Fig. 2.

Pre-treatment with N/OFQ fails to induce internalization of CXCR4, while reducing susceptibility to infection with X4 HIV-1. Human CD4-positive T cells (a, closed symbols), CD14-positive monocytes (a, open symbols), Jurkat T cells (b, closed symbols), and U937 monocytes (b, open symbols) were pre-treated with N/OFQ at the designated concentrations, and the expression of CXCR4 was determined after 60 min by flow cytometry. In each case, cells were also pre-treated with CXCL12 (100 ng/ml) as a positive control for homologous desensitization (square symbols). Results are expressed as a percentage of the CXCR4 expression in control cultures (no pre-treatment with N/OFQ or CXCL12) of triplicate cultures (± SEM), and are representative of 3–5 independent experiments. Assessment of HIV-1 susceptibility was carried out by treating T cells with 1 nM N/OFQ for 60 min, followed by infection with HIV-1 strain MN (MOI 0.1) for 2 hr (c). DNA was isolated from the cells at 2 hr and the reverse transcription of HIV strong-stop cDNA was determined by real time PCR. Results are expressed as the mean (± SEM) of triplicate cultures, and are representative of experiments with 5 independent donors. *, P < 0.05.