Ovine interleukin-12: Analysis of biologic function and species comparison

Interleukin-12 (IL-12) is a heterodimeric cytokine produced mainly by phago cytic and antigen-presenting cells (APC). The cDNA encoding the ovine IL-12 (OvIL-12) subunits, p40 and p35, were generated from concanavalin A (ConA) -stimulated peripheral blood mononuclear cells (PBMC). The ovine genes enco ded proteins that had the highest amino acid identity to caprine p40 (99% a mino acid identity) and p35 (97% amino acid identity) and also displayed a high degree of identity with human p40 (84%) and p35 (79%) homologs. To ens ure the equal expression of both subunits, we used the self-cleaving proper ties of the 2A oligopeptide from foot-and-mouth disease virus (FMDV) to exp ress IL-12 as a single, long open reading frame (ORF) encoding p402Ap35. Us ing an in vitro transcription/translation system, we demonstrated that this 2A oligopeptide mediated cleavage of the p402Ap35 into p402A and p35, in a manner similar to the processing of the FMDV polypeptide. Moreover, when e xpressed in COSm6 cells, this self-processing polypeptide encoded a functio nal heterodimer, which elicited biologic activities associated with IL-12 i n other species.