Rapid detection of Mycobacterium tuberculosis infection by enumeration of antigen-specific T cells

Capturing Recent Mycobacterium tuberculosis Infection by Tuberculin Skin Test vs. Interferon-Gamma Release Assay

Reductions in tuberculosis (TB) incidence require identification of individuals at high risk of developing active disease, such as those with recent Mycobacterium tuberculosis (Mtb) infection. Using a prospective household contact (HHC) study in Kampala, Uganda, we diagnosed new Mtb infection using both the tuberculin skin test (TST) and interferon-gamma release assay (IGRA). Our study aimed to determine if the TST adds additional value to the characterization of IGRA converters. We identified 13 HHCs who only converted the IGRA (QFT-only converters), 39 HHCs who only converted their TST (TST-only converters), and 24 HHCs who converted both tests (QFT/TST converters). Univariate analysis revealed that TST-only converters were older. Additionally, increased odds of TST-only conversion were associated with older age (p = 0.02) and crowdedness (p = 0.025). QFT/TST converters had higher QFT quantitative values at conversion than QFT-only converters and a bigger change in TST quantitative values at conversion than TST-only converters. Collectively, these data indicate that TST conversion alone likely overestimates Mtb infection. Its correlation to older age suggests an "environmental" boosting response due to prolonged exposure to environmental mycobacteria. This result also suggests that QFT/TST conversion may be associated with a more robust immune response, which should be considered when planning vaccine studies.

Evaluation of the diagnostic efficacy of EC-Test for latent tuberculosis infection in ambulatory people with HIV

BACKGROUND

Latent tuberculosis infection (LTBI) co-infected with human immunodeficiency virus (HIV) is more likely to develop into active tuberculosis (ATB), recombinant Mycobacterium tuberculosis fusion protein ESAT6/CFP10 (EC-Test) is a latest developed method for LTBI. Compared with the interferon γ release test assays (IGRAs), the diagnostic performance of EC-Test to LTBI screening in HIV needs to be evaluated.

METHODS

A population-based multicenter prospective study was conducted in Guangxi Province, China. The baseline data was collected and LTBI were measured by QuantiFERON-TB Gold In-Tube (QFT-GIT), EC-Test and T-cell spot of the TB assay (T-SPOT.TB).

RESULTS

A total of 1478 patients were enrolled. when taking T-SPOT.TB as reference, the value of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and consistency that EC-Test to diagnosis LTBI in HIV was 40.42, 97.98, 85.26, 85.04 and 85.06% respectively; when taking QFT-GIT as reference, the value was 36.00, 92.57, 55.10, 85.09 and 81.13%, respectively. When the CD4 + cell count was <200 cells/μl, the accuracies of EC-Test to T-SPOT.TB and QFT-GIT were 87.12 and 88.89%, respectively; when it was 200 ≤ CD4 + ≤ 500 cells/μl, the accuracies of EC-Test was 86.20 and 83.18%, respectively; when the CD4 + cell count >500 cells/μl, the accuracies of EC-Test were 84.29 and 77.94%, respectively. The incidence of adverse reactions in EC-Test was 34.23% and the serious adverse reactions were 1.15%.

CONCLUSION

EC-Test has good consistency compared with IGRAs in detecting LTBI in HIV no matter in different immunosuppression status or different regions, and the safety of EC-Test is also well, suitable for LTBI screening in HIV in high prevalence settings.

Combined Detection of IFN-γ and Lymphocyte Subsets with Activation Indicators in the Clinical Application of Mycobacterium Tuberculosis Infection at Different Times

The immune status of mycobacterium tuberculosis (MTB) infection is essential for the diagnosis and treatment of this disease. In this work, we aim to evaluate the clinical significance of the combination of serum IFN-γ, IGRAs (Interferon-Gamma Release Assay), lymphocyte subset with activation indicators detection in active and latent tuberculosis infection patients. For this study, anticoagulant whole blood were collected from 45 active tuberculosis (AT group), 44 latent tuberculosis (LT group) and 32 healthy controls (HCs group). The serum IFN-γ and IGRAs detected by chemiluminescence, and the percentage of lymphocyte subsets and activated lymphocytes detected by flow cytometry. The results showed combined IGRAs, serum IFN-γ and NKT cells not only has good diagnostic efficiency for the AT, but also provides a laboratory diagnostic method to distinguish AT from LT. Activation indicator of CD3⁺HLA-DR⁺T and CD4⁺HLA-DR⁺T can effectively distinguish LT from HCs. While combined CD3⁺T, CD4⁺T, CD8⁺CD28⁺T, Treg and CD16⁺CD56⁺CD69⁺ cells can distinguish AT from HCs. This study showed combined direct detection of serum IFN-γ and IGRAs as well as lymphocyte subsets with activation indicators which may provide laboratory basis for the diagnosis and differential diagnosis of active and latent MTB infection.

From thymus to tissues and tumors: A review of T-cell biology

T cells are critical orchestrators of the adaptive immune response that optimally eliminate a specific pathogen. Aberrant T-cell development and function are implicated in a broad range of human disease including immunodeficiencies, autoimmune diseases, and allergic diseases. Accordingly, therapies targeting T cells and their effector cytokines have markedly improved the care of patients with immune dysregulatory diseases. Newer discoveries concerning T-cell-mediated antitumor immunity and T-cell exhaustion have further prompted development of highly effective and novel treatment modalities for malignancies, including checkpoint inhibitors and antigen-reactive T cells. Recent discoveries are also uncovering the depth and variability of T-cell phenotypes: while T cells have long been described using a subset-based classification system, next-generation sequencing technologies suggest an astounding degree of complexity and heterogeneity at the single-cell level.

Differential Diagnosis of Latent Tuberculosis Infection and Active Tuberculosis: A Key to a Successful Tuberculosis Control Strategy

As an ancient infectious disease, tuberculosis (TB) is still the leading cause of death from a single infectious agent worldwide. Latent TB infection (LTBI) has been recognized as the largest source of new TB cases and is one of the biggest obstacles to achieving the aim of the End TB Strategy. The latest data indicate that a considerable percentage of the population with LTBI and the lack of differential diagnosis between LTBI and active TB (aTB) may be potential reasons for the high TB morbidity and mortality in countries with high TB burdens. The tuberculin skin test (TST) has been used to diagnose TB for > 100 years, but it fails to distinguish patients with LTBI from those with aTB and people who have received Bacillus Calmette–Guérin vaccination. To overcome the limitations of TST, several new skin tests and interferon-gamma release assays have been developed, such as the Diaskintest, C-Tb skin test, EC-Test, and T-cell spot of the TB assay, QuantiFERON-TB Gold In-Tube, QuantiFERON-TB Gold-Plus, LIAISON QuantiFERON-TB Gold Plus test, and LIOFeron TB/LTBI. However, these methods cannot distinguish LTBI from aTB. To investigate the reasons why all these methods cannot distinguish LTBI from aTB, we have explained the concept and definition of LTBI and expounded on the immunological mechanism of LTBI in this review. In addition, we have outlined the research status, future directions, and challenges of LTBI differential diagnosis, including novel biomarkers derived from Mycobacterium tuberculosis and hosts, new models and algorithms, omics technologies, and microbiota.

Identification of CTL Epitopes on Efflux Pumps of the ATP-Binding Cassette and the Major Facilitator Superfamily of Mycobacterium tuberculosis

Tuberculosis is the world's most deadly infectious disease, with 10 million people falling ill and 1.5 million people dying from the disease every year. With the increasing number of drug-resistant Mycobacterium tuberculosis (MTB) strains and prevalence of coinfection of MTB with human immunodeficiency virus, many challenges remain in the prevention and treatment of tuberculosis. Therefore, the development of safe and effective tuberculosis vaccines is an urgent issue. In this study, we identified cytotoxic T lymphocyte epitopes on drug resistance-associated membrane protein efflux pumps of MTB, the ATP-binding cassette and the major facilitator superfamilies. First, three online software were used to predict HLA-A2-restricted epitopes. Then, the candidate epitopes were confirmed with the T2A2 cell binding affinity and peptide/MHC (pMHC) complex stability assays and in vitro immune activity experiments. Two drug-resistant T lymphocyte epitopes, designated Rv1218c-p24 and Rv2477c-p182, were selected, and their immunogenic activities studied in vivo in genetically engineered mice. The immune activities of these two epitopes were improved with the help of complete Freund's adjuvant (CFA). The epitopes identified here provide a foundation for the diagnosis and treatment of patients infected with drug resistant and the future development of a multiepitope vaccine.

