Monocytes from four HIV-1- and hepatitis C virus-seronegative donors were isolated using RosetteSep (a positive-depletion monocyte enrichment method; Stem Cell Technologies, Vancouver, Canada) according to the manufacturer's protocol, which produces cell populations that are >99% CD14
+ monocytes with <1% B or T cells (CD3
+). MDM from four donors provided a 90% chance of detecting a twofold difference between virus- and mock-treated cultures, based on analysis of variance using a randomized complete block design, a two-sided
t test, and a standard deviation of 0.5. Cells were induced to adhere to plastic at a concentration of 2 × 10
6 per ml and were incubated in differentiation medium comprised of Dulbecco's modified Eagle's medium (Life Technologies, Gaithersburg, Md.) with 15% human AB serum (Sigma-Aldrich Corp., Saint Louis, Mo.) and a single treatment of 10 U of granulocyte-macrophage colony-stimulating factor (Invitrogen, Carlsbad, Calif.) per ml. After 7 days, >70% of cells expressed CD4 and >80% were positive for CCR5 as measured by flow cytometry (data not shown). After differentiation, CD14
+, Fcγ receptor
+ macrophages were the only cell type detected; no CD3
+ or CD19
+ T or B lymphocytes, respectively, were detected (
49,
73). MDM cultures were transferred to GM-CSF-free media and treated on day 0 with 2 ml of either HIV-1
JR-FL (multiplicity of infection, ∼0.02) or mock supernatants for 24 h, washed, and cultured in GM-CSF-free media. Levels of supernatant p24 antigen on days 2, 4, and 7 were assessed using a specific enzyme-linked immunosorbent assay kit (Coulter, Hialeah, Fla.). Aliquots of cells were washed twice with phosphate-buffered saline and lysed in a nonionic detergent buffer (50 mM KCl, 10 mM Tris-Cl, pH 8.3, 2.5 mM MgCl
2, 0.1 mg of gelatin/ml, 0.45% NP-40, and 0.45% Tween 20) containing proteinase K (100 μg per ml) (K buffer) for quantitation of infected cells by
TaqMan real-time PCR assay using HIV-1
gag as the analytical parameter and human
apoB as a genomic template control. The primers and probe used for quantitation of
apoB were as follows: forward primer, 5′-TGAAGGTGGAGGACATTCCTCTA; reverse primer, 5′-CTGGAATTGCGATTTCTGGTAA; probe, VIC (Applied Biosystems)-CGAGAATCACCCTGCCAGACTTCCGT-6-carboxy-tetramethylrhodamine (TAMRA). Viral
gag gene copies by
TaqMan were quantified using forward primer (5′-ACATCAAGCAGCCATGCAAAT-3′), reverse primer (5′-ATCTGGCCTGGTGCAATAGG-3′), and probe (5′-6-carboxy-fluorescein (FAM)-CATCAATGAGGAAGCTGCAGAATGGGATAGA-TAMRA-3′) (
19). Amplification reactions consisted of
TaqMan Universal PCR Master Mix (Applied Biosystems, Foster City, Calif.), 450 nM (each) forward and reverse primers, and 125 nM probe in a total volume of 50 μl. The PCR conditions were 50°C for 2 min and 95°C for 10 min, followed by 40 cycles of 95°C for 15 s and 60°C for 1 min. Thermal cycling and data acquisition were performed using a Prism 7700 Thermal Cycler (Applied Biosystems).