Directed shift of vaginal microbiota induced by vaginal application of sucrose gel in rhesus macaques

The microbial revolution: Unveiling the benefits of vaginal probiotics and prebiotics

Vaginal health is essential to a woman's overall well-being, as abnormalities in vaginal health can lead to a variety of gynaecological disorders, such as urinary tract infections, yeast infections, and bacterial vaginosis. The vaginal microbiome is essential for the prevention of these infections. Disruptions in this microbial ecosystem can significantly impact vaginal health. The concept of utilizing probiotics and prebiotics to stimulate the growth of protective vaginal microbiota has gathered substantial interest in recent years. Probiotics are live micro-organisms that strengthen and restore vaginal microbial balance by lowering pH levels, production of bacteriocins, biofilm disruption, modulation of immune response, and production of hydrogen peroxide (H2O2), consequently combating the development of pathogens. Prebiotics are oligosaccharides that encourage the development of probiotics such as lactobacilli species. Probiotics and prebiotics also have some broader implications for vaginal health, including their role in minimizing the incidence of premature birth, optimizing fertility, managing menopausal symptoms, and preventing vaginal infections. Synbiotics are a combination of probiotics and prebiotics that deliver additional benefits by encouraging the development and activity of beneficial microbes. Furthermore, postbiotics are bioactive compounds derived from probiotic bacteria during fermentation that have immunomodulatory actions and provide an additional layer of protection against vaginal infections. The present study highlights the most prevalent vaginal infections and limitations of existing therapies that influence the vaginal microbiota. The profound consequences of probiotics and prebiotics in women's health, including their role in minimizing the prevalence of vaginal infections and promoting overall vaginal health, as well as advanced therapeutic strategies such as synbiotics and postbiotics, are also discussed. The literature offers significant insights into the mechanism, efficacy, and safety of probiotics and prebiotics to healthcare providers and researchers.

Medical-Grade Honey as a Potential New Therapy for Bacterial Vaginosis

The prevalence of bacterial vaginosis (BV) among women of reproductive age is 29%. BV arises from a vaginal imbalance marked by reduced levels of lactic acid-producing lactobacilli and an overgrowth of pathogenic anaerobes. The multifactorial nature of BV's pathogenesis complicates its treatment. Current antibiotic therapy exhibits a recurrence rate of about 60% within a year. Recurrence can be caused by antibiotic treatment failure (e.g., due to antimicrobial resistance), the persistence of residual infections (e.g., due to biofilm formation), and re-infection. Because of the high recurrence rates, alternative therapies are required. Medical-grade honey (MGH), known for its antimicrobial and wound healing properties in wound care, emerges as a potential novel therapy for BV. MGH exerts broad-spectrum antimicrobial activity, employing multiple mechanisms to eliminate the risk of resistance. For example, the low pH of MGH and the production of hydrogen peroxide benefit the microbiota and helps restore the natural vaginal balance. This is supported by in vitro studies demonstrating that MGH has an antibacterial effect on several pathogenic bacteria involved in the pathophysiology of BV, while lactobacilli and the vaginal microenvironment can be positively affected. In contrast to antibiotics, MGH exerts anti-biofilm activity, affects the microbiome as pre- and probiotic, and modulates the vaginal microenvironment through its anti-inflammatory, anti-oxidative, physicochemical, and immunomodulatory properties. More clinical research is required to confirm the positive effect of MGH on BV and to investigate the long-term cure rate.

Significant Microbial Changes Are Evident in the Reproductive Tract of Pregnant Rhesus Monkeys at Mid-Gestation but Their Gut Microbiome Does Not Shift until Late Gestation

Vaginal and rectal specimens were obtained from cycling, pregnant, and nursing rhesus monkeys to assess pregnancy-related changes in the commensal bacteria in their reproductive and intestinal tracts. Using 16S rRNA gene amplicon sequencing, significant differences were found only in the vagina at mid-gestation, not in the hindgut. To verify the apparent stability in gut bacterial composition at mid-gestation, the experiment was repeated with additional monkeys, and similar results were found with both 16S rRNA gene amplicon and metagenomic sequencing. A follow-up study investigated if bacterial changes in the hindgut might occur later in pregnancy. Gravid females were assessed closer to term and compared to nonpregnant females. By late pregnancy, significant differences in bacterial composition, including an increased abundance of 4 species of Lactobacillus and Bifidobacterium adolescentis, were detected, but without a shift in the overall community structure. Progesterone levels were assessed as a possible hormone mediator of bacterial change. The relative abundance of only some taxa (e.g., Bifidobacteriaceae) were specifically associated with progesterone. In summary, pregnancy changes the microbial profiles in monkeys, but the bacterial diversity in their lower reproductive tract is different from women, and the composition of their intestinal symbionts remains stable until late gestation when several Firmicutes become more prominent.

