Bovine type I interferon receptor protein BoIFNAR-1 has high-affinity and broad specificity for human type I...

The type I interferon receptor (IFNAR) is composed of two transmembrane polypeptides, IFNAR-1 and IFNAR-2. Human IFNAR-1 has low intrinsic affinity for IFNs, but enhances the affinity for IFNs of the complex over that of HuIFNAR-2 alone, and modulates the ligand specificity. Bovine cells respond to human alpha interferons. The bovine homologue of HuIFNAR-1, BoIFNAR-1, when expressed in heterologous cells, confers high-affinity binding and broad specificity for human type I IFNs. A soluble fusion protein of the ectodomain of BoIFNAR-1 and an immunoglobulin Fc domain was produced. In contrast to HuIFNAR-1, this protein competes strongly with human cells for IFN binding, and directly binds a wide spectrum of human type I IFNs, including diverse IFN-alphas, IFN-beta and IFN-omega, with moderate to high affinity. This accounts for much of the specificity for human IFNs possessed by bovine cells, with several exceptions. The BoIFNAR-1 ectodomain, in contrast to HuIFNAR-1, may be useful for studies of binary and ternary complexes with IFNs and IFNAR-2, and for purification, assay and biological neutralization protocols.