Commensal bacteria modulate innate immune responses of vaginal epithelial cell multilayer cultures

Interaction of microbiota, mucosal malignancies, and immunotherapy-Mechanistic insights

The microbiome has emerged as a crucial modulator of host-immune interactions and clearly impacts tumor development and therapy efficacy. The microbiome is a double-edged sword in cancer development and therapy as both pro-tumorigenic and anti-tumorigenic bacterial taxa have been identified. The staggering number of association-based studies in various tumor types has led to an enormous amount of data that makes it difficult to identify bacteria that promote tumor development or modulate therapy efficacy from bystander bacteria. Here we aim to comprehensively summarize the current knowledge of microbiome-host immunity interactions and cancer therapy in various mucosal tissues to find commonalities and thus identify potential functionally relevant bacterial taxa. Moreover, we also review recent studies identifying specific bacteria and mechanisms through which the microbiome modulates cancer development and therapy efficacy.

Protective Properties of S-layer Protein 2 from Lactobacillus crispatus 2029 against Candida albicans Infections

Previously, the protective role of the S-layer protein 2 (Slp2) of the vaginal Lactobacillus crispatus 2029 (LC2029) strain against foodborne pathogens Campylobacter jejuni, Salmonella enterica serovar Enteritidis, and Escherichia coli O157:H was demonstrated. We demonstrate the new roles of the Slp2-positive LC2029 strain and soluble Slp2 against C. albicans infections. We show that LC2029 bacteria can adhere to the surface of the cervical epithelial HeLa cells, prevent their contact with C. albicans, and block yeast transition to a pathogenic hyphal form. Surface-bound Slp2 provides the ability for LC2029 to co-aggregate with various C. albicans strains, including clinical isolates. C. albicans-induced necrotizing epithelial damage is reduced by colonization with the Slp2-positive LC2029 strain. Slp2 inhibits the adhesion of various strains of C. albicans to different human epithelial cells, blocks yeast transition to a pathogenic hyphal form, and prevents the colonization and pathogenic infiltration of mucosal barriers. Only Slp2 and LC2029 bacteria stimulate the production of protective human β-defensin 3 in various epithelial cells. These findings support the anti-Candida albicans potential of the probiotic LC2029 strain and Slp2 and form the basis for further research on their ability to prevent and manage invasive Candida infections.

Validation of vaginal microbiome proxies for in vitro experiments that biomimic Lactobacillus-dominant vaginal cultures

The vaginal microbiome includes diverse microbiota dominated by Lactobacillus [L.] spp. that protect against infections, modulate inflammation, and regulate vaginal homeostasis. Because it is challenging to incorporate vaginal microbiota into in vitro models, including organ-on-a-chip systems, we assessed microbial metabolites as reliable proxies in addition to traditional vaginal epithelial cultures (VECs). Human immortalized VECs cultured on transwells with an air-liquid interface generated stratified cell layers colonized by transplanted healthy microbiomes (L. jensenii- or L. crispatus-dominant) or a community representing bacterial vaginosis (BV). After 48-h, a qPCR array confirmed the expected donor community profiles. Pooled apical and basal supernatants were subjected to metabolomic analysis (untargeted mass spectrometry) followed by ingenuity pathways analysis (IPA). To determine the bacterial metabolites' ability to recreate the vaginal microenvironment in vitro, pooled bacteria-free metabolites were added to traditional VEC cultures. Cell morphology, viability, and cytokine production were assessed. IPA analysis of metabolites from colonized samples contained fatty acids, nucleic acids, and sugar acids that were associated with signaling networks that contribute to secondary metabolism, anti-fungal, and anti-inflammatory functions indicative of a healthy vaginal microbiome compared to sterile VEC transwell metabolites. Pooled metabolites did not affect cell morphology or induce cell death (∼5.5%) of VEC cultures (n = 3) after 72-h. However, metabolites created an anti-inflammatory milieu by increasing IL-10 production (p = .06, T-test) and significantly suppressing pro-inflammatory IL-6 (p = .0001), IL-8 (p = .009), and TNFα (p = .0007) compared to naïve VEC cultures. BV VEC conditioned-medium did not affect cell morphology nor viability; however, it induced a pro-inflammatory environment by elevating levels of IL-6 (p = .023), IL-8 (p = .031), and TNFα (p = .021) when compared to L.-dominate microbiome-conditioned medium. VEC transwells provide a suitable ex vivo system to support the production of bacterial metabolites consistent with the vaginal milieu allowing subsequent in vitro studies with enhanced accuracy and utility.

Impaired immune response against SARS-CoV-2 infection is the major factor indirectly altering reproductive function in COVID-19 patients: a narrative review

Coronavirus disease 2019 (COVID-19) is an infectious disease affecting multiple systems and organs, including the reproductive system. SARS-CoV-2, the virus that causes COVID-19, can damage reproductive organs through direct (angiotensin converting enzyme-2, ACE-2) and indirect mechanisms. The immune system plays an essential role in the homeostasis and function of the male and female reproductive systems. Therefore, an altered immune response related to infectious and inflammatory diseases can affect reproductive function and fertility in both males and females. This narrative review discussed the dysregulation of innate and adaptive systems induced by SARS-CoV-2 infection. We reviewed the evidence showing that this altered immune response in COVID-19 patients is the major indirect mechanism leading to adverse reproduction outcomes in these patients. We summarized studies reporting the long-term effect of SARS-CoV-2 infection on women's reproductive function and proposed the chronic inflammation and chronic autoimmunity characterizing long COVID as potential underlying mechanisms. Further studies are needed to clarify the role of autoimmunity and chronic inflammation (long COVID) in altered female reproduction function in COVID-19.

Next generation 3D-printed intravaginal ring for prevention of HIV and unintended pregnancy

Globally, there are 20 million adolescent girls and young women living with HIV who have limited access to long-acting, effective, women-controlled preventative methods. Additionally, although there are many contraceptive methods available, globally, half of all pregnancies remain unintended. Here we report the first 3D-printed multipurpose prevention technology (MPT) intravaginal ring (IVR) for HIV prevention and contraception. We utilized continuous liquid interface production (CLIP™) to fabricate MPT IVRs in a biocompatible silicone-based resin. Etonogestrel (ENG), ethinyl estradiol (EE), and islatravir (ISL) were loaded into the silicone poly(urethane) IVR in a controlled single step drug loading process driven by absorption. ENG/EE/ISL IVR promoted sustained release of drugs for 150 days in vitro and 14 days in sheep. There were no adverse MPT IVR-related findings of cervicovaginal toxicity or changes in vaginal biopsies or microbiome community profiles evaluated in sheep. Furthermore, ISL IVR in macaques promoted sustained release for 28 days with ISL-triphosphate levels above the established pharmacokinetic benchmark of 50-100 fmol/106 PBMCs. The ISL IVR was found to be safe and well tolerated in the macaques with no observed mucosal cytokine changes or alterations in peripheral CD4 T-cell populations. Collectively, the proposed MPT IVR has potential to expand preventative choices for young women and girls.

Vaginal microbiome in obesity and its impact on reproduction

A number of reproductive outcomes have been increasingly found to be affected by the vaginal microbiota. Obesity has become a global epidemic, affecting increasing numbers of reproductive-age women, and has been shown to be a risk factor for a number of adverse female health outcomes. A healthy vaginal microbiome is characterized by Lactobacillus-dominance, in particular Lactobacillus crispatus; obesity has been found to be associated with higher diversity and a lower likelihood of Lactobacillus-dominance. In this review, we summarize the evidence on the vaginal microbiome in obese women and the impact on reproductive outcomes such as conception rates, early pregnancy, and preterm birth. We further explore the mechanisms by which obesity may result in an altered microbial composition and highlight future avenues for therapeutic targeting of the vaginal microbiota.

Imbalance of Vaginal Microbiota and Immunity: Two Main Accomplices of Cervical Cancer in Chinese Women

Objective

To explore the correlation of female vaginal microbiota and immune factors with cervical cancer.

Methods

The distribution pattern difference of vaginal microbiota of four groups of women (cervical cancer, HPV-positive CIN, HPV-positive non-CIN, and HPV-negative groups) were compared by microbial 16S rDNA sequencing. The protein chip was used to detect the composition and changes of the immune factors in the four groups.

Results

Alpha diversity analysis demonstrated that the diversity of the vaginal microbiota was increased as the disease develops. Among those bacteria abundant in the vaginal microbiota, Lactobacillus, Prevotella, and Gardnerella dominate at the genus level of vaginal flora. Compared with the HPV-negative group, the differentially dominant bacteria, such as Prevotella, Ralstonia, Gardnerella and Sneathia, are enriched in the cervical cancer group. Likewise, Gardnerella, Prevotella, and Sneathia are more in the HPV-positive CIN group, while Gardnerella and Prevotella in the HPV-positive non-CIN group, respectively. In contrast, Lactobacillus and Atopobium are dominant in the HPV-negative group (LDA>4log10). The concentration of inflammatory immune factors IP-10 and VEGF-A were increased in the cervical cancer group (P < 0.05), compared with other groups.

