Clostridium perfringens virulence factors are nonredundant activators of the NLRP3 inflammasome

Abstract

Inflammasome signaling is a central pillar of innate immunity triggering inflammation and cell death in response to microbes and danger signals. Here, we show that two virulence factors from the human bacterial pathogen Clostridium perfringens are nonredundant activators of the NLRP3 inflammasome in mice and humans. C. perfringens lecithinase (also known as phospolipase C) and C. perfringens perfringolysin O induce distinct mechanisms of activation. Lecithinase enters LAMP1 + vesicular structures and induces lysosomal membrane destabilization. Furthermore, lecithinase induces the release of the inflammasome‐dependent cytokines IL‐1β and IL‐18, and the induction of cell death independently of the pore‐forming proteins gasdermin D, MLKL and the cell death effector protein ninjurin‐1 or NINJ1. We also show that lecithinase triggers inflammation via the NLRP3 inflammasome in vivo and that pharmacological blockade of NLRP3 using MCC950 partially prevents lecithinase‐induced lethality. Together, these findings reveal that lecithinase activates an alternative pathway to induce inflammation during C. perfringens infection and that this mode of action can be similarly exploited for sensing by a single inflammasome. image Clostridium perfringens causes gas gangrene and clostridial myonecrosis in humans. This study shows that the secreted C. perfringens toxins lecithinase and perfringolysin O activate the NLRP3 inflammasome via distinct mechanisms. Perfringolysin O (PFO) is a pore‐forming toxin that mediates K + efflux at the plasma membrane. Lecithinase is a phospholipase that is endocytosed and triggers lysosomal membrane destabilization. Lecithinase is the first example of a microbial phospholipase that activates the mammalian innate immune system. Lecithinase‐driven inflammasome responses do not require GSDMD and NINJ1.