FIG. 1.

RIG-I-dependent signaling of the innate immune response during paramyxovirus infection. (A) wt, RIG-I^−/−, or MDA5^−/− mouse fibroblasts were either mock infected (right panels) or infected with SenV at 100 HA units/ml of medium (left panels) for 12 h. Cells were fixed and stained with primary antibodies specific for IRF-3 and SenV, followed by fluorescent dye-conjugated secondary antibodies. Cellular distribution of IRF-3 (green), SenV gene products (red), and 4′,6′-diamidino-2-phenylindole (DAPI)-stained nuclei (blue) was visualized by immunofluorescence microscopy. (B) wt, RIG-I^−/−, or MDA5^−/− mouse fibroblasts were either mock infected (M) or infected with SenV (SV) at 100 HA units/ml of medium for 24 h (left) or with NDV at a multiplicity of infection (MOI) of 5 for the indicated times (hours) (right). (C) wt, RIG-I^−/−, or MDA5^−/− mouse fibroblasts were either mock infected or infected with RSV (left) or GFP-RSV (right) at an MOI of 5 for the indicated times (hours). Cells were collected and analyzed by immunoblotting for expression of ISG15, ISG54, ISG56, RIG-I, MDA5, viral proteins, and actin (used as a control). (D) wt, RIG-I^−/−, or MDA5^−/− mouse fibroblasts were either mock infected or infected with either RFP-NDV (left) or GFP-RSV (right) at the indicated MOI for 48 h; then they were fixed, and virus replication was analyzed using fluorescence microscopy.