HIV-1 interaction with an O-glycan-specific bacterial lectin enhances virus infectivity and resistance to neutralization by antibodies.

Bacteria dysbiosis has been associated with an increased risk of HIV-1 transmission and acquisition. The prevalent idea is that bacteria dysbiosis compromises mucosal integrity and promotes inflammatory conditions to cause recruitment and activation of immune cells that harbor or are targeted by HIV-1. However, it is also possible that HIV-1 directly binds bacteria or bacterial products to impact virus infectivity and transmissibility. This study evaluated HIV-1 interactions with bacteria through glycan-binding lectins. The Streptococcal Siglec-like lectin SLBR-N, which is part of the fimbriae shrouding the bacteria surface and recognizes α2,3 sialyated O-linked glycans, was noted for its ability to enhance HIV-1 infectivity in the context of cell-free infection and cell-to-cell transfer. Enhancing effects were recapitulated with O-glycan-binding plant lectins, signifying the importance of O-glycans. Conversely, N-glycan-binding bacterial lectins FimH and Msl had no effect. SLBR-N was demonstrated to capture and transfer infectious HIV-1 virions, bind to O-glycans on HIV-1 Env, and increase HIV-1 resistance to broadly neutralizing antibodies targeting different regions of Env. Hence, this study highlights the potential contribution of O-glycans in promoting HIV-1 infection through the exploitation of O-glycan-binding lectins from commensal bacteria at the mucosa.

Emerging issues in probiotic safety: 2023 perspectives.

Probiotics are used for both generally healthy consumers and in clinical settings. However, theoretical and proven adverse events from probiotic consumption exist. New probiotic strains and products, as well as expanding use of probiotics into vulnerable populations, warrants concise, and actionable recommendations on how to work toward their safe and effective use. The International Scientific Association for Probiotics and Prebiotics convened a meeting to discuss and produce evidence-based recommendations on potential acute and long-term risks, risks to vulnerable populations, the importance for probiotic product quality to match the needs of vulnerable populations, and the need for adverse event reporting related to probiotic use. The importance of whole genome sequencing, which enables determination of virulence, toxin, and antibiotic resistance genes, as well as clear assignment of species and strain identity, is emphasized. We present recommendations to guide the scientific and medical community on judging probiotic safety.

What is the context? Probiotics, available to healthy consumers as both dietary supplements and foods, are also used by some patient populations. The goal of this paper is to determine if any new factors have emerged that would impact current views about probiotic safety for both these populations.What is new? The authors conclude that established practices are sensibly addressing factors important to the safety of traditional probiotics used by the general population. They also make recommendations regarding emerging safety considerations. Probiotics targeted for patient populations should undergo stringent testing to meet quality standards appropriate for that population, preferably verified by an independent third party. The safety of probiotics derived from species without a history of safe use must be considered on a case-by-case basis. Research is needed to address some gaps, for example which best animal models to use for safety assessment of live microbes, the possibility of antibiotic resistance gene transfer via transformation, and potential impact of probiotic-induced changes in microbiomes, interactions with drugs, and probiotic colonization.What is the impact? Probiotics of sufficient quality for patient populations are being developed and should be used accordingly. Long-term safety assessments for probiotics should be consistent with, and not more stringent than, current regulatory requirements for biologic drugs, including fecal microbial transplants. Rigor in collecting and reporting data on adverse events is needed. The authors confirm the need for understanding the entire genetic makeup of a probiotic as a cornerstone for assessing its safety.

Epidemiologic Evidence on the Role of Lactobacillus iners in Sexually Transmitted Infections and Bacterial Vaginosis: A Series of Systematic Reviews and Meta-Analyses.

