QuantiFERON-TB performance enhanced by novel Mycobacterium tuberculosis-specific antigens

Comparison of QuantiFERON-TB Gold In-Tube and QuantiFERON-TB Gold-Plus in the Diagnosis of Mycobacterium tuberculosis Infections in Immunocompromised Patients: a Real-World Study

QuantiFERON-TB Gold Plus (QFT-Plus) is an emerging QuantiFERON test after QuantiFERON-TB Gold In-Tube (QFT-GIT) for tuberculosis infection detection; it is an IFN-γ release assay. We compared QFTPlus, which has an additional TB antigen 2 (TB2) tube to induce cell-mediated (CD8⁺ T cell) immune responses, with QFT-GIT. We conducted this study to assess the agreement of the QFT-GIT and QFT-Plus assays in immunocompromised patients in a clinical setting. A total of 278 immunocompromised patients and 175 immunocompetent patients from different departments were continuously enrolled from August 2020 to March 2021, and each patient underwent both tests. Correlations between QFT-GIT and QFT-Plus assays showed good agreement (κ value = 0.859). Patients receiving long-term immunosuppressant therapy had the lowest concordance between QFT-GIT and QFT-Plus assays; 9 out of 11 positive latent tuberculosis infection (LTBI) cases were diagnosed by the QFT-Plus assay, implying that QFT-Plus may detect more LTBI than QFT-GIT does in these patients. Indeterminate results were associated with lower lymphocyte, CD4⁺ T cell, and CD8⁺ T cell absolute counts, and with lower CD4/CD8 ratios. In conclusion, we found that the QFT-GIT and QFT-Plus assays had high agreement not only in immunocompetent patients but also in immunocompromised patients. QFT-Plus may detect more LTBI than QFT-GIT in patients receiving long-term immunosuppressant therapy. Thresholds were established for lymphocyte absolute counts of >1.15 × 10⁹ cells, and for CD4⁺ T cell absolute counts of >467.7 × 10⁶ to 478.5 × 10⁶ cells, which may lessen the incidence of indeterminate results.

IMPORTANCE This study evaluated the performance of QFT-GIT and QFT-Plus in the diagnosis of M. tuberculosis infection in immunocompromised patients and found that QFT-Plus may detect more LTBI than QFT-GIT does in patients receiving long-term immunosuppressant therapy. We believe that our study makes a significant contribution to the literature because it highlights the different diagnostic accuracies of QFT-GIT and QFT-Plus in different subpopulations of immunocompromised and immunocompetent patients. Selecting a test with better performance, particularly in patients with a high risk of developing active TB, may assist the health sector in better managing TB. Furthermore, we believe that this study will be of significance to the diagnosis of LTBI.

Secreted Rv1768 From RD14 of Mycobacterium tuberculosis Activates Macrophages and Induces a Strong IFN-γ-Releasing of CD4+ T Cells

As the first line defensive mediators against Mycobacterium tuberculosis (M.tb) infection, macrophages can be modulated by M.tb to influence innate and adaptive immunity. Recently, we have identified several potential immunodominant T-cell antigens from the region of deletion (RD) of M.tb H37Rv, including Rv1768 from RD14. In this study, we further determined that Rv1768 was highly conserved among virulent M.tb strains and mainly distributed as a secreted protein. Exposure to recombinant purified Rv1768 (rRv1768) induced apoptosis of bone marrow derived macrophages (BMDMs) but showed no dose-dependent manner. Regarding macrophage activation, significant higher levels of iNOS and pro-inflammatory cytokines (like IL-6 and TNF-α) were detected in rRv1768-challenged BMDMs, whereas arginase 1 (Arg1) expression was markedly decreased. Meanwhile, MHC-II expression and antigen presentation activity of BMDMs were also enhanced by rRv1768 stimulation, leading to significantly increased IFN-γ expression of CD4⁺ T cells isolated from H37Rv-infected mice. It is worthy to note that Rv1768-induced IFN-γ production of peripheral blood mononuclear cells (PBMCs) and Rv1768-specific immunoglobulins was specifically observed in H37Rv-infected mice, but not BCG-infected or normal mice. Analysis of clinical blood samples further revealed that Rv1768 had a higher sensitivity and specificity (91.38 and 96.83%) for tuberculosis diagnosis than the results obtained from clinical CFP10 and ESAT6 peptides (CE)-based enzyme-linked immunospot (ELISPOT) assay. The area under ROC curve of Rv1768 was 0.9618 (95% CI: 0.919–1.000) when cutoff value set as 7 spots. In addition, Rv1768-specific IgG and IgM also exhibited moderate diagnostic performance for tuberculosis compared with CE specific antibodies. Our data suggest that Rv1768 is an antigen that strongly activates macrophages and has potential to serve as a novel ELISPOT-based TB diagnostic agent.

