ATYPICAL SPI INTERFERON BINDS ON PORCINE CELLS TO A MAJOR COMPONENT OF TYPE-I INTERFERON RECEPTOR

The short porcine type I interferon (spIIFN), encoded by a gene physio logically expressed by the pig embryonic trophoblast during implantati on, represents the first member of a novel family type I IFN. Binding and cross-linking experiments were carried out to characterize its cel lular receptor, On porcine kidney cells, specific binding of I-125-spI IFN could be displaced significantly by spI IFN, rpIFN-alpha(1), and rhIFN-alpha(1), but not by rhIFN-alpha(2a) or by rpIFN-gamma. On the o ther hand, all these type I IFNs but not rpIFN-gamma were capable of d isplacing bound P-32-hIFN-alpha A-P1 on these cells, Cross-linking dat a show that the specific 120 kD complex formed with these two radiolab eled ligands was displaceable by an excess of both spI IFN and rpIFN-a lpha(1). These results provide primary evidence that spI IFN shares at least the major binding subunit of type I IFN receptor on porcine cel ls, On human WISH cells, I-125-spI IFN did not form any complex, nor d id spI IFN affect crosslinking complexes of P-32-hIFN-alpha A-P1 on th ese cells, unlike rpIFN-alpha(1). The lack of antiviral and antiprolif erative effects of spI IFN on human cells is primarily a result of its inability to recognize human type I TFM receptor.