ABSTRACT: Although Lactobacillus crispatus -dominated vaginal microbiotas are thought to protect against bacterial vaginosis (BV) and sexually transmitted infections, the role of Lactobacillus iners -dominated microbiotas is less clear. To better understand the impact of L. iners on common cervicovaginal infections, we conducted systematic reviews of the associations between L. iners compared with L. crispatus and 8 outcomes: Chlamydia trachomatis (Ct), BV, human papillomavirus, cervical dysplasia, human immunodeficiency virus, genital herpes, Trichomonas vaginalis , and Neisseria gonorrhoeae . On April 30, 2021, we searched PubMed, Embase, Cochrane Library, and Web of Science for epidemiologic studies of reproductive-age, nonpregnant, cisgender women that used marker gene sequencing to characterize vaginal microbiota composition and presented an effect estimate for the association between L. iners , compared with L. crispatus , and outcomes of interest. For outcomes with ≥3 eligible results presenting the same form of effect estimate, we conducted random-effects meta-analysis. The review protocol was registered prospectively (PROSPERO CRD42020214775). Six Ct studies were included in meta-analysis, which showed L. iners -dominated microbiotas were associated with 3.4-fold higher odds of Ct compared with L. crispatus -dominated microbiotas (95% confidence interval, 2.1-5.4). Three BV studies were included in meta-analysis, which indicated L. iners -dominated microbiotas were associated with 2.1-fold higher prevalence of BV compared with L. crispatus -dominated microbiotas (95% confidence interval, 0.9-4.9). Evidence was too sparse to perform meta-analysis for the remaining outcomes. L. iners -dominated vaginal microbiotas may be suboptimal compared with L. crispatus -dominated microbiotas for BV and Ct. These reviews highlight evidence gaps regarding the remaining outcomes and opportunities to improve epidemiologic rigor in vaginal microbiome science.

Lacticaseibacillus rhamnosus GR-1, a.k.a. Lactobacillus rhamnosus GR-1: Past and Future Perspectives.

Lacticaseibacillus rhamnosus GR-1 (LGR-1) (previously classified as Lactobacillus rhamnosus GR-1) is the most researched probiotic strain for women's health. Its various urogenital health effects, including a reduction in the recurrence of bacterial vaginosis and urinary-tract infection, are well documented. The strain has also been safely used by HIV-positive subjects, a portion of whom have reported reduced diarrhea and increased CD4 counts. Unlike most probiotic strains used for urogenital health, LGR-1 has been extensively studied for its properties, including its genomic and metabolic traits and its surface properties. This review aims to highlight the totality of research performed with LGR-1, to act as a rigorous scientific benchmark for probiotic microbes, especially for application to women's health.

Shaping the Future of Probiotics and Prebiotics.

Recent and ongoing developments in microbiome science are enabling new frontiers of research for probiotics and prebiotics. Novel types, mechanisms, and applications currently under study have the potential to change scientific understanding as well as nutritional and healthcare applications of these interventions. The expansion of related fields of microbiome-targeted interventions, and an evolving landscape for implementation across regulatory, policy, prescriber, and consumer spheres, portends an era of significant change. In this review we examine recent, emerging, and anticipated trends in probiotic and prebiotic science, and create a vision for broad areas of developing influence in the field.

Inhibition of Candida albicans morphogenesis by chitinase from Lactobacillus rhamnosus GG.

Lactobacilli have been evaluated as probiotics against Candida infections in several clinical trials, but with variable results. Predicting and understanding the clinical efficacy of Lactobacillus strains is hampered by an overall lack of insights into their modes of action. In this study, we aimed to unravel molecular mechanisms underlying the inhibitory effects of lactobacilli on hyphal morphogenesis, which is a crucial step in C. albicans virulence. Based on a screening of different Lactobacillus strains, we found that the closely related taxa L. rhamnosus, L. casei and L. paracasei showed stronger activity against Candida hyphae formation compared to other Lactobacillus species tested. By exploring the activity of purified compounds and mutants of the model strain L. rhamnosus GG, the major peptidoglycan hydrolase Msp1, conserved in the three closely related taxa, was identified as a key effector molecule. We could show that this activity of Msp1 was due to its ability to break down chitin, the main polymer in the hyphal cell wall of C. albicans. This identification of a Lactobacillus-specific protein with chitinase activity having anti-hyphal activity will assist in better strain selection and improved application in future clinical trials for Lactobacillus-based Candida-management strategies.

Probiotics against airway allergy: host factors to consider.