Microbiota and nanoparticles: Description and interactions

The healthy human body is inhabited with a large number of bacteria, forming natural flora. It is even estimated that for a human body, its amount of DNA is less important that its bacterial genetic material. This flora plays major roles in the sickness and health of the human body and any change in its composition may lead to different diseases. Nanoparticles are widely used in numerous fields: cosmetics, food, industry, and as drug delivery carrier in the medical field. Being included in these various applications, nanoparticles may interact with the human body at various levels and with different mechanisms. These interactions differ depending on the nanoparticle nature, its structure, its concentration and manifest in different ways on the microbiota, leading to its destabilization, its restoring or showing no toxic effect. Nanoparticles may also be used as a vehicle to regulate the microbiota or to treat some of its diseases.

The Role of Fatty Acid Metabolites in Vaginal Health and Disease: Application to Candidiasis

Although the vast majority of women encounters at least one vaginal infection during their life, the amount of microbiome-related research performed in this area lags behind compared to alternative niches such as the intestinal tract. As a result, effective means of diagnosis and treatment, especially of recurrent infections, are limited. The role of the metabolome in vaginal health is largely elusive. It has been shown that lactate produced by the numerous lactobacilli present promotes health by limiting the chance of infection. Short chain fatty acids (SCFA) have been mainly linked to dysbiosis, although the causality of this relationship is still under debate. In this review, we aim to bring together information on the role of the vaginal metabolome and microbiome in infections caused by Candida. Vulvovaginal candidiasis affects near to 70% of all women at least once in their life with a significant proportion of women suffering from the recurrent variant. We assess the role of fatty acid metabolites, mainly SCFA and lactate, in onset of infection and virulence of the fungal pathogen. In addition, we pinpoint where lack of research limits our understanding of the molecular processes involved and restricts the possibility of developing novel treatment strategies.

Longitudinal Profiling of the Macaque Vaginal Microbiome Reveals Similarities to Diverse Human Vaginal Communities

The vaginal microbiota plays an important role in women's reproductive and urogenital health. It is now well accepted that a "healthy" vaginal microbiome is dominated by Lactobacillus species. Disturbances in this microbial community can lead to several adverse outcomes, including pelvic inflammatory disease and bacterial vaginosis (BV), as well as increased susceptibility to sexually transmitted infections, miscarriage, and preterm births. However, vaginal communities, especially those of women in the developing world, can be comprised of a diverse set of microorganisms in the absence of overt clinical symptoms. The implications of these diverse vaginal microbiomes for women's health remain poorly understood. Rhesus macaques are an excellent translational animal model to address these questions due to significant physiological and genetic homology with humans. In this study, we performed a longitudinal analysis of clinical and microbiome data from 16 reproductive-age female rhesus macaques. At both the taxonomic and functional levels, the rhesus macaque vaginal microbiome was most similar to that of women who harbor a diverse vaginal community associated with asymptomatic/symptomatic bacterial vaginosis. Specifically, rhesus macaque vaginal microbiomes harbored a diverse set of anaerobic Gram-negative bacteria, including Sneathia, Prevotella, Porphyromonas, and Mobiluncus Interestingly, some animals were transiently colonized by Lactobacillus and some with Gardnerella Our in-depth and comprehensive analysis highlights the importance of the model to understand the health implications of a diverse vaginal microbiome and test interventions for manipulating this community.IMPORTANCE It is widely accepted that the "healthy" vaginal microbiome of women in the developed world is dominated by Lactobacillus species. However, in the developing world, many asymptomatic women harbor diverse vaginal microbial communities that are typically associated with bacterial vaginosis. Many questions remain about the drivers and health implications of a diverse vaginal microbial community. Rhesus macaques provide an excellent translational model to address these questions due to significant physiological and genetic homology with humans. In this study, we performed a longitudinal analysis of clinical and microbiome data from a large cohort of reproductive-age rhesus macaques. At the taxonomic, genomic, and functional levels, the rhesus macaque vaginal microbiome was most similar to that of humans, who harbor a diverse vaginal community associated with asymptomatic/symptomatic bacterial vaginosis. Our in-depth and comprehensive analysis highlights the utility of macaques as a model to study diverse vaginal community state types and test interventions for manipulating the vaginal microbiome.

