Vpx increases HIV-1 provirus content in monocytes. Freshly isolated CD14+ monocytes from human peripheral blood were either treated with ΔVpx-VLPs, Vpx-VLPs or 2.5 mM deoxynucleosides. 1 × 106 cells were harvested for western blot (A), 2 × 106 collected for nucleotide measurement (B) and 0.5 × 106 were challenged 2 hrs after treatment with a HIV-1 reporter vector to assess GFP expression by flow cytometry (C). Samples were collected before treatment (0 hrs), 3 hrs two days (D2) and five days (D5) after treatment. HIV-1 LRT (D) and 2-LTR circles (E) were measured 3 days after infection and integrated provirus was analyzed by Alu-PCR at day 5 (F).