Preexposure prophylaxis (PrEP) with oral administration of an antiretroviral is a potential method for preventing acquisition of HIV.A controlled trial in men who have sex with men (the iPrEx trial) showed that daily oral use of tenofovir disoproxil fumarate-emtricitabine (TDF-FTC; Truvada) reduced transmission rates by 44% (Grant et al., 2010).In addition, the HIV Prevention Trial Network (HPTN) 052 trial recently confirmed that antiretroviral treatment leads to 96% reduction in transmission among HIV-neg. heterosexual partners of HIV-pos. individuals (Cohen et al., 2011).Similar trials, however, with TDF-FTC (the FEM-PrEP trial) or TDF alone (the VOICE trial) were stopped because of poor outcomes (van der Straten et al., 2012).Different results among various trials, which used identical antiretroviral regimens, could be explained by varying compliance with drug use and/or varying drug concentration and activity within the exposed tissue (Patterson et al., 2011).Langerhans cells (LCs) are CCR5+ dendritic cells located within genital skin and mucosal epithelium (Lederman et al., 2006).In female rhesus macaques exposed intravaginally to simian immunodeficiency virus, up to 90% of initially infected target cells were LCs (Hu et al., 2000).Ex vivo experiments with human foreskin explants show that epidermal LCs are target cells for HIV, providing a likely explanation for why circumcision greatly reduces the probability of acquiring HIV (Ganor et al., 2010).LCs also express CD4 and CCR5, but not CXCR4, within the tissue and demonstrate the distinctive characteristics of emigrating from tissue to draining lymph nodes in order to interact with T cells after contact with pathogens (Kawamura et al., 2000).Indeed, epidermal LCs are readily infected ex vivo with R5 HIV, but not with X4 HIV, and promote high levels of infection upon interaction with cocultured CD4+ T cells (Kawamura et al., 2000; Ogawa et al., 2013).Thus, LCs probably have an important role in disseminating HIV soon after exposure to virus.Epidemiol. observations have found that the majority of HIV strains isolated from patients soon after initial infection are R5 HIV strains (i.e., they utilize CCR5; Lederman et al., 2006).Not surprisingly, individuals with homozygous defects in CCR5 are largely protected from sexually acquiring HIV (Lederman et al., 2006).In addition, three different CCR5-binding topically applied compounds protected female macaques from sexually acquiring simian/human immunodeficiency virus: the N-terminally modified chemokine analog PSC-RANTES, the small-mol. inhibitor CMPD167, and maraviroc (MVC) (Lederman et al., 2006; Veazey et al., 2010).In addition to topical application to vaginal mucosa, oral delivery of CMPD167 protected macaques from vaginal simian/human immunodeficiency virus challenge (Veazey et al., 2005).Given these data, orally administered MVC may prove to be particularly important in PrEP regimens, although its ability to prevent HIV acquisition is unknown.In the current study, 20 healthy volunteers were randomly divided into four equal groups; they received 300mg of MVC orally twice daily for 1, 2, 3, or 14 days.To obtain epidermal tissues, all subjects underwent suction blistering of the skin before and 2hours after the last MVC dose.All subjects had plasma and semen collected 2hours after their last dose.MVC concentrations in serum, semen, and epidermal tissues were determined by using the liquid chromatog.- mass spectrometry method, as described previously (Takahashi et al., 2010).Mean concentration±SD in the epidermis was 21.91±13.80, 23.36±13.28, and 31.54±20.61nM for individuals taking drug for 1, 2, or 3 days (n=5 for each), resp.MVC concentrations tended to be higher with a longer dosing period.Consistent with recent data showing high levels of MVC in genital tissue (Dumond et al., 2009), these results indicate that MVC rapidly distributes into the skin at high concentrationsIn addition, MVC was detected in semen of all subjects (Supplementary Figure S1 online).To understand how HIV traverses skin and genital mucosa, an ex vivo model was developed whereby resident LCs within epithelial tissue explants are exposed to HIV and then allowed to emigrate from tissue, thus mimicking conditions that occur after mucosal exposure to HIV (Kawamura et al., 2000; Ogawa et al., 2013).In this model, although relatively few productively infected LCs are identified, these cells induce high levels of HIV infection when cocultured with resting autologous CD4+ T cells (Kawamura et al., 2000).In preliminary experiments, HIV infection of LCs, as well as subsequent virus transmission from emigrated LCs to cocultured CD4+ T cells, was decreased in a dose-dependent manner when skin explants were pretreated with various concentrations of MVC before HIV exposure (Supplementary Figure S2 online), similar to experiments reported earlier with PSC-RANTES (Kawamura et al., 2004).Next, the epithelial tissue explants were collected from study subjects after oral treatment with MVC (Supplementary Materials and Methods online).Importantly, oral MVC pretreatment for either 1 or 2 days partially inhibited subsequent ex vivo HIVBa-L infection of LCs within epithelial tissue, whereas MVC administration for either 3 or 14 days completely blocked LCs from ex vivo HIVBa-L infection (Figure 1).These data demonstrate the importance of the length of MVC dosing period before HIV exposure.MVC treatment also consistently prevented HIVBa-L transmission from LCs to cocultured CD4+ T cells (Figure 2).Furthermore, MVC administration for 3 days blocked ex vivo virus infection of LCs as well as subsequent virus transmission when different R5 HIV strains, HIVAD8 and HIVJR-FL, were utilized for an addnl. six subjects (n=3 for each strain, Figures 1 and 2).These data demonstrate that oral administration of MVC for at least 3 days is capable of fully protecting HIV infection of LCs within epithelial tissue.These experiments provide perhaps the best proof-of-concept test for MVC as a potential PrEP drug, as it would be unethical to expose MVC-treated volunteers to HIV in vivo.As proven here, orally delivered MVC rapidly distributes to skin and functionally acts to block infection of relevant target cells, LCs, supporting randomized controlled trials of MVC as a PrEP therapy for individuals at high risk of becoming infected with HIV through sexual exposure.
