Patent Publication Number: US-2011077207-A1

Title: Method for treating inflammation

Description:
This application is a continuation of U.S. patent application Ser. No. 09/951,268, filed Nov. 13, 2001, which claims the benefit of U.S. Provisional Application No. 60/233,305 filed on Sep. 15, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     Inflammation normally is a localized, protective response to trauma or microbial invasion that destroys, dilutes, or walls-off the injurious agent and the injured tissue. It is characterized in the acute form by the classic signs of pain, heat, redness, swelling, and loss of function. Microscopically it involves a complex series of events, including dilation of arterioles, capillaries, and venules, with increased permeability and blood flow, exudation of fluids, including plasma proteins, and leukocyte migration into the area of inflammation. 
     Diseases characterized by inflammation are significant causes of morbidity and mortality in humans. Commonly, inflammation occurs as a defensive response to invasion of the host by foreign, particularly microbial, material. Responses to mechanical trauma, toxins, and neoplasia also may results in inflammatory reactions. The accumulation and subsequent activation of leukocytes are central events in the pathogenesis of most forms of inflammation. Deficiencies of inflammation compromise the host. Excessive inflammation caused by abnormal recognition of host tissue as foreign or prolongation of the inflammatory process may lead to inflammatory diseases as diverse as diabetes, atherosclerosis, cataracts, reperfusion injury, and cancer, to post-infectious syndromes such as in infectious meningitis, rheumatic fever, and to rheumatic diseases such as systemic lupus erythematosus and rheumatoid arthritis. The centrality of the inflammatory response in these varied disease processes makes its regulation a major element in the prevention control or cure of human disease. 
     Important cytokines in the inflammatory process are IL-19, U.S. Pat. No. 5,985,614 and mda7, Jiang, H., et al.  Oncogene  10: 2477-2486 (1995). Thus, there is a need to produce agents that would inhibit inflammation related to one or more of the above-mentioned inflammatory-related proteins. 
     DESCRIPTION OF THE INVENTION 
     Accordingly, the present invention fills this need by providing for a method for treating inflammation, comprising administering to a mammal in need of treatment of inflammation a soluble IL-20RA/IL-20RBreceptor that binds to IL-19 or mda7. 
     The teachings of all the references cited herein are incorporated in their entirety by reference. 
     Definitions 
     Prior to setting forth the invention in detail, it may be helpful to the understanding thereof to define the following terms. 
     The term “affinity tag” is used herein to denote a polypeptide segment that can be attached to a second polypeptide to provide for purification or detection of the second polypeptide or provide sites for attachment of the second polypeptide to a substrate. In principal, any peptide or protein for which an antibody or other specific binding agent is available can be used as an affinity tag. Affinity tags include a poly-histidine tract, protein A, Nilsson et al.,  EMBO J.  4:1075 (1985); Nilsson et al.,  Methods Enzymol.  198:3 (1991), glutathione S transferase, Smith and Johnson,  Gene  67:31 (1988), Glu-Glu affinity tag, Grussenmeyer et al.,  Proc. Natl. Acad. Sci. USA  82:7952-4 (1985), substance P, Flag™ peptide, Hopp et al.,  Biotechnology  6:1204-1210 (1988), streptavidin binding peptide, or other antigenic epitope or binding domain. See, in general, Ford et al.,  Protein Expression and Purification  2: 95-107 (1991). DNAs encoding affinity tags are available from commercial suppliers (e.g., Pharmacia Biotech, Piscataway, N.J.). 
     The term “allelic variant” is used herein to denote any of two or more alternative forms of a gene occupying the same chromosomal locus. Allelic variation arises naturally through mutation, and may result in phenotypic polymorphism within populations. Gene mutations can be silent (no change in the encoded polypeptide) or may encode polypeptides having altered amino acid sequence. The term allelic variant is also used herein to denote a protein encoded by an allelic variant of a gene. 
     The terms “amino-terminal” and “carboxyl-terminal” are used herein to denote positions within polypeptides. Where the context allows, these terms are used with reference to a particular sequence or portion of a polypeptide to denote proximity or relative position. For example, a certain sequence positioned carboxyl-terminal to a reference sequence within a polypeptide is located proximal to the carboxyl terminus of the reference sequence, but is not necessarily at the carboxyl terminus of the complete polypeptide. 
     “Angiogenic” denotes the ability of a compound to stimulate the formation of new blood vessels from existing vessels, acting alone or in concert with one or more additional compounds. Angiogenic activity is measurable as endothelial cell activation, stimulation of protease secretion by endothelial cells, endothelial cell migration, capillary sprout formation, and endothelial cell proliferation. 
     The term “complement/anti-complement pair” denotes non-identical moieties that form a non-covalently associated, stable pair under appropriate conditions. For instance, biotin and avidin (or streptavidin) are prototypical members of a complement/anti-complement pair. Other exemplary complement/anti-complement pairs include receptor/ligand pairs, antibody/antigen (or hapten or epitope) pairs, sense/antisense polynucleotide pairs, and the like. Where subsequent dissociation of the complement/anti-complement pair is desirable, the complement/anti-complement pair preferably has a binding affinity of &lt;10 9  M −1 . 
     The term “complements of a polynucleotide molecule” is a polynucleotide molecule having a complementary base sequence and reverse orientation as compared to a reference sequence. For example, the sequence 5′ ATGCACGGG 3′ is complementary to 5′ CCCGTGCAT 3′. 
     The term “contig” denotes a polynucleotide that has a contiguous stretch of identical or complementary sequence to another polynucleotide. Contiguous sequences are said to “overlap” a given stretch of polynucleotide sequence either in their entirety or along a partial stretch of the polynucleotide. For example, representative contigs to the polynucleotide sequence 5′-ATGGCTTAGCTT-3′ are 5′-TAGCTTgagtct-3′ and 3′-gtcgacTACCGA-5′. 
     The term “degenerate nucleotide sequence” denotes a sequence of nucleotides that includes one or more degenerate codons (as compared to a reference polynucleotide molecule that encodes a polypeptide). Degenerate codons contain different triplets of nucleotides, but encode the same amino acid residue (i.e., GAU and GAC triplets each encode Asp). 
     The term “expression vector” is used to denote a DNA molecule, linear or circular, that comprises a segment encoding a polypeptide of interest operably linked to additional segments that provide for its transcription. Such additional segments include promoter and terminator sequences, and may also include one or more origins of replication, one or more selectable markers, an enhancer, a polyadenylation signal, etc. Expression vectors are generally derived from plasmid or viral DNA, or may contain elements of both. 
     The term “isolated”, when applied to a polynucleotide, denotes that the polynucleotide has been removed from its natural genetic milieu and is thus free of other extraneous or unwanted coding sequences, and is in a form suitable for use within genetically engineered protein production systems. Such isolated molecules are those that are separated from their natural environment and include cDNA and genomic clones. Isolated DNA molecules of the present invention are free of other genes with which they are ordinarily associated, but may include naturally occurring 5′ and 3′ untranslated regions such as promoters and terminators. The identification of associated regions will be evident to one of ordinary skill in the art (see for example, Dynan and Tijan,  Nature  316:774-78 (1985). 
     An “isolated” polypeptide or protein is a polypeptide or protein that is found in a condition other than its native environment, such as apart from blood and animal tissue. In a preferred form, the isolated polypeptide is substantially free of other polypeptides, particularly other polypeptides of animal origin. It is preferred to provide the polypeptides in a highly purified form, i.e. greater than 95% pure, more preferably greater than 99% pure. When used in this context, the term “isolated” does not exclude the presence of the same polypeptide in alternative physical forms, such as dimers or alternatively glycosylated or derivatized forms. 
     The term “operably linked”, when referring to DNA segments, indicates that the segments are arranged so that they function in concert for their intended purposes, e.g., transcription initiates in the promoter and proceeds through the coding segment to the terminator. 
     The term “ortholog” denotes a polypeptide or protein obtained from one species that is the functional counterpart of a polypeptide or protein from a different species. Sequence differences among orthologs are the result of speciation. 
     “Paralogs” are distinct but structurally related proteins made by an organism. Paralogs are believed to arise through gene duplication. For example, a-globin, b-globin, and myoglobin are paralogs of each other. 
     A “polynucleotide” is a single- or double-stranded polymer of deoxyribonucleotide or ribonucleotide bases read from the 5′ to the 3′ end. Polynucleotides include RNA and DNA, and may be isolated from natural sources, synthesized in vitro, or prepared from a combination of natural and synthetic molecules. Sizes of polynucleotides are expressed as base pairs (abbreviated “bp”), nucleotides (“nt”), or kilobases (“kb”). Where the context allows, the latter two terms may describe polynucleotides that are single-stranded or double-stranded. When the term is applied to double-stranded molecules it is used to denote overall length and will be understood to be equivalent to the term “base pairs”. It will be recognized by those skilled in the art that the two strands of a double-stranded polynucleotide may differ slightly in length and that the ends thereof may be staggered as a result of enzymatic cleavage; thus all nucleotides within a double-stranded polynucleotide molecule may not be paired. Such unpaired ends will in general not exceed 20 nt in length. 
