Drug efflux transporters and metabolic enzymes in human circulating and testicular T-cell subsets: relevance to HIV pharmacotherapy.

OBJECTIVES: ATP-binding cassette (ABC) drug efflux transporters and drug metabolic enzymes could reduce antiretroviral (ARV) concentrations in HIV target cells. The testis has been demonstrated to be a sanctuary site, displaying suboptimal ARV concentrations and persistent HIV infection. Therefore, we compared the expression and function of ABC transporters and metabolic enzymes in CD4 and CD8 T cells isolated from human testis and peripheral blood mononuclear cells (PBMCs), and assessed their expression in circulating naïve and memory CD4 T-cell phenotypes.

DESIGN: Testicular tissue and blood were collected from 15 uninfected donors undergoing gender affirmation surgery. Testicular interstitial cells were isolated by enzymatic digestion, whereas PBMCs were isolated from blood by density gradient centrifugation. The expression and/or function of ABC transporters and metabolic enzymes were examined in blood and testicular T-cell subsets by flow cytometry.

RESULTS: ABC transporters (P-gp, BCRP, MRP1) and metabolic enzymes (CYP3A4, UGT1A1) were expressed in testicular and circulating CD4 and CD8 T cells, as well as in circulating naïve, central, transitional, and effector memory T-cell phenotypes. MRP1 demonstrated lower frequencies in T cells from testis compared with PBMCs, as well as in circulating naïve T cells compared with the memory T-cell phenotypes. Functional activity of P-gp and BCRP was detected in T-cell subsets from testis and PBMCs.

CONCLUSION: Our findings demonstrate for the first time that ARV drug efflux transporters and metabolic enzymes are functionally expressed in T-cell subsets infiltrating the human testis. These transporters and enzymes can reduce ARV intracellular concentrations, potentially contributing to residual HIV replication in the testis, and negatively impact HIV cure strategies.