Cytometric detection of antigen-specific IFN-gamma/IL-2 secreting cells in the diagnosis of tuberculosis

The PE-PPE Family of Mycobacterium tuberculosis: Proteins in Disguise

Mycobacterium tuberculosis has thrived in parallel with humans for millennia, and despite our efforts, M. tuberculosis continues to plague us, currently infecting a third of the world's population. The success of M. tuberculosis has recently been attributed, in part, to the PE-PPE family; a unique collection of 168 proteins fundamentally involved in the pathogenesis of M. tuberculosis. The PE-PPE family proteins have been at the forefront of intense research efforts since their discovery in 1998 and whilst our knowledge and understanding has significantly advanced over the last two decades, many important questions remain to be elucidated. This review consolidates and examines the vast body of existing literature regarding the PE-PPE family proteins, with respect to the latest developments in elucidating their evolution, structure, subcellular localisation, function, and immunogenicity. This review also highlights significant inconsistencies and contradictions within the field. Additionally, possible explanations for these knowledge gaps are explored. Lastly, this review poses many important questions, which need to be addressed to complete our understanding of the PE-PPE family, as well as highlighting the challenges associated with studying this enigmatic family of proteins. Further research into the PE-PPE family, together with technological advancements in genomics and proteomics, will undoubtedly improve our understanding of the pathogenesis of M. tuberculosis, as well as identify key targets/candidates for the development of novel drugs, diagnostics, and vaccines.

Challenges and the Way forward in Diagnosis and Treatment of Tuberculosis Infection

Globally, it is estimated that one-quarter of the world's population is latently infected with Mycobacterium tuberculosis (Mtb), also known as latent tuberculosis infection (LTBI). Recently, this condition has been referred to as tuberculosis infection (TBI), considering the dynamic spectrum of the infection, as 5-10% of the latently infected population will develop active TB (ATB). The chances of TBI development increase due to close contact with index TB patients. The emergence of multidrug-resistant TB (MDR-TB) and the risk of development of latent MDR-TB has further complicated the situation. Detection of TBI is challenging as the infected individual does not present symptoms. Currently, there is no gold standard for TBI diagnosis, and the only screening tests are tuberculin skin test (TST) and interferon gamma release assays (IGRAs). However, these tests have several limitations, including the inability to differentiate between ATB and TBI, false-positive results in BCG-vaccinated individuals (only for TST), false-negative results in children, elderly, and immunocompromised patients, and the inability to predict the progression to ATB, among others. Thus, new host markers and Mtb-specific antigens are being tested to develop new diagnostic methods. Besides screening, TBI therapy is a key intervention for TB control. However, the long-course treatment and associated side effects result in non-adherence to the treatment. Additionally, the latent MDR strains are not susceptible to the current TBI treatments, which add an additional challenge. This review discusses the current situation of TBI, as well as the challenges and efforts involved in its control.

Mycobacterium tuberculosis-specific CD4 T-cell scoring discriminates tuberculosis infection from disease

Background

Rapid and reliable diagnostic work-up of tuberculosis (TB) remains a major healthcare goal. In particular, discrimination of TB infection from TB disease with currently available diagnostic tools is challenging and time consuming. This study aimed at establishing a standardised blood-based assay that rapidly and reliably discriminates TB infection from TB disease based on multiparameter analysis of TB antigen-reactive CD4⁺ T-cells acting as sensors for TB stage-specific immune status.

Methods

157 HIV-negative subjects with suspected TB infection or TB disease were recruited from local tertiary care hospitals in Berlin (Germany). Peripheral blood mononuclear cells were analysed for CD4⁺ T-cells reactive to the Mycobacterium tuberculosis antigens purified protein derivative and early secretory antigenic target 6 kDa/culture filtrate protein 10. The activation state of TB antigen-reactive T-cells, identified by surface expression of CD154, was evaluated according to the expression profile of proliferation marker Ki-67 and activation markers CD38 and HLA-DR. Using data from 81 subjects with clinically confirmed TB infection (n=34) or culture-proven pulmonary or extrapulmonary TB disease (n=47), 12 parameters were derived from the expression profile and integrated into a scoring system.

Results

Using the scoring system, our assay (TB-Flow Assay) allowed reliable discrimination of TB infection from both pulmonary and extrapulmonary TB disease with high sensitivity (90.9%) and specificity (93.3%) as was confirmed by Monte-Carlo cross-validation.

Conclusion

With low time requirement, ease of sample collection, and high sensitivity and specificity both for pulmonary and extrapulmonary TB disease, we believe this novel standardised TB-Flow Assay will improve the work-up of patients with suspected TB disease, supporting rapid TB diagnosis and facilitating treatment decisions.