     A “polypeptide” is a polymer of amino acid residues joined by peptide bonds, whether produced naturally or synthetically. Polypeptides of less than about 10 amino acid residues are commonly referred to as “peptides”. 
     The term “promoter” is used herein for its art-recognized meaning to denote a portion of a gene containing DNA sequences that provide for the binding of RNA polymerase and initiation of transcription. Promoter sequences are commonly, but not always, found in the 5′ non-coding regions of genes. 
     A “protein” is a macromolecule comprising one or more polypeptide chains. A protein may also comprise non-peptidic components, such as carbohydrate groups. Carbohydrates and other non-peptidic substituents may be added to a protein by the cell in which the protein is produced, and will vary with the type of cell. Proteins are defined herein in terms of their amino acid backbone structures; substituents such as carbohydrate groups are generally not specified, but may be present nonetheless. 
     The term “receptor” denotes a cell-associated protein that binds to a bioactive molecule (i.e., a ligand) and mediates the effect of the ligand on the cell. Membrane-bound receptors are characterized by a multi-domain structure comprising an extracellular ligand-binding domain and an intracellular effector domain that is typically involved in signal transduction. Binding of ligand to receptor results in a conformational change in the receptor that causes an interaction between the effector domain and other molecule(s) in the cell. This interaction in turn leads to an alteration in the metabolism of the cell. Metabolic events that are linked to receptor-ligand interactions include gene transcription, phosphorylation, dephosphorylation, increases in cyclic AMP production, mobilization of cellular calcium, mobilization of membrane lipids, cell adhesion, hydrolysis of inositol lipids and hydrolysis of phospholipids. In general, receptors can be membrane bound, cytosolic or nuclear; monomeric (e.g., thyroid stimulating hormone receptor, beta-adrenergic receptor) or multimeric (e.g., PDGF receptor, growth hormone receptor, IL-3 receptor, GM-CSF receptor, G-CSF receptor, erythropoietin receptor and IL-6 receptor). 
     The term “secretory signal sequence” denotes a DNA sequence that encodes a polypeptide (a “secretory peptide”) that, as a component of a larger polypeptide, directs the larger polypeptide through a secretory pathway of a cell in which it is synthesized. The larger polypeptide is commonly cleaved to remove the secretory peptide during transit through the secretory pathway. 
     The term “splice variant” is used herein to denote alternative forms of RNA transcribed from a gene. Splice variation arises naturally through use of alternative splicing sites within a transcribed RNA molecule, or less commonly between separately transcribed RNA molecules, and may result in several mRNAs transcribed from the same gene. Splice variants may encode polypeptides having altered amino acid sequence. The term splice variant is also used herein to denote a protein encoded by a splice variant of an mRNA transcribed from a gene. 
     Molecular weights and lengths of polymers determined by imprecise analytical methods (e.g., gel electrophoresis) will be understood to be approximate values. When such a value is expressed as “about” X or “approximately” X, the stated value of X will be understood to be accurate to ±10%. 
     A receptor has been discovered that binds to both IL-19 and mda7 and is a heterodimer comprised of the polypeptide termed ‘interleukin-20 receptor alpha IL-20RA’ and a polypeptide termed interleukin-20 receptor beta ‘IL-20RB’. The IL-20RA polypeptide, nucleic acid that encodes it, antibodies to IL-20RA and methods for producing it are disclosed in U.S. Pat. No. 5,945,511 issued Aug. 31, 1999. SEQ ID NOs: 1-3 are the polynucleotides and polypeptides of IL-20RA. The mature extracellular sequence of IL-20RA is comprised of SEQ ID NO: 3. The IL-20RB polypeptide, nucleic acid that encodes it, antibodies to IL-20RB and methods for producing it are disclosed in International Patent Application No. PCT/US99/03735 (publication no. WO 99/46379) filed on Mar. 8, 1999. A variant of IL-20RB (hereinafter referred to as V-IL-20RB has been cloned and is defined by SEQ ID NOs: 4-6, SEQ ID NO: 6 being the extracellular domain. 
     Preparation of a Soluble IL-20 Heterodimeric Receptor ‘IL-20RA/IL-20RB’ 
     The soluble heterodimeric receptor is comprised of SEQ ID NO: 3 (hereinafter referred to as IL-20RA) and the extracellular domain of IL-20RB or the extracellular domain of a variant of IL-20RB (vIL-20RB, SEQ ID NOs: 4-6) SEQ ID NO: 6. Preferably, the extracellular domain of the IL-20RA polypeptide and the extracellular domain of the IL-20RB polypeptide are covalently bonded together. In a preferred embodiment the one polypeptide has constant region of a heavy chain of an immunoglobulin fused to its carboxy terminus and the other polypeptide has a constant light chain of an immunoglobulin (Ig) fused to its carboxy terminus such that the two polypeptides come together and a disulfide bond is formed between the heavy and the light chains to form a heterodimer. In another method, a peptide linker could be fused to the two carboxy termini of the polypeptides to form a covalently bonded heterodimer. 
     A method is also provided for producing soluble dimerized extracellular domains of IL-20RA and IL-20RB comprising (a) introducing into a host cell a first DNA sequence comprised of a transcriptional promoter operatively linked to a first secretory signal sequence followed downstream by and in proper reading frame the DNA that encodes the extracellular portion of IL-20RA and the DNA that encodes an immunoglobulin light chain constant region; (b) introducing into the host cell a second DNA construct comprised of a transcriptional promoter operatively linked to a second secretory signal followed downstream by and in proper reading frame a DNA sequence that encodes the extracellular portion of IL-20RB and a DNA sequence that encodes an immunoglobulin heavy chain constant region domain selected from the group consisting of C H 1, C H 2, C H 3 and C H 4; (c) growing the host cell in an appropriate growth medium under physiological conditions to allow the secretion of a dimerized heterodimeric fusion protein comprised of the extracellular domain of IL-20RA? and IL-20RB; and (d) isolating the dimerized polypeptide from the host cell. In one embodiment, the second DNA sequence further encodes an immunoglobulin heavy chain hinge region wherein the hinge region is joined to the heavy chain constant region domain. In another embodiment, the second DNA sequence further encodes an immunoglobulin variable region joined upstream of and in proper reading frame with the immunoglobulin heavy chain constant region. 
     In an alternative embodiment a method is provided for producing soluble dimerized extracellular domains of IL-20RA and IL-20RB comprising (a) introducing into a host cell a first DNA sequence comprised of a transcriptional promoter operatively linked to a first secretory signal sequence followed downstream by and in proper reading frame the DNA that encodes the extracellular portion of IL-20RB and the DNA that encodes an immunoglobulin light chain constant region; (b) introducing into the host cell a second DNA construct comprised of a transcriptional promoter operatively linked to a second secretory signal followed downstream by and in proper reading frame a DNA sequence that encodes the extracellular portion of IL-20RA and a DNA sequence that encodes an immunoglobulin heavy chain constant region domain selected from the group consisting of C H 1, C H 2, C H 3 and C H 4; (c) growing the host cell in an appropriate growth medium under physiological conditions to allow the secretion of a dimerized heterodimeric fusion protein comprised of the extracellular domain of IL-20RA and IL-20RB; and (d) isolating the dimerized polypeptide from the host cell. In one embodiment, the second DNA sequence further encodes an immunoglobulin heavy chain hinge region wherein the hinge region is joined to the heavy chain constant region domain. In another embodiment, the second DNA sequence further encodes an immunoglobulin variable region joined upstream of and in proper reading frame with the immunoglobulin heavy chain constant region. (See U.S. Pat. No. 5,843,725.) 
     Polynucleotides 
     Generally, a cDNA sequence encodes the described polypeptides herein. A cDNA sequence that encodes a polypeptide of the present invention is comprised of a series of codons, each amino acid residue of the polypeptide being encoded by a codon and each codon being comprised of three nucleotides. The amino acid residues are encoded by their respective codons as follows.
         Alanine (Ala) is encoded by GCA, GCC, GCG or GCT;   Cysteine (Cys) is encoded by TGC or TGT;   Aspartic acid (Asp) is encoded by GAC or GAT;   Glutamic acid (Glu) is encoded by GAA or GAG;   Phenylalanine (Phe) is encoded by TTC or TTT;   Glycine (Gly) is encoded by GGA, GGC, GGG or GGT;   Histidine (His) is encoded by CAC or CAT;   Isoleucine (Ile) is encoded by ATA, ATC or ATT;   Lysine (Lys) is encoded by AAA, or AAG;   Leucine (Leu) is encoded by TTA, TTG, CTA, CTC, CTG or CTT;   Methionine (Met) is encoded by ATG;   Asparagine (Asn) is encoded by AAC or AAT;   Proline (Pro) is encoded by CCA, CCC, CCG or CCT;   Glutamine (Gln) is encoded by CAA or CAG;   Arginine (Arg) is encoded by AGA, AGG, CGA, CGC, CGG or CGT;   Serine (Ser) is encoded by AGC, AGT, TCA, TCC, TCG or TCT;   Threonine (Thr) is encoded by ACA, ACC, ACG or ACT;   Valine (Val) is encoded by GTA, GTC, GTG or GTT;   Tryptophan (Trp) is encoded by TGG; and   Tyrosine (Tyr) is encoded by TAC or TAT.       

