SIVmac239 (A), SIVmac251 (B) or SHIVSF162P3N (C) were incubated with the indicated concentrations of macaque SEVI for 1 h prior to the addition of TZM-bl cell cultures. At 48 h postinfection, the cells were lysed and the luminance (RLU/s) was determined by SpectraMax. The numbers above the bars are the folds of enhancement of luciferase reporter gene activities relative to those measured in the absence of macaque SEVI. Data were expressed as mean ± SD of three independent experiments (*P<0.05, **P<0.01, ***P<0.001, compared with no treatment control).