Molecular cloning and characterization of chicken lipopolysaccharide-induced TNF-alpha factor (LITAF).

The inflammatory response to parasites, bacteria, and viruses is mediated by multiple host factors. TNF-alpha is one of the most pleiotropic cytokines in mammals, but has yet to be identified in avian species. In the current study, we isolated a full-length cDNA encoding the chicken homologue of LPS-induced TNF-alpha factor (LITAF), transcription factor, with an open reading frame of 148 amino acids and a predicted molecular mass of 16.0kDa. Quantitative RT-PCR analysis showed that chicken LITAF mRNA was predominantly expressed in spleen and intestinal intraepithelial lymphocytes (IELs). LITAF mRNA levels were up-regulated following in vitro stimulation of macrophages for 4 h with Escherichia coli or Salmonella typhimurium endotoxin, and 18-48 h after treatment with Eimeria acervulina, E. maxima, or E. tenella, three causative agents of avian coccidiosis. LITAF mRNA was up-regulated by more than 700-fold in IELs isolated from E. maxima-infected birds. Purified recombinant LITAF protein expressed in E. coli or COS7 cells exhibited cytotoxic activity against chicken tumor cell lines in vitro, presumably through autocrine activation of TNF-alpha or its chicken homologue. This supposition was strengthened by the fact that treatment of chicken macrophages with recombinant LITAF induced the expression of TL1A (TNFSF 15), a member of the TNF ligand super family. We conclude that chicken LITAF may play an important role in the regulation of TNF-alpha gene expression during the course of coccidiosis or tumorigenesis.