Inerolysin and vaginolysin, the cytolysins implicated in vaginal dysbiosis, differently impair molecular integrity of phospholipid membranes

A multi-kingdom collection of 33,804 reference genomes for the human vaginal microbiome

The human vagina harbours diverse microorganisms-bacteria, viruses and fungi-with profound implications for women's health. Genome-level analysis of the vaginal microbiome across multiple kingdoms remains limited. Here we utilize metagenomic sequencing data and fungal cultivation to establish the Vaginal Microbial Genome Collection (VMGC), comprising 33,804 microbial genomes spanning 786 prokaryotic species, 11 fungal species and 4,263 viral operational taxonomic units. Notably, over 25% of prokaryotic species and 85% of viral operational taxonomic units remain uncultured. This collection significantly enriches genomic diversity, especially for prevalent vaginal pathogens such as BVAB1 (an uncultured bacterial vaginosis-associated bacterium) and Amygdalobacter spp. (BVAB2 and related species). Leveraging VMGC, we characterize functional traits of prokaryotes, notably Saccharofermentanales (an underexplored yet prevalent order), along with prokaryotic and eukaryotic viruses, offering insights into their niche adaptation and potential roles in the vagina. VMGC serves as a valuable resource for studying vaginal microbiota and its impact on vaginal health.

Vaginal microbiota and gynecological cancers: a complex and evolving relationship

The vagina hosts a community of microorganisms known as the vaginal microbiota. This community is relatively stable and straightforward, with Lactobacillus species being the most dominant members. The vaginal microbiota has various functions that are essential for maintaining human health and balance. For example, it can metabolise dietary nutrients, produce growth factors, communicate with other bacteria, modulate the immune system, and prevent the invasion of harmful pathogens. When the vaginal microbiota is disrupted, it can lead to diseases and infections. The observed disturbance is distinguished by a reduction in the prevalence of Lactobacillus and a concurrent rise in the number of other bacterial species that exhibit a higher tolerance to low oxygen levels. Gynecologic cancers are a group of cancers that affect the female reproductive organs and tissues, such as the ovaries, uterus, cervix, vagina, vulva, and endometrium. These cancers are a major global health problem for women. Understanding the complex interactions between the host and the vaginal microorganisms may provide new insights into the prevention and treatment of gynecologic cancers. This could improve the quality of life and health outcomes for women.

Cervicovaginal microbiota: a promising direction for prevention and treatment in cervical cancer

Cervical cancer is a common malignancy in women, with high incidence rate and mortality. Persistent infection of high-risk human papillomavirus (HPV) is the most important risk factor for cervical cancer and precancerous lesions. Cervicovaginal microbiota (CVM) plays an essential role in the defense of HPV infections and prevention of subsequent lesions. Dominance of Lactobacillus is the key of CVM homeostasis, which can be regulated by host, exogenous and endogenous factors. Dysbiosis of CVM, including altered microbial, metabolic, and immune signatures, can contribute to persist HPV infection, leading to cervical cancer. However, there is no evidence of the causality between CVM and cervical cancer, and the underlying mechanism remains unexplored. Considering the close correlation between CVM dysbiosis and persistent HPV infection, this review will overview CVM, its role in cervical cancer development and related mechanisms, and the prospects for therapeutic applications.

Extracellular vesicles from vaginal Gardnerella vaginalis and Mobiluncus mulieris contain distinct proteomic cargo and induce inflammatory pathways

Colonization of the vaginal space with bacteria such as Gardnerella vaginalis and Mobiluncus mulieris is associated with increased risk for STIs, bacterial vaginosis, and preterm birth, while Lactobacillus crispatus is associated with optimal reproductive health. Although host-microbe interactions are hypothesized to contribute to reproductive health and disease, the bacterial mediators that are critical to this response remain unclear. Bacterial extracellular vesicles (bEVs) are proposed to participate in host-microbe communication by providing protection of bacterial cargo, delivery to intracellular targets, and ultimately induction of immune responses from the host. We evaluated the proteome of bEVs produced in vitro from G. vaginalis, M. mulieris, and L. crispatus, identifying specific proteins of immunologic interest. We found that bEVs from each bacterial species internalize within cervical and vaginal epithelial cells, and that epithelial and immune cells express a multi-cytokine response when exposed to bEVs from G. vaginalis and M. mulieris but not L. crispatus. Further, we demonstrate that the inflammatory response induced by G. vaginalis and M. mulieris bEVs is TLR2-specific. Our results provide evidence that vaginal bacteria communicate with host cells through secreted bEVs, revealing a mechanism by which bacteria lead to adverse reproductive outcomes associated with inflammation. Elucidating host-microbe interactions in the cervicovaginal space will provide further insight into the mechanisms contributing to microbiome-mediated adverse outcomes and may reveal new therapeutic targets.

