Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/4/2002
Publication Date: 4/4/2002
Citation: Interpretive Summary:
Technical Abstract: Interference by maternal antibodies prevents the development of an antibody response following vaccination with either a killed or attenuated BVDV vaccine. However, T cell mediated immune response to BVDV may be generated in the absence of a detectable serum neutralizing antibody response. Two trials were conducted to evaluate the potential to elicit T cell mediated immune responses to BVDV in calves with circulating maternal antibody to BVDV. In the first trial, calves with high levels of circulating maternal antibody to BVDV1 and BVDV2 were experimentally challenged with BVDV2 (strain 1373) at 2-5 weeks of age. The T cell mediated immune responses of the experimentally infected calves and noninfected calves were monitored. Calves experimentally challenged with BVDV developed BVDV specific CD4+, CD8+, and gamma delta T cell responses while high levels of maternal antibody were circulating. A second challenge with BVDV2 (strain 1373) was performed once maternal antibody could no longer be detected. Previous exposure to BVDV in the presence of maternal antibody protected calves from clinical signs of acute BVDV infection compared to the control calves. In the second trial, three groups of calves with circulating maternal antibody to BVDV were given either a modified-live vaccine (MLV) containing BVDV1 and BVDV2, a killed vaccine containing BVDV1 and BVDV2, or no vaccine, at 7 weeks of age. Serum neutralizing antibody levels and antigen specific T cell responses were monitored for 14 weeks following vaccination. Calves vaccinated with MLV BVDV developed BVDV1 and BVDV2 specific CD4+ T cell responses, and BVDV 2 specific gamma delta T cell responses, in the presence of maternal antibody. Vaccination with killed BVDV did not result in the generation of measurable antigen specific T cell immune responses. Calves vaccinated with either an MLV or killed BVDV vaccine while maternal antibody circulated developed a memory antibody response to BVDV2 upon subsequent vaccination. The results of these trials indicate that vaccinating young calves with MLV BVDV while maternal antibody is present generates T cell mediated immunity to BVDV.