Hydrolysis of secreted sialoglycoprotein immunoglobulin A (IgA) in ex vivo and biochemical models of bacterial vaginosis

Prevotella are major contributors of sialidases in the human vaginal microbiome

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

Phase variable colony variants are conserved across Gardnerella spp. and exhibit different virulence-associated phenotypes

The Gardnerella genus, comprising at least 13 species, is associated with the polymicrobial disorder bacterial vaginosis (BV). However, the details of BV pathogenesis are poorly defined, and the contributions made by individual species, including Gardnerella spp., are largely unknown. We report here that colony phenotypes characterized by size (large and small) and opacity (opaque and translucent) are phase variable and are conserved among all tested Gardnerella strains, representing at least 10 different species. With the hypothesis that these different variants could be an important missing piece to the enigma of how BV develops in vivo, we characterized their phenotypic, proteomic, and genomic differences. Beyond increased colony size, large colony variants showed reduced vaginolysin secretion and faster growth rate relative to small colony variants. The ability to inhibit the growth of Neisseria gonorrhoeae and commensal Lactobacillus species varied by strain and, in some instances, differed between variants. Proteomics analyses indicated that 127-173 proteins were differentially expressed between variants. Proteins with increased expression in large variants of both strains were associated with amino acid and protein synthesis and protein folding, whereas those increased in small variants were related to nucleotide synthesis, phosphate transport, ABC transport, and glycogen breakdown. Furthermore, whole genome sequencing analyses revealed an abundance of genes associated with variable homopolymer tracts, implicating slipped strand mispairing in Gardnerella phase variation and illuminating the potential for previously unrecognized heterogeneity within clonal populations. Collectively, these results suggest that phase variants may be primed to serve different roles in BV pathogenesis.IMPORTANCEBacterial vaginosis is the most common gynecological disorder in women of childbearing age. Gardnerella species are crucial to the development of this dysbiosis, but the mechanisms involved in the infection are not understood. We discovered that Gardnerella species vary between two different forms, reflected in bacterial colony size. A slow-growing form makes large amounts of the toxin vaginolysin and is better able to survive in human cervix tissue. A fast-growing form is likely the one that proliferates to high numbers just prior to symptom onset and forms the biofilm that serves as a scaffold for multiple BV-associated anaerobic bacteria. Identification of the proteins that vary between different forms of the bacteria as well as those that vary randomly provides insight into the factors important for Gardnerella infection and immune avoidance.

Ablation of Intestinal Epithelial Sialylation Predisposes to Acute and Chronic Intestinal Inflammation in Mice

BACKGROUND & AIMS

Addition of sialic acids (sialylation) to glycoconjugates is a common capping step of glycosylation. Our study aims to determine the roles of the overall sialylation in intestinal mucosal homeostasis.

METHODS

Mice with constitutive deletion of intestinal epithelial sialylation (IEC Slc35a1-/- mice) and mice with inducible deletion of sialylation in intestinal epithelium (TM-IEC Slc35a1-/- mice) were generated, which were used to determine the roles of overall sialylation in intestinal mucosal homeostasis by ex vivo and mutiomics studies.

RESULTS

IEC Slc35a1-/- mice developed mild spontaneous microbiota-dependent colitis. Additionally, 30% of IEC Slc35a1-/- mice had spontaneous tumors in the rectum greater than the age of 12 months. TM-IEC Slc35a1-/- mice were highly susceptible to acute inflammation induced by 1% dextran sulfate sodium versus control animals. Loss of total sialylation was associated with reduced mucus thickness on fecal sections and within colon tissues. TM-IEC Slc35a1-/- mice showed altered microbiota with an increase in Clostridium disporicum, which is associated a global reduction in the abundance of at least 10 unique taxa; however, metabolomic analysis did not show any significant differences in short-chain fatty acid levels. Treatment with 5-fluorouracil led to more severe small intestine mucositis in the IEC Slc35a1-/- mice versus wild-type littermates, which was associated with reduced Lgr5+ cell representation in small intestinal crypts in IEC Slc35a1-/-;Lgr5-GFP mice.

CONCLUSIONS

Loss of overall sialylation impairs mucus stability and the stem cell niche leading to microbiota-dependent spontaneous colitis and tumorigenesis.

The Sweet Relationship between the Endometrium and Protein Glycosylation

The endometrium is an important part of women's bodies for menstruation and pregnancy. Various proteins are widely expressed on the surface of endometrial cells, and glycosylation is an important post-translational modification of proteins. Glycosylation modification is closely related not only to endometrial receptivity but also to common diseases related to endometrial receptivity. Glycosylation can improve endometrial receptivity, promote embryo localization and trophoblast cell adhesion and invasion, and contribute to successful implantation. Two diseases related to endometrial receptivity include endometriosis and endometrial cancer. As a common benign disease in women, endometriosis is often accompanied by an increased menstrual volume, prolonged menstrual periods, progressive and aggravated dysmenorrhea, and may be accompanied by infertility. Protein glycosylation modification of the endometrial surface indicates the severity of the disease and may be an important pathogenesis of endometriosis. In cancer, glycosylation modifications on the surface of tumor cells can be a marker to distinguish the type and severity of endometrial cancer. This review highlights the role of protein glycosylation in embryo-maternal endometrial dialogue and explores its potential mechanisms in diseases related to endometrial receptivity, which could provide a new clinical approach for their diagnosis and treatment.

The role of sialidases in the pathogenesis of bacterial vaginosis and their use as a promising pharmacological target in bacterial vaginosis

Bacterial vaginosis (BV) is an infection of the genital tract characterized by disturbance of the normally Lactobacilli-dominated vaginal flora due to the overgrowth of Gardnerella and other anaerobic bacteria. Gardnerella vaginalis, an anaerobic pathogen and the major pathogen of BV, produces sialidases that cleave terminal sialic acid residues off of human glycans. By desialylation, sialidases not only alter the function of sialic acid-containing glycoconjugates but also play a vital role in the attachment, colonization and spread of many other vaginal pathogens. With known pathogenic effects, excellent performance of sialidase-based diagnostic tests, and promising therapeutic potentials of sialidase inhibitors, sialidases could be used as a biomarker of BV. This review explores the sources of sialidases and their role in vaginal dysbiosis, in aims to better understand their participation in the pathogenesis of BV and their value in the diagnosis and treatment of BV.

IgA coating of vaginal bacteria is reduced in the setting of bacterial vaginosis (BV) and preferentially targets BV-associated species

Immunoglobulin (Ig) bacterial coating has been described in the gastrointestinal tract and linked to inflammatory bowel disease; however, little is known about Ig coating of vaginal bacteria and whether it plays a role in vaginal health including bacterial vaginosis (BV). We examined Ig coating in 18 women with symptomatic BV followed longitudinally before, 1 week, and 1 month after oral metronidazole treatment. Immunoglobulin A (IgA) and/or immunoglobulin G (IgG) coating of vaginal bacteria was assessed by flow cytometry, and Ig coated and uncoated bacteria were sorted and characterized using 16S rRNA sequencing. Despite higher levels of IgG compared to IgA in cervicovaginal fluid, the predominant Ig coating the bacteria was IgA. The majority of bacteria were uncoated at all visits, but IgA coating significantly increased after treatment for BV. Despite similar amounts of uncoated and IgA coated majority taxa ( >1% total) across all visits, there was preferential IgA coating of minority taxa (0.2%-1% total) associated with BV including Sneathia, several Prevotella species, and others. At the time of BV, we identified a principal component (PC) driven by proinflammatory mediators that correlated positively with an uncoated BV-associated bacterial community and negatively with an IgA coated protective Lactobacillus bacterial community. The preferential coating of BV-associated species, increase in coating following metronidazole treatment, and positive correlation between uncoated BV-associated species and inflammation suggest that coating may represent a host mechanism designed to limit bacterial diversity and reduce inflammatory responses. Elucidating the role of Ig coating in vaginal mucosal immunity may promote new strategies to prevent recurrent BV.

Resident microbes shape the vaginal epithelial glycan landscape

Epithelial cells are covered in carbohydrates (glycans). This glycan coat or "glycocalyx" interfaces directly with microbes, providing a protective barrier against potential pathogens. Bacterial vaginosis (BV) is a condition associated with adverse health outcomes in which bacteria reside in direct proximity to the vaginal epithelium. Some of these bacteria, including Gardnerella, produce glycosyl hydrolase enzymes. However, glycans of the human vaginal epithelial surface have not been studied in detail. Here, we elucidate key characteristics of the "normal" vaginal epithelial glycan landscape and analyze the impact of resident microbes on the surface glycocalyx. In human BV, glycocalyx staining was visibly diminished in electron micrographs compared to controls. Biochemical and mass spectrometric analysis showed that, compared to normal vaginal epithelial cells, BV cells were depleted of sialylated N- and O-glycans, with underlying galactose residues exposed on the surface. Treatment of primary epithelial cells from BV-negative women with recombinant Gardnerella sialidases generated BV-like glycan phenotypes. Exposure of cultured VK2 vaginal epithelial cells to recombinant Gardnerella sialidase led to desialylation of glycans and induction of pathways regulating cell death, differentiation, and inflammatory responses. These data provide evidence that vaginal epithelial cells exhibit an altered glycan landscape in BV and suggest that BV-associated glycosidic enzymes may lead to changes in epithelial gene transcription that promote cell turnover and regulate responses toward the resident microbiome.

