The Effect of Hormonal Contraception on Mucosal and Peripheral Immunity: Implications for Hiv Susceptibility Among Women in Nairobi, Kenya

Abstract

Background Safe and effective contraception is a critical component of basic healthcare for women. Unfortunately, a number of observational studies have associated depot-medroxyprogesterone acetate (DMPA) - a low-cost, progestin-based contraceptive - with a higher risk of HIV-1 acquisition. DMPA is the most widely used reversible contraceptive among young women living in sub-Saharan Africa (SSA), a region that bears the highest burden of HIV worldwide. An association between DMPA use and HIV acquisition in this region is of public health concern and presents potential challenges to HIV control efforts on the African continent. It is imperative to assess the biological mechanisms that DMPA may exploit to influence HIV acquisition at the genital tract including elevated numbers of CD4+ HIV target cells and increased concentrations of inflammatory cytokines at the endocervical mucosa. Alteration of the bloodstream levels of immune-modulating hormones may also be another mechanism. Defining the impact of DMPA on the immune response is important in understanding the biological factors influencing the risk of HIV acquisition in women, especially sex workers who are already at increased risk compared to women from the general population. Therefore, the aim of this study was to characterize the effect of DMPA on mucosal and peripheral immune responses of sex worker and non-sex worker groups of women. Objective To compare levels of T cell activation, concentrations of proinflammatory cytokines/chemokines in blood and the genital mucosa, and plasma levels of cortisol, free triiodothyronine (T3), and free thyroxine (T4) of female sex workers (FSW) and non-sex workers (non-SW) using DMPA and those not using any hormonal contraceptive. Methods In this cross-sectional study, 66 FSW and 61 non-SW living in the same community were recruited. Venous blood was collected and peripheral blood mononuclear cells (PBMC) and plasma freshly isolated using the Ficoll-Hypaque technique. Cervical mononuclear cells (CMC) were extracted from cytobrush specimens and processed. Cervicovaginal lavages (CVL) were also obtained. For each participant, paired PBMCs-CMC specimens were stained for ex vivo immunophenotyping with a panel of fluorochrome-conjugated monoclonal antibodies including CD3, CD4, CD8, HLA-DR, CD38, CD69, CCR5, CCR6 and CD161 and Brilliant Violet Stain Buffer. Data were acquired on the LSRII flow cytometer and analysed using FlowJo Software. Cytokine, chemokine and hormone concentrations were determined using multiplex bead arrays. Analyses were performed using GraphPad Prism and R with statistical significance set at p≤0.05. Findings A differential impact of DMPA on the immune response was noted between FSW and non-SW. In non-SW, DMPA elevated genital and peripheral T cell activation and CCR5 expression; they had significantly increased numbers of CD4+CD38+ and CD4+HLADR+ T cells along with increased intensity of CCR5 on CD4+ T cells. Similarly, the proportions of endocervical CD3+ cells, and activated CD4+CD69+ and CD4+38+ T cells were significantly higher in DMPA users. DMPA using non-sex workers also had higher systemic expression of IFNγ, IL-10, MIG and sCD40L. On the other hand, FSW using no HC had lower T cell activation levels and CCR5 expression compared to non-sex workers. In the systemic compartment, FSWs had significantly lower proportion of CD4+CCR5+ cells and expression of CD69+ and CD38+ on CD4+ T cells, while in the genital tract, lower proportion of CD4+CCR5+ cells and expression of the activation markers CD38 and CD69 was observed. Lower systemic concentrations of proinflammatory cytokines (IL-17, TNFα) and of chemotactic proteins (MCP-1) in the plasma as well as lower level of IFNγ in CVL of FSWs on no HC was also observed. But remarkably, similar levels of immune activation and inflammation was observed between FSW and non-SW using DMPA. By multivariate analysis, plasma MIG was the best marker for differentiating DMPA users from no-HC users. Additionally, Cortisol, T3 and T4 levels were elevated in DMPA users and this correlated with markers of T cell activation. Conclusion: DMPA raised genital and peripheral immune activation, CCR5 expression, cortisol, and thyroid hormone levels. While sex workers had decreased levels of immune activation at the genital tract, DMPA counteracted this effect. These findings collectively demonstrate that DMPA alters the immune response and provide a biological mechanism underlying increased susceptibility to HIV in women using DMPA. Therefore, women using DMPA should be counseled to evaluate their individual HIV risk and use appropriate HIV prevention methods alongside the contraceptive.