Despite antiretroviral (ARV) therapy, HIV persists in tissue reservoirs throughout the body. Lymph node ARV penetration is crucial for HIV eradication, and the factors responsible for distribution are largely unknown. This study investigated the influence of drug transporters, sex, and SHIV infection on ARV and active metabolite concentrations within lymph nodes of rhesus macaques.
Twelve male (6 SHIV-, 6 SHIV+) and three female (2 SHIV-, 1 SHIV+) macaques were dosed to steady-state with six ARVs: emtricitabine (FTC, 16 mg/kg), tenofovir (TFV, 30 mg/kg), efavirenz (EFV, 200 mg/day), raltegravir (RAL, 200 mg/day), maraviroc (MVC, 150 mg/day), and atazanavir (ATZ, 270 mg/kg). At necropsy, 24h post-dose, three lymph nodes per animal were snap frozen and stored at -80°C. ARV and active metabolite (emtricitabine triphosphate, FTCtp; tenofovir diphosphate, TFVdp) concentrations were measured by LC-MS/MS (LLOQ: 0.002-0.01 ng/mL) and converted to ng/g of tissue using a density of 1.06 g/mL. Concentrations of eight (5 efflux, 3 uptake) drug transporters were measured using Quantitative Targeted Absolute Proteomics (QTAP, LLOQ: 0.1 pMol/mg protein). Median lymph node data for each animal was used for analyses. Data are presented as geometric mean (median range) and geometric mean ratio (GMR). Analyses were performed using Pearson Correlation, Kruskall-Wallis, and Mann-Whitney Rank Sum tests (p<0.05).
ARV concentrations are summarized in the table, and trended higher for 4/8 ARVs in SHIV- macaques (uninfected vs infected GMRs: 1.7-2.2), and 4/8 ARVs in females (female vs male GMR: 2.0–2.7). 5/8 transporters had low to no expression (>50% values below LLOQ). Concentrations of one efflux (BCRP) and two uptake (ENT1, OCT3) transporters were significantly greater than all others (p<0.001). ENT1 concentration was 8-fold higher than both BCRP and OCT3 (p<0.001). None of these three differed significantly by infection status (p=0.05) or sex (p>0.06). Transporter expression was not correlated with ARV or metabolite concentrations across sex or infection status.
Modest differences in lymph node drug concentrations due to sex and infection status were noted. Low drug transporter levels, and lack of correlation between protein and drug concentrations, may indicate that lymph node ARV penetration occurs primarily by passive mechanisms. Future studies are warranted to further investigate sex differences in lymph nodes.