     Methods for synthesizing amino acids and aminoacylating tRNA are known in the art. Transcription and translation of plasmids containing nonsense mutations is carried out in a cell-free system comprising an  E. coli  S30 extract and commercially available enzymes and other reagents. Proteins are purified by chromatography. See, for example, Robertson et al.,  J. Am. Chem. Soc.  113:2722 (1991); Ellman et al.,  Methods Enzymol.  202:301 (1991; Chung et al.,  Science  259:806-809 (1993); and Chung et al.,  Proc. Natl. Acad. Sci. USA  90:10145-1019 (1993). In a second method, translation is carried out in  Xenopus  oocytes by microinjection of mutated mRNA and chemically aminoacylated suppressor tRNAs, Turcatti et al.,  J. Biol. Chem.  271:19991-19998 (1996). Within a third method,  E. coli  cells are cultured in the absence of a natural amino acid that is to be replaced (e.g., phenylalanine) and in the presence of the desired non-naturally occurring amino acid(s) (e.g., 2-azaphenylalanine, 3-azaphenylalanine, 4-azaphenylalanine, or 4-fluorophenylalanine). The non-naturally occurring amino acid is incorporated into the protein in place of its natural counterpart. See, Koide et al.,  Biochem.  33:7470-7476 (1994). Naturally occurring amino acid residues can be converted to non-naturally occurring species by in vitro chemical modification. Chemical modification can be combined with site-directed mutagenesis to further expand the range of substitutions, Wynn and Richards,  Protein Sci.  2:395-403 (1993). 
     A limited number of non-conservative amino acids, amino acids that are not encoded by the genetic code, non-naturally occurring amino acids, and unnatural amino acids may be substituted for amino acid residues. 
     Essential amino acids in the polypeptides of the present invention can be identified according to procedures known in the art, such as site-directed mutagenesis or alanine-scanning mutagenesis, Cunningham and Wells,  Science  244: 1081-1085 (1989); Bass et al.,  Proc. Natl. Acad. Sci. USA  88:4498-502 (1991). In the latter technique, single alanine mutations are introduced at every residue in the molecule, and the resultant mutant molecules are tested for biological activity as disclosed below to identify amino acid residues that are critical to the activity of the molecule. See also, Hilton et al.,  J. Biol. Chem.  271:4699-708, 1996. Sites of ligand-receptor interaction can also be determined by physical analysis of structure, as determined by such techniques as nuclear magnetic resonance, crystallography, electron diffraction or photoaffinity labeling, in conjunction with mutation of putative contact site amino acids. See, for example, de Vos et al.,  Science  255:306-312 (1992); Smith et al.,  J. Mol. Biol.  224:899-904 (1992); Wlodaver et al.,  FEBS Lett.  309:59-64 (1992). 
     Multiple amino acid substitutions can be made and tested using known methods of mutagenesis and screening, such as those disclosed by Reidhaar-Olson and Sauer,  Science  241:53-57 (1988) or Bowie and Sauer,  Proc. Natl. Acad. Sci. USA  86:2152-2156 (1989). Briefly, these authors disclose methods for simultaneously randomizing two or more positions in a polypeptide, selecting for functional polypeptide, and then sequencing the mutagenized polypeptides to determine the spectrum of allowable substitutions at each position. Other methods that can be used include phage display, e.g., Lowman et al.,  Biochem.  30:10832-10837 (1991); Ladner et al., U.S. Pat. No. 5,223,409; Huse, WIPO Publication WO 92/06204) and region-directed mutagenesis, Derbyshire et al.,  Gene  46:145 (1986); Ner et al.,  DNA  7:127 (1988). 
     Variants of the disclosed IL-20RA and IL-20RB DNA and polypeptide sequences can be generated through DNA shuffling as disclosed by Stemmer,  Nature  370:389-391, (1994), Stemmer,  Proc. Natl. Acad. Sci. USA  91:10747-10751 (1994) and WIPO Publication WO 97/20078. Briefly, variant DNAs are generated by in vitro homologous recombination by random fragmentation of a parent DNA followed by reassembly using PCR, resulting in randomly introduced point mutations. This technique can be modified by using a family of parent DNAs, such as allelic variants or DNAs from different species, to introduce additional variability into the process. Selection or screening for the desired activity, followed by additional iterations of mutagenesis and assay provides for rapid “evolution” of sequences by selecting for desirable mutations while simultaneously selecting against detrimental changes. 
     Mutagenesis methods as disclosed herein can be combined with high-throughput, automated screening methods to detect activity of cloned, mutagenized polypeptides in host cells. Mutagenized DNA molecules that encode active polypeptides can be recovered from the host cells and rapidly sequenced using modern equipment. These methods allow the rapid determination of the importance of individual amino acid residues in a polypeptide of interest, and can be applied to polypeptides of unknown structure. 
     Protein Production 
     Polypeptides can be produced in genetically engineered host cells according to conventional techniques. Suitable host cells are those cell types that can be transformed or transfected with exogenous DNA and grown in culture, and include bacteria, fungal cells, and cultured higher eukaryotic cells. Eukaryotic cells, particularly cultured cells of multicellular organisms, are preferred. Techniques for manipulating cloned DNA molecules and introducing exogenous DNA into a variety of host cells are disclosed by Sambrook et al., Molecular Cloning:  A Laboratory Manual,  2nd ed., (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989), and Ausubel et al., eds.,  Current Protocols in Molecular Biology  (John Wiley and Sons, Inc., NY, 1987). 
     In general, a DNA sequence encoding a polypeptide is operably linked to other genetic elements required for its expression, generally including a transcription promoter and terminator, within an expression vector. The vector will also commonly contain one or more selectable markers and one or more origins of replication, although those skilled in the art will recognize that within certain systems selectable markers may be provided on separate vectors, and replication of the exogenous DNA may be provided by integration into the host cell genome. Selection of promoters, terminators, selectable markers, vectors and other elements is a matter of routine design within the level of ordinary skill in the art. Many such elements are described in the literature and are available through commercial suppliers. 
     To direct a polypeptide into the secretory pathway of a host cell, a secretory signal sequence (also known as a leader sequence, prepro sequence or pre sequence) is provided in the expression vector. The secretory signal sequence may be that of the native polypeptides, or may be derived from another secreted protein (e.g., t-PA) or synthesized de novo. The secretory signal sequence is operably linked to the DNA sequence, i.e., the two sequences are joined in the correct reading frame and positioned to direct the newly synthesized polypeptide into the secretory pathway of the host cell. Secretory signal sequences are commonly positioned 5′ to the DNA sequence encoding the polypeptide of interest, although certain secretory signal sequences may be positioned elsewhere in the DNA sequence of interest (see, e.g., Welch et al., U.S. Pat. No. 5,037,743; Holland et al., U.S. Pat. No. 5,143,830). 
     Alternatively, the secretory signal sequence contained in the polypeptides of the present invention is used to direct other polypeptides into the secretory pathway. The present invention provides for such fusion polypeptides. The secretory signal sequence contained in the fusion polypeptides of the present invention is preferably fused amino-terminally to an additional peptide to direct the additional peptide into the secretory pathway. Such constructs have numerous applications known in the art. For example, these novel secretory signal sequence fusion constructs can direct the secretion of an active component of a normally non-secreted protein, such as a receptor. Such fusions may be used in vivo or in vitro to direct peptides through the secretory pathway. 
     Cultured mammalian cells are suitable hosts within the present invention. Methods for introducing exogenous DNA into mammalian host cells include calcium phosphate-mediated transfection, Wigler et al.,  Cell  14:725 (1978); Corsaro and Pearson,  Somatic Cell Genetics  7:603 (1981); Graham and Van der Eb,  Virology  52:456 (1973), electroporation, Neumann et al.,  EMBO J.  1:841-845 (1982), DEAE-dextran mediated transfection (Ausubel et al., ibid., and liposome-mediated transfection, Hawley-Nelson et al.,  Focus  15:73 (1993); Ciccarone et al.,  Focus  15:80 (1993), and viral vectors, Miller and Rosman,  BioTechniques  7:980(1989); Wang and Finer,  Nature Med.  2:714 (1996). The production of recombinant polypeptides in cultured mammalian cells is disclosed, for example, by Levinson et al., U.S. Pat. No. 4,713,339; Hagen et al., U.S. Pat. No. 4,784,950; Palmiter et al., U.S. Pat. No. 4,579,821; and Ringold, U.S. Pat. No. 4,656,134. Suitable cultured mammalian cells include the COS-1 (ATCC No. CRL 1650), COS-7 (ATCC No. CRL 1651), BHK (ATCC No. CRL 1632), BHK 570 (ATCC No. CRL 10314), 293 (ATCC No. CRL 1573; Graham et al.,  J. Gen. Virol.  36:59 (1977) and Chinese hamster ovary (e.g. CHO-K1; ATCC No. CCL 61) cell lines. Additional suitable cell lines are known in the art and available from public depositories such as the American Type Culture Collection, Rockville, Md. In general, strong transcription promoters are preferred, such as promoters from SV-40 or cytomegalovirus. See, e.g., U.S. Pat. No. 4,956,288. Other suitable promoters include those from metallothionein genes (U.S. Pat. Nos. 4,579,821 and 4,601,978) and the adenovirus major late promoter. 