In a prospective study, a scoring system based on analysis of the activation state of tuberculosis (TB)-specific CD4⁺ T-cells was developed that allows reliable discrimination of TB infection and TB disease with high sensitivity and specificityhttps://bit.ly/3EFG4KX

QuantiFERON-TB Gold Plus Assay in Patients With Latent vs. Active Tuberculosis in a Low Incidence Setting: Level of IFN-γ, CD4/CD8 Responses, and Release of IL-2, IP-10, and MIG

Objectives

We analyzed the results of the QuantiFERON Glod Plus assay (QFT) and cytokine patterns associated with active tuberculosis (ATB) among patients with positive QFT.

Methods

A total of 195 patients are QFT-positive, among which 24 had an ATB and 171 had a latent tuberculosis infection (LTBI). Interferon-gamma (IFN-γ) secretion was analyzed relative to interleukin-2 (IL-2), IFN-γ inducible protein or CXCL-10 (IP-10), and monokine induced by IFN-γ or CXCL-9 (MIG) secretion, and then compared between two sets of peptide antigens [tube 1 - cluster of differentiation 4 (CD4+) T cell stimulation; tube 2 - CD4+/CD8+ T cell response].

Results

Higher IFN-γ responses were measured in the ATB group (p = 0.0089). The results showed that there was a lower ratio of tube 1/tube 2 IFN-γ concentrations in the ATB group (p = 0.0009), and a median [interquartile ranges (IQR)] difference between the two sets at −0.82 IU/ml (−1.67 to 0.18) vs. −0.07 IU/ml (−0.035 to 0.11, p < 0.0001) in the ATB group compared to the LTBI group, respectively. In addition, patients with low ratios of IL-2/IFN-γ, IP-10/IFN-γ, and MIG/IFN-γ were much more likely to have ATB.

Conclusion

High levels of IFN-γ secretion, preferential IFN-γ response in tube 2, and lower secretion of IL-2, IP-10, and MIG release relative to IFN-γ secretion were more likely observed in subjects with ATB. These features of T cell response may be helpful in low prevalence settings to suspect ATB in patients tested positive for IFN-γ release assays (IGRA).

A Small Protein but with Diverse Roles: A Review of EsxA in Mycobacterium-Host Interaction

As a major effector of the ESX-1 secretion system, EsxA is essential for the virulence of pathogenic mycobacteria, such as Mycobacterium tuberculosis (Mtb) and Mycobacterium marinum (Mm). EsxA possesses an acidic pH-dependent membrane permeabilizing activity and plays an essential role by mediating mycobacterial escape from the phagosome and translocation to the cytosol for intracellular replication. Moreover, EsxA regulates host immune responses as a potent T-cell antigen and a strong immunoregulator. EsxA interacts with multiple cellular proteins and stimulates several signal pathways, such as necrosis, apoptosis, autophagy, and antigen presentation. Interestingly, there is a co-dependency in the expression and secretion of EsxA and other mycobacterial factors, which greatly increases the complexity of dissecting the precise roles of EsxA and other factors in mycobacterium-host interaction. In this review, we summarize the current understandings of the roles and functions of EsxA in mycobacterial infection and discuss the challenges and future directions.

CD38 +CD27 -TNF-α + on Mtb-specific CD4 + T is a robust biomarker for tuberculosis diagnosis

BACKGROUND

Early and accurate diagnosis followed by timely treatment are the key prerequisites to fight tuberculosis (TB) and reduce its global burden. Despite scientific advances, the rapid and correct diagnosis of both pulmonary and extrapulmonary tuberculosis remains a challenge due to traditional reliance on detection of the elusive bacilli. Mycobacterium tuberculosis (Mtb)-specific host immune activation and cytokine production have shown significant promise as alternative means of detecting and distinguishing active disease from latent infection. We queried the diagnostic ability of phenotypic markers on Mtb-specific cytokine-producing immune cell subsets for identifying active tuberculosis.

METHODS

Subjects belonging to the following groups were recruited - pulmonary and extrapulmonary TB, latent TB, cured TB, sick controls and healthy controls. Polychromatic flow cytometry was used to identify host immune biomarkers in an exploratory cohort comprising 56 subjects using peripheral blood mononuclear cells. Clinical performance of the identified biomarker was evaluated using whole blood in a blinded validation cohort comprising 165 individuals.

