Objective: To determine the duration for cross-neutralizing antibodies stimulated by administration of a single dose of a modified-live vaccine against bovine viral diarrhea virus (BVDV) to seronegative cattle.
Animals: 23 Angus cows seronegative to BVDV.
Procedure: Cows were randomly assigned to control (unvaccinated) or test (vaccinated) groups. Eighteen BVDV-seronegative Angus cattle were vaccinated via IM injection with a modified-live BVDV (NADL strain) vaccine and commingled with 5 unvaccinated seronegative cows. Serum was obtained from the cows before vaccination, on the day of vaccination, and 1.5, 3, 6, 9, 12, and 18 months after vaccination. Serum neutralizing antibody tests were performed on samples obtained at each point after vaccination, using a panel of 12 strains of BVDV that, on the basis of reactivity with monoclonal antibodies, were identified as heterologous.
Results: Antibodies against all 12 strains of BVDV (which we tested) were detected by use of viral neutralization testing in samples obtained from vaccinated cattle 18 months after vaccination; however, concentration of antibody for some of the strains was low. Nonvaccinated cattle remained seronegative throughout the 18-month study period.
Clinical implications: Analysis of these data indicated that modified-live BVDV vaccines could stimulate an antibody response in seronegative cows that was detectable for at least 18 months after vaccination. These antibodies were able to cross neutralize 12 antigenically diverse strains of BVDV.