Innate pattern-recognition receptors for viral RNA (RNA-sensing PRRs)

Innate pattern-recognition receptors (PRRs) for viral RNA are a specialized group of proteins that detect the presence of viral genetic material within a host cell or the extracellular environment. This group primarily includes endosomal Toll-like receptors (TLRs) such as TLR3, TLR7, and TLR8, and cytosolic RIG-I-like receptors (RLRs) like RIG-I (DDX58) and MDA5 (IFIH1) (Kawai T, Akira S. Immunity. 2011;34(5):637-650; Rehwinkel J, Gack MU. Nat Rev Immunol. 2020;20(9):537-551). Upon binding to specific viral RNA motifs—such as double-stranded RNA or 5'-triphosphorylated single-stranded RNA—these receptors trigger signaling cascades involving adapter proteins like TRIF, MyD88, or MAVS (UniProt Consortium. TLR3 - O15455). These pathways culminate in the activation of transcription factors like IRF3/7 and NF-κB, leading to the production of Type I interferons and pro-inflammatory cytokines (Chow KT, et al. Annu Rev Immunol. 2018;36:667-694). In disease contexts, these receptors are critical for the initial defense against viral infections, but their dysregulation can lead to chronic inflammation or autoimmune disorders such as systemic lupus erythematosus (Barrat FJ, et al. Nat Immunol. 2019;20(12):1574-1583). Therapeutically, agonists of these receptors, such as imiquimod or poly(I:C), are used as vaccine adjuvants and in cancer immunotherapy to boost the immune response, while antagonists are being explored to treat inflammatory conditions (DrugBank Online. Imiquimod - DB00724).

Other names

Viral RNA sensorsRNA-sensing pattern recognition receptorsEndosomal TLRs and RLRsTLR3/7/8/RIG-I/MDA5

Agonism of endosomal Toll-like receptors (TLR3, TLR7, TLR8) or cytosolic RIG-I-like receptors (RIG-I, MDA5) to stimulate the production of Type I interferons and pro-inflammatory cytokines via MyD88, TRIF, or MAVS signaling pathways.