Vaginal microecology and its role in human papillomavirus infection and human papillomavirus associated cervical lesions

The vaginal microecology comprises the vaginal microbiome, immune microenvironment, vaginal anatomy, and the cervicovaginal fluid, which is rich in metabolites, enzymes, and cytokines. Investigating its role in the female reproductive system holds paramount significance. The advent of next-generation sequencing enabled a more profound investigation into the structure of the vaginal microbial community in relation to the female reproductive system. Human papillomavirus infection is prevalent among women of reproductive age, and persistent oncogenic HPV infection is widely recognized as a factor associated with cervical cancer. Extensive previous research has demonstrated that dysbiosis of vaginal microbiota characterized by a reduction in Lactobacillus species, heightens susceptivity to HPV infection, consequently contributing to persistent HPV infection and the progression of cervical lesion. Likewise, HPV infection can exacerbate dysbiosis. This review aims to provide a comprehensive summary of current literatures and to elucidate potential mechanisms underlying the interaction between vaginal microecology and HPV infection, with the intention of offering valuable insights for future clinical interventions.

Cervicovaginal Gardnerella sialidase-encoding gene in persistent human papillomavirus infection

Disturbed vaginal microbiota have a role in the persistence of high-oncogenic-risk human papillomavirus (hrHPV) and Gardnerella spp. is closely related with this condition. Such bacteria are the major source of cervicovaginal sialidases, important for microbiota alterations. The sialidase-encoding gene nanH3 is account for their sialidase activity. Thus, a subset of 212 women positive for hrHPV at the first visit were included in the analysis of the current study aiming to compare the loads of nanH3 in cervicovaginal fluid (CFV) of women with persistent hrHPV infection and with those cleared the infection after a year. Participants were assigned to two study groups named "persistence" (n = 124, 53.22%) or "clearance" (n = 88, 37.77%), according to the HPV status upon enrollment and follow-up. Absolute quantification of nanH3 gene was performed using quantitative real-time PCR (qPCR). Persistence and clearance group did not show statistical difference in the load of nanH3 gene (p = 0.19). When considering the subset of women with HPV16, differences in number of copies of nanh3 gene was observed between the persistent (7.39E+08 copies/μL) and clearance group (2.85E+07 copies/μL) (p = 0.007). Therefore, baseline loads of nanH3 gene is increased in women that persist with cervical HPV16 infection after 12 months.

Dysregulation of immune response in PCOS organ system

Polycystic ovary syndrome (PCOS) is the most common reproductive endocrine disorder affecting women, which can lead to infertility. Infertility, obesity, hirsutism, acne, and irregular menstruation are just a few of the issues that PCOS can be linked to. PCOS has a complicated pathophysiology and a range of clinical symptoms. Chronic low-grade inflammation is one of the features of PCOS. The inflammatory environment involves immune and metabolic disturbances. Numerous organ systems across the body, in addition to the female reproductive system, have been affected by the pathogenic role of immunological dysregulation in PCOS in recent years. Insulin resistance and hyperandrogenism are associated with immune cell dysfunction and cytokine imbalance. More importantly, obesity is also involved in immune dysfunction in PCOS, leading to an inflammatory environment in women with PCOS. Hormone, obesity, and metabolic interactions contribute to the pathogenesis of PCOS. Hormone imbalance may also contribute to the development of autoimmune diseases. The aim of this review is to summarize the pathophysiological role of immune dysregulation in various organ systems of PCOS patients and provide new ideas for systemic treatment of PCOS in the future.

Lactobacillus helveticus HY7801 ameliorates bacterial vaginosis by inhibiting biofilm formation and epithelial cell adhesion of Gardnerella vaginalis

Bacterial vaginosis (BV) is caused by a microbial imbalance in the vaginal ecosystem, which causes genital discomfort and a variety of potential complications in women. This study validated the potential of Lactobacillus helveticus HY7801 as a probiotic to benefit vaginal health. In vivo, HY7801 reduced the number of Gardnerella vaginalis (GV) and pro-inflammatory cytokines in the vagina of GV-induced BV mice and ameliorated vaginal histological changes. In vitro, HY7801 exhibited positive resistance to simulated gastrointestinal conditions, showed excellent adherence ability to the female genital epithelium, and had high lactic acid and H₂O₂ production capacity. Furthermore, it was found that HY7801 can alleviate BV because it can suppress the expression of virulence factor genes of GV involved in epithelial cell adhesion and biofilm formation along with antibacterial activity against GV. These results indicate that HY7801 can be used as a promising probiotic strain for the maintenance of a healthy vaginal physiological state.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01208-7.

Cervicovaginal loads of Gardnerella spp. are increased in immunocompetent women with persistent high-risk human papillomavirus infection

Introduction. Two high-oncogenic-risk human papilomavirus (hrHPV) genotypes - HPV16 and HPV18 - cause most of the cases of cervical cancer worldwide. Bacterial vaginosis is associated with increased hrHPV persistence, although the mechanism underlying this association remains unclear. Gardnerella spp. are detected in nearly all cases of bacterial vaginosis and are the major source of cervicovaginal sialidases. The NanH1 gene is present in virtually all Gardnerella sialidase-producing strains and has been proposed as a potential marker for persistent hrHPV infection.Hypothesis. Gardnerella spp. load and the NanH1 gene are associated with hrHPV persistence.Aim. To compare the cervicovaginal load of Gardnerella spp. and the frequency of the NanH1 gene between women with persistent HPV16 and/or HPV18 infection and those who cleared the infection after 11 months.Methodology. Among a population of 1638 HPV screened, we detected 104 with positive HPV16 and/or HPV18 results. Samples were obtained at two time points (baseline and at a median of 11 months at follow-up) and tested using the Linear Array HPV Genotyping kit (Roche Molecular Systems, Pleasanton, CA, USA). Based on their HPV16/HPV18 status at enrolment and follow-up, participants were assigned to 'persistence' or 'clearance' groups. We used cervicovaginal fluid samples obtained upon enrolment to determine the load of the 23 s rRNA gene of Gardnerella spp. and the presence of the NanH1 gene using real-time polymerase chain reaction (PCR). We compared Gardnerella spp. loads and NanH1 frequency between the groups by, respectively, Mann-Whitney and chi-squared tests, with a P-value <0.05 considered to be significant.Results. Of the 104 participants who were positive for HPV16/HPV18, 73 (70.2 %) persisted with at least 1 of the baseline genotypes at follow-up, while 31 (29.8 %) cleared the infection in this time frame. Participants in the persistence group had significantly higher loads of Gardnerella spp. [5.8E+02 (0-3.0E+05) copies µl^-1] than those in the clearance group [9.9E+01 (0-7.7E+04) copies µl^-1] (P=0.03). The baseline frequency of NanH1 was higher in the persistence' (n=46, 63.0 %) than in the clearance (n=14, 45.2 %) group, although this was not statistically significant (P=0.09).Conclusion. These findings reinforce the negative effect of vaginal microbiota for the clearance of hrHPV and indicate a possible association between sialidase-producing species with hrHPV persistence.

Sialidase Activity in the Cervicovaginal Fluid Is Associated With Changes in Bacterial Components of Lactobacillus-Deprived Microbiota

INTRODUCTION

Sialidase activity in the cervicovaginal fluid (CVF) is associated with microscopic findings of bacterial vaginosis (BV). Sequencing of bacterial 16S rRNA gene in vaginal samples has revealed that the majority of microscopic BV cases fit into vaginal community-state type IV (CST IV), which was recently named "molecular-BV." Bacterial vaginosis-associated bacterial species, such as Gardnerella spp., may act as sources of CVF sialidases. These hydrolases lead to impairment of local immunity and enable bacterial adhesion to epithelial and biofilm formation. However, the impact of CVL sialidase on microbiota components and diversity remains unknown.

OBJECTIVE

To assess if CVF sialidase activity is associated with changes in bacterial components of CST IV.

