Bacterial amylases enable glycogen degradation by the vaginal microbiome

Effects of Dietary Quality on Vaginal Microbiome Composition Throughout Pregnancy in a Multi-Ethnic Cohort

Background: Vaginal Lactobacillus predominance is associated with improved vaginal health and reduced pregnancy complications. Little is known about how dietary quality may improve vaginal microbial composition or about dietary interventions that may promote Lactobacillus abundance. To understand the host factors affecting vaginal microbiota during pregnancy in a multi-ethnic cohort in Hawai`i. We hypothesize that better diet quality improves vaginal microbial composition, as represented by Lactobacillus abundance and depletion of anaerobic organisms. Methods: We compared comprehensive diet quality, as measured by the Healthy Eating Index-2015 (HEI-2015), to taxonomic classifications of bacteria present within the vagina. Participants of the four predominant ethnic groups in Hawai'i (Japanese, Filipino, Non-Hispanic White and Native Hawaiian) completed Quantitative Food Frequency Questionnaires (QFFQs) and collected vaginal swabs during each trimester. 16s rRNA amplicon sequencing (V2-V9 regions) was performed on vaginal samples. HEI-2015 scores and macro- and micronutrient intake were compared with the predominant species present using the Mann-Whitney-U test, PERMANOVA, and the Pearson correlation coefficient. A mixed-effects logistics regression model was used to predict the depletion of Lactobacillus species while accounting for confounding demographic factors. Results: Matched, longitudinal data for 40 participants demonstrated three predominant Lactobacillus species: L. crispatus, L. iners, and L. gasseri, with another subset of samples with anaerobic abundance. (Primarily, Atopobium vaginae, Prevotella, and Gardnerella vaginalis.) Non-Hispanic White participants had lower amounts of Lactobacillus iners compared to other racial and ethnic groups. HEI scores correlated with the chao index and observed species number primarily in the first trimester (r = 0.25, p < 0.05). Greater carbohydrate intake was associated with a higher abundance of L. crispatus, while lower carbohydrate intake trended towards more L. iners (0.056) and anaerobic species. Conclusions: Increased carbohydrate consumption and improved diet quality may be associated with beneficial vaginal microbial composition in pregnancy.

Prevotella timonensis degrades the vaginal epithelial glycocalyx through high fucosidase and sialidase activities

Bacterial vaginosis (BV) is a polymicrobial infection of the female reproductive tract. BV is characterized by replacement of health-associated Lactobacillus species by diverse anerobic bacteria, including the well-known Gardnerella vaginalis. Prevotella timonensis, and Prevotella bivia are anerobes that are found in a significant number of BV patients, but their contributions to the disease process remain to be determined. Defining characteristics of anerobic overgrowth in BV are adherence to the mucosal surface and the increased activity of mucin-degrading enzymes such as sialidases in vaginal secretions. We demonstrate that P. timonensis, but not P. bivia, strongly adheres to vaginal and endocervical cells to a similar level as G. vaginalis but did not elicit a comparable proinflammatory epithelial response. The P. timonensis genome uniquely encodes a large set of mucus-degrading enzymes, including four putative fucosidases and two putative sialidases, PtNanH1 and PtNanH2. Enzyme assays demonstrated that fucosidase and sialidase activities in P. timonensis cell-bound and secreted fractions were significantly higher than for other vaginal anerobes. In infection assays, P. timonensis efficiently removed fucose and α2,3- and α2,6-linked sialic acid moieties from the epithelial glycocalyx. Recombinantly expressed P. timonensis NanH1 and NanH2 cleaved α2,3 and α2,6-linked sialic acids from the epithelial surface, and sialic acid removal by P. timonensis could be blocked using inhibitors. This study demonstrates that P. timonensis has distinct virulence-related properties that include initial adhesion and a high capacity for mucin degradation at the vaginal epithelial mucosal surface. Our results underline the importance of understanding the role of different anerobic bacteria in BV.

IMPORTANCE

Bacterial vaginosis (BV) is a common vaginal infection that affects a significant proportion of women and is associated with reduced fertility and increased risk of secondary infections. Gardnerella vaginalis is the most well-known BV-associated bacterium, but Prevotella species including P. timonensis and P. bivia may also play an important role. We showed that, similar to G. vaginalis, P. timonensis adhered well to the vaginal epithelium, suggesting that both bacteria could be important in the first stage of infection. Compared to the other bacteria, P. timonensis was unique in efficiently removing the protective mucin sugars that cover the vaginal epithelium. These results underscore that vaginal bacteria play different roles in the initiation and development of BV.

Prevotella are major contributors of sialidases in the human vaginal microbiome

Elevated bacterial sialidase activity in the female genital tract is strongly associated with poor health outcomes including preterm birth and bacterial vaginosis (BV). These negative effects may arise from sialidase-mediated degradation of the protective mucus layer in the cervicovaginal environment. Prior biochemical studies of vaginal bacterial sialidases have focused solely on the BV-associated organism Gardnerella vaginalis. Despite their implications for sexual and reproductive health, sialidases from other vaginal bacteria have not been characterized. Here, we show that vaginal Prevotella species produce sialidases that possess variable activity toward mucin substrates. The sequences of sialidase genes and their presence are largely conserved across clades of Prevotella from different geographies, hinting at their importance globally. Finally, we find that Prevotella sialidase genes and transcripts, including those encoding mucin-degrading sialidases from Prevotella timonensis, are highly prevalent and abundant in human vaginal genomes and transcriptomes. Together, our results identify Prevotella as a critical source of sialidases in the vaginal microbiome, improving our understanding of this detrimental bacterial activity.

