EVOLUTION OF MYCOBACTERIUM TUBERCULOSIS AND IMPLICATIONS FOR VACCINE DEVELOPMENT.

Tuberculosis (TB) is a growing public health threat, particularly in the face of the global epidemics of multidrug resistance. Given the limited efficacy of the current TB vaccine and the recent clinical failure of the most advanced new TB vaccine candidate, novel concepts for vaccine design should be explored. Most T cell antigens in the human-adapted Mycobacterium tuberculosis complex (MTBC) are evolutionarily conserved and under strong purifying selection, indicating that host immune responses targeting these antigens might not be protective. By contrast, a few highly variable T cell epitopes have recently been discovered, which could serve as alternative vaccine antigens. Moreover, there is increasing evidence that the human-adapted MTBC has been co-evolving with the human host for a long time. Hence, studying the interaction between bacterial and human genetic diversity might help identify additional targets that could be exploited for TB vaccine development.