Conclusion

The occurrence of cervical cancer is related to an increase of vaginal microbiota diversity and up-regulation of inflammatory immune factor proteins. The abundance of Lactobacillus was decreased while the one of Prevotella and Gardnerella were increased in the cervical cancer group, compared with other three groups. Moreover, the IP-10 and VEGF-A were also increased in the cervical cancer group. Thus, evaluation of changes in the vaginal microbiota and these two immune factor levels might be a potential non-invasive and simple method to predict cervical cancer. Furthermore, it is significant to adjust and restore the balance of vaginal microbiota and maintain normal immune function in preventing and treating cervical cancer.

Advanced Organotypic In Vitro Model Systems for Host-Microbial Coculture

In vitro model systems have been advanced to recapitulate important physiological features of the target organ in vivo more closely than the conventional cell line cultures on a petri dish. The advanced organotypic model systems can be used as a complementary or alternative tool for various testing and screening. Numerous data from germ-free animal studies and genome sequencings of clinical samples indicate that human microbiota is an essential part of the human body, but current in vitro model systems rarely include them, which can be one of the reasons for the discrepancy in the tissue phenotypes and outcome of therapeutic intervention between in vivo and in vitro tissues. A coculture model system with appropriate microbes and host cells may have great potential to bridge the gap between the in vitro model and the in vivo counterpart. However, successfully integrating two species in one system introduces new variables to consider and poses new challenges to overcome. This review aims to provide perspectives on the important factors that should be considered for developing organotypic bacterial coculture models. Recent advances in various organotypic bacterial coculture models are highlighted. Finally, challenges and opportunities in developing organotypic microbial coculture models are also discussed.

Potential Role of Vaginal Microbiota in Ovarian Cancer Carcinogenesis, Progression and Treatment

Ovarian cancer represents one of the most challenging gynecologic cancers which still has numerous unknowns on the underlying pathogenesis. In addition to the verified contributors such as genomic predisposition and medical history in the carcinogenesis, emerging evidence points out the potential role of vaginal microbiota in ovarian cancer. Recent studies have underlined the presence of vaginal microbial dysbiosis in cancer cases. Increasing research also indicates the potential correlations between vaginal microbes and cancer carcinogenesis, progression and treatment. Currently, compared with other gynecologic cancers, reports on the roles of vaginal microbiota in ovarian cancer remain scarce and fragmentary. Therefore, in this review, we summarize the roles of vaginal microbiota in various gynecologic diseases, particularly focusing on the potential mechanisms and possible applications of vaginal microbiota in ovarian cancer, giving insight into the involvement of vaginal microbiota in gynecologic cancer treatment.

Female reproductive tract microbiome and early miscarriages

Miscarriage is one of the main causes of reproductive loss, which can lead to a number of physical and psychological complications and other long-term consequences. However, the role of vaginal and uterine microbiome in such complications is poorly understood. To review the published data on the function of the female reproductive tract microbiome in the pathogenesis of early miscarriages. The articles published over the past 20 years and deposited in PubMed, Google Academy, Scopus, Elibrary, ResearchGate, and EBSCO databases were analyzed. The review presents new data on the impact of the vaginal and uterine microbiome on the local immunity, including defense against sexually transmitted infections, and its association with other factors of miscarriages. The studies on the microbiome of non-pregnant women with recurrent miscarriages in the anamnesis, patients undergoing IVF, and pregnant women with miscarriages, as well as new directions in the microbiome research are discussed. The majority of studies have demonstrated that the dominant species of the vaginal and uterine microbiome in patients with early miscarriages are non-Lactobacillus bacteria. As many of these bacteria have not previously been detected by cultural studies and their role in obstetric complications is not well defined, further research on the female reproductive tract microbiome, including the microbiome of the cervix uteri, is needed to develop new approaches for the prognosis and prevention of miscarriages.

Copper intrauterine device increases vaginal concentrations of inflammatory anaerobes and depletes lactobacilli compared to hormonal options in a randomized trial

Effective contraceptives are a global health imperative for reproductive-aged women. However, there remains a lack of rigorous data regarding the effects of contraceptive options on vaginal bacteria and inflammation. Among 218 women enrolled into a substudy of the ECHO Trial (NCT02550067), we evaluate the effect of injectable intramuscular depot medroxyprogesterone acetate (DMPA-IM), levonorgestrel implant (LNG), and a copper intrauterine device (Cu-IUD) on the vaginal environment after one and six consecutive months of use, using 16S rRNA gene sequencing and multiplex cytokine assays. Primary endpoints include incident BV occurrence, bacterial diversity, and bacterial and cytokine concentrations. Secondary endpoints are bacterial and cytokine concentrations associated with later HIV seroconversion. Participants randomized to Cu-IUD exhibit elevated bacterial diversity, increased cytokine concentrations, and decreased relative abundance of lactobacilli after one and six months of use, relative to enrollment and other contraceptive options. Total bacterial loads of women using Cu-IUD increase 5.5 fold after six months, predominantly driven by increases in the concentrations of several inflammatory anaerobes. Furthermore, growth of L. crispatus (MV-1A-US) is inhibited by Cu2+ ions below biologically relevant concentrations, in vitro. Our work illustrates deleterious effects on the vaginal environment induced by Cu-IUD initiation, which may adversely impact sexual and reproductive health.

Staphylococcus aureus Fibronectin-Binding Proteins Contribute to Colonization of the Female Reproductive Tract

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic pathogen and frequent colonizer of human skin and mucosal membranes, including the vagina, with vaginal colonization reaching nearly 25% in some pregnant populations. MRSA vaginal colonization can lead to aerobic vaginitis (AV), and during pregnancy, bacterial ascension into the upper reproductive tract can lead to adverse birth outcomes. USA300, the most prominent MRSA lineage to colonize pregnant individuals, is a robust biofilm former and causative agent of invasive infections; however, little is known about how it colonizes and ascends in the female reproductive tract (FRT). Our previous studies showed that a MRSA mutant of seven fibrinogen-binding adhesins was deficient in FRT epithelial attachment and colonization. Using both monolayer and multilayer air-liquid interface cell culture models, we determine that one class of these adhesins, the fibronectin binding proteins (FnBPA and FnBPB), are critical for association with human vaginal epithelial cells (hVECs) and hVEC invasion through interactions with α₅β₁ integrin. We observe that both FnBPs are important for biofilm formation as single and double fnbAB mutants exhibit reduced biofilm formation on hVECs. Using heterologous expression of fnbA and fnbB in Staphylococcus carnosus, FnBPs are also found to be sufficient for hVEC cellular association, invasion, and biofilm formation. In addition, we found that an ΔfnbAB mutant displays attenuated ascension in our murine vaginal colonization model. Better understanding of MRSA FRT colonization and ascension can ultimately inform treatment strategies to limit MRSA vaginal burden or prevent ascension, especially during pregnancy and in those prone to AV.

Probiotics in vaginal health

Bacterial vaginosis, a type of vaginal inflammation, can be considered the main reason for abnormal discharges of the vagina and vaginal dysbiosis during reproductive years. Epidemiological investigations of females suffering from vaginitis demonstrated that at least 30% to 50% of all women had Bacterial vaginosis (BV). One of the fields of treatment is the use of probiotics, probiotics are commonly defined as viable microorganisms (yeasts or bacteria) that can positively affect the health of their hosts. They are used in foods, notably fermented milk products, and medicine-related products. The development of new probiotic strains is aimed at more active advantageous organisms. Lactobacillus species are the dominant bacteria in a normal vagina that can decrease the pH of the vagina by the production of lactic acid. A number of lactobacilli types can produce hydrogen peroxide as well. The presence of hydrogen peroxide-induced low pH can prevent the growth of several other microorganisms. The vaginal flora of BV cases can modify by replacing the Lactobacillus species with a high density of anaerobic bacteria (i.e. Mobiluncus sp. Bacteroides sp.), Mycoplasma hominis, and Gardnerella vaginalis. More vaginal infections are treated with medications, while there is a possibility of recurrence and chronic infection because of the adverse effects on the indigenous lactobacilli. Probiotics and prebiotics have shown capacities for optimizing, maintaining, and restoring the vaginal microflora. Therefore, biotherapeutics can offer alternative approaches to reduce infections of the vagina and thus promote consumers' health.

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

BACKGROUND

A 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.

RESULTS

Here, 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 and growth of the L. crispatus consortia on-chip 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.

CONCLUSION

This 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. Video Abstract.