The interplay between HPV, other Sexually Transmissible Infections and genital microbiome on cervical microenvironment (MicroCervixHPV study)

Background

The importance of Cervicovaginal Microbiota in protecting against infections (such as HPV) is already well established, namely through Lactobacillus spp., as well as the mechanism through which HPV leads to Cervical Neoplasia. However, it is not possible to classify HPV as a complete carcinogen. Thus, the importance of exploring Cervicovaginal dysbiosis with the intention of deciphering this interaction with HPV, takes on greater relevance. The main objectives of this study were: 1) Comparison of the MCV composition of women with or without HPV and women with ASCUS or LSIL; 2) Characterization of cytokines present in the vaginal microenvironment; 3) Evaluation of the blood count ratios as prognostic systemic inflammatory biomarkers; 4) Correlation between MCV, HPV serotypes and cytokines.

Methods

This was a retrospective, observational, multicenter, cross-sectional study. CVM analysis was performed by isolation RNA and sequencing on a NGS platform. Cytokine concentrations of CVM were obtained through Multiplex platform. Statistical analysis was performed in SPSS v 26.0. An α of 0.05 was considered statistically significant.

Results

Highlighting the core of the study, CVM types of CST I and CST IV were found to influence the emergence of cervical lesions. Neutrophil-to-Lymphocyte ratio was found to impact the prognosis of ASCUS. Within CVM, Lactobacillus prevent the growth of other CST IV species, while the latter express symbiotic relationships with each other and show affinity for specific HPV serotypes. At last, RANTES chemokine is significantly elevated in cervicovaginal infections.

Conclusion

The importance of using vaginal cytokine profiles and CVM is highlighted in the hypothesis of prevention of Cervical Neoplasia development, as well as in its use as a prognostic biomarker. Taken together, these insights are one step closer to personalized medicine.

Microbiota dynamics, metabolic and immune interactions in the cervicovaginal environment and their role in spontaneous preterm birth

Differences in the cervicovaginal microbiota are associated with spontaneous preterm birth (sPTB), a significant cause of infant morbidity and mortality. Although establishing a direct causal link between cervicovaginal microbiota and sPTB remains challenging, recent advancements in sequencing technologies have facilitated the identification of microbial markers potentially linked to sPTB. Despite variations in findings, a recurring observation suggests that sPTB is associated with a more diverse and less stable vaginal microbiota across pregnancy trimesters. It is hypothesized that sPTB risk is likely to be modified via an intricate host-microbe interactions rather than due to the presence of a single microbial taxon or broad community state. Nonetheless, lactobacilli dominance is generally associated with term outcomes and contributes to a healthy vaginal environment through the production of lactic acid/maintenance of a low pH that excludes other pathogenic microorganisms. Additionally, the innate immunity of the host and metabolic interactions between cervicovaginal microbiota, such as the production of bacteriocins and the use of proteolytic enzymes, exerts a profound influence on microbial populations, activities, and host immune responses. These interplays collectively impact pregnancy outcomes. This review aims to summarize the complexity of cervicovaginal environment and microbiota dynamics, and associations with bacterial vaginosis and sPTB. There is also consideration on how probiotics may mitigate the risk of sPTB and bacterial vaginosis.

Human papillomavirus associated cervical lesion: pathogenesis and therapeutic interventions

Human papillomavirus (HPV) is the most prevalent sexually transmitted virus globally. Persistent high-risk HPV infection can result in cervical precancerous lesions and cervical cancer, with 70% of cervical cancer cases associated with high-risk types HPV16 and 18. HPV infection imposes a significant financial and psychological burden. Therefore, studying methods to eradicate HPV infection and halt the progression of precancerous lesions remains crucial. This review comprehensively explores the mechanisms underlying HPV-related cervical lesions, including the viral life cycle, immune factors, epithelial cell malignant transformation, and host and environmental contributing factors. Additionally, we provide a comprehensive overview of treatment methods for HPV-related cervical precancerous lesions and cervical cancer. Our focus is on immunotherapy, encompassing HPV therapeutic vaccines, immune checkpoint inhibitors, and advanced adoptive T cell therapy. Furthermore, we summarize the commonly employed drugs and other nonsurgical treatments currently utilized in clinical practice for managing HPV infection and associated cervical lesions. Gene editing technology is currently undergoing clinical research and, although not yet employed officially in clinical treatment of cervical lesions, numerous preclinical studies have substantiated its efficacy. Therefore, it holds promise as a precise treatment strategy for HPV-related cervical lesions.