Vaginal community state types (CSTs) alter environmental cues and production of the Staphylococcus aureus toxic shock syndrome toxin-1 (TSST-1)

Menstrual toxic shock syndrome (mTSS) is a rare but life-threatening disease associated with the use of high-absorbency tampons. The production of the Staphylococcus aureus toxic shock syndrome toxin-1 (TSST-1) superantigen is involved in nearly all cases of mTSS and is tightly controlled by regulators responding to the environment. In the prototypic mTSS strain S. aureus MN8, the major repressor of TSST-1 is the carbon catabolite protein A (CcpA), which responds to glucose concentrations in the vaginal tract. Healthy vaginal Lactobacillus species also depend on glucose for both growth and acidification of the vaginal environment through lactic acid production. We hypothesized that interactions between the vaginal microbiota [herein referred to as community state types (CSTs)] and S. aureus MN8 depend on environmental cues and that these interactions subsequently affect TSST-1 production. Using S. aureus MN8 ΔccpA growing in various glucose concentrations, we demonstrate that the supernatants from different CSTs grown in vaginally defined medium (VDM) could significantly decrease tst expression. When co-culturing CST species with MN8 ∆ccpA, we show that Lactobacillus jensenii completely inhibits TSST-1 production in conditions mimicking healthy menstruation or mTSS. Finally, we show that growing S. aureus in "unhealthy" or "transitional" CST supernatants results in higher interleukin 2 (IL-2) production from T cells. These findings suggest that dysbiotic CSTs may encourage TSST-1 production in the vaginal tract and further indicate that the CSTs are likely important for the protection from mTSS.IMPORTANCEIn this study, we investigate the impact of the vaginal microbiota against Staphylococcus aureus in conditions mimicking the vaginal environment at various stages of the menstrual cycle. We demonstrate that Lactobacillus jensenii can inhibit toxic shock syndrome toxin-1 (TSST-1) production, suggesting the potential for probiotic activity in treating and preventing menstrual toxic shock syndrome (mTSS). On the other side of the spectrum, "unhealthy" or "transient" bacteria such as Gardnerella vaginalis and Lactobacillus iners support more TSST-1 production by S. aureus, suggesting that community state types are important in the development of mTSS. This study sets forward a model for examining contact-independent interactions between pathogenic bacteria and the vaginal microbiota. It also demonstrates the necessity of replicating the environment when studying one as dynamic as the vagina.

Interplay between Staphylococcus aureus and the vaginal microbiota

Staphylococcus aureus is a proficient colonizer and opportunistic pathogen which can lead to vaginal dysbiosis, aerobic vaginitis, or life-threatening menstrual toxic shock syndrome. Here we explore the complex but underappreciated interactions that S. aureus may impose on the vaginal environment leading to additional disease outcomes.

A non-invasive method to sample immune cells in the lower female genital tract using menstrual discs

T cells in the human female genital tract (FGT) 2 are key mediators of susceptibility to and protection from infection, including HIV and other sexually transmitted infections. There is a critical need for increased understanding of the distribution and activation of T cell populations in the FGT, but current sampling methods require a healthcare provider and are expensive, limiting the ability to study these populations longitudinally. To address these challenges, we have developed a method to sample immune cells from the FGT utilizing disposable menstrual discs which are non-invasive, self-applied, and low-cost. To demonstrate reproducibility, we sampled the cervicovaginal fluid (CVF) 3 of healthy, reproductive-aged individuals using menstrual discs over three sequential days. CVF was processed for cervicovaginal cells, and high parameter flow cytometry was used to characterize immune populations. We identified large numbers of live, CD45+ leukocytes, as well as distinct populations of T cells and B cells. Within the T cell compartment, activation and suppression status of T cell subsets were consistent with previous studies of the FGT utilizing current approaches, including identification of both tissue resident and migratory populations. In addition, the T cell population structure was highly conserved across days within individuals but divergent across individuals. Our approach to sample immune cells in the FGT with menstrual discs will decrease barriers to participation and empower longitudinal sampling in future research studies.

A Noninvasive Method to Sample Immune Cells in the Lower Female Genital Tract Using Menstrual Discs

T cells in the human female genital tract (FGT) are key mediators of susceptibility to and protection from infection, including HIV and other sexually transmitted infections. There is a critical need for increased understanding of the distribution and activation of T cell populations in the FGT, but current sampling methods require a healthcare provider and are expensive, limiting the ability to study these populations longitudinally. To address these challenges, we have developed a method to sample immune cells from the FGT utilizing disposable menstrual discs which are noninvasive, self-applied, and low in cost. To demonstrate reproducibility, we sampled the cervicovaginal fluid of healthy, reproductive-aged individuals using menstrual discs across 3 sequential days. Cervicovaginal fluid was processed for cervicovaginal cells, and high-parameter flow cytometry was used to characterize immune populations. We identified large numbers of live, CD45+ leukocytes, as well as distinct populations of T cells and B cells. Within the T cell compartment, activation and suppression status of T cell subsets were consistent with previous studies of the FGT utilizing current approaches, including identification of both tissue-resident and migratory populations. In addition, the T cell population structure was highly conserved across days within individuals but divergent across individuals. Our approach to sample immune cells in the FGT with menstrual discs will decrease barriers to participation and empower longitudinal sampling in future research studies.