Under-explored experimental topics related to integral mycobacterial vaccines for leprosy.

Many leprosy vaccine studies have utilized live or killed whole mycobacteria, such as Bacille Calmette-Guérin, Indian Cancer Research Center (ICRC) bacilli and Mycobacterium w either alone or in combination with killed Mycobacterium leprae. For Bacille Calmette-Guérin, the vaccine dose is generally that which gives the largest delayed-type hypersensitivity response with minimal side effects. The doses of other integral mycobacterial vaccines appear to be arbitrarily chosen. Hypotheses governing immunologic responses to complex antigens predict that the doses used may be too high, resulting in protection of some individuals and increasing the susceptibility of other individuals to leprosy. The natural history of an individual's prior exposure to environmental mycobacteria will affect the outcome of protective vaccination using a given dose of mycobacterial vaccine in the individual.