Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/5/2010
Publication Date: 12/5/2010
Citation: Waters, W.R., Palmer, M.V., Thacker, T.C. 2010. Bovine tuberculosis: Immune response and vaccine efficacy studies. Proceedings of the Conference of Research Workers in Animal Diseases. p. 18.
Technical Abstract: Bovine tuberculosis (TB) is a re-emerging disease of cattle within the United States, primarily due to importation of infected cattle from Mexico and the emergence of a wildlife reservoir (white-tailed deer) in Michigan. While the mainstay of bovine TB control has been abattoir inspection plus targeted test/cull campaigns, vaccines are now being considered as an additional tool for control, both in cattle and wildlife. To evaluate candidate TB vaccines, a neonatal calf model was developed to objectively measure efficacy and immunogenicity. Calves are vaccinated at ~2 wks of age and virulent M. bovis delivered by aerosol at ~3.5 months of age. Variables used to evaluate vaccine efficacy include: gross pathology, radiograph morphometry, histopathology, mycobacterial culture (quantitative and qualitative), and various immune parameters. A similar protocol was developed for evaluation of vaccine efficacy in WTD; however, the vaccine is administered to young adults (~1 yr of age) and M. bovis is delivered by instillation into the tonsilar crypts. For calves, vaccination with M. bovis Delta RD1 (the primary attenuating defect of M. bovis BCG) induced protection equivalent to BCG. Mean central memory T cell responses elicited by either M. bovis Delta RD1 or BCG prior to challenge correlated with reduced pathology and bacterial colonization. Reduced in vitro recall responses after challenge were also associated with effective Delta RD1 and BCG vaccines. Vaccination of white-tailed deer with BCG by either subcutaneous or oral routes resulted in reduced M. bovis–associated pathology compared to non-vaccinates; however, BCG persisted within tissues up to 250d, disseminated to distant lymphoid tissues, and transmitted from deer to deer. In addition to vaccine efficacy studies, this review highlights recent advances in our understanding of the immunopathogenesis of bovine TB.