Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 11, 2001
Publication Date: November 11, 2001
Technical Abstract: Bovine viral diarrhea virus genotype 2 (BVDV2) strains differ in the type and severity of disease they cause. Acute infections with highly virulent BVDV2 are associated with prolonged fever, leukopenia, severe thrombocytopenia, and diarrhea. Leukopenia occurs within 6 days of infection and reflects a greater than 60% drop in circulating lymphocytes. This decrease is evident in all lymphocyte subsets. To determine if leukopenia is associated with an apoptotic event, colostrum-deprived calves, tested free of BVDV and BVDV antibodies, were infected with BVDV2 strains. Naturally avirulent, highly virulent, cytopathic, and noncytopathic strains were tested. Basal body temperatures were taken daily. Blood samples were collected on days 0, 3, 6, 9, and 13 day post infection. Circulating lymphocytes were counted and virus isolation was performed on buffy coat samples. Numbers of apoptotic circulating lymphocytes were monitored by the binding of fluorescein labeled annexin to unfixed circulating lymphocytes. Annexin binding occurs when apoptotic events results in translocation of proteins to the host cell surface. Using the annexin assay, an increase in apoptotic lymphocytes could be detected as early as day 3 with some viral strains. The percentage increase in apoptotic cells did not correlate with biotype. The largest increase in apoptotic circulating lymphocytes was observed when animals were infected with noncytopathic highly virulent strains.