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/mm2 BV- vs 106.9 cells/mm2 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+, padj=0.0331) and tissue-resident CD69+CD103+ Tconv (median frequency 24% BV- vs 38% BV+, padj=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.

Oral tolerance to systemic vaccination remains intact without RORγt expression in regulatory T cells.

Many promising vaccine candidates and licensed vaccines lead to variable immune responses within humans. Studies suggest that environmental exposures in the gastrointestinal tract could contribute to a reduction in vaccine efficacy via immune tolerance at this site; this is partly achieved by a high abundance of regulatory T cells (Tregs). It is unclear if Treg subsets regulate systemic vaccine responses following oral antigen pre-exposure. Here, we implemented a conditional knock-out mouse model of RORγt+ Tregs to examine the role of these cells in mediating this process. Following oral exposure to the model antigen ovalbumin (OVA) prior to immunization, we found similar induction of vaccine-induced antibody responses in mice lacking RORγt expression in Tregs compared to sufficient controls. Use of various adjuvants led to distinct findings. Our data suggest that expression of RORγt+ within Tregs is not required to regulate tolerance to systemic vaccination following oral antigen exposure.