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.

Current use and acceptability of novel diagnostic tests for active tuberculosis: a worldwide survey

OBJECTIVE

To determine the current use and potential acceptance (by tuberculosis experts worldwide) of novel rapid tests for the diagnosis of tuberculosis that are in line with World Health Organization target product profiles.

METHODS

A multilingual survey was disseminated online between July and November of 2016.

RESULTS

A total of 723 individuals from 114 countries responded to the survey. Smear microscopy was the most commonly used rapid tuberculosis test (available to 90.9% of the respondents), followed by molecular assays (available to 70.7%). Only a small proportion of the respondents in middle- and low-income countries had access to interferon-gamma-release assays. Serological and lateral flow immunoassays were used by more than a quarter (25.4%) of the respondents. Among the respondents who had access to molecular tests, 46.7% were using the Xpert assay overall, that proportion being higher in lower middle-income countries (55.6%) and low-income countries (76.6%). The data also suggest that there was some alignment of pricing for molecular assays. Respondents stated they would accept novel rapid tuberculosis tests if available, including molecular assays (acceptable to 86.0%) or biomarker-based serological assays (acceptable to 81.7%). Simple biomarker-based assays were more commonly deemed acceptable in middle- and low-income countries.

CONCLUSIONS

Second-generation molecular assays have become more widely available in high- and low-resource settings. However, the development of novel rapid tuberculosis tests continues to be considered important by tuberculosis experts. Our data also underscore the need for additional training and education of end users.

First characterization of the CD4 and CD8 T-cell responses to QuantiFERON-TB Plus

INTRODUCTION

QuantiFERON^®-TB Gold Plus (QFT-Plus) is the new generation of QuantiFERON-TB Gold In-Tube test to identify latent tuberculosis infection (LTBI). QFT-Plus includes TB1 and TB2 tubes which contain selected Mycobacterium tuberculosis (Mtb) peptides designed to stimulate both CD4 and CD8 T-cells. Aim of this study is the flow cytometric characterization of the specific CD4 and CD8 T-cell responses to Mtb antigens contained within QFT-Plus.

METHODS

We enrolled 27 active tuberculosis (TB) patients and 30 LTBI individuals. Following stimulation with TB1 and TB2, antigen-specific T-cells were characterized by flow cytometry. Data were also correlated with the grade of TB severity.

RESULTS

TB1 mainly elicited a CD4 T-cell response while TB2 induced both CD4 and CD8 responses. Moreover, the TB2-specific CD4 response was detected for both active TB and LTBI patients, whereas the TB2-specific CD8 response was primarily associated with active TB (p = 0.01).

CONCLUSIONS

To our knowledge, we report the first characterization of the CD4 and CD8 T-cell response to QFT-Plus. CD8 T-cell response is mainly due to TB2 stimulation which is largely associated to active TB. These results provide a better knowledge on the use of this assay.

The best of respiratory infections from the 2015 European Respiratory Society International Congress

The breadth and quality of scientific presentations on clinical and translational research into respiratory infections at the 2015 European Respiratory Society (ERS) International Congress in Amsterdam, the Netherlands, establishes this area as one of the leadings fields in pulmonology. The host-pathogen relationship in chronic obstructive pulmonary disease, and the impact of comorbidities and chronic treatment on clinical outcomes in patients with pneumonia were studied. Various communications were dedicated to bronchiectasis and, in particular, to different prognostic and clinical aspects of this disease, including chronic infection with Pseudomonas and inhaled antibiotic therapy. Recent data from the World Health Organization showed that Europe has the highest number of multidrug-resistant tuberculosis cases and the poorest countries have the least access to suitable treatments. Latent tuberculosis and different screening programmes were also discussed with particular attention to risk factors such as HIV infection and diabetes. Several biomarkers were proposed to distinguish between active tuberculosis and latent infection. Major treatment trials were discussed (REMOX, RIFQUIN and STREAM). The possibility of once-weekly treatment in the continuation phase (RIAQUIN) was especially exciting. The continuing rise of Mycobacterium abscessus as a significant pathogen was noted. This article reviews some of the best contributions from the Respiratory Infections Assembly to the 2015 ERS International Congress.