A new study shows that the current tuberculosis vaccine induces protective immunity against nine strains of the bacteria in mice indicating that strain-specific resistance may be uncommon.
Tuberculosis (TB) is one of the world's most challenging infectious diseases to date and is responsible for approximately 2 million deaths per year. An attenuated vaccine incorporating Mycobacterium bovis BCG has been used for over 50 years, however, high mortality rates have persisted and researchers attribute multiple factors to its varying effectiveness including that the anti-TB protective immunity induced by the vaccine may be strain-specific.
W-Beijing lineage strains are among the most prominent associated with worldwide outbreaks of TB. In the study researchers investigated the strain specificity of Mycobacterium bovis BCG vaccine-induced antituberculosis protective immunity responses by inoculating mice with the vaccine and challenging them 2 months later with one of nine Mycobacterium tuberculosis strains, four from the W-Beijing lineage, four non-Beijing isolates, and one control.
Organ bacterial burdens and lung pathology were examined in vaccinated and naïve mice the day of infection as well as at 4, 12, and 20 weeks postchallenge. Four weeks following an aerosol challenge with each of the strains, results showed the bacterial growth in the lungs and spleens were much lower and lung pathology significantly improved in all vaccinated animals when compared to controls. Animals infected with six of the nine strains exhibited reduced organ bacterial burdens after 12 weeks and lung inflammation in all immunized animals was measurably lower at 20 weeks postchallenge.
"These data demonstrate that BCG vaccination protects against infection with diverse M. tuberculosis strains in the mouse model of pulmonary tuberculosis and suggest that strain-specific resistance to BCG-induced protective immunity may be uncommon," say the researchers.
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