Lactic acid from vaginal microbiota enhances cervicovaginal epithelial barrier integrity by promoting tight junction protein expression

BACKGROUND

Women with a cervicovaginal microbiota dominated by Lactobacillus spp. are at reduced risk of acquiring sexually transmitted infections including HIV, but the biological mechanisms involved remain poorly defined. Here, we performed metaproteomics on vaginal swab samples from young South African women (n = 113) and transcriptomics analysis of cervicovaginal epithelial cell cultures to examine the ability of lactic acid, a metabolite produced by cervicovaginal lactobacilli, to modulate genital epithelial barrier function.

RESULTS

Compared to women with Lactobacillus-depleted microbiota, women dominated by vaginal lactobacilli exhibit higher abundance of bacterial lactate dehydrogenase, a key enzyme responsible for lactic acid production, which is independently associated with an increased abundance of epithelial barrier proteins. Physiological concentrations of lactic acid enhance epithelial cell culture barrier integrity and increase intercellular junctional molecule expression.

CONCLUSIONS

These findings reveal a novel ability of vaginal lactic acid to enhance genital epithelial barrier integrity that may help prevent invasion by sexually transmitted pathogens. Video abstract.

Evaluation of Modulatory Activities of Lactobacillus crispatus Strains in the Context of the Vaginal Microbiota

It has been widely reported that members of the genus Lactobacillus dominate the vaginal microbiota, which is represented by the most prevalent species Lactobacillus crispatus, Lactobacillus jensenii, Lactobacillus gasseri, and Lactobacillus iners. L. crispatus is furthermore considered an important microbial biomarker due to its professed beneficial implications on vaginal health. In order to identify molecular mechanisms responsible for health-promoting activities that are believed to be elicited by L. crispatus, we performed in silico investigations of the intraspecies biodiversity of vaginal microbiomes followed by in vitro experiments involving various L. crispatus strains along with other vaginal Lactobacillus species mentioned above. Specifically, we assessed their antibacterial activities against a variety of pathogenic microorganisms that are associated with vaginal infections. Moreover, coculture experiments of L. crispatus strains showing the most antibacterial activity against different pathogens revealed distinct ecological fitness and competitive properties with regard to other microbial colonizers. Interestingly, we observed that even phylogenetically closely related L. crispatus strains possess unique features in terms of their antimicrobial activities and associated competitive abilities, which suggests that they exert marked competition and evolutionary pressure within their specific environmental niche. IMPORTANCE The human vaginal microbiota includes all microorganisms that colonize the vaginal tract. In this context, a vaginal microbiota dominated by Lactobacillus and specifically by Lactobacillus crispatus is considered a hallmark of health. The role of L. crispatus in maintaining host health is linked to its modulatory activity toward other members of the vaginal ecosystem and toward the host. In this study, in vitro experiments followed by genetic analyses of the mechanisms used by L. crispatus in colonizing the vaginal ecological niche, particularly in the production of different antimicrobial compounds, were evaluated, highlighting some intriguing novel aspects concerning the genetic variability of this species. Our results indicate that this species has adapted to its niche and may still undergo adaptation to enhance its competitiveness for niche colonization.

Healthy Vaginal Microbiota and Influence of Probiotics Across the Female Life Span

Vaginal microbiota plays a central role in women’s health and reproduction. Vaginal microbiota is dynamic and shaped by hormonal shifts in each stage of a woman’s life from pre-puberty to postmenopause. Current research has mainly focused on vaginal bacterial and fungal members of the community and emphasized their role in disease. However, the impact of balanced vaginal microbiota on health and its interaction with the host is yet poorly understood. High abundance of vaginal lactobacilli is most strongly associated with health, but the concept of health may vary as vaginal dysbiosis may be asymptomatic. Furthermore, there is a lot of variation between ethnic groups in terms of dominating vaginal bacteria. Probiotic lactobacilli could be a safe and natural means to balance and maintain healthy vaginal microbiota. Research evidence is accumulating on their role in supporting women’s health throughout life. This review describes the current literature on vaginal microbiota, the major factors affecting its composition, and how the communities change in different life stages. Furthermore, we focused on reviewing available literature on probiotics and their impact on vaginal microbiota and health.

Bacterial vaginosis and health-associated bacteria modulate the immunometabolic landscape in 3D model of human cervix

Bacterial vaginosis (BV) is an enigmatic polymicrobial condition characterized by a depletion of health-associated Lactobacillus and an overgrowth of anaerobes. Importantly, BV is linked to adverse gynecologic and obstetric outcomes: an increased risk of sexually transmitted infections, preterm birth, and cancer. We hypothesized that members of the cervicovaginal microbiota distinctly contribute to immunometabolic changes in the human cervix, leading to these sequelae. Our 3D epithelial cell model that recapitulates the human cervical epithelium was infected with clinical isolates of cervicovaginal bacteria, alone or as a polymicrobial community. We used Lactobacillus crispatus as a representative health-associated commensal and four common BV-associated species: Gardnerella vaginalis, Prevotella bivia, Atopobium vaginae, and Sneathia amnii. The immunometabolic profiles of these microenvironments were analyzed using multiplex immunoassays and untargeted global metabolomics. A. vaginae and S. amnii exhibited the highest proinflammatory potential through induction of cytokines, iNOS, and oxidative stress-associated compounds. G. vaginalis, P. bivia, and S. amnii distinctly altered physicochemical barrier-related proteins and metabolites (mucins, sialic acid, polyamines), whereas L. crispatus produced an antimicrobial compound, phenyllactic acid. Alterations to the immunometabolic landscape correlate with symptoms and hallmarks of BV and connected BV with adverse women’s health outcomes. Overall, this study demonstrated that 3D cervical epithelial cell colonized with cervicovaginal microbiota faithfully reproduce the immunometabolic microenvironment previously observed in clinical studies and can successfully be used as a robust tool to evaluate host responses to commensal and pathogenic bacteria in the female reproductive tract.

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.

Does probiotics work for bacterial vaginosis and vulvovaginal candidiasis

The different Lactobacillus strains of probiotics have been applied to the treatment and prevention of bacterial vaginosis and vulvovaginal candidiasis. The experimental data demonstrated that it works well via reducing the number of harmful bacteria, maintaining the acidic microenvironment, inhibiting the immune response, and so on, to restore the vaginal microecology. However, the clinical data indicated that it is not sufficient to support the use of probiotics in the intervention of vulvovaginal candidiasis rather than bacterial vaginosis. Hunting for novel probiotic strains and uncovering the precise mechanism of probiotics, especially with the new concept gut-vagina axis, to maintain the homeostasis of vaginal microbiota should be a great challenge in the future.

Lactiplantibacillus plantarum strains isolated from spontaneously fermented cocoa exhibit potential probiotic properties against Gardnerella vaginalis and Neisseria gonorrhoeae

Background

Probiotics are important tools in therapies against vaginal infections and can assist traditional antibiotic therapies in restoring healthy microbiota. Recent research has shown that microorganisms belonging to the genus Lactobacillus have probiotic potential. Thus, this study evaluated the potential in vitro probiotic properties of three strains of Lactiplantibacillus plantarum, isolated during the fermentation of high-quality cocoa, against Gardnerella vaginalis and Neisseria gonorrhoeae. Strains were evaluated for their physiological, safety, and antimicrobial characteristics.

Results

The hydrophobicity of L. plantarum strains varied from 26.67 to 91.67%, and their autoaggregation varied from 18.10 to 30.64%. The co-aggregation of L. plantarum strains with G. vaginalis ranged from 14.73 to 16.31%, and from 29.14 to 45.76% with N. gonorrhoeae. All L. plantarum strains could moderately or strongly produce biofilms. L. plantarum strains did not show haemolytic activity and were generally sensitive to the tested antimicrobials. All lactobacillus strains were tolerant to heat and pH resistance tests. All three strains of L. plantarum showed antimicrobial activity against the tested pathogens. The coincubation of L. plantarum strains with pathogens showed that the culture pH remained below 4.5 after 24 h. All cell-free culture supernatants (CFCS) demonstrated activity against the two pathogens tested, and all L. plantarum strains produced hydrogen peroxide. CFCS characterisation in conjunction with gas chromatography revealed that organic acids, especially lactic acid, were responsible for the antimicrobial activity against the pathogens evaluated.

Conclusion

The three strains of L. plantarum presented significant probiotic characteristics against the two pathogens of clinical importance. In vitro screening identified strong probiotic candidates for in vivo studies for the treatment of vaginal infections.

The association between obesity and weight loss after bariatric surgery on the vaginal microbiota

BACKGROUND

Obesity and vaginal microbiome (VMB) dysbiosis are each risk factors for adverse reproductive and oncological health outcomes in women. Here, we investigated the relationship between obesity, vaginal bacterial composition, local inflammation and bariatric surgery.