     Drug selection is generally used to select for cultured mammalian cells into which foreign DNA has been inserted. Such cells are commonly referred to as “transfectants”. Cells that have been cultured in the presence of the selective agent and are able to pass the gene of interest to their progeny are referred to as “stable transfectants.” A preferred selectable marker is a gene encoding resistance to the antibiotic neomycin. Selection is carried out in the presence of a neomycin-type drug, such as G-418 or the like. Selection systems can also be used to increase the expression level of the gene of interest, a process referred to as “amplification.” Amplification is carried out by culturing transfectants in the presence of a low level of the selective agent and then increasing the amount of selective agent to select for cells that produce high levels of the products of the introduced genes. A preferred amplifiable selectable marker is dihydrofolate reductase, which confers resistance to methotrexate. Other drug resistance genes (e.g. hygromycin resistance, multi-drug resistance, puromycin acetyltransferase) can also be used. Alternative markers that introduce an altered phenotype, such as green fluorescent protein, or cell surface proteins such as CD4, CD8, Class I MHC, placental alkaline phosphatase may be used to sort transfected cells from untransfected cells by such means as FACS sorting or magnetic bead separation technology. 
     Other higher eukaryotic cells can also be used as hosts, including plant cells, insect cells and avian cells. The use of  Agrobacterium rhizogenes  as a vector for expressing genes in plant cells has been reviewed by Sinkar et al.,  J. Biosci.  (Bangalore) 11:47 (1987). Transformation of insect cells and production of foreign polypeptides therein is disclosed by Guarino et al., U.S. Pat. No. 5,162,222 and WIPO publication WO 94/06463. Insect cells can be infected with recombinant baculovirus, commonly derived from  Autographa californica  nuclear polyhedrosis virus (AcNPV). DNA encoding a polypeptide is inserted into the baculoviral genome in place of the AcNPV polyhedrin gene coding sequence by one of two methods. The first is the traditional method of homologous DNA recombination between wild-type AcNPV and a transfer vector containing the gene flanked by AcNPV sequences. Suitable insect cells, e.g. SF9 cells, are infected with wild-type AcNPV and transfected with a transfer vector comprising a polynucleotide operably linked to an AcNPV polyhedrin gene promoter, terminator, and flanking sequences. See, King, L. A. and Possee, R. D.,  The Baculovirus Expression System: A Laboratory Guide , (Chapman &amp; Hall, London); O&#39;Reilly, D. R. et al.,  Baculovirus Expression Vectors: A Laboratory Manual  (Oxford University Press, New York, N.Y., 1994); and, Richardson, C. D., Ed.,  Baculovirus Expression Protocols. Methods in Molecular Biology , (Humana Press, Totowa, N.J. 1995). Natural recombination within an insect cell will result in a recombinant baculovirus that contains coding sequences driven by the polyhedrin promoter. Recombinant viral stocks are made by methods commonly used in the art. 
     The second method of making recombinant baculovirus utilizes a transposon-based system described by Luckow, V. A, et al.,  J Virol  67:4566 (1993). This system is sold in the Bac-to-Bac kit (Life Technologies, Rockville, Md.). This system utilizes a transfer vector, pFastBac1™ (Life Technologies) containing a Tn7 transposon to move the DNA encoding the polypeptide into a baculovirus genome maintained in  E. coli  as a large plasmid called a “bacmid.” The pFastBac1™ transfer vector utilizes the AcNPV polyhedrin promoter to drive the expression of the gene of interest. However, pFastBac1™ can be modified to a considerable degree. The polyhedrin promoter can be removed and substituted with the baculovirus basic protein promoter (also known as Pcor, p6.9 or MP promoter), is expressed earlier in the baculovirus infection, and has been shown to be advantageous for expressing secreted proteins. See, Hill-Perkins, M. S. and Possee, R. D.,  J Gen Virol  71:971 (1990); Bonning, B. C. et al.,  J Gen Virol  75:1551 (1994); and, Chazenbalk, G. D., and Rapoport, B.,  J Biol Chem  270:1543 (1995). In such transfer vector constructs, a short or long version of the basic protein promoter can be used. Moreover, transfer vectors can be constructed that replace the native secretory signal sequences with secretory signal sequences derived from insect proteins. For example, a secretory signal sequence from Ecdysteroid Glucosyltransferase (EGT), honey bee Melittin (Invitrogen, Carlsbad, Calif.), or baculovirus gp67 (PharMingen, San Diego, Calif.) can be used in constructs to replace the native secretory signal sequence. In addition, transfer vectors can include an in-frame fusion with DNA encoding an epitope tag at the C- or N-terminus of the expressed polypeptide, for example, a Glu-Glu epitope tag, Grussenmeyer, T. et al.,  Proc Natl Acad Sci.  82:7952 (1985). Using a technique known in the art, a transfer vector containing a recombinant gene is transformed into  E. coli , and screened for bacmids that contain an interrupted lacZ gene indicative of recombinant baculovirus. The bacmid DNA containing the recombinant baculovirus genome is isolated, using common techniques, and used to transfect  Spodoptera frugiperda  cells, e.g. Sf9 cells. Recombinant virus that expresses the polypeptide is subsequently produced. Recombinant viral stocks are made by methods commonly used the art. 
     The recombinant virus is used to infect host cells, typically a cell line derived from the fall army worm,  Spodoptera frugiperda . See, in general, Glick and Pasternak,  Molecular Biotechnology: Principles and Applications of Recombinant DNA  (ASM Press, Washington, D.C., 1994). Another suitable cell line is the High FiveO™ cell line (Invitrogen) derived from  Trichoplusia ni  (U.S. Pat. No. 5,300,435). Commercially available serum-free media are used to grow and maintain the cells. Suitable media are Sf900 II™ (Life Technologies) or ESF 921™ (Expression Systems) for the Sf9 cells; and Ex-cellO405™ (JRH Biosciences, Lenexa, Kans.) or Express FiveO™ (Life Technologies) for the  T. ni  cells. The cells are grown up from an inoculation density of approximately 2-5×10 5  cells to a density of 1-2×10 6  cells at which time a recombinant viral stock is added at a multiplicity of infection (MOI) of 0.1 to 10, more typically near 3. The recombinant virus-infected cells typically produce the recombinant polypeptide at 12-72 hours post-infection and secrete it with varying efficiency into the medium. The culture is usually harvested 48 hours post-infection. Centrifugation is used to separate the cells from the medium (supernatant). The supernatant containing the polypeptide is filtered through micropore filters, usually 0.45 μm pore size. Procedures used are generally described in available laboratory manuals (King, L. A. and Possee, R. D., ibid.; O&#39;Reilly, D. R. et al., ibid.; Richardson, C. D., ibid.). Subsequent purification of the polypeptide from the supernatant can be achieved using methods described herein. 
     Fungal cells, including yeast cells, can also be used within the present invention. Yeast species of particular interest in this regard include  Saccharomyces cerevisiae, Pichia pastoris , and  Pichia methanolica . Methods for transforming  S. cerevisiae  cells with exogenous DNA and producing recombinant polypeptides therefrom are disclosed by, for example, Kawasaki, U.S. Pat. No. 4,599,311; Kawasaki et al., U.S. Pat. No. 4,931,373; Brake, U.S. Pat. No. 4,870,008; Welch et al., U.S. Pat. No. 5,037,743; and Murray et al., U.S. Pat. No. 4,845,075. Transformed cells are selected by phenotype determined by the selectable marker, commonly drug resistance or the ability to grow in the absence of a particular nutrient (e.g., leucine). A preferred vector system for use in  Saccharomyces cerevisiae  is the POT1 vector system disclosed by Kawasaki et al. (U.S. Pat. No. 4,931,373), which allows transformed cells to be selected by growth in glucose-containing media. Suitable promoters and terminators for use in yeast include those from glycolytic enzyme genes (see, e.g., Kawasaki, U.S. Pat. No. 4,599,311; Kingsman et al., U.S. Pat. No. 4,615,974; and Bitter, U.S. Pat. No. 4,977,092) and alcohol dehydrogenase genes. See also U.S. Pat. Nos. 4,990,446; 5,063,154; 5,139,936 and 4,661,454. Transformation systems for other yeasts, including  Hansenula polymorpha, Schizosaccharomyces pombe, Kluyveromyces lactis, Kluyveromyces fragilis, Ustilago maydis, Pichia pastoris, Pichia methanolica, Pichia guillermondii  and  Candida maltosa  are known in the art. See, for example, Gleeson et al.,  J. Gen. Microbiol.  132:3459 (1986) and Cregg, U.S. Pat. No. 4,882,279.  Aspergillus  cells may be utilized according to the methods of McKnight et al., U.S. Pat. No. 4,935,349. Methods for transforming  Acremonium chrysogenum  are disclosed by Sumino et al., U.S. Pat. No. 5,162,228. Methods for transforming  Neurospora  are disclosed by Lambowitz, U.S. Pat. No. 4,486,533. 
