Figure 1.

RSV and IAV single-stranded RNA and double-stranded RNA moieties generated during viral replication are detected by both endosomal Toll-like receptors (TLR) 3 and TLR7/8, and cytoplasmic pattern recognition receptors (PRRs), resulting in activation of transcription factors interferon regulatory factors (IRF) 3, IRF7, and nuclear factor κB (NF-κB) production of pro-inflammatory cytokines, chemokines, and interferons. RSV and IAV have also been shown to increase expression of cell surface TLR4 and TLR10 PRRs that lead to NF-κB induced transcription of pro-inflammatory cytokine genes. Both viruses are detected by NLRP3 NLRs and activate the inflammasome pathway and downstream expression of IRF3 and NF-κB dependent immune responses, as well as direct production of interleukin (IL)-1B and IL-18.