METHODS

Vaginal bacterial composition assessed by high-throughput sequencing of bacterial 16S rRNA genes and local cytokine levels measured using a multiplexed Magnetic Luminex Screening Assay were compared between 67 obese and 42 non-obese women. We further assessed temporal changes in the microbiota and cytokines in a subset of 27 women who underwent bariatric surgery.

RESULTS

The bacterial component of the vaginal microbiota in obese women was characterised by a lower prevalence of a Lactobacillus-dominant VMB and higher prevalence of a high diversity (Lactobacillus spp., and Gardnerella- spp. depleted) VMB, compared with non-obese subjects (p<0.001). Obese women had higher relative abundance of Dialister species (p<0.001), Anaerococcus vaginalis (p=0.021), and Prevotella timonensis (p=0.020) and decreased relative abundance of Lactobacillus crispatus (p=0.014). Local vaginal IL-1β, IL-4, IL-6, IL-8, IFNγ, MIP-1α and TNFα levels were all higher among obese women, however, only IL-1β and IL-8 correlated with VMB species diversity. In a subset of obese women undergoing bariatric surgery, there were no significant overall differences in VMB following surgery; however, 75% of these women remained obese at 6 months. Prior to surgery, there was no relationship between body mass index (BMI) and VMB structure; however, post-surgery women with a Lactobacillus-dominant VMB had a significantly lower BMI than those with a high diversity VMB.

CONCLUSIONS

Obese women have a significantly different vaginal microbiota composition with increased levels of local inflammation compared to non-obese women. Bariatric surgery does not change the VMB; however, those with the greatest weight loss 6-month post-surgery are most likely to have a Lactobacillus-dominant VMB. Video abstract.

Association between vaginal microbiota and risk of early pregnancy miscarriage

Approximately 15 % of clinically recognized pregnancies end in miscarriage. To explore the vaginal microbiota profile in women diagnosed with early pregnancy miscarriage (including missed miscarriage [M] or empty-sac miscarriage [E]), the microbial community structure in vaginal fluid was evaluated by Illumina MiSeq sequencing of the 16S rRNA gene V4 region and compared with that in women with normal pregnancy (P). Taxa identified in samples from the P, E, and M groups formed distinct clusters. The M group had the highest bacterial species richness and diversity, with lower Lactobacillus levels and higher Bacteroides, Halomonas, Miscellaneous-Crenarchaeota, Bacillus, Staphylococcus, Escherichia/Shigella, and Acetobacter levels than in the other two groups. The vaginal community-state types differed significantly among the three groups (P = 0.02) but were similar between the P and E groups (P = 0.21). Moreover, we identified an optimal marker set composed of 12 operational taxonomic units based on a random forest model that distinguished the M and P groups, with areas under the receiver-operating characteristic curve of 86.76 % and 93.33 % in the training and test groups, respectively. In conclusion, this study highlights that patients with early pregnancy miscarriage had a significantly different vaginal microbiota profile. Microbial markers analyzed by RT-qPCR may be applied for the etiological diagnosis of miscarriage. Further studies should be performed to elucidate the possible mechanism of special strains affecting miscarriage during early pregnancy.

Gardnerella vaginalis and Neisseria gonorrhoeae Are Effectively Inhibited by Lactobacilli with Probiotic Properties Isolated from Brazilian Cupuaçu (Theobroma grandiflorum) Fruit

In recent years, certain Lactobacillus sp. have emerged in health care as an alternative therapy for various diseases. Based on this, this study is aimed at evaluating in vitro the potential probiotics of five lactobacilli strains isolated from pulp of cupuaçu fruit fermentation against Gardnerella vaginalis and Neisseria gonorrhoeae. Our lactobacilli strains were classified as safe for use in humans, and they were tolerant to heat and pH. Our strains were biofilm producers, while hydrophobicity and autoaggregation varied from 13% to 86% and 13% to 25%, respectively. The coaggregation of lactobacilli used in this study with G. vaginalis and N. gonorrhoeae ranged from 15% to 36% and 32% to 52%, respectively. Antimicrobial activity was present in all tested Lactobacillus strains against both pathogens, and the growth of pathogens in coculture was reduced by the presence of our lactobacilli. Also, all tested lactobacilli reduced the pH of the culture, even in incubation with pathogens after 24 hours. The cell-free culture supernatants (CFCS) of all five lactobacilli demonstrated activity against the two pathogens with a halo presence and CFCS characterization assay together with gas chromatography revealed that lactic acid was the most abundant organic acid in the samples (50% to 62%). Our results demonstrated that the organic acid production profile is strain-specific. This study revealed that cupuaçu is a promising source of microorganisms with probiotic properties against genital pathogens. We demonstrated by in vitro tests that our Lactobacillus strains have probiotic properties. However, the absence of in vivo tests is a limitation of our work due to the need to evaluate the interaction of our lactobacilli with pathogens in the vaginal mucosa. We believe that these findings may be useful in developing a product containing our lactobacilli and their supernatants in order to support with vaginal health.

The Complex Link between the Female Genital Microbiota, Genital Infections, and Inflammation

The female genital tract microbiota is part of a complex ecosystem influenced by several physiological, genetic, and behavioral factors. It is uniquely linked to a woman's mucosal immunity and plays a critical role in the regulation of genital inflammation. A vaginal microbiota characterized by a high abundance of lactobacilli and low overall bacterial diversity is associated with lower inflammation. On the other hand, a more diverse microbiota is linked to high mucosal inflammation levels, a compromised genital epithelial barrier, and an increased risk of sexually transmitted infections and other conditions. Several bacterial taxa such as Gardnerella spp., Prevotella spp., Sneathia spp., and Atopobium spp. are well known to have adverse effects; however, the definitive cause of this microbial dysbiosis is yet to be fully elucidated. The aim of this review is to discuss the multiple ways in which the microbiota influences the overall genital inflammatory milieu and to explore the causes and consequences of this inflammatory response. While there is abundant evidence linking a diverse genital microbiota to elevated inflammation, understanding the risk factors and mechanisms through which it affects genital health is essential. A robust appreciation of these factors is important for identifying effective prevention and treatment strategies.

Nutrition in Gynecological Diseases: Current Perspectives

Diet and nutrition are fundamental in maintaining the general health of populations, including women’s health. Health status can be affected by nutrient deficiency and vice versa. Gene–nutrient interactions are important contributors to health management and disease prevention. Nutrition can alter gene expression, as well as the susceptibility to diseases, including cancer, through several mechanisms. Gynecological diseases in general are diseases involving the female reproductive system and include benign and malignant tumors, infections, and endocrine diseases. Benign diseases such as uterine fibroids and endometriosis are common, with a negative impact on women’s quality of life, while malignant tumors are among the most common cause of death in the recent years. In this comprehensive review article, a bibliographic search was performed for retrieving information about nutrients and how their deficiencies can be associated with gynecological diseases, namely polycystic ovary syndrome, infertility, uterine fibroids, endometriosis, dysmenorrhea, and infections, as well as cervical, endometrial, and ovarian cancers. Moreover, we discussed the potential beneficial impact of promising natural compounds and dietary supplements on alleviating these significant diseases.

Comparative genome analyses of Lactobacillus crispatus isolated from different ecological niches reveal an environmental adaptation of this species to the human vaginal environment

Vaginal microbiota is defined as the community of bacteria residing in the human vaginal tract. Recent studies have demonstrated that the vaginal microbiota is dominated by members of the Lactobacillus genus, whose relative abundance and microbial taxa composition are dependent on the healthy status of this human body site. Particularly, among members of this genus, the high prevalence of Lactobacillus crispatus is commonly associated with a healthy vaginal environment. In the current study, we assessed the microbial composition of 94 healthy vaginal microbiome samples through shotgun metagenomics analyses. Based on our results we observed that L. crispatus was the most representative species and correlated negatively with bacteria involved in vaginal infections. Therefore, we isolated fifteen L. crispatus strains from different environments in which this species is abounding, ranging from vaginal swabs of healthy women to chicken fecal samples. The genomes of these strains were decoded and their genetic content was analyzed and correlated with their physiological features. An extensive comparative genomic analysis encompassing all publicly available genome sequences of L. crispatus and combined with those decoded in this study, revealed a genetic adaptation of strains to their ecological niche. In addition, in vitro growth experiments involving all isolated L. crispatus strains together with a synthetic vaginal microbiota reveal how this species is able to modulate the composition of the vaginal microbial consortia at strain level. Overall, our findings suggest that L. crispatus plays an important ecological role in reducing the complexity of the vaginal microbiota by depleting pathogenic bacteria.Importance The vaginal microbiota is defined as the community of bacteria residing in the human vaginal tract. Recent studies have demonstrated that the high prevalence of Lactobacillus crispatus species is commonly associated with a healthy vaginal environment. In the current study, we assessed the microbial composition of 94 public healthy vaginal samples through shotgun metagenomics analyses. Results showed that L. crispatus was the most representative species and correlated negatively with bacteria involved in vaginal infections. Moreover, we isolated and sequenced the genome of new L. crispatus strains from different environments and the comparative genomics analysis revealed a genetic adaptation of strains to their ecological niche. In addition, in-vitro growth experiments display the capability of this species to modulate the composition of the vaginal microbial consortia. Overall, our findings suggest an ecological role exploited by L. crispatus in reducing the complexity of the vaginal microbiota toward a depletion of pathogenic bacteria.

