Faculty Opinions recommendation of Role of double-stranded RNA pattern recognition receptors in rhinovirus-induced airway epithelial cell responses.

Rhinovirus (RV), a single-stranded RNA virus of the picornavirus family, is a major cause of the common cold as well as asthma and chronic obstructive pulmonary disease exacerbations. Viral double-stranded RNA produced during replication may be recognized by the host pattern recognition receptors Toll-like receptor (TLR)-3, retinoic acid inducible gene (RIG)-I and melanoma-differentiation-associated gene (MDA)-5. No study has yet identified the receptor required for sensing RV double-stranded (ds)-RNA. To examine this, BEAS-2B human bronchial epithelial cells were infected with intact RV-1B or replication-deficient UV-irradiated virus, and interferon (IFN) and IFN-stimulated gene expression determined by quantitative PCR. The separate requirements of RIG-I, MDA5 and IFN response factor (IRF)-3 were determined using their respective siRNAs. The requirement of TLR3 was determined using siRNA against the TLR3 adaptor molecule TRIF. Intact RV-1B, but not UV-irradiated RV, induced IRF3 phosphorylation and dimerization, as well as mRNA expression of IFN- , IFN- 1, IFN-2/3, IRF7, RIG-I, MDA5, IP-10/CXCL10, IL-8/CXCL8 and GM-CSF. siRNA against IRF3, MDA5 and TRIF, but not RIG-I, decreased RV1B-induced expression of IFN- IFN- 1, IFN-2/3, IRF7, RIG-I, MDA5 and IP-10/CXCL10, but had no effect on IL-8/CXCL8 and GM-CSF. siRNAs against MDA5 and TRIF also reduced IRF3 dimerization. Finally, in primary cells, transfection with MDA5 siRNA significantly reduced IFN expression, as it did in BEAS-2B cells. These results suggest that TLR3 and MDA5, but not RIG-I, are required for maximal sensing of RV dsRNA, and that TLR3 and MDA5 signal through a common downstream signaling intermediate, IRF3.