Lactic acid enhances vaginal epithelial barrier integrity and ameliorates inflammatory effects of dysbiotic short chain fatty acids and HIV-1

Influence of cervicovaginal microbiota on Chlamydia trachomatis infection dynamics

The cervicovaginal microbiome (CVM) is increasingly being considered as an important aspect of women's health, particularly in relation to the risk and progression of sexually transmitted infections (STIs). CVM composition varies significantly between individuals and is shaped by factors including diet, age, environmental exposures, and lifestyle. Understanding these influences may shed light on how microbial imbalances contribute to infection susceptibility and the development of reproductive health disorders. Five distinct community state types (CSTs) classify common CVM compositions. Most CSTs (I, II, III, V) are characterized by a dominant Lactobacillus species and are associated with better or neutral reproductive health, including reduced coincident detection of STIs such as Chlamydia trachomatis. In contrast, CST IV is composed of diverse, predominantly anaerobic, microbial species and is associated with CVM dysbiosis, bacterial vaginosis, and a heightened risk of STI acquisition. This review examines the complex interplay between the CVM, C. trachomatis infection, and host immune responses, highlighting the role of metabolites such as short-chain and long-chain fatty acids, indole, and iron in modulating pathogen survival and host defenses. Additionally, the impacts of CVM composition on C. trachomatis persistence, ascension, and clearance are discussed, alongside co-infection dynamics with pathogens like Neisseria gonorrhoeae and Mycoplasma genitalium.

Use of an Ethinyl Estradiol/Etonogestrel Vaginal Ring Alters Vaginal Microbial Communities in Women With HIV

BACKGROUND

Human immunodeficiency virus 1 (HIV-1) antiretroviral therapy (ART) alters hormonal contraceptive levels delivered via intravaginal ring (IVR) in a regimen-specific manner. We explored the role of the IVR on vaginal microbial communities, vaginal short chain fatty acids (SCFAs), vaginal HIV shedding, and the effect of vaginal microbes on hormone concentrations in cisgender women with HIV (WWH).

METHODS

Vaginal microbes were assessed by 16S RNA sequencing of weekly vaginal swabs, vaginal SCFA by mass spectrometry, HIV-1 shedding by nucleic acid amplification on vaginal aspirates, and bacterial vaginosis by Nugent scoring from 74 participants receiving an etonogestrel/ethinyl estradiol (ENG/EE) intravaginal ring while on no ART (n = 25), efavirenz-based ART (n = 25), or atazanavir-based ART (n = 24).

RESULTS

At baseline, microbial communities of the 64 substudy eligible participants robustly classified as Lactobacillus crispatus-dominant (n = 8), Lactobacillus gasseri-dominant (n = 2), Lactobacillus iners-dominant (n = 17), or mixed anaerobic communities (n = 37). During IVR therapy, there was an increased probability of Lactobacillus-dominant community state types (CSTs) (odds ratio = 1.61, P = .04). Vaginal CSTs were associated with Nugent scores. Bacterial vaginosis-associated bacteria were associated with significantly higher and L. iners with lower Nugent scores (all P adjusted <.1). Lactic acid levels were correlated with the relative abundance of Lactobacillus species (r2 = 0.574; P < .001). Vaginal shedding of HIV-1 was less common in women with L. crispatus-dominant microbiomes (P = .04). Mixed anaerobic vaginal communities modulated EE concentrations in a regimen-specific manner.

CONCLUSIONS

Combined ENG/EE IVR therapy was associated with an increase in Lactobacillus-dominant vaginal microbial communities in WWH and may benefit those with bacterial vaginosis. EE levels were altered by the vaginal microbiota.

Are We Able to Optimize Outcomes and Predict Complications in Pelvic Floor Surgery With a Better Understanding of Hormonal, Microbial and Other Factors? A Report From the ICI-RS 2024

INTRODUCTION

Pelvic organ prolapse (POP) is a common condition, affecting women worldwide and is known to have a significant impact on Health Related Quality of Life (HRQoL). Although there are various treatment options available, including pelvic floor muscle training and support pessaries, many women opt for or require surgery, with a lifetime risk of needing surgery of 12%-19%. As with any operation, this does not come without its complications and the reoperation rate following POP surgery is up to 36%. This International Consultation on Incontinence-Research Society (ICI-RS) report aims to look at the different factors which may play a role in objective and subjective outcomes following pelvic floor surgery and to summarize the evidence and uncertainties regarding prediction of POP surgical outcomes, how to optimize them and the tools available to predict them. Research question proposals to further this field have been highlighted.

METHODS

At ICI-RS 2024, the evidence for predicting the outcomes from POP surgery and methods to optimize outcomes were discussed and presented in this paper.

