SUMMARY
Enriched populations of neutrophils and mononuclear leukocytes from 9 cattle persistently infected with non-cytopathic bovine viral diarrhea virus were analyzed for frequency of association with virus, using flow cytometric procedures. Trypsinization of neutrophils decreased the frequency of viral association from 0.82% to 0.49%. Similar treatment of mononuclear leukocytes decreased the frequency of viral association from 5.53% to 4.81%. Results of immunocytochemical procedures to locate viral antigen were inconclusive for neutrophils, but viral antigen was found in the cytoplasm of mononuclear leukocytes. A distinct and highly pure population of eosinophils was identified during flow cytometric analysis of neutrophil populations from 2 of 9 cattle.