Submitted to: Molecular Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2009
Publication Date: 12/1/2009
Publication URL: http://dx.doi.org/10.1016/j.molimm.2009.08.027
Citation: Kim, S., Miska, K.B., Mcelroy, A., Jenkins, M.C., Fetterer, R.H., Cox, C., Stuard, L., Dalloul, R. 2009. Molecular cloning and functional characterization of avian interleukin-19. Molecular Immunology. 47:476-484. Interpretive Summary: Understanding the components of the immune system of the chicken is very important on many different levels. The chicken is an agricultural animal and therefore keeping the chicken pest and parasite free is a major concern to the poultry produces as well as the consumer. The chicken is also important evolutionarily since it branched off the before the separation of the all the mammalian sub-classes. Thus understanding the chicken immune system is important in better understanding of the vertebrate immune system. This work includes the initial discovery and biological characterization of chicken interleukin 19 (IL-19). Interleukins are major components of the immune system and are used to mediate the responses of different cell types. It appears that chicken IL-19 is biologically active and functions in mediating the Th2 (antibody based) responses in the chicken. Evolutionarily, the chicken IL-19 is similar but basal to mammalian IL-19.
Technical Abstract: The present study describes the cloning and functional characterization of avian interleukin (IL)-19, a cytokine that, in mammals, alters the balance of Th1 and Th2 cells in favor of the Th2 phenotype. The full-length avian IL-19 gene, located on chromosome 26, was amplified from LPS-stimulated chicken monocytes, and cloned into both prokaryotic (pET28a) and eukaryotic (pcDNA3.1) expression vectors. The confirmed avian IL-19 amino acid sequence has 66.5% homology with human and murine IL-19, with a predicted protein sequence of 176 amino acids. Analysis of avian IL-19 amino acid sequence showed six conserved, structurally relevant, cysteine residues as found in mammals, but only one N-glycosylation residue. The recombinant IL-19 (rChIL-19) expressed in the prokaryotic system was purified by Ni+-resin column followed by endotoxin removal. Using purified avian rChIL-19, expression of Th2 cytokines was measured in splenocytes using quantitative real-time PCR (qRT-PCR). In the presence of rChIL-19, expression levels of IL-4 and IL-13, as well as IL-10, were significantly increased after 6- and 12-hr treatments. This was confirmed by treating splenocytes with supernatants from IL-19 transfected cells. Also, avian monocytes incubated with rChIL-19 displayed increased expression of IL-1', IL-6, and IL-19. This study represents the first report for the cloning, expression, and functional characterization of avian IL-19. Taken together, avian IL-19 function seems to be conserved and similar to that of mammals and may play an important role in responses to intracellular poultry pathogens like bacteria and protozoa.