Ethnicity-tailored novel set of ESAT-6 peptides for differentiating active and latent tuberculosis

Utility of interferon gamma/tumor necrosis factor alpha FluoroSpot assay in differentiation between active tuberculosis and latent tuberculosis infection: a pilot study

Background

The differential diagnosis of active tuberculosis (ATB) and latent tuberculosis infection (LTBI) remains challenging in clinical practice. We aimed to evaluate the diagnostic accuracy of the IFN-γ/TNF-α FluoroSpot assay for differentiating ATB from LTBI.

Methods

We conducted a pilot study of case-control design, using the FluoroSpot assay to simultaneously detect IFN-γ and TNF-α secretion at the single-cell level. The frequencies of antigen-specific single TNF-α-, total TNF-α-, single IFN-γ-, total IFN-γ- and dual IFN-γ/TNF-α-secreting T cells were detected. The optimal cutoffs value of frequencies for differentiating ATB from LTBI were determined according to receiver operating characteristic curve analysis. The sensitivity, specificity, predictive values (PV) and likelihood ratios (LR) of the FluoroSpot assay were calculated.

Results

Thirty patients diagnosed microbiologically with ATB, 36 healthcare workers with LTBI and 36 healthy controls were enrolled. After stimulated by ESAT-6 or CFP-10 peptides, the median frequencies of single TNF-α-, total TNF-α-, single IFN-γ-, total IFN-γ- and dual IFN-γ/TNF-α-secreting T cells in ATB patients were all significantly higher than those in LTBI and HC groups (P < 0.01). The frequencies of total IFN-γ-secreting T cells detected by FluoroSpot assay correlated significantly with those of T-SPOT.TB (r = 0.910 for ESAT-6, P < 0.001, r = 0.845 for CFP-10, P < 0.001). After stimulated by ESAT-6 peptides, with total TNF-α-secreting T cells frequencies at a cut off value of 21 iSFCs/250,000 PBMCs, the sensitivity, specificity, PLR, NLR, PPV, NPV of IFN-γ/TNF-α FluoroSpot assay in differentiating ATB from LTBI were 96.7% (95%CI, 82.8–99.9%), 94.3% (95%CI, 80.8–99.3%), 16.92 (95%CI, 4.40–65.08), 0.04 (95%CI, 0.01–0.24), 93.6% (95%CI,78.6–99.2%) and 97.1% (95%CI, 84.7–99.9%), respectively. With the frequencies of total TNF-α- and total IFN-γ-secreting T cells stimulated by ESAT-6 peptides combined, the specificity was increased to 97.1%, and the positive likelihood ratio to 31.5. The combination with CFP-10 might not improve the diagnostic accuracy of the ESAT-6 for differentiating ATB from LTBI.

Conclusions

IFN-γ/TNF-α FluoroSpot assay might have potential to help differentiate ATB from LTBI, but the findings need to be further verified by cross-sectional or prospective cohort studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06351-w.

Cytokine biomarkers for the diagnosis of tuberculosis infection and disease in adults in a low prevalence setting

OBJECTIVE

Accurate and timely diagnosis of tuberculosis (TB) is essential to control the global pandemic. Currently available immunodiagnostic tests cannot discriminate between latent tuberculosis infection (LTBI) and active tuberculosis. This study aimed to determine whether candidate mycobacterial antigen-stimulated cytokine biomarkers can discriminate between TB-uninfected and TB-infected adults, and additionally between LTBI and active TB disease.

METHODS

193 adults were recruited, and categorised into four unambiguous diagnostic groups: microbiologically-proven active TB, LTBI, sick controls (non-TB lower respiratory tract infections) and healthy controls. Whole blood assays were used to determine mycobacterial antigen (CFP-10, ESAT-6, PPD)-stimulated cytokine (IL-1ra, IL-2, IL-10, IL-13, TNF-α, IFN-γ, IP-10 and MIP-1β) responses, measured by Luminex multiplex immunoassay.

