Bronchoalveolar lavage enzyme-linked immunospot for a rapid diagnosis of tuberculosis: a Tuberculosis Network European Trialsgroup study

Rapid Diagnosis of Recurrent Paucibacillary Tuberculosis

Introduction

The rapid diagnosis of tuberculosis recurrence can be challenging due to persistently positive detection of Mycobacterium tuberculosis-specific DNA from sputum and bronchopulmonary samples in the absence of active disease.

Methods

We compared the diagnostic accuracy of the detection of M. tuberculosis-specific DNA by either Xpert (January 2010-June 2018) or Xpert Ultra (July 2018-June 2020) and M. tuberculosis-specific ELISPOT in bronchoalveolar lavage (BAL) samples with M. tuberculosis culture results from sputum or bronchopulmonary samples in patients with suspected recurrence of pulmonary tuberculosis.

Results

Among 44 individuals with previous tuberculosis and a presumptive diagnosis of recurrent pulmonary tuberculosis, 4/44 (9.1%) were diagnosed with recurrent tuberculosis by culture. DNA of M. tuberculosis was detected by Xpert in BAL fluid in 1/4 (25%) individuals with recurrent tuberculosis and in 2/40 (5%) cases with past tuberculosis without recurrence, while BAL-ELISPOT with a cut-off of >4,000 early secretory antigenic target-6-specific or culture filtrate protein-10-specific interferon-γ-producing lymphocytes per 1 million BAL-lymphocytes was positive in 4/4 (100%) individuals with recurrent tuberculosis and in 2/40 (5%) cases of past tuberculosis without recurrence.

Conclusion

M. tuberculosis-specific BAL-ELISPOT is more accurate than BAL-Xpert for the diagnosis of paucibacillary tuberculosis recurrence.

Loss of T cells expressing CD27 at the site of active tuberculosis - A prospective diagnostic study

The lack of a rapid and reliable diagnostic test for active tuberculosis is still a burden to the control of the infection. The accumulation of Mycobacterium tuberculosis (MTB)-specific CD4⁺ T cells at the site of infection and the increase of MTB-specific CD27^- cells seem to be characteristic for active tuberculosis. We evaluated CD27 expression of non-stimulated T cells at the site of infection compared to peripheral blood of seventy-two patients (n = 72) presenting with symptoms of active MTB-infection. Twenty patients (n = 20, 27.8%) were actually confirmed to have active tuberculosis. Overall, a significant increase of terminally differentiated CD27^- CD4⁺ T cells at the site of disease was noted when compared to peripheral blood (<0.001). However, the loss of CD27 at the site of disease was not restricted to active tuberculosis (p = 0.253). The CD27 expression profile of tuberculosis patients was only discriminative to patients with malignancy.

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.

Proportions of interferon-γ-producing ascites lymphocytes in response to mycobacterial antigens: A help for early diagnosis of peritoneal tuberculosis in a low TB incidence country

Background

Peritoneal tuberculosis (TB) remains difficult to diagnose because of its non-specific clinical features and the lack of efficient microbiological tests. As delayed diagnosis is associated with high mortality rates, new diagnostic tools are needed.

Methods and findings

We investigated for 24 patients prospectively enrolled with a possible diagnosis of peritoneal TB, the diagnostic value of the analysis of IFN-γ production by peritoneal fluid lymphocytes in response to a short in vitro stimulation with mycobacterial antigens. The patients were classified in two groups: non-TB and confirmed or highly probable TB. Diagnosis of TB was based on microbiological and histopathological criteria and/or a favorable response to anti-TB treatment. The IFN-γ production by peritoneal CD4⁺ T lymphocytes was analyzed by flow cytometry after an overnight in vitro stimulation with three different mycobacterial antigens, purified protein derivative (PPD), heparin-binding haemagglutinin (HBHA) or early-secreted-antigen-target-6 (ESAT-6). The percentages of PPD-, HBHA- or ESAT-6-induced IFN-γ-producing peritoneal fluid CD4⁺ T lymphocytes were higher in the TB group than in the non-TB group (p = 0.0007, p = 0.0004, and p = 0.0002 respectively). Based on cut-off values determined by ROC curve analysis of the results from TB and highly probable TB compared to those of non-TB patients, the sensitivity of these three tests was 100% with a specificity of 92%.

Conclusions

The analysis of mycobacterial-induced IFN-γ production by peritoneal lymphocytes is a promising tool to reliably and rapidly diagnose peritoneal TB. Further studies should be performed on larger cohorts of patients in high-TB-incidence countries to confirm the clinical value of this new diagnostic approach for peritoneal TB.

Diagnostic performance in active TB of QFT-Plus assay and co-expression of CD25/CD134 in response to new antigens of Mycobacterium tuberculosis

The new QuantiFERON-TB Gold Plus employs modified peptides optimized to elicit an IFNγ response from CD8⁺ cytotoxic T lymphocytes in addition to CD4⁺ T cells. With a view to improve the difficult identification of TB cases, we assessed the combination of two specific immunological markers comprising IFNγ secretion and T cells co-expression of CD25 and CD134 in response to Mycobacterium tuberculosis-specific antigens. A total of 34 subjects with suspected TB and 10 age-matched HD were prospectively enrolled. Assessing the performance of QFT-Plus in terms of the TB1 and TB2 results, we found that in TB patients, the quantitative IFNγ value in TB2 was similar to that in TB1, and we did not find any differences irrespective of the disease (pulmonary or extra-pulmonary). The flow cytometric CD25/CD134 assay, allowed a more accurate differentiation between M. tuberculosis-infected and uninfected patients, with a better combination of sensitivity and specificity, especially by evaluation of CD4⁺ T-cell subset. All individuals with negative QFT-Plus results displayed a positive CD25/CD134 response. Overall, a positive correlation was found between T cells co-expressing CD25/CD134 and IFNγ levels in response to both QFT-Plus TB antigen tubes, as well as between the QFT-Plus TB1 and TB2 tubes. We demonstrated that both TB1 and TB2 induce a higher expression of CD25⁺CD134⁺ markers on CD4⁺ T cells among infected TB subjects, compared to the lower degree of CD8⁺ T cells, mainly induced to TB2 stimulation. We suggest that a combined use of classic QFT-Plus and specific CD25/CD134 response may be a useful means in the diagnostic workup for active TB.

Rapid diagnosis of pulmonary tuberculosis by combined molecular and immunological methods

Diagnosing pulmonary tuberculosis (TB) may be delayed until culture results become available.We ascertained the accuracy of a stepwise diagnostic algorithm for the rapid diagnosis of pulmonary TB by GeneXpert from sputum and/or bronchoalveolar lavage (BAL) followed by a Mycobacterium tuberculosis-specific BAL ELISPOT assay in patients with a suspected diagnosis of pulmonary TB at a clinical referral centre in Germany.Among 166 patients with a presumptive diagnosis of pulmonary TB, 81 cases were confirmed by M. tuberculosis culture from sputum and/or BAL. In 66 out of 81 (81.5%) cases, patients initially had M. tuberculosis detected by GeneXpert from sputum; in addition, six out of 81 (7.4%) cases were diagnosed by GeneXpert on BAL fluid (together 72 out of 81 (88.9%) patients). Out of the remaining nine patients with negative GeneXpert results from sputum and BAL, BAL ELISPOT identified eight patients with culture-confirmed TB correctly (median time to culture positivity 26 days). At a cut-off of >4000 early secretory antigenic target-6- or culture filtrate protein-10-specific interferon-γ-producing lymphocytes per 1 000 0000 lymphocytes, the specificity of the BAL ELISPOT for active TB was 97%.In low TB incidence countries, nearly all patients with active pulmonary TB can be identified within the first few days of clinical presentation using a stepwise strategy with GeneXpert and BAL ELISPOT.

