Loss of Receptor on Tuberculin-Reactive T-Cells Marks Active Pulmonary Tuberculosis

Abstract

BackgroundTuberculin-specific T-cell responses have low diagnostic specificity in BCG vaccinated populations. While subunit-antigen (e.g. ESAT-6, CFP-10) based tests are useful for diagnosing latent tuberculosis infection, there is no reliable immunological test for active pulmonary tuberculosis. Notably, all existing immunological tuberculosis-tests are based on T-cell response size, whereas the diagnostic potential of T-cell response quality has never been explored. This includes surface marker expression and functionality of mycobacterial antigen specific T-cells.Methodology/Principal FindingsFlow-cytometry was used to examine over-night antigen-stimulated T-cells from tuberculosis patients and controls. Tuberculin and/or the relatively M. tuberculosis specific ESAT-6 protein were used as stimulants. A set of classic surface markers of T-cell naïve/memory differentiation was selected and IFN-γ production was used to identify T-cells recognizing these antigens. The percentage of tuberculin-specific T-helper-cells lacking the surface receptor CD27, a state associated with advanced differentiation, varied considerably between individuals (from less than 5% to more than 95%). Healthy BCG vaccinated individuals had significantly fewer CD27-negative tuberculin-reactive CD4 T-cells than patients with smear and/or culture positive pulmonary tuberculosis, discriminating these groups with high sensitivity and specificity, whereas individuals with latent tuberculosis infection exhibited levels in between.Conclusions/SignificanceSmear and/or culture positive pulmonary tuberculosis can be diagnosed by a rapid and reliable immunological test based on the distribution of CD27 expression on peripheral blood tuberculin specific T-cells. This test works very well even in a BCG vaccinated population. It is simple and will be of great utility in situations where sputum specimens are difficult to obtain or sputum-smear is negative. It will also help avoid unnecessary hospitalization and patient isolation.

Active tuberculosis is characterized by an antigen specific and strictly localized expansion of effector T cells at the site of infection

“…Sensitivity and specificity in this small sample size both reached 100%, backing the recently reported findings on the diagnostic value of PPDspecific T cells in patients with active TB [9]. Expression, or rather the loss of CD27 on the surface of peripheral PPD-specific T cells, has been demonstrated to have excellent sensitivity and specificity for the diagnosis of active TB [9]. However, and in contrast to the approach suggested by our study, the identification of PPD-specific T cells requires overnight incubation and intracellular staining of cytokines.…”

“…3A; the loss of CD27 on the surface of peripheral PPD-specific T cells, has been demonstrated to have excellent sensitivity and specificity for the diagnosis of active TB [9]. However, and in contrast to the approach suggested by our study, the identification of PPD-specific T cells requires overnight incubation and intracellular staining of cytokines.…”

“…Group differences were assessed using the Mann-Whitney U-test. 9.96-69.3% in non-TB patients; p = 0.83) were not significant between the patient groups ( Fig. 1).…”

Flow cytometric measurements of TB‐specific T cells comparing with QuantiFERON‐TB gold

“…This may be due to the fact that one of the two MTB antigens tended to evoke a much larger response than the other, although both were determined to be positive. ESAT-6 reactivity is known to be higher in latent TB than in active TB (11,19,20). Regarding Target cell count, regardless of two MTB antigens in the TB group, the QFTþ TB subgroup (N ¼ 22 Â 2 ¼ 44) was significantly higher than the QFTÀ TB subgroup (N ¼ 14 Â 2 ¼ 28) (median 39.8, 14.8, respectively, P ¼ 0.015, unpaired t-test).…”

“…The ICCFC has the advantage of identifying the composition of the secreting cells to reference populations of peripheral blood (2,6,(9)(10)(11)(12)(13)(14), bronchoalveolar lavage fluid (9,15), or induced sputum (16) using polychromatic immunophenotyping. Despite the obvious advantage of diagnostic accuracy, studies comparing ICCFC with two other methodologies have not yet been performed (7), with the exception of two recent reports, one with QFT (14), and the other with ELISpot (16).…”