Also, in a study involving random mutagenesis, rescue of replication-proficient mutants in type I IFN response-deficient cells, and subsequent screening for viruses with an enhanced capacity to induce type I IFN after infection, a similar mutation (I68T), pointing in the same direction of the α-helix in the NS1 protein crystal structure as the mutation I64T (Fig. 6C and data not shown) and affecting the ability of NS1 protein to counteract IFN responses, was found (49). Here, IFNA1 is linked to infection.