Assay for improved detection of antigen-specific immune cells from extrasanguinous fluids

In this approach, pre-stained cells from extrasanguinous fluids (ESFs) are stimulated in the presence of blood from the same individual. Thus, blood-derived antigen-presenting cells enable stimulation of both ESF- and blood T cells. Pre-staining allows distinction of T cells from ESF and blood, and simultaneous analysis of antigen-specific T cells in both compartments.

Evaluation of interferon-gamma release assays in extrasanguinous body fluids for diagnosing tuberculosis: A systematic review and meta-analysis

AIMS

In this study, we conducted a meta-analysis to systematically compare the diagnostic accuracy of IGRAs performed for extrasanguinous body fluids with that performed for blood in the diagnosis of TB.

MAIN METHODS

Multiple English and Chinese databases were searched up to November 2017. Studies that complied with the guidelines for the Quality Assessment of Diagnostic Accuracy Studies and used QuantiFERON-TB Gold In-Tube and/or T-SPOT.TB (ELISPOT) assays on both blood and extrasanguinous body fluids were included. Statistical analysis was performed using Stata 12.0 software. Since publication bias is a concern in the meta-analysis of diagnostic studies, we tested for this using Begg's funnel plots.

KEY FINDING

Among the 1332 articles searched from the databases, 24 articles met the inclusion criteria, which included 1040 samples in the patient group and 1044 samples in the control group. For extrasanguinous body fluids, the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC) area under the curve (AUC) were 87% (95% CI: 0.81-0.91), 89% (95% CI: 0.84-0.93), 8.22 (95% CI 5.38-12.56), 0.15 (95% CI: 0.10-0.21), 44.92 (95% CI: 25.61-78.81), and 0.94 (95% CI: 0.92-0.96), respectively. For peripheral blood, these values were 83% (95% CI: 0.79-0.87), 74% (95% CI: 0.68-0.79), 3.17 (95% CI 2.63-3.84), 0.23 (95% CI: 0.19-0.29), 12.99 (95% CI: 10.19-16.57), and 0.86 (95% CI: 0.82-0.89), respectively.

SIGNIFICANCE

IGRAs performed on extrasanguinous body fluids exhibited a better diagnostic accuracy compared with IGRAs performed on peripheral blood for diagnosing TB.

Pulmonary immune responses to Mycobacterium tuberculosis in exposed individuals

BACKGROUND

Blood based Interferon-(IFN)-γ release assays (IGRAs) have a poor predictive value for the development of tuberculosis. This study aimed to investigate the correlation between IGRAs and pulmonary immune responses in tuberculosis contacts in Germany.

METHODS

IGRAs were performed on bronchoalveolar lavage (BAL) cells and peripheral blood from close healthy contacts of patients with culturally confirmed tuberculosis. Cellular BAL composition was determined by flow cytometry. BAL cells were co-cultured with three strains of Mycobacterium tuberculosis (Mtb) and Mtb derived antigens including Purified Protein Derivative (PPD), 6 kD Early Secretory Antigenic Target (ESAT-6) and 10 kD Culture Filtrate Protein (CFP-10). Levels of 29 cytokines and chemokines were analyzed in the supernatants by multiplex assay. Associations and effects were examined using linear mixed-effects models.

RESULTS

There were wide variations of inter-individual cytokine levels in BAL cell culture supernatants. Mycobacterial infection and stimulation with PPD showed a clear induction of several macrophage and lymphocyte associated cytokines, reflecting activation of these cell types. No robust correlation between cytokine patterns and blood IGRA status of the donor was observed, except for slightly higher Interleukin-2 (IL-2) responses in BAL cells from IGRA-positive donors upon mycobacterial infection compared to cells from IGRA-negative donors. Stronger correlations were observed when cytokine patterns were stratified according to BAL IGRA status. BAL cells from donors with BAL IGRA-positive responses produced significantly more IFN-γ and IL-2 upon PPD stimulation and mycobacterial infection than cells from BAL IGRA-negative individuals. Correlations between BAL composition and basal cytokine release from unstimulated cells were suggestive of pre-activated lymphocytes but impaired macrophage activity in BAL IGRA-positive donors, in contrast to BAL IGRA-negative donors.

CONCLUSIONS

In vitro BAL cell cytokine responses to M. tuberculosis antigens or infection do not reflect blood IGRA status but do correlate with stronger cellular responses in BAL IGRA-positive donors. The cytokine patterns observed suggest a pre-activated state of lymphocytes and suppressed macrophage responsiveness in BAL cells from BAL IGRA-positive individuals.

Bronchoscopic techniques in the management of patients with tuberculosis

Tuberculosis (TB) is one of the leading causes of morbidity and mortality worldwide. Early diagnosis and treatment are key to prevent Mycobacterium tuberculosis transmission. Bronchoscopy can play a primary role in pulmonary TB diagnosis, particularly for suspected patients with scarce sputum or sputum smear negativity, and with endobronchial disease. Bronchoscopic needle aspiration techniques are accurate and safe means adopted to investigate hilar and mediastinal lymph nodes in cases of suspected TB lymphadenopathy. Tracheobronchial stenosis represents the worst complication of endobronchial tuberculosis. Bronchoscopic procedures are less invasive therapeutic strategies than conventional surgery to be adopted in the management of TB-related stenosis. We conducted a non-systematic review aimed at describing the scientific literature on the role of bronchoscopic techniques in the diagnosis and therapy of patients with TB. We focused on three main areas of interventions: bronchoscopic diagnosis of smear negative/sputum scarce TB patients, endobronchial TB diagnosis and treatment and needle aspiration techniques for intrathoracic TB lymphadenopathy. We described experiences on bronchoalveolar lavage, bronchial washing, and biopsy techniques for the diagnosis of patients with tracheobronchial and pulmonary TB; furthermore, we described the role played by conventional and ultrasound-guided transbronchial needle aspiration in the diagnosis of suspected hilar and mediastinal TB adenopathy. Finally, we assessed the role of the bronchoscopic therapy in the treatment of endobronchial TB and its complications, focusing on dilation techniques (such as balloon dilation and airway stenting) and ablative procedures (both heat and cold therapies).

CTLA-4-expression on VZV-specific T cells in CSF and blood is specifically increased in patients with VZV related central nervous system infections

VZV-reactivation may lead to symptomatic central nervous system (CNS) diseases, but identification of VZV as causative pathogen of CNS-diseases is challenging. This study was performed to characterize VZV-specific T cells from cerebrospinal fluid (CSF) and blood of patients with active CNS-disease and to determine whether this may improve differential diagnosis. 27 patients with pleocytosis in the CSF were recruited and classified into three groups (10 VZV-related, 10 non-VZV-related, 7 unclear). VZV-specific CD4⁺ T cells were quantified in CSF and blood after simultaneous stimulation with a VZV-antigen lysate and detection of cytokines (IFN-γ, IL-2, TNF-α) and CTLA-4. Polyclonal stimulation served as positive control. VZV-specific CD4⁺ T-cell frequencies were highest in both CSF (p = 0.0001) and blood (p = 0.011) of patients with VZV-infection, and were enriched at the site of infection (p = 0.002). While cytokine-expression profiles only showed minor differences between the groups, CTLA-4-expression levels on VZV-specific T cells from CSF and blood were significantly increased in VZV-related CNS-infections (p = 0.0002 and p<0.0001) and clearly identified VZV-related CNS-diseases (100% sensitivity and 100% specificity). Polyclonally stimulated T cells did not show any quantitative and phenotypical differences between the groups. Increased frequency and CTLA-4-expression of VZV-specific T cells from CSF or blood are specifically found in patients with VZV-related CNS-infection.

