Vaccine https://doi.org/10.1016/j.vaccine.2019.11.060 (2019)
Since its first use in humans in 1921, the live attenuated tuberculosis vaccine bacille Calmette-Guérin (BCG) has been propagated under different conditions, which has led to the appearance of genetically distinct strains. In Vaccine, Levy and colleagues systematically compare five licensed BCG formulations to gain insights into the biological differences among these strains. The five formulations differ significantly in their in vitro viability, growth characteristics and RNA content when cultured under identical conditions. For example, BCG-India and BCG-Bulgaria show slower growth and are also more affected by changes in the culture media. BCG formulations also exhibit differences in their ability to stimulate immune responses, with BCG-India in particular being relatively poor at eliciting interferon-γ — a cytokine critical for effective antituberculosis responses. These findings highlight the need to consider BCG strain formulations in both clinical and laboratory contexts.