"One third of the world's population is infected with latent TB, which therefore constitutes the largest reservoir for TB. In 5% of latently infected individuals TB will eventually re-activate, and it is believed that most new TB cases is indeed due to re-activation of latent TB. TB is a chronic disease, and during the long interaction with the host, the immune response against TB antigens tend to focus on only a few dominant epitopes. The idea for the project is that while a response against the dominant epitopes will lead to partial protection, it is not enough to eradicate M.tb resulting in a lifelong latent infection. Moreover, a response against dominant epitopes will wane with time resulting in re-activation of TB, and spreading of the disease. As a consequence, an immune response against only dominant epitopes within M.tb antigens is not enough to fully control the infection and stop the spread of the disease.Recently is has become increasingly clear that concerning chronic diseases, responses against subdominant epitopes, not induced by the natural infection, can be highly protective (1), and our working hypothesis is therefore the following: To increase the control over a chronic persisting M.tb infection (and prevent re-activation of TB), a response against the subdominant epitopes is required.To examine this we intend to test the vaccine efficacy of both dominant epitopes (epitopes induced by the natural infection) and sub-dominant epitopes (epitopes not induced by the natural infection) given post exposure to animals harbouring a persistent infection."