RESULTS

Cytokine secreting frequencies of Mtb-specific CD4 + T cells with CD38 +CD27 - phenotype clearly distinguished infected individuals with active tuberculosis from those without disease. TNF-α secretion from CD38 +CD27 -CD4 + T cells upon stimulation with ESAT6/CFP10 peptides had the best diagnostic accuracy at a cut-off of 9.91% [exploratory: 96.67% specificity, 88.46% sensitivity; validation: 96.15% specificity, 90.16% sensitivity]. Additionally, this subset differentiated treatment-naive TB patients from individuals cured of TB following completion of anti-tuberculosis therapy.

CONCLUSIONS

Mtb-specific CD38 +CD27 -TNF-α +CD4 + T cell subset is a robust biomarker both for diagnosing tuberculosis and assessing cure.

Human cancer germline antigen-specific cytotoxic T cell-what can we learn from patient

In this review, we will highlight the importance of cancer germline antigen-specific cytotoxic CD8⁺ T lymphocytes (CTL) and the factors affecting antitumor CTL responses. In light of cancer immunotherapy, we will emphasis the need to further understand the features, characteristics, and actions of modulatory receptors of human cancer germline-specific CTLs, in order to determine the optimal conditions for antitumor CTL responses.

Defective Interferon Gamma Production by Tumor-Specific CD8+ T Cells Is Associated With 5'Methylcytosine-Guanine Hypermethylation of Interferon Gamma Promoter

Interferon gamma (IFNγ) supports effector responses of CD8⁺ cytotoxic T lymphocytes (CTLs) and is a surrogate marker for detection of antigen-specific T cells. Here, we show that tumor-specific CTL clones have impaired IFNγ expression and production upon activation. Assessment of the relationship between IFNγ production and the 5'methylcytosine-guanine (CpG) dinucleotide methylation of the IFNγ promoter using bisulfite treatment has shown that IFNγ^- CTL clones accumulates CpG hypermethylation within the promoter at key transcription factor binding sites (-186 and -54), known to be vital for transcription. We confirmed these findings using ex vivo isolated and short-term expanded bulk tumor-specific CTL lines from four cancer patients and demonstrated that IFNγ methylation inversely correlates with transcription, protein level, and cytotoxicity. Altogether, we propose that a sizeable portion of human tumor-specific CTLs are deficient in IFNγ response, contributed by CpG hypermethylation of the IFNγ promoter. Our findings have important implications for immunotherapy strategies and for methods to detect human antigen-specific T cells.

A microfluidic antibody bioarray for fast detection of human interleukins in low sample volumes

The antibody bioarray is a promising tool for the detection of proteins, which can be used as disease biomarkers. Therefore, we have developed a sandwich immunoassay-type bioarray using a microfluidic method to detect human interleukins that have diagnostic values. In the method development, we studied the effect of different factors that affect capture antibody immobilization, antibody–antigen interactions, and detection methods on the bioarray surface. The fluorescence signal obtained from different detection strategies was compared based on the signal fold-increase. This comparison showed that the use of covalent immobilization of capture antibodies, as opposed to their physical adsorption on the bioarray surface, increases the signal by 1.5 fold. Moreover, the use of protein G to achieve a better oriented immobilized capture antibody has resulted in a more than 3-fold signal enhancement.

Application of IFN-γ/IL-2 FluoroSpot assay for distinguishing active tuberculosis from non-active tuberculosis: A cohort study

Currently available Interferon-γ release assay cannot reliably differentiate active TB (ATB) from non-active TB (non-ATB). This study aimed to evaluate the diagnostic accuracy of the IFN-γ/IL-2 FluoroSpot assay, which can simultaneously detect IFN-γ and IL-2 secretion, for differentiating ATB from non-ATB. 191 suspected ATB patients with positive T-SPOT.TB results were consecutively recruited. 64 (33.5%) participants had ATB, including 22 (34.4%) microbiologically or histologically confirmed TB and 42 (65.6%) clinically diagnosed TB. 119 (62.3%) cases were non-ATB and 8 (4.2%) were clinically indeterminate. After being stimulated with ESAT-6 and CFP-10 antigens, the median frequency and proportion of IFN-γ⁺IL-2^- T cells were significantly higher in the ATB group than the non-ATB group (P < .001). The areas under the ROC curves of IFN-γ⁺IL-2^- T cells were larger than those of total IFN-γ⁺ T cells (0.788 vs. 0.739, p = .323). With a cutoff value of 25 SFCs/250,000 PBMCs for frequency, sensitivity and specificity of this assay were 73.4% and 69.8% respectively. When combining the frequency and proportions of IFN-γ⁺IL-2^- T cells, the sensitivity and specificity were increased to 95.3% in parallel testing and 83.2% in serial testing respectively. In conclusion, IFN-γ/IL-2 FluoroSpot assay is conducive for the diagnosis of ATB in patients with positive T-SPOT.TB results.

