2] is encoded by the following: nucleotides 898 to 1647 encode the EpoR extracellular domain protein; nucleotides 1648 to 1659 encode the Factor Xa cleavage sequence; nucleotides 1660 to 2361 encoding the human IgGj Fc sequence. The remainder of the sequence is derived from the plasmid parent. See Example 1. Fig. 8 is the DNA sequence [SEQ ID NO: 3] of CosFcLink vector from which a KpnI Xbal insert containing the IgGl Fc region was obtained. Detailed Description of the Invention The present invention provides a reproducible and reliable composition and method for generating antibodies which demonstrate the agonist properties of the naturally occurring ligand of a receptor molecule. While, in principle, any purified preparation could be used to generate antibodies to a receptor, and from these some may be agonists, this invention provides a specific immunogen which corresponds to a multimeric form of a receptor in which the extracellular domains are in a similar disposition to that expected for receptors having two or more subunits on the surface of the cell. /. The Recombinant Immunogen The recombinant immunogen of the present invention consists of an extracellular domain of a selected receptor molecule which is involved in ligand binding via the interaction of more than one extracellular domain. The extracellular domain is spaced apart from a second extracellular receptor domain by a bridging moiety. By "extracellular domain" is meant that portion of a receptor protein which is localized on the extracellular surface of a cell and which contributes to interaction and binding with its native ligand. The receptor subunit which contributes the extracellular domain(s) of the immunogen may be any receptor subunit which accomplishes ligand binding via a homodimer of the extracellular domain, a heterodimer of two different subunits of the receptor's extracellular domain, or a multimer of subunits. Receptors which homodimerize upon ligand binding and thus may contribute extracellular domains to the recombinant immunogen include those for, inter alia, erythropoietin (EPO) and thrombopoietin (CMPL), G-CSF, M-CSF, TGF-a, EGF, neu, growth hormone, prolactin, placental lactogen, c-kit (stem cell factor receptor), p50 and p75 receptor subunits of TNFa, and TNFβ. Other receptors which are anticipated to dimerize based on homology to TNF and which can be included in this list are Fas, CD40, CD27, CD30, 4- IBB and OX40. Similarly, receptors which are already in a homodimeric form on the cell surface, prior to ligand binding may also contribute the extracellular domain(s) to the immunogen. These latter receptors include, inter alia, insulin, IGF1 and IGF2, and PDGF. PDGF includes dimeric ligand made of two chains A and B and two receptor subunits a and b. Ligands and receptors can associate as homo- or hetero- dimers. Relaxin is also anticipated to be a dimeric receptor prior to ligand binding based on its homology to insulin and IGF. Receptors which are formed by heterodimers of two different subunits may also be employed as contributors of extracellular domain(s) of one or both of the subunits to the recombinant. Such receptors include, inter alia, GM-CSF, IL-3, IL- 5, IL-6, Oncostatin M, CNTF, LIP, NGF, FGF, IL-4, JL-13, IFNa, IFNβ, IFNg, TGFB1, TGFB2 and IL-12. Receptors, such as IL-3, which involve more than one subunit may respond to this method, if dimerization of one of the subunits is required for signal transduction. Receptors which form other aggregations, such as trimers of IL-2 receptor subunits, may also be used as sources of extracellular domain(s) for the recombinant immunogen of this invention. The extracellular domains of the selected receptor useful in the recombinant immunogen may be isolated and/or otherwise obtained by resort to the published and publicly available receptor sequences. Methods conventional in the art may be employed to isolate or synthesize the appropriate nucleotide sequences encoding these domains for further manipulation in the generation of the immunogen of this invention. By the term "bridging moiety" is meant a peptide or non-peptide sequence that stably associates with itself and places the first extracellular domain and me second extracellular domain into functional proximity (i.e., a relationship between the two or more domains which mimics the three dimensional functional proximity of the domains in the naturally occurring multimeric receptor, during or prior to ligand binding. Preferably, me bridging moiety is of a sufficient size to bring together the membrane proximal regions (i.e., the regions closest to the transmembrane region) of the extracellular domain. The precise dimensions of the bridging region can be estimated from the relevant crystal structures, such as those for growth hormone and its receptor, or TNF and its receptor [see, e.g., DeVos et al, Science, 255:306 (1992)]. The suitability of a given "bridging moiety" can sometimes be evaluated empirically. For example, a dimeric form of a receptor which dimerizes upon binding of ligand is expected to have a higher affinity for ligand than a monomeric form of the extracellular domain of the receptor, if the bridging group is appropriate. This would be evidenced either by direct binding studies of ligand to monomeric and dimeric receptor, or by the relative ability of the two forms of receptor to neutralize the biological activity of the ligand. For example, Fig. 1 shows the ability of dimeric EpoRFc to neutralize Epo activity about 100 times more effectively than monomeric EpoR. An example of a bridging moiety is an amino acid spacer sequence (e.g., between 1 to 10 amino acids in length and optionally encoding a cleavage site) fused to a dimerization or oligomerization domain which permits the formation of dimers or oligomers, respectively. In the following example, for instance, a spacer encoding the Factor Xa cleavage site is part of the bridging moiety; and the dimerization domain is the hinge CH2CH3 region of a human IgGl . This IgG component consists of the CH2 and CH3 domains and the hinge region of IgGl including cysteine residues contributing to inter-heavy chain disulfide bonding, for example residues 11 and 14 of the IgGl hinge region [see, e.g., B. Frangione, Nature. 216: 939-941, (1967)]. Preferably the IgGl component consists of amino acids corresponding to residues 1-4 and 6-15 of the hinge, 1-110 of CH2 and 1-107 of CH3 of IgGl described by J. Ellison et al, Nucleic Acids Res..10: 4071-4079 (1982). Residue 5 of the hinge is changed from cysteine in the published IgGl sequence to alanine by alteration of TGT to GCC in the nucleotide sequence. The bridging moiety can also be an Fc portion of any human immunoglobulin with an intact hinge CH2CH3 region, including those derived from IgG, IgE, IgM, IgA and IgG Still another suitable bridging moiety is an amino acid spacer fused to the C terminal domain of the TNF-like receptor of the shope fibroma poxvirus [C. A. Smith et al, BBRC, 176: 335-342 (1991)]. The bridging moiety may also be an a dimerization domain like an ampbipathic helix, such as a leucine zipper [see, e.g., P. Pack et al, Biochem.. 3JL(6): 1579-1584 (Feb. 18, 1992)]. The bridging moiety may also be alkaline phosphatase. Still other desirable embodiments of the bridging moiety are organic molecules which can functionally associate the receptor extracellular domains as desired. Such organic molecules may be selected from among such molecules known to associate peptide sequences to each other for other biological uses, e.g., bifunctional cross-linkers, such as carbodiimide, glutaraldehyde and DSS, BS3, and others which may be obtained from several commercial sources. However, these associations may require combination with specific target sequences for cross- Unking, e.g., an exposed Cys or His for nickel chelate, to achieve the appropriate three dimensional disposition of receptor subunits. Choice of an appropriate cross- linker can be determined by comparison to known crystal structures of homologous receptors. The suitability of a particular peptide or non-peptide entity as a bridging moiety may be functionally assessed in a receptor ligand binding assay. The suitability of the bridging moiety may be determined if the recombinant immunogen binds the receptor's intended ligand with greater affinity than does the monomeric sequence of the receptor extracellular domain. Ligand binding assays for the selected receptors are known to those of skill in the art and may be readily selected without undue experimentation. See, for example, me EpoR ligand assays described in Komatsu et al, Blood. £2:456-464 (1993); Miura et al, Mol. Cell. Biol.. 11:4895-4902 (1991); Witthuhn etal, Cell, 74:227-236 (1993). Another bridging moiety or linker may be prepared by mutagenesis of a receptor in the membrane proximal domain to create unpaired Cys, which can disulfide bond to create a dimeric receptor. Such mutations can be evaluated for appropriateness by observing whether the full length receptor containing such a mutation is able to constitutively activate the ligand's activity upon transfection into suitable target cells (e.g., EpoR mutations) [see, e.g., Watowich et al, Proc. Natl. Acad. Sci.. USA.. ££:2140-2144 (1992)]. Thus, for example, the bridging moiety of the recombinant immunogen can associate two identical extracellular domains into an immunogen that mimics a homodimeric receptor. Alternately, for example, the bridging moiety can associate two different extracellular domains of subunits of one receptor into an immunogen that mimics a heterodimeric receptor. For example, for the heterodimeric association of different subunits from a heterodimeric receptor, a different bridging moiety could be used for each receptor subunit. The bridging moiety for a heterodimeric receptor is preferably a domain that cannot associate with itself, but which preferentially associates with a second domain. Thus, the first bridging moiety can be a CHI region of a light chain of a selected immunoglobulin. Its complementary bridging moiety is me CHI region of the heavy chain of the same immunoglobulin or the entire Fc region including the CHI, hinge, CH2, and CH3 regions of the heavy chain. It is also anticipated that various bridging entities may be employed in preparing other multimeric immunogens, e.g., trimers, by associating three identical domains or three extracellular domains from one, two or three subunits of a single receptor. It is presently preferred to use an Fc portion of an immunoglobulin as a bridging moiety to associate the extracellular receptor domains, as disclosed in Example 1 below. //. Construction and Preparation of the Recombinant Immunogen The present invention also provides the nucleic acid sequences encoding the recombinant immunogens described above. The nucleotide sequences encoding the extracellular domains of the receptors useful in the immunogens may be obtained from known receptor sequences by conventional means [see, J. Sambrook et al, Molecular Cloning: A Laboratory Manual.2d ed., Cold Spring Harbor Laboratory (1989)]. For example, the nucleotide sequences which form the immunogen of the invention may be isolated by conventional uses of polymerase chain reaction or conventional genetic engineering cloning techniques. Alternatively, these sequences may be constructed using chemical synthesis techniques. Optionally, a nucleotide sequence which encodes a peptide sequence which provides an enzymatic cleavage site (of which many are well known in the art) is fused in frame to the extracellular domain nucleotide sequence prior to its association with the dimerization or oligomerization domain of the bridging moiety. This facilitates cleavage of the extracellular domain from the bridging moiety following expression. According to the invention, the nucleic acid sequences encoding the extracellular domains may be modified as desired. It is within the skill of the art to obtain other polynucleotide sequences encoding these receptor domains useful in the invention. Such modifications at the nucleic acid level include, for example, modifications to the nucleotide sequences which are silent or which change the amino acids, e.g. to improve expression or secretion. Such modifications include amino terminal, carboxy terminal or internal deletions of the nucleotide sequences, as desired. Where the bridging moiety is an amino acid sequence, the nucleotide sequence encoding it is also obtained conventionally and fused to the extracellular domain sequence directly or via a cleavage site or via additional sequence intended as a spacer. For example, where the bridging moiety is an Fc portion of a human immunoglobulin with intact hinge CH2CH3 region, the nucleotide sequence encoding the Fc region is obtained from known antibody sequences, prepared by conventional techniques and fused in frame to the receptor sequences or to the sequence providing the enzymatic cleavage site. To produce recombinant immunogens of this invention, a DNA sequence of the invention encoding the extracellular receptor domain, is fused in frame to an optional cleavage site and further fused to a nucleotide sequence encoding a peptide bridging moiety. Preparation of the nucleic acid sequences may be carried out chemically, enzymatically, or by a combination of the two methods, in vitro or in vivo as appropriate. Thus, the DNA sequences may be prepared by the enzymatic ligation of appropriate DNA fragments, by conventional methods such as those described by D. M. Roberts et al, Biochem.. 