OPN1LW and infection: To test the hypothesis that differences in the susceptibility of carp strains to a CEV infection might be related to a different induction of type I IFN responses, the mRNA expression of the genes encoding interferon a2 and the interferon induced proteins viperin and RNA dependent protein kinase (PKR) were analysed in the gills of carp strains AS, koi, Rop and PS after infection with CEV from the genogroups I and IIa.