RIGI and viral infectious disease: The endosomal TLR3, 7, 8, and 9 interact with extracellular viral nucleic acids while the cytosolic helicases RIG-I and MDA-5 sense intracellular double-stranded (ds)RNA and/or 5′triphosphate single-stranded RNA, two common byproducts of viral infection and replication [2], [3], [4], [5].