24:5090-5098 (1985). The DNA fragments may be obtained by digestion of DNA containing the required sequences of nucleotides with appropriate restriction enzymes, by chemical synthesis, by enzymatic polymerization on DNA or RNA templates, or by a combination of these methods. These methods are generally provided by the commercial supplier of the reagents. For example, digestion with restriction enzymes may be performed in an appropriate buffer at a temperature of 20-70°C, generally in a volume of 50ul or less with 0.1-lOug DNA. Enzymatic polymerization of DNA may be carried out in vitro using a DNA polymerase such as DNA polymerase I (Klenow fragment) in an appropriate buffer containing the nucleoside triphosphates dATP, dCTP, dGTP and dTTP as required at a temperature of 10-37°C, generally in a volume of 50ul or less. Enzymatic ligation of DNA fragments may be carried out using a DNA ligase such as T4 DNA ligase in an appropriate buffer at a temperature of 4°C to ambient, generally in a volume of 50ul or less. The chemical synthesis of the DNA sequence or fragments may be carried out by conventional phosphotriester, phosphite or phosphoramidite chemistry, using solid phase techniques such as those described in "Chemical and Enzymatic Synthesis of Gene Fragments - A Laboratory Manual" (ed. H.G. Gassen and A. Lang), Verlag Chemie, Weinheim (1982), or in other scientific publications, for example M.J. Gait et al, Nucleic Acids Res.. 10: 6243 (1982) and others. Preferably an automated DNA synthesizer is employed. The DNA sequence is preferably prepared by ligating two or more DNA molecules which together comprise a DNA sequence encoding the compound. The DNA molecules may be obtained by the digestion with suitable restriction enzymes of vectors carrying the required coding sequences or by use of polymerase chain reaction technology. The precise structure of the DNA molecules and the way in which they are obtained depends upon the structure of me desired product. The design of a suitable strategy for the construction of the DNA molecule coding for the recombinant immunogen is a routine matter for one skilled in the art. Once the nucleotide sequence encoding the recombinant immunogen is designed, it is inserted into a suitable expression system. Systems for cloning and expression of a selected protein in a desired microorganism or cell, including, e.g. E. coli, Bacillus, Streptomyces, mammalian, insect, and yeast cells, are known and available from private and public laboratories and depositories and from commercial vendors. Desirably, a recombinant molecule or vector is constructed in which the polynucleotide sequence encoding the immunogen is operably linked to a heterologous expression control sequence permitting expression of the human protein. Numerous types of appropriate expression vectors are known in the art for eukaryotic (including human) protein expression, by standard molecular biology techniques. Such vectors may be selected from among conventional vector types including mammalian, insects, e.g., baculovirus expression, Drosophila S2 cell, or yeast, fungal, bacterial or viral expression systems. Other appropriate expression vectors, of which numerous types are known in the art, can also be used for this purpose. Methods for obtaining such expression vectors are well-known. See, for example, Sambrook et al, cited above; Miller et al, Genetic Engineering. 8:277-298 (Plenum Press 1986) and Johansen et al, Genes and Develop..3:882-889 (1989)]. Suitable host cells or cell lines for transfection by this method include mammalian cells, such as Human 293 cells, Chinese hamster ovary cells (CHO), the monkey COS-1 cell line or murine 3T3 cells derived from Swiss, Balb-c or NTH mice may be used. Another suitable mammalian cell line is the CV-1 cell line. Still other suitable mammalian host cells, as well as methods for transfection, culture, amplification, screening, and product production and purification are known in the art. [See, e.g., Gething and Sambrook, Nature. 293:620-625 (1981), or alternatively, Kaufman et al, Mol. Cell. Biol..5(7): 1750-1759 (1985) or Howley et al, U. S. Patent 4,419,446]. Similarly bacterial cells are useful as host cells for the present invention. For example, the various strains of E. coli (e.g., HB101, MC1061, and strains used in the following examples) are well-known as host cells in the field of biotechnology. Various strains of B. subtilis, Pseudomonas, Streptomyces, other bacilli and the like may also be employed in this method. Many strains of yeast cells known to those skilled in the art are also available as host cells for expression of the polypeptides of the present invention. Other fungal cells may also be employed as expression systems. Alternatively, insect cells such as Spodopterafrugipedera (Sf9) or Drosophila S2 may be used. Thus, the present invention provides a method for producing a recombinant novel multimeric receptor immunogen which involves transfecting a host cell with at least one expression vector containing a recombinant polynucleotide as above- described under the control of a transcriptional regulatory sequence, e.g. by conventional means such as electroporation. The transfected host cell is then cultured under suitable conditions that allow expression of the product of the recombinant polynucleotide. During expression, the recombinant multimeric immunogen is formed in the cell by the association of the bridging moiety with itself. The expressed multimeric protein is then recovered, isolated, and optionally purified from the culture medium (or from the cell, if expressed intracellularly) by appropriate means known to one of skill in the art. To generate a heterodimeric receptor immunogen, a vector is designed as above to carry a first receptor subunit which is fused to, e.g., the CHI region of the light chain. A vector is also designed to carry the second, different subunit of the receptor fused to e.g., the heavy chain sequence (e.g., CHI region or the entire Fc region of the same lg that contributes the light chain CHI, as described above). Alternatively both sequences could be present on a single vector. The vectors are prepared as described above. However, for a heterodimeric receptor immunogen, the host cell must be co-transfected with both receptor-bridging moiety polynucleotide sequences. Expression of both sequences in the host cell causes the light chain CHI and heavy chain CHI, or light chain CHI and heavy chain Fc sequences to associate only complementarily (i.e., with each other not with their identical counterparts in the cell). Heterodimeric receptor immunogens are thereby formed in the manner of a "Fab"-like fragment or an antibody-like fragment, respectively. Once expressed, the recombinant immunogen (e.g., homodimeric or heterodimeric) may be isolated following cell lysis in soluble form, or may be extracted using known techniques, e.g., in guanidine chloride. If the protein is secreted, it can be isolated from culture supernatant and purified. With an Fc bridging moiety, Protein A or Protein G Sepharose may be used to purify the immunogen. Where the immunogen is a receptor subunit sequence fused to a peptide epitope, a specific monoclonal antibody mAb to the peptide epitope can be used to purify the immunogen. Another method of producing the novel multimeric receptor immunogen involves directly injecting the monomeric recombinant DNA (as, e.g., "naked DNA") into mice or rabbits intramuscularly. The multimeric receptor thus assembles in vivo, where it acts as an immunogen. See, e.g., Cohen, Science. 259: 1691-92 (1993); E. F. Fynan et al, Proc. Natl. Acad. Sci.. USA.9_Q: 11478- 11482 (1993). Association of a nucleotide sequence encoding the selected receptor extracellular domain and its optional cleavage site with a non-peptide bridging moiety may be by conventional covalent or ionic bonds, using conventional chemical linking agents. If the association is non-covalent, then cross-linking must occur either after purification or in freshly isolated cells prior to purification. Alternatively, the opportunity to cross-link could be enhanced by adding ligand to the receptor sequences to bring them into proximity to each other, add cross-linking agent and bridging moiety, and dissociate ligand by a conventional technique, e.g., low pH. The dimeric receptor could then be purified. ///. The Method of the Invention The recombinant immunogens of this invention are thus useful as antigens for the development of anti-receptor antisera and antibodies to the multimeric receptor domain immunogen. Specific antisera and polyclonal antibodies may be generated by employing the recombinant multimeric immunogen as an immunogen using known techniques. See, Sambrook, cited above, Chapter 18, generally, incoφorated by reference. Additionally, polyclonal antibodies and antisera may be generated to the immunogen formed in vivo following administration of the naked DNA. The polyclonal antibodies developed in the immunized animal may be isolated from the animal's plasma, peripheral blood or other tissue in a conventional manner. Antibodies thus isolated may be employed in the methods described below for generation of mAbs, humanized and chimeric antibodies of the invention. For example, monoclonal antibodies of the invention may be produced by conventional methods, including the Kohler and Milstein hybridoma technique, in which spleen cells from an immunized animal are fused with immortalized cells to create hybridoma cell lines which secrete a single mAb. Each hybridoma is then screen with a simple binding assay to detect agonist properties. Other types of antibodies may be designed based on the agonist mAbs so identified. For example, recombinant techniques, such as described by Huse et al, Science. 