Involvement of toll-like receptor 4 in innate immunity to respiratory syncytial virus

The mammalian Toll-like receptor 4, TLR4, is an important component in the innate immune response to gram-negative bacterial infection. The role of TL R4 in antiviral immunity has been largely unexplored. In this study, the in vivo immune responses to respiratory syncytial virus (RSV) and influenza v irus infection were examined in TLR4-deficient (C57BL/10ScNCr) and TLR4-exp ressing (C57BL/10Sn) mice. TLR4-deficient mice challenged with RSV, but not influenza virus, exhibited impaired natural killer (NK) cell and CD14(+) c ell pulmonary trafficking, deficient NK cell function, impaired interleukin -12 expression, and impaired virus clearance compared to mice expressing TL R4. These findings suggest that Toll signaling pathways have an important r ole in innate immunity to RSV.