The worldwide prevalence of allergic diseases has drastically increased in the past decades. Recent studies underline the importance of microbial exposure for the development of a balanced immune system. Consequently, probiotic bacteria are emerging as a safe and natural strategy for allergy prevention and treatment. However, clinical probiotic intervention studies have so far yielded conflicting results. There is increasing awareness about the importance of host-associated factors that determine whether an individual will respond to a specific probiotic treatment, and it is therefore crucial to promote a knowledge-based instead of an empirical selection of promising probiotic strains and their administration regimen.In this Review, we summarize the insights from animal model studies of allergic disease, which reveal how host-related factors - such as genetic makeup, sex, age and microbiological status - can impact the outcomes of preventive or curative probiotic treatment. We explore why and how these factors can influence the results of probiotic studies and negatively impact the reproducibility in animal experiments. These same factors might profoundly influence the outcomes of human clinical trials, and can potentially explain the conflicting results from probiotic intervention studies. Therefore, we also link these host-related factors to human probiotic study outcomes in the context of airway allergies.

Engineering Lactobacillus rhamnosus GG and GR-1 to express HIV-inhibiting griffithsin.

Probiotic bacteria are being explored for the in situ delivery of various therapeutic agents. In this study, we aimed to express two HIV-inhibiting lectins, actinohivin (AH) and griffithsin (GRFT), in the probiotic strains Lactobacillus rhamnosus GG and L. rhamnosus GR-1 for gastrointestinal and vaginal mucosal delivery, respectively. Constructs were generated for the intracellular and extracellular production of AH and GRFT under the control of the promoter of their Major Secreted Protein Msp1. Also, intracellular expression of GRFT was investigated under the control of the nisA promoter from the inducible nisin-controlled expression (NICE) system. For the extracellular localization, the signal leader peptide of Msp1/p75 from L. rhamnosus GG was translationally fused with the genes encoding AH and GRFT. Construction of recombinant strains expressing the AH monomer and dimer was unsuccessful, probably due to the intracellular toxicity of AH for the lactobacilli. On the other hand, recombinant strains for intra- and extracellular production of GRFT by L. rhamnosus GG and GR-1 were successfully constructed. The highest expression levels of recombinant GRFT were observed for the constructs under the control of the inducible nisA promoter and we demonstrated anti-HIV activity against an M-tropic and a T-tropic HIV-1 strain. We can conclude that recombinant Lactobacillus expressing anti-HIV lectins could contribute to the development of enhanced probiotic strains that are able to inhibit HIV transmission and subsequent replication, although further research and development are required.

Comparative Genomic and Phenotypic Analysis of the Vaginal Probiotic Lactobacillus rhamnosus GR-1.

Lactobacillus represents a versatile bacterial genus, which can adapt to a wide variety of ecological niches, including human body sites such as the intestinal and urogenital tract. In this study, the complete genome sequence of the vaginal probiotic Lactobacillus rhamnosus GR-1 was determined and compared to other L. rhamnosus strains at genomic and phenotypic level. The strain GR-1 was originally isolated from a female urethra, and was assessed with L. rhamnosus GG from a feces sample of a healthy male, and L. rhamnosus LC705 from a dairy product. A key difference is the absence in GR-1 and LC705 of the spaCBA locus required for pili-mediated intestinal epithelial adhesion. In addition, the L. rhamnosus GR-1 genome contains a unique cluster for exopolysaccharide production, which is postulated to synthesize glucose-rich, rhamnose-lacking exopolysaccharide molecules that are different from the galactose-rich extracellular polysaccharide of L. rhamnosus GG. Compared to L. rhamnosus GG, L. rhamnosus GR-1 was also genetically predicted and experimentally shown to better metabolize lactose and maltose, and to better withstand oxidative stress, which is of relevance in the vagina. This study could thus provide a molecular framework for the selection of the optimal probiotic strain for each targeted niche and condition, but further substantiation of niche adaptation mechanisms of lactobacilli is warranted.

Women and Their Microbes: The Unexpected Friendship.