Interferon-Gamma Release Assay Performance of Cerebrospinal Fluid and Peripheral Blood in Tuberculous Meningitis in China

The aim of this study was to examine the performance of T-SPOT.TB on cerebrospinal fluid (CSF) and peripheral blood (PB) in diagnosis of tuberculous meningitis (TBM) in China. Of 100 patients with presumed TBM prospectively enrolled from Sep 2012 to Oct 2014, 53 were TBM (21 definite and 32 probable TBM cases) and 37 were non-TBM cases; the other 10 patients were excluded from analysis due to inconclusive diagnosis, no sufficient CSF samples, or incomplete follow-up. T-SPOT.TB on CSF and PB and routine laboratory tests of CSF were performed simultaneously. The receiver operating characteristic (ROC) curve and cut-off value of CSF T-SPOT.TB and routine CSF parameters were established between TBM and non-TBM group. The area under ROC curve (AUC) of the T-SPOT.TB on CSF and PB was 0.81 and 0.89, which was higher than that of the routine CSF parameters (AUC 0.67–0.77). Although the sensitivity of CSF T-SPOT.TB was lower than that of PB T-SPOT.TB (60.8% versus 90.6%, P < 0.001), the specificity of CSF T-SPOT.TB was significantly higher than that of PB T-SPOT.TB (97.2% versus 75.7%, P = 0.007). These results indicated that the diagnostic accuracies of PB and CSF T-SPOT.TB are higher than routine laboratory tests. Furthermore, the higher specificity of CSF T-SPOT.TB makes it a useful rule-in test in rapid diagnosis of TBM.

Positive predictive value of ELISpot in BAL and pleural fluid from patients with suspected pulmonary tuberculosis

BACKGROUND

The aim of this study was to evaluate the positive predictive value (PPV) of ELISpot in bronchoalveolar lavage (BAL) and pleural fluid for the diagnosis of active tuberculosis (TB) in real-life clinical practice, together with the added value of a cut-off >1.0 for the ratio between the extra-sanguineous and systemic interferon-gamma responses in positive samples.

METHODS

A retrospective, single-centre study was performed. Patients with positive ELISpot in BAL and pleural fluid were included.

RESULTS

The PPV for TB in patients with positive ELISpot in BAL (n = 40) was 64.9%, which increased to 82.6% for the ESAT-6 panel and 71.4% for the CFP-10 panel after the introduction of a cut-off >1.0 for the ratio between the BAL and blood interferon-gamma responses. In patients with positive ELISpot in pleural fluid (n = 16), the PPV for TB was 85.7%, which increased to 91.7% for the ESAT-6 panel and 92.3% for the CFP-10 panel after the introduction of a cut-off >1.0 for the ratio between the pleural fluid and blood interferon-gamma responses.

CONCLUSIONS

This report describes the PPV of ELISpot in BAL and pleural fluid for the diagnosis of active TB in real-life clinical practice. The results indicate the possibility of an increase of the PPV using a cut-off >1.0 for the ratio between the extra-sanguineous and systemic interferon-gamma responses. Further studies are needed to underline this ratio-approach and to evaluate the full diagnostic accuracy of ELISpot in extra-sanguineous fluids like BAL and pleural fluid.

Multifunctional T Cell Response to DosR and Rpf Antigens Is Associated with Protection in Long-Term Mycobacterium tuberculosis-Infected Individuals in Colombia

Multifunctional T cells have been shown to be protective in chronic viral infections. In mycobacterial infections, however, evidence for a protective role of multifunctional T cells remains inconclusive. Short-term cultures of peripheral blood mononuclear cells stimulated with the Mycobacterium tuberculosis RD1 antigens 6-kDa early secretory antigenic target (ESAT6) and 10-kDa culture filtrate antigen (CFP10), which are induced in the early infection phase, have been mainly used to assess T cell multifunctionality, although long-term culture assays have been proposed to be more sensitive than short-term assays for assessment of memory T cells, which are essential for long-term immunity. Here we used a long-term culture assay system to study the T cell immune responses to the M. tuberculosis latency-associated DosR antigens and reactivation-associated Rpf antigens, compared to ESAT6 and CFP10, in patients with pulmonary tuberculosis (PTB) and household contacts of PTB patients with long-term latent tuberculosis infection (ltLTBI), in a community in which M. tuberculosis is endemic. Our results showed that the DosR antigens Rv1737c (narK2) and Rv2029c (pfkB) and the Rv2389c (rpfD) antigen of M. tuberculosis induced higher frequencies of CD4⁺ or CD8⁺ mono- or bifunctional (but not multifunctional) T cells producing interferon gamma (IFN-γ) and/or tumor necrosis alpha (TNF-α) in ltLTBI, compared to PTB. Moreover, the frequencies of CD4⁺ and/or CD8⁺ T cells with a CD45RO⁺ CD27⁺ phenotype were higher in ltLTBI than in PTB. Thus, the immune responses to selected DosR and Rpf antigens may be associated with long-term latency, correlating with protection from M. tuberculosis reactivation in ltLTBI. Further study of the functional and memory phenotypes may contribute to further discrimination between the different states of M. tuberculosis infections.

Accuracy of the Bronchoalveolar Lavage Enzyme-Linked Immunospot Assay for the Diagnosis of Pulmonary Tuberculosis: A Meta-analysis

Assessing of local immune response may improve the accuracy of pulmonary tuberculosis (PTB) diagnosis. Many studies have investigated diagnosing PTB based on enzyme-linked immunospot (ELISPOT) assay of bronchoalveolar lavage (BAL) fluid, but the results have been inconclusive. We meta-analyzed the available evidences on overall diagnostic performance of ELISPOT assay of BAL fluid for diagnosing PTB.A systematic literature search was performed using PubMed, Embase, Wangfang, Weipu, and CNKI. Data were pooled on sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR). Overall test performance was summarized using summary receiver operating characteristic curves and the area under the curve (AUC). Deeks test was used to test for potential publication bias.Seven publications with 814 subjects met our inclusion criteria and were included in this meta-analysis. The following pooled estimates for diagnostic parameters were obtained: sensitivity, 0.90 (95% CI: 0.85-0.94); specificity, 0.80 (95% CI: 0.77-0.84); PLR, 5.08 (95% CI: 2.70-9.57); NLR, 0.13 (95% CI: 0.06-0.28); DOR, 49.12 (95% CI: 12.97-186.00); and AUC, 0.96. No publication bias was identified.The available evidence suggests that ELISPOT assay of BAL fluid is a useful rapid diagnostic test for PTB. The results of this assay should be interpreted in parallel with clinical findings and the results of conventional tests.

Dynamics of the T cell response to Mycobacterium tuberculosis DosR and Rpf antigens in a Colombian population of household contacts of recently diagnosed pulmonary tuberculosis patients

Immune response to DosR and Rpf antigens from Mycobacterium tuberculosis (Mtb) seems to be important for latency maintenance. Little is known about the dynamics of the immune response to these antigens in an endemic community. Thus, the IFNγ response and cytokine production in response to PPD, Esat6-Cfp10 (E6-C10), DosR and Rpf antigens in healthy HHC of tuberculosis (TB) patients over a 12 (T12) months period (short-term, stLTBI) was investigated. This response was compared with a group of LTBI, who have remained healthy for 5-7 years (long-term, ltLTBI). According to the IFNγ response, two groups of HHCs were identified in stLTBI in response to E6-C10. At T12, E6-C10(+) HHCs displayed a decrease in the IFNγ levels and a generalized decrease in cytokines production. The E6-C10(-) HHC showed an increase in the IFNγ response and cytokine levels. In stLTBI, the responses to E6-C10, DosR, and Rpf may be interpreted as a protective immune response controlling Mtb infection and may be leading to a state of latent infection. Comparing the response of stLTBI and ltLTBI, we observed significant changes in the proportions of CD45RO(+)CD27(+) T cells to specific DosR and Rpf, which may indicate a persistent immune response to Mtb antigens in ltLTBI.

