Recombinant BCG to Enhance Its Immunomodulatory Activities

Area of Science:

• Microbiology
• Immunology
• Vaccinology

Background:

• Bacillus Calmette-Guérin (BCG), an attenuated Mycobacterium bovis, is a century-old tuberculosis vaccine with additional therapeutic applications in cancer and inflammatory diseases.
• The efficacy of BCG is imperfect, prompting research into genetic modifications to improve its protective and therapeutic capabilities.
• Recombinant BCG strains have been developed to express immune-modulatory molecules, aiming to enhance immune responses against tuberculosis and other conditions.

Purpose of the Study:

• To review molecular engineering strategies employed over the past three decades to enhance the immune-modulatory potential of BCG.
• To summarize the development and testing of recombinant BCG strains for improved efficacy against tuberculosis, cancer, and inflammatory diseases.
• To highlight the current limitations and future directions in recombinant BCG research, particularly the need for studies beyond mouse models.

Main Methods:

• Genetic modification of BCG to express various immune-modulatory molecules, including cytokines and bacterial toxins.
• Deletion of BCG genes responsible for immune-suppressive properties to modulate innate and adaptive immune responses.
• In vivo testing of genetically modified BCG strains in mouse models for protection against tuberculosis and therapeutic effects in cancer and allergies.

Main Results:

• Recombinant BCG strains have demonstrated potential for improved protection against tuberculosis and enhanced therapeutic efficacy in various cancer models.
• Genetic modifications have shown effects on BCG-induced innate and adaptive immune responses, particularly T cell responses.
• Studies have explored the use of cytokines, bacterial toxins, and other molecules in engineered BCG to boost immune responses.

Conclusions:

• Molecular engineering offers a promising avenue to enhance the immunomodulatory potential and therapeutic efficacy of BCG.
• While promising results have been observed in preclinical studies (primarily mouse models), further research is needed to translate these findings to human applications.
• The development of genetically modified BCG strains, including one in late-stage clinical trials for tuberculosis, underscores the ongoing efforts to improve BCG-based therapies.