West Nile virus-induced bax-dependent apoptosis.

The mechanism of cell death induced by West Nile virus (WNV), a causative agent of human febrile syndrome and encephalitis, was investigated. WNV-infected K562 and Neuro-2a cells manifested the typical features of apoptosis, including cell shrinkage, chromatin condensation and subdiploid DNA content by flow cytometry. DNA fragmentation into nucleosomal size and changes in outer cell membrane phospholipid composition were also observed in K562 cells. UV-inactivated virus failed to induce the above-mentioned characteristics, suggesting that viral replication may be required for the induction of apoptosis by WNV. Additionally, signals involved in WNV-induced apoptosis are associated with the up-regulation of bax gene expression.