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

Abstract

Abstract 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.

Keywords

• BCG vaccine
• White-tailed deer
• Mycobacterium bovis
• T cell
• Oral vaccine
• Sodium alginate spheres