Characteristics of vaginal microbes and classification of the vaginal microbiome

Background

The vaginal microbiome (VMB) has been classified into several discrete community state types, some of which have been associated with adverse human health conditions. However, the roles of the many vaginal bacteria in modulating the VMB and health remain unclear.

Methods

The associations among the vaginal taxa and other vaginal taxa, the vaginal pH, and the host gene expression responses were determined by calculating the correlation among the relative abundance of the vaginal taxa, the association between the vaginal pH and the predominant taxon in the VMB, and the correlation between the relative abundance of the vaginal taxa and human gene expression at the transcriptional level, respectively. Using these associations, an alternative more informative method, the biological vagitype (BVT), is proposed to classify community state types of the VMB.

Findings

Most Lactobacillus spp., with the exception of Lactobacillus iners , show significant correlations with host gene expression profiles and negative associations with dysbiosis-associated vaginal taxa. Many non- Lactobacillus spp. exhibit varied correlations with Lactobacillus spp., the vaginal pH, and host gene expression. Compared to other dysbiotic taxa, including Candidatus Lachnocurva vaginae, Gardnerella vaginalis has a stronger positive correlation with vaginal pH and a stronger negative correlation with Lactobacillus spp. Most dysbiosis-associated taxa are associated with stress responses of the host at the transcriptional level, but the genus Mycoplasma has a uniquely strong positive correlation with host immune responses. The association between BVTs of the VMBs and host characteristics, e.g., race/ethnicity, microbial infection, smoking, antibiotics, high blood pressure, economic state, diet, and others, was examined. The BVT classification method improved overall performance in associating specific vaginal microbial populations with host characteristics and phenotypes.

Interpretation

This study sheds light on the biological characteristics of the vaginal microbiota, including some less abundant or still unculturable taxa. Since the BVT method was established based on these biological characteristics, the classification outcome of the VMB may have more clinical relevance. Because the BVT method performs better in associating specific vaginal community types with diseases, e.g., bacterial vaginosis and gonorrhea, it could be beneficial for the predictive modeling of adverse health.

Funding

This work was supported by grants [UH3AI083263, U54HD080784, and R01HD092415] from the National Institutes of Health; and support from the [GAPPS BMGF PPB] grant from the Global Alliance to Prevent Prematurity and Stillbirth. We would also like to thank the Office of Research on Women's Health at NIH for their generous support.

Research in context

Evidence before this study: The vaginal microbiome (VMB) refers to the community of microorganisms in the female lower reproductive tract. The VMB is often a simple ecosystem dominated by a single species. The most predominant bacteria in the VMB include several Lactobacillus species and two non- Lactobacillus species, i.e., Candidatus Lachnocurva vaginae and Gardnerella vaginalis. Lactobacillus species produce lactic acid to lower the vaginal pH and inhibit the growth of disease-associated bacteria. Thus, the predominance of protective Lactobacilli, i.e., L. crispatus, L. jensenii , and L. gasseri , in the VMB is associated with overall vaginal health. However, the role of L. iners in promoting a healthy vaginal ecosystem is less clear. Actually, the biological and health relevance of many bacteria in the female lower reproductive tract is largely unknown. Some bacteria have low relative abundances, e.g., Peptostreptococcus and Coriobacteriaceae spp.; and others are not yet culturable, e.g., Candidatus Lachnocurva vaginae and BVAB TM7. When abundance of a taxon is low, its association with a host characteristic is a challenge. Previous methods to classify the VMB were based simply on their microbial compositions, and the biological characteristics of the vaginal bacteria were largely ignored. Thus, classification of these VMBs into biologically relevant community types, as described herein, should be helpful in determining their relevance to women's reproductive health. Added value of this study: This study examines three biological characteristics of bacteria in the VMB, i.e., the associations among different bacterial taxa, the vaginal pH, and the host response. Based on these three characteristics, the influence of these bacteria, particularly low abundant and unculturable bacteria, on vaginal health is evaluated. L. iners seems to be neutral in maintaining overall vaginal health. Gardnerella vaginalis is apparently more easily inhibited by Lactobacillus spp. than Candidatus Lachnocurva vaginae because of its stronger positive correlation with vaginal pH and negative correlation with Lactobacillus . The genus of Mycoplasma has a unique positive correlation with local immune responses, implying a role for Mycoplasma in promoting inflammation. Compared with previous methods to classify the VMB, a new method, considering the above three biological characteristics of bacteria in the VMB, has been established. The new method performs better in associating specific vaginal communities with host characteristics and phenotypes; e.g., bacterial vaginosis and gonorrhea. Implications of all the available evidence: Accurate biological classification of the VMB is fundamental for assessing its impact on women's health. Our classification scheme represents a step further toward that correct classification, eventually leading to new strategies for clinical assessment of the potential use of the VMB to diagnose or predict women's reproductive health.