Optimization of the autophagy measurement in a human cell line and primary cells by flow cytometry

The limited availability of rapid and reliable flow cytometry-based assays for ex vivo quantification of autophagy has hampered their clinical applications for studies of diseases pathogenesis or for the implementation of autophagy-targeting therapies. To this aim, we modified and improved the protocol of a commercial kit developed for quantifying the microtubule-associated protein 1A/1B light chain 3B (LC3), the most reliable marker for autophagosomes currently available. The protocol modifications were set up measuring the autophagic flux in neoplastic (THP-1 cells) and primary cells (peripheral blood mononuclear cells; PBMC) of healthy donors. Moreover, PBMC of active tuberculosis (TB) patients were stimulated with the Mycobacterium tuberculosis purified protein derivatives or infected with live Mycobacterium bovis bacillus Calmette-Guerin (BCG). We found that the baseline median fluorescent intensity (MFI) of THP-1 cells changed depending on the time of sample acquisition to the flow cytometer. To solve this problem, a fixation step was introduced in different stages of the assay's protocol, obtaining more reproducible and sensitive results when a post-LC3 staining fixation was performed, in either THP1 or PBMC. Furthermore, since we found that results are influenced by the type and the dose of the lysosome inhibitor used, the best dose of Chloroquine for LC3 accumulation were set up in either THP-1 cells or PBMC. Finally, applying these experimental settings, we measured the autophagic flux in CD14+ cells from active TB patients' PBMC upon BCG infection. In conclusion, our data indicate that the protocol modifications here described in this work improve the stability and accuracy of a flow cytometry-based assay for the evaluation of autophagy, thus assuring more standardised cell analyses.

Evaluation of profile and functionality of memory T cells in pulmonary tuberculosis

The cells T CD4+ T and CD8+ can be subdivided into phenotypes naïve, T of central memory, T of effector memory and effector, according to the expression of surface molecules CD45RO and CD27. The T lymphocytes are cells of long life with capacity of rapid expansion and function, after a new antigenic exposure. In tuberculosis, it was found that specific memory T cells are present, however, gaps remain about the role of such cells in the disease immunology. In this study, the phenotypic profile was analyzed and characterized the functionality of CD4+ T lymphocytes and CD8+ T cells of memory and effector, in response to specific stimuli in vitro, in patients with active pulmonary TB, compared to individuals with latent infection with Mycobacterium tuberculosis the ones treated with pulmonary TB. It was observed that the group of patients with active pulmonary tuberculosis was the one which presented the highest proportion of cells T CD4+ of central memory IFN-ɣ+ e TNF-α+, suggesting that in TB, these T of central memory cells would have a profile of protective response, being an important target of study for the development of more effective vaccines; this group also developed lower proportion of CD8+ T effector lymphocytes than the others, a probable cause of specific and less effective response against the bacillus in these individuals; the ones treated for pulmonary tuberculosis were those who developed higher proportion of T CD4+ of memory central IL-17+ cells, indicating that the stimulation of long duration, with high antigenic load, followed by elimination of the pathogen, contribute to more significant generation of such cells; individuals with latent infection by M. tuberculosis and treated for pulmonary tuberculosis, showed greater response of CD8+ T effector lymphocytes IFN-ɣ+ than the controls, suggesting that these cells, as well as CD4+ T lymphocytes, have crucial role of protection against M. tuberculosis. These findings have contributed to a better understanding of the immunologic changes in M. tuberculosis infection and the development of new strategies for diagnosis and prevention of tuberculosis.

Comparative Diagnostic Utility of Neopterin and IFN-γ/IL-2 in Extrapulmonary Tuberculosis

Resurgence of TB has emphasized the need for newer methods of diagnosis. Extrapulmonary tuberculosis (EPTB), being paucibacillary, is a diagnostic dilemma. The aim of the present study was to correlate IFN-γ/IL-2 with neopterin in diagnosis of EPTB. Extrapulmonary specimens from 69 clinically diagnosed cases were stained by Ziehl-Neelsen and cultured on Lowenstein-Jensen medium for Mycobacterium tuberculosis. ELISA was used to assess serum IFN-γ, IL-2 and neopterin levels. Median serum levels of IFN-γ/IL-2 and neopterin were 3.22 and 21.6 nmol/L in clinically diagnosed EPTB cases and 0.52 and 4.20 nmol/L in healthy controls respectively (p < 0.001). Both IFN-γ/IL-2 and neopterin were significantly higher in culture positive (14.64 and 49.8 nmol/L) than culture negative cases (3.01 and 17.5 nmol/L) respectively (p < 0.05). IFN-γ/IL-2 was significantly higher in AFB smear positive cases (8.63) than smear negative cases (3.04) (p = 0.003), whereas no significant difference in neopterin levels was seen (p = 0.307). A positive correlation between IFN-γ/IL-2 and neopterin was seen in EPTB cases (spearman's rho = 0.453, p < 0.001), whereas in healthy controls no such correlation existed (spearman's rho = 0.018, p = 0.884). An urgent need for research in the field of biomarkers exists to utilize them as point of care test in the diagnosis of EPTB.

