Cloning and expression of caprine interferon-gamma

Caprine interferon-gamma (IFN-gamma) cDNA was cloned from mitogen stimulated peripheral blood mononuclear cell (PBMC) RNA utilizing the reverse transcription-polymerase chain reaction (RT-PCR). The cDNA open reading frame (ORF) is 498bp, encoding a putative 166 amino acid (aa) protein (19327Da). The predicted aa sequence homology of caprine IFN-gamma and the corresponding ovine, bovine and cervine cytokine is 98.8%, 95.2% and 92.8%, respectively. IFN-gamma cDNA was subcloned and expressed in two different plasmids under the control of either the human cytomegalovirus (CMV) immediate early promoter or the caprine arthritis-encephalitis virus long terminal repeat (CAEV LTR). Recombinant caprine IFN-gamma (rCaIFN-gamma) secreted by transfected COS-7 cells shared at least two antigenic epitopes with recombinant bovine IFN-gamma (rBoIFN-gamma) and exhibited biological activity in the vesicular stomatitis virus (VSV) cytopathic effect reduction assay. In-vivo expression of IFN-gamma cDNA promoted by the CAEV LTR was confirmed by the intramuscular (IM) injection of Balb/C mice with plasmid followed by Western blot analysis of mouse serum against purified rCaIFN-gamma produced in E. coli.