NUCLEIC ACID MOLECULES AND POLYPEPTIDES FOR IMMUNE MODULATION

Abstract: The invention provides gp38 polypeptides, which play a role in immunomodulation, nucleic acid molecules encoding these polypeptides, and therapeutic and diagnostic methods employing these polypeptides and nucleic acid molecules. The invention also provides methods for identifying compounds that modulate the biological activities of gp38 nucleic acid molecules and polypeptides, and therapeutic methods employing these compounds.

Description: NUCLEIC ACID MOLECULES AND POLYPEPTIDES FOR IMMUNE MODULATION FIELD OF THE INVENTION The invention generally relates to immunology, and specifically relates to the identification and use of novel viral genes as immune modulators. BACKGROUND OF THE INVENTION Viruses propagate by living within the cells of higher-order vertebrates. Accordingly, they have evolved to specifically avoid the host immune system. Virus survival is dependent upon strategies that can evade, suppress, counteract, or otherwise circumvent host responses to a foreign antigen. These host responses are a powerful element of evolutionary pressure; all eukaryotic viruses existing today contain remnants of their battles with the host immune system, as evidenced by the presence of viral-encoded proteins that suppress the immune response or allow the virus to avoid immune system detection. The specific strategy or strategies used by a virus varies dramatically according to its genome capacity. Viruses with small genomes ensure their survival by exploiting weaknesses or gaps in the host immune repertoire to avoid detection. Alternatively or additionally, small viral genomes replicate rapidly, effectively outpacing the host immune response. Larger DNA viruses (e.g., adenoviruses, herpesviruses, iridoviruses, and poxviruses) specifically encode proteins that function to protect the virus from immune recognition and/or clearance by the infected host. Such "subversive" viral proteins are useful therapeutics for the treatment of inflammatory and autoimmune disorders. Poxviruses, in particular, have been a rich source of such immunomodulatory proteins. The genus of poxviruses includes Tanapox virus (TPV), Yaba monkey tumor virus (YMTV), and Yaba-like disease (YLD) virus (Knight et ai, Virology 172:116- 124, 1989). Both TPV and YMTV contain a linear double-stranded, approximately 145 kbp DNA genome (Essani et al., Microbial Pathogenesis 17:347-353, 1994; Knight et al., .supra). TPV produces a mild disease in humans, characterized by transient fever, one or more nodular skin lesions, and regional lymphadenopathy, while YMTV causes benign tumors in monkeys and humans (Paulose et al, Microbial Pathogenesis 25:33-41, 1998; Amano et al, Journal of General Virology 76:1109-1115, 1995). A 38 kDa secreted glycoprotein from TPV-induced cells has been reported to specifically bind and neutralize three human cytokines, namely interferon-γ, interleukin-2, and interleukin-5 (Essani et al., supra). It would be useful to identify novel viral immunomodulatory genes and polypeptides for the treatment of immunological disorders. SUMMARY OF THE INVENTION In general, the present invention provides immunomodulatory gp38 polypeptides, nucleic acid molecules encoding these polypeptides, and therapeutic, diagnostic, and screening methods employing these polypeptides and nucleic acid molecules. The invention also provides methods for identifying compounds that modulate the biological activities of gp38 nucleic acid molecules and polypeptides, and therapeutic methods employing these compounds. The present invention provides novel Yatapoxvirus immunomodulatory gp38 polypeptides, nucleic acid molecules encoding these polypeptides, and therapeutic, diagnostic, and screening methods employing these polypeptides and nucleic acid molecules. The invention also provides methods for identifying compounds that modulate the biological activities of Yatapoxvirus gp38 nucleic acid molecules and polypeptides, and therapeutic methods employing these compounds. In a first aspect, the invention provides a substantially pure Yatapoxvirus immunomodulatory polypeptide. In preferred embodiments of the first aspect, the polypeptide can be derived from yaba monkey tumor virus or from tanapox virus. In another preferred embodiment of the first aspect, the polypeptide includes an amino acid sequence that encodes an identifiable signal sequence. In another preferred embodiment of the first aspect, the polypeptide can be a chemokine (e.g. of human interferon-γ, human interleukin-2, and human interleukin-5) binding polypeptide, a cytokine binding polypeptide, an immunomodulator, or an anti-inflammatory polypeptide. In other preferred embodiments of the first aspect, the polypeptide can be glycosylated or have anti- cytokine activity. In other preferred embodiments of the first aspect, the polypeptide may include an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6, or may include the amino acid sequence of SEQ ID NO: 1, SEQ LD NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6. In a second aspect, the invention provides a substantially pure Yatapoxvirus nucleic acid molecule encoding a Yatapoxvirus immunomodulatory polypeptide. In preferred embodiments of the second aspect, the nucleic acid molecule can be genomic DNA, cDNA, or mRNA. In another preferred embodiment of the second aspect, the nucleic acid molecule includes a nucleotide sequence that encodes a polypeptide with an identifiable signal sequence. In other preferred embodiments of the second aspect, the nucleic acid molecule can encode a yaba monkey tumor virus polypeptide or a tanapox virus polypeptide, encode a polypeptide including an amino sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6, or encode a polypeptide including the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6. In other preferred embodiments of the second aspect, the nucleic acid molecule can include a nucleotide sequence that is substantially identical to the nucleotide sequence of SEQ ID NO: 3, SEQ ID NO: 5, SEQ ID NO: 7, or SEQ ID NO: 9. In other preferred embodiments of the second aspect, the invention provides a vector (e.g. a gene therapy vector) including the substantially pure Yatapoxvirus nucleic acid molecule encoding a Yatapoxvirus immunomodulatory polypeptide, and a cell containing this vector. The Yatapoxvirus nucleic acid molecule in the vector can be operably linked to regulatory sequences for expression of a Yatapoxvirus polypeptide and the regulatory sequences can include a promoter. The cell can be a human cell, a primate cell, or a rodent cell. In other preferred embodiments of the second aspect, the invention provides a non-human transgenic animal containing the substantially pure Yatapoxvirus nucleic acid molecule encoding a Yatapoxvirus immunomodulatory polypeptide, and a cell from the non-human transgenic animal. In other preferred embodiments of the second aspect, the invention provides a method of detecting a Yatapoxvirus gene or a Yatapoxvirus gene homolog or fragment thereof in a cell by contacting the substantially pure Yatapoxvirus nucleic acid molecule encoding a Yatapoxvirus immunomodulatory polypeptide, or a fragment thereof, where the fragment is greater than about 18 nucleotides in length, with a preparation of genomic DNA from the cell, under hybridization conditions providing detection of DNA sequences having about 50% or greater nucleotide sequence identity to SEQ ID NO: 3, SEQ ID NO: 5, SEQ ID NO: 7, or SEQ ID NO: 9. In a third aspect, the invention provides a nucleic acid molecule having at least 50% nucleic acid sequence identity to a sequence encoding a Yatapoxvirus immunomodulatory polypeptide or a fragment thereof, where the fragment includes at least six amino acids and the nucleic acid molecule hybridizes under high stringency conditions to at least a portion of a Yatapoxvirus nucleic acid molecule. In a preferred embodiment of the third aspect, the nucleic acid molecule has 100% complementarity to a nucleic acid molecule encoding a Yatapoxvirus immunomodulatory polypeptide or a fragment thereof including at least six amino acids, and the nucleic acid molecule hybridizes under high stringency conditions to at least a portion of a Yatapoxvirus nucleic acid molecule. In a fourth aspect, the invention provides a nucleic acid molecule, where the nucleic acid molecule includes a sequence that is antisense to the coding strand of a Yatapoxvirus nucleic acid molecule or a fragment thereof. In a fifth aspect, the invention provides a non-human transgenic animal having a knockout mutation in one or both alleles encoding a polypeptide substantially identical to a polypeptide. In a sixth aspect, the invention provides an antibody that specifically binds to a Yatapoxvirus polypeptide, for example, a polypeptide that includes an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6. In a preferred embodiment of the sixth aspect, the invention provides a method of detecting a Yatapoxvirus polypeptide in a sample by contacting the sample with the antibody, and assaying for the binding of the antibody to the polypeptide. In a seventh aspect, the invention provides a probe for analyzing a Yatapoxvirus gene or a Yatapoxvirus gene homolog or fragment thereof, the probe having at least 50% nucleotide sequence identity to a sequence encoding a Yatapoxvirus polypeptide or fragment thereof, where the fragment includes at least six amino acids, and the probe hybridizes under high stringency conditions to at least a portion of a Yatapoxvirus nucleic acid molecule. In a preferred embodiment of the seventh aspect, the probe has 100% complementarity to a nucleic acid molecule encoding a Yatapoxvirus polypeptide or fragment thereof, where the fragment includes at least six amino acids, and the probe hybridizes under high stringency conditions to at least a portion of a Yatapoxvirus nucleic acid molecule. In an eighth aspect, the invention provides a method of identifying an immunomodulatory Yatapoxvirus gene or a Yatapoxvirus immunomodulatory gene homolog or fragment thereof by: (a) providing a mammalian cell sample; (b) introducing into the cell sample a candidate gene; (c) expressing the candidate gene; and (d) determining whether the candidate gene elicits an alteration in the level of immune function in the cell sample, where an alteration in the level of immune function identifies the immunomodulatory Yatapoxvirus gene or the Yatapoxvirus immunomodulatory gene homolog, or fragment thereof. In a ninth aspect, the invention provides a method for identifying a test compound that modulates the expression or activity of a Yatapoxvirus polypeptide, by contacting the Yatapoxvirus polypeptide with the test compound, and determining the effect of the test compound on the Yatapoxvirus polypeptide expression or activity. In a tenth aspect, the invention provides a method for identifying a test compound that modulates the expression or activity of a swinepox (C1L) polypeptide, by contacting the swinepox (C1L) polypeptide with the test compound, and determining the effect of the test compound on the swinepox (C1L) polypeptide expression or activity. In an eleventh aspect, the invention provides a method of targeting proteins for secretion from a cell by attaching an identifiable signal sequence selected from a Yatapoxvirus polypeptide to a protein of interest, where the protein of interest is secreted from the cell. In a twelfth aspect, the invention provides a method of targeting proteins for secretion from a cell by attaching an identifiable signal sequence selected from a swinepox (C 1L) polypeptide to a protein of interest, where the protein of interest is secreted from the cell. In a thirteenth aspect, the invention provides a method of immunomodulation in a mammal by administering to the mammal a therapeutically effective amount of a Yatapoxvirus polypeptide or fragment thereof, where the polypeptide has an immunomodulatory effect in the mammal. In a fourteenth aspect, the invention provides a method of immunomodulation in a mammal by administering to the mammal a therapeutically effective amount of a swinepox (C1L) polypeptide or fragment thereof, where the polypeptide has an immunomodulatory effect in the mammal. In a fifteenth aspect, the invention provides a method of immunomodulation in a mammal by administering to the mammal a therapeutically effective amount of a compound that modulates the activity of a Yatapoxvirus polypeptide, where the compound has an immunomodulatory effect in the mammal. In a sixteenth aspect, the invention provides a method of immunomodulation in a mammal by administering to the mammal a therapeutically effective amount of a compound that modulates the activity of a swinepox (C1L) polypeptide, where the compound has an immunomodulatory effect in the mammal. The immunomodulation of the thirteenth through sixteenth aspects can be immunosuppression, immunostimulation, cell proliferation, apoptosis, decreasing T cell stimulation, or decreasing inflammation in a mammal. In an eighteenth aspect, the invention provides a method of treating a mammal having an immunomodulatory disorder, by administering to the mammal a therapeutically effective amount of a compound that modulates the activity of a swinepox (C1L) polypeptide, where the compound has an immunomodulatory effect in the mammal. In a nineteenth aspect, the invention provides a pharmaceutical composition including at least one dose of a therapeutically effective amount of a Yatapoxx'irus polypeptide or fragment thereof, in a pharmaceutically acceptable carrier, the composition being formulated for the treatment of an immunomodulatory disorder. In a twentieth aspect, the invention provides a pharmaceutical composition including at least one dose of a therapeutically effective amount of a swinepox (C1L) polypeptide or fragment thereof, in a pharmaceutically acceptable carrier, the composition being formulated for the treatment of an immunomodulatory disorder. In preferred embodiments of the thirteenth to twentieth aspects, the Yatapoxvirus polypeptide includes an amino acid sequence substantially identical to the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, or SEQ ID NO: 8, and fragments and analogs thereof. In other preferred embodiments of the thirteenth to twentieth aspects, the mammal is a human. In other preferred embodiments of the thirteenth to twenty- first aspects, the mammal has a condition selected from the group consisting of acute inflammation, rheumatoid arthritis, transplant rejection, asthma, inflammatory bowel disease, uveitis, restenosis, multiple