The interferon-inducible 204 gene, a member of the Ifi 200 family, is not involved in the antiviral state induction by IFN-alpha, but is required by the mouse cytomegalovirus for its replication.

To examine whether Ifi 200 genes are involved in antiviral state induction by IFNs we expressed mutant forms capable of inactivating the endogenous p204 and analyzed replication of both RNA and DNA viruses following IFN-alpha treatment. Inactivation of p204 does not impair replication of vesicular stomatitis virus, encephalomyocarditis virus, ectromelia virus, and herpes simplex virus 1 and does not alter an IFN-alpha induced antiviral state. By contrast, in cells lacking functional p204, mouse cytomegalovirus (MCMV) replication is strongly inhibited and is not further modulated by IFN-alpha. These results suggest that p204, a member of the Ifi 200 gene family, is not involved in the IFN-alpha-induced antiviral activity against some RNA or DNA viruses, but is required by MCMV for its replication.