Extended safety studies of the attenuated live tuberculosis vaccine SO2 based on phoP mutant

Area of Science:

• Vaccinology
• Microbiology
• Immunology

Background:

• Live attenuated vaccines require rigorous safety and stability assessments.
• The Mycobacterium tuberculosis phoP mutant strain SO2 is a promising candidate for a tuberculosis vaccine.
• Assessing the genetic stability and safety profile of vaccine candidates is crucial before clinical trials.

Purpose of the Study:

• To evaluate the genetic stability of the phoP mutation in the SO2 tuberculosis vaccine candidate.
• To assess the safety and attenuation of the SO2 strain in relevant animal models.
• To determine the drug sensitivity profile of the SO2 strain.

Main Methods:

• Sub-culturing the SO2 strain for 6 months in vitro and infecting SCID mice for 3 months to test mutation stability.
• Administering a high dose of SO2 (2.5x10^6 CFUs) to guinea pigs and monitoring for 6 months.
• Conducting post-exposure toxicity studies in guinea pigs and mice infected with M. tuberculosis.

Main Results:

• No reversion of the phoP mutation was observed in vitro or in vivo.
• SO2 demonstrated full sensitivity to four major first-line anti-tuberculosis drugs.
• All animals survived SO2 inoculation, with no histological lesions or toxicity, confirming full attenuation.

Conclusions:

• The SO2 vaccine candidate exhibits excellent genetic stability.
• SO2 possesses a robust safety profile, demonstrating full attenuation and no adverse effects in animal models.
• These findings support the advancement of the SO2 tuberculosis vaccine candidate into clinical trials.