sclerosis, psoriasis, wound healing, lupus erythematosus, allergic rhinitis, atopic dermatitis, food allergies, type 1 insulin-dependent diabetes mellitus, deramatitis, meningitis, thrombotic thrombocytopenic purpura, Sjogren's syndrome, encephalitis, leukocyte adhesion deficiency, rheumatic fever, Reiter's syndrome, psoriatic arthritic, progressive systemic sclerosis, primary biliary cirrhosis, pemphigus, pemphigoid, necrotizing vasculitis, mayasthenia gravis, lupus erythmatosus, polymyositis, sarcoidosis, granulomatorsis, vasculitis, pernicious anemia, CNS inflammatory disorder, antigen-antibody complex mediated diseases, autoimmune hemolytic anemia, Hashimoto's thyroiditis, Graves disease, habitual spontaneous abortions, Reynard's syndrome, glomerulonephritis, dermatomyositis, chromic active hepatitis, celiac disease, autoimmune complications of AIDS, atrophic gastritis, ankylosing spondylitis, Addison's disease, psoriasis, penphigus vularis, Behcet's syndrome, acute respiratory distress syndrome (ARDS), ischemic heart disease, atherosclerosis, post-dialysis syndrome, leukemia, acquired immune deficiency syndrome septic shock, lipid histiocytosis, and cancer. In twenty-first and twenty-second aspects, the invention provides a kit for the analysis of a Yatapoxvirus nucleic acid molecule, the kit including a nucleic acid molecule probe for analyzing a Yatapoxvirus nucleic acid molecule present in a test subject, or including an antibody for analyzing a Yatapoxvirus polypeptide present in a test subject. The invention provides several advantages. For example, it provides methods and reagents that can be used in the diagnosis and treatment of immune diseases that are sensitive to the bioactivities of Yatapoxvirus or swinepox (C1L) gp38 polypeptides. Other features and advantages of the invention will be apparent from the detailed description of the invention, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows an alignment of partial amino acid sequences of gp38 from tanapox virus (SEQ ID NO: 1) and yaba monkey tumor virus (SEQ ID NO: 2). Figure 2 shows a partial amino acid sequence (SEQ ID NO: 2) and partial open reading frame nucleotide sequence (SEQ ID NO: 3) of gp38 from yaba monkey tumor virus (YMTV). Figure 3 shows the amino acid sequence of gp38 polypeptide from tanapox virus (SEQ ID NO: 4). Figure 4 shows the nucleic acid sequence of gp38 from tanapox virus (SEQ ID NO: 5). Figure 5 shows the amino acid sequence of gp38 polypeptide from yaba- like disease virus (YLDV) (SEQ ID NO: 6). Figure 6 shows the nucleic acid sequence of gp38 from yaba-like disease virus (YLDV) (SEQ ID NO: 7). Figure 7 shows the amino acid sequence of gp38 polypeptide from swinepox virus (C1L) (SEQ ID NO: 8). Figure 8 shows the nucleic acid sequence of gp38 from swinepox virus (ClL) (SEQ ID NO: 9). Figure 9 shows the sequence similarity of the various polypeptide amino acid sequences. DETAILED DESCRIPTION OF THE INVENTION The invention provides gp38 polypeptides and in swinepox polypeptide, which play a role in immunomodulation, nucleic acid molecules encoding these polypeptides, and therapeutic and diagnostic methods employing these polypeptides and nucleic acid molecules. The invention also provides methods for identifying compounds that modulate the biological activities of gp38 and swinepox nucleic acid molecules and polypeptides, and therapeutic methods employing these compounds. "Polypeptide" or "polypeptide fragment" means a chain of two or more amino acids, regardless of any post-translational modification (e.g., glycosylation, acetylation, or phosphorylation), constituting all or part of a naturally or non- naturally occurring polypeptide. By "post-translational modification" is meant any change to a polypeptide or polypeptide fragment during or after synthesis. Post-translational modifications can be produced naturally (such as during synthesis within a cell) or generated artificially (such as by recombinant or chemical means). A "protein" can be made up of one or more polypeptides. "Yatapoxvirus gp38 immunomodulatory polypeptide" or "Yatapoxvirus gp38 polypeptide" means a Yatapoxvirus gp38 polypeptide or protein having immunomodulatory activity that is substantially identical to the polypeptide sequences described herein, or a biologically-active fragment or analog thereof. Yatapoxvi ruses have been described in, for example, Essani et al. (Microbial Pathogenesis 17:347-353, 1994), Knight et al. (Virology 172:116-124, 1989), Paulose et al. (Microbial Pathogenesis 25:33-41, 1998), and Amano et al. (Journal of General Virology 76:1109-1115, 1995), herein incorporated by reference. Specifically included in the invention are Yaba monkey tumor virus (YMTV) and tanapox virus (TPV) gp38 polypeptides. A Yatapoxvirus gp38 polypeptide may also be defined as encoding a polypeptide with at least 50%, preferably at least 75%, more preferably at least 90%, and most preferably at least 95% of the biological activity, e.g., immunomodulatory or anti-inflammatory activity, compared to a reference Yatapoxvirus gp38 polypeptide having an amino acid sequence substantially identical to those described herein. The term Yatapoxvirus gp38 polypeptide includes homologs, e.g., mammalian homologs of Yatapoxvirus gp38 proteins as well as allelic variations, natural mutants, induced mutants, proteins encoded by DNAs that hybridize to the Yatapoxvirus gp38 sequences described herein under high stringency conditions, and polypeptides or proteins specifically-bound by antisera directed to a Yatapoxvirus gp38 polypeptide. The term also includes chimeric polypeptides that include a Yatapoxvirus gp38 fragment. "Swinepox virus (CIL) gp38 immunomodulatory polypeptide" or "swinepox virus (C IL) gp38 polypeptide" means a swinepox vims (C IL) gp38 polypeptide or protein having immunomodulatory activity that is substantially identical to the polypeptide sequences described herein, or a biologically-active fragment or analog thereof. A swinepox virus (CIL) gp38 polypeptide may also be defined as encoding a polypeptide with at least 50%, preferably at least 75%, more preferably at least 90%, and most preferably at least 95% of the biological activity, e.g., immunomodulatory or anti- inflammatory activity, compared to a reference swinepox virus (CIL) gρ38 polypeptide having an amino acid sequence substantially identical to those described herein. The term swinepox virus (CIL) gp38 polypeptide includes homologs, e.g., mammalian homologs of swinepox virus (CIL) gp38 proteins as well as allelic variations, natural mutants, induced mutants, proteins encoded by DNAs that hybridize to the swinepox virus (CIL) gp38 sequences described herein under high stringency conditions, and polypeptides or proteins specifically-bound by antisera directed to a swinepox virus (CIL) gp38 polypeptide. The term also includes chimeric polypeptides that include a swinepox virus (CIL) gp38 fragment. By "biologically-active fragment" is meant a polypeptide fragment of a Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide that exhibits immunomodulatory properties that are at least 30%, preferably at least 50%, more preferably at least 75%, and most preferably at least 95% of the immunomodulatory properties of a full length Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide. As used herein, the term "fragment" means at least 10 contiguous amino acids, preferably at least 30 contiguous amino acids, more preferably at least 50 contiguous amino acids, and most preferably at least 60 to 80 or more contiguous amino acids. Fragments of Yatapoxvirus or swinepox virus (CIL) gp38 proteins can be generated by methods known to those skilled in the art or may result from normal protein processing (e.g.. removal of amino acids from the nascent polypeptide that are not required for biological activity or removal of amino acids by alternative mRNA splicing or alternative protein processing events). By "analog" is meant any substitution, addition, or deletion in the amino acid sequence of a Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide that exhibits properties that are at least 30%, preferably at least 50%, more preferably at least 75%, and most preferably at least 95% of the immunomodulatory properties of a Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide from which it is derived. Analogs can differ from the naturally occurring Yatapoxvirus or swinepox virus (CIL) gp38 protein by amino acid sequence differences, by post-translational modifications, or by both. Analogs of the invention are substantially identical to a naturally occurring Yatapoxvirus or swinepox virus (CIL) gp38 sequence. Modifications include in vivo and in vitro chemical derivatization of polypeptides, e.g., acetylation, carboxylation, phosphorylation, or glycosylation. Such modifications may occur during polypeptide synthesis or processing or following treatment with isolated modifying enzymes. Analogs can also differ from the naturally occurring Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide by alterations in primary sequence. These include genetic variants, both natural and induced (for example, resulting from random mutagenesis by irradiation or exposure to ethanemethylsulfate or by site-specific mutagenesis as described in Sambrook, Fritsch and Maniatis, Molecular Cloning: A Laboratoiy Manual (2d ed.), CSH Press, 1989, hereby incorporated by reference; or Ausubel et al, Current Protocols in Molecular Biology, John Wiley & Sons, New York, 1994, hereby incorporated by reference). Also included are cyclized peptides molecules and analogs that contain residues other than L-amino acids, e.g., D-amino acids or non-naturally occurring or synthetic amino acids. Fragments and analogs can be generated using standard techniques, for example, solid phase peptide synthesis or polymerase chain reaction. "Yatapoxvirus gp38 nucleic acid molecule" means a nucleic acid molecule, such as a genomic DNA, cDNA, or RNA (e.g., mRNA) molecule that encodes a polypeptide having the characteristics or biological activities of any Yatapoxvirus gp38 polypeptide described herein, or a fragment or analog thereof. A Yatapoxvirus gp38 nucleic acid molecule is substantially identical to a reference Yatapoxvirus gp38 nucleic acid molecule, as described herein. "Swinepox virus (C IL) gp38 nucleic acid molecule" means a nucleic acid molecule, such as a genomic DNA, cDNA, or RNA (e.g., mRNA) molecule that encodes a polypeptide having the characteristics or biological activities of any swinepox virus (CIL) gp38 polypeptide described herein, or a fragment or analog thereof. A swinepox virus (CIL) gp38 nucleic acid molecule is substantially identical to a reference swinepox virus (CIL) gp38 nucleic acid molecule, as described herein. The term "identity" is used herein to describe the relationship of the sequence of a particular nucleic acid molecule or polypeptide to the sequence of a reference molecule of the same type. For example, if a polypeptide or nucleic acid molecule has the same amino acid or nucleotide residue at a given position, compared to a reference molecule to which it is aligned, there is said to be "identity" at that position. The level of sequence identity of a nucleic acid molecule or a polypeptide to a reference molecule is typically measured using sequence analysis software with the default parameters specified therein, such as the introduction of gaps to achieve an optimal alignment (e.g., Sequence Analysis Software Package of the Genetics Computer Group, University of Wisconsin Biotechnology Center, 1710 University Avenue, Madison, WI 53705, BLAST, or PILEUP/PRETTYBOX programs). These software programs match identical or similar sequences by assigning degrees of identity to various substitutions, deletions, or other modifications. Conservative substitutions typically include substitutions within the following groups: glycine, alanine, valine, isoleucine, and leucine; aspartic acid, glutamic acid, asparagine, and glutamine; serine and threonine; lysine and arginine; and phenylalanine and tyrosine. A nucleic acid molecule or polypeptide is said to be "substantially identical" to a reference molecule if it exhibits, over its entire length, at least 50% or 55% identity, preferably at least 60%, 65%, or 68% identity, more preferably at least 75% or 85% identity, and most preferably at least 90%, 95%, or 99% identity to the sequence of the reference molecule. For polypeptides, the length of comparison sequences is at least 16 amino acids, preferably at least 20 amino acids, more preferably at least 25 amino acids, and most preferably at least 35 amino acids. For nucleic acid molecules, the length of comparison sequences is at least 50 nucleotides, preferably at least 60 nucleotides, more preferably at least 75 nucleotides, and most preferably at least 110 nucleotides. Alternatively, or additionally, two nucleic acid sequences are "substantially identical" if they hybridize under high stringency conditions. By "high stringency conditions" is meant conditions that allow hybridization comparable with the hybridization that occurs using a DNA probe of at least 500 nucleotides in length, in a buffer containing 0.5 M NaHPO 4 , pH 7.2, 7% SDS, 1 mMEDTA, and 1% BSA (fraction V), at a temperature of 65°C, or a buffer containing 48% formamide, 4.8X SSC, 0.2 M Tris-Cl, pH 7.6, IX Denhardt's solution, 10% dextran sulfate, and 0.1% SDS, at a temperature of 42°C. (These are typical conditions for high stringency northern or Southern hybridizations.) High stringency hybridization is also relied upon for the success of numerous techniques routinely performed by molecular biologists, such as high stringency PCR, DNA sequencing, single strand conformational polymorphism analysis, and in situ hybridization. In contrast to northern and Southern hybridizations, these techniques are usually performed with relatively short probes (e.g., usually 16 nucleotides or longer for PCR or sequencing and 40 nucleotides or longer for in situ hybridization). The high stringency conditions used in these techniques are well known to those skilled in the art of molecular biology, and examples of them can be found, for example, in Ausubel et al, Current Protocols in Molecular Biology, John Wiley & Sons, New York, NY, 1998, which is hereby incorporated by reference. By "probe" or "primer" is meant a single-stranded DNA or RNA molecule of defined sequence that can base pair to a second DNA or RNA molecule that contains a complementary sequence ("target"). The stability of the resulting hybrid depends upon the extent of the base pairing that occurs. This stability is affected