Biology subjects

Ravel, J.

Publications and source records attributed to Ravel, J..

At least 19 recordsLinked to original sources

bioRxiv2026

Exposure to Antibiotics Modifies the Immune Profiles of Bacterial Extracellular Vesicles from Common Vaginal Anaerobes

BackgroundThe female lower reproductive tract harbors a complex microbiome that plays a critical role in reproductive health. A vaginal microbiome dominated by Lactobacillus crispatus (LC; Community State Type (CST) I) supports vaginal health, whereas a microbiome enriched with anaerobic species, such as Gardnerella vaginalis (GV) and Mobiluncus mulieris (MM) (CST IV) is linked to bacterial vaginosis (BV) and adverse outcomes, including sexually transmitted infections, infertility, and preterm birth. Although antibiotics such as metronidazole and clindamycin are commonly prescribed to treat BV, recurrence rates remain high, and the impact of these treatments on bacterial extracellular vesicles (bEVs), critical mediators of host-microbe interactions, is poorly understood. ResultWe investigated how antibiotic treatment at a dose below minimum inhibitory concentration alters the production and immunomodulatory function of bEVs derived from GV, MM, and LC. Using nanoparticle tracking analysis, cytokine profiling, and TLR pathway analyses, we found that antibiotic treatment significantly enhanced the inflammatory properties of bEVs in a species- and antibiotic-specific manner. Notably, bEVs from antibiotic-exposed GV and MM cultures induced elevated cytokine responses in epithelial and immune cells, primarily through TLR2 activation for GV bEVs, and through both TLR2 and TLR5 activation for MM bEVs. While LC bEVs are typically non-inflammatory, exposure to metronidazole, even at a lower dose than what is used clinically, rendered them immunostimulatory, suggesting a potential unintended proinflammatory consequence of treatment on beneficial microbes. We also detected bEVs in human vaginal swabs, including vaginolysin-positive bEVs, even in CST I microbiomes, indicating that low-abundance microbes, including pathogens, remain transcriptionally active. ConclusionsThese findings suggest that antibiotics not only reduce microbial load but also reshape bacterial communication via bEVs, potentially contributing to inflammation, epithelial barrier disruption, persistent dysbiosis, and recurrent infections. This work underscores the need for precision antimicrobial strategies that eliminate pathogens while preserving beneficial bacteria and their functional bEVs. Future therapies may benefit from considering the ecosystem-wide effects of antibiotics on the vaginal microbiome and its bEV-mediated signaling network.

microbiology↗

bioRxiv2025

Vitamin B2 Production by Vaginal Lactobacilli Promotes Symbiosis

The human vaginal microbiome, particularly with lactobacilli as the main inhabitants, plays a key role in maintaining womens health. While lactic acid-mediated pathogen exclusion is well known, broader metabolic functions of vaginal lactobacilli remain underexplored. In this study, we analyzed the vaginal microbiome and metabolome of 258 healthy women from the Isala program. Using targeted metabolomics analysis, we detected a high prevalence with strong interpersonal differences of most B-vitamins, their precursors, and vitamin A in the vaginal microenvironment. Riboflavin (B2) and biotin (B7) showed strong associations with Lactobacillus crispatus and Limosilactobacillus sp. Comparative genomics, phenotypic assays, and in vivo metatranscriptomic data (VIRGO2) collectively confirmed riboflavin biosynthesis by these taxa. Using a riboflavin overproducing Lim. reuteri as a functional model, we showed that microbially derived riboflavin and its pathway intermediates are transported across the vaginal epithelium and modulate host redox balance, cytokine production, and activation of mucosal-associated invariant T (MAIT) cells via induction of MR1 (Major histocompatibility complex, class I-related protein receptor), revealing a potential immunometabolic interface between the vaginal microbiota and its host.

microbiology↗

bioRxiv2025

kSanity: A k-mer based application forprecision bacterial strain detection andquantification

