Because activated caspases 3, 7 and 8 can cleave PKR, releasing the biologically active C-terminus kinase domain from the Nterminus inhibitory domain, resulting in eIF2a phosphorylation [33] , we subsequently tested whether the accumulation of phosphorylated eIF2a following the combined activity of viral replication and ActD-treatment was due to induction of apoptosis [34] . VeroE6 cells, either infected with rMP12-rLuc or mockinfected, received the pan-caspase-inhibitor, benzyloxycarbonyl-Val-Ala-DL-Asp(OMe) fluoromethylketone (Z-VADfmk), in the presence of ActD or a-amanitin ( Figure S3 ). Judging from the resulting inhibition of cleaved caspase-3 accumulation in these cells, the Z-VADfmk treatment indeed inhibited apoptosis, whereas it had little effect on the eIF2a phosphorylation status and infectious virus yield. These data suggested to us that the accumulation of phosphorylated eIF2a in cells supporting rMP12-rLuc replication in the presence of ActD or a-amanitin was caspase-independent.