RIGI and viral infectious disease: Upon virus infection or treatment with agonist, the helicase domains of RIG-I/MDA5 detect virus-derived RNAs, their caspase activation and recruitment domain (CARD) are released and RIG-I/MDA5 becomes activated, the active RIG-I/MDA5 then interacts with mitochondrial antiviral signaling protein (MAVS), a down-stream mitochondrial adaptor molecule via RIG-I CARD and MAVS CARD interactions.