Bacterial Vaginosis‐Associated <i>Prevotella timonensis</i> Enhances Dendritic Cell–T Cell Clustering and Subsequent T Cell Proliferation

Dysbiosis of the vaginal microbiome is associated with increased inflammation in the female genital tract. Microbiota associated with bacterial vaginosis (BV), such as Gardnerella vaginalis, Megasphaera elsdenii, and Prevotella timonensis, replace the health-associated bacterium Lactobacillus crispatus and cause inflammation affecting mucosal integrity and immunity. However, it remains unclear how these BV-associated bacteria modulate immune cells and enhance inflammation. Here, we investigated whether BV-associated bacteria directly affected dendritic cell (DC) function. Notably, P. timonensis but not M. elsdenii induced cell-cell clustering between monocytic cell lines and, importantly, between primary DCs and primary CD4 T cells. Our data indicate that this increased clustering is independent of LFA-1. Moreover, P. timonensis enhanced DC-mediated CD4 T cell proliferation. Altogether, these results suggest that P. timonensis-induced cell-cell clustering contributes to the elevated mucosal inflammation observed during bacterial vaginosis.