CD4 response of QuantiFERON-TB Gold Plus for positive consistency of latent tuberculosis infection in patients on dialysis

A significantly negative reversion in the QuantiFERON-TB Gold In-tube (QFT-GIT) test is reported in patients on dialysis, which makes the results unreliable. The CD4 and CD8 responses of the QFT-Gold plus (QFT-Plus) may have better positive consistency, but this needs to be investigated. We enrolled dialysis patients with baseline positive QFT-GIT₀ results and conducted two rounds of follow-up paired QFT-GIT_1&2 and QFT-Plus_1&2 tests at an interval of 6 months. The positive consistency, concordance, and discordance of the QFT results were analyzed. A total of 236 patients on dialysis were screened, and 73 participants with positive QFT-GIT₀ results were enrolled. The baseline QFT-GIT₀ response was higher in the 1st QFT-Plus₁(+) group than in the QFT-Plus₁(-) group, but insignificantly different between the 1st QFT-GIT₁(+) and QFT-GIT₁(-) groups. The two assays had good correlation when concurrently tested. Fifty-three subjects completed a second round of the QFT-GIT₂ and QFT-Plus₂. Persistent positivity was higher with the QFT-Plus₂ (81.8%) than with the QFT-GIT₂ (58.8%, p = 0.040). The QFT-GIT₁ and QFT-Plus₁ CD4 responses were higher in patients with persistent positivity than in those with negative reversion, whereas the difference of the QFT-Plus TB1 and TB2 data, representative of the CD8 response, were similar between positive persistence and negative reversion. In conclusion, the QFT-Plus provides more reliable positive consistency than does the QFT-GIT. The CD4 interferon-γ response might play a role in maintaining positivity of LTBI.

Burden of Tuberculosis in South African Children During Treatment for Underlying Malignancies: A Single-center Experience in Johannesburg

BACKGROUND

Children with cancer are immunocompromised with increased susceptibility to infections. We evaluated the burden of tuberculosis in children with cancer.

METHODS

Children with cancer were enrolled and screened for Mycobacterium tuberculosis infection using the tuberculin skin test and enzyme-linked immune absorbent spot (T-SPOT.TB; Oxford Immunotec Ltd, Oxford, United Kingdom). Children with physician-suspected tuberculosis were investigated for M. tuberculosis using microscopy and culture on sputum or gastric washings.

RESULTS

We enrolled 169 children; 10.7% were living with HIV. The tuberculin skin test was positive in 2.9% of patients, who were treated for tuberculosis and excluded from further analysis. The enzyme-linked immune absorbent spot (T-SPOT.TB) was either negative or indeterminate in the first 100 children screened. The incidence of tuberculosis was 7.6 per 100 child-years; 35.3% were culture-confirmed. Tuberculosis was diagnosed at a mean of 5.5 months from cancer diagnosis. A greater proportion of children living with HIV (44.4%) developed tuberculosis than those without (17.2%; adjusted P = 0.042). Children treated for high-risk acute lymphoblastic leukemia, advanced stage non-Hodgkin lymphoma and acute myeloid leukemia (P = 0.009) and those with a higher exposure-period (per 100 child-years) to corticosteroids courses (350 vs. 29.4; P < 0.001) had a higher incidence of tuberculosis. Twenty-six of 34 children (76.5%) with tuberculosis died; multiple infections were identified at the time of death.

CONCLUSIONS

Screening children for tuberculosis infection at cancer diagnosis was of limited value. The high rate of tuberculosis and poor outcomes emphasize the need for a high index of suspicion to diagnose tuberculosis and consideration for antituberculosis treatment, especially for those with identified risk factors.

Comprehensive analysis of protein acetyltransferases of human pathogen Mycobacterium tuberculosis

Tuberculosis (TB), a leading infectious disease caused by Mycobacterium tuberculosis strain, takes four human lives every minute globally. Paucity of knowledge on M. tuberculosis virulence and antibiotic resistance is the major challenge for tuberculosis control. We have identified 47 acetyltransferases in the M. tuberculosis, which use diverse substrates including antibiotic, amino acids, and other chemical molecules. Through comparative analysis of the protein file of the virulent M. tuberculosis H37Rv strain and the avirulent M. tuberculosis H37Ra strain, we identified one acetyltransferase that shows significant variations with N-terminal deletion, possibly influencing its physicochemical properties. We also found that one acetyltransferase has three types of post-translation modifications (lysine acetylation, succinylation, and glutarylation). The genome context analysis showed that many acetyltransferases with their neighboring genes belong to one operon. By data mining from published transcriptional profiles of M. tuberculosis exposed to diverse treatments, we revealed that several acetyltransferases may be functional during M. tuberculosis infection. Insights obtained from the present study can potentially provide clues for developing novel TB therapeutic interventions.

Latent Tuberculosis Infection Increases in Kidney Transplantation Recipients Compared With Transplantation Candidates: A Neglected Perspective in Tuberculosis Control

Background

The prevalence and incidence of latent tuberculosis infection (LTBI) in patients with kidney transplantation remain unclear.

Methods

In this prospective study, we enrolled kidney transplantation candidates (KTCs) and recipients (KTRs) from 2014 to 2018. We defined LTBI as a positive result of QuantiFERON-TB Gold In-tube (QFT). We analyzed the predictors for LTBI acquisition and followed up on QFT assay test for 2 years among those initially without LTBI.

Results

Of 425 patients enrolled, 305 (71.8%) patients belonged to the KTC group and 120 (28.2%) to the KTR group. The initial QFT showed positive results in 32 (10.5%) and 24 (20.0%) patients in the KTC and KTR groups, respectively (P = .009). The QFT response value in patients with LTBI was higher in the KTR group than in the KTC group (1.85 vs 1.06 IU/mL, P = .046). Multivariate logistic regression showed that old age, absence of bacillus Calmette–Guérin (BCG) scar, presence of donor-specific antibody, and KTR group were independent factors for positive LTBI. For participants with initial negative QFT, positive QFT conversion within a 2-year follow-up was higher after kidney transplantation (20%) than in KTCs (5.5%) (P = .034).

Conclusions

This study is the first cohort to follow up LTBI status in patients with kidney transplantation and shows its higher prevalence and incidence in KTRs. It indicates that surveillance of LTBI after renal transplantation is important. In addition to status of kidney transplantation, old age, no BCG vaccination, and positive donor-specific antibody are also positive predictors for LTBI.

Elevated antigen-specific IFN-γ responses in bronchoalveolar lavage fluid impervious to clinical comorbidities improve the pulmonary tuberculosis diagnosis

The extremely slow growth rate of Mycobacterium tuberculosis (Mtb) challenges traditional methods for tuberculosis (TB) diagnosis. Here, we assessed the efficacy of a previously developed Mtb antigen-specific gamma interferon (IFN-γ) enzyme-linked immunospot (ELISPOT) performed on bronchoalveolar lavage fluid (BALF) from a cohort of 414 patients including 333 PTB patients (202/333 were sputum culture positive) for the diagnosis of PTB. We could confirm that antigen-specific IFN-γ-producing CD4⁺ T cells were concentrated significantly in BALF mononuclear cells (BALMC) compared with that in peripheral blood mononuclear cells (PBMC) assayed in parallel, but not those of CD8⁺ T cells both in sputum culture-negative and positive PTB. The magnitude of IFN-γ responses in the BALF was associated with bacterial load, and 9/202 of PTB with endobronchial TB (EBTB) were slightly reduced by the anti-TB treatment. Moreover, antigen-specific IFN-γ ELISPOT performed on BALMC showed higher sensitivity than PBMC ELISPOT. In addition, the differences of the BALMC ELISPOT between PTB and PTB with diabetes were not found, whereas PBMC IFN-γ responses were decreased in PTB with diabetes. Combined with the microbiological detection in BALF, such as microscopy and culture, the BALMC ELISPOT offers the opportunity for the more accurate diagnosis of PTB, especially those with clinical comorbidities.

