Detection of bovine viral diarrhoea virus p80 protein in subpopulations of bovine leukocytes.

Flow cytometry and two-colour immunofluorescence were used to detect cytoplasmic bovine viral diarrhoea virus (BVDV) antigen in leukocytes from viraemic cattle. Monoclonal antibody to the p80 protein of BVDV, a non-structural viral antigen, was used to identify the subpopulations of leukocytes in which viral protein synthesis had occurred. Viral antigen was detected in 23% of peripheral blood mononuclear cells. Monocytes were found to have the highest frequency of infection (35%). A higher proportion of CD2+ T cells (23%) were infected, compared with B cells (11%) or WC1+ gamma delta T cells (11%). No significant differences in percentages of different leukocyte subpopulations in blood were detected in persistently viraemic animals compared with controls.