Communities of microbiota have been associated with numerous health outcomes, and while much emphasis has been placed on the gastrointestinal niche, there is growing interest in the microbiome specific for female reproductive health and the health of their offspring. The vaginal microbiome plays an essential role not only in health and dysbiosis, but also potentially in successful fertilization and healthy pregnancies. In addition, microbial communities have been isolated from formerly forbidden sterile niches such as the placenta, breast, uterus, and Fallopian tubes, strongly suggesting an additional microbial role in women's health. A combination of maternally linked prenatal, birth, and postnatal factors, together with environmental and medical interventions, influence early and later life through the microbiome. Here, we review the role of microbes in female health focusing on the vaginal tract and discuss how male and female reproductive microbiomes are intertwined with conception and how mother-child microbial transfer is a key determinant in infant health, and thus the next generation.

Expression of fluorescent proteins in Lactobacillus rhamnosus to study host-microbe and microbe-microbe interactions.

Probiotic Lactobacillus strains are widely used to benefit human and animal health, although the exact mechanisms behind their interactions with the host and the microbiota are largely unknown. Fluorescent tagging of live probiotic cells is an important tool to unravel their modes of action. In this study, the implementation of different heterologously expressed fluorescent proteins for the labelling of the model probiotic strains Lactobacillus rhamnosusGG (gastrointestinal) and Lactobacillus rhamnosusGR-1 (vaginal) was explored. Heterologous expression of mTagBFP2 and mCherry resulted in long-lasting fluorescence of L. rhamnosusGG and GR-1 cells, using the nisin-controlled expression (NICE) system. These novel fluorescent strains were then used to study in vitro aspects of their microbe-microbe and microbe-host interactions. Lactobacillus rhamnosusGG and L. rhamnosusGR-1 expressing mTagBFP2 and mCherry could be visualized in mixed-species biofilms, where they inhibited biofilm formation by Salmonella Typhimurium-gfpmut3 expressing the green fluorescent protein. Likewise, fluorescent L. rhamnosusGG and L. rhamnosusGR-1 were implemented for the visualization of their adhesion patterns to intestinal epithelial cell cultures. The fluorescent L. rhamnosus strains developed in this study can therefore serve as novel tools for the study of probiotic interactions with their environment.

Lactobacillus iners: Friend or Foe?

The vaginal microbial community is typically characterized by abundant lactobacilli. Lactobacillus iners, a fairly recently detected species, is frequently present in the vaginal niche. However, the role of this species in vaginal health is unclear, since it can be detected in normal conditions as well as during vaginal dysbiosis, such as bacterial vaginosis, a condition characterized by an abnormal increase in bacterial diversity and lack of typical lactobacilli. Compared to other Lactobacillus species, L. iners has more complex nutritional requirements and a Gram-variable morphology. L. iners has an unusually small genome (ca. 1 Mbp), indicative of a symbiotic or parasitic lifestyle, in contrast to other lactobacilli that show niche flexibility and genomes of up to 3-4 Mbp. The presence of specific L. iners genes, such as those encoding iron-sulfur proteins and unique σ-factors, reflects a high degree of niche specification. The genome of L. iners strains also encodes inerolysin, a pore-forming toxin related to vaginolysin of Gardnerella vaginalis. Possibly, this organism may have clonal variants that in some cases promote a healthy vagina, and in other cases are associated with dysbiosis and disease. Future research should examine this friend or foe relationship with the host.

The lectin-like protein 1 in Lactobacillus rhamnosus GR-1 mediates tissue-specific adherence to vaginal epithelium and inhibits urogenital pathogens.

The probiotic Lactobacillus rhamnosus GR-1 has been documented to survive implantation onto the vaginal epithelium and interfere with urogenital pathogens. However, the molecular mechanisms involved are largely unknown. Here, we report for the first time the construction of dedicated knock-out mutants in L. rhamnosus GR-1 to enable the study of gene functions. In a search for genes responsible for the adherence capacity of L. rhamnosus GR-1, a genomic region encoding a protein with homology to lectin-like proteins was identified. Phenotypic analyses of the knock-out mutant of L. rhamnosus GR-1 revealed a two-fold decreased adhesion to the vaginal and ectocervical epithelial cell lines compared to wild-type. In contrast, the adhesion to gastro-intestinal epithelial (Caco2) and endocervical cell lines (Hela and End1/E6E7) was not drastically affected by the mutation, suggesting that the LGR-1_Llp1 lectins mediates tissue tropism. The purified LGR-1_Llp1 protein also inhibited biofilm formation and adhesion of uropathogenic Escherichia coli. For the first time, an important role for a novel lectin-like protein in the adhesion capacity and host cell-specific interaction of a vaginal probiotic Lactobacillus strain has been discovered, with an additional role in pathogen inhibition.