Serial anti-tuberculous immune responses during the follow-up of patients with tuberculous pleurisy

Little is known about the decay kinetics of interferon (IFN)-γ response and its influencing factors in tuberculous pleurisy. We enrolled thirty-two patients with tuberculous pleurisy prospectively and followed up at month 0, 6, and 9, at which time peripheral venous blood was drawn for interferon gamma release assay (IGRA) by means of QuantiFERON-TB Gold In-Tube (QFT-GIT). Demographic and clinical data were captured. To identify significant predictive factors influencing the IFN-γ response, multiple linear regression analyses were performed. Percentage of CD4+, CD8+, Vγ2Vδ2 T cells and Treg cells were measured by flow cytometry. The percentage of QFT-GIT-positive patients at baseline, month 6 and month 9 were 96.9% (30/32), 90.6% (29/32) and 84.4% (27/32), respectively. Quantitative IFN-γ response at baseline were significantly correlated with symptom duration (P = .003, R = 0.261) and age (P = .041, R = 0.132). Besides, the decreases of the IFN-γ response at month 6 and month 9 were positively correlated with the IFN-γ level at baseline. The dynamic tendency of the percentages of Treg cells was similar to the IFN-γ responses at each time-point. Quantitative IFN-γ response could be influenced by host immune status, instead of disease burden and anti-tuberculosis treatment. IGRA is probably not a useful biomarker of treatment efficacy in tuberculous pleurisy.

ATBdiscrimination: An in Silico Tool for Identification of Active Tuberculosis Disease Based on Routine Blood Test and T-SPOT.TB Detection Results

Tuberculosis remains one of the deadliest infectious diseases worldwide. Only 5-15% of people infected with Mycobacterium tuberculosis develop active TB disease (ATB), while others remain latently infected (LTBI) during their lifetime, which has a completely different clinical treatment schedule. However, most current clinical diagnostic methods are based on the immune response of M. tuberculosis infections and cannot distinguish ATB from LTBIs. Thus, the rapid diagnosis of active or latent tuberculosis infections remains a serious challenge for clinicians. In this work, based on the test data of a total of 478 patients, 36 blood biochemical data were specially included with T-SPOT.TB detection results which are all from routine clinical practice as commercially available. Then a discrimination method to detect ATB infections was successfully developed based on these data by the random forest algorithm. This method presents a robust classification performance with AUC as 0.9256 and 0.8731 for the cross-validation set and the external validation set, respectively. This work suggests an innovative strategy for identification of ATB disease from a single drop of blood with advantages of being timely, efficient, and economical. It also provides valuable information for the comprehensive understanding of TB with deep associations between TB infection and routine blood test data. The web server of this identification method, called ATBdiscrimination, is now available online at http://lishuyan.lzu.edu.cn/ATB/ATBdiscrimination.html .

The effect of combining QuantiFERON-TB Gold In-Tube test with tuberculin skin test on the detection of active tuberculosis

Background

Interferon-γ release assays (IGRAs) and tuberculin skin tests (TSTs) play an important role in the detection of tuberculosis (TB) infection. However, the interaction between these tests in detecting active pulmonary TB in adults has never been researched.

Methods

A matched case-control study was conducted in Taiwan from 1 March 2012 to 31 December 2013 by enrolling 150 confirmed TB cases and 852 matched controls dwelling at the same area (stratified by low, medium and high incidence).

Results

Compared with a negative QuantiFERON-TB Gold In-Tube (QFT-GIT) test and a negative tuberculin skin test (TST), the effect size for detecting active pulmonary TB was highest for both a positive QFT-GIT and positive TST (adjusted odds ratio [aOR] 8.77 [95% confidence interval {CI} 4.51 to 17.05]), but the detectability was substantially attenuated in the absence of either a positive TST (aOR 1.59 [95% CI 0.70 to 3.63]) or positive QFT-GIT (aOR 1.15 [95% CI 0.48 to 2.71]) after controlling for age and gender. The joint effect of detecting active TB was positively synergistic according to a large positive value of relative excess risk due to interaction (7.05 [95% CI 2.48 to 11.61]).

Conclusions

The administration of both the IGRA and TST for enhancing the detectability of active pulmonary TB in an area with a moderate prevalence of TB such as Taiwan is strongly suggested.

Mycobacterial Lipoprotein Z Triggers Efficient Innate and Adaptive Immunity for Protection Against Mycobacterium tuberculosis Infection

Mycobacterial lipoproteins are considered to be involved in both virulence and immunoregulatory processes during Mycobacterium tuberculosis (M.tb) infection. In our previous investigations on the immunoreactivity of more than 30 M.tb proteins in active TB patients, we identified mycobacterial lipoprotein Z (LppZ) as one of the most immune dominant antigens. How LppZ triggers immune responses is still unclear. In this study, we analyzed LppZ-mediated innate and adaptive immunity using a murine air pouch model and an M.tb infection model, respectively. We found that LppZ could not only recruit inflammatory cells but also induce the production of proinflammatory cytokines inside the pouches. LppZ could also induce strong Th1 responses following immunization and confer protection against challenge with M.tb virulent strain H37Rv at a similar level to BCG vaccination but with less pathological damage in the lungs. Furthermore, we revealed the presence of LppZ-specific functional CD4⁺ T cells in the lungs of the challenged mice that were capable of secreting double or triple cytokines, including IFN-γ, IL-2, and TNF-α. Our study thus demonstrates that LppZ is of strong immunogenicity during M.tb infection in both humans and mice and has the ability to trigger effective innate and cellular immunity. Considering the limitations of candidate antigens in the pipeline of TB vaccine development, LppZ-mediated immune protection against M.tb challenge in the mouse model implies its potential application in vaccine development.

Risk Factors for Indeterminate Interferon-Gamma Release Assay for the Diagnosis of Tuberculosis in Children-A Systematic Review and Meta-Analysis

Background: Interferon-gamma release assays (IGRA) are well-established immunodiagnostic tests for tuberculosis (TB) in adults. In children these tests are associated with higher rates of false-negative and indeterminate results. Age is presumed to be one factor influencing cytokine release and therefore test performance. The aim of this study was to systematically review factors associated with indeterminate IGRA results in pediatric patients. Methods: Systematic literature review guided by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) searching PubMed, EMBASE, and Web of Science. Studies reporting results of at least one commercially available IGRA (QuantiFERON-TB, T-SPOT.TB) in pediatric patient groups were included. Random effects meta-analysis was used to assess proportions of indeterminate IGRA results. Heterogeneity was assessed using the I² value. Risk differences were calculated for studies comparing QuantiFERON-TB and T-SPOT.TB in the same study. Meta-regression was used to further explore the influence of study level variables on heterogeneity. Results: Of 1,293 articles screened, 133 studies were included in the final analysis. These assessed QuantiFERON-TB only in 77.4% (103/133), QuantiFERON-TB and T-SPOT.TB in 15.8% (21/133), and T-SPOT.TB only in 6.8% (9/133) resulting in 155 datasets including 107,418 participants. Overall 4% of IGRA results were indeterminate, and T-SPOT.TB (0.03, 95% CI 0.02-0.05) and QuantiFERON-TB assays (0.05, 95% CI 0.04-0.06) showed similar proportions of indeterminate results; pooled risk difference was-0.01 (95% CI -0.03 to 0.00). Significant differences with lower proportions of indeterminate assays with T-SPOT.TB compared to QuantiFERON-TB were only seen in subgroup analyses of studies performed in Africa and in non-HIV-infected immunocompromised patients. Meta-regression confirmed lower proportions of indeterminate results for T-SPOT.TB compared to QuantiFERON-TB only among studies that reported results from non-HIV-infected immunocompromised patients (p < 0.001). Conclusion: On average indeterminate IGRA results occur in 1 in 25 tests performed. Overall, there was no difference in the proportion of indeterminate results between both commercial assays. However, our findings suggest that in patients in Africa and/or patients with immunocompromising conditions other than HIV infection the T-SPOT.TB assay appears to produce fewer indeterminate results.

A Systematic Review on Novel Mycobacterium tuberculosis Antigens and Their Discriminatory Potential for the Diagnosis of Latent and Active Tuberculosis

Background: Current immunodiagnostic tests for tuberculosis (TB) are based on the detection of an immune response toward mycobacterial antigens injected into the skin or following an in-vitro simulation in interferon gamma-release assays. Both tests have limited sensitivity and are unable to differentiate between tuberculosis infection (LTBI) and active tuberculosis disease (aTB). To overcome this, the use of novel Mycobacterium tuberculosis (M. tuberculosis) stage-specific antigens for the diagnosis of LTBI and aTB has gained interest in recent years. This review summarizes current evidence on novel antigens used for the immunodiagnosis of tuberculosis and discrimination of LTBI and aTB. In addition, results on measured biomarkers after stimulation with novel M. tuberculosis antigens were also reviewed.

