FIG. 5.

Caspase activation induced by virion-associated Vpr is independent of the Fas receptor pathway. Jurkat cells were infected at an MOI of 0.5 with the indicated viruses for 2 hours. After the 2 h of infection, cells infected with Vpr(+)^trans viruses were cultured for 48 h in the presence or absence of the Fas-neutralizing antibody ZB4 (2.5 μg/ml). Forty-eight hours postinfection, caspase 3/7, 8, and 9 activities were measured for each sample by using the appropriate Caspase-Glo assay. As a positive control for the neutralizing effect of the ZB4 antibody, uninfected cells were preincubated with the ZB4 antibody (2.5 μg/ml) for 6 h before the addition of the Fas-stimulating CH11 antibody (12.5 ng/ml). Caspase activities were then measured 42 h later. Blank values were subtracted, and the increase in activity was calculated based on activity measured from mock-infected cells. The black, white, and gray bars represent caspase 3/7, 8, and 9 activities, respectively. The results are shown as means plus standard deviations.