MotivationAccurate detection and quantification of bacterial strains in clinical samples is necessary to measure their colonization and persistence. Past methods to achieve this relied either on strain-specific qPCR assays, or shotgun metagenomic read mapping approaches. The resident microbial community is a major source of interference in both assays because it can contain conspecific strains bearing similarity to the focal strain(s). ResultsWe present kSanity, a k-mer based application for the detection and quantification of targeted bacterial strains in shotgun metagenomic data. Because kSanity uses exact string matches between the reads and reference, it is less sensitive to interference by conspecific strains. We test the performance of kSanity using a combination of in silico spike-in experiments, and in vivo observational data. Our results demonstrate that kSanity provides precise and accurate quantification of targeted bacterial strains, even when they are present at low sequence coverage in the metagenome. Availability and implementationkSanity is available at: https://github.com/ravel-lab/kSanity

bioinformatics↗

bioRxiv2025

A Microphysiologic Model of the Cervical Epithelium Recapitulates Microbial, Immunologic, and Pathogenic Properties of Sexually Transmitted Infections

Sexually transmitted infections (STIs) of the cervicovaginal mucosa are among the most common global infections. Clinical studies have revealed that susceptibility to STIs and the subsequent host responses they elicit are frequently associated with vaginal microbiota compositions that facilitate infection. Current monolayer cell culture and animal models fail to reproduce the multilevel complexity required to investigate these relationships simultaneously and/or with sufficient physiological relevance. To address this limitation, we have developed a microphysiologic system (MPS) that models human cervical tissue, its microbiota, and is susceptible to infection by two prominent genital pathogens, Chlamydia trachomatis and Neisseria gonorrhoeae. Significantly, this MPS platform recapitulates essential dynamic, polymicrobial, immune, and pathogenic features of chlamydial and gonococcal infections as they occur in humans. The lowcost MPS device requires no specialized equipment or specific expertise and was experimentally validated for both chlamydial and gonococcal infections across multiple nonengineering, remotely located laboratories, demonstrating its transferability and reproducibility. The MPS platform described herein provides a novel tool for expanded research into genital infections in a reconstituted system that closely mimics the cervical epithelium, a significant advance over existing models.

bioengineering↗

bioRxiv2025

The vaginal microbiota, symptoms, and local immune correlates in transmasculine individuals using sustained testosterone therapy

Transmasculine individuals (assigned female at birth, masculine gender identity, TM) may use gender-affirming testosterone therapy, and some TM report adverse genital symptoms during treatment. In cis women, the vaginal microbiota is a key determinant of reproductive and sexual health outcomes; Lactobacillus-dominant communities are considered optimal, while more even, diverse, Lactobacillus-depleted microbiota are considered non-optimal. Prior studies suggest Lactobacillus deficiency in TM vaginal microbiota, but associations with symptoms and immune markers remain unclear. We launched the TransBiota study to characterize the TM vaginal microbiota, soluble mediators of local inflammation (SMI), and self-reported symptoms over three weeks. Fewer than 10% of TM possessed Lactobacillus-dominant microbiota, and most exhibited more diverse, Lactobacillus-depleted microbiota. We identified 11 vaginal microbiota community state types (tmCSTs), with Lactobacillus-dominant tmCSTs unexpectedly linked to abnormal odor and elevated IL-1. These findings indicate that Lactobacillus dominance may no longer be an optimal state for TM during gender-affirming testosterone therapy and change in clinical management is needed.

microbiology↗

bioRxiv2025

The Neovaginal Microbiota, Symptoms, and Local Immune Correlates in Transfeminine Individuals with Penile Inversion Vaginoplasty

Transfeminine people (assigned male at birth) often undergo penile inversion vaginoplasty to create vulva, a clitoris and a vaginal canal (referred to as a neovagina). After vaginoplasty, transfeminine people frequently experience gynecological concerns but their etiology is unknown due to a lack of knowledge of the neovaginal microenvironment. We characterized neovaginal microbiota and cytokines in 47 transfeminine participants. Participants self-reported sexual behaviors and symptoms, enabling correlation with bacterial (16S rRNA) and immune profiles. Four distinct clusters of co-occurring bacteria with unique immune profiles were identified. One cluster, which included Fastidiosipila, Ezakiella, and Murdochiella, was abundant, stable, and correlated with lower cytokines. Conversely, another cluster containing Howardella, Parvimonas, Fusobacterium, and Lawsonella was linked to higher cytokines. Although Lactobacillus was detected, Lactobacillus-dominance was rare. These findings underscore the need for evidence-based clinical guidelines tailored to transfeminine gynecologic care, emphasizing the vital role of the neovaginal microbiome in symptom management and sexual health.

