D.Mel-2 cells expressing human RIG-I were infected for 72 h with RVFVΔNSs::REN (RVFV) and then tested for RIG-I conformation (A) and oligomerization (B). (C) In vitro activation of RIG-I. Lysates of RIG-I-expressing D.Mel-2 cells were mixed with lysates of naïve or RVFVΔNSs::REN-infected D.Mel-2 cells, and assayed for RIG-I conformation. (D) Co-immunoprecipitation. D.Mel-2 cells were either left naïve (mock), or only infected with RVFVΔNSs::REN (RVFV), only expressing RIG-I (RIG-I), or were both expressing RIG-I and superinfected with RVFVΔNSs::REN (RIG-I/RVFV). Combinations of lysates were subjected to IP and Western blot analysis using antibodies against RVFV N or RIG-I. As input control, 10% of the cell lysate were analyzed in parallel (left lanes).