High mannose-specific lectin Msl mediates key interactions of the vaginal Lactobacillus plantarum isolate CMPG5300.

To characterize the interaction potential of the human vaginal isolate Lactobacillus plantarum CMPG5300, its genome was mined for genes encoding lectin-like proteins. cmpg5300.05_29 was identified as the gene encoding a putative mannose-binding lectin. Phenotypic analysis of a gene knock-out mutant of cmpg5300.05_29 showed that expression of this gene is important for auto-aggregation, adhesion to the vaginal epithelial cells, biofilm formation and binding to mannosylated glycans. Purification of the predicted lectin domain of Cmpg5300.05_29 and characterization of its sugar binding capacity confirmed the specificity of the lectin for high- mannose glycans. Therefore, we renamed Cmpg5300.05_29 as a mannose-specific lectin (Msl). The purified lectin domain of Msl could efficiently bind to HIV-1 glycoprotein gp120 and Candida albicans, and showed an inhibitory activity against biofilm formation of uropathogenic Escherichia coli, Staphylococcus aureus and Salmonella Typhimurium. Thus, using a combination of molecular lectin characterization and functional assays, we could show that lectin-sugar interactions play a key role in host and pathogen interactions of a prototype isolate of the vaginal Lactobacillus microbiota.

Lectin-Like Molecules of Lactobacillus rhamnosus GG Inhibit Pathogenic Escherichia coli and Salmonella Biofilm Formation.

OBJECTIVES: Increased antibiotic resistance has catalyzed the research on new antibacterial molecules and alternative strategies, such as the application of beneficial bacteria. Since lectin molecules have unique sugar-recognizing capacities, and pathogens are often decorated with sugars that affect their survival and infectivity, we explored whether lectins from the probiotic strain Lactobacillus rhamnosus GG have antipathogenic properties. METHODS: The genome sequence of L. rhamnosus GG was screened for the presence of lectin-like proteins. Two genes, LGG_RS02780 and LGG_RS02750, encoding for polypeptides with an N-terminal conserved L-type lectin domain were detected and designated Llp1 (lectin-like protein 1) and Llp2. The capacity of Llp1 and Llp2 to inhibit biofilm formation of various pathogens was investigated. Sugar specificity was determined by Sepharose beads assays and glycan array screening. RESULTS: The isolated lectin domains of Llp1 and Llp2 possess pronounced inhibitory activity against biofilm formation by various pathogens, including clinical Salmonella species and uropathogenic E. coli, with Llp2 being more active than Llp1. In addition, sugar binding assays with Llp1 and Llp2 indicate specificity for complex glycans. Both proteins are also involved in the adhesion capacity of L. rhamnosus GG to gastrointestinal and vaginal epithelial cells. CONCLUSIONS: Lectins isolated from or expressed by beneficial lactobacilli could be considered promising bio-active ingredients for improved prophylaxis of urogenital and gastrointestinal infections.

The Low-Cost Compound Lignosulfonic Acid (LA) Exhibits Broad-Spectrum Anti-HIV and Anti-HSV Activity and Has Potential for Microbicidal Applications.