microbiology↗

bioRxiv2025

Temporal Dynamics of the Vaginal Microbiome and Host Immune Markers Before, During, and After Metronidazole Treatment for Bacterial Vaginosis

This study analyzed metagenomic and immune marker profiles of seven individuals before, during, and after a 7-day course of metronidazole treatment for bacterial vaginosis (BV). Treatment reduced BV-associated bacteria and immune marker levels, with distinct early (days 1-4) and late (days 5-7) phases. Post-treatment, variability in microbial and immune marker profiles demonstrated a rapid resurgence of certain BV associated bacteria, highlighting the need for additional strategies like probiotics to maintain a healthy vaginal microbiome. The study found significant host and microbial influences on immune response variance, with IP-10 and sEcad highly correlated with the vaginal microbiome. The findings identify optimal timing for administering live biotherapeutics to restore D-lactic acid-producing Lactobacillus species dominance and underscore the complexity of BV infection and treatment response among different people. ImportanceBacterial vaginosis (BV), a common condition associated with an increased risk of preterm birth and sexually transmitted infections among others, is characterized by a dysbiotic vaginal microbiome associated with dominance of a diverse assortment of anaerobic bacterial species. Metronidazole is the first-line treatment recommended by the CDC for BV when patients report symptoms. Despite treatment, BV recurrence is common. There is limited data regarding the effects of oral metronidazole on the vaginal microbiome starting at initiation of treatment as most studies have compared measurements taken before and after treatment completion. This study utilized metagenomic sequencing, pan-bacterial qPCR, and immune marker measurements to analyze the longitudinal dynamics of the vaginal microbiome and host immune response before, during and after metronidazole treatment.

microbiology↗

bioRxiv2025

VIRGO2: Unveiling the Functional and Ecological Complexity of the Vaginal Microbiome with an Enhanced Non-Redundant Gene Catalog

Despite the importance of the cervicovaginal microbiome, the mechanisms that govern its composition and drive its impact on host physiology remain poorly understood. This study expands our understanding of the function and ecology of the vaginal microbiome using VIRGO2, an enhanced non-redundant gene catalog comprising over 1.7 million well-annotated genes from body-site specific microbes and viruses. Analyses using VIRGO2 revealed novel insights, including the identification of previously uncharacterized vaginal bacteria, features of the vaginal mycobiome and phageome, and differential expression of bacterial carbohydrate catabolic genes. Constructed from over 2,500 metagenomes and 4,000 bacterial genomes, VIRGO2 broadens geographic representation and microbial diversity compared to its predecessor. This updated catalog enables more precise profiling of taxonomic and functional composition from metagenomic and metatranscriptomic datasets. VIRGO2 is a critical resource for integrative analyses of vaginal microbial communities and their interactions with host tissues, thereby enhancing our mechanistic understanding of vaginal health and disease.

microbiology↗

bioRxiv2024

Resource landscape shapes the composition and stability of the human vaginal microbiota

