At 72 h post-infection, the active form of caspase-3 was detected in Flag-Vpr-expressing cells but not in control cells by Western blot analysis with anti-caspase-3 antibody (Figure 3A), and G2 arrest was observed in Flag-Vpr expressing cells using a CELAVIEW microscope (Figure 3B). This evidence concerns the gene CASP3 and infection.