A TYPE-I OVINE INTERFERON WITH LIMITED SIMILARITY TO IFN-ALPHA, IFN-OMEGA AND IFN-TAU - GENE STRUCTURE, BIOLOGICAL PROPERTIES AND UNUSUAL SPECIES-SPECIFICITY

A gene encoding a 195 amino-acid (a.a.) polypeptide with a putative 23 a.a. signal sequence that had about 60% a.a. sequence identity to ovi ne interferon-omega (OvIFN-omega) and 55% or less identity to BoIFN-ta u, OVIFN-tau and all known IFN-alpha and -beta has been identified fro m an ovine genomic DNA library. Surprisingly, it shared almost complet e identity to genes for rabbit IFN-omega within its coding sequence an d proximal promoter region, although the two were different in their 3 '-ends. This IFN (tentatively termed ovine IFN-omega variant, OvIFN-om ega v), purified in recombinant form from E. coli, had normal antivira l activity when tested on sheep fetal tongue and brain cells and rabbi t kidney cells, but very low activity towards bovine, goat and human c ells. It competed with I-125-labeled BoIFN-tau for binding to IFN rece ptors on ovine cells. Expression of OvIFN-omega v was not detected by reverse transcription-PCR either in ovine peripheral blood leukocytes infected with Sendai virus, or in any other tissues examined. OvIFN-om ega v may represent a previously unrecognized, non-virally inducible t ype I subtype distinct from IFN-alpha, -beta, -omega and -tau. The pre sence of a conserved gene in rabbit and sheep could reflect a recent i nterspecies transfer.