Evaluation of vaginal microbiome equilibrium states identifies microbial parameters linked to resilience after menses and antibiotic therapy

The vaginal microbiome (VMB) is a complex microbial community that is closely tied to reproductive health. Optimal VMB communities have compositions that are commonly defined by the dominance of certain Lactobacillus spp. and can remain stable over time or transition to non-optimal states dominated by anaerobic bacteria and associated with bacterial vaginosis (BV). The ability to remain stable or undergo transitions suggests a system with either single (mono-stable) or multiple (multi-stable) equilibrium states, though factors that contribute to stability have been difficult to determine due to heterogeneity in microbial growth characteristics and inter-species interactions. Here, we use a computational model to determine whether differences in microbial growth and interaction parameters could alter equilibrium state accessibility and account for variability in community composition after menses and antibiotic therapies. Using a global uncertainty and sensitivity analysis that captures parameter sets sampled from a physiologically relevant range, model simulations predicted that 79.7% of microbial communities were mono-stable (gravitate to one composition type) and 20.3% were predicted to be multi-stable (can gravitate to more than one composition type, given external perturbations), which was not significantly different from observations in two clinical cohorts (HMP cohort, 75.2% and 24.8%; Gajer cohort, 78.1% and 21.9%, respectively). The model identified key microbial parameters that governed equilibrium state accessibility, such as the importance of non-optimal anaerobic bacteria interactions with Lactobacillus spp., which is largely understudied. Model predictions for composition changes after menses and antibiotics were not significantly different from those observed in clinical cohorts. Lastly, simulations were performed to illustrate how this quantitative framework can be used to gain insight into the development of new combinatorial therapies involving altered prebiotic and antibiotic dosing strategies. Altogether, dynamical models could guide development of more precise therapeutic strategies to manage BV.

Orally administrated Lactobacillus gasseri TM13 and Lactobacillus crispatus LG55 can restore the vaginal health of patients recovering from bacterial vaginosis

Bacterial vaginosis (BV) is a common infection of the lower genital tract with a vaginal microbiome dysbiosis caused by decreasing of lactobacilli. Previous studies suggested that supplementation with live Lactobacillus may benefit the recovery of BV, however, the outcomes vary in people from different regions. Herein, we aim to evaluate the effectiveness of oral Chinese-origin Lactobacillus with adjuvant metronidazole (MET) on treating Chinese BV patients. In total, 67 Chinese women with BV were enrolled in this parallel controlled trial and randomly assigned to two study groups: a control group treated with MET vaginal suppositories for 7 days and a probiotic group treated with oral Lactobacillus gasseri TM13 and Lactobacillus crispatus LG55 as an adjuvant to MET for 30 days. By comparing the participants with Nugent Scores ≥ 7 and < 7 on days 14, 30, and 90, we found that oral administration of probiotics did not improve BV cure rates (72.73% and 84.00% at day 14, 57.14% and 60.00% at day 30, 32.14% and 48.39% at day 90 for probiotic and control group respectively). However, the probiotics were effective in restoring vaginal health after cure by showing higher proportion of participants with Nugent Scores < 4 in the probiotic group compared to the control group (87.50% and 71.43% on day 14, 93.75% and 88.89% on day 30, and 77.78% and 66.67% on day 90). The relative abundance of the probiotic strains was significantly increased in the intestinal microbiome of the probiotic group compared to the control group at day 14, but no significance was detected after 30 and 90 days. Also, the probiotics were not detected in vaginal microbiome, suggesting that L. gasseri TM13 and L. crispatus LG55 mainly acted through the intestine. A higher abundance of Prevotella timonensis at baseline was significantly associated with long-term cure failure of BV and greatly contributed to the enrichment of the lipid IVA synthesis pathway, which could aggravate inflammation response. To sum up, L. gasseri TM13 and L. crispatus LG55 can restore the vaginal health of patients recovering from BV, and individualized intervention mode should be developed to restore the vaginal health of patients recovering from BV.

