Reovirus Activates a Caspase-Independent Cell Death Pathway

Berger, Angela K.; Danthi, Pranav

To define how prodeath signaling following T3D and T1L differs, we compared the activations of initiator and executioner caspases following infection of L929 cells by these two strains. Measurement of the activity of the effector caspases, caspase-3 and -7, by chemiluminescent enzymatic assays 24 h after infection indicated that T3D activates these enzymes to a significantly greater extent than T1L (Fig. 1B) . Consistent with these results, we found that a greater amount of cleaved caspase-3 was detectable following infection with T3D (see Fig. S1C in the supplemental material). Bid cleavage, a marker for caspase-8 activation following reovirus infection (14) , also occurred more efficiently in T3Dinfected cells than T1L-infected cells (Fig. S1D) . Collectively, these data demonstrate that initiator and effector caspase activity fol- After incubation at 37°C for 24 h, caspase-3/7 activity in cell lysates was determined. Results are expressed as the mean ratios of caspase-3/7 activity from infected cell lysates to that from mock-infected cells for triplicate samples. Error bars indicate SD. *, P value of Ͻ0.05 as determined by Student's t test in comparison to cells infected with T3D. lowing infection of L929 cells with T3D is significantly higher than that following infection with T1L.