CASP9 and infection: The above results show that DTMUV infection of DEFs promotes the activation of caspase-8 and caspase-9 cleavage and that specific inhibitors of caspase-8 or caspase-9 can inhibit apoptosis, indicating that infection activates the caspase-9-mediated mitochondrial apoptotic pathway and the caspase-8-mediated death receptor apoptotic pathway.