Alum is the only adjuvant approved for routine use in humans, although the basis for its adjuvanticity remains poorly understood. We have recently shown that Alum activates caspase-1 and induces secretion of mature IL-1β and IL-18. Here we show that in human and mice macrophages, alum-induced IL-1β, IL-18, and IL-33 secretion is mediated by the NLR protein NLRP3 and its adaptor ASC, but not by NLRC4. Other particulate adjuvants, such as QuilA and chitosan, induce inflammasome activation in a NLRP3-dependent fashion, suggesting that activation of the NLRP3-inflammasome may be a common mechanism of action of particulate adjuvants. Importantly, we demonstrate that antigen-specific antibody production elicited by vaccines that contain alum is significantly impaired in NLRP3-deficient mice. Our results demonstrate for the first time a role for the NLRP3-inflammasome during development of the immune response elicited by alum-enhanced vaccination. and suggest that therapeutic intervention aimed at NLRP3 may improve adjuvant efficacy.
Keywords: Monocytes/macrophages, Cytokines, Inflammation, Vaccination