IRF3 and infection: We addressed the role of these transcriptional activators in the IFN-β response to wild-type Listeria and ΔpgdA, and revealed that inactivation of IRF3 totally abrogated this response to both strains while IFN-β induction was significantly but not totally impaired in IRF7-deficient macrophages, indicating that both of these transcription factors are required for induction of IFN-β following infection with L. monocytogenes.