246:1275-1281 (1988), or any other modifications thereof known to the art may be employed to generate antibodies. Thus, also encompassed within this invention are methods for generating humanized and chimeric agonist antibodies b employing the CDRs from the agonist antibodies produced as described above. Methods of identifying suitable human framework regions and modifying a mAb of the invention to contain same to produce a humanized or chimeric antibody of the invention, are well known to those of skill in the art. See, e.g., E. Mark and Padlin, "Humanization of Monoclonal Antibodies", Chapter 4, The Handbook of Experimental Pharmacology. Vol. 113, The Pharmacology of Monoclonal Antibodies, Springer- Verlag (June, 1994). Other types of recombinantly-designed antibodies are also encompassed by this invention. As used in this specification and the claims, the following terms are defined as follows: "Altered antibody" refers to a protein encoded by an altered immunoglobulin coding region, which may be obtained by expression in a selected host cell. Such altered antibodies are engineered antibodies (e.g., chimeric, humanized, reshaped human or reconstituted human antibodies) or antibody fragments lacking all or part of an immunoglobulin constant region, e.g., Fv, Fab, or F(ab')2 and the like. "Altered immunoglobulin coding region" refers to a nucleic acid sequence encoding the altered antibody of the invention. When the altered antibody is a "reshaped human antibody", the sequences that encode the complementarity determining regions (CDRs) from a donor human immunoglobulin are individually inserted into a first immunoglobulin partner comprising human variable framework or as components of a variable region gene sequence attached to human constant sequences. If desired, the first immunoglobulin partner is operatively linked to a second fusion partner. "First immunoglobulin partner" refers to a nucleic acid sequence encoding a human framework or human immunoglobulin variable region in which the native (or naturally-occurring) CDR-encoding regions are replaced by the CDR-encoding regions of a donor human antibody. The human variable region can be an immunoglobulin heavy chain, a light chain (or both chains), an analog or functional fragments thereof. Such CDR regions, located within the variable region of antibodies (immunoglobulins) can be determined by known methods in the art. For example Kabat et al. (Sequences of Proteins of Immunological Interest.4th Ed., U.S. Department of Health and Human Services, National Institutes of Health (1987)) disclose rules for locating CDRs. In addition, computer programs are known which are useful for identifying CDR regions/structures. "Second fusion partner" refers to another nucleotide sequence encoding a protein or peptide to which the first immunoglobulin partner is fused in frame or by means of an optional conventional linker sequence (i.e., operatively linked). Preferably the fusion partner is an immunoglobulin gene and when so, it is referred to as a "second immunoglobulin partner". The second immunoglobulin partner may include a nucleic acid sequence encoding the entire constant region for the same (i.e., homologous - the first and second altered antibodies are derived from the same source) or an additional (i.e., heterologous) antibody of interest. It may be an immunoglobulin heavy chain or light chain (or both chains as part of a single polypeptide). The second immunoglobulin partner is not limited to a particular immunoglobulin class or isotype. In addition, the second immunoglobulin partner may comprise part of an immunoglobulin constant region, such as found in a Fab, or F(ab)2 (i.e., a discrete part of an appropriate human constant region or framework region). A second fusion partner may also comprise a sequence encoding an integral membrane protein exposed on the outer surface of a host cell, e.g., as part of a phage display library, or a sequence encoding a protein for analytical or diagnostic detection, e.g., horseradish peroxidase, β-galactosidase, etc. The terms Fv, Fc, Fd, Fab, or F(ab')2 are used with their standard meanings (see, e.g., Harlow et al., Antibodies A Laboratory Manual. Cold Spring Harbor Laboratory, (1988)). As used herein, an "engineered antibody" describes a type of altered antibody, i.e., a full-length synthetic antibody (e.g., a chimeric, reconsituted human , or reshaped human antibody as opposed to an antibody fragment) in which a portion of the light and/or heavy chain variable domains of a selected acceptor antibody are replaced by analogous parts from one or more donor antibodies which have specificity for the selected epitope. For example, such molecules may include antibodies characterized by an engineered heavy chain associated with an unmodified light chain (or chimeric light chain), or vice versa. Engineered antibodies may also be characterized by alteration of the nucleic acid sequences encoding the acceptor antibody light and/or heavy variable domain framework regions in order to retain donor antibody binding specificity. These antibodies can comprise replacement of one or more CDRs (preferably all) from the acceptor antibody with CDRs from a donor antibody described herein. A "chimeric antibody" refers to a type of engineered antibody which contains naturaUy-occurring variable region (light chain and heavy chains) derived from a donor antibody in association with light and heavy chain constant regions derived from an acceptor antibody from a heterologous species. A "humanized antibody" refers to a type of engineered antibody having its CDRs derived from a non-human donor immunoglobulin, the remaining immunoglobulin-derived parts of the molecule being derived from one (or more) human immunoglobulin(s). In addition, framework support residues may be altered to preserve binding affinity (see, e.g., Queen et al., Proc. Nat'l. Acad. Sci. USA. £6 10029-10032 (1989), Hodgson et al.. BioTechnologv. 9:421 (1991)). The term "reconstituted human antibody" refers to an antibody in which a Fab is converted into a full length Mab by cloning the heavy chain of the Fab into a human lg constant region comprising the hinge region and CH-2 and CH-3 domains. Preferrably the constant region is one of the IgG isotypes IgGl- IgG4 or variants thereof such as PE muatations. A reconstituted human antibody also includes variants of the processes, mature NH. terminal regions of the light or heavy chain are altered to conform with the predicted germ line parent sequence. The term "donor antibody" refers to an antibody (monoclonal, or recombinant) which contributes the nucleic acid sequences of its variable regions, CDRs, or other functional fragments or analogs thereof to a first immunoglobulin partner, so as to provide the altered immunoglobulin coding region and resulting expressed altered antibody with the antigenic specificity and neutralizing activity characteristic of the donor antibody. One donor antibody suitable for use in this invention is 1C8. The term "acceptor antibody" refers to an antibody (monoclonal, or recombinant) from a source genetically unrelated to to the donor antibody, which contributes all (or any portion, but preferably all) of the nucleic acid sequences encoding its heavy and/or light chain framework regions and/or its heavy and/or light chain constant regions to the first immunoglobulin partner. Preferably a human antibody is the acceptor antibody. "CDRs" are defined as the complementarity determining region amino acid sequences of an antibody which are the hypervariable regions of immunoglobulin heavy and light chains. See, e.g., Kabat et al., Sequences of Proteins of Immunological Interest.4th Ed., U.S. Department of Health and Human Services, National Institutes of Health (1987). There are three heavy chain and three light chain CDRs (or CDR regions) in the variable portion of an immunoglobulin. Thus, "CDRs" as used herein refers to all three heavy chain CDRs, or all three light chain CDRs (or both all heavy and all light chain CDRs, if appropriate). CDRs provide the majority of contact residues for the binding of the antibody to the antigen or epitope. CDRs of interest in this invention are derived from donor antibody variable heavy and light chain sequences, and include analogs of the naturally occurring CDRs, which analogs also share or retain the same antigen binding specificity and/or neutralizing ability as the donor antibody from which they were derived. By "sharing the antigen binding specificity or neutralizing ability" is meant, for example, that although antibody such as 1C8 may be characterized by a certain level of antigen affinity, a CDR encoded by a nucleic acid sequence of 1C8 in an appropriate structural environment may have a lower, or higher affinity. It is expected that CDRs of 1C8 in such environments will nevertheless recognize the same epitope(s) as in 1C8. A "functional fragment" is a partial heavy or light chain variable sequence (e.g., minor deletions at the amino or carboxy terminus of the immunoglobuUn variable region) which retains the same antigen binding specificity and/or neutraUzing abUity as the antibody from which the fragment was derived. An "analog" is an amino acid sequence modified by at least one amino acid, wherein said modification can be chemical or a substitution or a rearrangement of a few amino acids (i.e., no more than 10), which modification permits the amino acid sequence to retain the biological characteristics, e.g., antigen specificity and high affinity, of the unmodified sequence. For example, (silent) mutations can be constructed, via substitutions, when certain endonuclease restriction sites are created within or surrounding CDR-encoding regions. Analogs may also arise as aUeUc variations. An "alleUc variation or modification" is an alteration in the nucleic acid sequence encoding the amino acid or peptide sequences of the invention. Such variations or modifications may be due to degeneracy in the genetic code or may be deUberately engineered to provide desired characteristics. These variations or modifications may or may not result in alterations in any encoded amino acid sequence. The term "effector agents" refers to non-protein carrier molecules to which the altered antibodies, and/or natural or synthetic Ught or heavy chains of the donor antibody or other fragments of the donor antibody may be associated by conventional means. Such non-protein carriers can include conventional carriers used in the diagnostic field, e.g., polystyrene or other plastic beads, poiysaccharides, e.g., as used in the BIAcore (Pharmacia) system, or other non-protein substances useful in the medical field and safe for administration to humans and animals. Other effector agents may include a macrocycle, for chelating a heavy metal atom, or radioisotopes. Such effector agents may also be useful to increase the half-Ufe of the altered antibodies, e.g., polyethylene glycol. Also provided by the invention are human antibodies derived from human hybridomas, antibodies obtained by rescue from transgenic mice expressing human lg domains, and antibodies made in primates. Any other modifications which are known to be useful to prepare mAbs as pharmaceutical agents may also be made to the antibodies of this invention. Without wishing to be bound by theory, it is anticipated that the recombinant immunogens of this invention have configurations mimicking the form of the multimeric receptor on the cell surface. Thus, these immunogens generate a higher frequency of antibodies which crosslink the multiple receptor subunits in a manner similar to that of the naturally occurring Ugand and thereby are more likely than randomly obtained antibodies to be agonists of the receptor. TV. Utilities Polyclonal antisera, monoclonal antibodies and other antibodies of this invention, which bind to the novel immunogen as the antigen and can function as agonists are useful in substantially the same manner as is the naturally occurring Ugand of the receptor. For example, an agonist antibody developed to the exemplary erythropoietin receptor dimeric fusion protein described in Example 2 may be used in therapeutic, diagnostic and research