by parameters such as the degree of complementarity between the probe and target molecule, and the degree of stringency of the hybridization conditions. The degree of hybridization stringency is affected by parameters such as the temperature, salt concentration, and concentration of organic molecules, such as formamide, and is determined by methods that are well known to those skilled in the art. Probes or primers specific for Yatapoxvirus gp38 nucleic acid molecules, preferably, have greater than 45% sequence identity, more preferably at least 55- 75% sequence identity, still more preferably at least 75-85% sequence identity, yet more preferably at least 85-99% sequence identity, and most preferably 100% sequence identity to the nucleic acid sequences encoding the amino acid sequences described herein. Probes can be detectably-labeled, either radioactively or non-radioactively, by methods that are well-known to those skilled in the art. Probes can be used for methods involving nucleic acid hybridization, such as nucleic acid sequencing, nucleic acid amplification by the polymerase chain reaction, single stranded conformational polymorphism (SSCP) analysis, restriction fragment polymorphism (RFLP) analysis, Southern hybridization, northern hybridization, in situ hybridization, electrophoretic mobility shift assay (EMS A), and other methods that are well known to those skilled in the art. A molecule, e.g., an oligonucleotide probe or primer, a gene or fragment thereof, a cDNA molecule, a polypeptide, or an antibody, can be said to be "detectably-labeled" if it is marked in such a way that its presence can be directly identified in a sample. Methods for detectably-labeling molecules are well known in the art and include, without limitation, radioactive labeling (e.g., with an isotope, such as " " P or S) and nonradioactive labeling (e.g., with a fluorescent label, such as fluorescein). "Identifiable signal sequence" means a sequence of amino acids that may be identified by homology, or biological activity, to a peptide sequence with the known function of targeting a polypeptide to a particular region of the cell. Preferably the signal sequence directs the polypeptide to the cellular membrane such that the polypeptide is secreted. Alternatively, the signal sequence may direct the polypeptide to an intracellular compartment or organelle, such as the Golgi apparatus. One of ordinary skill in the art can identify a signal sequence by using readily available software (e.g., Sequence Analysis Software Package of the Genetics Computer Group, University of Wisconsin Biotechnology Center, 1710 University Avenue, Madison, WI 53705, BLAST, or PILEUP/PRETTYBOX programs). An identifiable signal sequence can be one that is, for example, substantially identical to a sequence that results in cleavage between amino acids 17 and 18 of YMTV gp38 (SEQ ID NO: 2). By a "substantially pure polypeptide" is meant a polypeptide (or a fragment or analog thereof) that has been separated from proteins and organic molecules that naturally accompany it. Typically, a polypeptide is substantially pure when it is at least 60%, by weight, free from the proteins and naturally- occurring organic molecules with which it is naturally associated. Preferably, the polypeptide is a Yatapoxvirus gp38 polypeptide that is at least 75%, more preferably at least 90%, and most preferably at least 99%, by weight, pure. A substantially pure Yatapoxvirus gp38 polypeptide can be obtained, for example, by extraction from a natural source (e.g., an infected mammalian cell), by expression of a recombinant nucleic acid molecule encoding a Yatapoxvirus gp38 polypeptide, or by chemical synthesis. Purity can be measured by any appropriate method, e.g., by column chromatography, polyacrylamide gel electrophoresis, or HPLC analysis. A polypeptide is substantially free of naturally associated components when it is separated from those proteins and organic molecules that accompany it in its natural state. Thus, a protein that is chemically synthesized or produced in a cellular system different from the cell in which it is naturally produced is substantially free from its naturally associated components. Accordingly, substantially pure polypeptides not only include those derived from eukaryotic organisms, but also those synthesized in expression systems, for example, E. coli or other prokaryotes, yeast, or insect cells. "Substantially pure nucleic acid molecule" means a nucleic acid molecule that is free of the components that naturally accompany it. For example, a substantially pure DNA is free of the genes that, in the naturally-occurring genome of the organism from which the DNA of the invention is derived, flank the gene. The term therefore includes, for example, a recombinant DNA which is incorporated into a vector; into an autonomously replicating plasmid or virus; or into the genomic DNA of a prokaryote or eukaryote; or that exists as a separate molecule (e.g., a cDNA or a genomic or cDNA fragment produced by PCR or restriction endonuclease digestion) independent of other sequences. It also includes a recombinant DNA that is part of a hybrid gene encoding additional polypeptide sequence. A nucleic acid molecule that is "antisense," means a nucleic acid molecule having a sequence that is complementary to at least 75 nucleotides, and preferably at least 100, 150, or 200 nucleotides, of the coding strand of a gene or nucleic acid molecule, such as a Yatapoxvirus gp38 gene or nudeic acid molecule. An antisense nucleic acid molecule can be, for example, capable of preferentially lowering the production of a Yatapoxvirus gp38 polypeptide encoded by a Yatapoxvirus gp38 gene or nucleic acid molecule. By "vector" is meant a genetically engineered plasmid or virus, derived from, for example, a bacteriophage, adenovirus, retrovirus, poxvirus, herpesvirus, or artificial chromosome, that is used to transfer a polypeptide (e.g., a Yatapoxvirus gp38 polypeptide) coding sequence, operably linked to a promoter, into a host cell, such that the encoded peptide or polypeptide is expressed within the host cell. A vector may be a gene therapy vector, i.e., a vector designed to transfer genetic material into the cells of a patient for a therapeutic benefit. Vectors generally contain regulatory sequences, including promoters, operably linked to the polypeptide coding sequences. A "promoter" is a minimal nucleic acid sequence element sufficient to direct transcription. If desired, constructs of the invention can include promoter elements that are sufficient to render promoter-dependent gene expression controllable in a cell type-specific, tissue-specific, or temporal-specific manner, or inducible by external signals or agents. Such elements can be located in the 5', 3', or intron regions of a gene. Sequences are "operably linked" when a gene and one or more regulatory sequences are connected in such a way as to permit gene expression when the appropriate molecules (e.g., transcriptional activator proteins) are bound to the regulatory sequences. By a "transgene" is meant a DNA molecule that is inserted by artifice into a cell (e.g., the nuclear genome of a cell), and is incorporated into the genome of an organism that develops from the cell. Such a transgene can be partly or entirely heterologous (i.e., foreign) to the transgenic organism, or can be a gene that is homologous to an endogenous gene of the organism. An organism or animal (e.g., a mammal, such as a mouse, rat, pig, or goat) can be said to be "transgenic" if it developed from a cell that had a transgene inserted into it by artifice. By a "knockout mutation" is meant an artificially-induced alteration in a nucleic acid molecule (created by recombinant DNA technology or deliberate exposure to a mutagen) that reduces the biological activity of the polypeptide normally encoded therefrom by at least 80% relative to the unmutated gene. The mutation can be, without limitation, an insertion, deletion, frameshift mutation, or a missense mutation. A "knockout animal" is preferably a mammal, and more preferably a mouse, containing a knockout mutation, as defined above. An antibody is said to "specifically bind" to a polypeptide if it recognizes and binds the polypeptide (e.g., a Yatapoxvirus polypeptide), but does not substantially recognize and bind other molecules (e.g., non-Yatapoxvirus gp38- related polypeptides) in a sample, e.g., a biological sample, that naturally includes the polypeptide. A preferred antibody binds to any Yatapoxvirus gp38 polypeptide sequence that is substantially identical to the polypeptide sequences shown herein, or fragments thereof. By "sample" is meant a tissue biopsy, amniotic fluid, cell, blood, serum, urine, stool, or other specimen obtained from a patient or test subject. The sample can be analyzed to detect a mutation in a Yatapoxvirus gp38 gene, expression levels of a Yatapoxvirus gp38 gene or polypeptide, or the biological function of a Yatapoxvirus gp38 polypeptide, by methods that are known in the art. For example, methods such as sequencing, single-strand conformational polymorphism (SSCP) analysis, or restriction fragment length polymorphism (RFLP) analysis of PCR products derived from a patient sample can be used to detect a mutation in a Yatapoxvirus gp38 gene; ELISA can be used to measure levels of Yatapoxvirus gp38 polypeptide; and PCR can be used to measure the level of a Yatapoxvirus gp38 nucleic acid molecule. "Immune function" or "immunoreactivity" refers to the ability of the immune system to respond to a foreign antigen as measured by standard assays. "Modulate" or "modulating" means the induction of a quantitative change, either by decrease or increase, in the response of a target cell, sample, or organism, as a result of an interaction with a Yatapoxvirus gp38 polypeptide or nucleic acid molecule or test compound. The increase or decrease is by at least 10%, preferably by at least 20%, more preferably by at least 50%, still more preferably by at least 75%, yet more preferably by at least 95% and most preferably by at least 100% relative to an untreated control organism, sample, or molecule. "Immunomodulation" or "immunomodulatory" refers to an alteration in the overall immunoreactivity of the immune system in a mammal, or alteration in the response of a cell, relative to an untreated control of the same type, upon treatment with an agent, such as a polypeptide or nucleic acid molecule of the present invention, or fragments and analogs thereof. Immunomodulation can be assayed using immune cells, for example, B cells, T cells, antigen-presenting cells, or any other cell that is involved in immune function. Immunomodulation can also be assayed by determining expression and/or activity of immune-related genes and proteins, or immune-related compounds, such as cytokines, cytokine receptors, immunoglobulins, etc. "Immunosuppression" refers to a decrease in the overall immunoreactivity of the immune system upon administration of an immunomodulator in comparison to the immunoreactivity of an immune system that has not been contacted with the particular immunomodulator. "Immunostimulation" refers to a increase in the overall immunoreactivity of the immune system upon administration of an immunomodulator in comparison to the immunoreactivity of an immune system that has not been contacted with the particular immunomodulator. "Decreasing T cell stimulation" means lowering the level of T cell stimulation as measured by, for example, a chromium release assay. "Decreasing inflammation" means decreasing the number of inflammatory cells (leukocytes, for example eosinophils) in the target tissue by, preferably, two-fold. By "cell proliferation" is meant the growth or reproduction of similar cells. By "apoptosis" is meant the process of cell death where a dying cell displays a set of well-characterized biochemical hallmarks which include cytolemmal blebbing, cell soma shrinkage, chromatin condensation, and DNA laddering. "Immunomodulator" refers to an agent that induces an immunomodulatory effect or alteration (i.e., immunosuppression, immunostimulation, etc.) as measured, for example, by an alteration of virulence in mutated viruses or a variety of immunoassays well known in the art (for example, chemotaxis assays as described herein). For example, in the present invention, an immunomodulator may elicit an altered level of immune function, such that the alteration in the level of immune function identifies a Yatapoxvirus gρ38 polypeptide. An "anti- inflammatory" agent is an immunomodulatory agent capable of decreasing the overall inflamation or immune function upon administration to an individual. Preferably, the increase or decrease is by at least 10%, preferably by at least 20%, more preferably by at least 50%, still more preferably by at least 75%, yet more preferably by at least 95% and most preferably by at least 100% relative to an untreated control organism, sample, or molecule. By "immunomodulatory disorder" or "immunological disorder" is meant any pathophysiological condition (i.e., a disturbance of function and/or structure of a living organism, resulting from an extemal source, a genetic predisposition, a physical or chemical trauma, or a combination of the above, including, but not limited to, any mammalian disease) that is characterized by an alteration in immune function. The alteration may include, for example, a decrease in immune cell number or size, an increase in cell apoptosis or death, or a decrease in immune cell growth, survival or differentiation. Immunological disorders include any disease that involve the immune response or immunity in general. More specifically, such a disorder is a malfunction of the immune system that reduces the ability of an organism to resist foreign substances in the body (e.g., viruses, bacteria, bacterial toxins, plant pollen, fungal spores, animal danders, medications, foods, or allogeneic or xenogeneic transplanted organs) or causes the body to produce antibodies against its own tissues (e.g., autoimmune disorders), resulting in tissue injury, or causes cancer. Immunological disorders can also occur when a malfunctioning immune system (caused by, for example, genetic defect, illness, injury, malnutrition, or medications, such as those used for chemotherapy) results in an increase in frequency or severity of infections. Immunological disorders are often accompanied by inflammation, which is the body's reaction to tissue injury, and results in the accumulation of white blood cells, macrophages, and lymphocytes at the site of injury. Immunological or immunomodulatory