Trichomonas vaginalis extracellular vesicles activate the NLRP3 inflammasome and TLR3-mediated inflammatory cascades in host cells

Trichomonas vaginalis (TV) is a flagellated parasite that causes trichomoniasis, the most common non-viral sexually transmitted infection (STI), with over 275 million cases annually. TV has been shown to secrete extracellular vesicles (TV-EVs) to regulate intercellular communication between parasites and host immune response; however, the mechanisms by innate immunity against TV-EVs are largely unknown. Herein, we aim to investigate the molecular mechanisms of inflammation induced by TV-EVs and identify novel proteins modulating the immune response in host cells. Firstly, the morphological characteristics of TV-EVs have been analyzed by transmission electron microscope (TEM) and nanoparticle tracking analysis, revealing that the vesicles are round-shaped bilayer membrane structures with size mostly about 100-120 nm. Additionally, the internalization of TV-EVs by host cells has been validated through immunofluorescence and TEM analysis. The multiplex immunoassay identified that TV-EVs induce the secretion of inflammatory cytokines, including CXCL1, IL-6, IL-8 and MIP-1β in THP-1 macrophages and ectocervical cells (Ect). Mechanistically, TV-EVs induce TLR3 overexpression to activate the NF-κB/NLRP3 pathway in THP-1 macrophages. Additionally, TV-EVs activate the PI3K-mediated NF-κB, p38 MAPK and ERK pathways in Ect. Moreover, TV-EV-induced TLR3 overexpression positively regulates the PI3K and NF-κB pathways, while simultaneously suppressing the p38 MAPK and ERK pathways in Ect. Proteomic analysis identified that TV-EVs upregulate MICB and TRAF3IP2, which are also positively regulated by TLR3 and involved in TV-EV-induced inflammatory cascade. Altogether, this study significantly advances our understanding of the immunomodulatory roles of TV-EVs in host cells, paving the way for future treatment of trichomoniasis and TV-associated STIs.