Multicolor flow cytometric analyses of CD4+ T cell responses to Mycobacterium tuberculosis-related latent antigens

Abstract

Although IFN-γ release assays (IγRAs) provide increased specificity over tuberculin skin tests, the early and sensitive detection of reactivation of latently infected Mycobacterium tuberculosis is required to control tuberculosis (TB). Recently, a multicolor flow cytometry has been developed to study CD4+ T cell cytokine responses (IFN-γ/IL-2/TNF-a) to purified protein derivatives (PPD) and M. tuberculosis-specific antigens (ESAT-6/CFP-10) and provided useful information regarding anti-TB immunity. However, the diagnostic relevancy remains uncertain. Here, we analyzed three additional CD4+ T cell cytokine responses (IL-10/IL-13/IL-17) to latent mycobacterial antigens (a-crystallin, methylated heparin-binding hemagglutinin [HBHA], and mycobacterial DNA-binding protein 1 [MDP-1]) as well as PPD and ESAT-6/CFP-10 in 12 IGRA+ TB cases and 8 healthy controls. No significant difference in IFN-γ response was observed between TB cases and controls, which was likely due to the high variation among the individuals. However, we found a significant increase over healthy controls in (i) the IL-2 response to HBHA in recovery stage TB cases, (ii) the number of M. tuberculosisspecific polyfunctional CD4+ T cells in on-treatment and recovery stage cases, and (iii) the IL-17 response to HBHA and MDP-1 in on-treatment and recovery stage cases. These results suggest that a combination of these T cell cytokine parameters could aid in accurate diagnosis of latent TB infection.