Methods: A systematic literature review was performed in Pubmed, EMBASE and web of science searching articles from 2000 up until December 2017. Only articles reporting studies in humans using novel antigens were included.

Results: Of 1,533 articles screened 34 were included in the final analysis. A wide range of novel antigens expressed during different stages and types of LTBI and aTB have been assessed. M. tuberculosis antigens Rv0081, Rv1733c, Rv1737c, Rv2029c, Rv2031 and Rv2628, all encoded by the dormancy of survival regulon, were among the most widely studied antigens and showed the most promising results. These antigens have been shown to have best potential for differentiating LTBI from aTB. In addition, several studies have shown that the inclusion of cytokines other than IFN-γ can improve sensitivity.

Conclusion: There is limited evidence that the inclusion of novel antigens as well as the measurement of other biomarkers than IFN-γ may improve sensitivity and may lead to a discrimination of LTBI from aTB.

Validation and comparison of ELISA kits to measure interferon gamma responses in QuantiFERON cultural supernatants for diagnosis of tuberculosis

Much effort has been made to reduce the cost of LTBI diagnosis with equivalent efficacy and efficiency of interferon-γ release assay (IGRA). This study showed that repeatability, intermediate precision, and accuracy of the Bionote-ELISA were comparable to QFT-ELISA. The Bionote-ELISA could provide the alternative method.

Novel interferon-gamma assays for diagnosing tuberculosis in young children in India

SETTING

The tuberculin skin test (TST) and interferon-gamma release assays (IGRAs) are used as supportive evidence to diagnose active tuberculosis (TB). Novel IGRAs could improve diagnosis, but data are lacking in young children.

DESIGN

Children (age 5 years) with suspected TB were prospectively screened at a tertiary hospital in Pune, India; the children underwent TST, and standard (early secretory antigenic target 6 and culture filtrate protein 10) and enhanced (five additional novel antigens) enzyme-linked immunospot (ELISpot) assays.

RESULTS

Of 313 children (median age 30 months) enrolled, 92% had received bacille Calmette-Guérin vaccination, 53% were malnourished and 9% were coinfected with the human immunodeficiency virus (HIV); 48 (15%) had TB, 128 (41%) did not, and TB could not be ruled out in 137 (44%). The sensitivity of enhanced (45%) and standard (42%) ELISpot assays for diagnosing TB was better than that of TST (20%) (P  0.03); however, enhanced ELISpot was not more sensitive than the standard ELISpot assay (P = 0.50). The specificity of enhanced ELISpot, standard ELISpot and TST was respectively 82% (95%CI 74-89), 88% (95%CI 81-94) and 98% (95%CI 93-100). Rv3879c and Rv3615c, previously reported to be promising antigens, failed to improve the diagnostic performance of the ELISpot assay.

CONCLUSION

The TST and the standard and novel ELISpot assays performed poorly in diagnosing active TB among young children in India.

Household tuberculosis contact investigation in a tuberculosis-prevalent country: Are the tuberculin skin test and interferon-gamma release assay enough in elderly contacts?

The high background rates of positive results on the tuberculin skin test (TST) and interferon-gamma release assay (IGRA) sometimes confuse the investigation of tuberculosis (TB) contact in TB-prevalent countries, particularly in elderly contacts. The aim was to investigate the predictive value of TST and IGRA for diagnosing latent TB infection (LTBI) in elderly household contacts in South Korea.In this retrospective study, TST and IGRA results of household contacts of suspected pulmonary TB patients were reviewed according to the index patient's final diagnosis (TB group: culture-confirmed pulmonary TB, non-TB group: pulmonary disease other than TB).A total of 249 contacts were included in the analysis (188 in the TB group and 61 in the non-TB group). In the TB group, TST and IGRA were positive in 42.6% and 45.7% of contacts, respectively. In the non-TB group, TST and IGRA were positive in 32.8% and 23.0% of contacts, respectively. TST did not show any differences between the TB and non-TB groups for any age group, whereas IGRA showed differences between the 2 groups for those ages 18 to 39 and 40 to 59 years. However, there were no significant differences between the groups for the ≥60 years old group.In elderly contacts, neither TST nor IGRA showed clear discrimination of positivity between the groups. Further studies are needed to predict which elderly contacts are at risk for progression to active TB as well as to accurately detect recent Mycobacterium tuberculosis infection in this vulnerable population.

Mycobacterium tuberculosis Rv3615c is a highly immunodominant antigen and specifically induces potent Th1-type immune responses in tuberculosis pleurisy

T-cell responses have been demonstrated to be essential for preventing Mycobacterium tuberculosis infection. The Th1-cytokines produced by T cells, such as INF-γ, IL-2, and TNF-α, not only limit the invasion of M. tuberculosis but also eliminate the pathogen at the site of infection. Bacillus Calmette-Guérin (BCG) is known to induce Th1-type responses but the protection is inadequate. Identification of immunogenic components, in addition to those expressed in BCG, and induction of a broad spectrum of Th1-type responses provide options for generating sufficient adaptive immunity. Here, we studied human pulmonary T-cell responses induced by the M. tuberculosis-specific antigen Rv3615c, a protein with a similar size and sequence homology to ESAT-6 and CFP-10, which induced dominant CD4⁺ T-cell responses in human tuberculosis (TB) models. We characterized T-cell responses including cytokine profiling, kinetics of activation, expansion, differentiation, TCR usage, and signaling of activation induced by Rv3615c compared with other M. tuberculosis-specific antigens. The expanded CD4⁺ T cells induced by Rv3615c predominately produced Th1, but less Th2 and Th17, cytokines and displayed effector/memory phenotypes (CD45RO⁺CD27^-CD127^-CCR7^-). The magnitude of expansion and cytokine production was comparable to those induced by well-characterized the 6 kDa early secreted antigenic target (ESAT-6), the 10 kDa culture filtrate protein (CFP-10) and BCG. Rv3615c contained multiple epitopes Rv3615c_1-15, Rv3615c_6-20, Rv3615c_66-80, Rv3615c_71-85 and Rv3615c_76-90 that activated CD4⁺ T cells. The Rv3615c-specific CD4⁺ T cells shared biased of T-cell receptor variable region of β chain (TCR Vβ) 1, 2, 4, 5.1, 7.1, 7.2 and/or 22 chains to promote their differentiation and proliferation respectively, by triggering a signaling cascade. Our data suggest that Rv3615c is a major target of Th1-type responses and can be a highly immunodominant antigen specific for M. tuberculosis infection.

IFN-γ and IL-2 Responses to Recombinant AlaDH against ESAT-6/CFP-10 Fusion Antigens in the Diagnosis of Latent versus Active Tuberculosis Infection

BACKGROUND

Discriminating latent tuberculosis infection (LTBI) from active TBI may be challenging. The objective of this study was to produce the recombinant L-alanine dehydrogenase (AlaDH) antigen and evaluate individuals with LTBI, those with active TBI, and uninfected individuals by enzyme-linked immunospot assay (ELISPOT) in order to distinguish LTBI from active TBI.

METHODS

This exploratory study was performed in the Iranian city of Shiraz from 2014 to 2015. The study population (N=99) was divided into 3 groups: individuals with newly diagnosed active TBI (n=33), their household contacts (n=33), and controls (n=33). AlaDH was produced through PCR and cloning methods. The diagnostic characteristics of AlaDH vs. ESAT-6/CFP-10 were evaluated in responses to interferon-γ (IFN-γ) and interleukin-2 (IL-2) with ELISPOT. Differences between the groups were assessed with the Kruskal-Wallis and Mann-Whitney tests for nonparametric data analysis. The statistical analyses were performed with SPSS, version 16.

RESULTS

IFN-γ responses to both ESAT-6/CFP-10 (P=0.81) and AlaDH (P=0.18) revealed that there were no significant differences between the individuals with LTBI and those with active TBI. The same results were determined for IL-2 responses to ESAT-6/CFP-10 between the 2 groups, while significantly higher IL-2 responses to AlaDH were observed in LTBI than in active TBI. According to the ROC curve analysis, a cutoff value of 275 SFC showed sensitivity of 75.8% and specificity of 78.8% for distinguishing LTBI from active TBI by IL-2 responses to AlaDH.

