Submitted to: International Cytokine Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 5, 2004
Publication Date: January 5, 2005
Citation: Lillehoj, E.P., Min, W., Lillehoj, H.S. 2005. Isolation and characterization of cdnas encoding chicken il-16 and il-17. International Cytokine Society Annual Meeting p. 35.
Only a limited number of cytokine genes have been cloned from avian spp. due to low sequence homologies with their mammalian counterparts. As an alternative approach, we prepared an EST cDNA library from intestinal intraepithelial lymphocytes of Eimeria acervulina-infected chickens and enriched for proinflammatory cytokine genes as potential vaccine/adjuvant candidates. The library contained 34,708 unique sequences with an average insert size of 1.7 kb, and 3.7 ESTs/contig (GenBank accession nos. CD726833-CD740810, CF074760-CF075157). Comparison of the sequence data from 14,409 clones with GenBank sequences identified 125 novel genes, including two previously unidentified cytokines, IL-16 and IL-17. The IL-16 clone contained a 1,821 bp full-length open reading frame predicted to encode a protein of 607 amino acids (63.5 kDa) with 49-52% sequence identity to mammalian homologues. By Northern blot analysis, IL-16 transcripts were identified in lymphoid, but not non-lymphoid tissues. A recombinant protein containing the COOH-terminal 149 amino acids of IL-16 expressed in COS-7 cells showed chemoattractive activity for splenic lymphocytes. Similarly, a 917 bp cDNA encoding the IL-17 gene was isolated. It contained a 507 bp full-length open reading frame predicted to encode a protein of 169 amino acids (18.9 kDa) containing a 27 residue NH2-terminal signal peptide, a single potential N-linked glycosylation site, and 6 cysteine residues conserved with mammalian IL-17s. IL-17 shared 37-46% amino acid sequence identity to the previously described mammalian homologues and was homologous to open reading frame 13 of Herpesvirus saimiri (HSV 13). IL-17 transcripts were identified in a reticuloendotheliosis virus-transformed lymphoblast cell line and Con A-stimulated splenic lymphocytes but not other cell lines or tissues. Conditioned medium from COS-7 cells transfected with the IL-17 cDNA induced IL-6 production by chicken embryonic fibroblasts suggesting a functional role for the cytokine in avian immunity. Supported by National Research Initiative grant 2002-35205-12838 from USDA.