TLR3 Sensing of Viral Infection

Viral infection is detected by the innate immune system which mounts a rapid semi-selective defence involving inflammation and production of type 1 interferons. Several sensors, both cell surface and intracellular, exist to detect different types of viral motifs. Double-stranded RNA viruses and dsRNA replication intermediates are detected by tolllike receptor 3 (TLR3) as well as by retinoid-inducible gene 1 (RIG-I) like receptors. Binding of dsRNA or its synthetic analogue poly I:C to TLR3 recruits the adaptor protein TRIF and stimulates distinct pathways leading to activation of interferon regulatory factor (IRF) and NFB. Here, we review the signalling cascades initiated by TLR3 and the modulation of these pathways.