Atypical spI Interferon Binds on Porcine Cells to a Major Component of Type I Interferon Receptor

Abstract

The short porcine type I interferon (spI IFN), encoded by a gene physiologically expressed by the pig embryonic trophoblast during implantation, represents the first member of a novel family type I IFN. Binding and cross-linking experiments were carried out to characterize its cellular receptor. On porcine kidney cells, specific binding of ¹²⁵I-spI IFN could be displaced significantly by spI IFN, rpIFN-α₁, and rhIFN-α₁, but not by rhIFN-α_2a or by rpIFN-γ. On the other hand, all these type I IFNs but not rpIFN-γ were capable of displacing bound ³²P-hIFN-αA-P1 on these cells. Cross-linking data show that the specific 120 kD complex formed with these two radiolabeled ligands was displaceable by an excess of both spI IFN and rpIFN-α₁. These results provide primary evidence that spI IFN shares at least the major binding subunit of type I IFN receptor on porcine cells. On human WISH cells, ¹²⁵I-spI IFN did not form any complex, nor did spI IFN affect crosslinking complexes of ³²P-hIFN-αA-P1 on these cells, unlike rpIFN-α₁. The lack of antiviral and antiproliferative effects of spI IFN on human cells is primarily a result of its inability to recognize human type I IFN receptor.