The vaginal microbiota is associated with the health of women and newborns alike. Despite its comparatively simple composition relative to other human microbiota systems, the mechanisms underpinning the dynamics and stability of vaginal microbial communities remain elusive. A crucial, yet so far underexplored, aspect of vaginal microbiota ecology is the role played by nutritional resources. Glycogen and its derivatives, produced by vaginal epithelia, are accessible to all bacterial constituents of the microbiota. Concurrently, free sialic acid and fucose offer supplementary nutritional resources to bacterial strains capable of cleaving them from glycans, which are structurally integral to mucus. Notably, bacteria adept at sialic acid exploitation are often correlated with adverse clinical outcomes and are frequently implicated in bacterial vaginosis (BV). In this study, we introduce a novel mathematical model tailored to human vaginal microbiota dynamics to explore the interactions between bacteria and their respective nutritional landscape. Our resource-based model examines the impact of the relative availability of glycogen derivatives (accessible to all bacterial species) and sialic acid (exclusive to some BV-associated bacteria) on the composition of the vaginal microbiota. Our findings elucidate that the success of BV-associated bacteria is intricately linked to their exclusive access to specific nutritional resources. This private access fortifies communities dominated by BV-associated bacteria, rendering them resilient to compositional transitions. We empirically corroborate our model prediction with longitudinal clinical data on microbiota composition and previously unpublished metabolomic profiles obtained from a North American cohort. The insights gleaned from this study shed light on potential pathways for BV prevention and treatment. Significance statementThe vaginal microbiota has a notable impact on womens health at various stages of life, namely puberty, infection protection, sexual health, fertility, pregnancy, and menopausal changes. At present, most non-anti-microbial products developed to mitigate adverse vaginal symptoms emphasise competitive interactions through acids (boric or lactic acid) or probiotics as a means to "rebalance" microbiota communities. Despite recent advances in profiling the composition of vaginal microbiota communities, there remains a major gap in our mechanistic understanding of how to maintain or reinstate a resilient Lactobacillus-dominated microbiota that improves vaginal health and outcomes. This study explores the role of nutritional resources in the vaginal microbiota by introducing a mathematical model that analyses how access to specific nutrients like glycogen derivatives and sialic acid affects the balance of bacterial vaginosis (BV) and non-BV-associated bacteria. Our findings, supported by original cohort-derived microbiological and metabolomics data, demonstrate that exclusive access to these nutrients is linked to the dominance and resilience of BV-associated bacteria, providing new insights for BV prevention and treatment.

microbiology↗

bioRxiv2024

Evaluating the Analytical Performance of Direct-to-Consumer Gut Microbiome Testing Services

Consumer interest in personal microbiome health has given rise to numerous direct-to-consumer (DTC) microbiome testing services despite questions regarding their analytical and clinical validity, and consumer safety. These tests straddle the line between more strictly regulated medical devices and minimally regulated general health and wellness products; a distinction that may not be readily apparent to consumers. To assess the current state of the industry, we evaluated the performance of seven commercial DTC gut microbiome testing services using a standardized NIST - developed human fecal material. Our results reveal major discrepancies, both within and across the different service providers. Significantly, we found variability between providers was on the same scale as biological variability between different donors. We attribute the observed differences to methodological variability and lack of sufficient quality control. Additionally, we highlight that analytical performance is a prerequisite for making sound clinical recommendations. Our results demonstrate the need for standards to ensure analytical validity and regulatory oversight to ensure patient safety.

microbiology↗

bioRxiv2024

SpeciateIT and vSpeciateDB: Novel, fast and accurate per sequence 16S rRNA gene taxonomic classification of vaginal microbiota

Clustering of sequences into operational taxonomic units (OTUs) and denoising methods are a mainstream stopgap to taxonomically classifying large numbers of 16S rRNA gene sequences. We developed speciateIT, a novel taxonomic classification tool which rapidly and accurately classifies individual amplicon sequences (https://github.com/Ravel-Laboratory/speciateIT). Environment-specific reference databases generally yield optimal taxonomic assignment. To this end, we also present vSpeciateDB, a custom reference database for the taxonomic classification of 16S rRNA gene amplicon sequences from vaginal microbiota. We show that speciateIT requires minimal computational resources relative to other algorithms and, when combined with vSpeciateDB, affords accurate species level classification in an environment-specific manner. ImportanceHerein, two resources with new and practical importance are described. The novel classification algorithm, speciateIT, is based on 7th order Markov chain models and allows for fast and accurate per-sequence taxonomic assignments (as little as 10 min for 107 sequences). vSpeciateDB, a meticulously tailored reference database, stands as a vital and pragmatic contribution. Its significance lies in the superiority of this environment-specific database to provide more species-resolution over its universal counterparts.

bioinformatics↗

bioRxiv2024

Inferring stability and persistence in the vaginal microbiome: A stochastic model of ecological dynamics

