Reduction of Mycobacterium tuberculosis infection in Bacillus Calmette Guerin immunized people is due to training of innate immunity.

The currently used vaccine for prevention of tuberculosis is Bacillus Calmette Guerin, which has been associated with a protective effect of 51% against tuberculosis. New vaccination strategies based on an enhancement of adaptive T-cell based immunity have been unsuccessful in increasing the efficiency of BCG immunisation. The proposed hypothesis is that a reduction of Mycobacterium (M.) tuberculosis infection in Bacillus Calmette Guerin immunized people is due to training of innate immunity. Evidence to support the hypothesis is a systematic review, which showed that BCG protects against M. tuberculosis infection as evident from negative interferon gamma release assay results in BCG immunised exposed people. BCG has been shown to enhance innate immunity in monocytes via nucleotide binding oligomerisation domain 2 receptor activation by muramyldipeptide. An alternative hypothesis may be that T-suppressor cells induced by BCG immunisation may be the reason for the absence of an interferon gamma response mimicking absence of infection in immunized people. In order to test the primary hypothesis an ultra-low dose mouse model of M. tuberculosis infection could be used. Innate immunity could be enhanced by administration of murabutide and groups with and without murabutide enhanced BCG immunisation and with and without elimination of T-suppressor cells compared. The contribution of training of innate immunity in reduction of infection could hereby be demonstrated by treatment of mice prior to immunisation with an inhibitor of epigenetic programming. Confirmation of the hypothesis could provide the foundation of a new approach to an improved vaccine against M. tuberculosis infection.