Prebiotic Maltose Gel Can Promote the Vaginal Microbiota From BV-Related Bacteria Dominant to Lactobacillus in Rhesus Macaque

The high incidence of bacterial vaginosis recurrence is common after treatment with an antibiotic agent and suggests the need for new treatments to prevent this. We conducted a randomized trial to evaluate the ability of maltose gel to treat bacterial vaginosis. Eighteen female rhesus macaques were randomly assigned, in a 2:1 ratio, to receive maltose gel or placebo gel by syringe to the fornix of the vagina for five consecutive days. We used 16S rRNA sequencing data from 70 swab samples of vaginal secretions in two groups in total on days 0, 3, and 5 after medication initiation and days 3 and 5 after medication withdrawal for the study of microbiome composition. We found that, in the placebo control group, there was no significant change in the composition and abundance of vaginal microbiota during the follow-up period. In the maltose gel test group, the abundance of Lactobacillus in the vagina microbiota increased gradually with the prolongation of the treatment time on Days 3 and 5 (ANOVA p = 6.99e−5 < 0.01) but began to decrease after the withdrawal of maltose gel, which was different from that of the control group. Correspondingly, the diversity and abundance of BV-related bacteria, Fusobacterium, Parvimonas, Mobiluncus, Campylobacter, Prevotella, and Sneathia, decreased on Day 0 to Day 5 of medication and increased after drug withdrawal in the maltose gel test group. The study confirms that maltose gel can facilitate the proliferation of Lactobacillus and promote the transition of the vaginal microbiota from BV-related bacteria dominant to Lactobacillus dominant in the rhesus macaque.

Rectal Microbiome Composition Correlates with Humoral Immunity to HIV-1 in Vaccinated Rhesus Macaques

There is considerable effort directed toward evaluating HIV-1 vaccine platforms to select the most promising candidates for enhancing mucosal HIV-1 antibody. The most successful thus far, the RV144 trial provided partial protection due to waning HIV-1 antibody titers. In order to develop an effective HIV vaccine, it may therefore be important to understand how biological factors, such as the microbiome, modulate host immune responses. Furthermore, as intestinal microbiota antigens may generate antibodies cross-reactive to the HIV-1 envelope glycoprotein, understanding the relationship between gut microbiota composition and HIV-1 envelope antibody responses after vaccination is important. Here, we demonstrate for the first time in rhesus macaques that the rectal microbiome composition can influence HIV-1 vaccine immunogenicity, and we report temporal changes in the mucosal microbiome profile following HIV-1 vaccination. Our results could inform findings from the HIV Vaccine Trials Network (HVTN) vaccine studies and contribute to an understanding of how the microbiome influences HIV-1 antibody responses.

The microbiome is an integral and dynamic component of the host and is emerging as a critical determinant of immune responses; however, its influence on vaccine immunogenicity is largely not well understood. Here, we examined the pivotal relationship between the mucosal microbiome and vaccine-induced immune responses by assessing longitudinal changes in vaginal and rectal microbiome profiles after intradermal immunization with a human immunodeficiency virus type 1 (HIV-1) DNA vaccine in adult rhesus macaques that received two prior DNA primes. We report that both vaginal and rectal microbiomes were dominated by Firmicutes but were composed of distinct genera, denoting microbiome specialization across mucosal tissues. Following immunization, the vaginal microbiome was resilient, except for a transient decrease in Streptococcus. In contrast, the rectal microbiome was far more responsive to vaccination, exhibiting an increase in the ratio of Firmicutes to Bacteroidetes. Within Bacteroidetes, multiple genera were significantly decreased, including Prevotella, Alloprevotella, Bacteroides, Acetobacteroides, Falsiporphyromonas, and Anaerocella. Decreased abundance of Prevotella correlated with induction of gut-homing α₄β₇⁺ effector CD4 T cells. Prevotella abundance also negatively correlated with rectal HIV-1 specific IgG levels. While rectal Lactobacillus was unaltered following DNA vaccination, baseline Lactobacillus abundance showed strong associations with higher rectal HIV-1 gp140 IgA induced following a protein boost. Similarly, the abundance of Clostridium in cluster IV was associated with higher rectal HIV-1 gp140 IgG responses. Collectively, these data reveal that the temporal stability of bacterial communities following DNA immunization is site dependent and highlight the importance of host-microbiome interactions in shaping HIV-1 vaccine responses. Our findings have significant implications for microbial manipulation as a strategy to enhance HIV vaccine-induced mucosal immunity.

