HEK293T cells were transfected using the calcium phosphate precipitate transfection method with specific expression vectors (pCAGGS-E-hA20 (LMBP 3778), pCAGGS-E-RIG-I-CARD (LMBP 6517), pEF-HA-IRF-7 (kindly provided by T. Taniguchi, Graduate School of Medicine and Faculty of Medicine, University of Tokyo)), NF-κB, IRF3, IRF7 reporter plasmids (respectively pConLuc (LMBP3248), pISRE-luc (LMBP4011), pGL3-IFNα4-luc (kindly provided by J. Hiscott, McGill University, Montreal, Quebec, Canada), and pACTbetagal (LMBP4341) for transfection efficiency normalization.