Utility of Th1-cell immune responses for distinguishing active tuberculosis from non-active tuberculosis: A case-control study

Currently available Interferon-γ release assay (IGRA) cannot reliably differentiate active TB (ATB) from non-active TB (non-ATB). A study was performed to evaluate the value of Mycobacterium tuberculosis (MTB) specific Th1 cell immune responses which test IFN-γ and IL-2 simultaneous for differentiating ATB from non-ATB. Forty-nine newly diagnosed inpatients with ATB (26 pulmonary TB and 23 extrapulmonary TB) were enrolled as the ATB group. Forty-five volunteers with latent tuberculosis infection (LTBI) and twenty with evidence of previous TB were enrolled during the same period as the non-ATB group. Clinical examination and MTB specific Th1 cell immune responses were performed for all participants. After being stimulated with ESAT-6 and CFP-10, the median frequencies of single IL-2-, single IFN-γ-, and dual IFN-γ/IL-2-secreting T-cells were all higher in the ATB group than in the non-ATB group (20(8–45) vs. 7(3–13), P<0.001;131(44–308) vs. 10(6–27), P<0.001;25(9–74) vs. 7(3–23), P = 0.001, respectively). Evaluation of the diagnostic performance of detecting single IFN-γ-secreting T cells for pulmonary TB employed a cutoff value of 35 iSFCs/250,000 PBMC. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were 92.3%, 80.0%, 64.9%, 96.3%, 4.62, and 0.10, respectively. For extrapulmonary TB, using a cutoff value of 23 iSFCs/ 250,000 PBMC, the sensitivity, specificity, PPV, NPV, PLR, and NLR were 91.3%, 76.9%, 58.3%, 96.2%, 3.96, and 0.11, respectively. When combining frequencies and proportion of single IFN-γ-secreting T cells, the test sensitivity was 100% in parallel tests and the specificity was 87.7% in serial tests for pulmonary TB. MTB specific Th1 cell immune responses (FluoroSpot) had value for the differentiation of ATB and non-ATB. Further confirmatory studies are indicated.

Interactions between Type 1 Interferons and the Th17 Response in Tuberculosis: Lessons Learned from Autoimmune Diseases

The classical paradigm of tuberculosis (TB) immunity, with a central protective role for Th1 responses and IFN-γ-stimulated cellular responses, has been challenged by unsatisfactory results of vaccine strategies aimed at enhancing Th1 immunity. Moreover, preclinical TB models have shown that increasing IFN-γ responses in the lungs is more damaging to the host than to the pathogen. Type 1 interferon signaling and altered Th17 responses have also been associated with active TB, but their functional roles in TB pathogenesis remain to be established. These two host responses have been studied in more detail in autoimmune diseases (AID) and show functional interactions that are of potential interest in TB immunity. In this review, we first identify the role of type 1 interferons and Th17 immunity in TB, followed by an overview of interactions between these responses observed in systemic AID. We discuss (i) the effects of GM-CSF-secreting Th17.1 cells and type 1 interferons on CCR2⁺ monocytes; (ii) convergence of IL-17 and type 1 interferon signaling on stimulating B-cell activating factor production and the central role of neutrophils in this process; and (iii) synergy between IL-17 and type 1 interferons in the generation and function of tertiary lymphoid structures and the associated follicular helper T-cell responses. Evaluation of these autoimmune-related pathways in TB pathogenesis provides a new perspective on recent developments in TB research.

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.

Detection of interleukin-2 is not useful for distinguishing between latent and active tuberculosis in clinical practice: a prospective cohort study

OBJECTIVE

Previous reports have identified interleukin-2 (IL-2), quantified in the supernatants of QuantiFERON^®-TB Gold In-tube (QFT) after 72 h of incubation, as a potential biomarker for distinguishing between latent and active tuberculosis (TB). However, its validity has not been tested in an appropriate clinical cohort.

METHODS

A multicentre study of 161 consecutive adult patients undergoing evaluation for active TB at eight TB Units in Spain. Interferon-γ (IFN-γ) and IL-2 were assessed in the supernatant of QFT after 16-24 h and 72 h of incubation. The accuracy of IL-2 for indicating latent TB infection (LTBI) was assessed by receiving operating characteristic curves. .

