Metronidazole Treatment Failure and Persistent BV Lead to Increased Frequencies of Activated T- and Dendritic-Cell Subsets

Bacterial vaginosis associates with dysfunctional T cells and altered soluble immune factors in the cervicovaginal tract

BACKGROUNDBacterial vaginosis (BV) is a dysbiosis of the vaginal microbiome that is prevalent among reproductive-age females worldwide. Adverse health outcomes associated with BV include an increased risk of sexually acquired HIV, yet the immunological mechanisms underlying this association are not well understood.METHODSTo investigate BV-driven changes to cervicovaginal tract (CVT) and circulating T cell phenotypes, Kinga Study participants with or without BV provided vaginal tract (VT) and ectocervical (CX) tissue biopsies and PBMC samples.RESULTSHigh-parameter flow cytometry revealed an increased frequency of cervical CD4+ conventional T (Tconv) cells expressing CCR5 in BR+ versus BR- women. However, we found no difference in the number of CD3+CD4+CCR5+ cells in the CX or VT of BV+ versus BV- individuals, suggesting that BV-driven increased HIV susceptibility may not be solely attributed to increased CVT HIV target cell abundance. Flow cytometry also revealed that individuals with BV had an increased frequency of dysfunctional CX and VT CD39+ Tconv and CX tissue-resident CD69+CD103+ Tconv cells, reported to be implicated in HIV acquisition risk and replication. Many soluble immune factor differences in the CVT further support that BV elicits diverse and complex CVT immune alterations.CONCLUSIONOur comprehensive analysis expands on potential immunological mechanisms that may underlie the adverse health outcomes associated with BV, including increased HIV susceptibility.TRIAL REGISTRATIONClinicalTrials.gov NCT03701802.FUNDINGThis work was supported by National Institutes of Health grants R01AI131914, R01AI141435, and R01AI129715.

Effect of the vaginal live biotherapeutic LACTIN-V (Lactobacillus crispatus CTV-05) on vaginal microbiota and genital tract inflammation among women at high risk of HIV acquisition in South Africa: a phase 2, randomised, placebo-controlled trial

BACKGROUND

Absence of vaginal lactobacilli and accompanying genital inflammation is associated with HIV acquisition. We aimed to assess how a vaginal live biotherapeutic containing Lactobacillus crispatus affects cervicovaginal microbiota and markers of HIV susceptibility in South African women.

METHODS

This randomised, placebo-controlled, phase 2 trial evaluated LACTIN-V (L crispatus CTV-05), a vaginal live biotherapeutic, compared with placebo in cisgender women in South Africa, aged 18-23 years, recruited at a community-based research clinic. Eligible participants with a Nugent score of 4-10 (indicating intermediate vaginal microbiota or bacterial vaginosis) completed 7 days of oral metronidazole and were randomly assigned (2:1) to LACTIN-V (2 × 109 colony forming units per dose) or placebo (the substrate alone) via an independently generated randomisation sequence. Pharmacists, participants, and investigators were masked to treatment assignment. The study product (or placebo) was dosed daily for 5 days in week 1, then twice per week for an additional 3 weeks. Adverse events were evaluated 4 weeks and 8 weeks after starting the study product. Vaginal swabs (for 16S rRNA sequencing of the vaginal microbiome) and cervicovaginal lavage (for Luminex analysis of immune markers) were collected before metronidazole treatment, before study product (or placebo) administration, and at the week 4 and week 8 follow-up visits. An endocervical cytobrush for flow cytometry analysis of immune cell populations (including CD3+CD4+ T cells, and presence of CCR5 and the activation markers CD38 or HLA-DR) was collected before study product use and at 4 weeks and 8 weeks after study product use. The coprimary outcomes for the trial were (1) safety and acceptability of LACTIN-V, as measured by number of adverse events and a validated questionnaire; (2) presence of a Lactobacillus-dominant vaginal microbial community by 16S rRNA gene sequencing at week 4 and week 8; and (3) comparison of change in genital tract inflammatory markers from before metronidazole treatment to week 4 and week 8 between groups. Safety analyses were done in the intention-to-treat population and efficacy analyses in a modified intent-to-treat population (ie, excluding one person assigned placebo who erroneously received LACTIN-V). This trial is completed and registered on ClinicalTrials.gov (NCT05022212).