Cytokine and Antibody Based Diagnostic Algorithms for Sputum Culture-Positive Pulmonary Tuberculosis

Background

Tuberculosis (TB) is one of the most serious infectious diseases globally and has high mortality rates. A variety of diagnostic tests are available, yet none are wholly reliable. Serum cytokines, although significantly and frequently induced by different diseases and thus good biomarkers for disease diagnosis and prognosis, are not sufficiently disease-specific. TB-specific antibody detection, on the other hand, has been reported to be highly specific but not sufficiently sensitive. In this study, our aim was to improve the sensitivity and specificity of TB diagnosis by combining detection of TB-related cytokines and TB-specific antibodies in peripheral blood samples.

Methods

TB-related serum cytokines were screened using a human cytokine array. TB-related cytokines and TB-specific antibodies were detected in parallel with microarray technology. The diagnostic performance of the new protocol for active TB was systematically compared with other traditional methods.

Results

Here, we show that cytokines I-309, IL-8 and MIG are capable of distinguishing patients with active TB from healthy controls, patients with latent TB infection, and those with a range of other pulmonary diseases, and that these cytokines, and their presence alongside antibodies for TB-specific antigens Ag14-16kDa, Ag32kDa, Ag38kDa and Ag85B, are specific markers for active TB. The diagnostic protocol for active TB developed here, which combines the detection of three TB-related cytokines and TB-specific antibodies, is highly sensitive (91.03%), specific (90.77%) and accurate (90.87%).

Conclusions

Our results show that combining detection of TB-related cytokines and TB-specific antibodies significantly enhances diagnostic accuracy for active TB, providing greater accuracy than conventional diagnostic methods such as interferon gamma release assays (IGRAs), TB antibody Colloidal Gold Assays and microbiological culture, and suggest that this diagnostic protocol has potential for clinical application.

Pulmonary responses to pathogen-specific antigens in latent Mycobacterium tuberculosis infection

In this study, we used ELISPOT to quantify frequencies of bronchoalveolar lavage (BAL) and peripheral blood T cells capable of producing IFNγ in response to PPD, antigen 85B, and Mtb-specific antigens CFP-10 and ESAT-6 in individuals with latent tuberculosis infection (LTBI) and Mtb-naïve controls. Compared to peripheral blood, BAL cells of LTBI subjects displayed significant enrichment for T cells responding to PPD, antigen 85B, and CFP-10, but not to ESAT-6. Baseline BAL cells of LTBI subjects displayed significant production of Mig (CXCL9) in response to PPD, antigen 85B, and CFP-10 as well. These findings suggest that enrichment for Mtb-specific T cells within BAL is not unique to active pulmonary tuberculosis and may, to the contrary, contribute to protection from re-infection in Mtb immune individuals.

Role of bronchoalveolar lavage in the diagnosis of pulmonary infiltrates in immunocompromised patients

PURPOSE OF REVIEW

To describe the role of bronchoalveolar lavage (BAL) in the evaluation of pulmonary disease in immunocompromised patients.

RECENT FINDINGS

Recent discoveries in this field are largely in two areas: the array of diagnostic testing performed on BAL fluid and technical details that can enhance the yield from this procedure. Regarding diagnostic testing, the addition of new assays, including Aspergillus galactomannan antigen assay, respiratory viral panels, and Pneumocystis jirovecii PCR, has improved the diagnostic yield of BAL over conventional cultures and stains. To improve the diagnostic yield of the procedure itself, it should be done early in the clinical course, with the BAL in the anatomic area most affected, and with a preprocedural computed tomography of the chest to properly plan the procedure.

SUMMARY

Bronchoscopic evaluation with BAL can provide important diagnostic information in immunocompromised patients with pulmonary diseases and should be routinely performed when clinically indicated and able to be completed safely.

Accuracy of bronchoalveolar lavage enzyme-linked immunospot assay to diagnose smear-negative tuberculosis: a meta-analysis

PURPOSE

While the bronchoalveolar lavage enzyme-linked immunospot assay (BAL-ELISPOT) shows promise for diagnosing smear-negative tuberculosis, its accuracy remains controversial. We meta-analyzed the available evidence to obtain a clearer understanding of the diagnostic accuracy.

METHODS

Studies of the diagnostic performance of ELI-SPOT on smear-negative tuberculosis were identified through systematic searches of the PubMed and EMBASE databases. Pooled data on sensitivity, specificity and other measures of accuracy were meta-analyzed using a random-effects model. Summary receiver operating characteristic curves were used to assess overall test performance.

RESULTS

A total of 7 studies were included in the meta-analysis. Diagnostic performance was as follows: sensitivity, 0.89 (95% CI 0.84 to 0.93); specificity, 0.78 (95% CI 0.74 to 0.81); positive likelihood ratio, 4.2 (95% CI 2.42 to 7.28); negative likelihood ratio, 0.14 (95% CI 0.06 to 0.33); diagnostic odds ratio, 36.16 (95% CI 9.70 to 134.73); and area under the curve, 0.9605 (SEM 0.0247).

CONCLUSIONS

Available evidence suggests that BAL-ELISPOT may perform better than blood-ELISPOT for both screening and confirming a diagnosis of smear-negative tuberculosis. Nevertheless, BAL-ELISPOT should be not used alone but rather in parallel with clinical manifestations and conventional tests to ensure reliable diagnosis.

Diagnostic value of nucleic acid amplification tests on bronchoalveolar lavage fluid for smear-negative pulmonary tuberculosis: a meta-analysis

Based on current available evidence, NAAT on BALF plays a role in the diagnosis of smear-negative pulmonary tuberculosis, and further studies should be performed to confirm our findings..

The diagnosis of smear-negative pulmonary tuberculosis (SNPT) remains a clinical challenge. Many studies suggest that nucleic acid amplification tests (NAATs) on bronchoalveolar lavage fluid (BALF) plays a role in diagnosing SNPT, but with considerable varying results. The current study aimed to summarize the overall diagnostic accuracy of NAATs assay on BALF for SNPT. A systematic literature search was performed and data were retrieved. Pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR) and diagnostic odds ratio (DOR) were calculated. A summary receiver operating characteristic curve and area under the curve (AUC) were used to evaluate the overall diagnostic performance. All the statistical analysis was performed by using STATA 12.0 and Meta-DiSc 1.4 software. A total of nine studies with 1214 subjects were included this meta-analysis. The pooled sensitivity, specificity, PLR, NLR and DOR were 0.54 [95% CI (confidence interval): 0.48–0.59], 0.97 (95% CI: 0.95–0.98), 12.13 (95% CI: 8.23–17.88), 0.36 (95% CI: 0.23–0.56) and 44.71 (95% CI: 22.30–89.63) respectively. The AUC was 0.96. Estimated positive and negative post-probability values for a SNPT prevalence of 20% were 82% and 7% respectively. No publication bias was identified. Current available evidence indicated that NAATs on BALF may play a role in diagnosing SNPT, whereas the results should be interpreted in parallel with clinical information of patients and the results of traditional tests. Further studies should be performed to confirm our findings.

