Progress in the development of tuberculosis vaccines for wildlife

Tuberculosis vaccines in clinical trials

Effective prophylactic and/or therapeutic vaccination is a key strategy for controlling the global TB epidemic. The partial effectiveness of the existing TB vaccine, bacille Calmette-Guérin (BCG), suggests effective vaccination is possible and highlights the need for an improved vaccination strategy. Clinical trials are evaluating both modifications to the existing BCG immunization methods and also novel TB vaccines, designed to replace or boost BCG. Candidate vaccines in clinical development include live mycobacterial vaccines designed to replace BCG, subunit vaccines designed to boost BCG and therapeutic vaccines designed as an adjunct to chemotherapy. There is a great need for validated animal models, identification of immunological biomarkers of protection and field sites with the capacity for large-scale efficacy testing in order to develop and license a novel TB vaccine or regimen.

Update on vaccination of cattle and wildlife populations against tuberculosis

In this review, the status of vaccination strategies to reduce bovine tuberculosis of cattle and wildlife reservoirs of the disease is discussed, with a focus on recent developments. Recent work in vaccines to protect humans against tuberculosis has been followed by a similar surge of interest in developing vaccines against bovine tuberculosis. The human vaccine, bacille Calmette-Guérin (BCG) affords protection against tuberculosis in cattle, but this protection is variable. In addition, vaccination with BCG compromises control strategies based on skin testing animals. In general, no single vaccine approach has shown itself to be significantly superior to BCG alone, however, vaccine combinations of BCG and vaccinating moiety such as adjuvanted subunit, virus vectored or DNA vaccines have been shown to induce protection superior to that achieved by BCG alone. Vaccinating wildlife species against tuberculosis is also an area which has been subjected to scrutiny. Recent work has focused on vaccinating wildlife orally, via the use of BCG formulated in baits consumed by these species. Results from trials in a number of animal species indicate that oral BCG vaccination can reduce disease severity following experimental challenge with Mycobacterium bovis and in a recent field trial, oral BCG vaccination was shown to prevent infection of wild possums following natural exposure to M. bovis. In conclusion, recent studies in cattle and wildlife have demonstrated the practicality and effectiveness of vaccinating animals against tuberculosis and provide much impetus for future use of vaccines.