Silencing of APOBEC3A blocks monocyte resistance to HIV. (A) Monocytes were transfected with siRNA sequences specific for hA3A or a control siRNA (siC) or mock transfected (electroporation control [EPC]) before infection with HIV. Two to 3 days after HIV-1 infection, cells were processed and tested for viral DNA synthesis by nested PCR. (B) Transfected monocytes were adhered and infected with HIV-1. Supernatants were harvested every third day for analysis of p24 levels by ELISA (day 13 shown; mean ± SE). Differences between electroporation control (EPC) and siRNA for hA3A were significant (*P < .05). (Inset) Monocytes transfected as described in (A) with siRNA specific for hA3G or control sequences (siC) were infected with HIV-1 and supernatants were tested for HIV p24. (C) Transfected cells were cultured for 48 hours and treated with IFNα (10 ng/mL) overnight before monitoring of hA3A and α tubulin protein levels by Western-blot analysis.