524 Regulation and Effects of T-lymphocyte P-glycoprotein Activity during HIV-1 Infection T. Hulgan*1,2, J.P. Donahue1, C. Hawkins1, R. T. D'Aquila1, F. Nicotera1, P. Rebeiro2, M. Rueff1, H. Erdem1, D. Unutmaz1, D. W. Haas1,2 1Vanderbilt Univ Sch of Med, Nashville, TN and 2Comprehensive Care Ctr, Nashville, TN
Background: The efflux pump P-glycoprotein (P-gp) decreases disposition of HIV protease inhibitors (PI) into selected cells. Causes and effects of variable lymphocyte P-gp activity are uncertain. We are studying a cohort of HIV-infected adults to identify pharmacologic, viral, and host factors regulating P-gp activity. Naive CD8+ lymphocytes are of interest because they are relatively quiescent, are not infected by HIV, are more homogeneous than total CD8+ cells, and have relatively high P-gp activity.
Methods: P-gp activity was defined as percent of cells that efflux 3,3'-diethyloxacarbocyanine iodide. Results were adjusted by results with complete P-gp inhibition by 19 µM verapamil. Control samples from healthy HIV-negative adults confirmed reproducibility. Naive (CD62L+/CD45RA+) CD8+ and CD4+ lymphocytes were identified by flow cytometry. Demographic, clinical, laboratory, and treatment data was obtained from an electronic database. Wilcoxon rank sum, Kruskal-Wallace tests, simple correlation, and regression analyses were performed.
Results: P-gp efflux function was determined in 204 subjects, of whom 79% were male, 65% were Caucasian, 33% were African-American, and mean age was 41 yrs. A total of 146 (72%) were receiving ART, 33% were receiving only NRTIs, 25% were receiving a NNRTI, and 48% were receiving a PI. Naive CD8+ lymphocyte P-gp activity ranged from 16%-93% (median = 67%). By univariate analysis, higher P-gp activity correlated with lower log10 HIV-1 RNA (p < 0.001) and higher CD4+ T-cell counts (p < 0.001), but not with antiretroviral drug class, race, gender, or age. By multivariate analysis, both log10 HIV-1 RNA (p < 0.001) and CD4+ T-cell counts (p = 0.002) correlated with naive CD8+ lymphocyte P-gp activity. P-gp activity on total and naive CD4+ T-cells was associated with low HIV-1 RNA concentrations (p < 0.001 for each). P-gp activity in naive CD8+ lymphocytes correlated with P-gp activity in total CD8+ and CD4+ lymphocytes, and naive CD4+ lymphocytes (p < 0.001).
Conclusions: Lower plasma HIV-1 RNA and higher CD4+ T-cell counts are independently associated with higher naive CD8+ lymphocyte P-gp activity. Increased CD4+ T-cell P-gp activity is associated with decreased HIV replication. Mechanisms may include decreased P-gp activity caused by HIV replication, or decreased HIV replication caused by greater P-gp function. Further study will clarify medication effects on P-gp activity, and whether regulation is at the mRNA or protein level.
