Dominant TNF-α+ Mycobacterium tuberculosis-specific CD4+ T cell responses discriminate between latent infection and active disease

Rapid diagnosis of active Mycobacterium tuberculosis (Mtb) infection remains a clinical and laboratory challenge. We have analyzed the cytokine profile (interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and interleukin-2 (IL-2)) of Mtb-specific T cells by polychromatic flow cytometry. We studied Mtb-specific CD4(+) T cell responses in subjects with latent Mtb infection and active tuberculosis disease. The results showed substantial increase in the proportion of single-positive TNF-alpha Mtb-specific CD4(+) T cells in subjects with active disease, and this parameter was the strongest predictor of diagnosis of active disease versus latent infection. We validated the use of this parameter in a cohort of 101 subjects with tuberculosis diagnosis unknown to the investigator. The sensitivity and specificity of the flow cytometry-based assay were 67% and 92%, respectively, the positive predictive value was 80% and the negative predictive value was 92.4%. Therefore, the proportion of single-positive TNF-alpha Mtb-specific CD4(+) T cells is a new tool for the rapid diagnosis of active tuberculosis disease.