     The use of  Pichia methanolica  as host for the production of recombinant proteins is disclosed in WIPO Publications WO 97/17450, WO 97/17451, WO 98/02536, and WO 98/02565. DNA molecules for use in transforming  P. methanolica  will commonly be prepared as double-stranded, circular plasmids, which are preferably linearized prior to transformation. For polypeptide production in  P. methanolica , it is preferred that the promoter and terminator in the plasmid be that of a  P. methanolica  gene, such as a  P. methanolica  alcohol utilization gene (AUG1 or AUG2). Other useful promoters include those of the dihydroxyacetone synthase (DHAS), formate dehydrogenase (FMD), and catalase (CAT) genes. To facilitate integration of the DNA into the host chromosome, it is preferred to have the entire expression segment of the plasmid flanked at both ends by host DNA sequences. A preferred selectable marker for use in  Pichia methanolica  is a  P. methanolica  ADE2 gene, which encodes phosphoribosyl-5-aminoimidazole carboxylase (AIRC; EC 4.1.1.21), which allows ade2 host cells to grow in the absence of adenine. For large-scale, industrial processes where it is desirable to minimize the use of methanol, it is preferred to use host cells in which both methanol utilization genes (AUG1 and AUG2) are deleted. For production of secreted proteins, host cells deficient in vacuolar protease genes (PEP4 and PRB1) are preferred. Electroporation is used to facilitate the introduction of a plasmid containing DNA encoding a polypeptide of interest into  P. methanolica  cells. It is preferred to transform  P. methanolica  cells by electroporation using an exponentially decaying, pulsed electric field having a field strength of from 2.5 to 4.5 kV/cm, preferably about 3.75 kV/cm, and a time constant (t) of from 1 to 40 milliseconds, most preferably about 20 milliseconds. 
     Prokaryotic host cells, including strains of the bacteria  Escherichia coli, Bacillus  and other genera are also useful host cells within the present invention. Techniques for transforming these hosts and expressing foreign DNA sequences cloned therein are well known in the art, see, e.g., Sambrook et al., ibid.). When expressing a polypeptide in bacteria such as  E. coli , the polypeptide may be retained in the cytoplasm, typically as insoluble granules, or may be directed to the periplasmic space by a bacterial secretion sequence. In the former case, the cells are lysed, and the granules are recovered and denatured using, for example, guanidine isothiocyanate or urea. The denatured polypeptide can then be refolded and dimerized by diluting the denaturant, such as by dialysis against a solution of urea and a combination of reduced and oxidized glutathione, followed by dialysis against a buffered saline solution. In the latter case, the polypeptide can be recovered from the periplasmic space in a soluble and functional form by disrupting the cells (by, for example, sonication or osmotic shock) to release the contents of the periplasmic space and recovering the protein, thereby obviating the need for denaturation and refolding. 
     Transformed or transfected host cells are cultured according to conventional procedures in a culture medium containing nutrients and other components required for the growth of the chosen host cells. A variety of suitable media, including defined media and complex media, are known in the art and generally include a carbon source, a nitrogen source, essential amino acids, vitamins and minerals. Media may also contain such components as growth factors or serum, as required. The growth medium will generally select for cells containing the exogenously added DNA by, for example, drug selection or deficiency in an essential nutrient, which is complemented by the selectable marker carried on the expression vector or co-transfected into the host cell.  P. methanolica  cells are cultured in a medium comprising adequate sources of carbon, nitrogen and trace nutrients at a temperature of about 25° C. to 35° C. Liquid cultures are provided with sufficient aeration by conventional means, such as shaking of small flasks or sparging of fermentors. A preferred culture medium for  P. methanolica  is YEPD (2% D-glucose, 2% Bacto™ Peptone (Difco Laboratories, Detroit, Mich.), 1% Bacto™ yeast extract (Difco Laboratories), 0.004% adenine and 0.006% L-leucine). 
     Protein Isolation 
     It is preferred to purify the polypeptides of the present invention to ≧80% purity, more preferably to ≧90% purity, even more preferably ≧95% purity, and particularly preferred is a pharmaceutically pure state, that is greater than 99.9% pure with respect to contaminating macromolecules, particularly other proteins and nucleic acids, and free of infectious and pyrogenic agents. Preferably, a purified polypeptide is substantially free of other polypeptides, particularly other polypeptides of animal origin. 
     Expressed recombinant polypeptides (or chimeric polypeptides) can be purified using fractionation and/or conventional purification methods and media. Ammonium sulfate precipitation and acid or chaotrope extraction may be used for fractionation of samples. Exemplary purification steps may include hydroxyapatite, size exclusion, FPLC and reverse-phase high performance liquid chromatography. Suitable chromatographic media include derivatized dextrans, agarose, cellulose, polyacrylamide, specialty silicas, and the like. PEI, DEAE, QAE and Q derivatives are preferred. Exemplary chromatographic media include those media derivatized with phenyl, butyl, or octyl groups, such as Phenyl-Sepharose FF (Pharmacia), Toyopearl butyl 650 (Toso Haas, Montgomeryville, Pa.), Octyl-Sepharose (Pharmacia) and the like; or polyacrylic resins, such as Amberchrom CG 71 (Toso Haas) and the like. Suitable solid supports include glass beads, silica-based resins, cellulosic resins, agarose beads, cross-linked agarose beads, polystyrene beads, cross-linked polyacrylamide resins and the like that are insoluble under the conditions in which they are to be used. These supports may be modified with reactive groups that allow attachment of proteins by amino groups, carboxyl groups, sulfhydryl groups, hydroxyl groups and/or carbohydrate moieties. Examples of coupling chemistries include cyanogen bromide activation, N-hydroxysuccinimide activation, epoxide activation, sulfhydryl activation, hydrazide activation, and carboxyl and amino derivatives for carbodiimide coupling chemistries. These and other solid media are well known and widely used in the art, and are available from commercial suppliers. Methods for binding receptor polypeptides to support media are well known in the art. Selection of a particular method is a matter of routine design and is determined in part by the properties of the chosen support. See, for example,  Affinity Chromatography: Principles &amp; Methods  (Pharmacia LKB Biotechnology, Uppsala, Sweden, 1988). 
     Polypeptides can be isolated by exploitation of their properties. Proteins that are fused to the Fc constant region of an antibody can be isolated by means of a ‘Protein A’ column,  Methods in Enzymol. , Vol. 182, “Guide to Protein Purification”, M. Deutscher, (ed.), page 529-539 (Acad. Press, San Diego, 1990). Within additional embodiments of the invention, a fusion of the polypeptide of interest and an affinity tag (e.g., maltose-binding protein, an immunoglobulin domain) may be constructed to facilitate purification. 
     Moreover, using methods described in the art, polypeptide fusions, or hybrid proteins, are constructed using regions or domains of polypeptides, Sambrook et al., ibid., Altschul et al., ibid., Picard,  Cur. Opin. Biology,  5:511 (1994). These methods allow the determination of the biological importance of larger domains or regions in a polypeptide of interest. Such hybrids may alter reaction kinetics, binding, constrict or expand the substrate specificity, or alter tissue and cellular localization of a polypeptide, and can be applied to polypeptides of unknown structure. 
     Fusion proteins can be prepared by methods known to those skilled in the art by preparing each component of the fusion protein and chemically conjugating them. Alternatively, a polynucleotide encoding both components of the fusion protein in the proper reading frame can be generated using known techniques and expressed by the methods described herein. For example, part or all of a domain(s) conferring a biological function may be swapped between a polypeptide of the present invention with the functionally equivalent domain(s) from another family member. Such domains include, but are not limited to, the secretory signal sequence, conserved, and significant domains or regions in this family. Such fusion proteins would be expected to have a biological functional profile that is the same or similar to polypeptides of the present invention or other known family proteins, depending on the fusion constructed. Moreover, such fusion proteins may exhibit other properties as disclosed herein. 
     The quantity of the IL-20RA/IL-20RB soluble receptor necessary to inhibit IL-19 or mda7 will depend upon many different factors, including means of administration, target site, physiological state of the patient, and other medications administered. Thus, treatment dosages should be titrated to optimize safety and efficacy. Typically, dosages used in vitro may provide useful guidance in the amounts useful for in vivo administration of these reagents. Animal testing of effective doses for treatment of particular disorders will provide further predictive indication of human dosage. Methods for administration include oral, intravenous, peritoneal, intramuscular, transdermal or administration into the lung or trachea in spray form by means or a nebulizer or atomizer. Pharmaceutically acceptable carriers will include water, saline, buffers to name just a few. Dosage ranges would ordinarily be expected from 1 μg to 1000 μg per kilogram of body weight per day. However, the doses may be higher or lower as can be determined by a medical doctor with ordinary skill in the art. For a complete discussion of drug formulations and dosage ranges see  Remington&#39;s Pharmaceutical Sciences,  18 th  Ed., (Mack Publishing Co., Easton, Pa., 1996), and  Goodman and Gilman&#39;s: The Pharmacological Bases of Therapeutics,  9 th  Ed. (Pergamon Press 1996). 
     The invention is further illustrated by the following non-limiting examples. 
    