OBJECTIVES: Lignosulfonic acid (LA), a low-cost lignin-derived polyanionic macromolecule, was extensively studied for its anti-HIV and anti-HSV activity in various cellular assays, its mechanism of viral inhibition and safety profile as potential microbicide. RESULTS: LA demonstrated potent inhibitory activity of HIV replication against a wide range of R5 and X4 HIV strains and prevented the uptake of HIV by bystander CD4+ T cells from persistently infected T cells in vitro (IC50: 0.07 - 0.34 µM). LA also inhibited HSV-2 replication in vitro in different cell types (IC50: 0.42 - 1.1 µM) and in rodents in vivo. Furthermore, LA neutralized the HIV-1 and HSV-2 DC-SIGN-mediated viral transfer to CD4+ T cells (IC50: ~1 µM). In addition, dual HIV-1/HSV-2 infection in T cells was potently blocked by LA (IC50: 0.71 µM). No antiviral activity was observed against the non-enveloped viruses Coxsackie type B4 and Reovirus type 1. LA is defined as a HIV entry inhibitor since it interfered with gp120 binding to the cell surface of T cells. Pretreatment of PBMCs with LA neither increased expression levels of cellular activation markers (CD69, CD25 and HLA-DR), nor enhanced HIV-1 replication. Furthermore, we found that LA had non-antagonistic effects with acyclovir, PRO2000 or LabyA1 (combination index (CI): 0.46 - 1.03) in its anti-HSV-2 activity and synergized with tenofovir (CI: 0.59) in its anti-HIV-1 activity. To identify mechanisms of LA resistance, we generated in vitro a mutant HIV-1 NL4.3LAresistant virus, which acquired seven mutations in the HIV-1 envelope glycoproteins: S160N, V170N, Q280H and R389T in gp120 and K77Q, N113D and H132Y in gp41. Additionally, HIV-1 NL4.3LAresistant virus showed cross-resistance with feglymycin, enfuvirtide, PRO2000 and mAb b12, four well-described HIV binding/fusion inhibitors. Importantly, LA did not affect the growth of vaginal Lactobacilli strains. CONCLUSION: Overall, these data highlight LA as a potential and unique low-cost microbicide displaying broad anti-HIV and anti-HSV activity.

Lactobacillus species as biomarkers and agents that can promote various aspects of vaginal health.

The human body is colonized by a vast number of microorganisms collectively referred to as the human microbiota. One of the main microbiota body sites is the female genital tract, commonly dominated by Lactobacillus spp., in approximately 70% of women. Each individual species can constitute approximately 99% of the ribotypes observed in any individual woman. The most frequently isolated species are Lactobacillus crispatus, Lactobacillus gasseri, Lactobacillus jensenii and Lactobacillus iners. Residing at the port of entry of bacterial and viral pathogens, the vaginal Lactobacillus species can create a barrier against pathogen invasion since mainly products of their metabolism secreted in the cervicovaginal fluid can play an important role in the inhibition of bacterial and viral infections. Therefore, a Lactobacillus-dominated microbiota appears to be a good biomarker for a healthy vaginal ecosystem. This balance can be rapidly altered during processes such as menstruation, sexual activity, pregnancy and various infections. An abnormal vaginal microbiota is characterized by an increased diversity of microbial species, leading to a condition known as bacterial vaginosis. Information on the vaginal microbiota can be gathered from the analysis of cervicovaginal fluid, by using the Nugent scoring or the Amsel's criteria, or at the molecular level by investigating the number and type of Lactobacillus species. However, when translating this to the clinical setting, it should be noted that the absence of a Lactobacillus-dominated microbiota does not appear to directly imply a diseased condition or dysbiosis. Nevertheless, the widely documented beneficial role of vaginal Lactobacillus species demonstrates the potential of data on the composition and activity of lactobacilli as biomarkers for vaginal health. The substantiation and further validation of such biomarkers will allow the design of better targeted probiotic strategies.

The lantibiotic peptide labyrinthopeptin A1 demonstrates broad anti-HIV and anti-HSV activity with potential for microbicidal applications.

