Higher mucosal antibody concentrations in women with genital tract inflammation

Abstract

Inflammatory cytokines augment humoral responses by stimulating antibody production and inducing class-switching. In women, genital inflammation (GI) significantly modifies HIV risk. However, the impact of GI on mucosal antibodies remains undefined. We investigated the impact of GI, pre-HIV infection, on antibody isotypes and IgG subclasses in the female genital tract. Immunoglobulin (Ig) isotypes, IgG subclasses and 48 cytokines were measured prior to HIV infection in cervicovaginal lavages (CVL) from 66 HIV seroconverters (cases) and 66 matched HIV-uninfected women (controls) enrolled in the CAPRISA 004 and 008 1% tenofovir gel trials. Pre-HIV infection, cases had significantly higher genital IgM (4.13; IQR, 4.04-4.19) compared to controls (4.06; IQR, 3.90-4.20; p = 0.042). More than one-quarter of cases (27%) had GI compared to just over one-tenth (12%) in controls. Significantly higher IgG1, IgG3, IgG4 and IgM (all p < 0.05) were found in women stratified for GI compared to women without. Adjusted linear mixed models showed several pro-inflammatory, chemotactic, growth factors, and adaptive cytokines significantly correlated with higher titers of IgM, IgA and IgG subclasses (p < 0.05). The strong and significant positive correlations between mucosal antibodies and markers of GI suggest that GI may impact mucosal antibody profiles. These findings require further investigation to establish a plausible biological link between the local inflammatory milieu and its consequence on these genital antibodies.

Figure 1

Comparison of mucosal immunoglobulin IgG subclasses and isotypes (Log₁₀ ng/ml) between matched controls and cases pre-HIV infection. Each data point represents an individual sample. Cases represent women who subsequently became HIV-infected, and controls represent women who remained HIV-uninfected. The scatter dot plot includes the medians and interquartile ranges. Wilcoxon signed rank test and paired t-tests were used to compare between the case-matched-control groups and p < 0.05 were considered statistically significant.

Figure 2

Comparison of mucosal IgG subclasses and isotypes in women stratified for presence of genital inflammation (GI+) or absence of genital inflammation (GI−) within cases [GI+ (n = 18) and GI− (n = 48)] and controls [GI+ (n = 8) and GI− (n = 58)] pre-HIV infection. Each data point represents an individual sample, the line-bars represents medians and interquartile ranges. Mann–Whitney U test and unpaired t-tests were used to compare between groups and p < 0.05 were considered statistically significant. Black circle represents cases and black triangle represents controls.

Figure 3

Associations between genital cytokines and mucosal IgG1 (A), IgG2 (B), IgG3 (C), IgG4 (D), IgM (E) and IgA (F). β-coefficients and p-values were determined using multivariable linear mixed models with a random effect of the matched pairs (N = 132). The multivariable models were adjusted for age, HSV-2 status, the number of vaginal sex acts, contraceptive method, condom use, tenofovir use and HIV infection status. β-coefficients are indicated by shaded circles and error bars indicate 95% confidence intervals. P-values < 0.05 are represented by *, and those p-values that are significant after multiple comparisons adjustment are represented by #.

Figure 3

Associations between genital cytokines and mucosal IgG1 (A), IgG2 (B), IgG3 (C), IgG4 (D), IgM (E) and IgA (F). β-coefficients and p-values were determined using multivariable linear mixed models with a random effect of the matched pairs (N = 132). The multivariable models were adjusted for age, HSV-2 status, the number of vaginal sex acts, contraceptive method, condom use, tenofovir use and HIV infection status. β-coefficients are indicated by shaded circles and error bars indicate 95% confidence intervals. P-values < 0.05 are represented by *, and those p-values that are significant after multiple comparisons adjustment are represented by #.