Liver bioengineering: Recent trends/advances in decellularization and cell sheet technologies towards translation into the clinic

Development of novel technologies provides the best tissue constructs engineering and maximizes their therapeutic effects in regenerative therapy, especially for liver dysfunctions. Among the currently investigated approaches of tissue engineering, scaffold-based and scaffold-free tissues are widely suggested for liver regeneration. Analogs of liver acellular extracellular matrix (ECM) are utilized in native scaffolds to increase the self-repair and healing ability of organs. Native ECM analog could improve liver repairing through providing the supportive framework for cells and signaling molecules, exerting normal biomechanical, biochemical, and physiological signal complexes. Recently, innovative cell sheet technology is introduced as an alternative for conventional tissue engineering with the advantage of fewer scaffold restrictions and cell culture on a Thermo-Responsive Polymer Surface. These sheets release the layered cells through a temperature-controlled procedure without enzymatic digestion, while preserving the cell-ECM contacts and adhesive molecules on cell-cell junctions. In addition, several novelties have been introduced into the cell sheet and decellularization technologies to aid cell growth, instruct differentiation/angiogenesis, and promote cell migration. In this review, recent trends, advancements, and issues linked to translation into clinical practice are dissected and compared regarding the decellularization and cell sheet technologies for liver tissue engineering.

Vaginal microbiota diversity and paucity of Lactobacillus species are associated with persistent hrHPV infection in HIV negative but not in HIV positive women

The vaginal microbiota is thought to play a role in modulating risk of high-risk human papillomavirus (hrHPV) infection. We examined the relationship between the vaginal microbiota and persistent hrHPV infection in HIV-negative and HIV-positive women. We used 16S-rRNA sequencing to characterize the vaginal microbiota of two serial samples taken six months apart from 211 Nigerian women (67%, 142/211 HIV-positive and 33%, 69/211 HIV-negative) and evaluated the association between the vaginal microbiota and persistent hrHPV infection using generalized estimating equation logistic regression models and linear discriminant analysis effect size (LEfSe) algorithm to identify phylotypic biomarkers of persistent hrHPV infection. The high diversity microbiota, Community State Type IV-B, was the most prevalent in both HIV-negative (38% at baseline, 30% at the follow-up visit) and HIV-positive (27% at baseline, 35% at the follow-up visit) women. The relationship between the vaginal microbiota and persistent hrHPV was modified by HIV status. In HIV-negative women, women with Lactobacillus dominant microbiota had lower odds (OR: 0.35, 95% CI 0.14-0.89, p = 0.03) of persistent hrHPV compared to women with Lactobacillus deficient microbiota. While among HIV-positive women, the odds of being persistently infected with hrHPV was higher in women with Lactobacillus dominant microbiota (OR: 1.25, 95% CI 0.73-2.14 p = 0.41). This difference in effect estimates by HIV was statistically significant (p = 0.02). A high diversity vaginal microbial community with paucity of Lactobacillus species was associated with persistent hrHPV infection in HIV-negative women but not in HIV-positive women.

Probiotics and the envisaged role in treating human infertility

Background

Considerable attention is being directed nowadays towards using probiotics as an alternative therapy in treating several human diseases including gastrointestinal tract diseases especially colorectal cancers, cardiovascular diseases, hyperlipidemia, and blood pressure cases. However, infertility as affected by the microbiome and the probable role of probiotics in alleviating infertility problems did not receive the deserved attention, especially in IVF patients with male or female factors.

Main body

In this review, we tried to draw the attention of researchers in the medical settings to the importance of the forthcoming role of probiotics use in elucidating the role of the microbiome in infertile patients. The hope is to attain the best performance of both male and female reproductive systems and to shed some light on infertility problems.

Conclusion

More in vivo experiments are still needed to address many aspects of probiotics like proper administration, exact functional strains, required dose, application method, duration of treatment, and combination with antibiotics before considering probiotics as an alternative treatment.

Human Gut Commensal Membrane Vesicles Modulate Inflammation by Generating M2-like Macrophages and Myeloid-Derived Suppressor Cells

Immunomodulatory commensal bacteria modify host immunity through delivery of regulatory microbial-derived products to host cells. Extracellular membrane vesicles (MVs) secreted from symbiont commensals represent one such transport mechanism. How MVs exert their anti-inflammatory effects or whether their tolerance-inducing potential can be used for therapeutic purposes remains poorly defined. In this study, we show that MVs isolated from the human lactic acid commensal bacteria Pediococcus pentosaceus suppressed Ag-specific humoral and cellular responses. MV treatment of bone marrow-derived macrophages and bone marrow progenitors promoted M2-like macrophage polarization and myeloid-derived suppressor cell differentiation, respectively, most likely in a TLR2-dependent manner. Consistent with their immunomodulatory activity, MV-differentiated cells upregulated expression of IL-10, arginase-1, and PD-L1 and suppressed the proliferation of activated T cells. MVs' anti-inflammatory effects were further tested in acute inflammation models in mice. In carbon tetrachloride-induced fibrosis and zymosan-induced peritonitis models, MVs ameliorated inflammation. In the dextran sodium sulfate-induced acute colitis model, systemic treatment with MVs prevented colon shortening and loss of crypt architecture. In an excisional wound healing model, i.p. MV administration accelerated wound closure through recruitment of PD-L1-expressing myeloid cells to the wound site. Collectively, these results indicate that P. pentosaceus-derived MVs hold promise as therapeutic agents in management/treatment of inflammatory conditions.

Microbial interactions in the mosquito gut determine Serratia colonization and blood-feeding propensity

How microbe–microbe interactions dictate microbial complexity in the mosquito gut is unclear. Previously we found that, Serratia, a gut symbiont that alters vector competence and is being considered for vector control, poorly colonized Aedes aegypti yet was abundant in Culex quinquefasciatus reared under identical conditions. To investigate the incompatibility between Serratia and Ae. aegypti, we characterized two distinct strains of Serratia marcescens from Cx. quinquefasciatus and examined their ability to infect Ae. aegypti. Both Serratia strains poorly infected Ae. aegypti, but when microbiome homeostasis was disrupted, the prevalence and titers of Serratia were similar to the infection in its native host. Examination of multiple genetically diverse Ae. aegypti lines found microbial interference to S. marcescens was commonplace, however, one line of Ae. aegypti was susceptible to infection. Microbiome analysis of resistant and susceptible lines indicated an inverse correlation between Enterobacteriaceae bacteria and Serratia, and experimental co-infections in a gnotobiotic system recapitulated the interference phenotype. Furthermore, we observed an effect on host behavior; Serratia exposure to Ae. aegypti disrupted their feeding behavior, and this phenotype was also reliant on interactions with their native microbiota. Our work highlights the complexity of host–microbe interactions and provides evidence that microbial interactions influence mosquito behavior.

Concentrative Nucleoside Transporter 3 Is Located on Microvilli of Vaginal Epithelial Cells

Transporters are specialized integral membrane proteins, which mediate the passage of virtually all molecules through cell membranes. They are expressed in a broad range of human and animal tissues and play important roles in both normal and disease states. For these reasons, they are evaluated when developing and testing drugs. Two major families of drug transporters, the adenosine 5'-triphosphate-binding cassette and solute carrier transporters (SLC), have critical roles in the absorption, distribution, metabolism, and elimination of drugs. The SLC family contains known nucleoside transporters and therefore are important when nucleoside analogs are used as drugs to prevent or treat viral infections. In this study, we wanted to determine if it was possible to locate one member of the SLC family, the human concentrative nucleoside transporter 3 (CNT3) in human vaginal epithelial cells. The CNT3 protein has important roles in drug delivery, subsequent drug tissue distribution, and, hence, efficacy. Vaginal epithelial cells, taken from two human volunteers (one Caucasian and one African American), were labeled for light and electron microscopy, with a commercial antibody to a cytoplasmic domain of CNT3, the protein product of the SLC28A3 gene. Fluorescent secondary antibodies or protein A-gold were used to detect antibody binding. By electron microscopy, gold particle binding was quantified to determine labeling specificity. By light microscopy, positive labeling with anti-CNT3 antibodies was detected on human vaginal epithelial cells, but specificity to any intracellular structure was not easily determined, most likely a result of specimen preparation. Electron microscopy revealed that the CNT3 transporter protein was present predominantly on microvilli located on one side of some human vaginal epithelial cells. Quantification confirmed specific anti-CNT3 labeling over human vaginal epithelial cell microvilli. The CNT3 protein, present in the microvilli of human vaginal epithelial cells, may have a role in redistributing nucleoside homologues delivered to the vaginal tract. Transporter proteins such as CNT3 could shuttle nucleosides and their analogs through the vaginal epithelium to immune cells located in lower cell layers. Outer layers of cells, which are eventually shed from the epithelium, may remove accumulated nucleoside drug analogs from the vaginal tract.

