Expression and functional characterization of recombinant chicken interferon-gamma

A cDNA encoding chicken interferon-gamma (chIFN-γ) was cloned from a CD4+ T-cell hybridoma by reverse transcription-polymerase chain reaction (RT-PCR) and expressed in Escherichia coli, COS- and CEC-32 fibroblast cell lines. In general, recombinant chicken IFN-γ (rchIFN-γ) expressed in the COS- and CEC-32 cell lines showed high bioactivity in vitro. The kinetics of IFN-γ gene expression were examined in concanavalin A (Con A)-activated spleen lymphocytes by Northern blot and RT-PCR. IFN-γ mRNA was detected as early as 30 min after Con A activation, reached peak expression at 2 h and then decreased starting at 4 h post Con A activation. A rabbit serum made to a synthetic peptide of IFN-γ immunoprecipitated a 60 kDa E. coli maltose-binding fusion protein of recombinant IFN-γ (MBP-IFN) and a 26–27 kDa secreted protein from COS cells and Con A-activated spleen cells. IFN-γ inhibited vesicular stomatitis virus (VSV) mediated cytotoxicity of chicken embryonic fibroblast (CEF) cells and upregulated the expression of many macrophage cell surface antigens, including class I and class II major histocompatibility complex (MHC) proteins. These results show that chicken IFN-γ possesses anti-viral activity and immunoregulates macrophage activities.