Figure 4.

MAVS is required for optimal IFN suppression by NS protein. IFN induction and IFN response were quantified by the appropriate Luc reporter assays, and RSV growth was measured by plaque assay in Hep-2 cells as previously described^28,38. NS1 and NS2 plasmids have also been described before²⁸, and V is the empty vector control. WT and MAVS KO MEFs were infected with NS1/2-deleted RSV. Where indicated, NS1 and/or NS2 proteins were overexpressed. (A) IFN induction. IFN gene activation was evaluated by the luciferase assays using constructs containing IFNβ gene promoter. (B) IFN response. The ability of NS1/2 to suppress the host cell response to recombinant IFNα was tested by using the ISGF54-Luc reporter assays, and suppression was considerably reduced in MAVS KO cells. (C) RSV growth. Monolayers of WT and MAVS KO MEFs were infected at 1 m.o.i. in the presence of increasing amounts of recombinant IFNα as shown³⁹, and infectious progeny virus, liberated after 24 h, was plaque assayed by serial dilution.