Activation of Toll-Like Receptors Differentially Modulates Inflammation in the Human Reproductive Tract: Preliminary Findings

The female reproductive tract (FRT) is the main site of entry of sexually transmitted infections (STIs). Toll-like receptors (TLRs) that recognize pathogenic motifs are widely expressed in the FRT. TLR stimulation induces immune activation and local production of inflammatory mediators. In the FRT, this response should also be compatible with reproductive functions and symbiosis with host microbiota. With a view to develop efficient mucosal vaccines to prevent STI acquisition, the role of TLR ligands in the FRT needs to be explored. We have therefore investigated the cytokine profiles of the different compartments of the FRT (vagina, endocervix, ectocervix, and uterus) before and after stimulation of mononuclear cells from human tissue specimens. The comparison with PBMCs allowed us to highlight the FRT specificities. We first characterized the main immune cell populations in each compartment and observed that their distribution was different through the compartments. The CD45⁺ cells represented a maximum of 11% in the FRT in contrast to 96% in PBMCs. We identified two main populations among the CD45⁺ cells in the four compartments of the FRT: CD3⁺ T cells (CD4⁺ and CD8⁺) and CD14⁺ APCs. B cell populations (CD19⁺) were much less frequent than T cells in all the FRT regions and were equally distributed. NK CD56⁺ cells were detected in all compartments and were more abundant in the uterus. Stimulation of the mononuclear cells was then performed with TLR agonists: R848 for TLR7/8, Poly I:C for TLR3, LPS for TLR4 and ODN CpG for TLR9. Cytokine levels in unstimulated cultures of cells isolated from all FRT compartments were higher than in cultures of unstimulated PBMCs. In contrast, after stimulation with TLR agonists, cytokine responses induced by TLR agonists were moderate in the FRT and significantly lower than in PBMCs. These responses were varied with different TLR ligands and FRT compartments. The cytokine profile induced by TLR activation in the FRT supports the role of these tissues in genital anti-microbial immunity and in the control of inflammation while allowing maintenance of its reproductive function.

Vaginal Microbiota and HPV Infection: Novel Mechanistic Insights and Therapeutic Strategies

Cervical cancer is a global public health concern. The complex interaction of genetic and environmental factors is critical for the progress of cervical cancer. Growing evidence suggests that microbes, human papillomavirus (HPV), and the immune system interact closely with each other to govern homeostasis of the vaginal environment and the health of the lower genital tract of females. Certain vaginal microbial strains may play either a protective or a pathogenic role in carcinogenesis of the cervix after HPV persistent infection. Probiotics can therefore present a putative therapeutic approach for cervical cancer. However, work in this field remains limited. Recent technological developments have allowed us to identify microbes and their products using culture-independent molecular detection techniques. In this review, we discuss the composition of the vaginal bacterial community, its commensal flora and the protective impact this has on the health of the female genital tract. This review will also describe critical immune factors in lower genital tract health and summarize the role of the vaginal microbiota in cervical carcinogenesis. Knowledge in this field has provided researchers with the clues and tools to propose the use of probiotics as a potential line of treatment for cervical cancer and has provided valuable insights into host–pathogen interaction dynamics within the female genital tract.

Inflammatory and antimicrobial properties differ between vaginal Lactobacillus isolates from South African women with non-optimal versus optimal microbiota

Female genital tract (FGT) inflammation increases HIV infection susceptibility. Non-optimal cervicovaginal microbiota, characterized by depletion of Lactobacillus species and increased bacterial diversity, is associated with increased FGT cytokine production. Lactobacillus species may protect against HIV partly by reducing FGT inflammation. We isolated 80 lactobacilli from South African women with non-optimal (Nugent 4–10; n = 18) and optimal microbiota (Nugent 0–3; n = 14). Cytokine production by vaginal epithelial cells in response to lactobacilli in the presence and absence of Gardnerella vaginalis was measured using Luminex. Adhesion to vaginal epithelial cells, pH, D/L-lactate production and lactate dehydrogenase relative abundance were assessed. Lactobacilli from women with non-optimal produced less lactic acid and induced greater inflammatory cytokine production than those from women with optimal microbiota, with IL-6, IL-8, IL-1α, IL-1β and MIP-1α/β production significantly elevated. Overall, lactobacilli suppressed IL-6 (adjusted p < 0.001) and IL-8 (adjusted p = 0.0170) responses to G. vaginalis. Cytokine responses to the lactobacilli were inversely associated with lactobacilli adhesion to epithelial cells and D-lactate dehydrogenase relative abundance. Thus, while cervicovaginal lactobacilli reduced the production of the majority of inflammatory cytokines in response to G. vaginalis, isolates from women with non-optimal microbiota were more inflammatory and produced less lactic acid than isolates from women with optimal microbiota.

The Interplay Between Reproductive Tract Microbiota and Immunological System in Human Reproduction

In the last decade, the microbiota, i.e., combined populations of microorganisms living inside and on the surface of the human body, has increasingly attracted attention of researchers in the medical field. Indeed, since the completion of the Human Microbiome Project, insight and interest in the role of microbiota in health and disease, also through study of its combined genomes, the microbiome, has been steadily expanding. One less explored field of microbiome research has been the female reproductive tract. Research mainly from the past decade suggests that microbial communities residing in the reproductive tract represent a large proportion of the female microbial network and appear to be involved in reproductive failure and pregnancy complications. Microbiome research is facing technological and methodological challenges, as detection techniques and analysis methods are far from being standardized. A further hurdle is understanding the complex host-microbiota interaction and the confounding effect of a multitude of constitutional and environmental factors. A key regulator of this interaction is the maternal immune system that, during the peri-conceptional stage and even more so during pregnancy, undergoes considerable modulation. This review aims to summarize the current literature on reproductive tract microbiota describing the composition of microbiota in different anatomical locations (vagina, cervix, endometrium, and placenta). We also discuss putative mechanisms of interaction between such microbial communities and various aspects of the immune system, with a focus on the characteristic immunological changes during normal pregnancy. Furthermore, we discuss how abnormal microbiota composition, “dysbiosis,” is linked to a spectrum of clinical disorders related to the female reproductive system and how the maternal immune system is involved. Finally, based on the data presented in this review, the future perspectives in diagnostic approaches, research directions and therapeutic opportunities are explored.

How the Cervical Microbiota Contributes to Cervical Cancer Risk in Sub-Saharan Africa

Despite ongoing efforts, sub-Saharan Africa faces a higher cervical cancer burden than anywhere else in the world. Besides HPV infection, definitive factors of cervical cancer are still unclear. Particular states of the cervicovaginal microbiota and viral infections are associated with increased cervical cancer risk. Notably, HIV infection, which is prevalent in sub-Saharan Africa, greatly increases risk of cervicovaginal dysbiosis and cervical cancer. To better understand and address cervical cancer in sub-Saharan Africa, a better knowledge of the regional cervicovaginal microbiome is required This review establishes current knowledge of HPV, HIV, cervicovaginal infections, and the cervicovaginal microbiota in sub-Saharan Africa. Because population statistics are not available for the region, estimates are derived from smaller cohort studies. Microbiota associated with cervical inflammation have been found to be especially prevalent in sub-Saharan Africa, and to associate with increased cervical cancer risk. In addition to high prevalence and diversity of HIV and HPV, intracellular bacterial infections such as Chlamydia, Gonorrhea, and Mycoplasma hominis are much more common than in regions with a low burden of cervical cancer. This suggests the prevalence of cervical cancer in sub-Saharan Africa may be partially attributed to increased cervical inflammation resulting from higher likelihood of cervical infection and/or microbial dysbiosis.