Clinical trial registration

https://classic.clinicaltrials.gov/ct2/show/, identifier NCT04771728.

Roles of the Microbiota of the Female Reproductive Tract in Gynecological and Reproductive Health

The microbiome of the female reproductive tract defies the convention that high biodiversity is a hallmark of an optimal ecosystem. Although not universally true, a homogeneous vaginal microbiome composed of species of Lactobacillus is generally associated with health, whereas vaginal microbiomes consisting of other taxa are generally associated with dysbiosis and a higher risk of disease. The past decade has seen a rapid advancement in our understanding of these unique biosystems. Of particular interest, substantial effort has been devoted to deciphering how members of the microbiome of the female reproductive tract impact pregnancy, with a focus on adverse outcomes, including but not limited to preterm birth. Herein, we review recent research efforts that are revealing the mechanisms by which these microorganisms of the female reproductive tract influence gynecologic and reproductive health of the female reproductive tract.

Age-Related Changes, Influencing Factors, and Crosstalk Between Vaginal and Gut Microbiota: A Cross-Sectional Comparative Study of Pre- and Postmenopausal Women

Objective: The ideal vaginal environment is maintained by Lactobacillus species, which keep the vagina clean and free of infections, boost fertility and immunity. Age-related decline in estrogen affects Lactobacillus population, leading to dominance of nonoptimal species and increased diversity in vaginal microbiota. In this study, we compared the differences between the vaginal microbiota of pre- and postmenopausal women. We also examined the relationships between vaginal and gut microbiota, their relationships with sex hormones and equol-producing ability. Materials and Methods: This was a cross-sectional study of 35 premenopausal and 35 postmenopausal women (age range: 27-76 years). We compared parameters such as the composition of the gut and vaginal microbiota, vaginal pH, estradiol, follicular stimulating hormone, and urinary equol concentration. Results: In the vaginal microbiota of premenopausal women, Lactobacillus species constituted ∼71.98%, and nonoptimal species constituted ∼16.87%. They were 10.08% and 26.78%, respectively, in the vaginal microbiota of postmenopausal women. The proportion of Lactobacillus was significantly low, whereas microbial diversity and vaginal pH were significantly high (p < 0.0001) in postmenopausal women. The compositions of the vaginal microbiota were significantly different in pre- and postmenopausal women. However, such differences were not noticeable in the gut microbiota. Urinary equol production had no significant correlation with vaginal microbiota, although it had significant relationships with gut microbiota in postmenopausal women. In both groups, the proportions of vaginal Lactobacillus were inversely correlated with vaginal microbial diversity and vaginal pH. Conclusion: Postmenopausal women had significantly low Lactobacillus and high nonoptimal species in their vaginal flora, whereas such age-related differences were not identified in gut microbiota. Urinary equol concentration had significant correlation with gut microbiota in postmenopausal women only. This study was registered with the University Hospital Medical Information Network (UMIN) Clinical Trial Registry (Trial registration No.: UMIN000043944).

Vaginal Lactobacillus iners abundance is associated with outcome in antibiotic treatment of bacterial vaginosis and capable of inhibiting Gardnerella

Bacterial vaginosis is characterized as a polymicrobial dysbiosis with the loss of Lactobacillus spp. and growth of multiple anerobic bacteria, including Gardnerella, Prevotella and Atopobium ranked as the top three most abundant. A total of nine Gardnerella genomospecies have been identified, yet the association between their distribution or any exact Lactobacillus species with BV occurrence or prognosis remains controversial. A total of 308 patients and 62 healthy women who sought annual examinations were recruited, with 130 BV patients and 41 healthy women who met our inclusion criteria finally included. Vaginal samples were used for microscopic examination, 16S rRNA sequencing, bacterial culture and isolation. Isolates of Gardnerella vaginalis, Fannyhessae vaginae (used to be called Atopobium vaginae) and Lactobacillus iners were used for competition tests. We found that the relative abundances of Gardnerella, Prevotella and Atopobium were elevated in BV patients compared to healthy people (p<0.0001), yet no significant differences were found among patients with different clinical outcomes (p>0.05). Seven out of nine Gardnerella genomospecies were present in both BV patients and healthy women, and the relative abundances of all detected genomospecies were higher in BV patients (p<0.05). Cured patients possessed higher GS03 than intermediate and failed patients (p=0.005, 0.0337). L. iners was significantly higher in cured patients than in the other two groups (p=0.0021, p<0.0001), and its ability to inhibit the growth of G. vaginalis and F. vaginae was validated. In summary, seven Gardnerella genomospecies were detected in Chinese BV patients, but no association of its distribution and BV occurrence or prognosis was found. The relative abundance of L. iners was higher in cured patients, and its antimicrobial activity against G. vaginalis and F. vaginae was validated through in vitro inhibition experiment. L. iners could become a predictive indicator of clinical outcomes of BV patients, and its antimicrobial function might be beneficial to BV patients.