METHODS

One hundred forty women were cross-sectionally enrolled. The presence of molecular-BV (CST IV) was assessed by V3-V4 16S rRNA sequencing (Illumina). Fluorometric assays were performed using 2-(4-methylumbelliferyl)-α-D-N-acetylneuraminic acid (MUAN) for measuring sialidase activity in CVF samples. Linear discriminant analysis effect size (LEfSe) was performed to identify the differently enriched bacterial taxa in molecular-BV according to the status of CVF sialidase activity.

RESULTS

Forty-four participants (31.4%) had molecular-BV, of which 30 (68.2%) had sialidase activity at detectable levels. A total of 24 bacterial taxa were enriched in the presence of sialidase activity, while just two taxa were enriched in sialidase-negative samples.

CONCLUSION

Sialidase activity in molecular-BV is associated with changes in bacterial components of the local microbiome. This association should be further investigated, since it may result in diminished local defenses against pathogens.

Protease activities of vaginal Porphyromonas species disrupt coagulation and extracellular matrix in the cervicovaginal niche

Porphyromonas asaccharolytica and Porphyromonas uenonis are common inhabitants of the vaginal microbiome, but their presence has been linked to adverse health outcomes for women, including bacterial vaginosis and preterm birth. However, little is known about the pathogenesis mechanisms of these bacteria. The related oral opportunistic pathogen, Porphyromonas gingivalis, is comparatively well-studied and known to secrete numerous extracellular matrix-targeting proteases. Among these are the gingipain family of cysteine proteases that drive periodontal disease progression and hematogenic transmission to the placenta. In this study, we demonstrate that vaginal Porphyromonas species secrete broad-acting proteases capable of freely diffusing within the cervicovaginal niche. These proteases degrade collagens that are enriched within the cervix (type I) and chorioamniotic membranes (type IV), as well as fibrinogen, which inhibits clot formation. Bioinformatic queries confirmed the absence of gingipain orthologs and identified five serine, cysteine, and metalloprotease candidates in each species. Inhibition assays revealed that each species' proteolytic activity can be partially attributed to a secreted metalloprotease with broad substrate specificity that is distantly related to the P. gingivalis endopeptidase PepO. This characterization of virulence activities in vaginal Porphyromonas species highlights their potential to alter the homeostasis of reproductive tissues and harm human pregnancy through clotting disruption, fetal membrane weakening, and premature cervical remodeling.

Mechanistic Insights into Immune Suppression and Evasion in Bacterial Vaginosis

The immunological response to bacterial vaginosis (BV) remains poorly understood and recurrent BV is still a major public health burden especially in the pregnant population. This article reviews the potential mechanisms by which BV-associated bacteria suppress and circumvent the host and microbial defence responses, and propagate their survival/dominance without overt inflammation. We discuss the composition of cervicovaginal mucosal barrier and the mechanism by which BV circumvents host defence: the degradation of the mucosal barrier and immunoglobulin A (IgA); the BV-associated organism Gardnerella vaginalis haemolysin (vaginolysin); diminished IgA response against vaginolysin; mucosal sialic acid degradation, foraging and depletion; inhibition of IL-8-induced neutrophilic infiltration; and metabolite-induced incapacitation of neutrophil and monocyte chemotaxis. We also highlight the tolerance/resistance to both host and antimicrobial molecules mounted by BV-associated biofilms. A plausible role of sialic acid-binding immunoglobulin-like lectins (SIGLECS) was also suggested. Sialidase, which is often produced by G. vaginalis, is central to the immunosuppression, relapse and recurrence observed in BV, although it is supported by other hydrolytic enzymes, vaginolysin and immunomodulatory metabolites.

Development of an enzymatic method for the evaluation of protein deposition on contact lenses

The aim of this study was to evaluate a new digestion method to quantify protein deposition on contact lenses. Four silicone hydrogel and one hydrogel contact lens material were incubated in lactoferrin, lysozyme, immunoglobulin A, and bovine serum albumin solutions at approximate physiological concentrations and temperature. Immobilized trypsin was used to digest the protein deposits from the contact lens surfaces. The total protein absorbed to lenses was extracted and digested using sequencing grade trypsin. The tryptic peptides were quantified using selected reaction monitoring mass spectrometry. The concentration of surface protein deposits was either lower than or the same as the total protein for all lens types and proteins. Immobilised trypsin can digest protein deposits from the surface of contact lenses. This ability to analyse the amount of protein at a contact lens surface may help in elucidating the effect of surface deposition on clinical outcomes during lens wear.

Activity of the glycosidases β-galactosidase, α-l-fucosidase, β-N-acetyl-hexosaminidase, and sialidase in uterine tissues from female dogs in diestrus with and without pyometra

This study aimed to compare the activity of selected glycosidases (β-galactosidase, α-l-fucosidase, β-N-acetyl-hexosaminidase, and sialidase) in homogenates of uterine tissues obtained from female dogs with and without pyometra. In addition, it examined the availability of substrates for these glycosidases in the homogenates. The study was carried out on female dogs undergoing ovariohysterectomy for pyometra (n = 10) and clinically healthy dogs (n = 10) undergoing elective spaying. The activity of β-galactosidase, α-l-fucosidase, and β-N-acetyl-hexosaminidase was analyzed using a spectrofluorometer and that of sialidase using a colorimetric method. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis with Alcian Blue (AB) and Periodic Acid-Schiff (PAS) staining was performed to determine the presence of substrates for these glycosidases in the homogenates of uterine tissues. The results revealed that the activity of all the examined glycosidases was significantly higher (P < 0.05) in the uterine tissues isolated from dogs with pyometra in comparison to healthy dogs. The electrophoretic patterns of the selected samples showed several proteins, which contained different sugar moieties stained by AB and PAS and the profiles differed significantly between the pyometra group and the healthy group. Densitometric analysis of AB staining showed patterns between 233 and 148, 86 and 55, and 43 and 20 kDa, which differed markedly in sugar content between the examined groups of animals. Similarly, PAS staining analysis revealed patterns of different molecular weights, between 233 and 117 and between 55 and 32 kDa, which also differed in sugar content. These findings suggest that canine pyometra is accompanied by the increase in the activity of selected glycosidases in the uterus. This could potentially modify the glycan structures of uterine glycoproteins and in result their biological functions. Further studies are needed to elucidate the potential role of the increased activity of glycosidases in the pathogenesis of this disease.

The prevalence of human papillomavirus and bacterial vaginosis among young women in China: a cross-sectional study

Background

The natural history of human papillomavirus (HPV) is influenced by vaginal microenvironment disorders, such as bacterial vaginosis (BV). The objective of this study was to assess the epidemiology of HPV combined with BV prevalence among Chinese women aged 20–35 years.

Methods

A total of 2000 sexually active women aged 20–35 years voluntarily enrolled in this study and underwent a ThinPrep cytologic test and PCR-reverse dot blot human papillomavirus genotyping (PCR-RDB HPV test). BV was diagnosed if clue cells were observed (20% more than epithelial cells).

Results

The overall HPV infection rate in this population was 16.2% (324/2000). Compared with HPV-negative individuals, BV prevalence was higher in the High-risk human papillomavirus (HR-HPV) (5.9% vs. 3.1%, P < 0.001). BV and HPV-51, -52 infection were more commonly associated with each other. In patients with cervical lesions (≥ CIN 1), the BV prevalence rate was higher than in patients with negative for intraepithelial lesion or malignancy (NILM) (11.9% vs. 3.8%, P = 0.002).

Conclusion

BV was found to be related to HPV-51, -52 infections and cervical lesions. To better manage HPV infected population, more attention should be paid to the prevention and proper treatment of BV.

Vaginal sialoglycan foraging by Gardnerella vaginalis: mucus barriers as a meal for unwelcome guests?

Bacterial vaginosis (BV) is a condition of the vaginal microbiome in which there are few lactobacilli and abundant anaerobic bacteria. Members of the genus Gardnerella are often one of the most abundant bacteria in BV. BV is associated with a wide variety of poor health outcomes for women. It has been recognized since the 1980s that women with BV have detectable and sometimes markedly elevated levels of sialidase activity in vaginal fluids and that bacteria associated with this condition produce this activity in culture. Mounting evidence collected using diverse methodologies points to the conclusion that BV is associated with a reduction in intact sialoglycans in cervicovaginal secretions. Here we review evidence for the contributions of vaginal bacteria, especially Gardnerella, in the processes of mucosal sialoglycan degradation, uptake, metabolism and depletion. Our understanding of the impacts of vaginal sialoglycan degradation is still limited. However, the potential implications of sialic acid depletion are discussed in light of our current understanding of the roles played by sialoglycans in vaginal physiology.

