标题：The primary mechanism of attenuation of bacillus Calmette–Guérin is a loss of secreted lytic function required for invasion of lung interstitial tissue
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：21
页码：12420-12425
DOI：10.1073/pnas.1635213100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Tuberculosis remains a leading cause of death worldwide, despite the availability of effective chemotherapy and a vaccine. Bacillus Calmette-Guerin (BCG), the tuberculosis vaccine, is an attenuated mutant of Mycobacterium bovis that was isolated after serial subcultures, yet the functional basis for this attenuation has never been elucidated. A single region (RD1), which is absent in all BCG substrains, was deleted from virulent M. bovis and Mycobacterium tuberculosis strains, and the resulting {Delta}RD1 mutants were significantly attenuated for virulence in both immunocompromised and immunocompetent mice. The M. tuberculosis {Delta}RD1 mutants were also shown to protect mice against aerosol challenge, in a similar manner to BCG. Interestingly, the {Delta}RD1 mutants failed to cause cytolysis of pneumocytes, a phenotype that had been previously used to distinguish virulent M. tuberculosis from BCG. A specific transposon mutation, which disrupts the Rv3874 Rv3875 (cfp-10 esat-6) operon of RD1, also caused loss of the cytolytic phenotype in both pneumocytes and macrophages. This mutation resulted in the attenuation of virulence in mice, as the result of reduced tissue invasiveness. Moreover, specific deletion of each transcriptional unit of RD1 revealed that three independent transcriptional units are required for virulence, two of which are involved in the secretion of ESAT-6 (6-kDa early secretory antigenic target). We conclude that the primary attenuating mechanism of bacillus Calmette-Guerin is the loss of cytolytic activity mediated by secreted ESAT-6, which results in reduced tissue invasiveness.
