HCV Genomic RNA Activates the NLRP3 Inflammasome in Human Myeloid Cells

BACKGROUND: Elevated plasma levels of IL-1β and IL-18 from patients with hepatitis C virus (HCV) infection indicate a possible activation of inflammasome by HCV. METHODOLOGY/PRINCIPAL FINDINGS: To demonstrate whether HCV infection activates the inflammasome, we investigated inflammasome activation from HCV infected hepatic Huh7 cells, or monocytic cells and THP-1 derived macrophages challenged with HCV virions, but no any inflammasome activation was detected in these cells. However, when we transfected HCV genomic RNA into monocytes or macrophages, IL-1β was secreted in a dose-dependent manner. We also detected ASC oligomerization and caspase-1 cleavage in HCV RNA transfected macrophages. Using shRNA-mediated gene silencing or specific inhibitors, we found that HCV RNA-induced IL-1β secretion was dependent on the presence of inflammasome components such as NLRP3, ASC and caspase-1. Furthermore, we also found that RIG-I was dispensable for HCV RNA-induced NLRP3 inflammasome activation, while reactive oxygen species (ROS) production was required. CONCLUSIONS: Our results indicate that HCV RNA activates the NLRP3 inflammasome in a ROS-dependent manner, and RIG-I is not required for this process.