Discrimination of Gardnerella Species by Combining MALDI-TOF Protein Profile, Chaperonin cpn60 Sequences, and Phenotypic Characteristics

The description of Gardnerella vaginalis was recently updated and three new species, including nine genome species within Gardnerella, were defined using whole genome sequences and matrix assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. A fast and simple method based on readily available techniques would be of immense use to identify Gardnerella species in research and clinical practice. Here we show that 34 previously characterized Gardnerella isolates were assigned to the species using partial chaperonin cpn60 sequences. The MALDI Biotyper from Bruker Daltonik GmbH demonstrated the capability to differentiate the phylogenetically diverse groups composed of G. vaginalis/G. piotii and G. leopoldii/G. swidsinskii. Among the phenotypic properties that characterize Gardnerella species are sialidase and β-galactosidase activities. Our data confirmed that the NanH3 enzyme is responsible for sialidase activity in Gardnerella spp. isolates. Almost all G. piotii isolates displayed a sialidase positive phenotype, whereas the majority of G. vaginalis strains were sialidase negative. G. leopoldii and G. swidskinskii displayed a sialidase negative phenotype. β-galactosidase is produced exclusively in G. vaginalis strains. Earlier determined phenotypic characteristics associated with virulence of Gardnerella isolates now assigned to the defined species may provide insights on how diverse species contribute to shaping the vaginal microbiome.

Immunoglobulin A Glycosylation and Its Role in Disease

Human IgA is comprised of two subclasses, IgA1 and IgA2. Monomeric IgA (mIgA), polymeric IgA (pIgA), and secretory IgA (SIgA) are the main molecular forms of IgA. The production of IgA rivals all other immunoglobulin isotypes. The large quantities of IgA reflect the fundamental roles it plays in immune defense, protecting vulnerable mucosal surfaces against invading pathogens. SIgA dominates mucosal surfaces, whereas IgA in circulation is predominately monomeric. All forms of IgA are glycosylated, and the glycans significantly influence its various roles, including antigen binding and the antibody effector functions, mediated by the Fab and Fc portions, respectively. In contrast to its protective role, the aberrant glycosylation of IgA1 has been implicated in the pathogenesis of autoimmune diseases, such as IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN). Furthermore, detailed characterization of IgA glycosylation, including its diverse range of heterogeneity, is of emerging interest. We provide an overview of the glycosylation observed for each subclass and molecular form of IgA as well as the range of heterogeneity for each site of glycosylation. In many ways, the role of IgA glycosylation is in its early stages of being elucidated. This chapter provides an overview of the current knowledge and research directions.

Immunoglobulin A and the microbiome

The trillions of microbes that constitutively colonize the intestine (the gut microbiota) impact diverse aspects of human physiology in health and disease. Immunoglobulin A (IgA) is the most abundant antibody isotype produced at mucosal surfaces, and nearly two grams of IgA is secreted into the intestine every day. Secretory IgA (SIgA) provides critical protection against pathogens and toxins, but can also directly bind to and 'coat' commensal bacteria in the gut. Commensal targeting by SIgA shapes gut microbiota composition, modulates bacterial behaviors, and enforces host-microbiota homeostasis in both mice and humans.

Glycan cross-feeding supports mutualism between Fusobacterium and the vaginal microbiota

Women with bacterial vaginosis (BV), an imbalance of the vaginal microbiome, are more likely to be colonized by potential pathogens such as Fusobacterium nucleatum, a bacterium linked with intrauterine infection and preterm birth. However, the conditions and mechanisms supporting pathogen colonization during vaginal dysbiosis remain obscure. We demonstrate that sialidase activity, a diagnostic feature of BV, promoted F. nucleatum foraging and growth on mammalian sialoglycans, a nutrient resource that was otherwise inaccessible because of the lack of endogenous F. nucleatum sialidase. In mice with sialidase-producing vaginal microbiotas, mutant F. nucleatum unable to consume sialic acids was impaired in vaginal colonization. These experiments in mice also led to the discovery that F. nucleatum may also “give back” to the community by reinforcing sialidase activity, a biochemical feature of human dysbiosis. Using human vaginal bacterial communities, we show that F. nucleatum supported robust outgrowth of Gardnerella vaginalis, a major sialidase producer and one of the most abundant organisms in BV. These results illustrate that mutually beneficial relationships between vaginal bacteria support pathogen colonization and may help maintain features of dysbiosis. These findings challenge the simplistic dogma that the mere absence of “healthy” lactobacilli is the sole mechanism that creates a permissive environment for pathogens during vaginal dysbiosis. Given the ubiquity of F. nucleatum in the human mouth, these studies also suggest a possible mechanism underlying links between vaginal dysbiosis and oral sex.

Bacterial mutualism involving the prominent oral bacterium Fusobacterium nucleatum may drive vaginal dysbiosis in women and could help to explain the clinical correlations between vaginal dysbiosis and oral sex.

Bacterial Vaginosis: Current Diagnostic Avenues and Future Opportunities

A healthy female genital tract harbors a microbiome dominated by lactic acid and hydrogen peroxide producing bacteria, which provide protection against infections by maintaining a low pH. Changes in the bacterial compositions of the vaginal microbiome can lead to bacterial vaginosis (BV), which is often associated with vaginal inflammation. Bacterial vaginosis increases the risk of acquiring sexually transmitted infections (STIs) like human immunodeficiency virus (HIV) and affects women's reproductive health negatively. In pregnant women, BV can lead to chorioamnionitis and adverse pregnancy outcomes, including preterm premature rupture of the membranes and preterm birth. In order to manage BV effectively, good diagnostic procedures are required. Traditionally clinical and microscopic methods have been used to diagnose BV; however, these methods require skilled staff and time and suffer from reduced sensitivity and specificity. New diagnostics, including highly sensitive and specific point-of-care (POC) tests, treatment modalities and vaccines can be developed based on the identification of biomarkers from the growing pool of vaginal microbiome and vaginal metabolome data. In this review the current and future diagnostic avenues will be discussed.

Production and characterization of a monoclonal antibody against the sialidase of Gardnerella vaginalis using a synthetic peptide in a MAP8 format

Abstract

Bacterial vaginosis is one of the most frequent vaginal infections. Its main etiological agent is Gardnerella vaginalis, which produces several virulence factors involved in vaginal infection and colonization, in particular, sialidase (SLD), a potential clinical biomarker that participates in immune response modulation and mucus degradation. The main objective of this work was the production and evaluation of a monoclonal antibody against G. vaginalis sialidase and its validation in immunoassays. For immunization of mice, a synthetic multiantigenic peptide was used, and hybridomas were generated. After fusion, hybridomas were evaluated for antibody production and cloned by limited dilution. One clone producing IgG1 was selected and characterized by indirect ELISA, dot blot, and Western blot, and we also tested clinical isolates and HeLa cells infected with G. vaginalis. The results showed that the anti-SLD antibody recognized a single protein of ~90 kDa that correlated with the estimated molecular weight of SLD. In addition, anti-SLD antibody recognized SLD from complete bacteria and from culture supernatants of infected Hela cells. In conclusion, our results showed that the anti-SLD antibody recognized SLD from different sources and could be considered a new tool for the diagnosis of bacterial vaginosis.

Key Points

• Anti-sialidase mAb was generated using a synthetic peptide

• The mAb recognizes synthetic peptide and intact protein from multiple sources

• The antibody was characterized by several immunological methods

Associations between the vaginal microbiome and Candida colonization in women of reproductive age

BACKGROUND

The composition of bacteria within the vaginal microbiome has garnered a lot of recent attention and has been associated with reproductive health and disease. Despite the common occurrence of yeast (primarily Candida) within the vaginal microbiome, there is still an incomplete picture of relationships between yeast and bacteria (especially lactobacilli), as well as how such associations are governed. Such relationships could be important to a more holistic understanding of the vaginal microbiome and its connection to reproductive health.

OBJECTIVE

The objective of the study was to perform molecular characterization of clinical specimens to define associations between vaginal bacteria (especially Lactobacillus species) and Candida colonization. In vitro studies were conducted to test the 2 most common dominant Lactobacillus species (Lactobacillus crispatus and Lactobacillus iners) in their ability to inhibit Candida growth and to examine the basis for such inhibition.

STUDY DESIGN

A nested cross-sectional study of reproductive-age women from the Contraceptive CHOICE Project was conducted. Vaginal swabs from 299 women were selected to balance race and bacterial vaginosis status, resulting in a similar representation of black and white women in each of the 3 Nugent score categories (normal [0-3], intermediate [4-6], and bacterial vaginosis [7-10]). Sequencing of the 16S ribosomal gene (V4 region) was used to determine the dominant Lactobacillus species present (primarily Lactobacillus iners and Lactobacillus crispatus), defined as >50% of the community. Subjects without dominance by a single Lactobacillus species were classified as Diverse. A Candida-specific quantitative polymerase chain reaction targeting the internally transcribed spacer 1 was validated using vaginal samples collected from a second cohort of women and used to assess Candida colonization. Two hundred fifty-five nonpregnant women with sufficient bacterial biomass for analysis were included in the final analysis. Generalized linear models were used to evaluate associations between Lactobacillus dominance, sociodemographic and risk characteristics, and vaginal Candida colonization. In separate in vitro studies, the potential of cell-free supernatants from Lactobacillus crispatus and Lactobacillus iners cultures to inhibit Candida growth was evaluated.

