Evaluation of multiple immune parameters after vaccination with modified live or killed bovine viral diarrhea virus vaccines.

The development of immunity to vaccine antigen was examined using three prime/boost strategies and the progression of immune activities was evaluated over the course of 8 weeks. Calves were vaccinated and multiple immune parameters were evaluated using several methods to assess humoral or cellular immunity from the same samples in parallel. The three vaccination protocols used were a killed vaccine followed by a killed boost (killed/killed), MLV vaccine and boost (MLV/MLV), or a MLV vaccine and killed boost (MLV/killed). All the vaccines used included modified live IBR/PI3 viruses to make the bystander context as similar as possible. The Singer strain of BVDV was used as the source antigen in the killed vaccine, and the NADL strain of BVDV was used in the MLV vaccine. Controls received a vaccine containing only MLV IBR/PI3. The assessment panel measured SN titers, as well as lymphocyte proliferation, cytokine mRNA expression, intracellular cytokine production, and released IFN-gamma after in vitro stimulation with three strains of BVDV virus. MLV/MLV and MLV/killed groups developed significant SN titers to the type 1 BVDV virus strains, Singer and NADL, and low crossover titers were also seen to the type 2 strain, 890 over the evaluation period. These two groups showed significant proliferation in response to the NADL virus as compared to controls. Multiple immune assessments were conducted simultaneously to attempt to provide a broader, more in depth evaluation of immune response to these BVDV vaccination protocols. We observed that the correlation among most of the assays conducted were weak; the correlation between SN titers and cellular proliferation assays demonstrated a moderate correlation.