Towards improved understanding of protective mechanisms induced by the BCG vaccine.

EVALUATION OF: Ryan AA, Nambiar JK, Wozniak TM et al. Antigen load governs the differential priming of CD8 T cells in response to the bacille Calmette-Guérin vaccine or Mycobacterium tuberculosis infection. J. Immunol. 182(11), 7172-7177 (2009). Mycobacterium tuberculosis is the causative agent of human TB, which is responsible for 26% of all preventable deaths in the developing world. Mycobacterium bovis bacillus Calmette-Guérin (BCG) has been used as a vaccine against TB since 1921, with protection varying from 0 to 80%. Although the reasons for this variability are unclear, protection is thought to be mediated by Th1-type responses. CD8(+) T cells have been shown to play a role in the response to mycobacteria. However, the nature of the CD8(+) response induced by BCG requires further characterization. In the paper being evaluated, it was shown that the antigenic load is important for the induction of CD8(+) T-cell responses and subsequent protective responses. Identification of the factors affecting induction of CD8(+) responses against mycobacteria will facilitate studies to characterize their nature and provide a platform for the development of systems seeking to improve on protection conferred by BCG.