The vaginal microbiome is dynamic, yet the ecological and stochastic forces shaping its stability and persistence remain poorly understood. We developed a multi-species stochastic population model to analyze time-series data from 135 individuals sampled daily over 70 days, integrating ecological theory with microbial dynamics. Our framework explicitly incorporates stochasticity, ecological feedback, and sampling error to quantify community stability. We show that intra- and inter-species interactions and environmental fluctuations critically shape microbial population trajectories. This approach enabled the estimation of species competition coefficients and the identification of distinct stability regimes across individuals. We also introduce a Risk Prediction Monitoring (RPM) tool to track persistence probabilities of key taxa, particularly Lactobacillus spp., mirroring extinction risk models in conservation biology. Our findings challenge static "healthy" vs. "dysbiotic" categorizations and offer a quantitative framework for assessing microbiome resilience. This has direct implications for microbiome-targeted therapies aimed at promoting ecological stability in vaginal bacterial communities.

ecology↗

bioRxiv2023

High-resolution functional description of vaginal microbiomes in health and disease

BackgroundA Lactobacillus-dominated vaginal microbiome provides the first line of defense against numerous adverse genital tract health outcomes. However, there is limited understanding of the mechanisms by which the vaginal microbiome modulates protection, as prior work mostly described its composition through morphologic assessment and marker gene sequencing methods that do not capture functional information. To address this limitation, we developed metagenomic community state types (mgCSTs) which uses metagenomic sequences to describe and define vaginal microbiomes based on both composition and function. ResultsMgCSTs are categories of microbiomes classified using taxonomy and the functional potential encoded in their metagenomes. MgCSTs reflect unique combinations of metagenomic subspecies (mgSs), which are assemblages of bacterial strains of the same species, within a microbiome. We demonstrate that mgCSTs are associated with demographics such as age and race, as well as vaginal pH and Gram stain assessment of vaginal smears. Importantly, these associations varied between mgCSTs predominated by the same bacterial species. A subset of mgCSTs, including three of the six predominated by Gardnerella mgSs, as well as a mgSs of L. iners, were associated with a greater likelihood of Amsel bacterial vaginosis diagnosis. This L. iners mgSs, among other functional features, encoded enhanced genetic capabilities for epithelial cell attachment that could facilitate cytotoxin-mediated cell lysis. Finally, we report a mgSs and mgCST classifier as an easily applied, standardized method for use by the microbiome research community. ConclusionsMgCSTs are a novel and easily implemented approach to reducing the dimension of complex metagenomic datasets, while maintaining their functional uniqueness. MgCSTs enable investigation of multiple strains of the same species and the functional diversity in that species. Future investigations of functional diversity may be key to unraveling the pathways by which the vaginal microbiome modulates protection to the genital tract. Importantly, our findings support the hypothesis that functional differences between vaginal microbiomes, including those that may look compositionally similar, are critical considerations in vaginal health. Ultimately, mgCSTs may lead to novel hypotheses concerning the role of the vaginal microbiome in promoting health and disease, and identify targets for novel prognostic, diagnostic, and therapeutic strategies to improve womens genital health.

genomics↗

bioRxiv2023

The vaginal microbiota of pregnant women varies with gestational age, maternal age, and parity