CONCLUSION

The current study suggests that it may be possible to discriminate LTBI from active TBI by IL-2 responses to AlaDH.

Qualitative and quantitative results of interferon-γ release assays for monitoring the response to anti-tuberculosis treatment

BACKGROUND/AIMS

The usefulness of interferon-γ release assays (IGRAs) in monitoring to responses to anti-tuberculosis (TB) treatment is controversial. We compared the results of two IGRAs before and after anti-TB treatment in same patients with active TB.

METHODS

From a retrospective review, we selected patients with active TB who underwent repeated QuantiFERON-TB Gold (QFN-Gold, Cellestis Limited) and T-SPOT.TB (Oxford Immunotec) assays before and after anti-TB treatment with first-line drugs. Both tests were performed prior to the start of anti-TB treatment or within 1 week after the start of anti-TB treatment and after completion of treatment.

RESULTS

A total of 33 active TB patients were included in the study. On the QFN-Gold test, at baseline, 23 cases (70%) were early secreted antigenic target 6-kDa protein 6 (ESAT-6) or culture filtrate protein 10 (CFP-10) positive. On the T-SPOT. TB test, at baseline, 31 cases (94%) were ESAT-6 or CFP-10 positive. Most of patients remained both test-positive after anti-TB treatment. Although changes in interferon-γ release responses over time were highly variable in both tests, there was a mean decline of 27 and 24 spot-forming counts for ESAT-6 and CFP-10, respectively on the T-SPOT.TB test (p < 0.05 for all).

CONCLUSIONS

Although limited by the small number of patients and a short-term follow-up, there was significant decline in the quantitative result of the T-SPOT. TB test with treatment. However, both commercial IGRAs may not provide evidence regarding the cure of disease in Korea, a country where the prevalence of TB is within the intermediate range.

The TB vaccine H56+IC31 dose-response curve is peaked not saturating: Data generation for new mathematical modelling methods to inform vaccine dose decisions

INTRODUCTION

In vaccine development, dose-response curves are commonly assumed to be saturating. Evidence from tuberculosis (TB) vaccine, H56+IC31 shows this may be incorrect. Mathematical modelling techniques may be useful in efficiently identifying the most immunogenic dose, but model calibration requires longitudinal data across multiple doses and time points.

AIMS

We aimed to (i) generate longitudinal response data in mice for a wide range of H56+IC31 doses for use in future mathematical modelling and (ii) test whether a 'saturating' or 'peaked' dose-response curve, better fit the empirical data.

METHODS

We measured IFN-γ secretion using an ELISPOT assay in the splenocytes of mice who had received doses of 0, 0.1, 0.5, 1, 5 or 15μg H56+IC31. Mice were vaccinated twice (at day 0 and 15) and responses measured for each dose at 8 time points over a 56-day period following first vaccination. Summary measures Area Under the Curve (AUC), peak and day 56 responses were compared between dose groups. Corrected Akaike Information Criteria was used to test which dose-response curve best fitted empirical data, at different time ranges.

RESULTS

(i) All summary measures for dose groups 0.1 and 0.5μg were higher than the control group (p<0.05). The AUC was higher for 0.1 than 15μg dose. (ii) There was strong evidence that the dose-response curve was peaked for all time ranges, and the best dose is likely to be lower than previous empirical experiments have evaluated.

CONCLUSION

These results suggest that the highest, safe dose may not always optimal in terms of immunogenicity, as the dose-response curve may not saturate. Detailed longitudinal dose range data for TB vaccine H56+IC31 reveals response dynamics in mice that should now be used to identify optimal doses for humans using clinical data, using new data collection and mathematical modelling.

Diagnosis of Tuberculous Meningitis Using a Combination of Peripheral Blood T-SPOT.TB and Cerebrospinal Fluid Interferon-γ Detection Methods

OBJECTIVE

To evaluate the effectiveness of combined peripheral blood T-SPOT.TB and cerebrospinal fluid interferon-γ (cIFN-γ) detection methods in the diagnosis of tuberculous meningitis (TBM).

METHODS

A total of 30 individuals with TBM and 39 control individuals without TBM participated in this study. IFN-γ-secreting T cells were detected by enzyme-linked immunospot (ELISPOT), and cIFN-γ was detected by enzyme-linked immunosorbent assay (ELISA). We collected cerebrospinal fluid from 10 patients in the TBM group on initial visit and at 4 weeks, to observe changes.

RESULTS

The sensitivity and specificity of peripheral-blood T-SPOT.TB testing in the diagnosis of TBM were 70% and 87%, respectively. The area under the ROC curve of cIFN-γ for TBM diagnosis was 0.819, and the corresponding sensitivity and specificity were 83% and 85%, respectively. When T-SPOT.TB and cIFN-γ results were positive, the specificity and positive predictive value of TBM diagnosis reached 100%.

CONCLUSIONS

Combined use of T-SPOT.TB and cIFN-γ could improve the diagnosis efficiency of TBM. Dynamic observation of cIFN-γ is also important in monitoring TBM because the level of this analyte significantly decreases after treatment.

Inflammatory markers and clinical characteristics for predicting persistent positivity of interferon gamma release assay in dialysis population

The interferon-gamma release assay (IGRA) is useful for diagnosing latent tuberculosis infection (LTBI), however the rate of negative conversion is high, especially in dialysis patients. Few studies have focused on predicting persistently positive patients who are at high risk of tuberculosis reactivation. We screened dialysis patients, and used QuantiFERON-TB Gold In-tube (QFT-GIT) to identify LTBI. Of the 157 participants who had initially positive QFT-GIT, 82 had persistently positivity and 75 had negative conversion. The persistently positive group were younger, more were current smokers, and had higher plasma level of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) and QFT-GIT responses than the negative conversion group. Multivariate logistic regression for persistent positivity revealed that high plasma sTREM-1 and QFT-GIT response, young age and TB contact history were independent factors. Currently smoking had borderline significance. The area under the receiver operating characteristic curve using the multi-factor model was 0.878, higher than 0.821 by QFT-GIT response of 0.95 IU/ml. In conclusion, dialysis patients with persistent LTBI status may be associated with a young age, high plasma sTREM-1, strong QFT-GIT response, currently smoking, and TB contact history. If resources are limited, these five predictors can be used to prioritize QFT-GIT-positive dialysis patients for LTBI treatment.

An Analysis of the Clinical, Endoscopic, and Pathologic Features of Intestinal Tuberculosis

GOALS

The aim of this study was to retrospectively analyze the clinical, endoscopic, and pathologic features of intestinal tuberculosis (TB).

BACKGROUND

The prevalence of intestinal TB has been increasing in China.

STUDY

The clinical, imaging and laboratory examination, endoscopic, and pathologic data of 81 cases of intestinal TB patients were retrospectively analyzed.

RESULTS

There were 48 male and 33 female cases whose age ranged from 17 to 76 years (mean, 32.4±1.6 y). Fifty-five cases were diagnosed by endoscopic biopsy, and 26 cases by postoperative pathologic examination. The common symptoms were chronic right lower abdominal and periumbilical pain (87.7%), weight loss (80.2%), anemia (64.2%), diarrhea (46.9%), fever (43.2%), diarrhea alternating with constipation (38.3%), and night sweats (30.9%). Purified protein derivative test (51.9%), TB antibody (34.6%), and TB protein chip (40.7%) had lower sensitivity. T-spot test sensitivity was 86.4%. Endoscopic types included ulcerative (52.7%), ulcero-proliferative (27.3%), and proliferative (20.0%) with mucosal hyperemia and edema (87.2%), mucosal erosion (76.4%), patulous ileocecal valve (65.5%), polypoid hyperplasia (58.2%), annular ulcer (52.7%), nodular hyperplasia (45.5%), and luminal stenosis (29.1%). Histopathologic findings were chronic mucosal inflammation (87.3%), ulceration (74.5%), lymphocytic aggregation (69.1%), and granulomatous fusion (58.2%). The presence of caseating granulomas (74.5%) and necrosis (25.5%) was helpful, but not common.

CONCLUSIONS

The clinical symptoms of intestinal TB are nonspecific. The most common anatomic locations for intestinal TB are the ileocecal valve and cecum. The T-spot test has high sensitivity, and it can be used to support the diagnosis of intestinal TB. The typical endoscopic features are circumscribed intestinal ulcers, and histopathologic findings of biopsy specimens can be also useful in making the diagnosis.

