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 cytopathi c BVDV. Our results show that the cytopathic biotype, in contrast to t he non-cytopathic counterpart, induces apoptosis in PBMC. Flow cytomet ry analysis of cells undergoing apoptosis revealed that: (1) monocytes constitute the major cell population undergoing apoptosis; (2) cytopa thic virus also induces apoptosis in BoCD4(+), BoCD8(+) and BoWC1(+) 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 monocy tes play an important role in apoptosis induced by cytopathic BVDV.