Diagnostic values of the QuantiFERON-TB Gold In-tube assay carried out in China for diagnosing pulmonary tuberculosis

BACKGROUND

Interferon-release assays (IGRAs) for diagnosing active pulmonary tuberculosis (PTB) are not yet fully validated, particularly in high TB-endemic areas as the People's Republic of China (PRC). The aim of this report was to assess the performance of the QuantiFERON-TB Gold In-tube (QFT-GIT) and tuberculin skin test (TST), in addition to microbiological results, as contributors for diagnosing active PTB in the PRC.

METHODS/PRINCIPAL FINDINGS

A total of 300 PTB patients, 41 disease controls (DC) and 59 healthy community controls (HCC) were included prospectively between May 2010 and April 2011 from two provinces of the PRC (Heilongjiang and Zhejiang). The QFT-GIT and TST yielded an overall sensitivity for active TB of 80.9% and 86.2%, and a specificity of 36.6% and 26.8%, respectively. The province of origin and smear microscopy status did not significantly impact the diagnostic values for PTB. However, using the TST with a 10 mm cut-off point, a significantly higher proportion of LTBI was observed in the DC than the HCC (p=0.01). Discordant results between the QFT-GIT and TST were found among 1/3 of the PTB, HCC and DC. Two-thirds of the individuals presented TST-positive/QFT-GIT-negative discordant results. The TST-negative/QFT-GIT-positive result was not associated with age or bacillary load. Cumulative QFT-GIT and TST positive results increased the overall sensitivity (95.9%), but it was associated with a dramatic decrease of the overall specificity (24.8%) leading to a suboptimal PPV (80.1%) and a low NPV (61.1%).

CONCLUSIONS/SIGNIFICANCE

The usefulness of the QFT-GIT to diagnose active TB in high TB-endemic countries remains doubtful because like the TST, the QFT-GIT cannot distinguish between LTBI and active TB. Used as single stand-alone tests, both the QFT-GIT and TST have very limited roles in the diagnosis of active PTB. However, the combined use of SM, the TST and QFT-GIT may allow for the exclusion of ATB.

Combined antigen-specific interferon-γ and interleukin-2 release assay (FluoroSpot) for the diagnosis of Mycobacterium tuberculosis infection

BACKGROUND

To evaluate interleukin (IL)-2 and interferon (IFN)-γ secreting T-cells in parallel for the differentiation of latent infection with Mycobacterium tuberculosis infection (LTBI) from active tuberculosis.

METHODS

Following ex-vivo stimulation of peripheral blood mononuclear cells (PBMC) with M. tuberculosis-specific antigens early secretory antigenic target (ESAT)-6 and culture filtrate protein (CFP)-10, immune responses were assessed by enzyme-linked immunospot IFN-γ release assay (EliSpot-IGRA) and a novel dual cytokine detecting fluorescence-linked immunospot (FluoroSpot) in 18 patients with pulmonary tuberculosis, 10 persons with previously cured tuberculosis, 25 individuals with LTBI and 16 healthy controls.

RESULTS

Correlation of IFN-γ+ spot-forming cells in EliSpot-IGRA and FluoroSpot were R2 = 0.67 for ESAT-6 and R2 = 0.73 for CFP-10. The number of IL-2- IFN-γ+ producing cells was higher in patients with tuberculosis compared with past tuberculosis (CFP-10-induced p = 0.0068) or individuals with LTBI (ESAT-6-induced p = 0.0136). A cutoff value of >16 CFP-10-induced IFN-γ+ secreting cells/200.000 PBMC in the EliSpot-IGRA discriminated with highest sensitivity and specificity (89% and 76%, respectively). However, overlap in cytokine responses precludes distinction between the cohorts on an individual basis.

CONCLUSIONS

Combined analysis of IFN-γ and IL-2 secretion by antigen specific T-cells does not allow a reliable differentiation between different states of M. tuberculosis infection in clinical practice.

Potential role of immunodiagnosis for pulmonary tuberculosis using induced sputum cells

PURPOSE

To evaluate the diagnostic utility and predictors for determinate results of an enzyme-linked immunospot assay using induced sputum cells (IS ELISPOT) for a rapid diagnosis of pulmonary tuberculosis (TB).

MATERIALS AND METHODS

Subjects suspected of pulmonary TB who had either sputum acid fast bacilli smear-negative or not producing sputum spontaneously were prospectively enrolled. ELISPOT assay was performed using cells from induced sputum.

RESULTS

A total of 43 subjects, including 25 with TB (TB group) and 18 with non-TB disease (non-TB group) were enrolled. Results of IS ELISPOT were determinate in only 17/43 (39%) subjects, but all of determinate results were consistent with the final diagnosis. Of the 43 sputum samples, 11 (26%) were inadequate to perform IS ELISPOT. Of 32 adequate sputum samples, the proportion of determinate results was significantly higher in the TB group (75%, 15/20) than in the non-TB group (17%, 2/12) (p=0.002). The status of active TB was a unique predictor but smear positivity was not a significant predictor for determinate results. In addition, sensitivity of IS ELISPOT (75%, 9/12) in smear negative TB was higher than that of TB-polymerase chain reaction (25%, 3/12).

CONCLUSION

IS ELISPOT showed relatively high diagnostic value and accuracy in the TB group, independent of smear positivity. IS ELISPOT may provide additional diagnostic yield for microbiological tools in the rapid diagnosis of smear-negative TB.

Variability in tuberculosis granuloma T cell responses exists, but a balance of pro- and anti-inflammatory cytokines is associated with sterilization

Lung granulomas are the pathologic hallmark of tuberculosis (TB). T cells are a major cellular component of TB lung granulomas and are known to play an important role in containment of Mycobacterium tuberculosis (Mtb) infection. We used cynomolgus macaques, a non-human primate model that recapitulates human TB with clinically active disease, latent infection or early infection, to understand functional characteristics and dynamics of T cells in individual granulomas. We sought to correlate T cell cytokine response and bacterial burden of each granuloma, as well as granuloma and systemic responses in individual animals. Our results support that each granuloma within an individual host is independent with respect to total cell numbers, proportion of T cells, pattern of cytokine response, and bacterial burden. The spectrum of these components overlaps greatly amongst animals with different clinical status, indicating that a diversity of granulomas exists within an individual host. On average only about 8% of T cells from granulomas respond with cytokine production after stimulation with Mtb specific antigens, and few “multi-functional” T cells were observed. However, granulomas were found to be “multi-functional” with respect to the combinations of functional T cells that were identified among lesions from individual animals. Although the responses generally overlapped, sterile granulomas had modestly higher frequencies of T cells making IL-17, TNF and any of T-1 (IFN-γ, IL-2, or TNF) and/or T-17 (IL-17) cytokines than non-sterile granulomas. An inverse correlation was observed between bacterial burden with TNF and T-1/T-17 responses in individual granulomas, and a combinatorial analysis of pair-wise cytokine responses indicated that granulomas with T cells producing both pro- and anti-inflammatory cytokines (e.g. IL-10 and IL-17) were associated with clearance of Mtb. Preliminary evaluation suggests that systemic responses in the blood do not accurately reflect local T cell responses within granulomas.

The characteristic feature of Mycobacterium tuberculosis (Mtb) infection is the formation of lesions, which are organized structures of immune cells in the lungs called granulomas, which contain the bacteria. When the granuloma functions effectively, it can kill the bacteria. T cells (a type of immune cell, also present in granulomas) are known to play an important role in control of tuberculosis. However, functions of T cells at individual granuloma levels are unknown. Here, we studied the functional characteristics of T cells, which are defined by the production of chemical messengers (cytokines) at the granuloma level in a non-human primate model. We compared the relationship between cytokine response and the number of bacteria (Mtb) in each granuloma. Each granuloma was found to be unique, suggesting different types exist within an animal. Only a small proportion of T cells produced any cytokine, but different types of cytokines were observed within each granuloma. A balance between different types of cytokine was associated with more killing of bacteria in granulomas. Understanding how to improve the T cell responses to obtain killing of bacteria in the granuloma will be important for vaccine development.