    
     EXAMPLE 1   
     Cloning of IL-20RB Variant 
     1. IL-20RB 
     Two novel members of the class II cytokine receptor family were described in International Patent Application No. PCT/US99/03735 filed Mar. 8, 1999. IL-20RB shares 31% sequence homology with class II cytokine receptor IL-20RA, U.S. Pat. No. 5,945,511 issued Aug. 31, 1999. IL-20 is a homologue of IL-10, which is a member of class II cytokine family. The fact that IL-20RB is a class II cytokine receptor and is expressed in fetal liver, fetal small intestine, fetal ovary, normal skin and psoriasis skin made IL-20RB a plausible candidate for an IL-20 receptor subunit. 
     2. Cloning of IL-20RB Coding Region 
     Two PCR primers were designed based on the sequence from International Patent Application No. PCT/US99/03735 (publication no. WO 99/46379) filed on Mar. 8, 1999: ZC25480 (SEQ ID NO: 7) contains the ATG (Met1) codon with an EcoRI restriction site, ZC25481 (SEQ ID NO: 8) contains the stop codon (TAG) with a XhoI restriction site. The PCR amplification was carried out using a human keratinocyte (HaCaT) cDNA library DNA as a template and ZC25480 (SEQ ID NO: 7) and ZC25481 (SEQ ID NO: 8) as primers. The PCR reaction was performed as follows: incubation at 94° C. for 1 min followed by 30 cycles of 94° C. for 30 sec and 68° C. for 2 min, after additional 68° C. for 4 min, the reaction was stored at 4° C. The PCR products were run on 1% Agarose gel, and a 1 kb DNA band was observed. The PCR products were cut from the gel and the DNA was purified using a QIAquick Gel Extraction Kit (Qiagen). The purified DNA was digested with EcoRI and XhoI, and cloned into a pZP vector that was called pZP7N. A pZP plasmid is a mammalian expression vector containing an expression cassette having the mouse metallothionein-1 promoter, human tPA leader peptide, multiple restriction sites for insertion of coding sequences, a Glu-Glu tag, and a human growth hormone terminator. The plasmid also has an  E. coli  origin of replication, a mammalian selectable marker expression unit having an SV40 promoter, an enhancer and an origin of replication, as well as a DHFR gene, and the SV40 terminator. Several IL-20R?-pZP7N clones were sequenced. They all contain three non-conservative mutations compared with the patent sequence of IL-20RB? in PCT/US99/03735: (sequence IL-20R?-pZP7N), 146 Pro (CCC)—Thr (ACC), 148 His (CAT)—Asp (GAT), and 171 Thr (ACG)—Arg (AGG). 
     To verify the three substitutions in IL-20R?-pZP7N clone, PCR amplification was carried out using three difference cDNA sources—fetal skin marathon cDNA, HaCaT cDNA library DNA, and prostate smooth muscle cDNA library DNA—as templates. The PCR products were gel purified and sequenced. The sequence of each of the three PCR products was consistent with that of the IL-20R?-pZP7N clone. 
     EXAMPLE 2   
     IL-20RA Receptor-Ig Fusion Protein 
     The expression vector pEZE3 was used to express the recombinant IL-20 receptor-Ig fusion protein. pEZE3 is derived from pDC312. pDC312 was obtained through license from Immunex Corporation. pDC312 and pEZE3 contain an EASE segment as described in WO 97/25420. The presence of the EASE segment in an expression vector can improve expression of recombinant proteins two to eight fold in stable cell pools. 
     pEZE3 is a tricistronic expression vector that may be used to express up to three different proteins in mammalian cells, preferably Chinese Hamster Ovary (CHO) cells. The pEZE3 expression unit contains the CMV enhancer/promoter, the adenovirus tripartite leader sequence, a multiple cloning site for insertion of the coding region for the first recombinant protein, the polioviruse type 2 internal ribosome entry site, a second multiple cloning site for insertion of the coding region for the second recombinant protein, an encephalomyocarditis virus internal ribosome entry site, a coding segment for mouse dihydrofolate reductase, and the SV40 transcription terminator. In addition, pEZE3 contains an  E. coli  origin of replication and the bacterial beta lactamase gene. 
     The IL-20 receptor-Ig fusion protein is a disulfide linked heterotetramer consisting of two chains of the extracellular domain of the human fused to the wild type human immunoglobulin kappa light chain constant region and two chains of the human IL-20R protein extracellular domain fused to a mutated human immunoglobulin gamma 1 constant region. The human immunoglobulin gamma 1 constant region contains amino acid substitutions to reduce FcRI binding and C1q complement fixation. 
     The human IL-20RB extracellular domain human immunoglobulin kappa light chain constant region fusion construct was generated by overlap PCR. The IL-20RB coding segment consists of amino acids 1 to 230. The template used for the PCR amplification of the IL-20R segment was a previously generated IL-20RB human kappa light chain constant region expression construct. Oligonucleotide primers SEQ ID NO: 9 (zc27,522) and SEQ ID NO: 10 (zc27,684) were used to amplify the IL-20RB segment. The entire wild type human immunoglobulin kappa light chain constant region was used. The template used for the PCR amplification of the wild type human immunoglobulin kappa light chain constant region segment was a previously generated IL-20RB human kappa light chain constant region expression construct. Oligonucleotide primers SEQ ID NO: 11 (zc27,675) and SEQ ID NO: 12 (zc27,685) were used to amplify the wild type human immunoglobulin kappa light chain constant region. The two protein coding domains were linked by overlap PCR using oligonucleotides SEQ ID NO: 9 (zc27,522) and SEQ ID NO: 12 (zc27,685). A (Gly 4 Ser) 3  peptide linker was inserted between the two protein domains. The (Gly 4 Ser) 3  peptide linker was encoded on the PCR primers SEQ ID NO: 11 (zc27,675) and SEQ ID NO: 10 (zc27,684). 
     The human IL-20RA extracellular domain human immunoglobulin gamma 1 heavy chain constant region fusion construct was generated by overlap PCR of four separate DNA fragments, each generated by separate PCR amplification reactions 
     The first fragment contained an optimized tPA (tissue plasminogen activator) signal sequence. The otPA signal sequence was amplified using oligonucleotide primers SEQ ID NO: 13 (zc27,525) and SEQ ID NO: 14 (zc27,526) using an in-house previously generated expression vector as the template. 
     The second fragment contained the IL-20RA extracellular domain coding region consisting of amino acids 1 to 214. Oligonucleotide primers SEQ ID NO: 15 (zc27,524) and SEQ ID NO: 16 (zc27,674) were used to amplify this IL-20RA? segment using a previously generated clone of IL-20RA as the template. 
     The human gamma 1 heavy chain constant region was generated from 2 segments. The first segment containing the C H 1 domain was amplified using oligonucleotide primers SEQ ID NO: 17 (zc27,676) and SEQ ID NO: 18 (zc28,077) using a clone of the wild type human gamma 1 heavy chain constant region as the template. The second segment containing the remaining hinge, C H 2, and C H 3 domains of the human immunoglobulin gamma 1 heavy chain constant region was generated by PCR amplification using oligonucleotide primers SEQ ID NO: 19 (zc28,076) and SEQ ID NO: 20 (zc27,523). 
     The four protein coding domains were linked by overlap PCR using oligonucleotides SEQ ID NO: 13 (zc27,525) and SEQ ID NO: 20 (zc27,523). A (Gly 4 Ser) 3  peptide linker was inserted between the zcytor7 and CH1 protein domains. The (Gly 4 Ser) 3  peptide linker was encoded on the PCR primers SEQ ID NO: 17 (zc27,676) and SEQ ID NO: 16 (zc27,674). 
     The IL-20RB extracellular domain human immunoglobulin kappa light chain constant region fusion coding segment was cloned into the second MCS while the human IL-20RA extracellular domain human immunoglobulin gamma 1 heavy chain constant region fusion coding segment was cloned into the first MCS of pEZE3. 
     The plasmid was used to transfect CHO cells. The cells were selected in medium without hypoxanthine or thymidine and the transgene was amplified using methotrexate. The presence of protein was assayed by Western blotting using anti human gamma 1 heavy chain constant region and anti human kappa light chain antibodies. 
     The IL-20RB extracellular domain human immunoglobulin kappa light chain constant region fusion protein and DNA sequence are shown in SEQ ID NOs: 21 and 22. 
     The IL-20RA extracellular domain human immunoglobulin gamma 1 heavy constant region fusion protein and DNA sequence are shown in SEQ ID NOs: 23 and 24. 
     EXAMPLE 3   
     IL-20RA/B Receptor-Ig Fusion Protein 
     The expression vector pEZE3 was used to express the recombinant IL-20RA/B receptor-Ig fusion protein. pEZE3 is derived from pDC312. pDC312 was obtained through license from Immunex Corporation. pDC312 and pEZE3 contain an EASE segment as described in WO 97/25420. The presence of the EASE segment in an expression vector can improve expression of recombinant proteins two to eight fold in stable cell pools. 
     pEZE3 is a tricistronic expression vector that may be used to express up to three different proteins in mammalian cells, preferably Chinese Hamster Ovary (CHO) cells. The pEZE3 expression unit contains the CMV enhancer/promoter, the adenovirus tripartite leader sequence, a multiple cloning site for insertion of the coding region for the first recombinant protein, the polioviruse type 2 internal ribosome entry site, a second multiple cloning site for insertion of the coding region for the second recombinant protein, an encephalomyocarditis virus internal ribosome entry site, a coding segment for mouse dihydrofolate reductase, and the SV40 transcription terminator. In addition, pEZE3 contains an  E. coli  origin of replication and the bacterial beta lactamase gene. 
     The IL-20RA/B receptor-Ig fusion protein is a disulfide linked heterotetramer consisting of two chains of the human IL-20RB protein extracellular domain fused to the wild type human immunoglobulin kappa light chain constant region and two chains of the human IL-20RA protein extracellular domain fused to a mutated human immunoglobulin gamma 1 constant region. The human immunoglobulin gamma 1 constant region contains amino acid substitutions to reduce Fc?RI binding and C1q complement fixation. 
