Development of an Engineered Mycobacterium tuberculosis Strain for a Safe and Effective Tuberculosis Human Challenge...

Area of Science:

• Microbiology
• Vaccinology
• Genetic Engineering

Background:

• Human challenge experiments are crucial for accelerating tuberculosis (TB) vaccine development.
• A key requirement for TB challenge strains is the ability to replicate within the host and be reliably cleared post-infection.

Approach:

• Engineered Mycobacterium tuberculosis (Mtb) strains were developed with up to three orthogonal kill switches.
• These kill switches are tightly regulated by exogenous tetracyclines and trimethoprim, allowing for controlled replication and clearance.
• The engineered strains' immunogenicity and antibiotic susceptibility were assessed and compared to wild-type Mtb.

Key Points:

• Under permissive conditions, engineered Mtb strains exhibited similar immunogenicity and antibiotic susceptibility to wild-type Mtb.
• In the absence of regulatory compounds, the engineered strains demonstrated rapid clearance in axenic culture, mice, and nonhuman primates.
• A strain with three kill switches showed an exceptionally low escape rate (<10^-10 per genome per generation) and no relapse in a SCID mouse model.

Conclusions:

• The developed engineered Mtb strains with multiple kill switches represent a significant advancement for TB vaccine research.
• These strains offer a potentially safe and effective tool for human challenge models, facilitating faster TB vaccine development.
• The precise control over Mtb replication and clearance enhances the safety profile for experimental use.