A rapid and non-invasive 2-step algorithm for diagnosing tuberculous peritonitis using a T cell-based assay on peripheral blood and peritoneal fluid mononuclear cells together with peritoneal fluid adenosine deaminase

OBJECTIVES

A recently developed RD-1 gene-based assay for diagnosing tuberculous peritonitis (TBP) has given promising results. We therefore created a clinical algorithm for differentiating TBP from other diagnoses using peripheral blood and peritoneal fluid mononuclear cells (PBMC/PF-MC) along with conventional tests.

METHODS

All adult patients with suspected TBP in whom enzyme-linked immunosorbent spot (ELISPOT) assays were performed both on PBMC and PF-MC were prospectively enrolled over a 6-year period. Confirmed TBP with positive cultures or Mycobacterium tuberculosis PCR, probable TBP with PF changes consistent with TBP, caseating granuloma, and a successful response to anti-TB therapy, as well as possible TBP without exclusion of TBP, were each defined.

RESULTS

A total of 74 patients were enrolled. Of these, 45 (61%) (19 confirmed, 16 probable, and 10 possible) were classified as TBP. The other 29 (39%) patients were classified as not TB. The sensitivity and specificity, respectively, of the tested methods for diagnosing TBP were as follows: PBMC ELISPOT (≥6 spots), 84% and 59%; PF-MC ELISPOT (≥6 spots), 87% and 86%; PF-MC/PBMC ratio (≥3), 69% and 97%; and PF-ADA level (≥21 U/L), 82% and 79%. The areas under the ROC curves were as follows: PF-MC ELISPOT, 0.90; PF-MC/PBMC ratio, 0.82; PBMC ELISPOT, 0.80; and PF-ADA, 0.80, respectively. When a 2-step algorithm ('PBMC ELISPOT ≥6 spots or PF-ADA ≥21 U/L' as a rule-out test and 'PF-MC/PBMC ratio ≥3' as a rule-in test) was applied, 67% (30/45) of the patients with TBP were accurately classified without undergoing invasive procedures.

CONCLUSIONS

A 2-step algorithm using the PBMC/PF-MC ELISPOT assays and PF-ADA appears to be a promising rapid and non-invasive approach for diagnosing TBP.

[Tuberculosis]

Tuberculosis (TB) continues to be an important public health problem. Currently, 2,100 million people--one third of the world population--are infected by Mycobacterium tuberculosis, with an estimated annual rate of 9.4 million new cases, and 440,000 cases of multidrug-resistant (MDR) TB in 2008; furthermore, cases of extensively-resistant (XDR) TB have been detected in 57 countries. While TB cases are constantly declining in industrialized countries, the rates and mortality due to this infection in developing countries remain alarming and will continue to be so in the future. Although the priorities in these countries are at present simpler, methods allowing rapid diagnosis of TB and of resistant strains will obviously contribute to better control of the disease. Nucleic acid amplification techniques allow M. tuberculosis detection in clinical samples in a few hours, while liquid media cultures may yield positive results in only 2 to 4 weeks, half the time that is usually required for growth in conventional solid media, which also allows more rapid determination of drug susceptibilities. Similarly, based on molecular biology, several approaches may rapidly identify gene mutations associated with resistance to antituberculosis drugs in clinical samples. Finally, the main obstacle to treatment adherence among patients--its length--could be minimized in the future if the new combinations of drugs currently under investigation, and some promising new vaccines, confirm similar rates of efficacy to those used at present.

Inactive fibrotic lesions versus pulmonary tuberculosis with negative bacteriology

This article analyzes the concept of inactive fibrotic lesions of presumed tuberculous origin (old healed tuberculosis), defined by radiological characteristics and a positive tuberculin skin test (TST), and we examine the evidence-based foundation for the indication of treatment of latent tuberculosis infection in these cases. We explore the risk of reactivation in older and recent literature, and the problems raised by the differential diagnosis with active tuberculosis with negative bacteriology. We also analyze data on the prevalence of fibrotic lesions in the recent literature. We examine the possible role of Interferon Gamma Release Assays (IGRAs) versus TST and other molecular antigen detection techniques in sputum that can aid in establishing the diagnosis and we discuss the current indications for chemoprophylaxis and the different options available. We propose diagnostic guidelines and therapeutic algorithms based on risk stratification by age and other factors in the management of radiological lesions that raise a differential diagnosis between fibrotic lesions and active pulmonary tuberculosis with negative bacteriology.

Interferon-gamma release assay performance of pleural fluid and peripheral blood in pleural tuberculosis

Background

The diagnosis of pleural tuberculosis (TB) remains to be difficult. Interferon-gamma release assay (IGRA) is a promising method for diagnosing TB in low TB burden countries. The release of interferon-gamma (IFN-γ) by T lymphocytes increases at a localized site of infection with Mycobacterium tuberculosis antigen. This study aimed to examine the clinical accuracy of T-SPOT.TB on pleural fluid and peripheral blood for the diagnosis of pleural TB in high TB burden country.

Methods

168 subjects with pleural effusion were enrolled prospectively and examined with T-SPOT.TB on pleural fluid and peripheral blood samples simultaneously.

Results

The receiver operating characteristic (ROC) curve and cut-off value of pleural fluid T-SPOT.TB was established according to spot forming cells (SFC) between culture/biopsy-confirmed pleural TB group and no pleural TB group. The sensitivity of pleural fluid T-SPOT.TB and peripheral blood T-SPOT.TB was similar (96.3% and 92.7%, respectively) (P= 0.691). In contrast, the specificity of pleural fluid T-SPOT.TB (94.5%) was significantly higher than that of peripheral blood T-SPOT.TB (76.1%) (P=0.002). 2% (2/98) of pleural fluid T-SPOT.TB results were indeterminate.

Conclusion

The diagnostic accuracy of peripheral blood T-SPOT.TB is low in high TB burden countries due to latent tuberculosis infection. Pleural fluid T-SPOT.TB is a relatively useful and supplementary test to explore pleural TB in high TB burden countries, but its diagnostic accuracy needs to be validated in further large scale research.

TB or not TB: the role of immunodiagnosis

The evaluation of delayed-type hypersensitivity immune responses by the tuberculin skin test and, more recently, by ex vivo IFN-γ release assays (IGRAs) form the basis for the risk assessment for the development of tuberculosis (TB) in close contacts of infective index patients and in immunocompromised hosts. In contrast, immunodiagnosis has little value for the diagnosis of active TB so far. A report in this issue of the European Journal of Immunology [Eur J Immunol 2012. 42: 2844-2850] provides new insight into the phenotypic characteristics and selective recruitment of Ag-specific T cells to the site of the infection, as analyzed by flow cytometry, which may provide new opportunities for the immune-based diagnosis of TB in the future.

TBNET - Collaborative research on tuberculosis in Europe

Networking is a key feature of scientific success. The Tuberculosis Network European Trialsgroup (TBNET) was founded in 2006 as a non-profit, non-governmental peer-initiated scientific organization to collaboratively address research priorities in the area of tuberculosis in Europe. Today, TBNET is the largest tuberculosis research organization in Europe with nearly 500 members from 22 EU countries and 49 countries worldwide (www.tb-net.org). Apart from small multicenter basic research studies, a particular strength of TBNET is the performance of large collaborative projects, pan-European multicenter studies and database projects. In recent years, research from TBNET has substantially contributed to the understanding of the management, risk and prognosis of patients with multidrug (MDR) and extensively drug-resistant (XDR) tuberculosis and led to a better understanding of the clinical value of novel tests for the identification of adults and children with tuberculosis and latent infection with Mycobacterium tuberculosis. In 2009, two branches of TBNET were founded to specifically address tuberculosis in the pediatric population (ptbnet) and non-tuberculous mycobacterial diseases (NTM-NET). In addition to the research activities, TBNET is developing expert consensus documents for clinical management and provides training and capacity building especially for members from Eastern European countries, where tuberculosis is still a prevalent health problem.

