Western blots showed significant activation of caspase-3, -9, -7, and poly (ADP-ribose) polymerase (PARP) (which indicated intrinsic apoptotic pathway activation), but not caspase-8 (which is involved in the extrinsic apoptotic signaling pathways), after 48 h of infection (Figure 4G). Here, CASP3 is linked to infection.