Immune response to bovine viral diarrhea virus (BVDV) vaccines detecting antibodies to BVDV subtypes 1a, 1b, 2a,and 2c

Bovine viral diarrhea virus (BVDV) represents a major cattle disease with multiple forms including fetal infections resulting in persistently infected (PI) cattle. The objectives of this study were to investigate the immune response to six vaccines, five modified live viral (MLV) and one killed vaccine containing BVDV immunogens as measured by antibodies to BVDV1a, BVDV1b, BVDV2a, and BVDV2c. The predominant BVDV subgenotype in the U.S. is BVDV1b compared to BVDV1a and BVDV2a. There are MLV and killed BVDV vaccines containing BVDV1a and BVDV2a marketed in the U.S. A prior study evaluated immune response to vaccination with BVDV1a and BVDV2a inducing virus neutralizing antibody titers. BVDV1b titers 128 or higher at time of exposure to BVDV1b PI cattle protected heifers against fetal infection. Calves received two doses and postweaning serums were collected and assayed for BVDV antibodies. Antibody titers were expressed as geometric mean averages. Percentages were expressed as proportions of animals within three antibody levels, including targeted level 128 or greater. There were statistical differences among vaccines in each study, particularly to BVDV1a, BVDV1b, and BVDV2a. MLV vaccines containing Singer strain induced higher levels to BVDV1a and BVDV1b than NADL vaccine in all three studies. Two vaccines, both MLV, Vaccine 1 and Vaccine 6 containing Singer strain induced higher proportion of 128 or higher BVDV1b titers than vaccine with NADL. Antibody levels to BVDV2a and BVDV2c were dependent on BVDV2a vaccine strain. This study indicates strain in BVDV vaccines reflects differences in immune response to different BVDV subgenotypes, particularly BVDV1b and BVDV2c.