VACCINIA VIRUS PROTEIN B18R INHIBITS THE ACTIVITY AND CELLULAR-BINDING OF THE NOVEL TYPE INTERFERON-DELTA

The soluble vaccinia virus-encoded protein B18R inhibits the antiviral activity and cellular binding of the type I interferons (IFN)-alpha, -beta and -omega of different mammalian species. Recently, a novel typ e I IFN was detected in pigs and classified as a member of a distinct IFN family designated IFN-delta. Our study aimed to determine if the s tructural properties of this shortest(149 residues long) type I IFN al low its interaction with the type I IFN-binding protein B18R. Experime nts using bovine (MDBK) cells demonstrated that B18R neutralized the a ntiviral activity of porcine IFN-delta with high efficiency. Preincuba tion of B18R with radiolabelled IFN-delta specifically inhibited bindi ng of IFN to bovine cells. These data indicate that the overall confor mation of the novel IFN-delta might be similar to that of other type I IFNs.