Differential expression of mycobacterial proteins following phagocytosis by macrophages

Mycobacterium tuberculosis resides within the macrophages of the host, but the molecular and cellular mechanisms of survival are poorly understood. Re cent evidence suggests that the attenuated vaccine strain Mycobacterium bov is BCG is both a deletion and regulatory mutant, yet retains both its immun oprotective and intra-macrophage survival potential. In an attempt to defin e M. bovis BCG genes expressed during interaction with macrophages, the pat terns of protein synthesis were examined by both one- and two-dimensional g el electrophoresis of BCC while inside the human leukaemic macrophage cell line THP-1. This study demonstrated that BCC expresses proteins while resid ent inside macrophages that are not expressed during in vitro growth in cul ture media or under conditions of heat shock. Western blotting analysis rev ealed that some of the differentially expressed proteins are specifically r ecognized by human M, tuberculosis-infected sera. Proteome analysis by two- dimensional electrophoresis and MS identified six abundant proteins that sh owed increased expression inside macrophages: 16 kDa a-crystallin (HspX), G roEL-1 and GroEL-2, a 31.7 kDa hypothetical protein (Rv2623), InhA and elon gation factor Tu (Tuf), Identification of proteins by such a strategy will help elucidate the molecular basis of the attenuation and the vaccine poten tial of BCG, and may provide antigens that distinguish infection with M, tu berculosis from vaccination with BCG.