FINDINGS

45 Black South African women were randomly assigned to receive LACTIN-V (n=32) or placebo (n=13). One woman in each group discontinued the trial during the intervention and two women discontinued during the follow-up. No severe or serious adverse events were observed. Solicited adverse events occurred in 35 (78%) of 45 participants with no significant difference by group (risk ratio 1·17, 95% CI 0·79-1·75; p=0·44). All local solicited adverse events were mild. 32 (71%) of 45 participants strongly agreed or agreed they would use the product again. L crispatus dominant microbiomes were identified in 13 (41%) of 32 participants in the LACTIN-V group at week 4 and eight (26%) of 31 at week 8, compared with none at week 4 and one (9%) of 11 in week 8 in the placebo group (week 4 p=0·0088; week 8 p=0·40). The proportion of activated endocervical HIV target cells out of total T cells increased from after metronidazole treatment to week 4 in the placebo group (median log2 fold change 1·891, IQR 1·731-4·018) but not in the LACTIN-V group (1·062, 0·449-1·424; p=0·016). Changes in the concentrations of 13 immune markers from before metronidazole treatment to week 4 or week 8 were not significantly different by group.

INTERPRETATION

The use of LACTIN-V after metronidazole significantly increased vaginal L crispatus colonisation during 4 weeks of use, although this increase was transient, and women in the placebo group had an increase in endocervical CD4+ HIV target cells during recovery compared with the LACTIN-V group. These results show that vaginal colonisation with an L crispatus live biotherapeutic is possible in an African context, and that optimisation of this strategy might be a way to decrease risk for HIV.

FUNDING

US National Institute of Child Health and Human Development and US National Institute of Allergy and Infectious Diseases.

Association between changes in genital immune markers and vaginal microbiome transitions in bacterial vaginosis

Bacterial vaginosis (BV), characterized by an imbalance in the vaginal microbiota, is a prevalent condition among women of reproductive age and a risk factor for human immunodeficiency virus, sexually transmitted infections, and preterm birth. BV is generally considered to induce mucosal inflammation, but the specific pathways and cell types involved are not well characterized. This prospective study aimed to assess associations between microbial changes and mucosal immune responses in BV patients. Therefore, samples from 20 premenopausal women with BV and treated with metronidazole were analyzed. Vaginal swabs, menstrual cup, and endocervical cytobrush samples were collected before treatment, weekly for four weeks, and at 2, 4, and 6 months for Nugent scoring, immune cell populations and cytokine analysis. Of 105 study intervals, 27 (25.7%) showed improvement in Nugent category, 61 (58.1%) remained unchanged, and 17 (16.2%) worsened. Improvement correlated with decreased monocytes (p = 0.005), while worsening was linked to increased monocytes (p < 0.001) and dendritic cells (p = 0.02). B cells (p = 0.02) and IFN-γ-induced chemokines - IP-10 (p = 0.007), MIG (p = 0.049), and ITAC (p = 0.005) - were associated with improvement. In conclusion, although the T-cell-associated chemokines IP-10, ITAC, and MIG were strongly associated with improvements in Nugent category, our findings indicate that antigen-presenting cells, particularly monocytes, show the most dynamic response to shifts in the vaginal microbiota in patients with BV.

Bacterial vaginosis-driven changes in cervicovaginal immunity that expand the immunological hypothesis for increased HIV susceptibility

Bacterial vaginosis (BV) is a dysbiosis of the vaginal microbiome that is prevalent among reproductive-age females worldwide. Adverse health outcomes associated with BV include an increased risk of sexually-acquired 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 PBMC samples. High-parameter flow cytometry revealed an increased frequency of cervical conventional CD4+ T cells (Tconv) expressing CCR5. However, we found no difference in number of CD3+CD4+CCR5+ cells in the CX or VT of BV+ vs BV- individuals, suggesting that BV-driven increased HIV susceptibility may not be solely attributed to increased CVT HIV target cell abundance. Flow cytometry also revealed that individuals with BV have an increased frequency of dysfunctional CX and VT CD39+ Tconv and CX tissue-resident CD69+CD103+ Tconv, reported to be implicated in HIV acquisition risk and replication. Many soluble immune factor differences in the CVT further support that BV elicits diverse and complex CVT immune alterations. Our comprehensive analysis expands on potential immunological mechanisms that may underlie the adverse health outcomes associated with BV including increased HIV susceptibility.

The human vaginal microbiota: from clinical medicine to models to mechanisms

The composition of the vaginal microbiota is linked to numerous reproductive health problems, including increased susceptibility to infection, pregnancy complications, and impaired vaginal tissue repair; however, the mechanisms contributing to these adverse outcomes are not yet fully defined. In this review, we highlight recent clinical advancements associating vaginal microbiome composition and function with health outcomes. Subsequently, we provide a summary of emerging models employed to identify microbe-microbe interactions contributing to vaginal health, including metagenomic sequencing, multi-omics approaches, and advances in vaginal microbiota cultivation. Last, we review new in vitro, ex vivo, and in vivo models, such as organoids and humanized microbiota murine models, used to define and mechanistically explore host-microbe interactions at the vaginal mucosa.