Comparative immunogenicity of BCG substrains for mice

Area of Science:

• Immunology
• Microbiology
• Vaccinology

Background:

• Bacillus Calmette-Guérin (BCG) is a live attenuated strain of Mycobacterium bovis used as a vaccine against tuberculosis.
• Variations exist among BCG substrains, potentially impacting their immunogenicity and efficacy.
• Understanding substrain differences is crucial for optimizing tuberculosis prevention strategies.

Purpose of the Study:

• To evaluate and compare the immunogenicity of four BCG substrains (BCG Brazil, BCG Prague, BCG Russia, and BCG Glaxo) in a mouse model.
• To assess the impact of intravenous vaccination route on BCG immunogenicity.
• To determine differences in induced tuberculin hypersensitivity among the BCG substrains.

Main Methods:

• Mice were vaccinated intravenously with four BCG substrains.
• Immunogenicity was assessed by measuring pulmonary density and splenic, hepatic, and pulmonary indexes.
• Tuberculin sensitivity was determined by measuring the thickness of the skin on the inoculated leg.

Main Results:

• All four BCG substrains exhibited intermediate virulence between pathogenic and non-pathogenic mycobacteria, with no significant differences in pulmonary density.
• Reinoculation via the intravenous route led to a significant increase in organ size (except spleen) compared to the subcutaneous route.
• BCG Brazil induced the highest tuberculin hypersensitivity, followed by BCG Prague, while BCG Glaxo induced the weakest response, allowing differentiation between BCG Brazil and BCG Glaxo.

Conclusions:

• Significant variability exists in the immunogenicity of BCG substrains, with BCG Brazil being the most potent and BCG Glaxo the least potent.
• The intravenous vaccination route influences BCG-induced immune responses.
• These findings highlight the importance of selecting specific BCG substrains for enhanced vaccine efficacy in tuberculosis control.