     The human IL-20RB extracellular domain human immunoglobulin kappa light chain constant region fusion construct was generated by overlap PCR. The IL-20RB coding segment consists of amino acids 1 to 230. The template used for the PCR amplification of the IL-20RB segment was a previously generated IL-20RB human kappa light chain constant region expression construct. Oligonucleotide primers SEQ ID NO: 9 (zc27,522) and SEQ ID NO: 10 (zc27,684) were used to amplify the IL-20RB segment. The entire wild type human immunoglobulin kappa light chain constant region was used. The template used for the PCR amplification of the wild type human immunoglobulin kappa light chain constant region segment was a previously generated IL-20RB human kappa light chain constant region expression construct. Oligonucleotide primers SEQ ID NO: 11 (zc27,675) and SEQ ID NO: 12 (zc27,685) were used to amplify the wild type human immunoglobulin kappa light chain constant region. The two protein coding domains were linked by overlap PCR using oligonucleotides SEQ ID NO: 9 (zc27,522) and SEQ ID NO: 12 (zc27,685). A (Gly 4 Ser) 3  peptide linker was inserted between the two protein domains. The (Gly 4 Ser) 3  peptide linker was encoded on the PCR primers SEQ ID NO: 11 (zc27,675) and SEQ ID NO:10 (zc27,684). 
     The human IL-20RA extracellular domain human immunoglobulin gamma 1 heavy chain constant region fusion construct was generated by overlap PCR of four separate DNA fragments, each generated by separate PCR amplification reactions 
     The first fragment contained an optimized tPA (tissue plasminogen activator) signal sequence. The otPA signal sequence was amplified using oligonucleotide primers SEQ ID NO: 13 (zc27,525) and SEQ ID NO: 14 (zc27,526) using an in-house previously generated expression vector as the template. 
     The second fragment contained the IL-20RA extracellular domain coding region consisting of amino acids 1 to 214. Oligonucleotide primers SEQ ID NO: 15 (zc27,524) and SEQ ID NO: 16 (zc27,674) were used to amplify this IL-20RA segment using a previously generated clone of IL-20RA as the template. 
     The human gamma 1 heavy chain constant region was generated from 2 segments. The first segment containing the C H 1 domain was amplified using oligonucleotide primers SEQ ID NO: 17 (zc27,676) and SEQ ID NO: 18 (zc28,077) using a clone of the wild type human gamma 1 heavy chain constant region as the template. The second segment containing the remaining hinge, C H 2, and C H 3 domains of the human immunoglobulin gamma 1 heavy chain constant region was generated by PCR amplification using oligonucleotide primers SEQ ID NO: 19 (zc28,076) and SEQ ID NO: 20 (zc27,523). 
     The four protein coding domains were linked by overlap PCR using oligonucleotides SEQ ID NO: 13 (zc27,525) and SEQ ID NO: 20 (zc27,523). A (Gly 4 Ser) 3  peptide linker was inserted between the zcytor7 and CH1 protein domains. The (Gly 4 Ser) 3  peptide linker was encoded on the PCR primers SEQ ID NO: 17 (zc27,676) and SEQ ID NO: 16 (zc27,674). 
     The IL-20RB extracellular domain human immunoglobulin kappa light chain constant region fusion coding segment was cloned into the second MCS while the human IL-20RA extracellular domain human immunoglobulin gamma 1 heavy chain constant region fusion coding segment was cloned into the first MCS of pEZE3. 
     The plasmid was used to transfect CHO cells. The cells were selected in medium without hypoxanthine or thymidine and the transgene was amplified using methotrexate. The presence of protein was assayed by Western blotting using anti human gamma 1 heavy chain constant region and anti human kappa light chain antibodies. 
     The IL-20RB extracellular domain human immunoglobulin kappa light chain constant region fusion protein and DNA sequence are shown in SEQ ID NOs: 21 and 22, the mature polypeptide sequence of which is SEQ ID NO: 41. 
     The IL-20RA extracellular domain human immunoglobulin gamma 1 heavy constant region fusion protein and DNA sequence are shown in SEQ ID NOs: 23 and 24, the mature polypeptide sequence of which is SEQ ID NO: 39. 
     EXAMPLE 4  
     Construction of an IL-20 Receptor Heterodimer 
     A vector expressing a secreted hIL-20RA/hIL-20B heterodimer was constructed. In this construct, the extracellular domain of hIL-20RA was fused to the heavy chain of IgG gamma 1 (IgGγ1), while the extracellular portion of IL-20RB was fused to human kappa light chain (human κ light chain). 
     Construction of IgG Gamma 1 and Human κ Light Fusion Vectors 
     The heavy chain of IgGγ1 was cloned into the Zem229R mammalian expression vector (ATCC deposit No. 69447) such that any extracellular portion of a receptor having a 5′ EcoRI and 3′ NheI site can be cloned in, resulting in an N-terminal extracellular domain-C-terminal IgGγ1 fusion. The IgGγ1 fragment used in this construct was made by using PCR to isolate the IgGγ1 sequence from a Clontech hFetal Liver cDNA library as template. A PCR reaction using oligos (SEQ ID NO: 25) ZC11,450 and (SEQ ID NO: 26) ZC11,443 was run as follows: 40 cycles of 94° for 60 sec., 53° C. for 60 sec., and 72° for 120 sec.; and 72° C. for 7 min. PCR products were separated by agarose gel electrophoresis and purified using a QiaQuick™ (Qiagen) gel extraction kit. The isolated, 990 bp, DNA fragment was digested with MluI and EcoRI (Boerhinger-Mannheim), ethanol precipitated and ligated with oligos (SEQ ID NO: 27) ZC11,440 and (SEQ ID NO: 28) ZC11,441, which comprise an MluI/EcoRI linker, into Zem229R previously digested with MluI and EcoRI using standard molecular biology techniques disclosed herein. This generic cloning vector was called Vector#76 hIgGgamma1 w/Ch1 #786 Zem229R (Vector #76). The polynucleotide sequence of the extracellular domain of hIL-20RA fused to the heavy chain of IgG gamma 1 is show in SEQ ID NO: 29 and the corresponding polypeptide sequence shown in SEQ ID NO: 30, the mature sequence of which is SEQ ID NO: 40. 
     The human κ light chain was cloned in the Zem228R mammalian expression vector (ATCC deposit No. 69446) such that any extracellular portion of a receptor having a 5′ EcoRI site and a 3′ KpnI site can be cloned in, resulting in an N-terminal extracellular domain-C-terminal human κ light chain fusion. The human κ light chain fragment used in this construct was made by using PCR to isolate the human κ light chain sequence from the same Clontech hFetal Liver cDNA library used above. A PCR reaction using oligos (SEQ ID NO: 31) ZC11,501 and (SEQ ID NO: 32) ZC11,451 was run under condition described above. PCR products were separated by agarose gel electrophoresis and purified using a QiaQuick™ (Qiagen) gel extraction kit. The isolated, 315 bp, DNA fragment was digested with MluI and EcoRI (Boerhinger-Mannheim), ethanol precipitated and ligated with the MluI/EcoRI linker described above, into Zem228R previously digested with MluI and EcoRI using standard molecular biology techniques disclosed herein. This generic cloning vector was called Vector #77 hκight #774 Zem228R (Vector #77). The polynucleotide sequence of the extracellular portion of IL-20RB fused to human kappa light chain is shown in SEQ ID NO: 33 and the corresponding polypeptide sequence shown in SEQ ID NO: 34, the mature sequence of which is SEQ ID NO: 42. 
     Insertion of hIL-20RA and IL-20RB Extracellular Domains into Fusion Vector Constructs 
     Using the construction vectors above, a construct having human IL-20RA fused to IgGγ1 was made. This construction was done by PCRing human IL-20RA receptor from hIL-20RA/IgG Vector #102 with oligos (SEQ ID NO: 35) ZC12,909 and (SEQ ID NO: 36) ZC26,564 under conditions described as follows: 30 cycles of 94° C. for 60 sec., 57° C. for 60 sec., and 72° C. for 120 sec.; and 72° C. for 7 min. The resulting PCR product was digested with EcoRI and NheI, gel purified, as described herein, and ligated into a previously EcoRI and NheI digested and band-purified Vector #76 (above). The resulting vector was sequenced to confirm that the human IL-20Rα/IgG gamma 1 fusion (hIL-20RA/Ch1 IgG) was correct. The hIL-20RA/Ch1 IgG gamma 1 #1825 Zem229R vector was called vector #195. 
     A separate construct having IL-20RB fused to κ light was also constructed. The IL-20RB/human κ light chain construction was performed as above by PCRing from DR1/7N-4 with oligos (SEQ ID NO: 37) ZC26,602 and (SEQ ID NO: 38) ZC26,599, digesting the resulting band with EcoRI and KpnI and then ligating this product into a previously EcoRI and KpnI digested and band-purified Vec#77 (above). The resulting vector was sequenced to confirm that the IL-20RB/human κ light chain fusion (IL-20RB/κlight) was correct. This IL-20RB//κlight #1833 Zem228R vector was called Vector #194. 
     Co-expression of the Human IL-20RA and Human IL-20RB Receptors 
     Approximately 16 μg of each of vectors #194 and #195, above, were co-transfected into BHK-570 cells (ATCC No. CRL-10314) using LipofectaminePlus™ reagent (Gibco/BRL), as per manufacturer&#39;s instructions. The transfected cells were selected for 10 days in DMEM+5% FBS (Gibco/BRL) containing 1 μM of methotrexate (MTX) (Sigma, St. Louis, Mo.) and 0.5 mg/ml G418 (Gibco/BRL) for 10 days. The resulting pool of tranfectants was selected again in 10 μM MTX and 0.5 mg/ml G418 for 10 days. 
     The resulting pool of doubly selected cells was used to generate protein. Three factories (Nunc, Denmark) of this pool were used to generate 8 L of serum free conditioned medium. This conditioned media was passed over a 1 ml protein-A column and eluted in (10) 750 microliter fractions. 4 of these fractions found to have the highest concentration were pooled and dialyzed (10 kD MW cutoff) against PBS. Finally, the dialyzed material was analyzed by BCA (Pierce) and found to have a concentration of 317 μg/ml. A total of 951 μg was obtained from this 8 L purification. 
     EXAMPLE 5 
     Proliferation Assay on Baf3/IL-20RA/IL-20RB Stable Cell Lines 
     Object of the Example: 
     The object of the present example was to determine if IL-19 could bind to cell lines that express the IL20RA/IL-20RB heterodimeric receptor.
         IL-19 was placed in a dose response proliferation assay in Baf3/IL-20RA/IL-20RB Stable Cell Lines. The proliferation assay was set up as follows:       Day 1: A 96-well plate at 5000 cells/well was seeded with a dose response of IL-19 from 6 ng/ml down to 0.01 ng/ml and controls, and the cells were incubated at 37° C.   Day 4: 20 μl of Alamar Blue were placed in each well and let the cells were incubated at 37° C. overnight.   Day 5: The plate on the plate reader in robotics in Fluoresces Units (544 nm ex./590 nm em.). The data are shown below.
 
