Additional work showed that the Mtb DosR-regulon-encoded antigen Rv2628 was strongly recognized by individuals with remote Mtb infection 13, 14. Thus far, the precise mechanisms and T-cell subsets responsible for the responses against Mtb DosR-regulon-encoded antigens have not been studied in detail; and virtually all studies have relied on measuring IFN-γ production by polyclonal
cells. Here, we report peptide reactivity and memory phenotypes of Mtb selleck compound DosR-regulon-encoded antigen-specific T cells in long-term LTBI, and moreover, document a large series of specific peptide epitopes recognized by specific CD4+ and CD8+ T cells. Three Mtb DosR antigens, Rv1733c, Rv2029c and Rv2031c (HspX, α-crystallin) were tested in this study. Strong Mtb DosR antigen-specific CD4+ and CD8+ polyfunctional T-cell responses were detected Rapamycin nmr in ltLTBIs. The highest responses were observed among single cytokine-producing CD4+ and CD8+ T-cell subsets (either TNF-α+, IL-2+ or IFN-γ+, depending on the stimulus) followed by double producing CD4+ and particularly CD8+ T cells. Of interest, the most frequent
multiple cytokine-producing T cells were IFN-γ+TNF-α+ CD8+ T cells. These cells were further characterized as effector memory (CCR7− and CD45RA−) or effector (CCR7− and CD45RA+) T cells, which have the ability to perform immediate effector functions. This is compatible with an important role for CD8+ T cells in Mtb infection 37, 38. Mtb antigen-specific polyfunctional T cells have been studied intensely the last few years, both in vaccination and in observational studies in Mtb-infected individuals 18–29, 39. There is currently
no consensus whether polyfunctional T cells represent a marker of protective immunity or of disease activity. The vaccine MVA85A (recombinant replication-deficient cAMP vaccinia Ankara, expressing Ag85A) induced polyfunctional CD4+ and CD8+ T cells producing IFN-γ, TNF-α and IL-2 as well as IFN-γ and TNF-α in mice, which correlated with TB protection 19. This vaccine also induced increased CD4+ T cells expressing IFN-γ, TNF-α and IL-2 in humans when given as a booster to previous BCG vaccination 20, 21. Similar results were reported following human vaccination with the BCG booster AERAS-402 (recombinant replication-deficient Adenovirus (Ad35) virus, expressing a polyprotein of Ag85A, Ag85B and TB10.4) 22. Finally, mice vaccinated with hybrid subunit vaccines H1 (Ag85-ESAT6) and H56 (H1+Rv2660) also had high numbers of triple cytokine-producing CD4+ T cells 23, 24. However, observational studies in humans have associated polyfunctional CD4+ T cells with TB disease 25, 26.