Engineered Mycobacterium tuberculosis triple-kill-switch strain provides controlled tuberculosis infection in animal models.

Human challenge experiments could accelerate tuberculosis vaccine development. This requires a safe Mycobacterium tuberculosis (Mtb) strain that can both replicate in the host and be reliably cleared. Here we genetically engineered Mtb strains encoding up to three kill switches: two mycobacteriophage lysin operons negatively regulated by tetracycline and a degron domain-NadE fusion, which induces ClpC1-dependent degradation of the essential enzyme NadE, negatively regulated by trimethoprim.