methods in which the Ugand, erythropoietin, is useful. These antibodies may be used as research tools and as components for separation of the receptor proteins from other contaminants of Uving tissue, for example, are also contemplated for these antibodies. Agonist antibodies to the receptor would have the same therapeutic utiUty as the natural Ugand, but would have the advantage of longer half-life and hence prolonged activity in vivo. These agonists can thus be employed to activate the biological activity which results from receptor/Ugand binding. Thus, these agonist antibodies are useful in the treatment of diseases in which the interaction of the receptor and its ligand is part of a biochemical cascade of events leading to a desired response. The advantages of such agonist antibodies include the abiUty to administer lower dosages of antibody than Ugand, easier and less frequent administration of a pharmaceutic based on the agonist antibody, as well as easier purification. Agonist antibodies may demonstrate a different profile of activity in vivo than the non-agonist antibodies due to a different distribution. Compositions and methods useful for the treatment of conditions associated with abnormal receptor or ligand levels are provided. The present invention provides pharmaceutical compositions useful in the treatment of :anemia associated with chronic renal failure; anemia associated with AIDS; pre-dialysis patients; patients in need of pre- and/or post surgery hematocrit boosting; cancer patients undergoing hematocrit decreasing radiation or chemotherapy; rheumatoid arthritis and sickle ceU anemia. These compositions contain a therapeutically effective amount of an agonist antibody of this invention and an acceptable pharmaceutical carrier. As used herein, the term "pharmaceutical" includes veterinary appUcations of the invention. The term "therapeutically effective amount" refers to that amount of a receptor agonist antibody, which is useful for alleviating a selected condition. Also provided are compositions and methods for inhibiting receptor activity in order to ameUorate an undesired response. The receptor agonist antibodies of the invention can be formulated into pharmaceutical compositions and administered in the same manner as described for mature proteins [see, e.g., International Patent Apphcation, PubUcation No. WO 90/02762 (Mar. 22 1990)]. These therapeutic compositions of the invention may be administered to mimic the effect of the normal receptor Ugand. These compositions may contain a pharmaceuticaUy acceptable carrier. Suitable carriers are weU known to those of skill in the art and include, for example, saline. Alternatively, such compositions may include conventional deUvery systems into which protein of the invention is incorporated. Optionally, these compositions may contain other active ingredients, e.g., chemotherapeutics. Thus, the invention also provides improved methods of treating a variety of disorders in which receptor/Ugand interactions are implicated, e.g., inflammation, autoimmune disorders, etc. For example, an agonist antibody developed to a dimeric EpoR of this invention can be employed to treat acute renal failure, anemia, AIDS, and any disorder which the Ugand erythropoietin can be used for treatment, e.g., for cancer chemotherapy. Similarly, an agonist antibody developed to a dimeric TpoR receptor may be employed to treat conditions of low platelet count, i.e., patients undergoing chemotherapy for cancer, etc. An agonist antibody developed to the G-CSF dimeric receptor of this invention is useful to stimulate the polymoφhonuclear ceUs, thereby for the treatment of conditions characterized by neutropenia, e.g., cancer chemotherapy, etc. The invention encompasses methods of administering therapeutically effective amounts of a antibody or pharmaceutical composition of the invention to a patient. The dose, timing and mode of administration of these therapeutic or gene therapy compositions may be determined by one of skill in the art, and may be less than or equal to the amounts of the ligand known to be aσministered for similar conditions. Such factors as the disease being treated, the age, physical condition, and the level of the receptor detected by the diagnostic methods described above, may be taken into account in deterrnining the dose, timing and mode of administration of the therapeutic compositions of the invention. Generally, where treatment of an existing disorder is indicated, a therapeutic composition of the invention is preferably adrninistered in a site-directed manner and is repeated as needed. Such therapy may be administered in conjunction with conventional therapies for such conditions. Generally, an agonist antibody of the invention is administered in an amount between about 0.01 ng/kg body weight to about 1 g/kg and preferably about 0.01 ng/kg to 100 mg/kg per dose. Preferably, these pharmaceutical compositions are adrninistered to human or other mammalian subjects by injection. However, administration may be by any appropriate internal route, and may be repeated as needed, e.g., as frequently as one to three times daily for between 1 day to about three weeks to once per week or once biweekly. Preferably, the agonist antibody is administered less frequently than is the Ugand, when it is used therapeuticaUy. Optionally, the pharmaceutical compositions of the invention may contain other active ingredients or be administered in conjunction with other therapeutics. Suitable optional ingredients or other therapeutics include those conventional for treating conditions of this nature, e.g. other anti-inflammatories, diuretics, and immune suppressants, among others. According to the methods of this invention, and as described in detail in the following examples, antibodies were generated to the erythropoietin receptor (EpoR), which mimic the agonist properties of erythropoietin. The foUowing examples illustrate the construction and expression of exemplary multimeric receptor proteins of the invention. These examples are illustrative only and do not limit the scope of the invention. Example 1 - Multimeric EpoR Antigen A dimeric antigen of this invention was designed by fusing the extraceUular domain of the erythropoietin receptor via an amino acid Unker to the Fc portion of a human immunoglobulin, and expressing the fusion protein in a suitable host ceU. Using the foUowing primers sets based on the pubUshed nucleotide sequence of EpoR (Jones et al, Blood. 76: 31-35 (1990)), the extraceUular domain of the EpoR was ampUfied via PCR from a human fetal Uver cDNA Ubrary (Clontech). One primer was selected from: 5' GT ATC ATG GAC CAC CTC GGG GCG TCC CTC TGG CCC CAG 3' [SEQ ID NO: 4] and 5' ATG GAC CAC CTC GGG GCG TCC CTC TGG CCC CAG 3' [SEQ ID NO: 5]. A second primer was selected from: 3' GGA GAC GGG GGG TCG ATA CAC CGA ACG AGA ATC CTG TG 5' [SEQ ID NO: 6] and 3' GGA GAC GGG GGG TCG ATA CAC CGA ACG AGA ATC 5' [SEQ ID NO: 7]; 3" CAC AGC GAC GAC TGC GGA TCG CTG GAC CTG GGG ate act ga 5' [SEQ ID NO: 8] and 3' CAC AGC GAC GAC TGC GGA TCG CTG GAC CTG GGG gtc 5' [SEQ ID NO: 9]. The resulting 250 bp DNA fragment so isolated was cloned into the vector PCR2000 (Invitrogen) and sequenced. The EpoR fragment was found to encode amino acids 1-250 [SEQ ID NO: 2] of the extracellular domain of the human EpoR [Jones et al, cited above; SWISSPROT Accession number P19235]. An Spel/Xbal fragment was isolated from the PCR2000-derived vector by digestion containing this EpoR insert, nucleotide 898 to 1647 of SEQ ID NO: 1. The insert was then cloned into the Drosophila S2 vector mtal [see, European Patent No. 290,261 B, pubUshed November 9, 1988] at the equivalent Unker sites, Spel and Xbal. The resulting plasmid vector, pS2EpoR, contains the EpoR extracellular domain gene insert under the control of the Drosophila copper metallothionein (mtn) promoter [Johansen et al, Genes and Development. 3_:882-889 (1989); AngeUchio et al, Nucl. Acid Res..19:5037-5043 (1991)]. The plasmid pS2EpoR was digested with B_s§H2 and Xbal and a C terminal fragment of the EpoR sequence was removed by this digestion. A plasmid containing the whole EpoR gene fused to a bridging moiety was then prepared by cloning the foUowing three fragments: ( 1 ) the large BssH2/XbaI fragment from the above digestion; (2) a synthetic BssH2/KpnI Unker, which spanned nucleotide 1561 to nucleotide 1659 of SEQ ID NO: 1 , which encoded the C terminus of the EpoR extraceUular domain, aa 222 to 250 of SEQ ID NO: 2, linked in frame to the four amino acid recognition sequence for protease Factor Xa cleavage (DeGluGlyArg) [amino acids 251 to 254 of SEQ ID NO: 2], and (3) a KpnI/Xbal fragment containing the human IgGl Fc region, spanning nucleotide 1660 to the Xbal site which appears at nucleotides 2371-2376 of SEQ ID NO: 1 [see, also Johansen et al, J. Biol. Chem..270:9459-9471 (1995)]. This KpnI/Xbal fragment was constructed as foUows: Human IgGl cDNA encoding CHI, the hinge, CH2 and CH3 described by J. EUison et al, Nucleic Acids Res..10: 4071-4079 (1982) was cloned from the human IgG plasma ceU leukemia ARH-77 (American Type Tissue CoUection), using RT-PCR. This cDNA was fuUy sequenced to confirm identity with the pubUshed sequence [see, International patent publication WO 92/00985]. This sequence was inserted into a pUC18 vector (pUC18-Fc). This vector was digested with Kpnl and SacU, deleting the CHI, hinge and part of CH2. The deleted region was replaced with a PCR amplified fragment containing the hinge-CH2 region as foUows. Using the foUowing PCR primers: 5' TCG AGC TCG GTA CCG AGC CCA AAT CGG CCG ACA AAA CTC ACA C 3' [SEQ ID NO: 10] and 5' GTA CTG CTC CTC CCG CGG CTT TGT CTT G 3' [SEQ ID NO: 11], a DNA fragment containing the hinge-CH2 region was ampUfied from pUC18-Fc, digested with Kpnl and SacU. gel purified and cloned back into the Kpnl/SacJJ. digested pUC18-Fc vector. The Cys, which occurs at position 230 [Kabat numbering; Kabat et al, "Sequences of Proteins of Immunological Interest, 5th Edition, US Department of Health and Human Services, NIH Publication No. 91-3242 (1991); this is also residue 5 of the hinge of the IgGl heavy chain; residue 261 of SEQ ID NO: 2] was altered to an Ala through a TGT to GCC substitution in the nucleotide sequence to avoid having the unpaired Cys present which is usually involved in Ught chain-heavy chain crossUnking. An altered DNA sequence in one of the PCR primers introduced a unique Kpnl site at the 5' end of the hinge. The resulting plasmid was caUed pUC18Fcmod, and the junctions and PCR amplified region were sequenced for confirmation. The entire hinge-CH2-CH3 insert in pUClδ-Fcmod was removed in a single DNA fragment with Kpnl and Xbal. gel purified, and Ugated into SFcRlCos4 cut with Kpnl and Xbal to create COSFc. SFcRlCos4 is a derivative of pST4DHFR [K. Deen et al, Nature. 