RIGI and viral infectious disease: The relative importance of TLR3, MDA5 or RIG-I in viral infections has been partly defined by cells derived from TLR3−/−[21], RIG-1−/− or MDA5−/− mice [35], [36], however the importance of each PRR, including their exclusive or redundant roles in various infection models, and their direct relevance to human disease remains a subject of much debate.