RIGI and viral infectious disease: In general, toll like receptor (TLR) families, retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5, encoded by IFIH1 gene) are intracellular pattern-recognition receptors (PRRs) that function as viral infection detectors and all contribute to type I interferon (IFN) production15.