331: 82 (1988)] and contains the soluble Fc receptor type I (sFcRl) inserted between the cytomegalovirus (CMV) promoter and bovine growth hormone (BGH) polyadenylation regions, and also contains the dihydrofolate reductase (DHFR) cDNA inserted between the b-globin promoter and S V40 polyadenylation regions, an SV40 origin of repUcation, and an ampicillin resistance gene for growth in bacteria. Cutting the vector with Kpnl and Xbal removes the sFcRl coding region, so that the COSFc vector contains the hinge-CH2-CH3 region inserted between the CMV promoter and BGH polyA regions. The COSFcLink vector was made from COSFc by inserting an oUgonucleotide Unker at the unique EcoRI site of the vector, which recreates this EcoRI site, and also introduces BstEU, PstI and EcoRV cloning sites. The oligonucleotides used were: 5' AATTCGGTTACCTGCAGATATCAAGCT 3' [SEQ ID NO: 12] and 3' GCCAATGGACGTCTATAGTTCGATTAA 5' [SEQ ID NO: 13]. The junction was sequenced to confirm orientation in the vector. The size of the final vector is 6.37 kb and is reported as SEQ ID NO: 3. The KpnI Xbal fragment used in the dimeric immunogen described herein was obtained from COSFcLink. The resulting plasmid DNA construct containing the three fragments described above was called pmtalsEpoRFc [SEQ ID NOS: 1 and 2]. The plasmid sequence contains the heterologous fusion sequence comprising an intact EpoR extraceUular domain encoding amino acids 1-250 of SEQ JD NO: 2 Unked via a four amino acid Unker (aa 251-254 of SEQ ID NO: 2) to a human IgGl Fc region (aa 255 to 488 of SEQ ID NO: 2). In the plasmid, the fusion sequence was under the control of the mtn promoter, described above. Plasmid pmtalsEpoFc was cotransfected into Drosophila S2 ceUs with a vector encoding hygromycin resistance [see, EP No. 290,261B, cited above]. Stable co-transfectants were selected in hygromycin, and expression of the EpoR induced by Q12SO4 according to published protocols [Johansen et al, cited above; AngeUchio et al, cited above]. The co-transfected cells secreted the EpoRFc protein as a dimeric molecule due to the natural affinity of the Fc sequence for itself. Under reducing conditions in SDS-PAGE, the EpoRFc protein ran as a monomer. The dimeric protein was purified from Drosophila medium by passage over a Protein A Sepharose column. To obtain the monomeric EpoR extraceUular protein apart from its Fc fusion, the EpoRFc fusion protein is treated as follows: EpoR-Fc was dialyzed into 20 mM Tris, 100 mM NaCl, 2 mM CaCl2, pH 8. Factor Xa (New England Biolabs) was added at a ratio of 1 mg Factor Xa per 25 mg EpoR-Fc and incubated at 6°C for 18- 20 hours. The digest was then added to Protein A Sepharose 4 Fast Flow [Pharmacia], washed with 100 mM Tris, pH 8, giving a ratio of 0.5 ml packed resin per mg protein. FoUowing a 90 minute incubation with mixing, at 6°C, the resin was separated from the supernatant by centrifugation. SDS/PAGE and Western blots showed that EpoR, free of Fc, was present in the supernatant. The N-terminal sequence for EpoR was correct. The final product was sterile filtered. Example 2 - Erythropoietin Binding Assay The activity of the dimeric fusion protein EpoRFc and the monomeric single- stranded mEpoR protein cleaved from EpoRFc were tested in various biological assays by their abUity to neutralize the activity of erythropoietin (Epo). A. Inhibition of Epo-induced proliferation ofUT7-Epo Cells An assay for the measurement of Epo activity on the proUferation of UT7Epo ceUs, which are dependent on Epo for growth [Komatsu et al, Blood. 82:456-464 (1993)] was performed as foUows. The Epo used in the experiment is Epogen (2000 U/ml) [Amgen, Thousand Oaks, Ca], diluted in phosphate buffered saline (PBS) and human serum albumin (HSA) for storage at 4°C at 200 U/ml. DUutions of cleaved EpoR or EpoRFc protein samples were made, so that final concentrations ranged from 0.001 to 100 ng/ml. Samples of either EpoR or EpoRFc were added to weUs at 10 ul weU in quadrupUcate. Epo (0.2 U/ml) was added to each weU. UT7Epo ceUs (1 x 10^ ceUs/ml) were plated at 100 ul/weU. After the plates were incubated at 37°C for three days, 10 ul/weU of 3 H-thymidine (diluted to 100 mCi/ml in IMDM+10% fetal calf serum (FCS)) were added to a final concentration of 10 uCi/ml. Plates were incubated at 37°C for four hours with 3H-thymidine. The 96-well plates were harvested onto glass fiber filters using the Tomtec plate harvester with 10% cold TCA and cold 95% ethanol. SoUd scintillant was melted onto the filters and the samples counted. The mean and standard error of quadrupUcate samples was determined. The data were reported as the percent of positive (0.2 U/ml) Epo control and are illustrated in Fig. 1. B. Inhibition of Epo-induced proliferation of32D/Epo wt Cells Another assay was performed for the measurement of Epo activity on the proliferation of 32D/Epo wt cells (Miura, O. et al, Mol. Cell. Biol..13: 1788-1795 (1993)). 32D/Epo wt is an IL-3 dependent ceU line transfected with the human Epo receptor. This assay is performed as described in Part A above, with the modification that the each well contains 1 U/ml Epo. The results of this assay are illustrated in Fig. 2. C. Inhibition of Epo-induced CFU-E colony formation A third assay for measuring the abiUty of Epo to stimulate the differentiation of murine bone marrow ceUs to hemoglobin producing mature erythrocytes (CFU-E assay) was performed as described below. Murine bone marrow ceUs were flushed from the femur of female B2D6F1 mice. The marrow ceUs (1 x 10^ cells/ml final concentration) were mixed with IMDM, 25% FCS (final) and methylceUulose (0.8 % final). 0.4 ml ceUs was plated per well of 24-well TC plate. EpoRFc (40 ul/weU) samples were added and Epo (1 U/ml) was added to each weU. Plates were incubated at 37°C, 5% CO2, 6% O2 for two days. CFU-E colonies containing 8 or more red ceUs were counted. The mean and standard error of tripUcate samples were determined and data reported as the percent of the positive ( 1 U/ml) Epo control. The results of this assay are iUustrated in Fig. 3. In all three assays, both the monomeric extraceUular domain protein EpoR and the dimeric fusion protein EpoRFc were able to bind, and thereby neutraUze, the biological activity of the ligand Epo. However, the dimeric fusion protein EpoRFc was consistently 10 to 100 fold more effective at neutralizing Epo activity than non-fused, monomeric extraceUular domain protein EpoR, suggesting that the dimeric antigen had a higher affinity to the natural Ugand, Epo. The assay results also confirm that the dimeric fusion protein mimics the ceU surface form of the natural EpoR in being able to bind to Epo with greater affinity than the mEpoR domain protein. Example 3 - Agonist Antibodies of the Invention A. Generation of Hybridomas Mice were immunised s.c. with recombinant EpoRFc (34ug) in Freund's complete adjuvant and then boosted i.p.4 weeks later (34ug) with Freund's incomplete adjuvant. One and three days before fusion mice received 20ug in PBS i.p.. The spleens were harvested and fused with myeloma ceUs according to the method described in Zola. ( Monoclonal Antibodies : A Manual of Techniques, Zola H. ed., Boca Raton, FI : CRC Press, 1987) Positive hybridomas were selected through a primary screen described below. Positives were rescreened using a competive immunoassay and then BIAcore was used to select hybridomas that expressed high affinity monoclonal antibodies which were then cloned twice by the limiting dilution method. Al. Primary Screening assay of anti EpoRFc Hybridomas 96 well microtitre plates were coated with lOOul well of EpoRFc at 0.5ug/ml in coating buffer (50mM Na2HPO4, 150mM NaCl, 0.02% v/v Kathon, pH 7.4) and incubated overnight at 4°C. The weUs were aspirated and 250ul well blocking buffer ( 1 % w/v BSA, 50mM Tris, 150mM NaCl, 0.1 % v/v Kathon, pH 7.4) added for 1 hour at 37°C. The wells were washed X4 with wash buffer (lOmM Tris, 150mM NaCl, 0.05% Tween 20, pH 7.4) and 50ul/well of 40ug/ml human IgG diluted in assay buffer (0.5% w/v BSA, 0.05% w/v bovine γ globulin, 50mM Tris, 150mM NaCl, 7.86mg/L DTPA, O.lg L Tween-40, 0.02% v/v Kathon, pH 7.4) added foUowed by 50ul hybridoma supernatant. The plates were incubated for 1 hour at 37°C on a plate shaker, the weUs washed X4 and then lOOul weU Europium conjugated anti-mouse IgG added (0.5ug/ml in assay buffer). After incubation for 1 hour at 37°C on the plate shaker the weUs were again washed X4 and lOOul/weU of enhancement solution added into each weU and incubated for 2 min at 22C on the plate shaker and the counts read on a Delfia plate reader. A2. Isolation of Hybridomas Producing High Affinity Antibodies that Recognise Solution Phase EpoRFc using a competitive immunoassay. Microtitre plates were coated with EpoRFc and blocked as above. The weUs were washed X4 and then 50ul of either EpoRec at 6ug/ml diluted in assay buffer or 50ul human IgG at 40ug/ml diluted in assay buffer or 50ul assay buffer alone were added foUowed by 50ul hybridoma supernatant. After incubation for 1 hour at 37°C on the plate shaker the weUs were washed X4 foUowed by addition of lOOul/weU Europium conjugated anti-mouse IgG at 0.5ug/ml (diluted in assay buffer). After incubation for 1 hour at 37°C on the plate shaker the wells were again washed X4 and lOOul well of enhancement solution added into each weU and incubated for 2 min at 22°C on the plate shaker and the counts read on a Delfia plate reader. Positive antibodies would be displaced by solution phase EpoRFc and these would thus show a reduction in counts when compared to weUs with only assay buffer, antibodies giving a reduction in counts with human IgG would be non specific. High affinity antibodies would show >80% reduction in counts. A hybridoma designated herein as 1C8 (or alternatively as 5-1C8) has been deposited at the European Collection of Animal CeU Cultures, Porton Down, Salisbury, Wiltshire, SP4 OJG United Kingdom on 5 June 1996 and assigned provisional Accession number 96060519. The deposit referred to herein wiU be maintained under the terms of the Budapest Treaty on the International Recognition of the Deposit of Micro-organisms for purposes of Patent Procedure. These deposits are provided merely as convenience to those of skiU in the art and are not an admission that a deposit is required under 35 U.S.C. § 112. The sequence of the polynucleotides contained in the deposited material, as well as the amino acid sequence of the polypeptides encoded thereby, are incoφorated herein by reference and are controlling in the event of any conflict with any description of sequences herein. A Ucense may be required to make, use or seU the deposited material, and no such Ucense is hereby granted. A3. Binding Analysis in the BIAcore for the Selection of Antibodies that Bound EpoR with High Affinity Rabbit anti-mouse Fc (RAMFc) was immobiUsed to the sensor chip surface (Pharmacia Biosensor protocol) and used as a capture antibody. The run buffer used was lOmM HEPES, 150mM NaCl, 3.4mM EDTA, 0.005% (v/v) Surfactent P 20 at a flow rate of 5ul/min. 20ul hybridoma supernatant was injected over the sensor chip surface foUowed by 20ul EpoR or EpoRFc (3ug/ml diluted in run buffer). The surface was regenerated by injection of 15ul HCL (lOOmM) and then lOul SDS (0.025%). High affinity monoclonal antibodies were selected on the basis of a fast on rate and slow off rate with respect to EpoR binding. B. Assays to Test Agonist Characteristic of Antibodies The hybridoma supernatants or purified antibodies were then tested for their ability to bind to the naturaUy occurring EpoR on UT7 or 32D/Epo wt ceUs in flow cytometry as follows. 