Bacteria associated with BV increase genital-tract HIV RNA levels. Quantitative bacterial counts for lactobacilli and M. hominis are better correlates of CVL HIV RNA than are Nugent score or Amsel criteria. Since plasma virus and CD4 cell levels did not differ between the BV and no-BV groups, these data suggest that the bacterial flora associated with BV influence genital-tract HIV shedding.

Lactobacillus colonization of the lower female genital tract provides protection from the acquisition of sexually transmitted diseases, including human immunodeficiency virus, and from adverse pregnancy outcomes. While glycogen in vaginal epithelium is thought to support Lactobacillus colonization in vivo, many Lactobacillus isolates cannot utilize glycogen in vitro. This study investigated how glycogen could be utilized by vaginal lactobacilli in the genital tract. Several Lactobacillus isolates were confirmed to not grow in glycogen, but did grow in glycogen-breakdown products, including maltose, maltotriose, maltopentaose, maltodextrins, and glycogen treated with salivary α-amylase. A temperature-dependent glycogen-degrading activity was detected in genital fluids that correlated with levels of α-amylase. Treatment of glycogen with genital fluids resulted in production of maltose, maltotriose, and maltotetraose, the major products of α-amylase digestion. These studies show that human α-amylase is present in the female lower genital tract and elucidates how epithelial glycogen can support Lactobacillus colonization in the genital tract.

Problem Short chain fatty acids (SCFAs), produced at relatively high levels by anaerobic bacteria in bacterial vaginosis (BV), are believed to be anti-inflammatory. BV, a common alteration of the genital microbiota associated with increased susceptibility to HIV infection, is characterized by increased levels of both pro-inflammatory cytokines and SCFAs. We investigated how SCFAs alone or together with TLR-ligands affected pro-inflammatory cytokine secretion. Method of study Cytokines were measured by ELISA. Flow was used for phenotyping and reactive oxygen species (ROS) measurement. Results SCFAs, at 20mM, induced IL-8, IL-6, and IL-1β release while lower levels (0.02–2mM) did not induce cytokine secretion. Levels >20mM were toxic to cells. Interestingly, lower levels of SCFAs significantly enhanced TLR2 ligand- and TLR7 ligand-induced production of IL-8 and TNFα in a time- and dose-dependent manner, but had little effect on LPS-induced cytokine release. SCFAs mediated their effects on pro-inflammatory cytokine production at least in part by inducing generation of reactive oxygen species. Conclusions Our data suggest that SCFAs, especially when combined with specific TLR ligands, contribute to a pro-inflammatory milieu in the lower genital tract and help further our understanding of how BV affects susceptibility to microbial infections.

The innate and adaptive immune systems are important mechanisms for resistance to pathogens in the female lower genital tract. Lactobacilli at this site help maintain a healthy vagina by producing several factors including lactic acid. Indeed, bacterial vaginosis, a condition in which the genital microbiota is altered, is strongly associated with increased rates of a number of infections including HIV. However, the precise factors that contribute to increased rates of microbial and viral infections in bacterial vaginosis remain to be elucidated. We have studied the effects of bacterial microbiota in the lower genital tract on innate immunity and have found that Toll-like receptor ligands and short chain fatty acids, produced by bacterial microbiota, have dramatic effects on immune function. In this review, we will discuss these results, in addition to some recent articles that we believe will enhance our understanding of how microbes might interact with the immune system.

Background This study investigated whether HIV-infection is associated with a change in diversity of genital microbiota in women. Methods Amplicon length heterogeneity PCR (LH-PCR) and pyrosequencing of the 16S rRNA gene were used to analyze diversity of the microbiota from HIV-positive (HIV+) and HIV-negative (HIV-) women with or without bacterial vaginosis (BV). Results LH-PCR analysis showed significantly more diversity in BV-positive (BV+) women than in BV-negative (BV-) women, but no significant difference between HIV+ women and HIV- women. Pyrosequencing revealed that Lactobacillus constituted a median of 96% of the bacteria in BV- women. BV+ women had a significantly higher number of taxa found at ≥ 1% of the microbiota (median of 11). Common taxa in BV were Prevotella, Megasphaera, Gardnerella, Coriobacterineae, Lachnospira, and Sneathia. There was a trend (p=0.07) toward a higher number of taxa in HIV+BV+ compared to HIV-BV+ women. Propionibacterineae, Citrobacter and Anaerococcus were found only in HIV+ women (p<0.05). Conclusions This study showed that both LH-PCR and pyrosequencing differentiated BV+ from BV- microbiota and that pyrosequencing indicated a trend toward increased diversity in BV+HIV+ suggesting that HIV-infection is associated with changes in diversity of genital microbiota.