S-layer protein 2 of Lactobacillus crispatus 2029, its structural and immunomodulatory characteristics and roles in protective potential of the whole bacteria against foodborne pathogens

We have previously demonstrated that human vaginal Lactobacillus crispatus 2029 (LC2029) strain is highly adhesive to cervicovaginal epithelial cells, exhibits antagonistic activity against genitourinary pathogens and expresses surface-layer protein (Slp). The aims of the present study were elucidation of Slp structural and immunomodulatory characteristics and its roles in protective properties of the whole vaginal LC2029 bacteria against foodborne pathogens. Enteric Caco-2 and colon HT-29 cell lines were used as the in vitro models of the human intestinal epithelial layer. LC2029 strain has two homologous surface-layer (S-layer) genes, slp1 and slp2. Whilst we found no evidence for the expression of slp1 under the growth conditions used, a very high level of expression of the slp2 gene was detected. C-terminal part of the amino sequence of Slp2 protein was found to be highly similar to that of the conserved C-terminal region of SlpA protein of L. crispatus Zj001 isolated from pig intestines and CbsA protein of L. crispatus JCM5810 isolated from chicken intestines, and was substantially variable at the N-terminal and middle regions. The amino acid sequence identity between SlpA and CbsA was as high as 84%, whilst the identity levels of these sequences with that of Slp2 were only 49% and 50% (respectively). LC2029 strain was found to be both acid and bile tolerant. Survival in simulated gastric and intestinal juices of LC2029 cells unable to produce Slp2 was reduced by 2-3 logs. Vaginal L. crispatus 1385 (LC1385) strain not expressing Slp was also very sensitive to gastric and intestinal stresses. Slp2 was found to be non-covalently bound to the surface of the bacterium, acting as an adhesin and facilitating interaction of LC2029 lactobacilli with the host immature or fully differentiated Caco-2 cells, as well as HT-29 cells. No toxicity to or damage of Caco-2 or HT-29 epithelial cells were detected after 24 h of colonization by LC2029 lactobacilli. Both Slp2 protein and LC2029 cells induced NF-kB activation in Caco-2 and HT-29 cells, but did not induce expression of innate immunity mediators Il-8, Il-1β, and TNF-α. Slp2 and LC2029 inhibited Il-8 production in Caco-2 and HT-29 cells induced by MALP-2 and increased production of anti-inflammatory cytokine Il-6. Slp2 inhibited production of CXCL1 and RANTES by Caco-2 cells during differentiation and maturation process within 15 days. Culturing Caco-2 and HT-29 cells in the presence of Slp2 increased adhesion of bifidobacteria BLI-2780 to these enterocytes. Upon binding to Caco-2 and HT-29 cells, Slp2 protein and LC2029 lactobacilli were recognized by toll-like receptors (TLR) 2/6. It was shown that LC2029 strain is a strong co-aggregator of foodborne pathogens Campylobacter jejuni, Salmonella enteritidis, and Escherichia coli O157:H used in this study. The Slp2 was responsible for the ability of LC2029 to co-aggregate these enteropathogens. Slp2 and intact LC2029 lactobacilli inhibited foodborne pathogen-induced activation of caspase-9 and caspase-3 as apoptotic biomarkers in Caco-2 and HT-29 cells. In addition, Slp2 and Slp2-positive LC2029 strain reduced adhesion of tested pathogenic bacteria to Caco-2 and HT-29 cells. Slp2-positive LC2029 strain but not Slp2 alone provided bactericidal effect on foodborne pathogens. These results suggest a range of mechanisms involved in inhibition of growth, viability, and cell-adhesion properties of pathogenic Proteobacteria by the Slp2 producing LC2029, which may be useful in treatment of necrotizing enterocolitis (NEC) in newborns and foodborne infectious diseases in children and adults, increasing the colonization resistance and maintaining the intestinal homeostasis.

Distinct Immune Responses Elicited From Cervicovaginal Epithelial Cells by Lactic Acid and Short Chain Fatty Acids Associated With Optimal and Non-optimal Vaginal Microbiota

Non-optimal vaginal microbiota, as observed in bacterial vaginosis (BV), is typically characterized by a depletion of beneficial lactobacilli and an abundance of numerous anaerobes. These non-optimal conditions are associated with subclinical cervicovaginal inflammation and an increased risk of HIV infection compared to women colonized with optimal vaginal microbiota dominated by lactobacilli. Lactic acid (LA) is a major organic acid metabolite produced by vaginal lactobacilli that elicits anti-inflammatory effects from cervicovaginal epithelial cells and is dramatically depleted during BV. However, it is unclear if LA retains its anti-inflammatory activity in the presence of vaginal microbiota metabolites comprising short chain fatty acids (SCFAs) and succinic acid, which are also produced by an optimal vaginal microbiota. Furthermore, the immunomodulatory effect of SCFAs and succinic acid on cervicovaginal epithelial cells at higher concentrations present during BV is unknown. Here we report that in the presence of physiologically relevant concentrations of SCFAs and succinic acid at pH 3.9 (as found in women with lactobacillus-dominated microbiota) LA induced an anti-inflammatory state in cervicovaginal epithelial cells and inhibited inflammation elicited by the toll-like receptor (TLR) agonists polyinosinic:polycytidylic acid and Pam3CSK4. When cervicovaginal epithelial cells were treated with a vaginal microbiota metabolite mixture representative of BV, containing a lower concentration of LA but higher concentrations of SCFA/succinic acid at pH 7, no anti-inflammatory was observed. Rather, the vaginal microbiota metabolite mixture representative of BV dysregulated the immune response of cervicovaginal epithelial cells during prolonged and sustained treatments. This was evidenced by increased basal and TLR-induced production of pro-inflammatory cytokines including tumor necrosis factor-α, but decreased basal production of chemokines including RANTES and IP-10. Further characterization of individual components of the BV vaginal microbiota mixture suggested that acetic acid is an important vaginal microbiota metabolite capable of eliciting diverse immunomodulatory effects on a range of cervicovaginal epithelial cell targets. These findings indicate that elevated levels of SCFAs are a potential source of cervicovaginal inflammation in women experiencing BV, and support the unique anti-inflammatory properties of LA on cervicovaginal epithelial cells as well as a role for LA or LA-producing lactobacilli to reverse genital inflammation associated with increased HIV risk.

Extracellular vesicles from symbiotic vaginal lactobacilli inhibit HIV-1 infection of human tissues

The vaginal microbiota, dominated by Lactobacillus spp., plays a key role in preventing HIV-1 transmission. Here, we investigate whether the anti-HIV effect of lactobacilli is mediated by extracellular vesicles (EVs) released by these bacteria. Human cervico-vaginal and tonsillar tissues ex vivo, and cell lines were infected with HIV-1 and treated with EVs released by lactobacilli isolated from vaginas of healthy women. EVs released by L. crispatus BC3 and L. gasseri BC12 protect tissues ex vivo and isolated cells from HIV-1 infection. This protection is associated with a decrease of viral attachment to target cells and viral entry due to diminished exposure of Env that mediates virus-cell interactions. Inhibition of HIV-1 infection is associated with the presence in EVs of several proteins and metabolites. Our findings demonstrate that the protective effect of Lactobacillus against HIV-1 is, in part, mediated by EVs released by these symbiotic bacteria. If confirmed in vivo, this finding may lead to new strategies to prevent male-to-female sexual HIV-1 transmission.

Lactobacillus associates with vaginal protection from HIV-1 infection. Here, the authors show that lactobacilli extracellular vesicles contain bacterial proteins and metabolites that inhibit HIV-1 infection in T cells and in human cervico-vaginal and tonsillar tissues ex vivo via altering viral Env proteins.

Development of a Novel ex vivo Nasal Epithelial Cell Model Supporting Colonization With Human Nasal Microbiota

The nasal mucosa provides first line defense against inhaled pathogens while creating a unique microenvironment for bacterial communities. Studying the impact of microbiota in the nasal cavity has been difficult due to limitations with current models including explant cultures, primary cells, or neoplastic cell lines. Most notably, none have been shown to support reproducible colonization by bacterial communities from human donors. Therefore, to conduct controlled studies of the human nasal ecosystem, we have developed a novel ex vivo mucosal model that supports bacterial colonization of a cultured host mucosa created by immortalized human nasal epithelial cells (NEC). For this model, immortalized NEC established from 5 male and 5 female donors were cultured with an air-interfaced, apical surface on a porous transwell membrane. NEC were grown from nasal turbinate tissues harvested from willed bodies or from discarded tissue collected during sinonasal procedures. Immortalized cells were evaluated through molecular verification of cell type, histological confirmation of tissue differentiation including formation of tight junctions, NEC multilayer viability, metabolism, physiology and imaging of the luminal surface by scanning electron microscopy. Results showed proper differentiation and multilayer formation at seven to 10 days after air interface that was maintained for up to 3 weeks. The optimized mucosal cultures created an environment necessary to sustain colonization by nasal microbiomes (NMBs) that were collected from healthy volunteers, cryogenically preserved and characterized with customized quantitative polymerase chain reaction (qPCR) arrays. Polymicrobial communities of nasal bacteria associated with healthy and inflamed states were consistently reproduced in matured NEC co-cultures by transplant of NMBs from multiple community types. The cultured NMBs were stable after an initial period of bacterial replication and equilibration. This novel ex vivo culture system is the first model that supports controlled cultivation of NMBs, allowing for lab-based causation studies and further experimentation to explore the complexities of host-microbe and microbe-microbe interactions.