Effects of KLK Peptide on Adjuvanticity of Different ODN Sequences

Endosomal Toll-like receptors (TLR) such as TLR3, 7, 8 and 9 recognize pathogen associated nucleic acids. While DNA sequence does influence degree of binding to and activation of TLR9, it also appears to influence the ability of the ligand to reach the intracellular endosomal compartment. The KLK (KLKL5KLK) antimicrobial peptide, which is immunostimulatory itself, can translocate into cells without cell membrane permeabilization and thus can be used for endosomal delivery of TLR agonists, as has been shown with the IC31 formulation that contains an oligodeoxynucleotide (ODN) TLR9 agonist. We evaluated the adjuvant activity of KLK combined with CpG or non-CpG (GpC) ODN synthesized with nuclease resistant phosphorothioate (S) or native phosphodiester (O) backbones with ovalbumin (OVA) antigen in mice. As single adjuvants, CpG(S) gave the strongest enhancement of OVA-specific immunity and the addition of KLK provided no benefit and was actually detrimental for some readouts. In contrast, KLK enhanced the adjuvant effects of CpG(O) and to a lesser extent of GpC (S), which on their own had little or no activity. Indeed while CD8 T cells, IFN-γ secretion and humoral response to vaccine antigen were enhanced when CpG(O) was combined with KLK, only IFN-γ secretion was enhanced when GpC (S) was combined to KLK. The synergistic adjuvant effects with KLK/ODN combinations were TLR9-mediated since they did not occur in TLR9 knock-out mice. We hypothesize that a nuclease resistant ODN with CpG motifs has its own mechanism for entering cells to reach the endosome. For ODN without CpG motifs, KLK appears to provide an alternate mechanism for accessing the endosome, where it can activate TLR9, albeit with lower potency than a CpG ODN. For nuclease sensitive (O) backbone ODN, KLK may also provide protection from nucleases in the tissues.

Risk of Tuberculosis Among Patients on Dialysis: The Predictive Value of Serial Interferon-Gamma Release Assay

Patients on long-term dialysis are at high risk for tuberculosis (TB). Although latent tuberculosis infection (LTBI) is good target for TB eradication, interferon-gamma release assay-defined LTBI has a high proportion of negative conversion and lacks active TB correlation among patients on dialysis.Patients on long-term dialysis were screened in multiple centers in Taiwan. QuantiFERON-TB Gold In-tube (QFT-GIT) was used to define LTBI and was performed thrice at 6-month intervals. The primary outcome was active TB diagnosed after LTBI screening. The incidence and predictive value of QFT-GIT were analyzed.The 940 dialysis patients enrolled had an average age of 59.3 years. The initial QFT-GIT results were positive in 193, including 49.6% with persistent positive results on second check. In an average follow-up period of 3 years, 7 patients had TB. Three (319.1 per 100,000 person-yrs) and 4 (141.8 per 100,000 person-yrs) of them were prevalent and incident TB cases, respectively. Persistent positive QFT-GIT for 2 and 3 times correlated with increased hazard ratio for TB (14.44 and 20.29, respectively) compared with a single positive result (hazard ratio 10.38). Among those with 3 positive QFT-GIT results, TB development rate was 4.5% and incidence rate was 1352.3 per 100,000 person-years. In contrast, none of the incident TB occurred in those with initial positive and then negative conversion of QFT-GIT.In an area of intermediate TB incidence, dialysis patients have high TB risk. LTBI status is a good predictor of TB development, especially for those with more than 1 positive result. After excluding prevalent TB cases, serial follow-up of LTBI may narrow the target population to reduce treatment costs.

Interleukin-4 enzyme-linked immunospot assay may be useful for diagnosing sensitization to house dust mite

BACKGROUND

The skin prick test (SPT) is considered a standard test for identification of allergens, but it has some limitations in clinical practice. The multiple allergen simultaneous test (MAST), which measures allergen-specific immunoglobulin E in patients' serum, is a widely used alternative test, but is limited by its relatively low sensitivity and specificity. As a novel diagnostic test to identify allergens, we investigated the sensitivity and specificity of an interleukin-4 (IL-4) enzyme-linked immunospot (ELISpot) assay for Dermatophagoides farinae (Der f) and Dermatophagoides pteronyssinus (Der p).

METHODS

Based on the symptoms and SPT results, 43 house dust mite (HDM) allergic rhinitis (AR) patients and 41 control subjects were included. Peripheral blood was drawn from each subject for IL-4 ELISpot assay and MAST. The receiver operating characteristic (ROC) curve analysis was conducted to determine the cutoff values. Sensitivity, specificity, and positive and neg predictive values were compared between the 2 tests.

RESULTS

The sensitivity, specificity, and areas under the ROC curve (AUCs) of the IL-4 ELISpot assay were 88.4%, 97.6%, and 0.939 for Der f, and 95.3%, 97.5%, and 0.971 for Der p, respectively. However, the sensitivity, specificity, and AUC of MAST were 76.7%, 73.2%, and 0.777 for Der f, and 69.8%, 75.6%, and 0.788 for Der p, respectively.

CONCLUSION

The IL-4 ELISpot assay showed higher sensitivity, specificity, and AUC than MAST, which indicates its clinical feasibility for diagnosing allergy for HDM. A further study is needed to determine the accuracy of the IL-4 ELISpot assay for other common allergens.

Adenylate kinase: a novel antigen for immunodiagnosis and subunit vaccine against tuberculosis

Mycobacterium tuberculosis (M.tb)-derived antigens capable of inducing strong cellular and/or humoral responses are potential targets for both immunodiagnosis and vaccine development against tuberculosis (TB). In the present study, we identified adenylate kinase (ADK, Rv0733) as an antigen that induces high cellular and antibody responses in active TB patients. We consequently tested the use of ADK-specific T cells and antibodies as biomarkers for TB diagnosis. The ADK-specific IFN-γ-producing cells detected by ELISPOT assay showed a sensitivity of 85.0 % and specificity of 94.15 % for TB diagnosis while ADK-specific IgG antibody showed a sensitivity of 40.35 % and specificity of 96.43 %. Combining ADK-specific cellular and antibody responses increased the sensitivity to 91.59 % and the specificity to 96.15 %. Immunogenicity and protection against M.tb infection were further tested in a murine model. Immunization with ADK protein elicited strong specific T- and B-cell responses, and provided protection against the virulent H37Rv stain of M.tb resulting in lower bacilli load in the spleens and lungs. More ADK-specific polyfunctional Th1 cells were observed in the lungs when compared to adjuvant-immunized mice. ADK thus may serve as a novel M.tb antigen for TB immunodiagnosis and development of subunit vaccines.

KEY MESSAGES

ADK induces strong immune responses both in humans and mice. ADK-specific IFN-γ production and B-cell responses have high potential for TB diagnosis. ADK immunization provides protection against M.tb infection.

Granzyme B as a diagnostic marker of tuberculosis in patients with and without HIV coinfection

Immunodiagnostic tests for tuberculosis (TB) are based on the estimation of interferon γ (IFN-γ) or IFN-γ-secreting CD4(+) T cells following ex vivo stimulation with ESAT6 and CFP-10. Sensitivity of these tests is likely to be compromised in CD4(+) T-cell-depleted situations, like HIV-TB coinfection. CD4(+) and CD8(+) T cells, isolated from 3 groups, viz., HIV-negative patients with active TB, HIV-TB coinfected patients, and healthy household contacts (HHCs) were cocultivated with autologous dendritic cells, and the cytokine response to rESAT6 stimulation was compared between groups in supernatants. While CD4(+) T-cell stimulation yielded significantly elevated levels of IFN-γ and interleukin 4 in HIV-negative TB patients, compared to HHCs, the levels of both these cytokines were nondiscriminatory between HIV-positive TB patients and HHCs. However, CD8(+) T-cell stimulation yielded significantly elevated granzyme B titers in both groups of patients, irrespective of HIV coinfection status. Hence, contrary to IFN-γ, granzyme B might be a useful diagnostic marker for Mycobacterium tuberculosis infection particularly in HIV coinfected patients.

