The NIH3T3 system with shRNAs corroborates with the data from RIG-I/MDA5 DKO MEFs, suggesting that IFN induction has minimal restrictive effect on the first round of infection for T3D strains, and that IFN signalling does not account for the increased rate of infection by T3DPL relative to T3DTD. This evidence concerns the gene RIGI and infection.