Multifunctional CD4+T cells correlate with active Mycobacterium tuberculosis infection

Th1 CD4+T cells and their derived cytokines are crucial for protection against Mycobacterium tuberculosis. Using multiparametric flow cytometry, we have evaluated the distribution of seven distinct functional states (IFN-gamma/IL-2/TNF-alpha triple expressors, IFN-gamma/IL-2, IFN-gamma/TNF-alpha or TNF-alpha/IL-2 double expressors or IFN-gamma, IL-2 or TNF-alpha single expressors) of CD4+T cells in individuals with latent (LTBI) and active (TB) tuberculosis. We found that triple expressors, while detectable in 85-90%TB patients, were only present in 10-15% of LTBI subjects. In contrast, LTBI subjects had significantly higher (12- to 15-fold) proportions of IL-2/IFN-gamma double and IFN-gamma single expressors as compared with the other CD4+T cell subsets. Proportions of the other double or single CD4+T cell expressors did not differ between TB and LTBI subjects. These distinct IFN-gamma, IL-2 and TNF-alpha profiles of Mycobacterium tuberculosis-specific CD4+T cells seem to be associated with live bacterial loads, as indicated by the decrease in frequency of multifunctional T cells in TB patients after completion of anti-mycobacterial therapy. Our results suggest that phenotypic and functional signatures of CD4+T cells may serve as immunological correlates of protection and curative host responses, and be a useful tool to monitor the efficacy of anti-mycobacterial therapy