Antimicrobial and inflammatory properties of South African clinical Lactobacillus isolates and vaginal probiotics

Bacterial vaginosis (BV) causes genital inflammation and increased HIV acquisition risk. The standard-of-care for BV, antibiotic therapy, is associated with high recurrence rates. Probiotics may improve treatment outcomes, although substantial heterogeneity in efficacy has been observed during clinical trials. To evaluate the potential to improve existing probiotics, we compared the inflammatory and antimicrobial (adhesion, H₂O₂, D-lactate and L-lactate production) characteristics of 23 vaginal Lactobacillus isolates from South African women, commercial vaginal probiotics (L. casei rhamnosus, L. acidophilus) and 4 reference strains. All lactobacilli induced inflammatory cytokine production by genital epithelial cells and produced D-lactate. Of six isolates assessed, five suppressed inflammatory responses to Gardnerella vaginalis. Although the L. acidophilus probiotic was the most adherent, many clinical isolates produced greater amounts of H₂O₂, D-lactate and L-lactate than the probiotics. The most L-lactate and H₂O₂ were produced by L. jensenii (adjusted p = 0.0091) and L. mucosae (adjusted p = 0.0308) species, respectively. According to the characteristics evaluated, the top 10 isolates included 4 L. jensenii, 2 L. crispatus, 1 L. mucosae, 1 L. vaginalis and the L. acidophilus probiotic. There is potential to develop an improved vaginal probiotic using clinical Lactobacillus isolates. Inflammatory profiles are critical to evaluate as some isolates induced substantial cytokine production.

Cultivated Human Vaginal Microbiome Communities Impact Zika and Herpes Simplex Virus Replication in ex vivo Vaginal Mucosal Cultures

The human vaginal microbiome (VMB) is a complex bacterial community that interacts closely with vaginal epithelial cells (VECs) impacting the mucosal phenotype and its responses to pathogenic insults. The VMB and VEC relationship includes nutrient exchange and regulation of signaling molecules that controls numerous host functions and defends against invading pathogens. To better understand infection and replication of sexually transmitted viral pathogens in the human vaginal mucosa we used our ex vivo VEC multilayer culture system. We tested the hypothesis that selected VMB communities could be identified that alter the replication of sexually transmitted viruses consistent with reported clinical associations. Sterile VEC multilayer cultures or those colonized with VMB dominated by specific Lactobacillus spp., or VMB lacking lactobacilli, were infected with Zika virus, (ZIKV) a single stranded RNA virus, or Herpes Simplex Virus type 2 (HSV-2), a double stranded DNA virus. The virus was added to the apical surface of the cultured VEC multilayer to model transmission during vaginal intercourse. Viral replication was measured 48 h later by qPCR. The results indicated that VEC cultures colonized by VMB containing Staphylococcus spp., previously reported as inflammatory, significantly reduced the quantity of viral genomes produced by ZIKV. HSV-2 titers were decreased by nearly every VMB tested relative to the sterile control, although Lactobacillus spp.-dominated VMBs caused the greatest reduction in HSV-2 titer consistent with clinical observations. To explore the mechanism for reduced ZIKV titers, we investigated inflammation created by ZIKV infection, VMB colonization or pre-exposure to selected TLR agonists. Finally, expression levels of human beta defensins 1–3 were quantified in cultures infected by ZIKV and those colonized by VMBs that impacted ZIKV titers. Human beta defensins 1–3 produced by the VEC showed no association with ZIKV titers. The data presented expands the utility of this ex vivo model system providing controlled and reproducible methods to study the VMB impact on STIs and indicated an association between viral replication and specific bacterial species within the VMB.

The relationship between sex hormones, the vaginal microbiome and immunity in HIV-1 susceptibility in women

The role of sex hormones in regulating immune responses in the female genital tract has been recognized for decades. More recently, it has become increasingly clear that sex hormones regulate susceptibility to sexually transmitted infections through direct and indirect mechanisms involving inflammation and immune responses. The reproductive cycle can influence simian/human immunodeficiency virus (SHIV) infections in primates and HIV-1 infection in ex vivo cervical tissues from women. Exogenous hormones, such as those found in hormonal contraceptives, have come under intense scrutiny because of the increased susceptibility to sexually transmitted infections seen in women using medroxyprogesterone acetate, a synthetic progestin-based contraceptive. Recent meta-analyses concluded that medroxyprogesterone acetate enhanced HIV-1 susceptibility in women by 40%. In contrast, estradiol-containing hormonal contraceptives were not associated with increased susceptibility and some studies reported a protective effect of estrogen on HIV/SIV infection, although the underlying mechanisms remain incompletely understood. Recent studies describe a key role for the vaginal microbiota in determining susceptibility to sexually transmitted infections, including HIV-1. While Lactobacillus spp.-dominated vaginal microbiota is associated with decreased susceptibility, complex microbiota, such as those seen in bacterial vaginosis, correlates with increased susceptibility to HIV-1. Interestingly, sex hormones are inherently linked to microbiota regulation in the vaginal tract. Estrogen has been postulated to play a key role in establishing a Lactobacillus-dominated microenvironment, whereas medroxyprogesterone acetate is linked to hypo-estrogenic effects. The aim of this Review is to contribute to a better understanding of the sex-hormone-microbiome-immunity axis, which can provide key information on the determinants of HIV-1 susceptibility in the female genital tract and, consequently, inform HIV-1 prevention strategies.

Lactobacillus crispatus accelerates re-epithelialization in vaginal epithelial cell line MS74

PROBLEM

The functions of vaginal lactobacilli in susceptibility to infectious diseases as regards epithelial barrier integrity and wound healing remain incompletely understood.

METHOD OF STUDY

Lactobacillus crispatus, one of the most common Lactobacillus species in the vagina and among the most protective against sexually transmitted infections, was cocultured with an immortalized human vaginal epithelial cell line (MS74), and a scratch assay was performed to evaluate re-epithelialization. The concentration of vascular endothelial growth factor A (VEGF) was measured using enzyme-linked immunosorbent assay (ELISA). An immunofluorescence assay was performed to locate the expression of VEGF and VEGF receptor (VEGFR) 1 and 2. The effects of the bacterial supernatant of L. crispatus were also evaluated.

RESULTS

Lactobacillus crispatus significantly accelerated re-epithelialization of MS74 cells, accompanied by an increase in VEGF concentration. In contrast, heat-killed L. crispatus did not show this effect. The bacterial supernatant of L. crispatus also induced re-epithelialization. The immunoreactivity of VEGF was higher at the scratched edge, whereas VEGFR1 and 2 stained site-independently. Recombinant VEGF induced cell migration in a dose-dependent manner. The bacterial supernatant of L. crispatus also significantly accelerated re-epithelialization in MS74 cells and increased the concentration of VEGF in the culture 24 hours after the scratch.

CONCLUSION

These results may enhance our knowledge of the importance of L. crispatus in the healing of damaged vaginal epithelium and protection against the consequent risk of pathogenic infections, such as human immunodeficiency virus (HIV), and improve our understanding of vaginal epithelial barrier integrity maintenance by this bacterium.

Cervicovaginal Microbiota and Reproductive Health: The Virtue of Simplicity

Cervicovaginal microbiota play a critical role in women's health and reproductive outcomes. Despite being one of the simplest commensal bacterial communities in the human body, we are only beginning to appreciate its complex dynamic nature and important role in host immune modulation. In this review, we discuss the "optimal" cervicovaginal bacterial community composition, the impact of microbiota on gynecologic and obstetric outcomes, and the hurdles to developing a deeper mechanistic understanding of the function of the cervicovaginal microbiome. We then describe efforts to durably alter microbial composition in this compartment by promotion of Lactobacillus colonization with probiotics, modulation of vaginal pH, hormonal administration, and the eradication of pathogenic bacteria with antibiotics. Finally, we draw on lessons learned from the deeply investigated gut microbiome to suggest future avenues of research into host-pathogen interactions in the female genital tract.

Clinical translation of microbe-based therapies: Current clinical landscape and preclinical outlook

Next generation microbe-based therapeutics, inspired by the success of fecal microbiota transplants, are being actively investigated in clinical trials to displace or eliminate pathogenic microbes to treat various diseases in the gastrointestinal tract, skin, and vagina. Genetically engineered microbes are also being investigated in the clinic as drug producing factories for biologic delivery, which can provide a constant local source of drugs. In either case, microbe-therapeutics have the opportunity to address unmet clinical needs and open new areas of research by reducing clinical side effects associated with current treatment modalities or by facilitating the delivery of biologics. This review will discuss examples of past and current clinical trials that are investigating microbe-therapeutics, both microbiome-modulating and drug-producing, for the treatment of a range of diseases. We then offer a perspective on how preclinical approaches, both those focused on developing advanced delivery systems and those that use in vitro microbiome model systems to inform formulation design, will lead to the realization of next-generation microbe-therapeutics.