disorders include, without limitation, acute inflammation, rheumatoid arthritis, transplant rejection, asthma, inflammatory bowel disease, uveitis, restenosis, multiple sclerosis, psoriasis, wound healing, lupus erythematosus, and any other autoimmune or inflammatory disorder that can be recognized by one of ordinary skill in the art. For example, other diseases related to inflammation that may be treated by methods the present invention include, but are not limited to, allergic rhinitis, atopic dermatitis and food allergies. Examples of other autoimmune disorders, where the immune system attacks the host's own tissues, include, but are not limited to, type 1 insulin-dependent diabetes mellitus, dermatitis, meningitis, thrombotic thrombocytopenic purpura, Sjogren's syndrome, encephalitis, leukocyte adhesion deficiency, rheumatic fever, Reiter's syndrome, psoriatic arthritic, progressive systemic sclerosis, primary biliary cirrhosis, pemphigus, pemphigoid, necrotizing vasculitis, myasthenia gravis, systemic lupus erythmatosus, polymyositis, sarcoidosis, granulomatorsis, vasculitis, pernicious anemia, CNS inflammatory disorder antigen-antibody complex mediated diseases, autoimmune hemolytic anemia, Hashimoto's thyroiditis, Graves disease, habitual spontaneous abortions, Reynard's syndrome, glomerulonephritis, dermatomyositis, chromic active hepatitis, celiac disease, autoimmune complications of AIDS, atrophic gastritis, ankylosing spondylitis and Addison's disease. Other diseases related to non-malignant or immunological-related cell- proliferative diseases that may be treated by methods of the present invention include psoriasis, pemphigus vulgaris, Behcet's syndrome, acute respiratory distress syndrome (ARDS), ischemic heart disease, atherosclerosis, post-dialysis syndrome, leukemia, acquired immune deficiency syndrome septic shock and other type of acute inflammation, lipid histiocytosis, and cancer. By "test compound" is meant a chemical, be it naturally-occurring or artificially-derived, that is assayed for its ability to act as an immunomodulator by employing one of the assay methods described herein or known in the art. Test compounds may include, for example, peptides, polypeptides, synthesized organic molecules, naturally occurring organic molecules, nucleic acid molecules, and components thereof. "Therapeutically effective amount" as used herein in reference to dosage of a medication, refers to the administration of a specific amount of a pharmacologically active agent (e.g., a Yatapoxvirus gp38 polypeptide as described herein) tailored to each individual patient manifesting symptoms characteristic of an immunological disorder, or at risk for a immunological disorder. For example, a patient receiving the treatment of the present invention might be experiencing an autoimmune or inflammatory disease. A person skilled in the art will recognize that the optimal dose of a pharmaceutical agent to be administered will vary from one individual to another. Dosage in individual patients should take into account the patient's height, weight, rate of absorption and metabolism of the medication in question, the stage of the disorder to be treated, and what other pharmacological agents are administered concurrently. By "pharmaceutically acceptable carrier" is meant a carrier that is physiologically acceptable to the treated mammal while retaining the therapeutic properties of the compound with which it is administered. One exemplary pharmaceutically acceptable carrier is physiological saline solution. Other physiologically acceptable carriers and their formulations are known to one skilled in the art and described, for example, in Remington: The Science and Practice of Pharmacy, (19 th edition), ed. A. Gennaro, 1995, Mack Publishing Company, Easton, PA. By "treating " or "treatment" is meant the medical management of a patient with the intent to cure, ameliorate, stabilize, or prevent a disease, pathological condition, or disorder. This term includes active treatment, that is, treatment directed specifically toward the improvement or associated with the cure of a disease, pathological condition, or disorder, and also includes causal treatment, that is, treatment directed toward removal of the cause of the associated disease, pathological condition, or disorder. In addition, this term includes palliative treatment, that is, treatment designed for the relief of symptoms rather than the curing of the disease, pathological condition, or disorder; preventative treatment, that is, treatment directed to minimizing or partially or completely inhibiting the development of the associated disease, pathological condition, or disorder; and supportive treatment, that is, treatment employed to supplement another specific therapy directed toward the improvement of the associated disease, pathological condition, or disorder. The phrase "treatment" also includes symptomatic treatment, that is, treatment directed toward constitutional symptoms of the associated disease, pathological condition, or disorder. By "cytokine" is meant a small molecular weight polypeptide that plays an important role in regulating the immune response, by for example, signaling adjacent cells. By "chemokine" is meant a small molecular weight ligand that is a chemoattractant for leukocytes (e.g., neutrophils, basophils, monocytes, and T cells), and is important for infiltration of lymphocytes and monocytes into sites of inflammation. The therapeutic, diagnostic, and screening methods of the invention are first described, followed by general approaches that can be used in carrying out these methods. This description will assist those skilled in the art to better understand the invention and its principles and advantages. It is intended that this description be illustrative of the invention and not limit the scope thereof. Therapeutic Methods Employing gp38 Nucleic Acid Molecules, Polypeptides, Antibodies, And Immunomodulatory Compounds The invention includes methods of treating or preventing immunological disorders by using immunomodulatory agents. Immunomodulatory reagents include, without limitation, Yatapoxvirus gp38 or swinepox virus (CIL) polypeptides; Yatapoxvirus or swinepox virus (C IL) gp38 cDNAs, mRNAs, or antisense RNAs; Yatapoxvirus or swinepox virus (CIL) gp38 antibodies; and any compound that modulates Yatapoxvirus gp38 biological activity, expression, or stability. Yatapoxvirus or swinepox virus (CIL) gp38 polypeptides identified in the present invention (or fragments or analogs thereof) that exhibit anti-cytokine activity, anti- inflammatory activity, and exhibit a decrease in leukocyte chemotaxis activity are considered particularly useful in the invention; such polypeptides may be used, for example, as therapeutics to decrease the immunoreactivity in a individual with rheumatoid arthritis. Other immunological disorders that may be treated using an immunosuppressive agent, or an agent that reduces the immune function, include acute inflammation, allergic reactions, asthmatic reactions, inflammatory bowel diseases (i.e., Crohn's Disease and ulcerative colitis), transplant rejection, and restenosis. Alternatively, a polypeptide that enhances or induces apoptosis may be used in the treatment of tumors. Treatment or prevention of diseases resulting from an immunomodulatory disorder is accomplished, for example, by modulating the function of a immunoregulatory protein by delivering a Yatapoxvirus or swinepox virus (CIL) gp38 protein to the appropriate cells. It is also possible to correct an immune defect by modifying the physiological pathway (e.g., a signal transduction pathway), in which the immunoregulatory protein participates, by delivering a Yatapoxvirus gp38 protein or nucleic acid molecule to the appropriate cells. Direct administration of a recombinant Yatapoxλ'irus or swinepox virus (CIL) gp38 protein, nucleic acid molecule, antibody, or compound, either to the site of a potential or actual disease-affected tissue (for example, by injection), or systemically for treatment of, for example, an autoimmune or inflammatory disorder, can be performed accordingly to any conventional recombinant protein administration technique known in the art or described herein. The actual dosage depends on a number of factors known to those of ordinary skill in the art, including the size and health of the individual patient, but generally, between 0.1 mg and lOOmg inclusive are administered per day to an adult in any pharmaceutically-acceptable formulation. A Yatapoxvirus or swinepox virus (CIL) gp38 immunomodulator, antiflammatory agent, or anticarcinogen may be administered with a pharmaceutically-acceptable diluent, cairier, or excipient, at a pharmaceutically effective dose. Conventional pharmaceutical practice may be employed to provide suitable formulations or compositions to administer Yatapoxvirus or swinepox virus (CIL) gp38 polypeptides to patients suffering from an immunomodulatory disorder. Any appropriate route of administration may be employed, for example, parenteral, intravenous, subcutaneous, intramuscular, intracranial, intraorbital, ophthalmic, intraventricular, intracapsular, intraspinal, intracistemal, intraperitoneal, intranasal, aerosol, or oral administration. Therapeutic formulations may be in the form of liquid solutions or suspensions; for oral administration, formulations may be in the form of tablets or capsules; and for intranasal formulations, in the form of powders, nasal drops, or aerosols. Methods well known in the art for making formulations are found in, for example, "Remington's Pharmaceutical Sciences, supra." Formulations for parenteral administration may, for example, contain excipients, sterile water, or saline, polyalkylene glycols such as polyethylene glycol, oils of vegetable origin, or hydrogenated napthalenes. Biocompatible, biodegradable lactide polymer, lactide/glycolide copolymer, or polyoxyethylene-polyoxypropylene copolymers may be used to control the release of the compounds. Other potentially useful parenteral delivery systems for Yatapoxvirus gp38 immunomodulatory compounds include ethylene-vinyl acetate copolymer particles, osmotic pumps, implantable infusion systems, and liposomes. Formulations for inhalation may contain excipients, for example, lactose, or may be aqueous solutions containing, for example, polyoxyethylene-9-lauryl ether, glycocholate and deoxycholate, or may be oily solutions for administration in the form of nasal drops, or as a gel. Yatapoxvirus or swinepox virus (CIL) gp38 Gene Therapy A Yatapoxvirus or swinepox virus (C IL) gp38 gene or fragment thereof can be used in immunomodulatory or anti-cancer gene therapy. For example, to enhance leukocyte infiltration of a tumor, a functional Yatapoxvirus or swinepox virus (CIL) gp38 gene or fragment thereof may be introduced into cells at the site of a tumor. In addition, Yatapoxvirus or swinepox virus (CIL) gp38 polypeptides that are shown to reverse autoimmune reactions can also be used in gene therapy. Alternatively, Yatapoxvirus or swinepox virus (CIL) gp38 polypeptides that block inflammation can be administered via gene therapy, for example, for the treatment of eosinophil-mediated inflammatory conditions. Gene transfer is achieved using viral vectors, as well as by non-viral means. Transplantation of genes into the affected tissues of a patient can also be accomplished by transferring a Yatapoxvirus or swinepox virus (CIL) gp38 gene or fragment thereof into a cultivatable cell type ex vivo, after which the cell (or its descendants) is injected into a targeted tissue. Retroviral vectors, adenoviral vectors, adeno-associated viral vectors, or other viral vectors with the appropriate tropism for Yatapoxvirus or swinepox virus (CIL) gp38 protein-expressing cells may be used as a gene transfer delivery system for a therapeutic Yatapoxvirus or swinepox virus (CIL) gp38 gene construct. Numerous vectors useful for this purpose are known (see, for example, Miller, Human Gene Therapy 15-14, 1990; Friedman, Science 244:1275-1281, 1989; Eglitis and Anderson, BioTechniques 6:608-614, 1988; Tolstoshev and Anderson, Current Opinion in Biotechnology 1 :55-61, 1990; Sharp, The Lancet 337: 1277- 1278, 1991; Cometta et al, Nucleic Acid Research and Molecular Biology 36:311-322, 1987; Anderson, Science 226:401-409, 1984; Moen, Blood Cells 17:407-416, 1991; and Miller and Rosman, Biotechniques 7:980-990, 1989; Le Gal La Salle et al, Science 259:988-990, 1993; and Johnson, Chest 107:77S- 83S, 1995). Retroviral vectors are particularly well developed and have been used in clinical settings (Rosenberg et al, N. Engl. J. Med 323:370, 1990; Anderson et al, U.S. Pat. No. 5,399,346). Non-viral approaches, for the introduction of therapeutic DNA into cells, include transfection in vitro, by means of any standard technique, including but not limited to, calcium phosphate, DEAE dextran, electroporation, protoplast fusion, and liposomes. For example, a Yatapoxvirus gp38 gene may be introduced into a tumor cell by lipofection (Feigner et al, Proc. Natl. Acad. Sci. USA 84:7413, 1987; Ono et al, Neuroscience Lett 117:259, 1990; Brigham et al, Am. J. Med. Sci. 298:278, 1989; Staubinger and Papahadjopoulos, Meth. Em. 101:512, 1983); asialorosonucoid-polylysine conjugation (Wu and Wu, J. Biol. Chem. 263: 14621, 1988; Wu et al, J. Biol. Chem. 264: 16985, 1989); or microinjection under surgical conditions (Wolff et al, Science 247:1465, 1990). For any of the above approaches, the therapeutic Yatapoxvirus gp38 DNA construct is preferably applied to the site of the malignancy or inflammation and cytotoxic damage (for example, by injection), but may also be applied to tissue in the vicinity of the malignancy or inflammation and cytotoxic damage, or even to a blood vessel supplying these areas. In the gene therapy constructs, Yatapoxvirus or swinepox virus (CIL) gρ38 cDNA expression is directed from any suitable promoter (e.g., the human cytomegalovirus, simian virus 40, or metallothionein promoters), and its production is regulated by any desired mammalian regulatory element. For example, if desired, enhancers known to direct preferential gene expression in endothelial or epithelial cells may be used to direct Yatapoxvirus or swinepox virus (CIL) gp38 protein expression. Such enhancers include, without limitation, the lung specific promotors (e.g. surfactant), and gut specific regulatory sequences. Alternatively, if a Yatapoxvirus or swinepox virus (CIL) gp38 genomic clone is utilized as a therapeutic construct (for example, following its isolation by hybridization with a Yatapoxvirus