Single-molecule analysis of the entire perfringolysin O pore formation pathway

The cholesterol-dependent cytolysin perfringolysin O (PFO) is secreted by Clostridium perfringens as a bacterial virulence factor able to form giant ring-shaped pores that perforate and ultimately lyse mammalian cell membranes. To resolve the kinetics of all steps in the assembly pathway, we have used single-molecule fluorescence imaging to follow the dynamics of PFO on dye-loaded liposomes that lead to opening of a pore and release of the encapsulated dye. Formation of a long-lived membrane-bound PFO dimer nucleates the growth of an irreversible oligomer. The growing oligomer can insert into the membrane and open a pore at stoichiometries ranging from tetramers to full rings (~35 mers), whereby the rate of insertion increases linearly with the number of subunits. Oligomers that insert before the ring is complete continue to grow by monomer addition post insertion. Overall, our observations suggest that PFO membrane insertion is kinetically controlled.

Towards a deeper understanding of the vaginal microbiota

The human vaginal microbiota is a critical determinant of vaginal health. These communities live in close association with the vaginal epithelium and rely on host tissues for resources. Although often dominated by lactobacilli, the vaginal microbiota is also frequently composed of a collection of facultative and obligate anaerobes. The prevalence of these communities with a paucity of Lactobacillus species varies among women, and epidemiological studies have associated them with an increased risk of adverse health outcomes. The mechanisms that drive these associations have yet to be described in detail, with few studies establishing causative relationships. Here, we review our current understanding of the vaginal microbiota and its connection with host health. We centre our discussion around the biology of the vaginal microbiota when Lactobacillus species are dominant versus when they are not, including host factors that are implicated in shaping these microbial communities and the resulting adverse health outcomes. We discuss current approaches to modulate the vaginal microbiota, including probiotics and vaginal microbiome transplants, and argue that new model systems of the cervicovaginal environment that incorporate the vaginal microbiota are needed to progress from association to mechanism and this will prove invaluable for future research.

Insight into the ecology of vaginal bacteria through integrative analyses of metagenomic and metatranscriptomic data

Background

Vaginal bacterial communities dominated by Lactobacillus species are associated with a reduced risk of various adverse health outcomes. However, somewhat unexpectedly, many healthy women have microbiota that are not dominated by lactobacilli. To determine the factors that drive vaginal community composition we characterized the genetic composition and transcriptional activities of vaginal microbiota in healthy women.

Results

We demonstrate that the abundance of a species is not always indicative of its transcriptional activity and that impending changes in community composition can be predicted from metatranscriptomic data. Functional comparisons highlight differences in the metabolic activities of these communities, notably in their degradation of host produced mucin but not glycogen. Degradation of mucin by communities not dominated by Lactobacillus may play a role in their association with adverse health outcomes. Finally, we show that the transcriptional activities of L. crispatus, L. iners, and Gardnerella vaginalis vary with the taxonomic composition of the communities in which they reside. Notably, L. iners and G. vaginalis both demonstrate lower expression of their cholesterol-dependent cytolysins when co-resident with Lactobacillus spp. and higher expression when co-resident with other facultative and obligate anaerobes. The pathogenic potential of these species may depend on the communities in which they reside and thus could be modulated by interventional strategies.

Conclusions

Our results provide insight to the functional ecology of the vaginal microbiota, demonstrate the diagnostic potential of metatranscriptomic data, and reveal strategies for the management of these ecosystems.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13059-022-02635-9.

Electrochemical Impedance Spectroscopy as a Convenient Tool to Characterize Tethered Bilayer Membranes

In this paper, we describe the application of electrochemical impedance spectroscopy (EIS) to characterize process of formation and properties of solid-supported tethered bilayer membranes on solid conducting substrates. Along with the description of experimental procedures to prepare substrates and self-assembly of phospholipid bilayers onto gold-coated glass slides, we describe the detailed protocols of EIS measurements. We demonstrate the utility of EIS in the evaluation of the properties of both molecular anchor layers used to immobilize tBLMs as well as characterization of tBLMs. We show that the EIS methodology extends the applicability of this technique well beyond the mere evaluation of electric parameters. Specifically, we demonstrate how by using EIS one may evaluate both density and size of water-filled defects (ion-channels) in tBLMs, to determine the structural mode (homogeneous, heterogeneous, or clustered) of distribution of defects in tBLMs. Our methodology can be applied in both basic protein membrane interaction studies, as well as in the development of precision biosensoric systems with tBLMs as a sensing element.