RESULTS

There are many reasons why POP surgery may fail, such as variations in lifestyle and occupation, persistent constipation, failure in the perineal body, connective tissue types or the shape of the pelvis. There may also be inherent conditions of the vagina, such as hormonal or microbial features. The literature lacks evidence about the potential use of advanced statistical modeling or supervised machine learning in the development of management plans for patients with POP. Furthermore, future research is needed to determine the role of UDS in the preoperative evaluation of POP patients.

CONCLUSIONS

High-quality powered studies are required to assess optimization for long-term outcomes of pelvic surgery and then, once these are well established, and possible interventions are elucidated, prediction modeling can have a real impact clinically.

Innate lymphoid cells in HIV pathogenesis and in the human female genital tract

PURPOSE OF REVIEW

Women are underrepresented in HIV infection and prevention research despite making up half of people living with HIV. The female genital tract (FGT) serves as a primary site of HIV acquisition, but gaps in knowledge remain regarding protective innate immune mechanisms. Innate lymphoid cells are tissue-resident cells involved in mucosal barrier maintenance and protection, and innate lymphoid cells (ILCs) are altered during chronic HIV infection. However, ILCs role in mucosal HIV pathogenesis is unclear and they are poorly characterized in the FGT.

RECENT FINDINGS

Human ILCs differ from their mouse counterparts and plastically adjust to their tissue of residency. Human ILC characterization is difficult due to tissue-specific adaptations and transition between subsets. While evidence for ILC involvement in antiviral activity and barrier maintenance is provided in mouse models, human ILC role in mucosal immunity remain understudied, particularly in the FGT. In chronic HIV/simian immunodeficiency virus (SIV) infection, ILCs are altered in a tissue-specific manner, and SIV models indicate potential for antiviral responses.

SUMMARY

ILCs are tissue-resident plastic cells that provide barrier protection at mucosal surfaces and display antiviral capacity. Considering that HIV is primarily transmitted through mucosal exposure, more research is needed to understand ILC contribution to HIV pathogenesis in human mucosal surfaces relevant for HIV acquisition.

Early prediction of preeclampsia using the first trimester vaginal microbiome

Preeclampsia is a severe obstetrical syndrome which contributes to 10-15% of all maternal deaths. Although the mechanisms underlying systemic damage in preeclampsia-such as impaired placentation, endothelial dysfunction, and immune dysregulation-are well studied, the initial triggers of the condition remain largely unknown. Furthermore, although the pathogenesis of preeclampsia begins early in pregnancy, there are no early diagnostics for this life-threatening syndrome, which is typically diagnosed much later, after systemic damage has already manifested. Here, we performed deep metagenomic sequencing and multiplex immunoassays of vaginal samples collected during the first trimester from 124 pregnant individuals, including 62 who developed preeclampsia with severe features. We identified multiple significant associations between vaginal immune factors, microbes, clinical factors, and the early pathogenesis of preeclampsia. These associations vary with BMI, and stratification revealed strong associations between preeclampsia and Bifidobacterium spp., Prevotella timonensis, and Sneathia vaginalis. Finally, we developed machine learning models that predict the development of preeclampsia using this first trimester data, collected ~5.7 months prior to clinical diagnosis, with an auROC of 0.78. We validated our models using data from an independent cohort (MOMS-PI), achieving an auROC of 0.80. Our findings highlight robust associations among the vaginal microbiome, local host immunity, and early pathogenic processes of preeclampsia, paving the way for early detection, prevention and intervention for this devastating condition.

G. vaginalis increases HSV-2 infection by decreasing vaginal barrier integrity and increasing inflammation in vivo

Introduction

Clinically, a dysbiotic vaginal microbiota (VMB) colonized with anaerobic species such as Gardnerella vaginalis has been linked to increased susceptibility to viral sexually transmitted infections (STIs) such as Herpes Simplex Virus Type 2 (HSV-2). The mechanism is poorly understood due to the lack of small animal models.

Methods

Mice were inoculated with 107 CFU of the eubiotic bacteria Lactobacillus crispatus, the dysbiotic bacteria G. vaginalis, or PBS as a negative control every 48 h for ten days. On day ten, mice were inoculated with 105 PFU WT HSV-2 333 and survival, pathology, and viral titers were assessed. To elucidate changes in the vaginal microenvironment following bacterial inoculations, vaginal tissue and washes were collected following ten days of inoculations. To assess barrier integrity, tissue was fixed and stained for the barrier protein Desmoglein-1 (DSG-1). To evaluate the immune microenvironment, tissue was processed for flow cytometry to examine tissue-resident T cells and cytokine production by T cells. Vaginal washes were used for multiplex cytokine/chemokine analysis.

