Oral delivery of Mycobacterium bovis bacillus Calmette-Guérin (BCG) in alginate spheres to captive white-tailed deer

BACKGROUND: Bovine tuberculosis (bTB), caused by infection with Mycobacterium bovis, continues to be an animal and zoonotic concern in many parts of the world, including the United States. Long-standing eradication programs have been successful at lowering prevalence of disease in many countries; however, disease eradication has not been achieved. One major obstacle to eradication is the presence of various wildlife reservoirs for M. bovis, such as white-tailed deer (Odocoileus virginianus), which serve as a source of spill-back to cattle herds. A potential method to reduce intra- and inter-species disease transmission of M. bovis between wildlife and domestic livestock includes vaccination of wildlife species. Oral vaccination of white-tailed deer with the human tuberculosis vaccine, M. bovis bacillus Calmette-Guérin (BCG) has been demonstrated to afford some level of protection against experimental challenge. However, vaccinating wildlife presents its own challenges, primarily due to the need of a delivery platform that could be implemented at scale and would not require animal handling. RESULTS: Oral vaccine delivery units or baits are an effective means of delivering vaccine to wildlife populations. Therefore, we explored whether sodium alginate spheres could be used as a delivery platform for BCG for vaccination of white-tailed deer. We assessed the development of peripheral immune responses following BCG vaccination and demonstrated that passive administration of BCG via alginate spheres results in antigen-specific cellular responses, similar to oral administration of BCG. CONCLUSIONS: Our data characterize the kinetics of cellular responses elicited by oral vaccination and suggest passive oral administration of BCG as a potential means to vaccinate free-ranging white-tailed deer.