or swinepox virus (C IL) gp38 cDNA), Yatapoxvirus or swinepox virus (CIL) gp38 protein expression is regulated by its cognate regulatory sequences or, if desired, by regulatory sequences derived from a heterologous source, e.g., any of the promoters or regulatory elements described herein. Yatapoxvirus or swinepox virus (CIL) gp38 gene therapy is also accomplished by direct administration of the Yatapoxvirus or swinepox virus (C IL) gp38 mRNA to a tumor. This mRNA may be produced and isolated by any standard technique, but is most readily produced by in vitro transcription using a Yatapoxvirus or swinepox virus (CIL) gp38 cDNA under the control of a high efficiency promoter (e.g., the T7 promoter). Administration of Yatapoxvirus or swinepox virus (CIL) gρ38 mRNA to malignant cells is carried out by any of the methods for direct nucleic acid administration described above. Transgenic Animals Transgenic animals may be made using standard techniques (see for example, Gene Targeting: A Practical Approach, A. L. Joyner, ed., Oxford University Press, 1999). For example, a Yatapoxvirus gp38 gene may be provided using endogenous control sequences or using constitutive, tissue- specific, or inducible regulatory sequences. Transgenic animals lacking functional Yatapoxvirus or swinepox virus (CIL) gp38 homolog polypeptide may also be made using standard techniques. This may be done by engineering knock-out mutations in the Yatapoxvirus or swinepox vims (CIL) gp38 homolog gene using DNA sequences provided herein. Yatapoxvirus Knockouts Poxviruses are among the largest eukaryotic DNA viruses and have the unusual capacity to replicate autonomously in the cytoplasm of infected cells. Many poxvirus proteins have been defined as virulence factors on the basis that, when present, they confer increased pathogenicity and improve viral replication within immunocompetent hosts. When genes that encode these virulence factor proteins are deleted, the resulting virus strain generally exhibits an attenuated or altered disease phenotype (Turner, Curr. Top. Microbiol. Immunol, 163: 125-151 , 1990; Buller, Microbiol. Rev., 55:80-122, 1991 ; Smith, J. Gen. Virol, 74: 1725- 1740; McFadden, Austin (TX): R. G. Landes Company, 1995, incorporated herein by reference). Such "knockout" Yatapoxviruses may assist in the elucidation of the immunomodulatory or other role of viral proteins. Using standard virological assays (e.g., Nash et al, (1999) Immunological Review, 57:731), one of ordinary skill in the art may establish the contribution of each gene to Yatapoxvirus infection and the general biochemical and physiological progression of viral infection. Knockout Yatapoxviruses lacking a particular gene may be generated using standard molecular biological techniques (see Sambrook et al, supra; Innis et al, PCR Protocols: A Guide to Methods and Applications, Academic Press, San Diego, CA, 1990; Erlich et al, PCR Technology: Principles and Applications for DNA Amplification, Stockton Press, New York, NY, 1989 each of which is incorporated herein by reference). The virulence of these knockout viruses may be assessed using standard infectivity assays well known in the art (see Nash et al, supra). For example, as mentioned above, the gp38 polypeptide of Yatapoxviruses (SEQ ID NOs: 1 or 2) can be useful in elucidating the mechanism used by Yatapoxviruses and other poxviurses to inhibit inflammation. Diagnostic Methods Employing Yatapoxyirus or swinepox vims (CIL) gp38 Nucleic Acid Molecules, Polypeptides, and Antibodies Yatapoxvirus or swinepox virus (CIL) gp38 polypeptides and nucleic acid molecules can be used in the detection or monitoring of inflammatory, autoimmune, and other conditions. For example, because Yatapoxvirus or swinepox virus (CIL) gp38 proteins may be involved in leukocyte chemotaxis, and because a decrease in the number of leukocytes correlates with immunosuppression, an alteration in the level of particular Yatapoxvirus or swinepox virus (CIL) gp38 protein production provides an indication of the prognosis of the condition. Levels of Yatapoxvirus or swinepox virus (CIL) gp38 protein expression may be assayed by any standard technique. For example, its expression in a biological sample (e.g., a biopsy) may be monitored by standard Northern blot analysis or may be aided by PCR (see, e.g., Ausubel et al, supra; Yap and McGee, Niicl. Acids. Res. 19:4294, 1991). In yet another approach, immunoassays are used to detect or monitor Yatapoxvirus or swinepox virus (CIL) gp38 protein in a biological sample. Yatapoxvirus gp38 protein-specific polyclonal or monoclonal antibodies (produced as described herein) may be used in any standard immunoassay format (e.g., ELISA, Western blot, or RIA assay) to measure Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide levels. A change in Yatapoxvirus or swinepox virus (CIL) gp38 protein production may be indicative of a particular prognosis. Examples of immunoassays are described, e.g., in Ausubel et al, supra. Immunohistochemical techniques may also be utilized for Yatapoxvirus or swinepox virus (CIL) gp38 protein detection. For example, a tissue sample may be obtained from a patient, and a section stained for the presence of Yatapoxvirus or swinepox vims (CIL) gp38 protein using an anti- Yatapoxvirus or swinepox virus (CIL) gp38 protein antibody and any standard detection system (e.g., one which includes a secondary antibody conjugated to horseradish peroxidase). General guidance regarding such techniques can be found in, e.g., Bancroft and Stevens {Theory and Practice of Histological Techniques, Churchill Livingstone, 1982) and Ausubel et al (supra). Identification Of Molecules That Modulate Yatapoxyirus or swinepox virus (CIL) gp38 Biological Activity Or Whose Biological Activity Is Modulated By Yatapoxx'irus or swinepox virus (CIL) gp38 Vims Isolation of the Yatapoxvirus or swinepox virus (CIL) gp38 nucleic acid molecule sequence also facilitates the identification of molecules that increase or decrease a Yatapoxvirus gp38 or swinepox virus (CIL) polypeptide biological activity. Similarly, molecules whose activity is modulated by a Yatapoxvirus or swinepox virus (CIL) gρ38 polypeptide biological activity can be identified. These molecules can be tested using assays described herein, e.g., chemotaxis assays. A molecule which promotes an increase in Yatapoxvirus or swinepox virus (CIL) gp38 protein expression or a decrease in leukocyte chemotaxis activity is considered particularly useful in the invention; such a molecule may be used, for example, as a therapeutic to decrease the immunoreactivity in a individual. According to one approach, candidate molecules are added at varying concentrations to the culture medium of cells expressing Yatapoxvirus or swinepox virus (CIL) gp38 mRNA. Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide biological activity is then measured using standard techniques. The measurement of biological activity can include the measurement of Yatapoxvirus or swinepox vims (CIL) gρ38 polypeptide protein and nucleic acid molecule levels, or the effect of Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide on immunomodulation If desired, the effect of candidate modulators on expression can, in the alternative, be measured at the level of Yatapoxvirus or swinepox virus (CIL) gp38 protein production using the same general approach and standard immunological detection techniques, such as western blotting or immunoprecipitation with a Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide-specific antibody (see below). Candidate modulators can be purified (or substantially purified) molecules or can be one component of a mixture of compounds (e.g., an extract or supernatant obtained from cells; Ausubel et al, supra). In a mixed compound assay, Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide expression is tested against progressively smaller subsets of the candidate compound pool (e.g., produced by standard purification techniques, e.g., HPLC or FPLC) until a single compound or minimal compound mixture is demonstrated to modulate Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide expression. Alternatively, or in addition, candidate compounds can be screened for those that modulate Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide activity. In this approach, the level of immunomodulation in the presence of a candidate compound is compared to the level of immunomodulation in its absence, under equivalent conditions. Again, such a screen can begin with a pool of candidate compounds, from which one or more useful modulator compounds is isolated in a step-wise fashion. The screening assays described above can be carried out in a variety of ways that are well known to those skilled in this art. These include using Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide variants or by using fragments of a Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide. A test compound that can be screened in the methods described above can be a chemical, be it naturally-occurring or artificially-derived. Such compounds can include, for example, polypeptides, synthesized organic molecules, naturally occurring organic molecules, nucleic acid molecules, and components thereof. Candidate Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide modulators include peptide as well as non-peptide molecules (e.g., peptide or non-peptide molecules found, e.g., in a cell extract, mammalian serum, or growth medium in which mammalian cells have been cultured). In general, novel drugs for prevention or treatment of immunomodulatory diseases are identified from large libraries of both natural products, synthetic (or semi-synthetic) extracts, and chemical libraries using methods that are well known in the art. Those skilled in the field of drug discovery and development will understand that the precise source of test extracts or compounds is not critical to the screening methods of the invention. Accordingly, virtually any number of chemical extracts or compounds can be screened using these methods. Examples of such extracts or compounds include, but are not limited to, plant-, fungal-, prokaryotic-, or animal-based extracts, fermentation broths, and synthetic compounds, as well as modifications of existing compounds. Numerous methods are also available for generating random or directed synthesis (e.g., semi-synthesis or total synthesis) of any number of chemical compounds, including, but not limited to, saccharide-, lipid-, peptide-, and nucleic acid molecule-based compounds. Synthetic compound libraries are commercially available from Brandon Associates (Merrimack, NH) and Aldrich Chemical (Milwaukee, WI). Alternatively, libraries of natural compounds in the form of bacterial, fungal, plant, and animal extracts are commercially available fiom a number of sources, including Biotics (Sussex, UK), Xenova (Slough, UK), Harbor Branch Oceanographic Institute (Ft. Pierce, FL), and PharmaMar, U.S.A. (Cambridge, MA). In addition, natural and synthetically produced libraries are produced, if desired, according to methods known in the art, e.g., by standard extraction and fractionation methods. Furthermore, if desired, any library or compound can be readily modified using standard chemical, physical, or biochemical methods. In addition, those skilled in the art of drug discovery and development readily understand that methods for dereplication (e.g., taxonomic dereplication, biological dereplication, and chemical dereplication, or any combination thereof) or the elimination of replicates or repeats of materials already known for their therapeutic activities for immunological disorders can be employed whenever possible. When a crude extract is found to regulate immunomodulation, further fractionation of the positive lead extract can be carried out to isolate chemical constituents responsible for the observed effect. Thus, the goal of the extraction, fractionation, and purification process is the careful characterization and identification of a chemical entity within the crude extract having a desired activity. The same assays described herein for the detection of activities in mixtures of compounds can be used to purify the active component and to test derivatives thereof. Methods of fractionation and purification of such heterogenous extracts are known in the art. If desired, compounds shown to be useful agents for treatment are chemically modified according to methods known in the art. Compounds identified as being of therapeutic value can be subsequently analyzed using, for example, any of the animal models described herein. The above approaches may also be used to inhibit the activity of the candidate compound by substituting an altered Yatapoxvirus or swinepox virus (C IL) gp38 polypeptide having Yatapoxvirus or swinepox virus (CIL) gp38 protein blocking activity (e.g. , have a deletion or insertion at the amino terminus) for the Yatapoxvirus or swinepox virus (C IL) gp38 polypeptide described above. Animal Models Immunomodulators of this invention and other compounds found to be effective at the level of Yatapoxvirus or swinepox virus (CIL) gp38 protein expression or activity are tested in animal models, for efficacy in treating, for example, autoimmune and inflammatory diseases and cancer. Animal models for testing the immunomodulatory effects of candidate compounds are well known in the art. Therefore, the present invention refers to a selection of animal models that can be used to test the candidate compounds of the invention. Animal models proposed for use in the present invention to test candidate compounds for their efficacy in treating autoimmune and inflammatory disorders include, but are not limited to: Acute inflammation: Animal models of acute inflammation are targeted for initial and rapid drug efficacy screening, and for their potential predicative value of outcomes in chronic inflammatory diseases. The following animal models can be used to test the candidate compounds of the present invention for their efficacy in treating acute inflammation: 1) carrageenin-induced inflammation model; 2) turpentine- induced inflammation model; 3) transgenic HLAB-27 inflammation model; and 4) ear-scratch model of inflammation. Rheumatoid arthritis: rat, mouse, rabbit Efficacy in Rheumatoid Arthritis evaluated in: 1) various antigen-induced arthritis models in rabbit, rat, and mouse; and 2) in transgenic rheumatological models. The molecular and cellular mechanisms of action of the candidate compounds are evaluated by testing their efficacy in influencing key intracellular mechanisms that regulate degradative processes involved in joint disease. Important molecular- and cellular mechanisms that receive particular attention include signaling events regulating disease processes such as increased angiogenesis, synovial hyperplasia, and matrix metalloprotease expression. These processes have been implicated in cartilage degradation in arthritic diseases. 