Results: The data below are the number of cells in each well and indicates that the cells proliferated in a dose-dependent response to IL-19.
   

     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                   
                 Basal 
                 0.01 ng/ml 
                 0.02 ng/ml 
                 0.05 ng/ml 
                 0.09 ng/ml 
                 0.19 ng/ml 
               
               
                   
               
               
                 IL-19 (A096G) 
                 351 
                 952 
                 1463 
                 2415 
                 3406 
                 4110 
               
               
                   
                 15.76368 
                 114.4513 
                 156.6867 
                 265.7708 
                 122.874 
                 33.92484 
               
               
                   
                 15.76 
                 59.29149 
                 93.94366 
                 74.18359 
                 144.9331 
                 136.9183 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                 0.38 ng/ml 
                 0.75 ng/ml 
                 1.5 ng/ml 
                 3 ng/ml 
                 6 ng/ml 
               
               
                   
                   
               
               
                   
                 IL-19 (A096G) 
                 4528 
                 4962 
                 5194 
                 5499 
                 5664 
               
               
                   
                   
                 172.5072 
                 185.7348 
                 177.8779 
                 92.49958 
                 83.41251 
               
               
                   
                   
                 84.89956 
                 49.76869 
                 83.2038 
                 49.12525 
                 43.42404 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
                 12 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 A 
                 6528.9 
                 5722.8 
                 5619.8 
                 5492.3 
                 5338.3 
                 4896.2 
                 4285.9 
                 3621 
                 3563.9 
                 2104 
                 1443.5 
                 373.79 
               
               
                 B 
                 6544.8 
                 5540.1 
                 5421.6 
                 5133.1 
                 4976.4 
                 4676.9 
                 4376.6 
                 3933.5 
                 3240.5 
                 2221.8 
                 1149.4 
                 351.74 
               
               
                 C 
                 6554.7 
                 5541.9 
                 5402.7 
                 5160.9 
                 4981.9 
                 4646.2 
                 4325.9 
                 3908.5 
                 3029.9 
                 2071.4 
                 1181 
                 321.27 
               
               
                 D 
                 6457.9 
                 5689.5 
                 5397.3 
                 5012.6 
                 4835.6 
                 4409.4 
                 4304.4 
                 3831.3 
                 2849.4 
                 1794.4 
                 1276.7 
                 368.39 
               
               
                 E 
                 6537.7 
                 5627.4 
                 5496.6 
                 5304 
                 4962.9 
                 4622 
                 4341.3 
                 3573.1 
                 2521.7 
                 1390.6 
                 921.81 
                 340.1 
               
               
                 F 
                 6494.5 
                 5708 
                 5532.4 
                 5235.2 
                 4880.5 
                 4603.9 
                 4055.3 
                 3433.2 
                 2416.2 
                 1423.1 
                 872.13 
                 341.37 
               
               
                 G 
                 6492.6 
                 5613.8 
                 5419.6 
                 5082.8 
                 5002 
                 4445.3 
                 4061.1 
                 3173.9 
                 2312.1 
                 1413.5 
                 989.98 
                 352.52 
               
               
                 H 
                 6562.8 
                 5705.8 
                 5546.2 
                 5154.9 
                 5002.8 
                 4442 
                 3983.1 
                 3444.6 
                 2408.8 
                 1624.3 
                 1025 
                 359.24 
               
               
                   
               
            
           
         
       
     
     EXAMPLE 6   
     Neutralization Assay of IL-19 
     Object of the Example: 
     The object of the present example was to determine if the soluble IL-20RA/IL-20RB heterodimeric receptor could neutralize IL-19.
     Day 1: Baby hamster kidney (BHK) cells expressing the IL-20RA/IL-20RB heterodimeric receptor were plated at 1000 cells/well in a 96 well plate.   Day 2: The cells were re-plated into serum-free medium to down regulate their response.   Day 3: Three different solutions containing IL-19 were made, one having a concentration of 0.1 ng/ml, the second solution having a concentration of 1 ng/ml and the third having a concentration of 10 ng/ml.   

     As a control experiment, 100 μl aliquots of each of the solutions of IL-19 were placed in different cell-containing wells to determine the level of proliferation of the cells caused by IL-19. 
     In a second experiment, 100 μl of a solution containing the soluble IL-20A/IL-20B heterodimeric receptor having a concentration of 10 μg/ml were mixed with 100 μl aliquots of each of the solutions of IL-19 and vortexed to thoroughly mix the solutions. The solutions were then let to sit at room temperature for 30 minutes. The mixed solutions were then loaded in triplicate in the wells containing the BHK cells that express the IL-20RA/IL-20RB receptors. The microtiter plates containing the cells were then incubated at 37° C. for 4 hours, then read on a luminometer and the data collected. 
     The data in the tables below indicate the number of cells present at the end of the experiment. As can be seen the soluble receptor neutralized some of IL-19&#39;s activity at all three concentrations (especially the higher concentration) when compared to IL-19&#39;s activity alone. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Basal 
                 0.1 ng/ml 
                 1 ng/ml 
                 10 ng/ml 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 zmda1 Alone 
                 3370 
                 11488 
                 18684 
                 25148.33 
               
               
                 Soluble  
                 80.06664 
                 282.8722 
                 223.1457 
                 770.5052 
               
               
                 Receptor 
                   
                   
                   
                   
               
               
                 (A442F)  
                   
                   
                   
                   
               
               
                 10 μg/ml 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                   
                 Basal 
                 0.1 ng/ml 
                 1 ng/ml 
                 10 ng/ml 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Soluble  
                 3574.667 
                 6115.333 
                 13160.67 
                 20687 
               
               
                   
                 Receptor 
                   
                   
                   
                   
               
               
                   
                 (A442F) 
                   
                   
                   
                   
               
               
                   
                 10 μg/ml  
                   
                   
                   
                   
               
               
                   
                 +Zmda1 
                 105.3291 
                 435.0788 
                 672.2645 
                 582.3624