RESULTS

Twenty-eight participants were not infected, 43 had LTBI, 69 had TB, and 21 were not classifiable. Median (interquartile range) IL-2 concentrations after 72 h of incubation were 0.0 pg/mL (0.0-0.0) in uninfected individuals, 261.0 pg/mL (81.0-853.0) in LTBI individuals, 166.5 pg/mL (33.5-551.5) in patients with extrapulmonary TB, 95.0 pg/mL (26.0-283.0) in patients with smear-negative pulmonary TB, and 38.5 pg/mL (7.5-178.0) in patients with smear-positive pulmonary TB (p <0.0001). The area under the curve of the receiving operating characteristic curve (95% CI) of IL-2 after 72 h of incubation for the diagnosis of LTBI was 0.63 (0.53-0.74) when all TB cases were considered as a single group, ranging from 0.59 (0.47-0.71) to 0.72 (0.58-0.85) when only extrapulmonary and smear-positive pulmonary TB cases respectively were considered.

CONCLUSIONS

Quantification of IL-2 in the supernatant of QFT after a prolonged incubation is not useful to distinguish between LTBI and active disease in clinical practice.

High IFN-γ Release and Impaired Capacity of Multi-Cytokine Secretion in IGRA Supernatants Are Associated with Active Tuberculosis

Interferon gamma (IFN-γ) release assays (IGRAs) detect Mycobacterium tuberculosis (Mtb) infection regardless of the active (ATB) or latent (LTBI) forms of tuberculosis (TB). In this study, Mtb-specific T cell response against region of deletion 1 (RD1) antigens were explored by a microbead multiplex assay performed in T-SPOT TB assay (T-SPOT) supernatants from 35 patients with ATB and 115 patients with LTBI. T-SPOT is positive when over 7 IFN-γ secreting cells (SC)/250 000 peripheral blood mononuclear cells (PBMC) are enumerated. However, over 100 IFN-γ SC /250 000 PBMC were more frequently observed in the ATB group compared to the LTBI group. By contrast, lower cytokine concentrations and lower cytokine productions relative to IFN-γ secretion were observed for IL 4, IL-12, TNF-α, GM-CSF, Eotaxin and IFN-α when compared to LTBI. Thus, high IFN-γ release and low cytokine secretions in relation with IFN-γ production appeared as signatures of ATB, corroborating that multicytokine Mtb-specific response against RD1 antigens reflects host capacity to contain TB reactivation. In this way, testing cytokine profile in IGRA supernatants would be helpful to improve ATB screening strategy including immunologic tests.

A rapid alternative method to evaluate T-cell hybridoma activation using an improved cytokine (IL-2) secretion assay

T-cell hybridoma assays have been widely used for the in vitro study of antigen processing and presentation because they represent an unlimited source of cells and they bypass the difficulty of maintaining T-cell clones in culture. One of the most widely used methods to assess hybridoma activation is measurement of CTLL-2 cell proliferation, which is dependent on IL-2. However, continuous culture of this cell line results in a loss of sensitivity, and significant interassay variability can occur. Therefore, our goal was to develop a method to assess T-cell hybridoma activation that was fast and sensitive with low variability based on the IL-2 secretion assay. The assay used flow cytometry detection and employed the hen egg lysozyme (HEL)-specific 3A9 hybridoma as a model. The original murine IL-2 secretion assay protocol from Miltenyi Biotec® was tested and modified; the conjugated capture antibody (anti-CD45-anti-IL-2) was added together with the stimulus at the beginning of the antigen presentation assay instead of after antigenic stimulation. With this modification, the percentage of detectable CD4⁺IL-2⁺ cells following HEL stimulation rose from 4.5% with the original protocol (0.8% without stimulus) to 94.1% (0.8% without stimulus) with the newly proposed method under the conditions evaluated in this study. This modification allowed us to evaluate the activation of hybridomas directly and more rapidly (~18h) than the reference method that assayed CTLL-2 cell proliferation using the MTT reduction assay (~48h). In conclusion, the proposed method offered a rapid alternative for screening T-cell hybridomas and evaluating their antigen-specific activation.