5 x 10^ ceUs per sample of 32D/Epo wt or UT7-Epo ceUs were resuspended in 50 ul PBS/10%BSA. 5.0 ul of each purified anti-EpoRFc was diluted to 30ug/ml and incubated on ice for 45 minutes. Cells were washed and resuspended in 50 ul PBS/10% bovine serum albumin (BSA) and 7 ul FTTC-labelled goat anti-mouse IgG (Fab')2 [Tago] added for 45 minutes on ice. Cells were again washed in PBS/10%BSA and resuspended in 0.4 ml PBS/10% BSA and then 0.2 ml 3.2% paraformaldehyde added foUowed by vortexing. CeUs were stored at 4°C until analysis on Becton-Dickinson's FACScan fluorescence activated ceU sorter. The data, illustrated in Figure 4, was reported as the % of control antibody fluorescence. As can be seen, four antibodies stained UT7Epo ceUs whUe three did not. Interestingly, only one of the four positive antibodies on UT7Epo ceUs was able to recognize the transfected human Epo receptor in 32D/Epo wt cells, suggesting some differences in the disposition of the Epo receptor in these cell Unes. This also suggests differences in the epitopes recognized by these antibodies. C. Assays to Test agonist activity of antibodies. (1) Hybridoma supernatants or purified antibodies were tested for their abiUty to mimic the activity of Epo by stimulating the proUferation of UT7-Epo ceUs in an assay performed as described in Example 2A above, with the modification that Epo is absent from weUs containing the hybridoma supernatants. The only sample was dilutions of the monoclonal antibodies against EpoRFc dimeric protein. Results of this assay are shown in Figure 5 for some purified EpoR reactive monoclonal antibodies. Four of the antibodies gave significant proliferative activity, in one case approaching that of Epo itself (1C8). The variabUity of the extent of peak activity relative to Epo suggests that the way in which the antibodies bind may be an important determinant of activity. (2) Hybridoma supernatants or purified antibodies were tested for their abUity to mimic the activity of Epo by stimulating the proUferation and differentiation of human bone marrow progenitor ceUs to form red blood ceU colonies (CFU-E) similar to the assay described above in Figure 6 . The present assay differed in that the progenitor cells were of human origin. In this procedure, Ught density ceUs from human bone marrow centrifuged over Histopaque 1077 were washed and resuspended at 2.5 x 10 6 ceUs/ml in X-vivo medium (BioWhittaker). The purified monoclonal antibodies were diluted in X-vivo medium, and the Epo positive control was 4 U/ml. For the assay, 0.3 ml cells, 0.3 ml Mab sample (or Epo control) and 0.7 ml X-vivo medium were incubated in a polypropylene tube for 30 min at RT, then 0.9 ml FCS, 0.3 ml 10% BSA and 0.8 ml 3.2% methylceUulose were added. 0.4 ml were plated per weU of a 24-weU TC dish (Nunc). This procedure departs from the standard assay in the pre-incubation of ceUs, X-Vivo and Mab alone for 30 min (without serum, BSA or methylceUulose) prior to plating in methylceUulose. The results are shown in Figure 6. Once again, aU four antibodies were positive in the UT7Epo proUferation assay were also able to stimulate the generation of mature red blood cells. Again the most potent was antibody 1C8 which gave almost 50% of the maximal activity of human Epo on the same cells. The order of maximal activity was siπ lar to that observed in the proliferative assay. D. Epitope mapping of agonist antibodies. It was likely that one contributor to the different activities of the agonist antibodies was the epitope recognized on the erythropoieitin receptor. To determine if the antibodies recognized overlapping epitopes on the Epo receptor, the abiUty of antibodies to compete with each other in binding to EpoR or EpoRFc was measured. RAMFc was immobiUsed to the sensor chip surface and using a flow rate of 5ul/min the foUowing sequential injections were used. 5ul of first monoclonal antibody (25 or 30ug/ml), lOul EpoR (5ug/ml) or EpoRFc (6ug/ml), 2 X 5ul of nonspecific monoclonal antibodies, (lOOug/ml each of IgG 2bk, IgG 3k, IgG Ik and IgG 2ak), 5ul of second monoclonal antibody. The surface was regenerated with 15ul 0. IM phosphoric acid and 8ul 0.025% SDS at lOul/min. The data are shown in Table I. Table I Competition of different monoclonal antibodies for epitopes on Epo receptor as measured by BIAcore. Results are expressed as Response Units. The antibody attached to the chip via protein A is shown in the left hand column and each row shows the binding of each monoclonal after prebinding of EpoR or EpoRFc. Epo-R Measurements are in RU 5-1C8 3-2B6 5-2G6 5-1C8 -25 -21 2 3-2B6 -3 -6 269 5-2G6 -13 169 - Epo- RFc Measurements are in RU 5-1C8 3-2B6 5-2G6 5-1C8 -9.6 6.3 5.2 3-2B6 -7 -8 272 5-2G6 -11.6 167 -5 The data indicate that of the three agonist antibodies, 2B6 and 2G6 bind to two non-overlapping epitopes since they do not compete for binding to the Epo receptor. In contrast, 1C8 competes with both 2B6 and 2G6, suggesting that it binds to a third distinct epitope which overlaps the other two. Thus there is no single epitope which can lead to agonist activity, but the precise epitope can very likely affect the extent of bioactivity observed. Use of the EpoRFc as antigen seems to generate a wide variety of agonist epitopes. E. Competition of antibody binding with Epo. Another measure of differences between the agonist antibodies is provided by studies which measure the abiUty of monoclonal antibody to compete with Epo binding to the receptor. These experiments were conducted in two ways. First, a goat anti-human IgG was attached to the BIAcore chip, followed by sequential binding of EpoRFc, Epo and finaUy monoclonal antibody. In this experiment, pre-binding of Epo blocked the binding of 1C8 by more than 75%, but had only a limited effect on the binding of 1D9, 2G6 and 2B6. Second, if the EpoRFc binding to the chip was foUowed first by monoclonal antibody and then by Epo, aU four monoclonal antibodies could block subsequent binding of Epo. More specifically, a goat anti- human IgG, Fc specific antibody was immobUised on the sensor chip surface. Injection of 25ul EpoRFc (2ug/ml) at 5ul/min was followed by injection of 25ul Epo ( 5ug/ml) then 25ul Mab (lOug/ml) at 5ul/min. RU recorded. The surface was regenerated with injections of 15ul 0.1M phosphoric acid (5ul/min) and 8ul 0.025% SDS at lOul/min. and as mentioned above the experiment was repeated reversing the order of addition for Epo and mAb, i.e inject Mab first , then displaced with Epo. These data, shown in Table II suggest that all four antibodies may block access of Epo to its binding site, but only the 1C8 antibody overlaps substantiaUy with the Epo binding site on the Epo receptor. Table π Competition of monoclonal antibody binding with Epo binding to Epo receptor as measured by BIAcore. The order of addition is left to right as indicated. The identity of each monoclonal antibody is listed in the left column. F. Affinity of the monoclonal antibodies to the Epo receptor The binding kinetics and affinities of the agonist antibodies was determined by measurements in the BIAcore with both the soluble EpoR and with the dimeric EpoRFc. Specifically, RAMFc was immobUised to the sensor chip surface and a flow rate of 5ul/rnin was used with run buffer. The Mab was first bound to the RAMFc (5ul injection) foUowed by a 20ul injection of of EpoR (0-4ug/ml) or EpoRFc (0-6ug/ml) then buffer flow for 120 sec and regeneration with 15ul 0.1M phosphoric acid and 8ul 0.025% SDS at lOul/min. The four antibodies showed quite different kinetics and binding constants as listed in Table D3„ Table JJJ Affinities and kinetics of binding of monoclonal antibodies to Epo receptor as measured by BIAcore. On the monomeric EpoR, the affinities ranged between 0.75nM and 23nM. Interestingly, the most biologically potent antibody, 1C8, had the lowest dissociation constant of 23nM , and also had a second binding mode with a dissociation constant of 4.3nM. It was the only antibody to show this phenomenon. In contrast, with the dimeric receptor EpoRFc, aU four antibodies had non-measurable dissociations, suggesting dissociation constants of less than 500pM. These data suggest that kinetics may also play a role in the relative agonist activity of different monoclonal antibodies. AU documents cited above are incoφorated herein by reference. Numerous modifications and variations of the present invention are included in the above- identified specification and are expected to be obvious to one of skiU in the art. Such modifications and alterations to the compositions and processes of the present invention are beheved to be encompassed in the scope of the claims appended hereto. SEQUENCE LISTING (1) GENERAL INFORMATION: (i) APPLICANT: Young, Peter R. Erickson-Miller, Connie (ii) TITLE OF INVENTION: Method for Obtaining Receptor Agonist Antibodies (iii) NUMBER OF SEQUENCES: 13 (iv) CORRESPONDENCE ADDRESS: (A) ADDRESSEE: SmithKline Beecham Corporation- Corporate Patents (B) STREET: 709 Swedeland Road (C) CITY: King of Prussia (D) STATE: Pennsylvania (E) COUNTRY: USA (F) ZIP: 19406-2799 (v) COMPUTER READABLE FORM: (A) MEDIUM TYPE: Floppy disk (B) COMPUTER: IBM PC compatible (C) OPERATING SYSTEM: PC-DOS/MS-DOS (D) SOFTWARE: Patentin Release #1.0, Version #1.30 (vi) CURRENT APPLICATION DATA: (A) APPLICATION NUMBER: US (B) FILING DATE: (C) CLASSIFICATION: (viii) ATTORNEY/AGENT INFORMATION: (A) NAME: Jervis, Herbert H. (B) REGISTRATION NUMBER: 31,171 (C) REFERENCE/DOCKET NUMBER: SBC P50349-1 (ix) TELECOMMUNICATION INFORMATION: (A) TELEPHONE: 610-270-5015 (B) TELEFAX: 610-270-5090 (2) INFORMATION FOR SEQ ID NO:l: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 4990 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (ix) FEATURE: (A) NAME/KEY: CDS (B) LOCATION: 898..2361 (xi) SEQUENCE DESCRIPTION: SEQ ID NO:l: TCGCGCGTTT CGGTGATGAC GGTGAAAACC TCTGACACAT GCAGCTCCCG GAGACGGTCA 60 CAGCTTGTCT GTAAGCGGAT GCCGGGAGCA GACAAGCCCG TCAGGGCGCG TCAGCGGGTG 120 TTGGCGGGTG TCGGGGCTGG CTTAACTATG CGGCATCAGA GCAGATTGTA CTGAGAGTGC 180 ACCATATGCG GTGTGAAATA CCGCACAGAT GCGTAAGGAG AAAATACCGC ATCAGGCGCC 240 ATTCGCCATT CAGGCTGCGC AACTGTTGGG AAGGGCGATC GGTGCGGGCC TCTTCGCTAT 300 TACGCCAGCT GGCGAAAGGG GGATGTGCTG CAAGGCGATT AAGTTGGGTA ACGCCAGGGT 360 TTTCCCAGTC ACGACGTTGT AAAACGACGG CCAGTGCCAG TGAATTCGTT GCAGGACAGG 420 ATGTGGTGCC CGATGTGACT AGCTCTTTGC TGCAGGCCGT CCTATCCTCT GGTTCCGATA 480 AGAGACCCAG AACTCCGGCC CCCCACCGCC CACCGCCACC CCCATACATA TGTGGTACGC 540 AAGTAAGAGT GCCTGCGCAT GCCCCATGTG CCCCACCAAG AGTTTTGCAT CCCATACAAG 600 TCCCCAAAGT GGAGAACCGA ACCAATTCTT CGCGGGCAGA ACAAAAGCTT CTGCACACGT 660 CTCCACTCGA ATTTGGAGCC GGCCGGCGTG TGCAAAAGAG GTGAATCGAA CGAAAGACCC 720 GTGTGTAAAG CCGCGTTTCC AAAATGTATA AAACCGAGAG CATCTGGCCA ATGTGCATCA 780 GTTGTGGTCA GCAGCAAAAT CAAGTGAATC ATCTCAGTGC AACTAAAGGG GGGATCCGAT 840 ATCCAAGGTT ACCGCGGACT AGTCTAGTAA CGGCCGCCAG TGTGCTGGAA TTCGGCT 897 ATG GAC CAC CTC GGG GCG TCC CTC TGG CCC CAG GTC GGC TCC CTT TGT 945 Met Asp His Leu Gly Ala Ser Leu Trp Pro Gin Val Gly Ser Leu Cys 1 5 10 15 CTC CTG CTC GCT GGG GCC GCC TGG GCG CCC CCG CCT AAC CTC CCG GAC 993 Leu Leu Leu Ala Gly Ala Ala Trp Ala Pro Pro Pro Asn Leu Pro Asp 20 25 30 CCC AAG TTC GAG AGC AAA GCG GCC TTG CTG GCG GCC CGG GGG CCC GAA 1041 Pro Lys Phe Glu Ser Lys Ala Ala Leu Leu Ala Ala Arg Gly Pro Glu 35 40 45 GAG CTT CTG TGC TTC ACC GAG CGG TTG GAG GAC TTG GTG TGT TTC TGG 1089 Glu Leu Leu Cys Phe Thr Glu Arg Leu Glu Asp Leu Val Cys Phe Trp 50 55 60 GAG GAA GCG GCG AGC GCT GGG GTG GGC CCG GGC AAC TAC AGC TTC TCC 1137 Glu Glu Ala Ala Ser Ala Gly Val Gly Pro Gly Asn Tyr Ser Phe Ser 65 70 75 80 TAC CAG CTC GAG GAT GAG CCA TGG AAG CTG TGT CGC CTG CAC CAG GCT 1185 Tyr Gin Leu Glu Asp Glu Pro Trp Lys Leu Cys Arg Leu His Gin Ala 85 90 95 CCC ACG GCT CGT GGT GCG GTG CGC TTC TGG TGT TCG CTG CCT ACA GCC 1233 Pro Thr Ala Arg Gly Ala Val Arg Phe Trp Cys Ser Leu Pro Thr Ala 100 105 110 GAC ACG TCG AGC TTC GTG CCC CTA GAG TTG CGC GTC ACA GCA GCC TCC 1281 Asp Thr Ser Ser Phe Val Pro Leu Glu Leu Arg Val Thr Ala Ala Ser 115 120 125 GGC GCT CCG CGA TAT CAC CGT GTC ATC CAC ATC AAT GAA GTA GTG CTC 1329 Gly Ala Pro Arg Tyr His Arg Val He His He Asn Glu Val Val Leu 130 135 140 CTA GAC GCC CCC GTG GGG CTG GTG GCG CGG TTG GCT GAC GAG AGC GGC 1377 Leu Asp Ala Pro Val Gly Leu Val Ala Arg Leu Ala Asp Glu Ser Gly 145 150 155 160 CAC GTA GTG TTG CGC TGG CTC CCG CCG CCT GAG ACA CCC ATG ACG TCT 1425 His Val Val Leu Arg Trp Leu Pro Pro Pro Glu Thr Pro Met Thr Ser 165 170 175 CAC ATC CGC TAC GAG GTG GAC GTC TCG GCC GGC AAC GGC GCA GGG AGC 1473 His He Arg Tyr Glu Val Asp Val Ser Ala Gly Asn Gly Ala Gly Ser 180 185 190 GTA CAG AGG GTG GAG ATC CTG GAG GGC CGC ACC GAG TGT GTG CTG AGC 1521 Val Gin Arg Val Glu He Leu Glu Gly Arg Thr Glu Cys Val Leu Ser 195 200 205 AAC CTG CGG GGC CGG ACG CGC TAC ACC TTC GCC GTC CGC GCG CGT ATG 1569 Asn Leu Arg Gly Arg Thr Arg Tyr Thr Phe Ala Val Arg Ala Arg Met 210 215 220 GCT GAG CCG AGC TTC GGC GGC TTC TGG AGC GCC TGG TCG GAG CCT GTG 1617 Ala Glu Pro Ser Phe Gly Gly Phe Trp Ser Ala Trp Ser Glu Pro Val 225 230 235 240 TCG CTG CTG ACG CCT