The composition of the vaginal microbiota is heavily influenced by pregnancy and may factor into pregnancy complications, including spontaneous preterm birth. However, results among studies have been inconsistent, due in part to variation in sample sizes and ethnicity. Thus an association between the vaginal microbiota and preterm labor continues to be debated. Yet, before assessing associations between the composition of the vaginal microbiota and preterm labor, a robust and in-depth characterization of the vaginal microbiota throughout pregnancy in the specific study population under investigation is required. Herein, we report a large longitudinal study (N = 474 women, 1862 vaginal samples) of a primarily African-American cohort- which experiences a relatively high rate of pregnancy complications - evaluating associations between individual identity, gestational age, and other maternal characteristics with the composition of the vaginal microbiota throughout gestation resulting in term delivery. The primary factors influencing the composition of the vaginal microbiota in pregnancy are individual identity and gestational age at sampling. Secondary factors are maternal age, parity, obesity, and self-reported Cannabis use. The principal pattern across gestation is for the vaginal microbiota to remain or transition to a state of Lactobacillus dominance. This pattern can be mitigated by maternal parity and obesity. Regardless, network analyses reveal dynamic associations among specific bacterial taxa within the vaginal ecosystem, which shift throughout the course of pregnancy. This study provides a robust foundational understanding of the vaginal microbiota in pregnancy among African-Americans, in particular, and sets the stage for further investigation of this microbiota in obstetrical disease. IMPORTANCEThere is debate regarding links between the vaginal microbiota and pregnancy complications, especially spontaneous preterm birth. Inconsistencies in results among studies are likely due to differences in sample sizes and cohort ethnicity. Ethnicity is a complicating factor because, although all bacterial taxa commonly inhabiting the vagina are present among all ethnicities, the frequencies of these taxa vary among ethnicities. Therefore, an in-depth characterization of the vaginal microbiota throughout pregnancy in the specific study population under investigation is required prior to evaluating associations between the vaginal microbiota and obstetrical disease. This initial investigation is a large longitudinal study of the vaginal microbiota throughout gestation resulting in a term delivery in a primarily African-American cohort, a population that experiences disproportionally negative maternal-fetal health outcomes. It establishes the magnitude of associations between maternal characteristics, such as age, parity, BMI, and self-reported Cannabis use, on the vaginal microbiota in pregnancy.

microbiology↗

bioRxiv2022

Highly specialized carbohydrate metabolism capability in Bifidobacterium strain associated with intestinal barrier maturation in early preterm infants

"Leaky gut", or high intestinal barrier permeability, is common in preterm newborns. The role of microbiota in this process remains largely uncharacterized. We employed both short- and long-read sequencing of the 16S rRNA gene and metagenomes to characterize the intestinal microbiome of a longitudinal cohort of 113 preterm infants born between 240/7-326/7 weeks of gestation. Enabled by enhanced taxonomic resolution, we found significantly increased abundance of Bifidobacterium breve and a diet rich in mothers breastmilk to be associated with intestinal barrier maturation during the first week of life. We combined these factors using genome- resolved metagenomics and identified a highly specialized genetic capability of the Bifidobacterium strains to assimilate human milk oligosaccharides and host-derived glycoproteins. Our study proposed mechanistic roles of breastmilk feeding and intestinal microbial colonization in postnatal intestinal barrier maturation; these observations are critical towards advancing therapeutics to prevent and treat hyperpermeable gut- associated conditions, including necrotizing enterocolitis. IMPORTANCEDespite improvements in neonatal intensive care, necrotizing enterocolitis (NEC) remains a leading cause of morbidity and mortality. "Leaky gut", or intestinal barrier immaturity with elevated intestinal permeability, is the proximate cause of susceptibility to NEC. Early detection and intervention to prevent leaky gut in "at-risk" preterm neonates is critical to lower the risk for potentially life-threatening complications like NEC. However, the complex interactions between the developing gut microbial community, nutrition, and intestinal barrier function, remain largely uncharacterized. In this study, we revealed the critical role of sufficient breastmilk feeding volume and specialized carbohydrate metabolism capability of Bifidobacterium in coordinated postnatal improvement of intestinal barrier. Determining the clinical and microbial biomarkers that drive the intestinal developmental disparity will inform early detection and novel therapeutic strategies to promote appropriate intestinal barrier maturation, prevent NEC and other adverse health conditions in preterm infants.

microbiology↗

bioRxiv2022

Persistence and in vivo evolution of vaginal bacterial strains over a multi-year time period

