While VF1 from MNV-1 has been shown to inhibit IFN-β induction during infection [19, 29], whether this function is present in MNV-3 is unclear, as reports using VF1 from a variant of MNV-3 that does not persist in immunocompetent mice failed to inhibit RIG-I-dependent induction of a luciferase reporter under the control of the IFN-β promoter [29]. Here, RIGI is linked to infection.