To analyze whether the reduced replication of rSIV NS1 S42P, D92E and S42P/ D92E mutations is the result of an impaired ability of the NS1 protein to block host cell interferon production, the 293 T cells were infected with the 3 mutant viruses and the wt virus at an MOI of 1, and the production of IFN-α and IFN-β of the supernatants was measured by real-time PCR at 24 h post infection. Here, IFNA1 is linked to infection.