RESULTS

Forty-two women (16%) were vaginally colonized with Candida. Microbiomes characterized as Diverse (38%), Lactobacillus iners-dominant (39%), and Lactobacillus crispatus-dominant (20%) were the most common. The microbiome, race, and Candida colonization co-varied with a higher prevalence of Candida among black women and Lactobacillus iners-dominant communities compared with white women and Lactobacillus crispatus-dominant communities. Lactobacillus iners-dominant communities were more likely to harbor Candida than Lactobacillus crispatus-dominant communities (odds ratio, 2.85, 95% confidence interval, 1.03-7.21; Fisher exact test, P = .048). In vitro, Lactobacillus crispatus produced greater concentrations of lactic acid and exhibited significantly more pH-dependent growth inhibition of Candida albicans, suggesting a potential mechanism for the clinical observations.

CONCLUSION

In nonpregnant women, Lactobacillus iners-dominant communities were significantly more likely to harbor Candida than Lactobacillus crispatus-dominant communities, suggesting that Lactobacillus species have different relationships with Candida. In vitro experiments indicate that Lactobacillus crispatus may impede Candida colonization more effectively than Lactobacillus iners through a greater production of lactic acid.

Characterization of Porphyromonas gingivalis sialidase and disruption of its role in host-pathogen interactions

Key to onset and progression of periodontitis is a complex relationship between oral bacteria and the host. The organisms most associated with severe periodontitis are the periodontal pathogens of the red complex: Tannerella forsythia, Treponema denticola and Porphyromonas gingivalis. These organisms express sialidases, which cleave sialic acid from host glycoproteins, and contribute to disease through various mechanisms. Here, we expressed and purified recombinant P. gingivalis sialidase SiaPG (PG_0352) and characterized its activity on a number of substrates, including host sialoglycoproteins and highlighting the inability to cleave diacetylated sialic acids - a phenomenon overcome by the NanS sialate-esterase from T. forsythia. Indeed SiaPG required NanS to maximize sialic acid harvesting from heavily O-acetylated substrates such as bovine salivary mucin, hinting at the possibility of interspecies cooperation in sialic acid release from host sources by these members of the oral microbiota. Activity of SiaPG and P. gingivalis was inhibited using the commercially available chemotherapeutic zanamivir, indicating its potential as a virulence inhibitor, which also inhibited sialic acid release from mucin, and was capable of inhibiting biofilm formation of P. gingivalis on oral glycoprotein sources. Zanamivir also inhibited attachment and invasion of oral epithelial cells by P. gingivalis and other periodontal pathogens, both in monospecies but also in multispecies infection experiments, indicating potential to suppress host-pathogen interactions of a mixed microbial community. This study broadens our understanding of the multifarious roles of bacterial sialidases in virulence, and indicates that their inhibition with chemotherapeutics could be a promising strategy for periodontitis therapy.

Does Aerobic Vaginitis Have Adverse Pregnancy Outcomes? Prospective Observational Study

Background

Aerobic vaginitis (AV) is an aberration within the balanced vaginal microbiota. Only few reports have documented the adverse pregnancy outcomes related to AV. Nonetheless, the exact role of AV in pregnancy and the potential benefit of its screening need further study. Our goal was to evaluate the association between aerobic vaginitis (AV) in late pregnancy and maternal and neonatal outcomes.

Methods

In this prospective observational study, a total of 600 singleton pregnant women with intact fetal membranes at a gestational age of 34-36 weeks were recruited (one hundred women with AV and 500 pregnant women without AV). The study protocol excluded patients with other forms of vaginal infection. Pregnancy outcomes were traced and documented. The primary outcome was the association between AV and preterm labor. The current study compared the maternal and neonatal outcomes among pregnant women with and without AV in unadjusted and adjusted analyses with the odds ratio (OR) and 95% confidence interval (CI) reported.

Results

There was an association between AV and with preterm birth (adjusted OR 3.06, 95% CI 1.58-5.95) and prelabor rupture of membranes (adjusted OR 6.17, 95% CI 3.24-11.7). For neonatal outcomes, AV was associated with a higher incidence of neonatal ICU admission (adjusted OR 2.19, 95% CI 1.1-4.34). Severe forms of AV significantly increased the incidence of PTB (p = 0.0014) and PROM (p = 0.0094) when compared to less severe forms of AV.

Conclusion

AV is common in late pregnancy and is linked to a diversity of adversative pregnancy outcomes including preterm birth, PROM, and neonatal ICU admission. Moreover, the incidence of PTB and PROM might further increase with the severity of AV. Clinicians should pay more consideration to vaginal microbiota assessment during pregnancy.

Prediction of bacterial vulvovaginitis in girls at different Tanner stages of sexual development

At present, there is a paucity of research studies that comprehensively investigate the factors causing vulvovaginitis in young females. The aim of this work was to propose an algorithm for predicting the risk of vulvovaginitis in young girls and adolescents. The study recruited 252 healthy girls, who were stratified into a few groups depending on their sexual development on the Tanner scale. The composition of vaginal microbiota was determined in all the participants using real-time polymerase chain reaction (PCR); distribution of allele and genotype frequencies was assessed for the polymorphic variants of genes coding for pro- and anti-inflammatory cytokines. Based on the obtained data, we created a functional model for predicting the risk of vulvovaginitis in girls at different stages of sexual development. Favorable risk factors for Tanner I girls included predominance of obligate anaerobes in vaginal microbiota and the polymorphic IL10 variant (C-819T) homozygous for TT. The sensitivity of the model was 80%, its specificity was 78%. Favorable risk factors for prepubertal and pubertal girls included predominance of aerobes in the composition of vaginal microbiota and the presence of the TT allele in the polymorphic IL10 gene variant (C-3953T). The sensitivity of the model was 58.3%, whereas specificity, 94.1%. This study provides the rationale conforming with the principles of evidence-based medicine for using prevention measures in the groups at risk for vulvovaginitis at young age. The proposed measures allowed us to reduce the relapse rate of bacterial vulvovaginitis threefold.

Rapid production of a chimeric antibody-antigen fusion protein based on 2A-peptide cleavage and green fluorescent protein expression in CHO cells

To enable large-scale antibody production, the creation of a stable, high producer cell line is essential. This process often takes longer than 6 months using standard limited dilution techniques and is very labor intensive. The use of a tri-cistronic vector expressing green fluorescent protein (GFP) and both antibody chains, separated by a GT2A peptide sequence, allows expression of all proteins under a single promotor in equimolar ratios. By combining the advantages of 2A peptide cleavage and single cell sorting, a chimeric antibody-antigen fusion protein that contained the variable domains of mouse IgG with a porcine IgA constant domain fused to the FedF antigen could be produced in CHO-K1 cells. After transfection, a strong correlation was found between antibody production and GFP expression (r = 0.69) using image analysis of formed monolayer patches. This enables the rapid selection of GFP-positive clones using automated image analysis for the selection of high producer clones. This vector design allowed the rapid selection of high producer clones within a time-frame of 4 weeks after transfection. The highest producing clone had a specific antibody productivity of 2.32 pg/cell/day. Concentrations of 34 mg/L were obtained using shake-flask batch culture. The produced recombinant antibody showed stable expression, binding and minimal degradation. In the future, this antibody will be assessed for its effectiveness as an oral vaccine antigen.

Identification and characterization of NanH2 and NanH3, enzymes responsible for sialidase activity in the vaginal bacterium Gardnerella vaginalis

Gardnerella vaginalis is abundant in bacterial vaginosis (BV), a condition associated with adverse reproductive health. Sialidase activity is a diagnostic feature of BV and is produced by a subset of G. vaginalis strains. Although its genetic basis has not been formally identified, sialidase activity is presumed to derive from the sialidase A gene, named here nanH1 In this study, BLAST searches predicted two additional G. vaginalis sialidases, NanH2 and NanH3. When expressed in Escherichia coli, NanH2 and NanH3 both displayed broad abilities to cleave sialic acids from α2-3- and α2-6-linked N- and O-linked sialoglycans, including relevant mucosal substrates. In contrast, recombinant NanH1 had limited activity against synthetic and mucosal substrates under the conditions tested. Recombinant NanH2 was much more effective than NanH3 in cleaving sialic acids bearing a 9-O-acetyl ester. Similarly, G. vaginalis strains encoding NanH2 cleaved and foraged significantly more Neu5,9Ac₂ than strains encoding only NanH3. Among a collection of 34 G. vaginalis isolates, nanH2, nanH3, or both were present in all 15 sialidase-positive strains but absent from all 19 sialidase-negative isolates, including 16 strains that were nanH1-positive. We conclude that NanH2 and NanH3 are the primary sources of sialidase activity in G. vaginalis and that these two enzymes can account for the previously described substrate breadth cleaved by sialidases in human vaginal specimens of women with BV. Finally, PCRs of nanH2 or nanH3 from human vaginal specimens had 81% sensitivity and 78% specificity in distinguishing between Lactobacillus dominance and BV, as determined by Nugent scoring.

