NLRP3 Inflammasome Contributes to Host Defense Against Talaromyces marneffei Infection

Talaromyce marneffei is an important thermally dimorphic pathogen causing disseminated mycoses in immunocompromised individuals in southeast Asia. Previous studies have suggested that NLRP3 inflammasome plays a critical role in antifungal immunity. However, the mechanism underlying the role of NLRP3 inflammasome activation in host defense against T. marneffei remains unclear. We show that T. marneffei yeasts but not conidia induce potent IL-1 beta production. The IL-1 beta response to T. marneffei yeasts is differently regulated in different cell types; T. marneffei yeasts alone are able to induce IL-1 beta production in human PBMCs and monocytes, whereas LPS priming is essential for IL-1 beta response to yeasts. We also find that Dectin-1/Syk signaling pathway mediates pro-IL-1 beta production, and NLRP3-ASC-caspase-1 inflammasome is assembled to trigger the processing of pro-IL-1 beta into IL-1 beta. In vivo, mice deficient in NLRP3 or caspase-1 exhibit higher mortality rate and fungal load compared to wild-type mice after systemic T. marneffei infection, which correlates with the diminished recruitment of CD4 T cells into granulomas in knockout mice. Thus, our study first demonstrates that NLRP3 inflammasome contributes to host defense against T. marneffei infection.