The cervicovaginal mucus barrier to HIV-1 is diminished in bacterial vaginosis

Abstract

Bacterial vaginosis (BV), a condition in which the vaginal microbiota consists of community of obligate and facultative anaerobes rather than dominated by a single species of Lactobacillus, affects ~30% of women in the US. Women with BV are at 60% increased risk for HIV acquisition and are 3-times more likely to transmit HIV to an uninfected partner. As cervicovaginal mucus (CVM) is the first line of defense against mucosal pathogens and the home of the resident vaginal microbiota, we hypothesized the barrier function of CVM to HIV may be diminished in BV. Here, we characterized CVM properties including pH, lactic acid content, and Nugent score to correlate with the microbiota community composition, which was confirmed by 16S rDNA sequencing on a subset of samples. We then quantified the mobility of fluorescently-labeled HIV virions and nanoparticles to characterize the structural and adhesive barrier properties of CVM. Our analyses included women with Nugent scores categorized as intermediate (4-6) and BV (7-10), women that were either symptomatic or asymptomatic, and a small group of women before and after antibiotic treatment for symptomatic BV. Overall, we found that HIV virions had significantly increased mobility in CVM from women with BV compared to CVM from women with Lactobacillus crispatus-dominant microbiota, regardless of whether symptoms were present. We confirmed using nanoparticles and scanning electron microscopy that the impaired barrier function was due to reduced adhesive barrier properties without an obvious degradation of the physical CVM pore structure. We further confirmed a similar increase in HIV mobility in CVM from women with Lactobacillus iners-dominant microbiota, the species most associated with transitions to BV and that persists after antibiotic treatment for BV. Our findings advance the understanding of the protective role of mucus and highlight the interplay between vaginal microbiota and the innate barrier function mucus.

Fig 1. Stacked bar graph of bacterial phylotypes as determined by 16S rDNA sequencing.

Samples are organized according to community state types (CST) as indicated by the colored bar on top of the graph (left to right: red = L. jensenii; orange = L. crispatus; blue = mixture of L. iners and L. crispatus; green = L. iners; maroon = polymicrobial). Each column represents an individual sample (n = 38 total). Bacterial phylotypes are indicated by different colors displayed in the legend on the right.

Fig 2. HIV virion ensemble-averaged mean square displacement at a time scale (τ) of 1 s, where each data marker represents an individual CVM sample (n = 84 CVM samples from 70 participants).

Samples are organized by group assignments and color coded based on available 16S sequencing community state types. Data represented as geometric mean and geometric mean standard deviation. **** p < 0.0001. Repeat samples from the same participant were excluded in statistical analyses.

Fig 3

Ensemble-averaged mean square displacement () as a function of time scale (τ) for (A) 100 nm, (B) 200 nm, (C) 500 nm, and (D) 1 μm sized PS and PS-PEG particles in Group 1 (n = 6) and Group 4 (n = 8) CVM samples. Data represented as the average ± SEM.

Fig 4

Representative scanning electron microscopy (SEM) images of (A) Group 1 and (B) Group 4 CVM samples. Scale bar = 1 μm.

Fig 5

(A) HIV virion ensemble-averaged mean square displacement at a time scale (τ) of 1 s in CVM from participants with symptomatic BV (n = 7) compared to asymptomatic BV (n = 7). Data is redundant from selected samples also shown in Fig 2. Samples are color-coded based on available 16S sequencing community state types. Data represented as geometric mean and geometric mean standard deviation. (B) Ensemble-averaged mean square displacement <MSD> as a function of τ for 100 nm PS and PS-PEG particles in CVM samples from participants with symptomatic BV (n = 4) compared to asymptomatic BV (n = 4). Data is redundant from selected samples also shown in Fig 3. Data represented as average ± SEM.

Fig 6

HIV virion ensemble-averaged mean square displacement at a time scale (τ) of 1 s in CVM plotted as a function of (A) pH (n = 84 CVM samples) (B) D-LA (n = 79 CVM samples) and (C) total lactic acid (n = 79 CVM samples). The shape of the data marker reflects the group assignment and the color reflects community state types based on available 16S sequencing data. Pearson correlation coefficient (r) value shown on graph. All p values were p<0.0001.