Resuscitation-promoting factors are expressed in Mycobacterium tuberculosis-infected human tissue.

Resuscitation-promoting factors are small proteins found in many high G+C Gram-positive organisms. In picomolar concentrations in vitro they promote the emergence from dormancy and shorten the lag phase of growth of small inocula of responsive bacteria. Mycobacterium tuberculosis has five rpf gene orthologues all of which are expressed during in vitro growth. Rpfs may play a role in dormancy or reactivation of tubercle bacilli in vivo, and could be a potential target for chemotherapeutic intervention: however it is not known whether they are expressed by M. tuberculosis in vivo in the context of human infection. The work presented here demonstrates that Rpf expression can be detected in human tissues infected with M. tuberculosis and describes the pattern of this expression using immunocytochemistry with anti-Rpf antibodies.