The present invention relates in a first aspect to isolated sigma factor C(SigC) of bacteria, in particular, of mycobacteria for use in a pharmaceutical composition, e.g., for use in a prophylactic or therapeutic vaccine. The present invention provides the use of SigC of bacteria, in particular, of mycobacteria for use in a prime-boost-vaccination strategy, e.g. as a vaccine against Mycobacterium tuberculosis and other types of mycobacteria based diseases. In a further aspect, the present invention relates to pharmaceutical compositions containing SigC whereby said pharmaceutical composition is in form of a vaccine. Finally, methods for treating or preventing infections as well as for modulating or reducing innate immune responses are provided based on administration of Sig C.