RESULTS

The background-corrected mycobacterial antigen-stimulated cytokine responses of all eight cytokines were significantly higher in TB-infected participants compared with TB-uninfected individuals, with IL-2 showing the best performance characteristics. In addition, mycobacterial antigen-stimulated responses with IL-1ra, IL-10 and TNF-α were higher in participants with active TB compared those with LTBI, reaching statistical significance with PPD stimulation, although there was a degree of overlap between the two groups.

CONCLUSION

Mycobacterial antigen-stimulated cytokine responses may prove useful in future immunodiagnostic tests to discriminate between tuberculosis-infected and tuberculosis-uninfected individual, and potentially between LTBI and active tuberculosis.

Improving T-cell assays for diagnosis of latent TB infection: Confirmation of the potential role of testing Interleukin-2 release in Iranian patients

BACKGROUND

Since gamma interferon release assays (IGRAs) cannot differentiate between active tuberculosis and latent tuberculosis infection (LTBI), development of rapid and specific diagnosis tools are essential for discriminating between active tuberculosis (TB) from LTBI. Both IGRAs are based on Mycobacterium tuberculosis-specific antigens, namely, early secretory antigenic target 6 (ESAT-6) and 10kDa culture filtrate (CFP-10). The aim of this study was to evaluate the potential value of IL-2 secretion by whole blood cells after stimulation with rESAT-6 and rCFP-10 for discriminating between active and latent tuberculosis.

METHODS

Interleukin-2 and IFN-γ were measured after blood stimulation of 90 cases (30 with active TB, 30 with LTBI and 30 healthy controls) with recombinant ESAT-6 and CFP-10. Receiver operating characteristic (ROC) curve analysis was conducted to determine the best IL-2 and IFN-γ result thresholds in discriminating between cases with active or latent TB, and the corresponding sensitivity and specificity were recorded.

RESULTS

The IFN-γ release assay demonstrated a good sensitivity and specificity (sensitivity 83-84% and specificity 92%) for diagnosis of tuberculosis. The discrimination performance of IL-2 assay (assessed by the area under ROC curve) between LTBI and patients with active TB were 0.75 and 0.8 following stimulation with rESAT-6 and rCFP-10, respectively. Maximum discrimination was reached at a cut-off of 11.6pg/mL for IL-2 after stimulation with recombinant rESAT-6 with 72% sensitivity and 79% specificity and 10.7pg/mL for IL-2 following stimulation with rCFP-10 with 75% sensitivity and 79% specificity, respectively.

CONCLUSION

This study demonstrates that rESAT-6 and rCFP-10 can provide a sensitive and specific diagnosis of TB. In addition, it was shown that IL-2 may be serving as a marker for discriminating LTBI and active TB.

PpiA antigen specific immune response is a potential biomarker for latent tuberculosis infection

One third of the world's population is estimated to harbour latent tuberculosis infection (LTBI). Around 10% of them have the life time risk of developing active tuberculosis (PTB). Currently there is no gold standard test for identifying LTBI. Therefore identification of specific markers for LTBI will help as to develop a test specific for LTBI. Earlier, in our immunoproteomic analysis, we found that peptidyl-prolyl cis-trans isomerase A (PpiA) protein-containing fractions induced significantly higher interferon-gamma (IFN-γ) response in LTBI than in PTB. Immunological characterisation of recombinant PpiA protein was carried out in the current study. We have studied 10 cytokines and 2 chemokine responses against PpiA and standard antigens such as early secretory antigenic target-6 (ESAT-6) and culture filtrate antigen-10 (CFP-10). In healthy household contacts (HHC), all the tested antigens induced significantly higher levels of IFN-γ and Interlukin-8 (IL-8) compared with those in PTB. PpiA-specific IL-12p40 response was significantly increased in HHC compared with that in PTB. PpiA antigen-specific IFN-γ and IL-12p40 both showed 86% positivity in HHC, whereas in PTB, they showed 20% and 38% positivity, respectively. In terms of IFN-γ/TNF-α ratio, PpiA displayed 86% (30/35) positivity in HHC and 18% (7/39) positivity in PTB. In summary we found that PpiA-specific IFN-γ and IFN-γ/TNF-α ratio response were specific biomarkers for LTBI identification.