VACV replication in APOBEC3G-expressing HeLa cells. A: APOBEC3GmycHis is expressed in 90% of HeLa-APOBEC3G cells. Expression was confirmed by intracellular staining with a mouse anti-Myc antibody (BDBiosciences, Heidelberg) and a FITC-conjugated anti-mouse IgG antibody (Dianova, Hamburg) followed by FACS analysis. B: Viral replication is not impaired by APOBEC3G expression. HeLa-APOBEC3G and HeLa cells were infected with VACV strain WR at an MOI of 0.05 and viral titers were measured 0, 24 and 48 h post infection by titration on RK13 cells.