Apoptotic events induced by prototype foamy virus infection

Foamy virus infection induces cytopathology in several cell types from different species. But the exact mechanism is still unknown. In this study, we have investigated the mechanism of cell death induced by prototype foamy virus (PFV) infection in baby hamster kidney (BHK 21) cell lines. PFV induces apoptosis by exhibiting morphological alterations such as chromatin condensation, blebbing, and nuclear fragmentation. In addition, PFV infection causes chromosomal DNA fragmentation, up-regulation of Bax, and activation of caspase-3, but not caspase-8. Up-regulation of Bax initiates the translocation of cytochrome-c from mitochondria to the cytoplasm, suggesting predominantly to the mitochondrial-mediated pathway. Blocking apoptosis using caspase inhibitors increased PFV-infected BHK 21 cell viability. Although blocking apoptosis resulted in reduced progeny release, maximal accumulation of PFV was found in apoptosis-blocked cells. This report provides the first experimental evidence of apoptosis induced by PFV infection, which will provide valuable insights for foamy viral pathology.