Overexpression of heat-shock proteins reduces survival of Mycobacterium tuberculosis in the chronic phase of infection

Elevated expression of heat-shock proteins (HSPs) can benefit a microbial p athogen struggling to penetrate host defenses during infection, but at the same time might provide a crucial signal alerting the host immune system to its presence. To determine which of these effects predominate, we construc ted a mutant strain of Mycobacterium tuberculosis that constitutively overe xpresses Hsp70 proteins. Although the mutant was fully virulent in the init ial stage of infection, it was significantly impaired in its ability to per sist during the subsequent chronic phase. Induction of microbial genes enco ding HSPs might provide a novel strategy to boost the immune response of in dividuals with latent tuberculosis infection.