Contribution of Lactobacillus iners to Vaginal Health and Diseases: A Systematic Review

Lactobacillus iners, first described in 1999, is a prevalent bacterial species of the vaginal microbiome. As L. iners does not easily grow on de Man-Rogosa-Sharpe agar, but can grow anaerobically on blood agar, it has been initially overlooked by traditional culture methods. It was not until the wide application of molecular biology techniques that the function of L. iners in the vaginal microbiome was carefully explored. L. iners has the smallest genome among known Lactobacilli and it has many probiotic characteristics, but is partly different from other major vaginal Lactobacillus species, such as L. crispatus, in contributing to the maintenance of a healthy vaginal microbiome. It is not only commonly present in the healthy vagina but quite often recovered in high numbers in bacterial vaginosis (BV). Increasing evidence suggests that L. iners is a transitional species that colonizes after the vaginal environment is disturbed and offers overall less protection against vaginal dysbiosis and, subsequently, leads to BV, sexually transmitted infections, and adverse pregnancy outcomes. Accordingly, under certain conditions, L. iners is a genuine vaginal symbiont, but it also seems to be an opportunistic pathogen. Further studies are necessary to identify the exact role of this intriguing species in vaginal health and diseases.

The composition of human vaginal microbiota transferred at birth affects offspring health in a mouse model

Newborns are colonized by maternal microbiota that is essential for offspring health and development. The composition of these pioneer communities exhibits individual differences, but the importance of this early-life heterogeneity to health outcomes is not understood. Here we validate a human microbiota-associated model in which fetal mice are cesarean delivered and gavaged with defined human vaginal microbial communities. This model replicates the inoculation that occurs during vaginal birth and reveals lasting effects on offspring metabolism, immunity, and the brain in a community-specific manner. This microbial effect is amplified by prior gestation in a maternal obesogenic or vaginal dysbiotic environment where placental and fetal ileum development are altered, and an augmented immune response increases rates of offspring mortality. Collectively, we describe a translationally relevant model to examine the defined role of specific human microbial communities on offspring health outcomes, and demonstrate that the prenatal environment dramatically shapes the postnatal response to inoculation.

Characteristics associated with Lactobacillus iners-dominated vaginal microbiota

OBJECTIVE

The protective role of Lactobacillus iners in the vaginal microbiota has been questioned. Recent studies have shown that L. iners is the dominating taxon in a large subset of women worldwide. The aim of this study was to identify sociodemographic, behavioural and clinical variables associated with L. iners-dominated community state type (CST) III in Brazilian women of reproductive age.

PARTICIPANTS AND METHODS

This study leveraged microbiota compositional data generated by sequencing of the V3-V4 16S rRNA gene from vaginal samples collected from 442 participants enrolled in a previous cross-sectional study that included 609 women in five geographical regions of Brazil. A total of 167 (27.4%) participants were excluded from the current study as they did not present a Lactobacillus-dominated vaginal microbiota. Data on sociodemographic and behavioural characteristics of the study population were obtained through face-to-face interviews. Participants were assigned to two study groups: those with L. iners-dominated CST III (n=222) and those with three distinct CSTs (I, II or V) dominated by another Lactobacillus spp. (n=220). Logistic regression analysis using a stepwise method was performed to test association between CST III and participants' characteristics, considering their OR and 95% CIs.

RESULTS

Among the population characteristics assessed, L. iners-dominated CST III was independently associated with having two or more sexual partners (OR 3.27; 95% CI 1.50 to 7.11) and microscopic detection of Candida sp. on vaginal smears (OR 2.24; 95% CI 1.02 to 4.89). Other characteristics were inversely associated with CST III, including condom use (OR 0.59; 95% CI 0.38 to 0.91), higher educational level (OR 0.61; 95% CI 0.41 to 0.91) and diet containing milk/dairy intake (OR 0.43; 95% CI 0.20 to 0.90).

CONCLUSION

Unprotected sex practices, number of sexual partners and lower educational levels may be useful for identifying women with L. iners-dominated microbiota and its suboptimal protective properties. L. iners microbiota does not seem to provide optimal protection against Candida sp. colonisation, warranting further investigation.