BCG-specific IgG-secreting peripheral plasmablasts as a potential biomarker of active tuberculosis in HIV negative and HIV positive patients

Background

Diagnosis of active tuberculosis (TB) among sputum-negative cases, patients with HIV infection and extra-pulmonary TB is difficult. In this study, assessment of BCG-specific IgG-secreting peripheral plasmablasts, was used to identify active TB in these high-risk groups.

Methods

Peripheral blood mononuclear cells were isolated from patients with TB and controls and cultured in vitro using an assay called Antibodies in Lymphocyte Supernatant, which measures spontaneous IgG antibody release from migratory plasmablasts. A BCG-specific ELISA and flow cytometry were used to quantify in vivo activated plasmablasts in blood samples from Ethiopian subjects who were HIV negative or HIV positive. Patients diagnosed with different clinical forms of sputum-negative active TB or other diseases (n=96) were compared with asymptomatic individuals including latent TB and non-TB controls (n=85). Immunodiagnosis of TB also included the tuberculin skin test and the interferon (IFN)-γ release assay, QuantiFERON.

Results

This study demonstrated that circulating IgG+ plasmablasts and spontaneous secretion of BCG-specific IgG antibodies were significantly higher in patients with active TB compared with latent TB cases and non-TB controls. BCG-specific IgG titres were particularly high among patients coinfected with TB and HIV with CD4 T-cell counts <200 cells/ml who produced low levels of Mycobacterium tuberculosis-specific IFNγ in vitro.

Conclusions

These results suggest that BCG-specific IgG-secreting peripheral plasmablasts could be successfully used as a host-specific biomarker to improve diagnosis of active TB, particularly in people who are HIV positive, and facilitate administration of effective treatment to patients. Elevated IgG responses were associated with impaired peripheral T-cell responses, including reduced T-cell numbers and low M tuberculosis-specific IFNγ production.

Bronchoalveolar lavage enzyme-linked immunospot for diagnosis of smear-negative tuberculosis in HIV-infected patients

Background

Peripheral blood interferon-gamma release assays (IGRAs) have sub-optimal sensitivity and specificity for diagnosis of active pulmonary tuberculosis (TB). However, assessment of local immune responses has been reported to improve the accuracy of TB diagnosis.

Methods

We enrolled HIV-infected adults with cough ≥2 weeks’ duration admitted to Mulago Hospital in Kampala, Uganda and referred for bronchoscopy following two negative sputum acid-fast bacillus smears. We performed an ELISPOT-based IGRA (T-SPOT.TB®, Oxford Immunotec, Oxford, UK) using peripheral blood and bronchoalveolar lavage (BAL) fluid mononuclear cells, and determined the accuracy of IGRAs using mycobacterial culture results as a reference standard.

Results

94 HIV-infected patients with paired peripheral blood and BAL IGRA results were included. The study population was young (median age 34 years [IQR 28–40 years]) and had advanced HIV/AIDS (median CD4+ T-lymphocyte count 60 cells/µl [IQR 22–200 cells/µl]). The proportion of indeterminate IGRA results was higher in BAL fluid than in peripheral blood specimens (34% vs. 14%, difference 20%, 95% CI 7–33%, p = 0.002). BAL IGRA had moderate sensitivity (73%, 95% CI 50–89%) but poor specificity (48%, 95% CI 32–64%) for TB diagnosis. Sensitivity was similar (75%, 95% CI 57–89%) and specificity was higher (78%, 95% CI 63–88%) when IGRA was performed on peripheral blood.

Conclusions

BAL IGRA performed poorly for the diagnosis of smear-negative TB in a high HIV/TB burden setting. Further studies are needed to examine reasons for the large proportion of indeterminate results and low specificity of BAL IGRA for active TB in high HIV/TB burden settings.

Added value of use of a purified protein derivative-based enzyme-linked immunosorbent spot assay for patients with Mycobacterium bovis BCG infection after intravesical BCG instillations

In this case series, we describe four cases in which the use of gamma interferon release assays with purified protein derivative (PPD) as a stimulating antigen was able to demonstrate PPD-specific immune activation. This may help to improve the adequate diagnosis of (systemic) Mycobacterium bovis BCG infections after intravesical BCG instillations for bladder carcinoma.

IP-10 is an additional marker for tuberculosis (TB) detection in HIV-infected persons in a low-TB endemic country

OBJECTIVE

In Indian HIV-infected patients, IP-10 response to QuantiFERON-TB Gold In tube (QFT-IT) antigens has been associated to tuberculosis (TB). However, specificity for active TB was lower than that reported by QFT-IT, making accuracy for TB detection questionable. To investigate this uncertainty, likely due to India being highly endemic for TB, and to better identify TB correlates, we evaluated the IP-10-based assay in HIV-infected subjects in Italy, a low-TB endemic country.

METHODS

195 individuals were prospectively enrolled; 118 were HIV-infected (21 with active TB, 97 without active TB, and distinguished as high/low-TB-risk). QFT-IT was performed and IP-10 was evaluated by ELISA.

RESULTS

Among the HIV-infected individuals, sensitivity for active TB was 66.7% by IP-10-based test and 52.4% (p = 1) by QFT-IT. IP-10-based assay showed a lower dependence on mitogen-response and CD4 counts than QFT-IT. Among subjects without active TB, a higher proportion of IP-10 responders was shown in high-TB-risk subjects than low-TB-risk subjects (40.0% vs 12.9%), similar to QFT-IT (37.1% vs 4.8%). Low-TB risk subjects showed 87.1% specificity for active TB by IP-10-based test vs 95.2% by QFT-IT.

CONCLUSIONS

In a low-TB endemic country, besides IFN-γ, IP-10 response to QFT-IT is associated with active TB and TB risk factors in HIV-infected patients with lower dependence on mitogen-response and CD4 counts.

Local immune responses in human tuberculosis: learning from the site of infection

Host-pathogen interactions in tuberculosis should be studied at the disease site because Mycobacterium tuberculosis is predominately contained in local tissue lesions. Although M. tuberculosis infection involves different clinical forms of tuberculosis, such as pulmonary tuberculosis, pleural tuberculosis, and lymph node tuberculosis, most studies of human tuberculosis are performed using cells from the peripheral blood, which may not provide a proper reflection of the M. tuberculosis-specific immune responses induced at the local site of infection. A very low proportion of M. tuberculosis-specific effector T cells are found in the blood compared with the infected tissue, and thus there may be considerable differences in the cellular immune response and regulatory mechanisms induced in these diverse compartments. In this review, we discuss differences in the immune response at the local site of infection compared with the peripheral circulation. The cell types and immune reactions involved in granuloma formation and maintenance as well as the in situ technologies used to assess local tuberculosis pathogenesis are also described. We need to strengthen and improve the exploratory strategies used to dissect immunopathogenesis in human tuberculosis with the aim to accelerate the implementation of relevant research findings in clinical practice.

