SPECIFICITY AND DURATION OF NEUTRALIZING ANTIBODIES INDUCED IN HEALTHY CATTLE AFTER ADMINISTRATION OF A MODIFIED-LIVE VIRUS-VACCINE AGAINSTBOVINE VIRAL DIARRHEA

Objective-To determine the duration for cross-neutralizing antibodies stimulated by administration of a single dose of a modified-live vacci ne against bovine viral diarrhea virus (BVDV) to seronegative cattle. Animals-23 Angus cows seronegative to BVDV. Procedure-Cows were random ly assigned to control (unvaccinated) or test (vaccinated) groups. Eig hteen 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 befor e vaccination, on the day of vaccination, and 1.5, 3, 6, 9, 12, and 18 months after vaccination. Serum neutralizing antibody tests were perf ormed on samples obtained at each point after vaccination, using a pan el of 12 strains of BVDV that, on the basis of reactivity with monoclo nal antibodies, were identified as heterologous. Results-Antibodies ag ainst all 12 strains of BVDV (which we tested) were detected by use of viral neutralization testing in samples obtained from vaccinated catt le 18 months after vaccination; however, concentration of antibody for some of the strains was low. Nonvaccinated cattle remained seronegati ve throughout the 18-month study period. Clinical Implications-Analysi s of these data indicated that modified-live BVDV vaccines could stimu late an antibody response in seronegative cows that was detectable for at least 18 months after vaccination. These antibodies were able to c ross neutralize 12 antigenically diverse strains of BVDV.