Rare Variable Antigens induce predominant Th17 responses in human infection.

CD4 T cells are essential for immunity to (), and emerging evidence indicates that IL-17-producing Th17 cells contribute to immunity to . While identifying protective T cell effector functions is important for TB vaccine design, T cell antigen specificity is also likely to be important. To identify antigens that induce protective immunity, we reasoned that as in other pathogens, effective immune recognition drives sequence diversity in individual antigens. We previously identified genes under evolutionary diversifying selection pressure whose products we term Rare Variable Mtb Antigens (RVMA). Here, in two distinct human cohorts with recent exposure to TB, we found that RVMA preferentially induce CD4 T cells that express RoRγt and produce IL-17, in contrast to 'classical' antigens that induce T cells that produce IFNγ. Our results suggest that RVMA can be valuable antigens in vaccines for those already infected with to amplify existing antigen-specific Th17 responses to prevent TB disease.