Phenotypic characterization of Gardnerella vaginalis subgroups suggests differences in their virulence potential

The well-known genotypic and phenotypic diversity of G. vaginalis resulted in its classification into at least four subgroups (clades) with diverse genomic properties. To evaluate the virulence potential of G. vaginalis subgroups, we analyzed the virulence-related phenotypic characteristics of 14 isolates of clade 1, 12 isolates of clade 2, 8 isolates of clade 4 assessing their in vitro ability to grow as a biofilm, produce the toxin vaginolysin, and express sialidase activity. Significant differences in VLY production were found (p = 0.023), but further analysis of clade pairs did not confirm this finding. The amount of biofim did not differ significantly among the clades. Analysis of sialidase activity indicated statistically significant differences among the clades (p < 0.001). Production of active recombinant G. vaginalis sialidase demonstrated the link between the sld gene and enzymatic activity, which may be differentially regulated at the transcriptional level. Statistical classification analysis (random forests algorithm) showed that G. vaginalis clades could be best defined by the profiles of two phenotypic characteristics: sialidase activity and vaginolysin production. The results of principal component analysis and hierarchical clustering suggested that all isolates can be subgrouped into three clusters, the structures of which are determined based on phenotypic characteristics of the isolates. Clade 4 was the most homogenous group, as all isolates were found in the same cluster, which is characterized by low production of all studied virulence factors. Clade 2 isolates were mainly distributed between two clusters, whereas clade 1 isolates were found in all three clusters that were characterized by a distinct profile of phenotypic characteristics. Our findings suggest that G. vaginalis subgroups with different virulence potential might play distinct roles in vaginal microbiota.

Inhibition of sialidase activity and cellular invasion by the bacterial vaginosis pathogen Gardnerella vaginalis

Bacterial vaginosis is a genital tract infection, thought to be caused by transformation of a lactobacillus-rich flora to a dysbiotic microbiota enriched in mixed anaerobes. The most prominent of these is Gardnerella vaginalis (GV), an anaerobic pathogen that produces sialidase enzyme to cleave terminal sialic acid residues from human glycans. Notably, high sialidase activity is associated with preterm birth and low birthweight. We explored the potential of the sialidase inhibitor Zanamavir against GV whole cell sialidase activity using methyl–umbelliferyl neuraminic acid (MU-NANA) cleavage assays, with Zanamavir causing a 30% reduction in whole cell GV sialidase activity (p < 0.05). Furthermore, cellular invasion assays using HeLa cervical epithelial cells, infected with GV, demonstrated that Zanamivir elicited a 50% reduction in cell association and invasion (p < 0.05). Our data thus highlight that pharmacological sialidase inhibitors are able to modify BV-associated sialidase activity and influence host–pathogen interactions and may represent novel therapeutic adjuncts.

Association of asymptomatic bacterial vaginosis with persistence of female genital human papillomavirus infection

More data are needed on the role of abnormal vaginal microbiota in the natural history of cervical human papillomavirus (HPV) infections. Our purpose was to study the prevalence of mixed flora (MF), bacterial vaginosis (BV) and yeast infection in women with known HPV outcomes during the 72-month follow-up (FU). Asymptomatic pregnant women (N = 329) were enrolled in the third trimester of their pregnancy. Pap smears and HPV genotyping samples were taken at baseline and at 12-, 24-, 36- and 72-month FU visits, with one additional sample at 2 months for HPV. HPV testing was done with nested PCR and Multimetrix assay to determine the point prevalence and persistence of HPV. Conventional Pap smears were scored for MF, BV and yeast infection. Covariates of the outcomes were analyzed using generalized estimating equation (GEE) and Poisson regression. Of the women, 76.6% (252/329) tested HPV-positive at least once during the FU. BV was detected in 12.2% (40/329), MF in 57.4% (189/329) and yeast infection in 22.9% (73/329) of the women. HPV-positive women had significantly more leucocytes in their Pap smear (p = 0.023) than the HPV-negative ones. MF (OR 2.75, 95% CI 1.77-4.27) and yeast infection (p = 0.007) were linked with HPV positivity. BV but not yeast infection was a significant covariate of HPV persistence (p = 0.024; OR 2.15, 95% CI 1.13-4.08). MF and yeast infection were associated with prevalent cervical HPV infection. In the longitudinal setting, BV predicted HPV persistence, implicating that treatment of asymptomatic BV in women with cervical HR-HPV infections might be justified.

Aerobic vaginitis: no longer a stranger

Aerobic vaginitis (AV) is the name given in 2002 to a vaginal infectious entity which was not recognized as such before. It is characterized by abnormal (dysbiotic) vaginal microflora containing aerobic, enteric bacteria, variable levels of vaginal inflammation and deficient epithelial maturation. Although AV and bacterial vaginosis (BV) share some characteristics, such as a diminished number or absence of lactobacilli, increased discharge (fishy smelling in BV, while in severe forms of AV, a foul, rather rotten smell may be present) and increased pH (often more pronounced in AV), there are also striking differences between the two. There is no inflammation in women with BV, whereas the vagina of women with AV often appears red and edematous, and may even display small erosions or ulcerations. The color of the discharge in BV is usually whitish or gray and of a watery consistency, whereas in AV it is yellow to green and rather thick and mucoid. Women with BV do not have dyspareunia, while some women with severe AV do. Finally, the microscopic appearance differs in various aspects, such as the presence of leucocytes and parabasal or immature epithelial cells in AV and the absence of the granular aspect of the microflora, typical of BV. Despite all these differences, the distinction between AV and BV was not recognized in many former studies, leading to incomplete and imprecise diagnostic workouts and erroneous management of patients in both clinical and research settings. The prevalence of AV ranges between 7 and 12%, and is therefore less prevalent than BV. Although still largely undiagnosed, many researchers and clinicians increasingly take it into account as a cause of symptomatic vaginitis. AV can co-occur with other entities, such as BV and candidiasis. It can be associated with dyspareunia, sexually transmitted infections (such as human papilloma virus, human immunodeficiency virus, Trichomonas vaginalis and Chlamydia trachomatis), chorioamnionitis, fetal infection, preterm birth and cervical dysplasia. Many other possible pathological associations are currently under investigation. The diagnosis of AV is made using wet mount microscopy, ideally using phase contrast. An AV score is calculated, according to: lactobacillary grade, presence of inflammation, proportion of toxic leucocytes, characteristics of the microflora and presence of immature epithelial cells. To circumvent the hurdle of microscopic investigation, some groups have begun to develop nucleic-acid-based and enzymatic diagnostic tests, but the detailed information obtained with phase contrast microscopy is irreplaceable. The best treatment is not yet fully determined, but it must be tailored according to the microscopic findings and the patient's needs. There is a role for local estrogen therapy, corticosteroids, antimicrobials and probiotics. Further research will reveal more precise data on diagnosis, pathogenesis, management and prevention.

Etiology of bacterial vaginosis and polymicrobial biofilm formation

Microorganisms in nature rarely exist in a planktonic form, but in the form of biofilms. Biofilms have been identified as the cause of many chronic and persistent infections and have been implicated in the etiology of bacterial vaginosis (BV). Bacterial vaginosis is the most common form of vaginal infection in women of reproductive age. Similar to other biofilm infections, BV biofilms protect the BV-related bacteria against antibiotics and cause recurrent BV. In this review, an overview of BV-related bacteria, conceptual models and the stages involved in the polymicrobial BV biofilm formation will be discussed.

The presence of the putative Gardnerella vaginalis sialidase A gene in vaginal specimens is associated with bacterial vaginosis biofilm

Bacterial vaginosis (BV) is a difficult-to-treat recurrent condition in which health-associated lactobacilli are outnumbered by other anaerobic bacteria, such as Gardnerella vaginalis. Certain genotypes of G. vaginalis can produce sialidase, while others cannot. Sialidase is known to facilitate the destruction of the protective mucus layer on the vaginal epithelium by hydrolysis of sialic acid on the glycans of mucous membranes. This process possibly facilitates adhesion of bacterial cells on the epithelium since it has been linked with the development of biofilm in other pathogenic conditions. Although it has not been demonstrated yet, it is probable that G. vaginalis benefits from this mechanism by attaching to the vaginal epithelium to initiate biofilm development. In this study, using vaginal specimens of 120 women enrolled in the Ring Plus study, we assessed the association between the putative G. vaginalis sialidase A gene by quantitative polymerase chain reaction (qPCR), the diagnosis of BV according to Nugent score, and the occurrence of a BV-associated biofilm dominated by G. vaginalis by fluorescence in situ hybridisation (FISH). We detected the putative sialidase A gene in 75% of the G. vaginalis-positive vaginal specimens and found a strong association (p<0.001) between the presence of a G. vaginalis biofilm, the diagnosis of BV according to Nugent and the detection of high loads of the G. vaginalis sialidase A gene in the vaginal specimens. These results could redefine diagnosis of BV, and in addition might guide research for new treatment.

