Global Expression of Molecular Transporters in the Human Vaginal Tract: Implications for HIV Chemoprophylaxis

Abstract

BackgroundPre-exposure chemoprophylaxis (PrECP) using antiretroviral agents is a promising strategy for the prevention of sexual HIV transmission in women. Molecular transporters in the human vaginal tract (VT) may play a pivotal role in determining drug disposition and, consequently, pharmacodynamic outcomes in these efforts. Little is known, however, on the expression of these transporters in vaginal tissues, representing a critical knowledge gap.Methodology/Principal FindingsOur study analyzed the genome-wide transcriptome in 44 vaginal tissue samples from 6 reproductive-age women undergoing gynecologic surgeries. The analysis revealed that, unexpectedly, a large number (43%) of gene isoforms corresponding to membrane transporters were over-expressed (above the median expression level) in all samples. A subset of 12 highly expressed membrane transporters was identified and contained 10 members (83%) of the solute carrier superfamily. The largest difference in membrane transporter gene expression was observed across subjects, but more subtle differential expression also was found along the anterior-posterior axis of the VT. Cross-validation of the microarray analyses with measurements RT-qPCR demonstrated high concordance between these data sets. Immunofluorescence labeling of membrane transporter proteins in vaginal tissues was highly dependent on tissue/cell types.Conclusions/SignificanceAntiretroviral PrECP drugs currently under evaluation are substrates for molecular transporters that were commonly expressed, but fell into both over- or under-expressed categories in all samples, suggesting a complex role for carrier-mediated processes in determining the disposition of these xenobiotics in vaginal tissues. These findings hold important implications for the successful development of products, either oral or intravaginal, for female-controlled HIV PrECP.

Pharmacokinetics and Preliminary Safety Study of Pod-Intravaginal Rings Delivering Antiretroviral Combinations for HIV Prophylaxis in a Macaque Model

“…6). Paired vaginal fluid and tissue ARV drug levels proximal and distal to the IVR on day 7 and day 22 were poorly correlated, suggesting that mucosal uptake and distribution are dependent on host characteristics such as menstrual status, the structure of the vaginal epithelium, and expression of membrane transporters (42) and ARV drug-metabolizing enzymes (43) in addition to xenobiotic physicochemical characteristics. Overall, the drug distribution in vaginal fluids and tissues was homogeneous, with few statistically significant concentration gradients extending distally from the IVR.…”

Combination Pod-Intravaginal Ring Delivers Antiretroviral Agents for HIV Prophylaxis: Pharmacokinetic Evaluation in an Ovine Model

“…An inefficient drug delivery profile of the matrix-IVR, combined with low release rates after the first week of use, could explain the low MVC tissue levels encountered clinically (33). This explanation seems more likely than that of significant active efflux from vaginal epithelial cells mediated by the membrane transporter p-glycoprotein (ABCB1), as it has been found to be underexpressed in VTs (40,47).…”

Vaginal ecosystem modeling of growth patterns of anaerobic bacteria in microaerophilic conditions

“…In previous work, we employed microarray, qRT-PCR and immunolabeling to evaluate human vaginal tissues and in VEC cultures to identify the subset of ABC and SLC transporters that were expressed [1, 19]. Selected vaginally-expressed transporter genes were evaluated in cultures with shifted VMB profiles created by CO 2 supplementation in the VEC model.…”

“…Custom qPCR arrays were built for selected immune response-related genes and molecular transporters (Supplemental Tables 1 and 2) [21–23] and subjected to qPCR with SYBR green detection in CFX amplification systems (Bio-Rad) as described previously [24]. Gene targets were selected following previously identified gene expression in human vaginal mucosa tissues [19]. Melt temperatures for each amplified target were matched to historic controls and genes with melt curves outside ± 0.6 C were eliminated from further analysis.…”

“…As an initial study of the molecular signals associated with alterations of the vaginal environment, we quantified changes in immune response and molecular transporter gene expression with custom RT-PCR arrays as an extension of our previous work [19]. Collectively, the results from two genetically distinct VEC donors suggest that increasing CO 2 in the vaginal lumen favors selected lactobacilli that are defined as microaerophiles or aerobes and are considered probiotic organisms.…”