Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2009
Publication Date: 10/7/2009
Citation: Fulton, R.W., Ridpath, J.F., Burge, L.J., Step, D.L., Johnson, B.J., Kapil, S. 2009. Bovine Viral Diarrhea Virus Experimental Live Virus (BVDV1b and BVDV2b) Vaccines in Cattle: Immunogenicity Studies with Antibody Response to Multiple BVDV Subgenotypes [abstract]. American Association of Veterinary Laboratory Diagnosticians. p. 125. Interpretive Summary:
Technical Abstract: Bovine viral diarrhea viruses (BVDV) are a diverse group of viruses causing infection and diseases in cattle worldwide. There are two major types of BVDV, BVDV1 and BVDV2. There are currently reported 12 different BVDV1 subgenotypes (BVDV1a-BVDV1l) and two BVDV2 subgenotypes (BVDV2a and BVDV2b). In the US, the three subgenotypes are BVDV1a, BVDV1b, and BVDV2a, although there is a report of a cytopathic (CP) BVDV2b. The principal BVDV subgenotype in the United States is BVDV1b based on accessions to diagnostic laboratories, typing of persistently infected (PI) cattle entering the feedlot, and a regional study of BVDV in young dairy calves. However, most vaccines in the United States contain BVDV1a and BVDV2a with a few only containing BVDV1a or BVDV1 (subgenotype not identified) strains. There are no BVDV1b vaccines currently licensed in the United States. There are antigenic differences among the BVDV1a, BVDV1b, and BVDV2a strains. The question remains: would vaccine efficacy be improved by the inclusion of the subgenotype for the predominant strain in a population. The objectives of this study included: (1) development of BVDV1b and BVDV2b live viral vaccines for use in cattle; (2) detection of an active immune response in susceptible calves as measured by viral neutralizing antibodies in the serums to multiple strains; (3) detection of viremia post vaccination and potential for viral shedding in vaccinates; (4) ability of viral infection in vaccinates to cause skin test positive reactions post vaccination; and (4) comparison to a commercial vaccine containing MLV BVDV1a and BVDV2a strains. There were five groups of calves: (1) nonvaccinate controls ;(2) BVDV1b CP experimental vaccine given SQ; (3) BVDV1b experimental vaccine given IM; (4) BVDV2b CP experimental vaccine given SQ; and (5) commercial MLV vaccine containing BVDV1a and BVDV2a given IM. The calves were bled weekly from day 0 to day 42. The blood leukocytes were assayed for infectious virus on the weekly samples and serums assayed for BVDV antibodies to BVDV1a (Singer), BVDV1b (TGAC), BVDV2a (125C), and the BVDV2b CP vaccine strain. Skin samples were tested for BVDV antigen using the IHC and ACE. And the day 0, 7, 14, and day 42 serums were tested by a gel-based reverse transcriptase PCR assay. The skin samples were negative at all collections to the IHC and ACE. There were no viremias detected by viral isolation, although a limited number of PCR positives were noted in the experimental vaccinates. There was no evidence of viral shedding as indicated by failure to seroconvert by the nonvaccinated control group animals that were housed together. The experimental BVDV1b CP vaccine given either by SQ or IM induced greater antibody levels to BVDV1b at days 21,28 and 42 compared to the commercial BVDV vaccine containing BVDV1a and BVDV2a (P value-<0.05). And the experimental BVDV1b vaccine given IM induced higher BVDV1a antibody levels than the commercial vaccine at day 42. The experimental BVDV2b vaccine induced higher BVDV2a and BVDV2b antibody levels at days 14,21,28 and 42 than the commercial BVDV vaccine containing BVDV1a and BVDV2a (P=<0.05). These results indicate the uniqueness of the experimental BVDV1b vaccine to induce higher levels of antibody to BVDV1b, the most common BVDV strain in many surveys, than a commercial MLV vaccine containing BVDV1a and BVDV2a. Likewise the BVDV2b vaccine demonstrated ability to induce antibodies to the heterologous BVDV2a. In summary, the BVDV experiment vaccines offer potential for commercial development, especially the BVDV1b vaccine.