1. Collagen-induced arthritis: rat, mouse, rabbit Autoimmune-mediated polyarthritis can be induced in certain strains of rodents (rat, mouse and rabbit) and non-human primates by immunizing them with native type II collagen. The collagen-induced arthritis model is widely used and well characterized. Collagen-induced arthritis is mediated by susceptibility to autoantibodies which bind to a particular region of type II collagen. The mechanism of induction is linked to MHC-class II molecules but also depends on the species of type II collagen used for immunization. 2. Ovalbumin-induced arthritisa; rabbit Candidate compounds are tested for efficacy in decreasing signs and symptoms of ovalbumin arthritis. Polyarthritis is induced in rabbits by immunizing them with Ovalbumin. 3. Adjuvant-induced arthritis: rat, mouse, rabbit Candidate compounds are tested for the efficacy in decreasing signs and symptoms of adjuvant-induced arthritis. Polyarthritis is induced in certain strains of rodents by immunizing them with Freud's Adjuvant. 4. Streptococcal cell wall-induced arthritis: rat Candidate compounds are tested for efficacy in decreasing signs and symptoms of streptococcal cell wall-induced arthritis. Chronic, erosive polyarthritis is induced by intraperitoneal injection of an aqueous suspension of cell wall fragments isolated from group A streptococci. Transplant rejection (acute and chronic) Efficacy in transplant rejection is evaluated in various models of graft vascular disease (GVD). GVD is the most common cause of late graft failure in solid organ transplantation. GVD or graft atherosclerosis is characterized by plaque formation and fibrosis in small vessels. The development of graft vascular disease has been associated with acute allograft rejection, ischemia-reperfusion injury, and bacterial or viral infections. The common pathway of these postoperative insults results in perivascular inflammation which triggers migration of mesenchymal cells into the vessel wall, eventually resulting in occlusion or partial occlusion of the vessel lumen. 1. Aortic allograft model: rat, rabbit, monkey Candidate compounds are tested for efficacy in reducing graft atherosclerosis and transplant rejection in a model of vascular injury after transplantation of aortic segments performed in certain strains of MHC mismatched rats, monkeys, and rabbits. 2. Tracheal allograft model: rat, rabbit, monkey Candidate compounds are tested for efficacy in reducing graft atherosclerosis and transplant rejection in a model of vascular injury after transplantation of tracheal segments performed in certain strains of MHC mismatched rats, rabbits, and monkeys. 3. Heterotopic heart transplant: mouse, rat, monkey A hetero tropic heart transplantation is performed in MHC mismatched animals. In this model, animals are treated with cyclosporine A for only the first 7 days after transplantation are allowed to develop graft vasculai" disease, and are then analyzed after sacrifice at postoperative day 90. 4. Orthotopic kidney transplant: mouse, rat, monkey An orthotopic kidney transplantation is performed in MHC mismatched animals. In this model, animals receiving subtherapeutic doses of cyclosporine A for the first 10 days after transplantation are allowed to exhibit features of chronic renal allograft rejection in 70% of cases, and are then analyzed after sacrifice at postoperative day 90. 5. Orthotopic lung transplant: rat, monkey Candidate compounds are tested for effectiveness in delaying or reducing signs and symptoms of organ rejection after lung whole organ transplantation in rats and monkeys. 6. Reperfusion injury: rat The immediate postoperative course in clinical lung transplantation is often severely impaired by delayed graft function as a result of ischemia and reperfusion injury. Preventive efficacy of drug candidates in ischemia- reperfusion injury is evaluated using a model of acute in vivo double lung transplantation in the rat (Hausen et al, Ann, Thorac. Surg. 61:1714-9, 1996 incorporated herein by reference). Restenosis Candidate compounds are tested for efficacy in reducing atherosclerotic plaque deposition in a model of coronary restenosis after balloon angioplasty. Atherosclerotic plaque formation is critically involved in vascular occlusion and has been linked to excessive inflammatory and thrombotic response to arterial injury. Asthma: rodent The effectiveness of candidate compounds in reduction of signs and symptoms of asthma is evaluated in rodent models of antigen-induced experimental airways inflammation. The models include: 1. Ovalbumin-induced experimental airways inflammation: rodent Candidate compounds are tested for efficacy in reducing inflammatory cell components in the bronchoalveolar lavage of the lungs after aerosol challenge in ovalbumin-sensitized rodent models of experimental airways inflammation. 2. Ovalbumin-induced allergic sensitization in presence of GM-CSF transgene expression: mice Candidate compounds are tested for efficacy in reducing inflammatory cell components in the bronchoalveolar lavage of the lungs of mice after ovalbumin aerosol challenge in the context of local expression of GM-CSF (Staempfli et al, J. Clin. Invest., Vol. 102:9, 1704-1714). Inflammatory bowel disease (IBD): mice and rats Drug candidates are evaluated for their potential therapeutic efficacy in ulcerative colitis or Crohn's disease utilizing various models of antigen-induced and genetically-mediated spontaneous chronic intestinal inflammation in mice and rats. Examples include: 1. Dextran sulfate sodium induced IBD: mice Chronic, irreversible clinical symptoms of IBD are induced by treating mice with an oral administration of dextran sulfate sodium. 2. Gene deletion and transgenic models for IBD: rodent Compound efficacy will be tested in transgenic rodent lines which develop symptoms closely resembling the human elements of inflammatory bowel disease. Models include, the targeted deletion of the genes encoding IL-2, IL-10, TGF beta, T-cell receptor, alpha/beta, keratin 8, Gi2 alpha. In addition, animals expressing transgenes for the human WA-B27 and HLA-B27 as well as a dominant negative construct which functionally blocks N-cadherin will be tested. Uveitis Drug candidates will be evaluated for efficacy in various animal models of uveitis. Key models include both, experimental autoimmune uveitis and adoptively transferred experimental autoimmune uveitis. 1. Experimental autoimmune uveitis (EAU) EAU is a T-cell mediated inflammatory eye disease that can be induced in several mammalian species by immunization with ocular-specific antigens (Gery et al, Invest. Opthalmol. Vis. Sci., 27: 1296-1300, 1986,. Sanui t al, J Exp. Med., 169:1947-1989, incorporated herein by reference). This experimental disease is considered a model for a family of inflammatory eye diseases in humans and has been used to examine numerous modalities before their human testing. 2. Adoptively transferred experimental autoimmune uveitis Adoptively transferred EAU is induced through injection of lymphocytes presensitized against the retinal antigen are injected into naive syngenic recipients (McAllister et al, J. Immunol, 138: 1416-1420, 1987 incorporated herein by reference) Yatapoxyirus or swinepox virus (CIL) gp38 Protein Expression In general, Yatapoxvirus or swinepox vims (CIL) gp38 may be produced by transformation or transfection of a suitable host cell with all or part of a Yatapoxvirus or swinepox virus (C IL) gp38 protein-encoding cDNA fragment in a suitable expression vehicle. Those skilled in the field of molecular biology will understand that any of a wide variety of expression systems may be used to provide the recombinant protein. The precise host cell used is not critical to the invention. The Yatapoxvirus or swinepox virus (CIL) gp38 protein may be produced in a prokaryotic host (e.g., E. coli) or in a eukaryotic host (yeast cells, e.g., Saccharomyces cerevisiae, insect cells, e.g., S 21 cells, or mammalian cells, e.g., COS 1, NIH 3T3, or HeLa cells). Such cells are available from a wide range of sources (e.g., the American Type Culture Collection, Rockland, MD; also, see, e.g., Ausubel et al, supra). The method of transformation or transfection and the choice of expression vehicle will depend on the host system selected. Transformation and transfection methods are described, e.g., in Ausubel et al. (supra); expression vehicles may be chosen from those provided, e.g., in Cloning Vectors: A Laboratoiγ Manual, P.H. Pouwels et al, 1985, Supp. 1987). One preferred expression system is the baculovirus system (using, for example, the vector pBacPAK9) available from Clontech (Pal Alto, CA). If desired, this system may be used in conjunction with other protein expression techniques, for example, the myc tag approach described by Evan et al. (Mol. Cell Biol. 5:3610-3616, 1985). Alternatively, a Yatapoxvirus or swinepox virus (CIL) gp38 protein is produced by a stably-transfected mammalian cell line. A number of vectors suitable for stable transfection of mammalian cells are available to the public, e.g., see Pouwels et al. (supra); methods for constructing such cell lines are also publicly available, e.g., in Ausubel et al. (supra). In one example, cDNA encoding the Yatapoxvirus or swinepox virus (CIL) gp38 protein is cloned into an expression vector which includes the dihydrofolate reductase (DHFR) gene. Integration of the plasmid and, therefore, the Yatapoxvirus or swinepox virus (CIL) gp38 protein-encoding gene into the host cell chromosome is selected for by inclusion of 0.01-300 mM methotrexate in the cell culture medium (as described in Ausubel et al, supra). This dominant selection can be accomplished in most cell types. Recombinant protein expression can be increased by DHFR- mediated amplification of the transfected gene. Methods for selecting cell lines bearing gene amplifications are described in Ausubel et al. (supra); such methods generally involve extended culture in medium containing gradually increasing levels of methotrexate. DHFR-containing expression vectors commonly used for this purpose include pCVSEII-DHFR and pAdD26SV(A) (described in Ausubel et al, supra). Any of the host cells described above or, preferably, a DHFR- deficient CHO cell line (e.g., CHO DHFR- cells, ATCC Accession No. CRL 9096) are among the host cells preferred for DHFR selection of a stably- transfected cell line or DHFR-mediated gene amplification. Once the recombinant Yatapoxvirus or swinepox virus (C IL) gp38 protein is expressed, it is isolated, e.g., using affinity chromatography. In one example, an anti-Yatapoxvirus or swinepox virus (C IL) gp38 protein antibody (e.g., produced as described herein) is attached to a column and used to isolate the Yatapoxvirus or swinepox virus (CIL) gp38 protein. Lysis and fractionation of Yatapoxvirus or swinepox virus (C IL) gp38 protein-harboring cells prior to affinity chromatography are performed by standard methods (see, e.g., Ausubel et al, supra). In another example, Yatapoxvirus or swinepox vims (CIL) gp38 proteins are purified or substantially purified from a mixture of compounds such as an extract or supernatant obtained from cells (Ausubel et al, supra). Standard purification techniques can be used to progressively eliminate undesirable compounds from the mixture until a single compound or minimal number of effective compounds has been isolated. Once isolated, the recombinant protein can, if desired, be further purified, e.g., by high performance liquid chromatography (see, e.g. , Fisher, Laboratory Techniques In Biochemistry And Molecular Biology, eds., Work and Burdon, Elsevier, 1980). Polypeptides of the invention, particularly short Yatapoxvirus or swinepox virus (CIL) gp38 protein fragments, can also be produced by chemical synthesis (e.g., by the methods described in Solid Phase Peptide Synthesis, 2nd ed., 1984 The Pierce Chemical Co., Rockford, IL). These general techniques of polypeptide expression and purification can also be used to produce and isolate useful Yatapoxvirus or swinepox virus (CIL) gp38 protein fragments or analogs (described herein). Yatapoxvirus or swinepox virus (C IL) gp38 polypeptides can be attached to any one of a variety of tags. Tags can be amino acid tags or chemical tags and can be added for the purpose of purification (for example a 6-histidine tag for purification over a nickel column). Various labels can be used as means for detecting binding of a Yatapoxvirus or swinepox virus (C I L) gp38 protein to another protein, for example to a chemokine or a chemokine receptor. Alternatively, Yatapoxxnrus or swinepox virus (CIL) gp38 DNAs or RNAs may be labeled for detection, for example in a hybridization assay. Yatapoxvirus or swinepox virus (C IL) gp38 nucleic acids or polypeptides, or derivatives thereof, may be directly or indirectly labeled, for example, with a radioisotope, a fluorescent compound, a bioluminescent compound, a chemiluminescent compound, a metal chelator or an enzyme. Those of ordinary skill in the art will know of other suitable labels or will be able to ascertain such, using routine experimentation. Yatapoxvirus or swinepox virus (CIL) gp38 polypeptides can also be linked to toxins. Proteins linked to toxins can be used, for example to target toxic drugs to malignant tumors if the protein has the ability localize to the tumor. To generate Yatapoxvirus gp38 protein-specific antibodies, a Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide coding sequence (e.g.., gp38 from TPV, YMTV, or swinepox virus (CIL)) is expressed, for example, as a C-terminal fusion with glutathione S-transferase (GST) (Smith et al, Gene 67:31- 40, 1988). The fusion protein is then purified on glutathione-Sepharose beads, eluted with glutathione cleaved with thrombin (at the engineered cleavage site), and purified to the degree necessary for immunization of rabbits. Primary immunizations are carried out with Freud's complete adjuvant and subsequent immunizations with Freud's incomplete adjuvant. Antibody titres are monitored by Western blot and immunoprecipitation analysis using the thrombin-cleaved Yatapoxvirus or swinepox virus (CIL) gp38 protein fragment of the GST -Yatapoxvirus or swinepox virus (CIL) gp38 fusion protein. Immune sera are affinity purified