To evaluate whether infection with candidate oncolytic VACV (WR/TK−/Δ, WR/TK−/2Δ, and WR/TK−/3Δ) leads to activation of the IRF3 pathway, we determined the amounts of phosphorylated IRF3 (p-IRF3) by western blot after infection of human cancer cells. Here, IRF3 is linked to infection.