Viral tropism and Vpr-dependency. (A) SS-R5, N2-R5, and arsenic-treated N2-R5 cells were infected with R5-tropic WT or ΔVpr HIV-1 (NLAD8), and viral replication was detected by p24Gag ELISA. Data represent one of at least three independent experiments. (B) Measurement of cell growth rate under As2O3 treatment. Indicated cells were treated with 0.2 μM As2O3 or untreated. Cell numbers were counted daily after staining with trypan blue. (C) Effect of NaAsO2 on HIV-1 replication. Indicated cells were infected with WT or ΔVpr HIV-1 in the presence of 2 μM NaAsO2 and viral replication was detected by p24Gag ELISA.