Although studies of VP35-mediated IFN antagonism have so far focused on the inhibition of IRF3, it has been demonstrated that a different transcription factor, IRF7, is largely responsible for the induction of type I IFN after virus infection, as evidenced by the abrogation of IFN production in Irf7 −/− mice, but not in Irf3 −/− mice [22]–[24]. This evidence concerns the gene IFNA1 and viral infectious disease.