Tethered Lipid Membranes as a Nanoscale Arrangement towards Non-Invasive Analysis of Acute Pancreatitis

Extracellular heat shock proteins (HSPs) mediate immunological functions and are involved in pathologies such as infection, stress, and cancer. Here, we demonstrated the dependence of an amount of HSP70 and HSP90 in serum vs. severity of acute pancreatitis (AP) on a cohort of 49 patients. Tethered bilayer lipid membranes (tBLMs) have been developed to investigate HSPs’ interactions with tBLMs that can be probed by electrochemical impedance spectroscopy (EIS). The results revealed that HSP70 and HSP90 interact via different mechanisms. HSP70 shows the damage of the membrane, while HSP90 increases the insulation properties of tBLM. These findings provide evidence that EIS offers a novel approach for the study of the changes in membrane integrity induced by HSPs proteins. Herein, we present an alternative electrochemical technique, without any immunoprobes, that allows for the monitoring of HSPs on nanoscaled tBLM arrangement in biologics samples such us human urine. This study demonstrates the great potential of tBLM to be used as a membrane based biosensor for novel, simple, and non-invasive label-free analytical system for the prediction of AP severity.

Why Do Tethered-Bilayer Lipid Membranes Suit for Functional Membrane Protein Reincorporation?

Membrane proteins (MPs) are essential for cellular functions. Understanding the functions of MPs is crucial as they constitute an important class of drug targets. However, MPs are a challenging class of biomolecules to analyze because they cannot be studied outside their native environment. Their structure, function and activity are highly dependent on the local lipid environment, and these properties are compromised when the protein does not reside in the cell membrane. Mammalian cell membranes are complex and composed of different lipid species. Model membranes have been developed to provide an adequate environment to envisage MP reconstitution. Among them, tethered-Bilayer Lipid Membranes (tBLMs) appear as the best model because they allow the lipid bilayer to be decoupled from the support. Thus, they provide a sufficient aqueous space to envisage the proper accommodation of large extra-membranous domains of MPs, extending outside. Additionally, as the bilayer remains attached to tethers covalently fixed to the solid support, they can be investigated by a wide variety of surface-sensitive analytical techniques. This review provides an overview of the different approaches developed over the last two decades to achieve sophisticated tBLMs, with a more and more complex lipid composition and adapted for functional MP reconstitution.

Cholesterol-Dependent Cytolysins Produced by Vaginal Bacteria: Certainties and Controversies

Bacterial vaginosis (BV) is a vaginal anaerobic dysbiosis that affects women of reproductive age worldwide. BV is microbiologically characterized by the depletion of vaginal lactobacilli and the overgrowth of anaerobic bacterial species. Accumulated evidence suggests that Gardnerella spp. have a pivotal role among BV-associated bacteria in the initiation and development of BV. However, Gardnerella spp. often colonize healthy women. Lactobacillus iners is considered as a prevalent constituent of healthy vaginal microbiota, and is abundant in BV. Gardnerella spp. and L. iners secrete the toxins vaginolysin (VLY) and inerolysin (INY), which have structural and activity features attributed to cholesterol-dependent cytolysins (CDCs). CDCs are produced by many pathogenic bacteria as virulence factors that participate in various stages of disease progression by forming lytic and non-lytic pores in cell membranes or via pore-independent pathways. VLY is expressed in the majority of Gardnerella spp. isolates; less is known about the prevalence of the gene that encodes INY. INY is a classical CDC; membrane cholesterol acts a receptor for INY. VLY uses human CD59 as its receptor, although cholesterol remains indispensable for VLY pore-forming activity. INY-induced damage of artificial membranes is directly dependent on cholesterol concentration in the bilayer, whereas VLY-induced damage occurs with high levels of membrane cholesterol (>40 mol%). VLY primarily forms membrane-embedded complete rings in the synthetic bilayer, whereas INY forms arciform structures with smaller pore sizes. VLY activity is high at elevated pH, which is characteristic of BV, whereas INY activity is high at more acidic pH, which is specific for a healthy vagina. Increased VLY levels in vaginal mucosa in vivo were associated with clinical indicators of BV. However, experimental evidence is lacking for the specific roles of VLY and INY in BV. The interplay between vaginal bacterial species affects the expression of the gene encoding VLY, thereby modulating the virulence of Gardnerella spp. This review discusses the current evidence for VLY and INY cytolysins, including their structures and activities, factors affecting their expression, and their potential impacts on the progression of anaerobic dysbiosis.