Varicella-zoster virus—induced apoptosis in MeWo cells is accompanied by down-regulation of Bcl-2 expression

Varicella-zoster virus infects multiple human and monkey cells in culture. The mode of cell death appears to be autophagy or apoptosis. Analysis of VZV-infected human melanoma (MeWo) cells revealed that Bcl-2 mRNA and protein levels were decreased significantly 64 and 72 hpi (hours post infection), accompanied by the release of cytochrome c from mitochondria into the cytoplasm. Western blot analysis of virus-infected cells revealed activation of caspase-8, a marker for the extrinsic pathway of apoptosis, and caspase-9, a marker for the intrinsic pathway of apoptosis at 64 and 72 hpi. Significant increases in the levels of cleaved caspase-3 and cleaved poly (ADP) ribose polymerase (PARP) were also seen at the height of cytopathic effect. Thus VZV induces apoptosis in MeWo cells in which Bcl-2 is down-regulated. Future studies will determine differences in the cascade of apoptotic events in non-neuronal cells compared to neurons that allow VZV to become latent.