Expression of katG in Mycobacterium tuberculosis is associated with its growth and persistence in mice and guinea pigs
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1Laboratory of Mycobacteria, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland, USA.
Abstract:
The molecular mechanisms associated with the pathogenesis of tuberculosis are not well understood. The present study evaluated the role of catalase-peroxidase as a potential virulence factor for Mycobacterium tuberculosis. Growth and persistence of M. tuberculosis H37Rv in intravenously infected BALB/ c mice were compared with katG-deleted, isoniazid-resistant M. tuberculosis H37RVINHR. Transformation of M. tuberculosis H37Rv (TBkatG) or Mycobacterium intracellulare (MACkatG) genes into M. tuberculosis H37RvINHR restored its catalase-peroxidase activities and the ability of the recombinants to persist in spleens of mice and guinea pigs. Transformation with the TBkatG gene with the codon 463 R-->L mutation also restored catalase-peroxidase activity and enhanced persistence. However, transformants with the codon 275 T-->P mutant expressed low levels of enzymatic activity and failed to persist in guinea pig spleen, although they did survive in mouse tissues. These results indicate that KatG contributes to the ability of M. tuberculosis to grow and survive within the infected host tissues.
Insights
Mycobacterium tuberculosis KatG (catalase-peroxidase) is crucial for virulence. Restoring KatG activity in mutant strains improved their ability to survive and persist in host tissues, highlighting its role in tuberculosis pathogenesis.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Tuberculosis pathogenesis mechanisms remain incompletely understood.
- The role of specific virulence factors in Mycobacterium tuberculosis survival is under investigation.
Purpose of the Study:
- To evaluate the contribution of catalase-peroxidase (KatG) to the virulence of Mycobacterium tuberculosis.
- To investigate the impact of KatG activity on M. tuberculosis persistence in host tissues.
Main Methods:
- Comparison of M. tuberculosis H37Rv wild-type and katG-deleted strains in mouse infection models.
- Complementation of katG-deleted strains with wild-type or mutant KatG genes.
- Assessment of bacterial growth and persistence in mouse and guinea pig spleens.
Main Results:
- Deletion of the katG gene impaired M. tuberculosis persistence in host tissues.
- Restoration of catalase-peroxidase activity via gene transformation re-established bacterial persistence.
- Specific KatG mutations differentially affected enzymatic activity and in vivo survival.
Conclusions:
- KatG is a significant virulence factor for Mycobacterium tuberculosis.
- Catalase-peroxidase activity is essential for M. tuberculosis to effectively grow and survive within host tissues during infection.