Clinical Application of Interferon-γ Release Assays for the Prevention of Tuberculosis in Countries with Low Incidence

Despite global efforts to control tuberculosis (TB) the estimated number of people who developed TB worldwide increased to an all-time record of more than 10 million in 2015. The goal of the World Health Organization (WHO) to reduce the global incidence of TB to less than 100 cases per million by 2035, cannot be reached unless TB prevention is markedly improved. There is a need for an improved vaccine that better protects individuals who are exposed to Mycobacterium tuberculosis from infection and active disease compared to the current M. bovis Bacille Calmette Guérin (BCG) vaccine. In the absence of such a vaccine, prevention relies on infection control measures and preventive chemotherapy for people with latent infection with M. tuberculosis (LTBI), who have the highest risk of progression to active TB. During the past decade, interferon-γ release assays (IGRAs) have increasingly replaced the tuberculin skin test as screening tools for the diagnosis of LTBI in countries with a low incidence of TB. Despite recent WHO guidelines on the management of LTBI, the definition of groups at risk for TB remains controversial, and the role of IGRAs for TB prevention in low-incidence countries remains uncertain. We reviewed the scientific literature and provide recommendations for the use of IGRAs for LTBI diagnosis in low-incidence countries. These recommendations are based on the number of patients needing treatment in order to prevent one case of TB. As the positive predictive value of IGRAs for the development of TB is sub-optimal, research must focus on the identification of alternative biomarkers that offer better predictive ability in order to substantially reduce the number needing treatment while improving the prevention of TB and improving the effectiveness of targeted preventive chemotherapy.

Rate of tuberculosis infection in children and adolescents with household contact with adults with active pulmonary tuberculosis as assessed by tuberculin skin test and interferon-gamma release assays

Tuberculosis (TB) infection was evaluated in Brazilian immunocompetent children and adolescents exposed and unexposed (control group) to adults with active pulmonary TB. Both groups were analysed by clinical and radiological assessment, TST, QFT-IT and T-SPOT.TB. The three tests were repeated after 8 weeks in the TB-exposed group if results were initially negative. Individuals with latent tuberculosis infection (LTBI) were treated and tests were repeated after treatment. Fifty-nine TB-exposed and 42 controls were evaluated. Rate of infection was 69·5% and 9·5% for the exposed and control groups, respectively. The exposed group infection rate was 61% assessed by TST, 57·6% by T-SPOT.TB, and 59·3%, by QFT-IT. No active TB was diagnosed. Agreement between the three tests was 83·1% and 92·8% in the exposed and control groups, respectively. In the exposed group, T-SPOT.TB added four TB diagnoses [16%, 95% confidence interval (CI) 1·6-30·4] and QFT-IT added three TB diagnoses (12%, 95% CI 0-24·7) in 25 individuals with negative tuberculin skin test (TST). Risk factors associated to TB infection were contact with an adult with active TB [0-60 days: odds ratio (OR) 6·9; >60 days: OR 27·0] and sleeping in the same room as an adult with active TB (OR 5·2). In Brazilian immunocompetent children and adolescents, TST had a similar performance to interferon-gamma release assays and detected a high rate of LTBI.

Ex vivo assessment of cellular immune function - applications in patient care and clinical studies

Cellular ex vivo assays have a broad range of applications in patient care and clinical studies, especially when they are standardized and highly sensitive. As compared to analyses by molecular genetics such as the single nucleotide polymorphism (SNP) testing, they are usually more global. These assays partly mimic the in vivo situation, relying on a complex interaction of various immune cells. For example, they can be used to determine modulation of alloresponses by treatment or underlying disease, diagnose and quantify primary and secondary cellular immunodeficiency, follow-up vaccination responses, measure adoptive transfer of virus-specific immunity via hematopoietic stem cell or liver transplantation, assess allergy, antimicrobial immunity and also rare effector/memory cells directed against tumor antigens. This review will first shortly describe various cellular in vitro methods and then present applications, summarizing some own studies performed within the last 18 years.

High level of IFN-γ released from whole blood of human tuberculosis infections following stimulation with Rv2073c of Mycobacterium tuberculosis

More efficacious and specific biomarkers are urgently needed for better control of tuberculosis (TB), the second leading infectious cause of mortality worldwide. The region of difference 9 (RD9) presents the genome of the causative pathogen Mycobacterium tuberculosis rather than other species of the genus Mycobacterium, which might be promising targets for specific diagnosis, vaccine development and pathogenesis. In this study, two proteins Rv2073c and Rv2074, encoded by the RD9 were expressed and purified from Escherichia coli system. Following stimulation with both proteins, the levels of IFN-γ secreted by T cells from a total of 49 whole blood samples obtained from clinically diagnosed active TB patients, patients with latent TB infections (LTBIs), and healthy donors, were compared with those of the incubation with recombinant fusion protein of CFP21 and MPT64 (rCM). Our results demonstrated that only Rv2073c could induce a higher level of IFN-γ in TB infections than healthy controls and there was a positive correlation between Rv2073c- and rCM-specific IFN-γ levels in TB infections and healthy donors, respectively. These findings indicate that Rv2073c might be a promising antigen for specific diagnostic reagents and vaccine candidates of TB.

Comparison of the Prevalence of Latent Tuberculosis Infection among Non-Dialysis Patients with Severe Chronic Kidney Disease, Patients Receiving Dialysis, and the Dialysis-Unit Staff: A Cross-Sectional Study

Background

Patients with renal failure are vulnerable to tuberculosis, a common worldwide infectious disease. In the growing dialysis population, the risk for tuberculosis among the associated sub-groups is important but unclear. This study investigated latent tuberculosis infection (LTBI) in patients with severe chronic kidney disease (CKD) and among dialysis-unit staff caring for patients on dialysis.

Methods

From January 2012 to June 2013, patients undergoing dialysis, those with severe CKD (estimated glomerular filtration rate <30ml/min/1.73 m²), and the dialysis-unit staff (nursing staff and doctors in hemodialysis units) in several Taiwan hospitals were prospectively enrolled. Interferon-gamma release assay (IGRA) through QuantiFERON-TB Gold In-tube was used to determine LTBI. Predictors for LTBI were analyzed.

Results

Of the 599 participants enrolled, 106 (25%) in the dialysis group were IGRA positive. This was higher than the seven (11%) among severe CKD patients and 12 (11%) in the dialysis-unit staff. Independent predictors of LTBI in patient with renal dysfunction were old age (odds ratio [OR]: 1.03 [1.01–1.04] per year increment), prior TB lesion on chest radiograph (OR: 2.90 [1.45–5.83]), serum albumin (OR: 2.59 [1.63–4.11] per 1 g/dl increment), and need for dialysis (OR: 2.47, [1.02–5.95]). The QFT-GIT response was similar among the three groups. Malignancy (OR: 4.91 [1.84–13.10]) and low serum albumin level (OR: 0.22 [0.10–0.51], per 1 g/dl decrease) were associated with indeterminate IGRA results.

Conclusions

More patients on dialysis have LTBI compared to those with severe CKD and the dialysis-unit staff. Old age, prior radiographic TB lesion, high serum albumin, and need for dialysis are predictors of LTBI in patients with renal failure. Patients with severe CKD are a lower priority for LTBI screening. The hemodialysis environment is not a risk for LTBI and dialysis-unit staff may be treated as general healthcare workers.

[New methods of diagnosis in tuberculosis]

Bacteriological diagnosis of tuberculosis has benefited in recent years from many technological advances to improve rapidity and sensitivity of the techniques. Thus, new LED fluorescence microscopes are in the process of replacing the optical microscopes and the Ziehl-Neelsen technique, making the examination more precise, faster and easier. The manual and automatic liquid culture has improved Lowenstein-Jensen culture and helped shorten antibiotic sensitivity test, allowing appropriate management of patients. The development and standardization of molecular biology methods led to the rapid detection and identification of mycobacterium directly in clinical samples but also of resistance genes for early diagnosis of MDR-TB and dealing with them quickly. However, the performance of these techniques does not sufficiently cover the diagnosis of smear-negative tuberculosis, extrapulmonary forms, children- and immune-compromised tuberculosis where sensitivity is limited. The diagnosis of latent tuberculosis is reinforced by the in vitro release testing of gamma interferon overcoming the lack of specificity of the tuberculin skin test. Despite considerable progress, more amelioration is still needed to improve these techniques in order to extend them to the paucibacillary tuberculosis and to facilitate their access to low-resource countries.