using CNBr-Sepharose-coupled Yatapoxvirus or swinepox virus (CIL) gp38 protein. Antiserum specificity is determined using a panel of unrelated GST proteins and GST-trypsin (which was generated by PCR using known sequences). As an alternate or adjunct immunogen to GST fusion proteins, peptides corresponding to relatively unique hydrophilic Yatapoxvirus or swinepox vims (C IL) gp38 proteins may be generated and coupled to keyhole limpet hemocyanin (KLH) through an introduced C-terminal lysine. Antiserum to each of these peptides is similarly affinity purified on peptides conjugated to BSA, and specificity tested in ELISA and Western blots using peptide conjugates, and by Western blot and immunoprecipitation using Yatapoxvirus or swinepox virus (CIL) gp38 protein expressed as a GST fusion protein. Alternatively, monoclonal antibodies may be prepared using the Yatapoxvirus or swinepox virus (CIL) gp38 proteins described above and standard hybridoma technology (see, e.g., Kohler et al, Nature, 256:495, 1975; Kohler et al, Eur. J. Immunol 6:511, 1976; Kohler et al, Eur. J. Immunol 6:292, 1976; Hammerling et al, In Monoclonal Antibodies and T Cell Hybridomas, Elsevier, NY, 1981; Ausubel et al, supra). Once produced, monoclonal antibodies are also tested for specific Yatapoxvirus or swinepox virus (CIL) gp38 protein recognition by Western blot or immunoprecipitation analysis (by the methods described in Ausubel et al, supra). Antibodies which specifically bind Yatapoxvirus or swinepox virus (CIL) gp38 proteins are considered to be useful in the invention; such antibodies may be used, e.g., in an immunoassay to monitor the level of Yatapoxvirus gρ38 proteins produced by a mammal (for example, to determine the amount or location of a Yatapoxvirus or swinepox virus (CIL) gp38 protein). Preferably, antibodies of the invention are not only produced using the whole Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide, but using fragments of the Yatapoxvirus or swinepox virus (CIL) gp38 polypeptide that lie outside highly conserved regions and appear likely to be antigenic, by criteria such as high frequency of charged residues may also be used. In one specific example, such fragments are generated by standard techniques of PCR and cloned into the pGEX expression vector (Ausubel et al, supra). Fusion proteins are expressed in E. colt and purified using a glutathione agarose affinity matrix as described in Ausubel et al. (supra). To attempt to minimize the potential problems of low affinity or specificity of antisera, two or three such fusions are generated for each protein, and each fusion is injected into at least two rabbits. Antisera are raised by injections in a series, preferably including at least three booster injections. Antibodies to Yatapoxvirus or swinepox virus (CIL) proteins can be used to detect Yatapoxvirus or swinepox virus (CIL) proteins. In addition, the antibodies can be coupled to compounds, such as radionuclides and liposomes for diagnostic or therapeutic uses. EXAMPLES Cloning Additional Yatapoxvirus-Related gp38 Genes. Standard techniques, such as the polymerase chain reaction (PCR) and DNA hybridization, can be used to clone Yatapoxvirus-r elated gp38 genes. Yatapoxvirus-Related gp38 genes and homologs can be readily identified using low-stringency DNA hybridization or low-stringency PCR with specific probes or primers. Degenerate primers Yatapoxvirus-r elated gp38 amino acid sequences can be used to clone additional Yatapoxvirus-r elated gp38 genes and homologs by RT-PCR. Based on the amino acid sequences provided by the present invention, degenerate oligonucleotide primers containing restriction sites are synthesized. First strand cDNA is synthesized from RNA prepared from a tissue of interest and PCR is performed with an initial five cycle step, for example, at 37°C for 60s, followed by 25 cycles at 50°C for 60s (denaturation at 95°C for 30s and extension at 72°C for 90s) in order to amplify a Yatapoxvi ru A-elated gp38 cDNA fragment that can be subsequently subcloned into Bluescript II KS (Stratagene). Construction of a cDNA library using poly A RNA isolated from the selected tissue is performed using Stratagene ZAP Express Vector according to the directions of the manufacturer. Potential clones are subsequently amplified and an aliquot of this cDNA library containing phage is screened with the Yatapoxvirus gp38 cDNA that has been 32 P-labeled with Klenow enzyme. Isolated phagemids are subsequently subjected to automated sequencing on both strands using Applied Biosystems Instrumentation (model 373a) and the dye-terminator protocol. Sequence analysis is performed using software developed, for example, by the University of Wisconsin genetics computer group (Altschul, et al J. Mol. Biol. 215:403-410, 1990). Yatapoxvirus gp38 mRNA Expression in Different Organs. Northern blot analysis of total RNA isolated from different mammalian tissue samples is performed to detect expression of any Yatapoxvirus gp38 gene, homolog or derivative. Mammalian tissues including the brain, bone marrow, skin, intestines, stomach, heart, thymus, lymph node, mammary gland, skeletal muscle, tongue, spleen, liver, testes, and kidney are analyzed. Likewise, cell lines, such as macrophages isolated and cultured from the spleen, a lung epithelial cell line, and a colon adenocarcinoma cell, are analyzed for expression of Yatapoxvirus gp38 mRNA. DNA and RNA analysis. RNA is isolated by CsCl centrifugation in guanidine isothiocyanate (Chirgwin, et al. (1979) Biochemistry. 18:5294-9). Biologically active ribonucleic acid is isolated from sources enriched in ribonuclease. DNA is isolated from these gradients as well. In some cases, RNA is isolated using RNAzol (Biotecx Lab, Inc.) according to the directions of the manufacturer. Poly A RNA is enriched by elution through an oligo dT column (Pharmacia). For example, 10 μg of total RNA, 2 μg of poly A RNA, or 10 μg of restriction endonuclease cut DNA is electrophoresed in agarose, and transferred to Gene Screen (NEN Dupont) membranes. Membranes will be hybridized with ' " P labeled full length cDNA or a fragment encoding the translated protein. High stringency hybridization is performed, for example, in 50% formamide, 10% dextran sulfate, 5X SSC, IX Denhardt's solution (0.0002% (w/v) polyvinylpyirolidone, 0.0002% (w/v) BSA, 0.0002% (w/v) Ficoll 400), 1% (w/v) SDS, 100 μg /ml denatured heiring sperm DNA, and 20mM Tris at 42°C and blots are washed with 0.2X SSC, 0.5% SDS at 65oC. Low stringency hybridization is performed, for example, in 0.6M NaCl, 80mM TrisCl, 4mM EDTA, 0.1% (w/v) sodium pyrophosphate, 0.1% (w/v) SDS, 10X Denhardts, 100 μg /ml denatured heiring sperm DNA at 50°C and washed with 1XSSC, 0.05% SDS at 50°C. Quantitation of the intensity of band hybridization will be determined using a Phosphor-Imager (Molecular Dynamics). Yatapoxvirus gp38 Gene Analysis. A cDNA probe from the coding region of the Yatapoxvirus gp38 cDNA is 32 P-labeled with Klenow enzyme and used to screen approximately 1 X 10 6 plaques from a mammalian genomic library (e.g., a variety of libraries are available from Stratagene, La Jolla, CA) under conditions of low stringency (hybridization in 0.6 M NaCl, 80mM TrisCl, 4mM EDTA, 0.1% sodium pyrophosphate, 0.1% SDS, 10X Denhardfs solution (0.002% polyvinylpyrrolidone, 0.002% BSA, 0.002% Ficoll 400), lOOμg/ml denatured herring sperm DNA at 50°C and blots washed with IX SSC, 0.05% SDS at 50°C). Plaques that hybridize strongly are purified. The genomic DNA is liberated from the phage DNA by restriction digestion with the appropriate enzymes and sub-cloned into pBlue- Script SK II (Stratagene). Any positively identified genomic fragment that hybridizes with the probe is subcloned into, for example, pBlue-Script KS II, and subjected to automated sequencing on both strands using Applied Biosystems Instrumentation (model 373a) and the dye-terminator protocol. Sequence analysis is performed using software developed by, for example, the University of Wisconsin genetics computer group Altschul et al, J. Mol. Biol. 215:403-410, 1990. The Yatapoxvirus gp38 gene homolog chromosomal localization is determined by the analysis of any identified polymorphisms in the gene. PCR primers flanking this polymorphism will be constructed and genomic DNA is amplified by PCR. Using these primers, a size polymorphism is identified (for example, see Rowe, et al, Manun. Gen. 5: 253-274, 1994). The identified genomic fragment can be used to screen a mammalian cDNA expression library (Stratagene) under conditions of high stringency (hybridization in 50% formamide, 10% dextran sulfate, 5X SSC, IX Denhardt's solution, 1% SDS, 100 mcg/ml denatured heiring sperm DNA, and 20mM Tris at 42°C and blots were washed with 0.2X SSC, 0.5% SDS at 65°C). Positive plaques are identified, purified, and phagemids are prepared according to the instructions of the library manufacturer. The inserts are completely sequenced on both strands by automated sequencing. Alignment analysis will be determined by the Clustal method using MegAlign software (DNASTAR Inc) (Higgins, et al. (1988) Gene 73, 237-244), or other standard software. Construction and Transfection of Protein Expression Vectors. PCR primers are designed to amplify the coding region of the Yatapoxx'irus gp38 gene, or homolog or derivative thereof, flanked by convenient restriction sites for subsequent sub-cloning. PCR is performed under standard conditions using Yatapoxvirus gp38 cDNA-pBlueScript as a template. The resulting PCR products are subsequently subcloned using, for example, a TA cloning kit (Invitrogen, San Diego, CA) and confirmatory sequencing is performed. Yatapoxvirus gp38 cDNA is subcloned into the available restriction sites of pcDNA-I/Amp (Invitrogen). Approximately 4 μg of the Yatapoxvirus gp38-pcDNA-I construct is transfected into 100 mm plates containing -30% confluent COS cells using DEAE-Dextran (Lopata, et al, Nucl Acids Res. 12, 5707-5717, 1984). In order to measure transfection efficiency, a replicate sample of COS cells will be transfected with a CMV promoter-placental alkaline phosphatase control plasmid (Fields-Berry et al, Proc. Natl. Acad. Sci. U.S.A. 89: 693-697, 1992). RNA expression is confirmed by Northern analysis using the Yatapoxvirus gp38 cDNA as a probe. Yatapoxvirus gp38 -pcDNA-I transfected or mock transfected COS cell supernatant is obtained after 72 firs of culture and stored at 4°C. In another set of transfection experiments, Yatapoxvirus gp38 cDNA is similarly subcloned into the available site of MoLTR-S V40 I/PA expression vector (for example, see Luster, et al, J. Exp. Med. 178, 1057-1065, 1993). 20 μg of linearized Yatapoxvirus gp38-MoLTR construct and lμg of linearized neomycin resistance plasmid pSV7Neo is used to transfect J558L cells by electroporation. G418 resistant cells from single wells are analyzed for Yatapoxvirus gp38 mRNA expression by Northern analysis. Cells expressing Yatapoxvirus gp38 protein or control untransfected cells (that do not express Yatapoxvirus gp38 protein) will be expanded in large cultures. In order to optimize the concentration of Yatapoxvirus gp38 protein in the supernatant, the cells are grown at high density (1 X 106 cells/ml) in RPMI without FCS, cultured for 72 firs, and the conditioned medium is concentrated 5-fold with Centricon 3000 microconcentrators (Amicon, Beverly, MA) before being stored. Chemotaxis Assays. Leukocytes, for example eosinophils, are isolated. Eosinophils, in particular, can be isolated from IL-5 transgenic mice (Dent, et al, J. Exp. Med. 172:1425-1431, 1990). These mice develop splenomegaly, with eosinophils accounting for -30% of the splenocytes. Eosinophils are purified from the spleen using immuno-magnetic separation to remove the contaminating splenocytes. Briefly, splenocytes are labeled with anti-Thy-1 (M5/49), anti-B220 (6B2), and anti-Lyt-2 (53-6.7). Hybridoma cell lines are obtained, for example, from American Type Culture Collection and hybridoma cell supernatants are used as a source of antibodies. The antibody labeled cells are treated with anti- serum coated-magnetic beads, the anti-serum having specificity for the isotype of the primary antibody, (M450, Dynal, Great Neck, NY), and eosinophils are enriched by negative selection through a magnetic field. Macrophage cells are isolated from the peritoneal cavity of mice that have been pre-treated (2 days prior) with intraperitoneal injection of 2.9% thioglycollate (Difco, Detroit, CA). Peritoneal neutrophils are isolated from mice pre-treated with sodium casein (Luo, et al, J. Ininiun. 153, 4616-4624, 1994). Macrophages and neutrophils are purified by Percoll gradients (Luo, et al, J. Immun. 153, 4616-4624, 1994. Eosinophils or macrophages are suspended in HBSS with 0.05% BSA at 2 X 106 cells/ml, respectively, and 50 ml of replicate cells are placed in the top well of a 48 well micro-chemotaxis chamber (Neuro Probe, Inc, Cabin John, MD). A polycarbonate filter with 5-μm pores are used to separate the cells from buffer (30 ml) alone or buffer containing recombinant COS cell supernatant and a positive (for example MCP- 1 (Rollins, & Pober, Am. J. Path., 138, 1315- 1319, 1991)) and negative control (for example, supernatant from mock-transfected COS cells) so that a comparison can be made and the immunosuppressive (inhibition of chemotaxis) properties of the Yatapoxvirus gp38 protein assessed. Cells are incubated at 37°C for 60 minutes (eosinophils and neutrophils) or 90 minutes (macrophages) and the cells that migrate across the filter and adhere to the bottom side of the filter are stained with Diff-Quick (Baxter Scientific, McGaw Park, IL). The number of cells per 400X field is counted. Statistical Analysis. The statistical significance of differences between means is determined by analysis of variance (ANOVA). P < 0.05 is considered significant. When ANOVA indicates a significant difference, the Newman-Keuls test is used to determine which groups are significantly different from each other. Other Embodiments All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each independent publication or patent application was specifically and individually indicated to be incorporated by reference. While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure come within known or customary practice within the ait to which the invention pertains and may be applied to the essential features hereinbefore set forth, and follows in the scope of the appended claims. What is claimed is:

