Introduction: Concentrations of zidovudine (ZDV)- and lamivudine (3TC)-triphosphates (TP) have been quantified in unfractionated peripheral blood mononuclear cells (PBMC) from HIV+ patients. The objective of this study was to determine whether concentrations of ZDV-TP and 3TC-TP in PBMC reflect the concentrations within CD4 T cells in HIV-seronegative adults.
Methods: Volunteers had taken 300 mg of ZDV plus 150 mg of 3TC twice daily for ≥ 7 days. Blood (60 mL) was collected 2 or 5 h post observed dose. PBMC were processed into three cell fractions using CD4 magnetic immunobeads: CD4-purified cells; unfractionated PBMC; and CD4-depleted PBMC. TP were determined in each cell fraction with liquid chromatography–mass spectrometry and compared across cell types by non-parametric analyses.
Results: Six males and two females participated. The median (range) percentage of CD4 T cells (CD4%) in each fraction were: CD4-purified, 99%; unfractionated, 63% (range, 53–70); and CD4-depleted, 14% (range, 4–29). Corresponding median (range) ZDV-TP concentrations were 8.0 (5.3–10.3), 26.5 (12.9–42.2), and 34.2 (16.4–52.2) fmol/1 × 106 cells (Friedman P = 0.0008). The 3TC-TP values were 4.6 (2.3–6.7), 4.8 (3.5–8.8), and 6.8 (4.0–13.1) pmol//1 × 106 cells (Friedman P = 0.01). In mixed model analyses: ZDV-TP (fmol/1 × 106 cells) = 42–0.32 (CD4%); P < 0.001 and 3TC-TP (pmol/1 × 106 cells) = 7.3–0.03(CD4%); P = 0.003.
Conclusions: In HIV-seronegative volunteers, 3TC-TP concentrations in PBMC reflected the concentrations within CD4 T cells, but ZDV-TP concentrations were more than 70% lower in CD4 T cells than in PBMC. Thus, TP concentrations differ according to cell type in vivo with corresponding efficacy and toxicity implications for cells with low or high triphosphates.
From the University of Colorado Health Sciences Center, Denver, Colorado, USA.
Received 14 December, 2006
Revised 11 March, 2007
Accepted 22 May, 2007
Correspondence to P.L. Anderson, University of Colorado Health Sciences Center, Box C238, 4200 E. 9th Ave., Denver, CO 80262, USA. Tel: +1 303 315 1720; e-mail: Peter.firstname.lastname@example.org