FIG. 2.

rM51R-M virus induces caspase-8-like and caspase-9-like activities. Fluorometric caspase assays were performed using substrates for caspase-8 (A) and caspase-9 (B). L929 cells were left untreated (Mock), infected with rwt virus or rM51R-M virus, treated with 50 nM TRAIL (A), or treated with 1 μM SSP (B). At 8 (black bars), 16 (hatched bars), and 24 (white bars) h postinfection, cells were lysed and caspase activities were measured with fluorogenic substrates. Caspase activities are expressed in arbitrary fluorescence units per milligram of total protein and are normalized to the maximum values expressed by the positive controls, TRAIL and SSP, respectively. The data represent the averages ± SEM from three experiments. hpi, hours postinfection; *, P is <0.05 relative to mock-infected samples; **, P is <0.001 relative to rM51R-M virus-infected samples at 16 h postinfection.