Cervicovaginal cytokines, sialidase activity and bacterial load in reproductive-aged women with intermediate vaginal flora

Studies have shown that not only bacterial vaginosis, but also intermediate vaginal flora has deleterious effects for women's reproductive health. However, literature still lacks information about microbiological and immunological aspects of intermediate flora.

OBJECTIVE

To characterize intermediate flora regarding levels of Interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor-alpha, interleukin 1 receptor antagonist (IL-1ra), IL-10, sialidase; loads of Gardnerella vaginalis, total bacteria and to verify whether it is closer related to normal flora or bacterial vaginosis. This cross-sectional study enrolled 526 non-pregnant reproductive-aged women distributed in 3 groups according to pattern of vaginal flora using Nugent's system in normal, intermediate and bacterial vaginosis. Cervicovaginal levels of cytokines, sialidases, loads of G. vaginalis and total bacteria were assessed by ELISA, conversion of MUAN and quantitative real-time PCR, respectively. A principal component analysis(PCA) using all measured parameters was performed to compare the three different types of flora. Results showed that intermediate flora is associated with increased cervicovaginal IL-1beta in relation to normal flora(P<0.0001). When compared to bacterial vaginosis, intermediate flora has higher IL-8 and IL-10 levels(P<0.01). Sialidases were in significantly lower levels in normal and intermediate flora than bacterial vaginosis(P<0.0001). Loads of G. vaginalis and total bacterial differed among all groups(P<0.0001), being highest in bacterial vaginosis. PCA showed that normal and intermediate flora were closely scattered, while bacterial vaginosis were grouped separately.

CONCLUSION

Although intermediate flora shows some differences in cytokines, sialidases and bacterial loads in relation to normal flora and bacterial vaginosis, when taken together, general microbiological and immunological pattern pattern of intermediate flora resembles the normal flora.

The Effects of Hormones and Vaginal Microflora on the Glycome of the Female Genital Tract: Cervical-Vaginal Fluid

In this study, we characterized the glycome of cervical-vaginal fluid, collected with a Catamenial cup. We quantified: glycosidase levels; sialic acid and high mannose specific lectin binding; mucins, MUC1, MUC4, MUC5AC, MUC7; and albumin in the samples collected. These data were analyzed in the context of hormonal status (day of menstrual cycle, hormonal contraception use) and role, if any, of the type of the vaginal microflora present. When the Nugent score was used to stratify the subjects by microflora as normal, intermediate, or bacterial vaginosis, several important differences were observed. The activities of four of six glycosidases in the samples from women with bacterial vaginosis were significantly increased when compared to normal or intermediate women: sialidase, P = <0.001; α-galactosidase, P = 0.006; β-galactosidase, P = 0.005; α-glucosidase, P = 0.056. Sialic acid binding sites as measured by two lectins, Maackia amurensis and Sambucus nigra binding, were significantly lower in women with BV compared to women with normal and intermediate scores (P = <0.0001 and 0.008 respectively). High mannose binding sites, a measure of innate immunity were also significantly lower in women with BV (P = <0.001). Additionally, we observed significant increases in MUC1, MUC4, MUC5AC, and MUC7 concentrations in women with BV (P = <0.001, 0.001, <0.001, 0.02 respectively). Among normal women we found that the membrane bound mucin MUC4 and the secreted MUC5AC were decreased in postmenopausal women (P = 0.02 and 0.07 respectively), while MUC7 (secreted) was decreased in women using levonorgestrel-containing IUDs (P = 0.02). The number of sialic acid binding sites was lower in the postmenopausal group (P = 0.04), but the number of high mannose binding sites, measured with Griffithsin, was not significantly different among the 6 hormonal groups. The glycosidase levels in the cervical-vaginal mucus were rather low in the groups, with exception of α-glucosidase activity that was much lower in the postmenopausal group (P<0.001). These studies present compelling evidence that the vaginal ecosystem responds to the presence of different vaginal microorganisms. These effects were so influential that it required us to remove subjects with BV for data interpretation of the impact of hormones. We also suggest that certain changes occurring in vaginal/cervical proteins are due to bacteria or their products. Therefore, the quantitation of vaginal mucins and lectin binding offers a new method to monitor bacteria-host interactions in the female reproductive tract. The data suggest that some of the changes in these components are the result of host processing, such as the increases in mucin content, while the microflora is responsible for the increases in glycosidases and the decreases in lectin binding. The methods should be considered a valid marker for insult to the female genital tract.

The vaginal microbiota, host defence and reproductive physiology

The interaction between the human host and the vaginal microbiota is highly dynamic. Major changes in the vaginal physiology and microbiota over a woman's lifetime are largely shaped by transitional periods such as puberty, menopause and pregnancy, while daily fluctuations in microbial composition observed through culture-independent studies are more likely to be the results of daily life activities and behaviours. The vaginal microbiota of reproductive-aged women is largely made up of at least five different community state types. Four of these community state types are dominated by lactic-acid producing Lactobacillus spp. while the fifth is commonly composed of anaerobes and strict anaerobes and is sometimes associated with vaginal symptoms. The production of lactic acid has been associated with contributing to the overall health of the vagina due to its direct and indirect effects on pathogens and host defence. Some species associated with non-Lactobacillus vaginal microbiota may trigger immune responses as well as degrade the host mucosa, processes that ultimately increase susceptibility to infections and contribute to negative reproductive outcomes such as infertility and preterm birth. Further studies are needed to better understand the functional underpinnings of how the vaginal microbiota affect host physiology but also how host physiology affects the vaginal microbiota. Understanding this fine-tuned interaction is key to maintaining women's reproductive health.

The bacterial etiology of preterm birth

Preterm birth is the leading cause of infant morbidity and mortality. Very preterm births, those occurring before 32 completed weeks of gestation, are associated with the greatest risks. The leading cause of very preterm birth is intrauterine infection, which can lead to an inflammatory response that triggers labor or preterm premature rupture of membranes. How bacteria invade the uterine cavity, which is normally a sterile environment, and the reasons why different species vary in their capacity to induce inflammation and preterm birth are still incompletely understood. However, advanced techniques that circumvent the need for cultivating bacteria, deep sequence analysis that allows for the comprehensive characterization of the microbiome of a given body site and detection of low-prevalence species, and transcriptomics and metabolomics approaches that shed light on the host response to bacterial invasion are all providing a more complete picture of the progression from vaginal colonization to uterine invasion to preterm labor and preterm birth.

Bacterial vaginosis in pregnant adolescents: proinflammatory cytokine and bacterial sialidase profile. Cross-sectional study

CONTEXT AND OBJECTIVE

Bacterial vaginosis occurs frequently in pregnancy and increases susceptibility to sexually transmitted infections (STI). Considering that adolescents are disproportionally affected by STI, the aim of this study was to evaluate the cervicovaginal levels of interleukin (IL)-1 beta, IL-6, IL-8 and bacterial sialidase in pregnant adolescents with bacterial vaginosis.

DESIGN AND SETTING

Cross-sectional study at mother and child referral units in Belém, Pará, Brazil.

METHODS

Vaginal samples from 168 pregnant adolescents enrolled were tested for trichomoniasis and candidiasis. Their vaginal microbiota was classified according to the Nugent criteria (1991) as normal, intermediate or bacterial vaginosis. Cervical infection due to Chlamydia trachomatisand Neisseria gonorrhoeae was also assessed. Cytokine and sialidase levels were measured, respectively, using enzyme-linked immunosorbent assays and MUAN conversion in cervicovaginal lavages. Forty-eight adolescents (28.6%) were excluded because they tested positive for some of the infections investigated. The remaining 120 adolescents were grouped according to vaginal flora type: normal (n = 68) or bacterial vaginosis (n = 52). Their cytokine and sialidase levels were compared between the groups using the Mann-Whitney test (P < 0.05).

RESULTS

The pregnant adolescents with bacterial vaginosis had higher levels of IL-1 beta, IL-6 and IL-8 (P < 0.05). Sialidase was solely detected in 35 adolescents (67.2%) with bacterial vaginosis.