AGC GAC CTG GAC CCC ATT GAG GGC CGT GGT ACC 1665 Ser Leu Leu Thr Pro Ser Asp Leu Asp Pro He Glu Gly Arg Gly Thr 245 250 255 GAG CCC AAA TCG GCC GAC AAA ACT CAC ACA TGC CCA CCG TGC CCA GCA 1713 Glu Pro Lys Ser Ala Asp Lys Thr His Thr Cys Pro Pro Cys Pro Ala 260 265 270 CCT GAA CTC CTG GGG GGA CCG TCA GTC TTC CTC TTC CCC CCA AAA CCC 1761 Pro Glu Leu Leu Gly Gly Pro Ser Val Phe Leu Phe Pro Pro Lys Pro 275 280 285 AAG GAC ACC CTC ATG ATC TCC CGG ACC CCT GAG GTC ACA TGC GTG GTG 1809 Lys Asp Thr Leu Met He Ser Arg Thr Pro Glu Val Thr Cys Val Val 290 295 300 GTG GAC GTG AGC CAC GAA GAC CCT GAG GTC AAG TTC AAC TGG TAC GTG 1857 Val Asp Val Ser His Glu Asp Pro Glu Val Lys Phe Asn Trp Tyr Val 305 310 315 320 GAC GGC GTG GAG GTG CAT AAT GCC AAG ACA AAG CCG CGG GAG GAG CAG 1905 Asp Gly Val Glu Val His Asn Ala Lys Thr Lys Pro Arg Glu Glu Gin 325 330 335 TAC AAC AGC ACG TAC CGG GTG GTC AGC GTC CTC ACC GTC CTG CAC CAG 1953 Tyr Asn Ser Thr Tyr Arg Val Val Ser Val Leu Thr Val Leu His Gin 340 345 350 GAC TGG CTG AAT GGC AAG GAG TAC AAG TGC AAG GTC TCC AAC AAA GCC 2001 Asp Trp Leu Asn Gly Lys Glu Tyr Lys Cys Lys Val Ser Asn Lys Ala 355 360 365 CTC CCA GCC CCC ATC GAG AAA ACC ATC TCC AAA GCC AAA GGG CAG CCC 2049 Leu Pro Ala Pro He Glu Lys Thr He Ser Lys Ala Lys Gly Gin Pro 370 375 380 CGA GAA CCA CAG GTG TAC ACC CTG CCC CCA TCC CGG GAT GAG CTG ACC 2097 Arg Glu Pro Gin Val Tyr Thr Leu Pro Pro Ser Arg Asp Glu Leu Thr 385 390 395 400 AAG AAC CAG GTC AGC CTG ACC TGC CTG GTC AAA GGC TTC TAT CCC AGC 2145 Lys Asn Gin Val Ser Leu Thr Cys Leu Val Lys Gly Phe Tyr Pro Ser 405 410 415 GAC ATC GCC GTG GAG TGG GAG AGC AAT GGG CAG CCG GAG AAC AAC TAC 2193 Asp He Ala Val Glu Trp Glu Ser Asn Gly Gin Pro Glu Asn Asn Tyr 420 425 430 AAG ACC ACG CCT CCC GTG CTG GAC TCC GAC GGC TCC TTC TTC CTC TAC 2241 Lys Thr Thr Pro Pro Val Leu Asp Ser Asp Gly Ser Phe Phe Leu Tyr 435 440 445 AGC AAG CTC ACC GTG GAC AAG AGC AGG TGG CAG CAG GGG AAC GTC TTC 2289 Ser Lys Leu Thr Val Asp Lys Ser Arg Trp Gin Gin Gly Asn Val Phe 450 455 460 TCA TGC TCC GTG ATG CAT GAG GCT CTG CAC AAC CAC TAC ACG CAG AAG 2337 Ser Cys Ser Val Met His Glu Ala Leu His Asn His Tyr Thr Gin Lys 465 470 475 480 AGC CTC TCC CTG TCT CCG GGT AAA TGAGTGTAGT CTAGAAGCTT ACGCGTAGGC 2391 Ser Leu Ser Leu Ser Pro Gly Lys 485 CTGAGCTCGC TGATCAGCCT CGAGGATCCA GACATGATAA GATACATTGA TGAGTTTGGA 2451 CAAACCACAA CTAGAATGCA GTGAAAAAAA TGCTTTATTT GTGAAATTTG TGATGCTATT 2511 GCTTTATTTG TAACCATTAT AAGCTGCAAT AAACAAGTTA ACAACAACAA TTGCATTCAT 2571 TTTATGTTTC AGGTTCAGGG GGAGGTGTGG GAGGTTTTTT AAAGCAAGTA AAACCTCTAC 2631 AAATGTGGTA TGGCTGATTA TGATCAGTCG ACCGATGCCC TTGAGAGCCT TCAACCCAGT 2691 CAGCTCCTTC CGGTGGGCGC GGGGCATGAC TATCGTCGCC GCACTTATGA CTGTCTTCTT 2751 TATCATGCAA CTCGTAGGAC AGGTGCCGGC AGCGCTCTGG GTCATTTTCG GCGAGGACCG 2811 CTTTCGCTGG AGCGCGACGA TGATCGGCCT GTCGCTTGCG GTATTCGGAA TCTTGCACGC 2871 CCTCGCTCAA GCCTTCGTCA CTGGTCCCGC CACCAAACGT TTCGGCGAGA AGCAGGCCAT 2931 TATCGCCGGC ATGGCGGCCG ACGCGCTGGG CTACGTCTTG CTGGCGTTCG CGACGCGAGG 2991 CTGGATGGCC TTCCCCATTA TGATTCTTCT CGCTTCCGGC GGCATCGGGA TGCCCGCGTT 3051 GCAGGCCATG CTGTCCAGGC AGGTAGATGA CGACCATCAG GGACAGCTTC AAGGATCGCT 3111 CGCGGCTCTT ACCAGCCAGC AAAAGGCCAG GAACCGTAAA AAGGCCGCGT TGCTGGCGTT 3171 TTTCCATAGG CTCCGCCCCC CTGACGAGCA TCACAAAAAT CGACGCTCAA GTCAGAGGTG 3231 GCGAAACCCG ACAGGACTAT AAAGATACCA GGCGTTTCCC CCTGGAAGCT CCCTCGTGCG 3291 CTCTCCTGTT CCGACCCTGC CGCTTACCGG ATACCTGTCC GCCTTTCTCC CTTCGGGAAG 3351 CGTGGCGCTT TCTCAATGCT CACGCTGTAG GTATCTCAGT TCGGTGTAGG TCGTTCGCTC 3411 CAAGCTGGGC TGTGTGCACG AACCCCCCGT TCAGCCCGAC CGCTGCGCCT TATCCGGTAA 3471 CTATCGTCTT GAGTCCAACC CGGTAAGACA CGACTTATCG CCACTGGCAG CAGCCACTGG 3531 TAACAGGATT AGCAGAGCGA GGTATGTAGG CGGTGCTACA GAGTTCTTGA AGTGGTGGCC 3591 TAACTACGGC TACACTAGAA GGACAGTATT TGGTATCTGC GCTCTGCTGA AGCCAGTTAC 3651 CTTCGGAAAA AGAGTTGGTA GCTCTTGATC CGGCAAACAA ACCACCGCTG GTAGCGGTGG 3711 TTTTTTTGTT TGCAAGCAGC AGATTACGCG CAGAAAAAAA GGATCTCAAG AAGATCCTTT 3771 GATCTTTTCT ACGGGGTCTG ACGCTCAGTG GAACGAAAAC TCACGTTAAG GGATTTTGGT 3831 CATGAGATTA TCAAAAAGGA TCTTCACCTA GATCCTTTTA AATTAAAAAT GAAGTTTTAA 3891 ATCAATCTAA AGTATATATG AGTAAACTTG GTCTGACAGT TACCAATGCT TAATCAGTGA 3951 GGCACCTATC TCAGCGATCT GTCTATTTCG TTCATCCATA GTTGCCTGAC TCCCCGTCGT 4011 GTAGATAACT ACGATACGGG AGGGCTTACC ATCTGGCCCC AGTGCTGCAA TGATACCGCG 4071 AGACCCACGC TCACCGGCTC CAGATTTATC AGCAATAAAC CAGCCAGCCG GAAGGGCCGA 4131 GCGCAGAAGT GGTCCTGCAA CTTTATCCGC CTCCATCCAG TCTATTAATT GTTGCCGGGA 4191 AGCTAGAGTA AGTAGTTCGC CAGTTAATAG TTTGCGCAAC GTTGTTGCCA TTGCTGCAGG 4251 CATCGTGGTG TCACGCTCGT CGTTTGGTAT GGCTTCATTC AGCTCCGGTT CCCAACGATC 4311 AAGGCGAGTT ACATGATCCC CCATGTTGTG CAAAAAAGCG GTTAGCTCCT TCGGTCCTCC 4371 GATCGTTGTC AGAAGTAAGT TGGCCGCAGT GTTATCACTC ATGGTTATGG CAGCACTGCA 4431 TAATTCTCTT ACTGTCATGC CATCCGTAAG ATGCTTTTCT GTGACTGGTG AGTACTCAAC 4491 CAAGTCATTC TGAGAATAGT GTATGCGGCG ACCGAGTTGC TCTTGCCCGG CGTCAACACG 4551 GGATAATACC GCGCCACATA GCAGAACTTT AAAAGTGCTC ATCATTGGAA AACGTTCTTC 4611 GGGGCGAAAA CTCTCAAGGA TCTTACCGCT GTTGAGATCC AGTTCGATGT AACCCACTCG 4671 TGCACCCAAC TGATCTTCAG CATCTTTTAC TTTCACCAGC GTTTCTGGGT GAGCAAAAAC 4731 AGGAAGGCAA AATGCCGCAA AAAAGGGAAT AAGGGCGACA CGGAAATGTT GAATACTCAT 4791 ACTCTTCCTT TTTCAATATT ATTGAAGCAT TTATCAGGGT TATTGTCTCA TGAGCGGATA 4851 CATATTTGAA TGTATTTAGA AAAATAAACA AATAGGGGTT CCGCGCACAT TTCCCCGAAA 4911 AGTGCCACCT GACGTCTAAG AAACCATTAT TATCATGACA TTAACCTATA AAAATAGGCG 4971 TATCACGAGG CCCTTTCGT 4990 (2) INFORMATION FOR SEQ ID N0:2: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 488 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2: Met Asp His Leu Gly Ala Ser Leu Trp Pro Gin Val Gly Ser Leu Cys 1 5 10 15 Leu Leu Leu Ala Gly Ala Ala Trp Ala Pro Pro Pro Asn Leu Pro Asp 20 25 30 Pro Lys Phe Glu Ser Lys Ala Ala Leu Leu Ala Ala Arg Gly Pro Glu 35 40 45 Glu Leu Leu Cys Phe Thr Glu Arg Leu Glu Asp Leu Val Cys Phe Trp 50 55 60 Glu Glu Ala Ala Ser Ala Gly Val Gly Pro Gly Asn Tyr Ser Phe Ser 65 70 75 80 Tyr Gin Leu Glu Asp Glu Pro Trp Lys Leu Cys Arg Leu His Gin Ala 85 90 95 Pro Thr Ala Arg Gly Ala Val Arg Phe Trp Cys Ser Leu Pro Thr Ala 100 105 110 Asp Thr Ser Ser Phe Val Pro Leu Glu Leu Arg Val Thr Ala Ala Ser 115 120 125 Gly Ala Pro Arg Tyr His Arg Val He His He Asn Glu Val Val Leu 130 135 140 Leu Asp Ala Pro Val Gly Leu Val Ala Arg Leu Ala Asp Glu Ser Gly 145 150 155 160 His Val Val Leu Arg Trp Leu Pro Pro Pro Glu Thr Pro Met Thr Ser 165 170 175 His He Arg Tyr Glu Val Asp Val Ser Ala Gly Asn Gly Ala Gly Ser 180 185 190 Val Gin Arg Val Glu He Leu Glu Gly Arg Thr Glu Cys Val Leu Ser 195 200 205 Asn Leu Arg Gly Arg Thr Arg Tyr Thr Phe Ala Val Arg Ala Arg Met 210 215 220 Ala Glu Pro Ser Phe Gly Gly Phe Trp Ser Ala Trp Ser Glu Pro Val 225 230 235 240 Ser Leu Leu Thr Pro Ser Asp Leu Asp Pro He Glu Gly Arg Gly Thr 245 250 255 Glu Pro Lys Ser Ala Asp Lys Thr His Thr Cys Pro Pro Cys Pro Ala 260 265 270 Pro Glu Leu Leu Gly Gly Pro Ser Val Phe Leu Phe Pro Pro Lys Pro 275 280 285 Lys Asp Thr Leu Met He Ser Arg Thr Pro Glu Val Thr Cys Val Val 290 295 300 Val Asp Val Ser His Glu Asp Pro Glu Val Lys Phe Asn Trp Tyr Val 305 310 315 320 Asp Gly Val Glu Val His Asn Ala Lys Thr Lys Pro Arg Glu Glu Gin 325 330 335 Tyr Asn Ser Thr Tyr Arg Val Val Ser Val Leu Thr Val Leu His Gin 340 345 350 Asp Trp Leu Asn Gly Lys Glu Tyr Lys Cys Lys Val Ser Asn Lys Ala 355 360 365 Leu Pro Ala Pro He Glu Lys Thr He Ser Lys Ala Lys Gly Gin Pro 370 375 380 Arg Glu Pro Gin Val Tyr Thr Leu Pro Pro Ser Arg Asp Glu Leu Thr 385 390 395 400 Lys Asn Gin Val Ser Leu Thr Cys Leu Val Lys Gly Phe Tyr Pro Ser 405 410 415 Asp He Ala Val Glu Trp Glu Ser Asn Gly Gin Pro Glu Asn Asn Tyr 420 425 430 Lys Thr Thr Pro Pro Val Leu Asp Ser Asp Gly Ser Phe Phe Leu Tyr 435 440 445 Ser Lys Leu Thr Val Asp Lys Ser Arg Trp Gin Gin Gly Asn Val Phe 450 455 460 Ser Cys Ser Val Met His Glu Ala Leu His Asn His Tyr Thr Gin Lys 465 470 475 480 Ser Leu Ser Leu Ser Pro Gly Lys 485 (2) INFORMATION FOR SEQ ID NO:3: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 6367 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3: GACGTCGACG GATCGGGAGA TCGGGGATCG ATCCGTCGAC GTACGACTAG TTATTAATAG 60 TAATCAATTA CGGGGTCATT AGTTCATAGC CCATATATGG AGTTCCGCGT TACATAACTT 120 ACGGTAAATG GCCCGCCTGG CTGACCGCCC AACGACCCCC GCCCATTGAC GTCAATAATG 180 ACGTATGTTC CCATAGTAAC GCCAATAGGG ACTTTCCATT GACGTCAATG GGTGGACTAT 240 TTACGGTAAA CTGCCCACTT GGCAGTACAT CAAGTGTATC ATATGCCAAG TACGCCCCCT 300 ATTGACGTCA ATGACGGTAA ATGGCCCGCC TGGCATTATG CCCAGTACAT GACCTTATGG 360 GACTTTCCTA CTTGGCAGTA CATCTACGTA TTAGTCATCG CTATTACCAT GGTGATGCGG 420 TTTTGGCAGT ACATCAATGG GCGTGGATAG CGGTTTGACT CACGGGGATT TCCAAGTCTC 480 CACCCCATTG ACGTCAATGG GAGTTTGTTT TGGCACCAAA ATCAACGGGA CTTTCCAAAA 540 TGTCGTAACA ACTCCGCCCC ATTGACGCAA ATGGGCGGTA GGCGTGTACG GTGGGAGGTC 600 TATATAAGCA GAGCTGGGTA CGTGAACCGT CAGATCGCCT GGAGACGCCA TCGAATTCGG 660 TTACCTGCAG ATATCAAGCT AATTCGGTAC CGAGCCCAAA TCGGCCGACA AAACTCACAC 720 ATGCCCACCG TGCCCAGCAC CTGAACTCCT GGGGGGACCG TCAGTCTTCC TCTTCCCCCC 780 AAAACCCAAG GACACCCTCA TGATCTCCCG GACCCCTGAG GTCACATGCG TGGTGGTGGA 840 CGTGAGCCAC GAAGACCCTG AGGTCAAGTT CAACTGGTAC GTGGACGGCG TGGAGGTGCA 900 TAATGCCAAG ACAAAGCCGC GGGAGGAGCA GTACAACAGC ACGTACCGGG TGGTCAGCGT 960 CCTCACCGTC CTGCACCAGG ACTGGCTGAA TGGCAAGGAG TACAAGTGCA AGGTCTCCAA 1020 CAAAGCCCTC CCAGCCCCCA TCGAGAAAAC CATCTCCAAA GCCAAAGGGC AGCCCCGAGA 1080 ACCACAGGTG TACACCCTGC CCCCATCCCG GGATGAGCTG ACCAAGAACC AGGTCAGCCT 1140 GACCTGCCTG GTCAAAGGCT TCTATCCCAG CGACATCGCC GTGGAGTGGG AGAGCAATGG 1200 GCAGCCGGAG AACAACTACA AGACCACGCC TCCCGTGCTG GACTCCGACG GCTCCTTCTT 1260 CCTCTACAGC AAGCTCACCG TGGACAAGAG CAGGTGGCAG CAGGGGAACG TCTTCTCATG 1320 CTCCGTGATG CATGAGGCTC TGCACAACCA CTACACGCAG AAGAGCCTCT CCCTGTCTCC 1380 GGGTAAATGA GTGTAGTCTA GAGCTCGCTG ATCAGCCTCG ACTGTGCCTT CTAGTTGCCA 1440 GCCATCTGTT GTTTGCCCCT CCCCCGTGCC TTCCTTGACC CTGGAAGGTG CCACTCCCAC 1500 TGTCCTTTCC TAATAAAATG AGGAAATTGC ATCGCATTGT CTGAGTAGGT GTCATTCTAT 1560 TCTGGGGGGT GGGGTGGGGC AGGACAGCAA GGGGGAGGAT TGGGAAGACA ATAGCAGGCA 1620 TGCTGGGGAT GCGGTGGGCT CTATGGAACC AGCTGGGGCT CGAGGGGGGA TCTCCCGATC 1680 CCCAGCTTTG CTTCTCAATT TCTTATTTGC ATAATGAGAA AAAAAGGAAA ATTAATTTTA 1740 ACACCAATTC AGTAGTTGAT TGAGCAAATG CGTTGCCAAA AAGGATGCTT TAGAGACAGT 1800 GTTCTCTGCA CAGATAAGGA CAAACATTAT TCAGAGGGAG TACCCAGAGC TGAGACTCCT 1860 AAGCCAGTGA GTGGCACAGC ATTCTAGGGA GAAATATGCT TGTCATCACC GAAGCCTGAT 1920 TCCGTAGAGC CACACCTTGG TAAGGGCCAA TCTGCTCACA CAGGATAGAG AGGGCAGGAG 1980 CCAGGGCAGA GCATATAAGG TGAGGTAGGA TCAGTTGCTC CTCACATTTG CTTCTGACAT 2040 AGTTGTGTTG GGAGCTTGGA TAGCTTGGAC AGCTCAGGGC TGCGATTTCG CGCCAAACTT 2100 GACGGCAATC CTAGCGTGAA GGCTGGTAGG ATTTTATCCC CGCTGCCATC ATGGTTCGAC 2160 CATTGAACTG CATCGTCGCC GTGTCCCAAA ATATGGGGAT TGGCAAGAAC GGAGACCTAC 2220 CCTGGCCTCC GCTCAGGAAC GAGTTCAAGT ACTTCCAAAG AATGACCACA ACCTCTTCAG 2280 TGGAAGGTAA ACAGAATCTG GTGATTATGG GTAGGAAAAC CTGGTTCTCC ATTCCTGAGA 2340 AGAATCGACC TTTAAAGGAC AGAATTAATA TAGTTCTCAG TAGAGAACTC AAAGAACCAC 2400 CACGAGGAGC TCATTTTCTT GCCAAAAGTT TGGATGATGC CTTAAGACTT ATTGAACAAC 2460 CGGAATTGGC AAGTAAAGTA GACATGGTTT GGATAGTCGG AGGCAGTTCT GTTTACCAGG 2520 AAGCCATGAA TCAACCAGGC CACCTTAGAC TCTTTGTGAC AAGGATCATG CAGGAATTTG 2580 AAAGTGACAC GTTTTTCCCA GAAATTGATT TGGGGAAATA TAAACTTCTC CCAGAATACC 2640 CAGGCGTCCT CTCTGAGGTC CAGGAGGAAA AAGGCATCAA GTATAAGTTT GAAGTCTACG 2700 AGAAGAAAGA CTAACAGGAA GATGCTTTCA AGTTCTCTGC TCCCCTCCTA AAGCTATGCA 2760 TTTTTATAAG ACCATGCTAG CTTGAACTTG TTTATTGCAG CTTATAATGG TTACAAATAA 2820 AGCAATAGCA TCACAAATTT CACAAATAAA GCATTTTTTT CACTGCATTC TAGTTGTGGT 2880 TTGTCCAAAC TCATCAATGT ATCTTATCAT GTCTGGATCA ACGATAGCTT ATCTGTGGGC 2940 GATGCCAAGC ACCTGGATGC TGTTGGTTTC CTGCTACTGA TTTAGAAGCC ATTTGCCCCC 3000 TGAGTGGGGC TTGGGAGCAC TAACTTTCTC TTTCAAAGGA AGCAATGCAG AAAGAAAAGC 3060 ATACAAAGTA TAAGCTGCCA TGTAATAATG GAAGAAGATA AGGTTGTATG AATTAGATTT 3120 ACATACTTCT GAATTGAAAC TAAACACCTT TAAATTCTTA AATATATAAC ACATTTCATA 3180 TGAAAGTATT TTACATAAGT AACTCAGATA CATAGAAAAC AAAGCTAATG ATAGGTGTCC 3240 CTAAAAGTTC ATTTATTAAT TCTACAAATG ATGAGCTGGC CATCAAAATT CCAGCTCAAT 3300 TCTTCAACGA ATTAGAAAGA GCAATCTGCA AACTCATCTG GAATAACAAA AAACCTAGGA 