Results

G. vaginalis inoculated mice infected with HSV-2 had significantly decreased survival rates, increased pathology, and higher viral titers than PBS and L. crispatus inoculated mice. The vaginal epithelium of G. vaginalis inoculated mice showed decreased DSG-1 staining compared to other groups, indicating compromised barrier function. Decreased total numbers of CD4+ and CD8+ T cells expressing activated mucosal immune markers CD44, CD69, and CD103 were observed in the vaginal tract of G. vaginalis inoculated mice. They also showed increased proportions of T cells expressing inflammatory cytokines TNF-α and IFN-γ, while L. crispatus inoculated mice had increased proportions and absolute counts of T cells expressing the regulatory cytokine IL-10. In the multiplex assay, vaginal washes from G. vaginalis mice had increased inflammatory cytokines and chemokines compared to L. crispatus and PBS groups.

Discussion

These results suggest G. vaginalis inoculation may be increasing HSV-2 infection by disrupting the epithelial barrier, decreasing protective immune responses and increasing tissue inflammation in the vaginal tract.

Vaginal lactobacilli produce anti-inflammatory β-carboline compounds

The optimal vaginal microbiome is a Lactobacillus-dominant community. Apart from Lactobacillus iners, the presence of Lactobacillus species is associated with reduced vaginal inflammation and reduced levels of pro-inflammatory cytokines. Loss of Lactobacillus-dominance is associated with inflammatory conditions, such as bacterial vaginosis (BV). We have identified that Lactobacillus crispatus, a key vaginal bacterial species, produces a family of β-carboline compounds with anti-inflammatory activity. These compounds suppress nuclear factor κB (NF-κB) and interferon (IFN) signaling downstream of multiple pattern recognition receptors in primary human cells and significantly dampen type I IFN receptor (IFNAR) activation in monocytes. Topical application of an anti-inflammatory β-carboline compound, perlolyrine, was sufficient to significantly reduce vaginal inflammation in a mouse model of genital herpes infection. These compounds are enriched in cervicovaginal lavage (CVL) of healthy people compared with people with BV. This study identifies a family of compounds by which vaginal lactobacilli mediate host immune homeostasis and highlights a potential therapeutic avenue for vaginal inflammation.

Unravelling the vaginal microbiome, impact on health and disease

PURPOSE OF REVIEW

The vaginal microbiome has a fundamental role in supporting optimal vaginal, reproductive, and sexual health. Conversely, dysbiosis of the vaginal microbiome is linked to vaginal symptoms and adverse health outcomes. This review summarizes recent literature concerning the role of the vaginal microbiome in health and disease, with a focus on the most common vaginal dysbiosis, bacterial vaginosis.

RECENT FINDINGS

Molecular studies have expanded our understanding of the composition of the vaginal microbiome. Lactic acid-producing lactobacilli are an important component of host defences against pathogens, whereas a paucity of lactobacilli is associated with adverse sequelae. Bacterial vaginosis is characterized by low levels of lactobacilli and increased levels of nonoptimal anaerobes; however, the exact cause remains unclear. Furthermore, despite decades of research, bacterial vaginosis recurrence rates following standard treatment are unacceptably high. Strategies to improve bacterial vaginosis cure and promote an optimal lactobacilli-dominated vaginal microbiome are being investigated. Importantly, historical and emerging evidence supports the sexual transmission of bacterial vaginosis, which opens exciting opportunities for novel treatments that incorporate partners.

SUMMARY

A mechanistic and deeper understanding of the vaginal microbiome in health and disease is needed to inform ongoing development of therapeutics to improve bacterial vaginosis cure. Partner treatment holds promise for improving bacterial vaginosis cure.

The vaginal microbiome and HIV transmission dynamics

PURPOSE OF REVIEW

Among women, having a nonoptimal, highly diverse vaginal microbiome dominated by bacteria other than optimal Lactobacillus species such as L. crispatus or L. jensenii predicts HIV transmission. Reducing HIV acquisition among women requires a better understanding of the mechanisms through which the vaginal microbiome impacts HIV transmission dynamics and how to more effectively treat and intervene. Technological advancements are improving the ability of researchers to fully characterize interacting host-bacteria mechanisms. Consequently, the purpose of this review was to summarize the most innovative research on the vaginal microbiome and its role in HIV transmission in the past year.

RECENT FINDINGS

Studies combining multiomics, experimental, and translational approaches highlight the associations of a nonoptimal microbiome with maladaptive alterations in immune cell functioning, vaginal metabolites, host cell transcription, mucosal immunity, and epithelial barrier integrity. While there are multiple mechanisms proposed to increase HIV acquisition risk, there are virtually zero acceptable and effective treatments to improve the vaginal microbiome and immunity.

SUMMARY

Women-centered solutions to modify the vaginal microbiome and bacterial metabolites should continue to be explored as a mechanism to reduce HIV acquisition.

