Apoptosis induced by bovine ephemeral fever virus.

The potential significance of bovine ephemeral fever virus (BEFV)-induced apoptosis and involved viral molecules was fully unknown. In the present study, evidence is provided demonstrating that bovine ephemeral fever virus induces apoptosis in several cell lines. Five types of assays for apoptosis were used in examining BEFV-infected cells. (1) Assay for DNA fragmentation, (2) nuclear staining with acridine orange, (3) ELISA detection of cytoplasmic histone-associated DNA fragment, (4) terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick-end labelling (TUNEL) assay of BEFV-infected cells, (5) observation of blebbing of the plasma membrane and the formation of apoptotic bodies of apoptic cells by scanning electron microscope. The level of lactate dehydrogenase (LDH) in BEFV-infected cells was increased significantly after 20-25 h post-infection. Caspases-2, -3, -4, -6, -8, -9, and -10 were activated in BEFV-infected BHK-21 cells. To determine further whether BEFV-induced apoptosis was caspase-dependent, the effect of the tripeptide pan-ICE (caspase) inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyketone on the inhibition of apoptosis in BEFV-infected BHK-21 cells, was investigated. Apoptosis could be blocked by the caspase inhibitor (Z-VAD-fmk), indicating that BEFV induces caspase-dependent apoptosis in cultured cells.