MX1 and infection: Alternatively, the use of type I IFN as an inducer of Viperin might also explain this discrepancy: indeed, Wang et al. found that overexpression of the splicing variant (lacking exon 5) but not the full length isoform of fathead minnow Viperin could induce the expression of RIG-I, IRF3 IRF7, type I IFN, MxA and PKR in FHM cells and this variant was only expressed upon infection with SVCV and not upon poly(I:C) stimulation [39].