IMPORTANCE There is considerable effort directed toward evaluating HIV-1 vaccine platforms to select the most promising candidates for enhancing mucosal HIV-1 antibody. The most successful thus far, the RV144 trial provided partial protection due to waning HIV-1 antibody titers. In order to develop an effective HIV vaccine, it may therefore be important to understand how biological factors, such as the microbiome, modulate host immune responses. Furthermore, as intestinal microbiota antigens may generate antibodies cross-reactive to the HIV-1 envelope glycoprotein, understanding the relationship between gut microbiota composition and HIV-1 envelope antibody responses after vaccination is important. Here, we demonstrate for the first time in rhesus macaques that the rectal microbiome composition can influence HIV-1 vaccine immunogenicity, and we report temporal changes in the mucosal microbiome profile following HIV-1 vaccination. Our results could inform findings from the HIV Vaccine Trials Network (HVTN) vaccine studies and contribute to an understanding of how the microbiome influences HIV-1 antibody responses.

Comparing the effect of sucrose gel and metronidazole gel in treatment of clinical symptoms of bacterial vaginosis: a randomized controlled trial

BACKGROUND

Lactobacilli, as normal vaginal flora, have a central role in controlling body environment and preventing the growth of pathogens. Sucrose, by promoting the growth of Lactobacilli, accelerates the suppression of pathogenic bacteria. The aim of this research was to compare the effects of sucrose gel with those of metronidazole gel in treating women with bacterial vaginosis (BV).

METHODS

This triple-blind clinical trial (IRCT2016112631105N1) was conducted with 70 sexually active, premenopausal women diagnosed with bacterial vaginosis through meeting at least three out of four Amsel criteria. The subjects were randomly divided into two groups of 35 patients, one group treated with sucrose vaginal gel, and the other with metronidazole vaginal gel. The treatment period was 14 days for each group. At the end of the treatment period, the status of each woman's improvement was determined by elimination at least three out of four Amsel criteria (homogeneous vaginal discharge, presence of clue cells > 20%, positive whiff test and vaginal pH value > 4.5), and clinical complaints and reported side effects of medication were recorded for the patients. Data were analyzed using the t test, chi-squared test and McNemar's test).

RESULTS

The sucrose vaginal gel and metronidazole vaginal gel were not significantly different in reducing patients' clinical complaints or in elimination at least three out of four of the Amsel criteria that were positive before treatment. With an 85.7% improvement rate with sucrose gel and an 88.5% improvement rate with metronidazole gel, the differences in therapeutic response were not significant, and neither was statistically different in improving the disease (p = 0.389).

CONCLUSION

It seems that sucrose vaginal gel might be considered a possible alternative to metronidazole vaginal gel in the treatment of bacterial vaginosis.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials, IRCT2016112631105N1 . Registered on 27 December 2016.

Low Lactobacilli abundance and polymicrobial diversity in the lower reproductive tract of female rhesus monkeys do not compromise their reproductive success

The lower reproductive tract of nonhuman primates is colonized with a diverse microbiota, resembling bacterial vaginosis (BV), a gynecological condition associated with negative reproductive outcomes in women. Our 4 aims were to: (i) assess the prevalence of low Lactobacilli and a BV-like profile in female rhesus monkeys; (ii) quantify cytokines in their cervicovaginal fluid (CVF); (iii) examine the composition and structure of their mucosal microbiota with culture-independent sequencing methods; and (iv) evaluate the potential influence on reproductive success. CVF specimens were obtained from 27 female rhesus monkeys for Gram's staining, and to determine acidity (pH), and quantify proinflammatory cytokines. Based on Nugent's classification, 40% had a score of 7 or higher, which would be indicative of BV in women. Nugent scores were significantly correlated with the pH of the CVF. Interleukin-1ß was present at high concentrations, but not further elevated by high Nugent scores. Vaginal swabs were obtained from eight additional females to determine microbial diversity by rRNA gene amplicon sequencing. At the phylum level, the Firmicutes/Bacteroidetes ratio was low. The relative abundance of Lactobacilli was also low (between 3% and 17%), and 11 other genera were present at >1%. However, neither the microbial diversity in the community structure, nor high Nugent scores, was associated with reduced fecundity. Female monkeys provide an opportunity to understand how reproductive success can be sustained in the presence of a diverse polymicrobial community in the reproductive tract.