HIV-1 infection alters CD4+ memory T-cell phenotype at the site of disease in extrapulmonary tuberculosis

HIV-1-infected people have an increased risk of developing extrapulmonary tuberculosis (TB), the immunopathogenesis of which is poorly understood. Here, we conducted a detailed immunological analysis of human pericardial TB, to determine the effect of HIV-1 co-infection on the phenotype of Mycobacterium tuberculosis (MTB)-specific memory T cells and the role of polyfunctional T cells at the disease site, using cells from pericardial fluid and blood of 74 patients with (n=50) and without (n=24) HIV-1 co-infection. The MTB antigen-induced IFN-γ response was elevated at the disease site, irrespective of HIV-1 status or antigenic stimulant. However, the IFN-γ ELISpot showed no clear evidence of increased numbers of antigen-specific cells at the disease site except for ESAT-6 in HIV-1 uninfected individuals (p=0.009). Flow cytometric analysis showed that CD4⁺ memory T cells in the pericardial fluid of HIV-1-infected patients were of a less differentiated phenotype, with the presence of polyfunctional CD4⁺ T cells expressing TNF, IL-2 and IFN-γ. These results indicate that HIV-1 infection results in altered phenotype and function of MTB-specific CD4⁺ T cells at the disease site, which may contribute to the increased risk of developing TB at all stages of HIV-1 infection.

Monitoring of peptide-specific and gamma interferon-productive T cells in patients with active and convalescent tuberculosis using an enzyme-linked immunosorbent spot assay

To establish a high-efficiency gamma interferon-specific enzyme-linked immunosorbent spot assay (IFN-γ ELISPOT assay) for detection of tuberculosis (TB), peptides (E6, E7, and C14) and peptide mixtures (E6 plus E7 and E6 plus E7 plus C14) were used to monitor peripheral blood (PBL) samples from patients with pulmonary TB (PTB), as well as control samples. The positive detection rates of the five IFN-γ ELISPOT assays were 78.38%, 74.86%, 55.83%, 90.43%, and 91.51%, respectively, and there were similar detection rates between the two combined peptide mixture IFN-γ ELISPOT assays and the tuberculin skin test (TST) (90.62% versus 95.59%). No significant difference was found between the detection rates of the two combined peptide mixture IFN-γ ELISPOT assays and the T-SPOT.TB assay for 86 patients with PTB (P > 0.05), but the median number of spot-forming cells/10(6) cells (SFP value) for positive results was higher by the former than by the latter assay (P < 0.05). In contrast, the 29.93% positive detection rate and median SFP value of 482 by the two combined peptide mixture IFN-γ ELISPOT assays were significantly higher than the corresponding values of 14.29% and 152 by T-SPOT.TB assay for the same 147 community donors (P < 0.05). For nine PTB patients tracked, the SFP value of 7 for the two peptide mixture IFN-γ ELISPOT assays began to decrease from the second month after regular treatment. A relatively low, almost normal, SFP level was reached and maintained after the third or fourth month. Two in-house IFN-γ ELISPOT assays and the T-SPOT.TB assay could reduce the false-positive and false-negative detection rates of TST and sputum acid-fast staining. Therefore, these two combined peptide mixture IFN-γ ELISPOT assays have a potential advantage, beyond their greater specificity and sensitivity, for use in screening and detection of active TB infection (TBI) and latent TB infection (LTBI) in China.

Adjunctive tests for diagnosis of tuberculosis: serology, ELISPOT for site-specific lymphocytes, urinary lipoarabinomannan, string test, and fine needle aspiration

The diagnostic gold standard for active tuberculosis (TB) is the detection of Mycobacterium tuberculosis (MTB) by culture or molecular methods. However, despite its limited sensitivity, sputum smear microscopy is still the mainstay of TB diagnosis in resource-limited settings. Consequently, diagnosis of smear-negative pulmonary and extrapulmonary TB remains challenging in such settings. A number of novel or alternative techniques could provide adjunctive diagnostic use in the context of difficult-to-diagnose TB. These may be especially useful in certain patient groups such as persons infected with human immunodeficiency virus (HIV) and children, who are disproportionably affected by smear-negative and extrapulmonary disease and who are also most adversely affected by delays in TB diagnosis and treatment. We review a selection of these methods that are independent of nucleic acid amplification techniques and could largely be implemented in resource-limited settings in current or adapted versions. Specifically, we discuss the diagnostic use and potential of serologic tests based on detection of antibodies to MTB antigens; interferon gamma release assays using site-specific lymphocytes; detection of lipoarabinomannan, a glycolipid of MTB, in urine; the string test, a novel technique to retrieve lower respiratory tract samples; and fine needle aspiration biopsy of lymph nodes.

Higher frequency of T-cell response to M. tuberculosis latency antigen Rv2628 at the site of active tuberculosis disease than in peripheral blood

Rationale

Due to the invasive nature of the procedures involved, most studies of Mycobacterium tuberculosis (Mtb)-specific immunity in humans have focused on the periphery rather than the site of active infection, the lung. Recently, antigens associated with Mtb-latency and -dormancy have been described using peripheral blood (PB) cells; however their response in the lung is unknown. The objective of this report was to evaluate, in patients prospectively enrolled with suspected active tuberculosis (TB), whether the latency antigen Rv2628 induces local-specific immune response in bronchoalveolar lavage (BAL) cells compared to PB cells.

Material/Methods

Among the 41 subjects enrolled, 20 resulted with active TB. Among the 21 without active disease, 9 were defined as subjects with latent TB-infection (LTBI) [Quantiferon TB Gold In-tube positive]. Cytokine responses to Rv2628 were evaluated by enzyme linked immunospot (ELISPOT) assay and flow cytometric (FACS) analysis. RD1-secreted antigen stimulation was used as control.

Results

There was a significantly higher frequency of Rv2628- and RD1-specific CD4⁺ T-cells in the BAL of active TB patients than in PB. However the trend of the response to Rv2628 in subjects with LTBI was higher than in active TB in both PB and BAL, although this difference was not significant. In active TB, Rv2628 and RD1 induced a cytokine-response profile mainly consisting of interferon (IFN)-γ-single-positive over double-IFN-γ/interleukin (IL)-2 T-cells in both PB and BAL. Finally, BAL-specific CD4⁺ T-cells were mostly effector memory (EM), while peripheral T-cell phenotypes were distributed among naïve, central memory and terminally differentiated effector memory T-cells.

Conclusions

In this observational study, we show that there is a high frequency of specific T-cells for Mtb-latency and RD1-secreted antigens (mostly IFN-γ-single-positive specific T-cells with an EM phenotype) in the BAL of active TB patients. These data may be important for better understanding the pathogenesis of TB in the lung.

T-SPOT.TB assay usage in adults and children

The diagnosis and treatment of TB infection is one of the public health priorities. Until recently, diagnosis of TB infection has been based on the tuberculin skin test (TST). However, this is neither 100% sensitive nor specific for the diagnosis of TB infection owing to its many drawbacks. More recently, T-cell-based IFN-γ release assays (IGRAs) have been developed. In this article, we review the clinical performance of one of the IGRAs, T-SPOT.TB assay, for the diagnosis of TB infection in adults and children. We discuss the principle of the assay, its utility in active TB diseases, latent TB infection and the performance of the test in specialized subgroups of patients, such as immunocompromised individuals. When compared with the TST, the T-SPOT.TB assay has better specificity in bacillus Calmette-Guérin-vaccinated individuals, and data suggest that T-SPOT.TB may be more sensitive than the TST. Data in groups at high risk of progression to disease support the idea that T-SPOT.TB performs better than the TST. In addition, application of T-SPOT.TB by using bodily fluids such as cerebrospinal fluid, bronchoalveolar lavage fluid and pleural fluid may offer new diagnostic approaches in extrapulmonary TB disease. Although IGRAs cannot distinguish active TB disease from latent TB infection, these assays perform better than the TST for the detection of TB infection.