3360 TAGCAAAAAC TCTTCTCAAG GATAAAAGAA CCTCTGGTGG AATCACCATG CCTGACCTAA 3420 AGCTGTACTA CAGAGCAATT GTGATAAAAA CTGCATGGTA CTGATATAGA AACGGACAAG 3480 TAGACCAATG GAATAGAACC CACACACCTA TGGTCACTTG ATCTTCAACA AGAGAGCTAA 3540 AACCATCCAC TGGAAAAAAG ACAGCATTTT CAACAAATGG TGCTGGCACA ACTGGTGGTT 3600 ATCATGGAGA AGAATGTGAA TTGATCCATT CCAATCTCCT TGTACTAAGG TCAAATCTAA 3660 GTGGATCAAG GAACTCCACA TAAAACCAGA GACACTGAAA CTTATAGAGG AGAAAGTGGG 3720 GAAAAGCCTC GAAGATATGG GCACAGGGGA AAAATTCCTG AATAGAACAG CAATGGCTTG 3780 TGCTGTAAGA TCGAGAATTG ACAAATGGGA CCTCATGAAA CTCCAAAGCT ATCGGATCAA 3840 TTCCTCCAAA AAAGCCTCCT CACTACTTCT GGAATAGCTC AGAGGCCGAG GCGGCCTCGG 3900 CCTCTGCATA AATAAAAAAA ATTAGTCAGC CATGCATGGG GCGGAGAATG GGCGGAACTG 3960 GGCGGAGTTA GGGGCGGGAT GGGCGGAGTT AGGGGCGGGA CTATGGTTGC TGACTAATTG 4020 AGATGCATGC TTTGCATACT TCTGCCTGCT GGGGAGCCTG GGGACTTTCC ACACCTGGTT 4080 GCTGACTAAT TGAGATGCAT GCTTTGCATA CTTCTGCCTG CTGGGGAGCC TGGGGACTTT 4140 CCACACCCTA ACTGACACAC ATTCCACAGA ATTAATTCCC GATCCCGTCG ACCTCGAGAG 4200 CTTGGCGTAA TCATGGTCAT AGCTGTTTCC TGTGTGAAAT TGTTATCCGC TCACAATTCC 4260 ACACAACATA CGAGCCGGAA GCATAAAGTG TAAAGCCTGG GGTGCCTAAT GAGTGAGCTA 4320 ACTCACATTA ATTGCGTTGC GCTCACTGCC CGCTTTCCAG TCGGGAAACC TGTCGTGCCA 4380 GCTGCATTAA TGAATCGGCC AACGCGCGGG GAGAGGCGGT TTGCGTATTG GGCGCTCTTC 4440 CGCTTCCTCG CTCACTGACT CGCTGCGCTC GGTCGTTCGG CTGCGGCGAG CGGTATCAGC 4500 TCACTCAAAG GCGGTAATAC GGTTATCCAC AGAATCAGGG GATAACGCAG GAAAGAACAT 4560 GTGAGCAAAA GGCCAGCAAA AGGCCAGGAA CCGTAAAAAG GCCGCGTTGC TGGCGTTTTT 4620 CCATAGGCTC CGCCCCCCTG ACGAGCATCA CAAAAATCGA CGCTCAAGTC AGAGGTGGCG 4680 AAACCCGACA GGACTATAAA GATACCAGGC GTTTCCCCCT GGAAGCTCCC TCGTGCGCTC 4740 TCCTGTTCCG ACCCTGCCGC TTACCGGATA CCTGTCCGCC TTTCTCCCTT CGGGAAGCGT 4800 GGCGCTTTCT CAATGCTCAC GCTGTAGGTA TCTCAGTTCG GTGTAGGTCG TTCGCTCCAA 4860 GCTGGGCTGT GTGCACGAAC CCCCCGTTCA GCCCGACCGC TGCGCCTTAT CCGGTAACTA 4920 TCGTCTTGAG TCCAACCCGG TAAGACACGA CTTATCGCCA CTGGCAGCAG CCACTGGTAA 4980 CAGGATTAGC AGAGCGAGGT ATGTAGGCGG TGCTACAGAG TTCTTGAAGT GGTGGCCTAA 5040 CTACGGCTAC ACTAGAAGGA CAGTATTTGG TATCTGCGCT CTGCTGAAGC CAGTTACCTT 5100 CGGAAAAAGA GTTGGTAGCT CTTGATCCGG CAAACAAACC ACCGCTGGTA GCGGTGGTTT 5160 TTTTGTTTGC AAGCAGCAGA TTACGCGCAG AAAAAAAGGA TCTCAAGAAG ATCCTTTGAT 5220 CTTTTCTACG GGGTCTGACG CTCAGTGGAA CGAAAACTCA CGTTAAGGGA TTTTGGTCAT 5280 GAGATTATCA AAAAGGATCT TCACCTAGAT CCTTTTAAAT TAAAAATGAA GTTTTAAATC 5340 AATCTAAAGT ATATATGAGT AAACTTGGTC TGACAGTTAC CAATGCTTAA TCAGTGAGGC 5400 ACCTATCTCA GCGATCTGTC TATTTCGTTC ATCCATAGTT GCCTGACTCC CCGTCGTGTA 5460 GATAACTACG ATACGGGAGG GCTTACCATC TGGCCCCAGT GCTGCAATGA TACCGCGAGA 5520 CCCACGCTCA CCGGCTCCAG ATTTATCAGC AATAAACCAG CCAGCCGGAA GGGCCGAGCG 5580 CAGAAGTGGT CCTGCAACTT TATCCGCCTC CATCCAGTCT ATTAAΪTGTT GCCGGGAAGC 5640 TAGAGTAAGT AGTTCGCCAG TTAATAGTTT GCGCAACGTT GTTGCCATTG CTACAGGCAT 5700 CGTGGTGTCA CGCTCGTCGT TTGGTATGGC TTCATTCAGC TCCGGTTCCC AACGATCAAG 5760 GCGAGTTACA TGATCCCCCA TGTTGTGCAA AAAAGCGGTT AGCTCCTTCG GTCCTCCGAT 5820 CGTTGTCAGA AGTAAGTTGG CCGCAGTGTT ATCACTCATG GTTATGGCAG CACTGCATAA 5880 TTCTCTTACT GTCATGCCAT CCGTAAGATG CTTTTCTGTG ACTGGTGAGT ACTCAACCAA 5940 GTCATTCTGA GAATAGTGTA TGCGGCGACC GAGTTGCTCT TGCCCGGCGT CAATACGGGA 6000 TAATACCGCG CCACATAGCA GAACTTTAAA AGTGCTCATC ATTGGAAAAC GTTCTTCGGG 6060 GCGAAAACTC TCAAGGATCT TACCGCTGTT GAGATCCAGT TCGATGTAAC CCACTCGTGC 6120 ACCCAACTGA TCTTCAGCAT CTTTTACTTT CACCAGCGTT TCTGGGTGAG CAAAAACAGG 6180 AAGGCAAAAT GCCGCAAAAA AGGGAATAAG GGCGACACGG AAATGTTGAA TACTCATACT 6240 CTTCCTTTTT CAATATTATT GAAGCATTTA TCAGGGTTAT TGTCTCATGA GCGGATACAT 6300 ATTTGAATGT ATTTAGAAAA ATAAACAAAT AGGGGTTCCG CGCACATTTC CCCGAAAAGT 6360 GCCACCT 6367 (2) INFORMATION FOR SEQ ID NO:4: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 38 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) ' MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4: GTATCATGGA CCACCTCGGG GCGTCCCTCT GGCCCCAG 38 (2) INFORMATION FOR SEQ ID NO:5: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 33 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5: ATGGACCACC TCGGGGCGTC CCTCTGGCCC CAG 33 (2) INFORMATION FOR SEQ ID NO:6: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 38 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6: GTGTCCTAAG AGCAAGCCAC ATAGCTGGGG GGCAGAGG 38 (2) INFORMATION FOR SEQ ID NO:7: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 33 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID N0:7: CTAAGAGCAA GCCACATAGC TGGGGGGCAG AGG 33 (2) INFORMATION FOR SEQ ID NO:8: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 41 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8: AGTCACTAGG GGTCCAGGTC GCTAGGCGTC AGCAGCGACA C 41 (2) INFORMATION FOR SEQ ID NO:9: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 36 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9: CTGGGGGTCC AGGTCGCTAG GCGTCAGCAG CGACAC 36 (2) INFORMATION FOR SEQ ID NO:10: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 43 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10: TCGAGCTCGG TACCGAGCCC AAATCGGCCG ACAAAACTCA CAC 43 (2) INFORMATION FOR SEQ ID NO:11: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 28 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:11: GTACTGCTCC TCCCGCGGCT TTGTCTTG 28 (2) INFORMATION FOR SEQ ID NO:12: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 27 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:12: AATTCGGTTA CCTGCAGATA TCAAGCT 27 (2) INFORMATION FOR SEQ ID NO:13: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 27 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: unknown (D) TOPOLOGY: not relevant (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:13: AATTAGCTTG ATATCTGCAG GTAACCG 27

Claims: WHAT IS CLAIMED IS: 1. A method for generating an antibody capable of acting as an agonist of a receptor comprising: introducing into an immunocompetent animal or isolated immunocompetent cells thereof an antigenically effective amount of a recombinant immunogen comprising a first extraceUular receptor domain spaced apart from a second extraceUular receptor domain by a bridging moiety which places said first domain and said second domain in functional proximity which mimics the functional domain proximity of a native multimeric receptor. 2. The method according to claim 1 wherein said native multimeric receptor is a homodimer and said first domain and said second domain are the same. 3. The method according to claim 1 wherein said native multimeric receptor is a heterodimer and said first domain and said second domain are different subunits of the same receptor. 4. The method according to claim 1 wherein said bridging moiety is peptidic. 5. The method according to claim 4 wherein said bridging moiety is an amino acid amphipathic helix. 6. The method according to claim 5 wherein said helix is a leucine zipper. 7. The method according to claim 4 wherein said bridging moiety is an Fc portion of a human immunoglobulin with an intact hinge region. 8. The method according to claim 1 wherein said bridging moiety is an organic non-peptidic molecule. 9. The method according to claim 8 wherein said organic molecule is a bifunctional cross Unker. 10. The method according to claim 9 wherein said cross-linker is selected from the group consisting of carbodUmide, glutaraldehyde, DSS, and BS3. 11. In a method for generating a monoclonal antibody comprising introducing an immunogen into an animal or to isolated cells thereof, isolating antibody producing ceUs therefrom, fusing said antibody producing ceUs with immortalized ceUs and isolating a hybridoma cell line which secretes a monoclonal antibody to said immunogen, the improvement comprising employing as the immunogen the immunogen of claim 1. 12. An antibody produced by the method of claim 1. 13. An antibody produced by the method of claim 11. 14. An altered antibody comprising a portion of the antibody selected from the group consisting of the antibody of Claim 12 and Claim 13. 15. A recombinant immunogen comprising a first extraceUular receptor domain spaced apart from a second extraceUular receptor domain by a bridging moiety which places said first domain and said second domain in functional proximity which mimics the functional domain proximity of a native multimeric receptor. 16. The immunogen according to claim 15 wherein said multimeric receptor is a homodimer or heterodimer. 17. The immunogen according to claim 15 wherein said bridging moiety is peptidic domain. 18. The immunogen according to claim 15 wherein said bridging moiety is an organic non-peptidic molecule. 19. A recombinant polynucleotide comprising a nucleotide region encoding a first extraceUular domain of a receptor molecule fused in the correct reading frame to a nucleotide region encoding a peptidic bridging moiety which is fused in the correct reading frame to a nucleotide region encoding a second extraceUular domain of a receptor molecule. 20. The recombinant polynucleotide according to claim 19 comprising a nucleotide region encoding a first extraceUular domain of a receptor molecule fused in the correct reading frame to a nucleotide region encoding a peptidic bridging moiety. 21. The polynucleotide according to claim 19 wherein a further nucleotide region encoding an enzymaticaUy cleavable peptide sequence is optionaUy inserted in the correct reading frame between: (a) the region encoding said first extraceUular domain and the region encoding said bridging moiety; or (b) the region encoding the bridging moiety and the region encoding said second extraceUular domain; or both (a) and (b). 22. The polynucleotide according to claim 20 wherein a further nucleotide region encoding an enzymaticaUy cleavable peptide sequence is optionaUy inserted in the correct reading frame between the region encoding said first extraceUular domain and the region encoding said bridging moiety. 23. A vector comprising a polynucleotide sequence of any of the claims 19-22 under the control of suitable regulatory sequences capable of directing replication and expression of said polynucleotide sequence in a host ceU. 24. A host ceU transformed with the vector according to claim 23. 25. A recombinant immunogen comprising a first extracellular receptor domain of the erythropoietin receptor spaced apart from a second erythropoietin receptor extracellular domain by an Fc region with intact hinge region of a human antibody, which places saidfirst domain and said second domain in functional proximity which niimics the functional domain proximity of the native dimeric erythropoietin receptor. 26. The immunogen according to claim 25, which is EpoRFc. 27. An EPO agonist antibody characterized as possessing at least 20% of EPO activity when measured in a CFU(E) assay or at least 40% of EPO activity when measured in a proUferation assay or havng an affinity for EpoR as measured by Kd equal to or less than about 23nM, or having an affinity for EpoRFc as measured by Kd of equal to or less than 500pM. 28. The antibody according to claim 27 wherein said antibody possesses at least 40% of EPO activity when measured in a CFU(E) assay or at least 60% of EPO activity when measured in a proUferation assay. 29 The antibody according to claim 27 wherein the antibody is selected from the group consisting of 1C8 and 2G6. 30. A method of treating anemia in a patient comprising administering a therapeutically effective amount of the antibody of claim 27. 31. A method for modulating the endogenous activity of an EPO receptor in a mammal comprising administering a modulating effective amount of the antibody of claim 27.

Inventors: ERICKSON-MILLER CONNIE L, YOUNG PETER RONALD, ERICKSON-MILLER, CONNIE, L., YOUNG, PETER, RONALD
Applicants: ERICKSON MILLER CONNIE L, SMITHKLINE BEECHAM CORP, YOUNG PETER RONALD, ERICKSON-MILLER, CONNIE, L., SMITHKLINE BEECHAM CORPORATION, YOUNG, PETER, RONALD
Application year: 1996
Main classification: A61K39
IPC codes: A61K38, A61K39, A61P7, A61P43, C07K14, C07K16, C12N5, C12N15, C12P21