Evaluation of QuantiFERON-TB Gold Plus for Detection of Mycobacterium tuberculosis infection in Japan

Performance of interferon-γ (IFN-γ) release assays still needs to be improved. The data on the performance of QuantiFERON-TB Gold Plus (QFT-Plus), a new-generation of QFT assay are limited. This study evaluated the diagnostic performance of QFT-Plus, and compared to that of QuantiFERON-TB Gold In-Tube (QFT-GIT). Blood samples were collected from 162 bacteriologically confirmed tuberculosis (TB) patients and 212 Mycobacterium tuberculosis-uninfected volunteers; these samples were then tested with QFT-GIT and QFT-Plus. The IFN-γ concentration of QFT-Plus was lower than that of QFT-GIT in TB patients (p < 0.001). Receiver operating characteristic curves were compared between QFT-GIT and QFT-Plus. Both assays showed area under the curve values over 0.99 without significant difference. Using the conventional cut-off (0.35 IU/mL) for QFT-GIT, QFT-Plus had a lower sensitivity of 91.1% compared to 96.2% (p = 0.008) at its optimum cut-off (0.168 IU/mL) with the same specificity. Moreover, IFN-γ values were significantly reduced with age in QFT-GIT (p = 0.035) but not in QFT-Plus. The diagnostic performance of QFT-Plus was as accurate as that of QFT-GIT despite a lack of TB7.7 antigen and despite the decrease in quantitative values. However, the cut-off value for QFT-Plus should be considered independently from that of QFT-GIT to obtain the best sensitivity without compromising specificity.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Novel T-cell assays for the discrimination of active and latent tuberculosis infection: the diagnostic value of PPE family

OBJECTIVE

The diagnosis of active and latent tuberculosis remains a challenge. Although a new approach based on detecting Mycobacterium tuberculosis-specific T-cells has been introduced, it cannot distinguish between latent infection and active disease. The aim of this study was to evaluate the diagnostic potential of interleukin-2 (IL-2) as biomarker after specific antigen stimulation with PE35 and PPE68 for the discrimination of active and latent tuberculosis infection (LTBI).

METHOD

The production of IL-2 was measured in the antigen-stimulated whole-blood supernatants following stimulation with recombinant PE35 and PPE68.

RESULTS

The discrimination performance (assessed by the area under ROC curve) for IL-2 following stimulation with recombinant PE35 and PPE68 between LTBI and patients with active TB were 0.837 [95 % confidence interval (CI) 0.72-0.97] for LTBI diagnosis and 0.75 (95 % CI 0.63-0.89) for active TB diagnosis, respectively. Applying the 6.4 pg/mL cut-off for IL-2 induced by PE35 in the present study population resulted in sensitivity of 78 %, specificity of 83 %, PPV of 83 % and NPV of 78 % for the discrimination of active TB and LTBI. In addition, a sensitivity of 81 %, specificity of 71 %, PPV of 68 and 83 % of NPV was reported based on the 4.4 pg/mL cut-off for IL-2 induced by PPE68.

CONCLUSION

This study confirms IL-2 induced by PE35 and PPE68 as a sensitive and specific biomarker and highlights IL-2 as new promising adjunct markers for discriminating of LTBI and active TB disease.

Multiple cytokine responses in discriminating between active tuberculosis and latent tuberculosis infection

BACKGROUND

Cytokines play an important role in cell-mediated immune responses against Mycobacterium tuberculosis (Mtb) infection. Cytokine profile specifically associated with active tuberculosis (ATB) patients, subjects with latent tuberculosis infection (LTBI) and non-infected individuals remains to be determined.

METHODS

We enrolled a total of 92 subjects including patients with ATB (n = 25), LTBI (n = 36) and healthy controls (HC, n = 31) to investigate the cytokine production by peripheral blood mononuclear cells after Mtb purified protein derivative (PPD) stimulation which was evaluated by a beads-based multiplex assay system.

RESULTS

The production of IL-1β, IL-2, IL-6, IL-10, IL-17, G-CSF, IFN-γ, IP-10, MIP-1α and TNF-α was abundantly induced by PPD in all three groups. The levels of IL-2, IL-10, IFN-γ, IP-10 and TNF-α were significantly higher in LTBI group than in ATB group. The combination of PPD-stimulated IL-2 and IL-10 accurately identified 84.0% of ATB and 88.9% of LTBI. We validated the use of PPD-stimulated IL-2 and IL-10 test combined with T-SPOT.TB test in a cohort of 44 subjects with TB suspicion. The sensitivity and specificity of the combined test were 83.3% and 92.3%, respectively. The PPD-stimulated IL-2/IFN-γ ratio (p < 0.001) in LTBI subjects was significantly higher than in active TB patients.

CONCLUSION

Our study identified cytokine patterns characteristic of ATB and LTBI. Cytokines such as IL-2 and IL-10 may serve as biomarkers for distinguishing ATB from LTBI and healthy control and may contribute to intervention and improvement in TB diagnosis.