Claims: CLAIMS 1. A substantially pure Yatapoxvirus immunomodulatory polypeptide. 2. The polypeptide of claim 1, wherein said polypeptide is derived from yaba monkey tumor virus. 3. The polypeptide of claim 1, wherein said polypeptide is derived from tanapox virus. 4. The polypeptide of claim 1, wherein said polypeptide comprises an amino acid sequence that encodes an identifiable signal sequence. 5. The polypeptide of claim 1, wherein said polypeptide is selected from the group consisting of a chemokine binding polypeptide, a cytokine binding polypeptide, an immunomodulator, and an anti-inflammatory polypeptide. 6. The polypeptide of claim 5, wherein said chemokine is selected from the group consisting of human interferon-γ, human interleukin-2, and human interleukin-5. 7. The polypeptide of claim 1, wherein said polypeptide is glycosylated. 8. The polypeptide of claim 1, wherein said polypeptide has anti-cytokine activity. 9. The polypeptide of claim 1, wherein said polypeptide comprises an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6. 10. The polypeptide of claim 9, wherein said polypeptide comprises the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6. 11. A substantially pure Yatapoxvirus nucleic acid molecule, wherein said nucleic acid molecule encodes a Yatapoxvirus immunomodulatory polypeptide. 12. The nucleic acid molecule of claim 11, wherein said nucleic acid molecule is selected from the group consisting of genomic DNA, cDNA, and mRNA. 13. The nucleic acid molecule of claim 11, wherein said nucleic acid molecule comprises a nucleotide sequence that encodes a polypeptide with an identifiable signal sequence. 14. The nucleic acid molecule of claim 11, wherein said nucleic acid molecule encodes a yaba monkey tumor virus polypeptide. 15. The nucleic acid molecule of claim 11, wherein said nucleic acid molecule encodes a tanapox virus polypeptide. 16. The nucleic acid molecule of claim 11, wherein said nucleic acid molecule encodes a polypeptide comprising an amino sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6. 17. The nucleic acid molecule of claim 16, wherein said nucleic acid molecule encodes a polypeptide comprising the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6. 18. The nucleic acid molecule of claim 1 1 , wherein said nucleic acid molecule comprises a nucleotide sequence that is substantially identical to the nucleotide sequence of SEQ ID NO: 3, SEQ ID NO: 5, or SEQ ID NO: 7. 19. A nucleic acid molecule having at least 50% nucleic acid sequence identity to a sequence encoding a Yatapoxvirus immunomodulatory polypeptide or a fragment thereof, wherein said fragment comprises at least six amino acids and said nucleic acid molecule hybridizes under high stringency conditions to at least a portion of a Yatapoxvirus nucleic acid molecule. 20. The nucleic acid molecule of claim 19, wherein said nucleic acid molecule has 100% complementarity to a nucleic acid molecule encoding a Yatapoxvirus immunomodulatory polypeptide or a fragment thereof comprising at least six amino acids, and said nucleic acid molecule hybridizes under high stringency conditions to at least a portion of a Yatapoxvirus nucleic acid molecule, 21. A nucleic acid molecule, wherein said nucleic acid molecule comprises a sequence that is antisense to the coding strand of a Yatapoxvirus nucleic acid molecule or a fragment thereof. 22. A vector comprising the nucleic acid molecule of claim 11. 23. The vector of claim 22, wherein said vector is a gene therapy vector. 24. A cell comprising the vector of claim 22. 25. The vector of claim 22, wherein said nucleic acid molecule is operably linked to regulatory sequences for expression of a Yatapoxvirus polypeptide and wherein said regulatory sequences comprise a promoter. 26. The cell of claim 24, wherein said cell is selected from the group consisting of a human cell, a primate cell, and a rodent cell. 27. A non-human transgenic animal comprising the nucleic acid molecule of claim 11. 28. A cell from the non-human transgenic animal of claim 27. 29. A non-human transgenic animal having a knockout mutation in one or both alleles encoding a polypeptide substantially identical to a Yatapoxvirus polypeptide. 30. An antibody that specifically binds to a Yatapoxvirus polypeptide. 31. The antibody of claim 30, wherein said polypeptide comprises an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6. 32. A probe for analyzing a Yatapoxvirus gene or a Yatapoxvirus gene homolog or fragment thereof, said probe having at least 50% nucleotide sequence identity to a sequence encoding a Yatapoxvirus polypeptide or fragment thereof, wherein said fragment comprises at least six amino acids, and said probe hybridizes under high stringency conditions to at least a portion of a Yatapoxvirus nucleic acid molecule. 33. The probe of claim 32, wherein said probe has 100% complementarity to a nucleic acid molecule encoding a Yatapoxvirus polypeptide or fragment thereof, wherein said fragment comprises at least six amino acids, and said probe hybridizes under high stringency conditions to at least a portion of a Yatapoxvirus nucleic acid molecule. 34. A method of detecting a Yatapoxvirus polypeptide in a sample, said method comprising contacting said sample with the antibody of claim 30, and assaying for the binding of said antibody to said polypeptide. 35. A method of detecting a Yatapoxvirus gene or a Yatapoxvirus gene homolog or fragment thereof in a cell, said method comprising contacting the nucleic acid molecule of claim 11 or a fragment thereof, wherein said fragment is greater than about 18 nucleotides in length, with a preparation of genomic DNA from said cell, under hybridization conditions providing detection of DNA sequences having about 50% or greater nucleotide sequence identity to SEQ ID NO: 3, SEQ ID NO: 5, or SEQ ID NO: 7. 36. A method of identifying an immunomodulatory Yatapoxvirus gene or a Yatapoxvirus immunomodulatory gene homolog or fragment thereof comprising: (a) providing a mammalian cell sample; (b) introducing into said cell sample a candidate gene; (c) expressing said candidate gene; and (d) determining whether said candidate gene elicits an alteration in the level of immune function in said cell sample, wherein an alteration in the level of immune function identifies said immunomodulatory Yatapoxvirus gene or said Yatapoxvirus immunomodulatory gene homolog, or fragment thereof. 37. A method for identifying a test compound that modulates the expression or activity of a Yatapoxvirus polypeptide, said method comprising contacting said Yatapoxvirus polypeptide with said test compound, and determining the effect of said test compound on said Yatapoxvirus polypeptide expression or activity. 38. A method of targeting proteins for secretion from a cell, comprising attaching an identifiable signal sequence selected from a Yatapoxvirus polypeptide to a protein of interest, wherein said protein of interest is secreted from said cell. 39. A method of immunomodulation in a mammal, said method comprising: administering to said mammal a therapeutically effective amount of a Yatapoxvirus polypeptide or fragment thereof, wherein said polypeptide has an immunomodulatory effect in said mammal. 40. A method of immunomodulation in a mammal, said method comprising: administering to said mammal a therapeutically effective amount of a compound that modulates the activity of a Yatapoxvirus polypeptide, wherein said compound has an immunomodulatory effect in said mammal. 41. A method of treating a mammal having an immunomodulatory disorder, said method comprising: administering to said mammal a therapeutically effective amount of a compound that modulates the activity of a Yatapoxvirus polypeptide, wherein said compound has an immunomodulatory effect in said mammal. 42. A pharmaceutical composition comprising at least one dose of a therapeutically effective amount of a Yatapoxvirus polypeptide or fragment thereof, in a pharmaceutically acceptable cairier, said composition being formulated for the treatment of an immunomodulatory disorder. 43. The method of claims 37 to 42, wherein the Yatapoxvirus polypeptide comprises an amino acid sequence substantially identical to the amino acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 4, or SEQ ID NO: 6, and fragments and analogs thereof. 44. The method of claim 39 or 40, wherein said immunomodulation is selected from the group consisting of immunosuppression, immunostimulation, cell proliferation, apoptosis, decreasing T cell stimulation, and decreasing inflammation in a mammal. 45. The method of claims 39 to 41, wherein said mammal is a human. 46. The method of claims 39 to 41, wherein said mammal has a condition selected from the group consisting of acute inflammation, rheumatoid arthritis, transplant rejection, asthma, inflammatory bowel disease, uveitis, restenosis, multiple sclerosis, psoriasis, wound healing, lupus erythematosus, allergic rhinitis, atopic dermatitis, food allergies, type 1 insulin-dependent diabetes mellitus, deramatitis, meningitis, thrombotic thrombocytopenic purpura, Sjogren's syndrome, encephalitis, leukocyte adhesion deficiency, rheumatic fever, Reiter's syndrome, psoriatic arthritic, progressive systemic sclerosis, primary biliary cirrhosis, pemphigus, pemphigoid, necrotizing vasculitis, mayasthenia gravis, lupus erythmatosus, polymyositis, sarcoidosis, granulomatorsis, vasculitis, pernicious anemia, CNS inflammatory disorder, antigen-antibody complex mediated diseases, autoimmune hemolytic anemia, Hashimoto's thyroiditis, Graves disease, habitual spontaneous abortions, Reynard's syndrome, glomerulonephritis, dermatomyositis, chromic active hepatitis, celiac disease, autoimmune complications of AIDS, atrophic gastritis, ankylosing spondylitis, Addison's disease, psoriasis, penphigus vularis, Behcet's syndrome, acute respiratory distress syndrome (ARDS), ischemic heart disease, atherosclerosis, post-dialysis syndrome, leukemia, acquired immune deficiency syndrome septic shock and other type of acute inflammation, and lipid histiocytosis. 47. A kit for the analysis of a Yatapoxvirus nucleic acid molecule, said kit comprising a nucleic acid molecule probe for analyzing a Yatapoxvirus nucleic acid molecule present in a test subject. 48. A kit for the analysis of a Yatapoxvirus polypeptide, said kit comprising an antibody for analyzing a Yatapoxvirus polypeptide present in a test subject. 49. A method for identifying a test compound that modulates the expression or activity of a polypeptide comprising an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 8, said method comprising contacting said polypeptide with said test compound, and determining the effect of said test compound on said polypeptide expression or activity. 50. A method of targeting proteins for secretion from a cell, comprising attaching an identifiable signal sequence selected from a polypeptide comprising an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 8 to a protein of interest, wherein said protein of interest is secreted from said cell. 51. A method of immunomodulation in a mammal, said method comprising: administering to said mammal a therapeutically effective amount of a polypeptide comprising an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 8, or fragment thereof, wherein said polypeptide has an immunomodulatory effect in said mammal. 52. A method of immunomodulation in a mammal, said method comprising: administering to said mammal a therapeutically effective amount of a compound that modulates the activity of a polypeptide comprising an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 8, wherein said compound has an immunomodulatory effect in said mammal. 53. A method of treating a mammal having an immunomodulatory disorder, said method comprising: administering to said mammal a therapeutically effective amount of a compound that modulates the activity of a polypeptide comprising an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 8, wherein said compound has an immunomodulatory effect in said mammal. 54. A pharmaceutical composition comprising at least one dose of a therapeutically effective amount of a polypeptide comprising an amino acid sequence that is substantially identical to the amino acid sequence of SEQ ID NO: 8, or fragment thereof, in a pharmaceutically acceptable cairier, said composition being formulated for the treatment of an immunomodulatory disorder. 55. The method of claims 49 to 54, wherein the polypeptide has an amino acid sequence of SEQ ID NO: 8. 56. The method of claim 51 or 52, wherein said immunomodulation is selected from the group consisting of immunosuppression, immunostimulation, cell proliferation, apoptosis, decreasing T cell stimulation, and decreasing inflammation in a mammal. 57. The method of claims 51 to 53, wherein said mammal is a human. 58. The method of claim 51 to 53, wherein said mammal has a condition selected from the group consisting of acute inflammation, rheumatoid arthritis, transplant rejection, asthma, inflammatory bowel disease, uveitis, restenosis, multiple sclerosis, psoriasis, wound healing, lupus erythematosus, allergic rhinitis, atopic dermatitis, food allergies, type 1 insulin-dependent diabetes mellitus, deramatitis, meningitis, thrombotic thrombocytopenic purpura, Sjogren's syndrome, encephalitis, leukocyte adhesion deficiency, rheumatic fever, Reiter's syndrome, psoriatic arthritic, progressive systemic sclerosis, primary biliary cirrhosis, pemphigus, pemphigoid, necrotizing vasculitis, mayasthenia gravis, lupus erythmatosus, polymyositis, sarcoidosis, granulomatorsis, vasculitis, pernicious anemia, CNS inflammatory disorder, antigen-antibody complex mediated diseases, autoimmune hemolytic anemia, Hashimoto's thyroiditis, Graves disease, habitual spontaneous abortions, Reynard's syndrome, glomerulonephritis, dermatomyositis, chromic active hepatitis, celiac disease, autoimmune complications of AIDS, atrophic gastritis, ankylosing spondylitis, Addison's disease, psoriasis, penphigus vularis, Behcet's syndrome, acute respiratory distress syndrome (ARDS), ischemic heart disease, atherosclerosis, post-dialysis syndrome, leukemia, acquired immune deficiency syndrome septic shock and other type of acute inflammation, and lipid histiocytosis.

Inventors: ESSANI KARIM, MCFADDEN GRANT, ESSANI, KARIM, MCFADDEN, GRANT
Applicants: ESSANI KARIM, MCFADDEN GRANT, VIRON THERAPEUTICS INC, ESSANI, KARIM, MCFADDEN, GRANT, VIRON THERAPEUTICS, INC.
Application year: 2001
Main classification: C12N
IPC codes: A01K67, A61K38, A61K39, A61P1, A61P3, A61P5, A61P7, A61P9, A61P11, A61P13, A61P15, A61P17, A61P19, A61P21, A61P25, A61P29, A61P31, A61P35, A61P37, A61P43, C07K14, C07K16, C12N5, C12N15, C12Q1, G01N33