Abstract Text: Overreliance on studies of a few immunodominant M. tuberculosis (Mtb) antigens (out of > 4,000 proteins) is a bottleneck to identification of protective antigens/epitopes against tuberculosis. We stimulated PBMC from recently exposed, QFT+ HIV negative human adults with distinct Mtb antigens; four immunodominant antigens (classical); ESAT-6, PPE18, PPE46, and EspI, and four novel antigens (antigens with T cell epitope sequence variation demonstrating evidence of evolutionary diversifying selection); RimJ, Rv0012, Rv0010c and LldD2, and assessed CD4 T cell differentiation and functionality by intracellular cytokine staining for IFN-g, TNF-α, IL17, and GM-CSF. We discovered that CD4 T cell responses to distinct Mtb antigens are highly variable but, unexpectedly, classical antigens induce predominant Th1 while novel antigens elicit predominant Th17 cell responses. Specifically, the novel antigens responses are characterized by IL17 production, expression of RORgT, and CCR6, while classical antigens exhibit IFN-g production, expression of T-bet, and CXCR3. Whereas IL17 and IFN-g responses are enriched in novel and classical antigens respectively, TNF-a and GMCSF responses are prevalent in both classes of antigens. Additional analysis revealed that CD4 T cells that respond to Mtb antigens by producing IFN-g are predominantly central memory, while cells that produce IL17 in response to the same antigens are evenly distributed in effector and central memory phenotypes. In contrast, Staphylococcus Enterotoxin B (SEB)-responsive IFN-g and IL17 cells are predominantly effector memory. Studies to determine whether these differences in CD4 T cell responses determine the outcome of Mtb infection, progression to active TB disease or non-progression are ongoing.
