The F2 compound blocks an early step of HIV-1 replication. A. Structure of compound F2. B.Dose–response curve of F2 in 293T cells challenged with the VSVg pseudotyped pNL4-3lucR+E- vector. The effect of the compound on infection was determined by measurement of virus-encoded firefly luciferase activity. The experiment shown, performed with triplicate samples, is representative of six independent experiments. C. Dose–response curve of F2 in CEM-GFP cells challenged with the pLai3Luc2 HIV-1 vector.The numbers of GFP positive cells at 2 days post-infection were determined by flow cytometry and the experiment shown, performed with duplicate samples, is representative of two independent experiments. D. Dose–response curve of F2 in human PBMCs challenged with the NL4-3 Nef+ IRES rluc vector encoding renilla luciferase activity, measured at 5 days post-infection. The experiment shown was performed with eight replicate samples. The error bars (panels B-D) represent the standard errors of the mean.