CHAPTER 1: Introduction
1.3 Study Aims and Objectives
The overall aims of this dissertation were to investigate: (i) the biological effect of injectable HCs use on the innate environment in the genital tract of HIV-1 negative women at high risk of HIV-1 infection; and (ii) the impact of injectable HC use on the genital immune environment and epithelial barrier function of HIV-1 infected women and the consequence of these immune changes to their infectiousness to their sexual partners during acute HIV-1 infection.
Rationale
Several HC methods are widely used by South African women to prevent unplanned or mistimed pregnancies, with over 57% of women (aged 15 - 49 years) using long- acting injectable progestin HCs, particularly DMPA (South African Department of Health, 2003). Although the use of DMPA to prevent unplanned pregnancies has explicit gains (WHO, 2010), it has also be associated with an increased risk of HIV-1 infection (Baeten et al. 2007; Martin et al. 1998; Morrison et al. 2010, 2011 and
2012). The precise mechanism by which DMPA may increase risk to HIV-1 infection has not been conclusively demonstrated yet although several studies have suggested that DMPA may reduce integrity and thickness of vaginal and epithelial lining, increase recruitment of HIV-1 target cells to the genital mucosa, and change the vaginal microbiota which may influence HIV-1 risk (Chandra et al. 2013; Ildgruben et al. 2003; Miller et al. 2000; Wieser et al. 2001; Wira et al. 2011). This dissertation focuses on the influence of injectable HC use (DMPA and NET-EN) on risk for HIV- 1 infection in the context of a heterosexual epidemic in South Africa; and the potentially confounding effect of injectable HC use in HIV-1 prevention research. If biological plausibility is demonstrable, more informed policy measures could be implemented timeously to avoid these negative consequences.
Specific Objectives 1
To compare concentrations of genital tract soluble immune mediators [including cytokines, chemokines, growth factors, matrix metalloproteinases (MMPs) and tissue- inhibitors of metalloproteinases (TIMPs)] between women using long-acting injectable HCs and women not using HCs, while accounting for BV and common STIs (Chapter 3).
Rationale.
DMPA might increase HIV-1 aquisition risk by changing the inflammatory or chemotactic environment of the genital mucosa so as to influence the recruitment of HIV-1 susceptible immune cells to the mucosa (Ildgruben et al., 2003; Miller et al.,
2000; Wieser et al., 2001; Wira et al., 2011b; Wira and Veronese, 2011). However, in vitro treatment of PBMCs with injectable HC was shown to cause reduced production of several inflammatory and adaptive cytokines (Huijbregts et al., 2013). Defining the impact of injectable HCs on female genital tract innate immunity in relation to susceptibility to STIs or BV will provide important insights into biological co-factors influencing HIV-1 risk in women.
Hypothesis.
Injectable HC use is associated with reduced cytokine and soluble factor concentrations in genital secretions compared to non-HC users.
Specific Objective 2
To investigate whether detection of semen in cervicovaginal lavages (CVLs) from high-risk HIV-1 negative women, by assessment of Y-chromosome by PCR and prostate specific antigen (PSA) by ELISA, influenced the cytokine milieu and soluble factors of cervicovaginal secretions (Chapter 4).
Rationale.
The vaginal mucosa immune environment plays a potentially important role in regulating the transmission of STIs, including HIV-1 (Chormont et al., 2001). Genital specimens, including CVLs, vaginal and/or cervical swabs, from women have been used to study vaginal mucosa immunity in a number of studies (Bebell et al., 2008;
Belec et al., 1995; Roberts et al., 2012). However, immunological characterization of factors in these genital fluids from sexually active women may be biased by the presence of semen (Silverman et al., 1980). Semen contains high concentrations of both inflammatory and anti-inflammatory cytokines and prostaglandins, which may moderate the cytokine environment in the female genital tract (Olivier et al., 2014).
Detection of PSA and the Y-chromosome are semen markers that have been used as surrogate indicators for the presence of semen in female genital fluids (Chormont et al., 2001). Detecting the presence of semen in genital fluids using these biomarkers provides a tool to objectively assess recent exposure to semen, allowing for objective assessment of unprotected sexual intercourse in HIV-1 prevention trials. In addition, detecting semen also allows evaluation of the confounding effects of semen exposure on the immunological environment in the female genital tract.
Hypothesis.
Presence of semen in cervico-vaginal specimens from sexually active women will influence cytokine concentrations in cervicovaginal fluids.
Specific Objectives 3
To compare the impact of DMPA on innate cell function in vitro, to natural progesterone and cortisol following exogenous addition (Chapter 5).
Rationale.
In vitro study has shown that addition of exogenous progesterone-derivates such as DMPA decreased TLR-9-induced IFN-α production by plasmacytoid dendritic cells (Hughes et al., 2008). Studies elucidating the basic mechanism/s by which injectable HCs might increase HIV-1 infection could aid the WHO consultants to reach a definitive conclusion on guideline for Medical eligebility criteria for contraceptive use, particuraly DMPA.
Hypothesis.
In vitro exogenous addition of HCs to PBMCs from women not using injectable HCs will influence the activation phenotype and suppress cytokine production by monocytes and dendritic cells following TLR stimulation.
Specific Objectives 4
To investigate the influence of DMPA on vaginal epithelial thinning and density of HIV-1 target cells in vaginal biopsies from HIV-1 infected women during acute infection; and implications to their infectiousness to their sexual partners (Chapter 6).
Rationale.
DMPA use has been suggested to increase the likelihood of an HIV-1 infected woman infecting her sex partner. The mechanism/s accounting for increased HIV-1 transmission risk in HIV-1 infected women using DMPA remain poorly
characterized. HIV-1 target cell density in the genital mucosa and inflammatory cytokines present in genital secretions has been suggested to influence HIV-1 risk (Li et al., 2009; Masson et al., 2015). HIV-uninfected women with genital inflammation were at 2.9-fold increased risk for HIV-1 infection (Masson et al., 2015). In addition, women who seroconverted had similar levels of genital tract inflammation before they became infected as they had during acute HIV-1 infection (Roberts et al., 2012).
Better understanding of the influence of DMPA on recruitment of HIV-1 target cells to the female genital tract, properties of the epithelial barrier that could influence HIV-1 penetration, altered genital cytokine profiles and HIV-1 shedding in vaginal secretions could lead to interventions to disrupt HIV-1 transmission.
Hypothesis.
DMPA use will reduce the thickness of the vaginal epithelial barrier in women, reduce the distance between HIV-1 target cell numbers and the vaginal lumen, reduce pro-inflammatory cytokine concentrations in CVLs, and increase HIV-1 viral loads at the mucosa. Furthermore, DMPA-induced alterations in genital HIV-1 target cell numbers in the epithelium during acute HIV-1 infection will be associated with faster HIV-1 disease progression (as measured by CD4 decline to 350 cells/ml and viral load at 12 months).