Bacterial vaginosis-driven changes in vaginal T cell phenotypes and their implications for HIV susceptibility.

Bacterial vaginosis (BV) is a dysbiosis of the vaginal microbiome that is prevalent in reproductive-age women worldwide. Adverse outcomes associated with BV include an increased risk of sexually acquired Human Immunodeficiency Virus (HIV), yet the immunological mechanisms underlying this association are not well understood. To investigate BV driven changes to cervicovaginal tract (CVT) and circulating T cell phenotypes, participants with or without BV provided vaginal tract (VT) and ectocervical (CX) tissue biopsies and peripheral blood mononuclear cells (PBMC). Immunofluorescence analysis of genital mucosal tissues revealed a reduced density of CD3 ⁺ CD4 ⁺ CCR5 ⁺ cells in the VT lamina propria of individuals with compared to those without BV (median 243.8 cells/mm ² BV- vs 106.9 cells/mm ² BV+, p=0.043). High-parameter flow cytometry of VT biopsies revealed an increased frequency in individuals with compared to those without BV of dysfunctional CD39 ⁺ conventional CD4 ⁺ T cells (Tconv) (median frequency 15% BV- vs 30% BV+, p _adj =0.0331) and tissue-resident CD69 ₊ CD103 ⁺ Tconv (median frequency 24% BV- vs 38% BV+, p _adj =0.0061), previously reported to be implicated in HIV acquisition and replication. Our data suggests that BV elicits diverse and complex VT T cell alterations and expands on potential immunological mechanisms that may promote adverse outcomes including HIV susceptibility.