It is not clear if the bacterial strains which comprise our microbiota are mostly long-term colonizers or transient residents. Studies have demonstrated decades long persistence of bacterial strains within the gut, but persistence at other body sites has yet to be determined. The vaginal microbiota (VMB) is often dominated by Lactobacillus, although it is also commonly comprised of a more diverse set of other facultative and obligate anaerobes. Longitudinal studies have demonstrated that these communities can be stable over several menstrual cycles or can fluctuate temporally in species composition. We sought to determine whether the bacterial strains which comprise the VMB were capable of persisting over longer time-periods. We performed shotgun metagenomics on paired samples from 10 participants collected 1 and 2 years apart. The resulting sequences were de novo assembled and binned into high-quality metagenome assembled genomes. Persistent strains were identified based on the sequence similarity between the genomes present at the two timepoints and were found in the VMB of six of the participants, three of which had multiple. The VMB of the remaining four participants was similar in species composition at the two timepoints but was comprised of different strains. For the persistent strains, we were able to identify the mutations which fixed in the populations over the observed time period, giving insight into the evolution of these bacteria. These results indicate that bacterial strains can persist in the vagina for extended periods of time, providing an opportunity for them to evolve in the host microenvironment. ImportanceThe persistence of strains within the vaginal microbiota has not yet been characterized. Should these strains be capable of persisting for extended periods of time, they could evolve within their host in response to selective pressures exerted by the host or by other members of the community. Here, we present preliminary findings which demonstrate that bacterial strains can persist in the vagina for at least one year and evolve over time. In several cases, multiple strains persisted together in a community, indicating that co-evolution between bacterial strains could occur in the vagina. Our observations motivate future studies which collect samples from more participants, at more timepoints and over even longer periods of time. Understanding which strains persist, what factors drive their persistence, and what selective pressures they face will inform the development and delivery of rationally designed live biotherapeutics for the vagina.

microbiology↗

bioRxiv2022

Vaginal microbiome-host interactions modeled in a human vagina-on-a-chip

BackgroundA dominance of non-iners Lactobacillus species in the vaginal microbiome is optimal and strongly associated with gynecological and obstetric health, while the presence of diverse obligate or facultative anaerobic bacteria and a paucity in Lactobacillus species, similar to communities found in bacterial vaginosis (BV), is considered non-optimal and associated with adverse health outcomes. Various therapeutic strategies are being explored to modulate the composition of the vaginal microbiome; however, there is no human model that faithfully reproduces the vaginal epithelial microenvironment for preclinical validation of potential therapeutics or testing hypotheses about vaginal epithelium-microbiome interactions. ResultsHere, we describe an organ-on-a-chip (Organ Chip) microfluidic culture model of the human vaginal mucosa (Vagina Chip) that is lined by hormone-sensitive, primary vaginal epithelium interfaced with underlying stromal fibroblasts, which sustains a low physiological oxygen concentration in the epithelial lumen. We show that the Vagina Chip can be used to assess colonization by optimal L. crispatus consortia as well as non-optimal Gardnerella vaginalis-containing consortia, and to measure associated host innate immune responses. Co-culture of the L. crispatus consortia was accompanied by maintenance of epithelial cell viability, accumulation of D- and L-lactic acid, maintenance of a physiologically relevant low pH, and down regulation of proinflammatory cytokines. In contrast, co-culture of G. vaginalis-containing consortia in the Vagina Chip resulted in epithelial cell injury, a rise in pH, and upregulation of proinflammatory cytokines. ConclusionThis study demonstrates the potential of applying human Organ Chip technology to create a preclinical model of the human vaginal mucosa that can be used to better understand interactions between the vaginal microbiome and host tissues, as well as to evaluate the safety and efficacy of live biotherapeutics products.

microbiology↗

bioRxiv2021

Sub-communities of the vaginal ecosystem in pregnant and non-pregnant women.

Diverse and non-Lactobacillus-dominated vaginal microbial communities are associated with adverse health outcomes such as preterm birth and the acquisition of sexually transmitted infections. Despite the importance of recognizing and understanding the key risk-associated features of these communities, their heterogeneous structure and properties remain ill-defined. Clustering approaches are commonly used to characterize vaginal communities, but they lack sensitivity and robustness in resolving substructures and revealing transitions between potential sub-communities. Here, we address this need with an approach based on mixed membership topic models, using longitudinal data from cohorts of pregnant and non-pregnant study participants. We identify several non-Lactobacillus-dominated sub-communities common to both cohorts and independent of reproductive status. In non-pregnant individuals, we find that the menstrual cycle modulates transitions between and within sub-communities. In addition, a specific non-Lactobacillus-dominated sub-community, which was associated with preterm delivery in pregnant participants, was also more common during menses, a time of elevated vaginal inflammation in non-pregnant participants. Overall, our analyses based on mixed membership models reveal substructures of vaginal ecosystems which may have important clinical and biological associations.

microbiology↗