CONCLUSIONS

Not only IL-1 beta and sialidase levels, but also IL-6 and IL-8 levels are higher in pregnant adolescents with bacterial vaginosis, thus indicating that this condition elicits a more pronounced inflammatory response in this population, which potentially increases vulnerability to STI acquisition.

Modeling of Virion Collisions in Cervicovaginal Mucus Reveals Limits on Agglutination as the Protective Mechanism of Secretory Immunoglobulin A

Secretory immunoglobulin A (sIgA), a dimeric antibody found in high quantities in the gastrointestinal mucosa, is broadly associated with mucosal immune protection. A distinguishing feature of sIgA is its ability to crosslink pathogens, thereby creating pathogen/sIgA aggregates that are too large to traverse the dense matrix of mucin fibers in mucus layers overlying epithelial cells and consequently reducing infectivity. Here, we use modeling to investigate this mechanism of “immune exclusion” based on sIgA-mediated agglutination, in particular the potential use of sIgA to agglutinate HIV in cervicovaginal mucus (CVM) and prevent HIV transmission. Utilizing reported data on HIV diffusion in CVM and semen, we simulate HIV collision kinetics in physiologically-thick mucus layers–a necessary first step for sIgA-induced aggregation. We find that even at the median HIV load in semen of acutely infected individuals possessing high viral titers, over 99% of HIV virions will penetrate CVM and reach the vaginal epithelium without colliding with another virion. These findings imply that agglutination is unlikely to be the dominant mechanism of sIgA-mediated protection against HIV or other sexually transmitted pathogens. Rather, we surmise that agglutination is most effective against pathogens either present at exceedingly high concentrations or that possess motility mechanisms other than Brownian diffusion that significantly enhance encounter rates.

Bacterial glycosidases in pathogenesis and glycoengineering

Glycosylation is a common post-translational protein modification and many key proteins of the immune system are glycosylated. As the true experts of our immune system, pathogenic bacteria produce enzymes that can modify the carbohydrates (glycans) of the defense mechanisms in order to favor bacterial survival and persistence. At the intersection between bacterial pathogenesis and glycobiology, there is an increased interest in studying the bacterial enzymes that modify the protein glycosylation of their colonized or infected hosts. This is of great importance in order to fully understand bacterial pathogenesis, but it also presents itself as a valuable source for glycoengineering and glycoanalysis tools. This article highlights the role of bacterial glycosidases during infections, introduces the use of such enzymes as glycoengineering tools and discusses the potential of further studies in this emerging field.

Impact of bacterial vaginosis, as assessed by nugent criteria and hormonal status on glycosidases and lectin binding in cervicovaginal lavage samples

The objective of this study was to evaluate the impact of hormonal status and bacterial vaginosis (BV) on the glycosidases present and glycosylation changes as assessed by lectin binding to cervicovaginal lavage constituents. Frozen cervicovaginal lavage samples from a completed study examining the impact of reproductive hormones on the physicochemical properties of vaginal fluid were utilized for the present study. In the parent study, 165 women were characterized as having BV, intermediate or normal microflora using the Nugent criteria. The presence of glycosidases in the samples was determined using quantitative 4-methyl-umbelliferone based assays, and glycosylation was assessed using enzyme linked lectin assays (ELLA). Women with BV had elevated sialidase, α-galactosidase, β-galactosidase and α-glucosidase activities compared to intermediate or normal women (P<0.001, 0.003, 0.006 and 0.042 respectively). The amount of sialic acid (Sambucus nigra, P = 0.003) and high mannose (griffithsin, P<0.001) were reduced, as evaluated by lectin binding, in women with BV. When the data were stratified according to hormonal status, α-glucosidase and griffithsin binding were decreased among postmenopausal women (P<0.02) when compared to premenopausal groups. These data suggest that both hormonal status and BV impact the glycosidases and lectin binding sites present in vaginal fluid. The sialidases present at increased levels in women with BV likely reduce the number of sialic acid binding sites. Other enzymes likely reduce griffithsin binding. The alterations in the glycosidase content, high mannose and sialic acid binding sites in the cervicovaginal fluid associated with bacterial vaginosis may impact susceptibility to viruses, such as HIV, that utilize glycans as a portal of entry.

Studying the effects of reproductive hormones and bacterial vaginosis on the glycome of lavage samples from the cervicovaginal cavity

The cervicovaginal fluid (CVF) coating the vaginal epithelium is an important immunological mediator, providing a barrier to infection. Glycosylation of CVF proteins, such as mucins, IgG and S-IgA, plays a critical role in their immunological functions. Although multiple factors, such as hormones and microflora, may influence glycosylation of the CVF, few studies have examined their impact on this important immunological fluid. Herein we analyzed the glycosylation of cervicovaginal lavage (CVL) samples collected from 165 women under different hormonal conditions including: (1) no contraceptive, post-menopausal, (2) no contraceptive, days 1-14 of the menstrual cycle, (3) no contraceptive, days 15-28 of the menstrual cycle, (4) combined-oral contraceptive pills for at least 6 months, (5) depo-medroxyprogesterone acetate (Depo-Provera) injections for at least 6 months, (6) levonorgestrel IUD for at least 1 month. Glycomic profiling was obtained using our lectin microarray system, a rapid method to analyze carbohydrate composition. Although some small effects were observed due to hormone levels, the major influence on the glycome was the presence of an altered bacterial cohort due to bacterial vaginosis (BV). Compared to normal women, samples from women with BV contained lower levels of sialic acid and high-mannose glycans in their CVL. The change in high mannose levels was unexpected and may be related to the increased risk of HIV-infection observed in women with BV, as high mannose receptors are a viral entry pathway. Changes in the glycome were also observed with hormonal contraceptive use, in a contraceptive-dependent manner. Overall, microflora had a greater impact on the glycome than hormonal levels, and both of these effects should be more closely examined in future studies given the importance of glycans in the innate immune system.

Cross-Sectional Analysis of Selected Genital Tract Immunological Markers and Molecular Vaginal Microbiota in Sub-Saharan African Women, with Relevance to HIV Risk and Prevention

Data on immune mediators in the genital tract and the factors that modulate them in sub-Saharan women are limited. Cervicovaginal lavage (CVL) samples from 430 sexually active women from Kenya, South Africa, and Rwanda were analyzed for 12 soluble immune mediators using Bio-Plex and Meso Scale Discovery multiplex platforms, as well as single enzyme-linked immunosorbent assays. Ten bacterial species were quantified in vaginal swab samples. Bacterial vaginosis (BV) was defined by Nugent scoring. CVL samples from HIV-infected women showed a clear-cut proinflammatory profile. Pregnant women, adolescents, and women engaging in traditional vaginal practices differed in specific soluble markers compared to reference groups of adult HIV-negative women. Cervical mucus, cervical ectopy, abnormal vaginal discharge, and having multiple sex partners were each associated with an increase in inflammatory mediators. The levels of interleukin-1α (IL-1α), IL-1β, IL-6, IL-12(p70), and IL-8 were elevated, whereas the IL-1RA/IL-1(α+β) ratio decreased in women with BV. The level of gamma interferon-induced protein 10 was lower in BV-positive than in BV-negative women, suggesting its suppression as a potential immune evasion mechanism by BV-associated bacteria. Lactobacillus crispatus and Lactobacillus vaginalis were associated with decreased proinflammatory cytokines and each BV-associated species with increased proinflammatory cytokines. Remarkably, the in vitro anti-HIV activity of CVL samples from BV-positive women was stronger than that of BV-negative women. In conclusion, we found significant associations of factors, including vaginal microbiota, which can influence immune mediators in the vaginal environment in sexually active women. These factors need to be considered when establishing normative levels or pathogenic cutoffs of biomarkers of inflammation and associated risks in African women.

Solvothermal synthesis of ZnO nanoparticles and anti-infection application in vivo

Zinc oxide nanoparticles (ZnONPs) have been widely studied as the bacteriostatic reagents. However, synthesis of small ZnO nanoparticles with good monodispersion and stability in aqueous solution is still a challenge. Anti-infection research of ZnONPs used as antibacterial agent in vivo is rare. In this paper, a novel, sustainable, and simple method to synthesize ZnO nanoparticles with good monodispersion in aqueous low-temperature conditions and with a small molecule agent is reported. Inhibition zone test and the minimum inhibitory concentration test were performed to examine the antibacterial activity of ZnONPs against bacteria Staphylococcus aureus and Escherichia coli in vitro. For further application in vivo, low cytotoxicity and low acute toxicity in mice of ZnO were demonstrated. Finally, 4 nm ZnONPs combined with poly(vinyl alcohol) gel was used as antibacterial agent in rodent elytritis model, and significant anti-infection effect was proven. In one word, the present research would shed new light on the designing of antibacterial materials like ZnO with promising application in disinfection.