Role of the inflammasome-related cytokines Il-1 and Il-18 during infection with murine coronavirus

The inflammasome, a cytosolic protein complex that mediates the processing and secretion of pro-inflammatory cytokines, is one of the first responders during viral infection. The cytokines secreted following inflammasome activation, which include IL-1 and IL-18, regulate cells of both the innate and adaptive immune system, guiding the subsequent immune responses. In this study, we used murine coronavirus, mouse hepatitis virus (MHV), infection of the central nervous system and liver to assess of the role of the inflammasome and its related cytokines on pathogenesis and host defense during viral infection. Mice lacking all inflammasome signaling due to the absence of caspase-1 and -11 were more vulnerable to infection, with poor survival and elevated viral replication compared to wild-type mice. Mice lacking IL-1 signaling experienced elevated viral replication but similar survival compared to wild-type controls. In the absence of IL-18, mice had elevated viral replication and poor survival, and this protective effect of IL-18 was found to be due to promotion of interferon gamma production in αβ T cells. These data suggest that inflammasome signaling is largely protective during murine coronavirus infection, in large part due to the pro-inflammatory effects of IL-18.