Protective Mechanisms of Vaginal Lactobacilli against Sexually Transmitted Viral Infections

The healthy cervicovaginal microbiota is dominated by various Lactobacillus species, which support a condition of eubiosis. Among their many functions, vaginal lactobacilli contribute to the maintenance of an acidic pH, produce antimicrobial compounds, and modulate the host immune response to protect against vaginal bacterial and fungal infections. Increasing evidence suggests that these beneficial bacteria may also confer protection against sexually transmitted infections (STIs) caused by viruses such as human papillomavirus (HPV), human immunodeficiency virus (HIV) and herpes simplex virus (HSV). Viral STIs pose a substantial public health burden globally, causing a range of infectious diseases with potentially severe consequences. Understanding the molecular mechanisms by which lactobacilli exert their protective effects against viral STIs is paramount for the development of novel preventive and therapeutic strategies. This review aims to provide more recent insights into the intricate interactions between lactobacilli and viral STIs, exploring their impact on the vaginal microenvironment, host immune response, viral infectivity and pathogenesis, and highlighting their potential implications for public health interventions and clinical management strategies.

Mechanisms of mucosal immunity at the female reproductive tract involved in defense against HIV infection

Human immunodeficiency virus-1 remains a major global health threat. Since the virus is often transmitted through sexual intercourse and women account for the majority of new infections within the most endemic regions, research on mucosal immunity at the female reproductive tract (FRT) is of paramount importance. At the FRT, there are intrinsic barriers to HIV-1 infection, such as epithelial cells and the microbiome, and immune cells of both the innate and adaptive arms are prepared to respond in case the virus overcomes the first line of defense. In this review, we discuss recent findings on FRT mucosal mechanisms of HIV-1 defense and highlight research gaps. While defense from HIV-1 infection at the FRT has been understudied, current and future research is essential to develop new therapeutics and vaccines that can protect this unique mucosal site from HIV-1.

Development of phenyllactic acid ionic liquids and evaluation of cytotoxicity to human cervical epithelial cells

Phenyllactic acid (PLA), is a naturally produced, broad-spectrum antimicrobial compound with activity against bacteria and fungi. PLA can be produced by a variety of lactic acid bacteria, including vaginal Lactobacillus species, which are healthy constituents of the vaginal microbiome with a protective role against invading pathogenic bacteria and/or fungi. Additionally, PLA has been shown to exhibit anti-inflammatory and immunomodulatory properties, overall indicating its therapeutic potential as an intravaginally delivered compound for modulation of the vaginal microbiome. However, PLA has low kinetic solubility in water. Hence, strategies to improve the solubility of PLA are necessary to facilitate its intravaginal delivery. Using biocompatible cations, choline and carnitine, we successfully transformed both d- and l-enantiomers of crystalline PLA into amorphous low-melting ionic liquids (ILs) with high water solubility. We further evaluated the in vitro cytotoxicity of PLA ILs to human cervical epithelial cells. Microscopic visualisation of cellular morphology using crystal violet staining and MTT cell proliferation assay revealed that PLA ILs result in minimal morphological changes and low cytotoxicity to human cervical epithelial cells. Overall, we successfully demonstrated that transforming PLA into ILs efficiently enhances its solubility in water and these formulations are not toxic to human epithelial cells. This investigation lays the groundwork for future testing of PLA ILs for their antimicrobial properties and metabolic activity within the cervicovaginal microenvironment.

Lactobacillus crispatus CCFM1339 Inhibits Vaginal Epithelial Barrier Injury Induced by Gardnerella vaginalis in Mice

The vaginal epithelial barrier, which integrates mechanical, immune, chemical, and microbial defenses, is pivotal in safeguarding against external pathogens and upholding the vaginal microecological equilibrium. Although the widely used metronidazole effectively curtails Gardnerella vaginalis, a key pathogen in bacterial vaginosis, it falls short in restoring the vaginal barrier or reducing recurrence rates. Our prior research highlighted Lactobacillus crispatus CCFM1339, a vaginally derived Lactobacillus strain, for its capacity to modulate the vaginal epithelial barrier. In cellular models, L. crispatus CCFM1339 fortified the integrity of the cellular monolayer, augmented cellular migration, and facilitated repair. Remarkably, in animal models, L. crispatus CCFM1339 substantially abated the secretion of the barrier disruption biomarker E-cadherin (from 101.45 to 82.90 pg/mL) and increased the anti-inflammatory cytokine IL-10 (35.18% vs. the model), consequently mitigating vaginal inflammation in mice. Immunological assays in vaginal tissues elucidated increased secretory IgA levels (from 405.56 to 740.62 ng/mL) and curtailed IL-17 gene expression. Moreover, L. crispatus CCFM1339 enhanced Lactobacilli abundance and attenuated Enterobacterium and Enterococcus within the vaginal microbiome, underscoring its potential in probiotic applications for vaginal barrier regulation.