Both RIG-I and MDA5 have two caspase recruitment domains (CARDs) at the N terminus; after activation of the PRR by viral infection, the CARDs of RIG-I or MDA5 interact with the CARD of mitochondrial antiviral signaling protein (MAVS; also known as IPS-1, VISA, and Cardif), providing an initial signal for MAVS activation [14,15,16,17]. Here, MAVS is linked to viral infectious disease.