Bovine viral diarrhea virus induces apoptosis in blood mononuclear cells by a mechanism largely dependent on monocytes

The induction of apoptosis by bovine viral diarrhoea virus (BVDV) was examined in bovine peripheral blood mononuclear cells (PBMC) incubated with an antigenically homologous pair of non-cytopathic and cytopathic BVDV. Our results show that the cytopathic biotype, in contrast to the non-cyto- pathic counterpart, induces apoptosis in PBMC. Flow cytometry analysis of cells undergoing apoptosis revealed that: (1) monocytes constitute the major cell population undergoing apoptosis; (2) cytopathic virus also induces apoptosis in BoCD4 , BoCD8 andBoWC1 T cells in whole PBMC cultures but not in purified T cell suspensions; (3) the degree of apoptosis of BoCD4 and BoCD8 T cells incubated with the cytopathic virus was significantly enhanced by the presence of monocytes. Taken together, these results suggest that bovine monocytes play an important role in apoptosis induced by cytopathic BVDV.