Submitted to: Journal of Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 2, 1998
Publication Date: N/A
Interpretive Summary: Avian coccidiosis is a major parasitic disease of poultry for which no recombinant vaccine is currently available. Understanding the nature of host immune system and coccidia parasites is critical for the development of a novel control strategy. In this report, ARS scientists, in collaboration with scientists at the Seoul National University, cloned a gene which encodes a T-cell growth factor for chickens. This factor is called interleukin-15 and showed growth promoting activity of chicken T cells. Potential use of this factor in coccidiosis control will be explored in the future.
A cDNA encoding chicken interleukin-15 was cloned from a CD4+ T cell hybridoma expression library by screening with a rabbit antibody against a protein fraction of conditioned medium containing T cell growth promoting activity. The chicken IL-15 cDNA contains an open reading frame of 143 amino acids with a single potential N-linked glycosylation site. The predicted m.w. of the encoded protein (16 kDa) matched the size of an immunoreactive band on Western blots of E. coli expressing the recombinant IL-15. Amino acid and nucleotide sequence analyses of chicken IL-15 revealed 34% and 46% homology with bovine IL-15 respectively and lesser homologies to other mammalian IL-15s. Chicken IL-15 contained all 4 highly conserved cysteine residues present in mammalian IL-15 sequences. RT-PCR demonstrated that the chicken IL-15 gene is expressed in many tissues including spleen, intestine, and muscle. Activation of spleen cells with Con A enhanced the expression of IL-15 gene transcripts in a time-dependent manner. CHO-K1 cells transfected with the chicken IL-15 cDNA secreted a biologically active protein supporting the growth of Con A activated spleen lymphocytes. Continuous culture of spleen Con A lymphoblasts with chicken IL-15 over two months resulted in an enriched T lymphocyte population expressing gamma,deltaTCR, CD8alpha, and CD3 cell surface antigens, and mediating spontaneous cytotoxicity against tumor cells.