Lantibiotics are peptides, produced by bacteria, that contain the noncanonical amino acid lanthionine and many of them exhibit antibacterial activities. The labyrinthopeptin A1 (LabyA1) is a prototype peptide of a novel class of carbacyclic lantibiotics. Here, we extensively evaluated its broad-spectrum activity against HIV and HSV in vitro, studied its mechanism of action and evaluated potential microbicidal applications. LabyA1 exhibited a consistent and broad anti-HIV activity (EC50s: 0.70-3.3 µM) and anti-HSV activity (EC50s: 0.29-2.8 µM) in cell cultures. LabyA1 also inhibited viral cell-cell transmission between persistently HIV-infected T cells and uninfected CD4(+) T cells (EC50∶2.5 µM) and inhibited the transmission of HIV captured by DC-SIGN(+)-cells to uninfected CD4(+) T cells (EC50∶4.1 µM). Time-of-drug addition studies revealed that LabyA1 acts as an entry inhibitor against HIV and HSV. Cellular and virus binding studies combined with SPR/FLIPR technology showed that LabyA1 interacted with the HIV envelope protein gp120, but not with the HIV cellular receptors. LabyA1 also demonstrated additive to synergistic effects in its anti-HIV-1 and anti-HSV-2 activity with anti(retro)viral drugs in dual combinations such as tenofovir, acyclovir, saquinavir, raltegravir and enfuvirtide. LabyA1 can be considered as a novel lead peptide as it had profound antiviral activity against HIV and HSV. Pre-treatment of PBMCs with LabyA1 neither increased the expression of the activation markers CD69 and CD25, nor enhanced HIV replication, nor significantly induced various inflammatory cytokines/chemokines. LabyA1 also did not affect the growth of vaginal Lactobacilli populations. Based on the lack of toxicity on the vaginal Lactobacillus strains and its synergistic/additive profile in combination with clinically approved anti(retro)virals, it deserves further attention as a potential microbicide candidate in the prevention of sexual transmitted diseases.

Vaginal microbiota and its role in HIV transmission and infection.

The urogenital tract appears to be the only niche of the human body that shows clear differences in microbiota between men and women. The female reproductive tract has special features in terms of immunological organization, an epithelial barrier, microbiota, and influence by sex hormones such as estrogen. While the upper genital tract is regarded as free of microorganisms, the vagina is colonized by bacteria dominated by Lactobacillus species, although their numbers vary considerably during life. Bacterial vaginosis is a common pathology characterized by dysbiosis, which increases the susceptibility for HIV infection and transmission. On the other hand, HIV infections are often characterized by a disturbed vaginal microbiota. The endogenous vaginal microbiota may protect against HIV by direct production of antiviral compounds, through blocking of adhesion and transmission by ligands such as lectins, and/or by stimulation of immune responses. The potential role of probiotics in the prevention of HIV infections and associated symptoms, by introducing them to the vaginal and gastrointestinal tract (GIT), is also discussed. Of note, the GIT is a site of considerable HIV replication and CD4(+) T-cell destruction, resulting in both local and systemic inflammation. Finally, genetically engineered lactobacilli show promise as new microbicidal agents against HIV.

Inhibition of infection and transmission of HIV-1 and lack of significant impact on the vaginal commensal lactobacilli by carbohydrate-binding agents.

OBJECTIVES: A selection of carbohydrate-binding agents (CBAs) with different glycan specificities were evaluated for their inhibitory effect against HIV infection and transmission, and their interaction with vaginal commensal bacteria. METHODS: Several assays were used for the antiviral evaluation: (i) cell-free virus infection of human CD4+ T lymphocyte C8166 cells; (ii) syncytium formation in co-cultures of persistently HIV-1-infected HUT-78/HIV-1 and non-infected CD4+ SupT1 cells; (iii) DC-SIGN-directed capture of HIV-1 particles; and (iv) transmission of DC-SIGN-captured HIV-1 particles to uninfected CD4+ C8166 cells. CBAs were also examined for their interaction with vaginal commensal lactobacilli using several viability, proliferation and adhesion assays. RESULTS: The CBAs showed efficient inhibitory activity in the nanomolar to low-micromolar range against four events that play a crucial role in HIV-1 infection and transmission: cell-free virus infection, fusion between HIV-1-infected and non-infected cells, HIV-1 capture by DC-SIGN and transmission of DC-SIGN-captured virus to T cells. As candidate microbicides should not interfere with the normal human microbiota, we examined the effect of CBAs against Lactobacillus strains, including a variety of vaginal strains, a gastrointestinal strain and several non-human isolates. None of the CBAs included in our studies inhibited the growth of these bacteria in several media, affected their viability or had any significant impact on their adhesion to HeLa cell monolayers. CONCLUSIONS: The CBAs in this study were inhibitory to HIV-1 in several in vitro infection and transmission models, and may therefore qualify as potential microbicide candidates. The lack of significant impact on commensal vaginal lactobacilli is an important property of these CBAs in view of their potential microbicidal use.