Risk factors for latent tuberculosis infection in close contacts of active tuberculosis patients in South Korea: a prospective cohort study

Background

The diagnosis and treatment of latent tuberculosis infection (LTBI) have become mandatory to reduce the burden of tuberculosis worldwide. Close contacts of active TB patients are at high risk of both active and LTBI. The aim of this study is to identify the predominant risk factors of contracting LTBI, persons in close contact with TB patients were recruited. This study also aimed to compare the efficacy of the tuberculin skin test (TST) and QuantiFERON^®-TB GOLD (QFT-G) to diagnose LTBI.

Methods

Close contacts of active pulmonary TB patients visiting a hospital in South Korea were diagnosed for LTBI using TST and/or QFT-G. The association of positive TST and/or QFT-G with the following factors was estimated: age, gender, history of Bacillius Calmette-Guerin (BCG) vaccination, history of pulmonary TB, cohabitation status, the acid-fast bacilli smear status, and presence of cough in source cases.

Results

Of 308 subjects, 38.0% (116/305) were TST positive and 28.6% (59/206) were QFT-G positive. TST positivity was significantly associated with male gender (OR: 1.734; 95% CI: 1.001-3.003, p =0.049), history of pulmonary TB (OR: 4.130; 95% CI: 1.441-11.835, p =0.008) and household contact (OR: 2.130; 95% CI: 1.198-3.786, p =0.01) after adjustment for confounding variables. The degree of concordance between TST and QFT-G was fair (70.4%, κ =0.392).

Conclusions

A prevalence of LTBI among close contacts of active pulmonary TB patients was high, and prior TB history and being a household contact were risk factors of LTBI in the study population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0566-4) contains supplementary material, which is available to authorized users.

Differences between pediatric extra-pulmonary and pulmonary tuberculosis: a warning sign for the future

BACKGROUND

Tuberculosis (TB) remains a major global health problem. The childhood tuberculosis has some unique features different which makes the diagnosis more complicated. Here we described the epidemiologic, clinical and microbiologic features of children with extra pulmonary and pulmonary TB.

METHODS

The data of the patients <14 years with active TB were collected and compared in pulmonary (PTB) and extrapulmonary TB (EXPTB) patients.

RESULTS

A total of 128 cases was included. Forty-two cases occurred in children were < 5 years of age; 41 cases between 6-10 years and 45 cases > 10 years. PTB was present in 75,0% of the cases, and EXPTB was present in 25% of cases. There was no significant difference between the EXPTB and PTB by means of distribution of age groups (p=0,201). The rate of patients free of constitutional symptoms were significantly higher in EXPTB compared to PTB(p=0,000). There was no significant difference between EXPTB and PTB by means of sources detection(p=0,069).

CONCLUSION

TB is still a major public health problem. EXPTB has an insidious and silent onset without any constitutional symptoms, and both microbiological confirmation and the source by an adult are not frequently found. Moreover, detection of the adult source is mandatory for controlling the TB disease in children.

The performance and limitation of T-SPOT.TB for the diagnosis of TB in a high prevalence setting

BACKGROUND

Tuberculosis (TB) diagnosis remains difficulty. The previous reports have shown that the T-SPOT.TB assay may be a more promising diagnostic tool for TB, however, it needs a further study to evaluate the diagnostic value of T-SPOT.TB for the specific populations in a high prevalence setting.

METHODS

In this present study, we conducted stratified and comparable analyses to explore the clinical value and the limitation of T-SPOT.TB assay in TB diagnosis in a high TB prevalence setting, Southern China. A total of 413 subjects including 163 pulmonary TB (PTB), 39 extrapulmonary TB (EPTB), 106 non-TB pulmonary diseases (NTBPDs), 20 medical staff and 85 healthy controls were included in the study.

RESULTS

According to T-SPOT.TB, there had a high incidence of latent TB infection (LTBI) in general population in Southern China, especially in the NTBPDS and medical staff. The T-SPOT.TB had a high performance in the diagnosis of active TB (ATB) in a lower risk of TB infection population such as the general population, however, the T-SPOT.TB for the diagnosis of ATB in the high risk of TB infection populations involving close contacts such as the patients with pulmonary diseases (PD) or medical staff isn't reliable due to the interference by LTBI. Under this condition, the value of rule-out of the assay was seemed to be better than that of rule-in. We believed that the T-SPOT.TB is suitable for screening both the EPTB and the ATB combined with diabetes mellitus (DM). However, we found that the sensitivity of T-SPOT.TB in sputum smear-negative population wasn't as high as that in smear-positive population.

CONCLUSIONS

The T-SPOT.TB testing results should be interpreted with caution combined with subject's characteristics in a high prevalence setting.

Tuberculin skin testing and treatment modulates interferon-gamma release assay results for latent tuberculosis in migrants

Background

Identifying latent tuberculosis infection (LTBI) in people migrating from TB endemic regions to low incidence countries is an important control measure. However, no prospective longitudinal comparisons between diagnostic tests used in such migrant populations are available.

Objectives

To compare commercial interferon (IFN)-gamma release assays (IGRAs) and the tuberculin skin test (TST) for diagnosing LTBI in a migrant population, and the influence of antecedent TST and LTBI treatment on IGRA performance.

Materials and Methods

This cohort study, performed from February to September 2012, assessed longitudinal IGRA and TST responses in Nepalese military recruits recently arrived in the UK. Concomitant T-SPOT.TB, QFT-GIT and TST were performed on day 0, with IGRAs repeated 7 and 200 days later, following treatment for LTBI if necessary.

Results

166 Nepalese recruits were prospectively assessed. At entry, 21 individuals were positive by T-SPOT.TB and 8 individuals by QFT-GIT. There was substantial agreement between TST and T-SPOT.TB positives at baseline (71.4% agreement; κ = 0.62; 95% CI:0.44–0.79), but only moderate concordance between positive IGRAs (38.1% agreement; κ = 0.46; 95% CI:0.25–0.67). When reassessed 7 days following TST, numbers of IGRA-positive individuals changed from 8 to 23 for QFT-GIT (p = 0.0074) and from 21 to 23 for T-SPOT.TB (p = 0.87). This resulted in an increase in IGRA concordance to substantial (64.3% agreement; κ = 0.73; 95% CI:0.58-0.88). Thus, in total on day 0 and day 7 after testing, 29 out of 166 participants (17.5%) provided a positive IGRA and of these 13 were TST negative. Two hundred days after the study commenced and three months after treatment for LTBI was completed by those who were given chemoprophylaxis, 23 and 21 participants were positive by T-SPOT.TB or QFT-GIT respectively. When individual responses were examined longitudinally within this population 35% of the day 7 QFT-GIT-positive, and 19% T-SPOT.TB-positive individuals, were negative by IGRA. When the change in the levels of secreted IFN-γ was examined after chemoprophylaxis the median levels were found to have fallen dramatically by 77.3% from a pre-treatment median concentration of IFN-γ 2.73 IU/ml to a post-treatment median concentration IFN-γ 0.62 (p = 0.0002).

Conclusions

This study suggests differences in the capacity of commercially available IGRAs to identify LTBI in the absence of antecedent TST and that IGRAs, in the time periods examined, may not be the optimal tests to determine the success of chemoprophylaxis for LTBI.

Use of interferon gamma release assays in clinical practice: review of QuantiFERON-TB prescription in a French university hospital

BACKGROUND

In recent years, the clinical use of interferon gamma release assays (IGRAs) has increased exponentially, while their indications remain controversial given difficulties in interpretation. Four indications were recommended by the French National Authority for Health (HAS) in 2006. We evaluated the utilization of the QuantiFERON-TB Gold In-Tube (QFT-IT) test over a 1-y period in a French university hospital and the impact of IGRA results in particular.

METHODS

The QFT-IT tests requested in 2009 were analysed retrospectively, excluding those from the Occupational Health Department, the Regional Tuberculosis Centre, and rheumatology consultations for which the indications were clearly defined.

RESULTS

Three hundred and sixty QFT-IT tests were analysed. The interpretation was frequently problematic given the inclusion of a significant proportion of patients over 80 y of age (11%), immunocompromised patients (43%), and patients with a known history of tuberculosis (6%). The indications failed to comply with HAS recommendations in 42% of cases (151/360), i.e. 14% of all QFT-IT tests in 2009. Thirty-seven percent of request forms were related to suspected pulmonary tuberculosis. In the case of a positive QFT-IT test, the clinical decision-making was changed in 58% of cases when the indications met the HAS recommendations, compared with only 16% if they did not (p < 0.005).

CONCLUSION

When the indications do not meet the health authority recommendations, the diagnostic value of the IGRA remains limited.