Comparison of the vaginal environment in rhesus and cynomolgus macaques pre- and post-lactobacillus colonization

BACKGROUND

Rhesus and cynomologus macaques are valuable animal models for the study of human immunodeficiency virus (HIV) prevention strategies. However, for such studies focused on the vaginal route of infection, differences in vaginal environment may have deterministic impact on the outcome of such prevention, providing the rationale for this study.

METHODS

We tested the vaginal environment of rhesus and cynomolgus macaques longitudinally to characterize the normal microflora based on Nugent scores and pH. This evaluation was extended after colonization of the vaginal space with Lactobacilli in an effort to recreate NHP models representing the healthy human vaginal environment.

RESULTS AND CONCLUSION

Nugent scores and pH differed significantly between species, although data from both species were suggestive of stable bacterial vaginosis. Colonization with Lactobacilli was successful in both species leading to lower Nugent score and pH, although rhesus macaques appeared better able to sustain Lactobacillus spp over time.

Freeze-dried cylinders carrying chitosan nanoparticles for vaginal peptide delivery

Recently nanoparticle-based vaginal drug delivery formulations have been acquiring great attention for the administration of peptide based-vaccines or microbicides to prevent or treat sexually transmitted diseases. In this work, a straightforward and efficient strategy for the vaginal application and release of peptide-loaded mucoadhesive nanoparticles was developed. This essentially consists of chitosan nanoparticles encapsulated in suitable hydrophilic freeze-dried cylinders. Chitosan nanoparticles are responsible for carrying the peptide drug and allowing adhesion to the vaginal mucosal epithelium. Hydrophilic freeze-dried cylinders facilitate the application and quick release of the nanoparticles to the vaginal zone. Upon contact with the aqueous vaginal medium, the excipients constituting these sponge-like systems are quickly dissolved enabling the release of their content. In vitro release studies showed the ability of the sponge-like systems and chitosan nanoparticles to deliver the mucoadhesive nanoparticles and peptide respectively. CLSM micrographs proved the nanoparticles ability promoting the peptide penetration inside the vaginal mucosa.

Genomic Comparisons of Lactobacillus crispatus and Lactobacillus iners Reveal Potential Ecological Drivers of Community Composition in the Vagina

Lactobacillus crispatus and Lactobacillus iners are common inhabitants of the healthy human vagina. These two species are closely related and are thought to perform similar ecological functions in the vaginal environment. Temporal data on the vaginal microbiome have shown that nontransient instances of cooccurrence are uncommon, while transitions from an L. iners-dominated community to one dominated by L. crispatus, and vice versa, occur often. This suggests that there is substantial overlap in the fundamental niches of these species. Given this apparent niche overlap, it is unclear how they have been maintained as common inhabitants of the human vagina. In this study, we characterized and compared the genomes of L. iners and L. crispatus to gain insight into possible mechanisms driving the maintenance of this species diversity. Our results highlight differences in the genomes of these two species that may facilitate the partitioning of their shared niche space. Many of the identified differences may impact the protective benefits provided to the host by these two species.

IMPORTANCE

The microbial communities that inhabit the human vagina play a critical role in the maintenance of vaginal health through the production of lactic acid and lowering the environmental pH. This precludes the growth of nonindigenous organisms and protects against infectious disease. The two most common types of vaginal communities are dominated by either Lactobacillus iners or Lactobacillus crispatus, while some communities alternate between the two over time. We combined ecological theory with state-of-the-art genome analyses to characterize how these two species might partition their shared niche space in the vagina. We show that the genomes of L. iners and L. crispatus differ in many respects, several of which may drive differences in their competitive abilities in the vagina. Our results provide insight into factors that drive the complicated temporal dynamics of the vaginal microbiome and demonstrate how closely related microbial species partition shared fundamental niche space.