High IL-6 and low IL-15 levels mark the presence of TB infection: A preliminary study

The host immune response, apart from mycobacterial factors, is a significant determinant in the development of tuberculosis (TB). The purpose of the study was to examine whether the differential serum profiles of cytokines IL-1β, IL-2, IL-4, IL-6, IL-10, IL-15, IFN-γ, TGF-β, and TNF-α could discriminate between TB patients and healthy controls and provide insights into pathogenesis. Serum samples from TB patients, TB patient contacts and healthy controls were collected and analyzed by ELISA. The cytokine concentrations obtained were stratified into three groups: below detection limit (BDL), low values, and high values. The differences in cytokine concentrations were analyzed by Fisher's exact test. The statistically significant results were interpreted based on post-hoc analysis of the chi square contingency table using the adjusted residual method. Among the assayed cytokines, there was a statistically significant difference in the detection levels of IL-6, IL-15 and IFN-γ. Levels of IL-1β, IL-2, IL-4, IL-10, TGF-β and TNF-α did not vary. Post-hoc analysis of the significant results revealed that dynamic changes in the BDL and high values of cytokines influenced the post-infection cytokine milieu in the study subjects. The study concludes that altered balance in the levels of serum cytokines can be indicative of TB pathogenesis. Hence, profiling of dynamic changes in cytokines would facilitate effective TB diagnostic and treatment strategies.

Assessment of CD27 expression as a tool for active and latent tuberculosis diagnosis

There are still no reliable tests to distinguish active tuberculosis (TB) from latent TB infection (LTBI). Assessment of CD27 modulation on CD4⁺ T-cells has been suggested as a tool to diagnose different TB stages.

OBJECTIVES

To use several cytometric approaches to evaluate CD27 expression on Mycobacterium tuberculosis (Mtb)-specific CD4⁺ T-cells to differentiate TB stages.

METHODS

55 HIV-uninfected subjects were enrolled: 13 active TB; 12 cured TB; 30 LTBI. Whole blood was stimulated with RD1-proteins or Cytomegalovirus-lysate (CMV). Interferon (IFN)-γ response was evaluated by cytometry. The proportion of CD27(±) within the IFN-γ⁺ CD4⁺ T-cells or RATIO of the CD27-median fluorescence intensity (MFI) of CD4⁺ T-cells over the CD27 MFI of IFN-γ⁺ CD4⁺ T-cells was evaluated.

RESULTS

The greatest diagnostic accuracy in discriminating active TB vs. LTBI or cured TB was reached by evaluating the CD27(+) CD45RA(-) cells within the IFN-γ⁺ CD4⁺ T-cell subset (76.92 sensitivity for both, and 90% and 91.67% specificity, respectively), although the use of the CD27 MFI RATIO allows for stricter data analysis, independent of the operator.

CONCLUSIONS

the study of CD27 expression using different approaches, whether it involves evaluation of CD45RA expression or not, is a robust biomarker for discriminating TB stages.

Multifunctional Analysis of CD4+ T-Cell Response as Immune-Based Model for Tuberculosis Detection

Mono- and multifunctional specific CD4⁺ and CD8⁺ T-cell responses were evaluated to improve the immune-based detection of active tuberculosis (TB) and latent infection (LTBI). We applied flow cytometry to investigate cytokines profile (IFN-γ, TNF-α, and IL-2) of T cells after stimulation with TB antigens in 28 TB-infected subjects (18 active TB and 10 LTBI) and 10 uninfected controls. Cytokines production by CD4⁺ T cells at single-cell levels was higher in TB-infected subjects than uninfected controls (P < 0.0001). Assigning to activated CD4⁺ T cells, producing any of the three cytokines, a cut-off >0.45%, it was possible to differentiate TB-infected (>0.45%) by uninfected subjects (<0.45%). Among TB-infected subjects, the frequencies of multifunctional CD4⁺ T cells, simultaneously producing all 3 cytokines, are lower in active TB than LTBI subjects (P = 0.003). Thus, assigning to triple-positive CD4⁺ T cells a cut-off <0.182%, TB-infected individuals could be classified as active TB subjects (<0.182%) or LTBI subjects (>0.182%). The magnitude of CD8⁺ T-cell responses showed no differences between active TB and LTBI. Multifunctional CD4⁺ T-cell responses could have the potential to identify at single time point subjects without TB infection and patients having active or latent TB.

Tuberculosis specific responses following therapy for TB: Impact of HIV co-infection

Characterizing perturbations in the immune response to tuberculosis in HIV can develop insights into the pathogenesis of coinfection. HIV+ TB+ and TB monoinfected (TB+) subjects recruited from clinics in Bamako prior to initiation of TB treatment were evaluated at time-points following initiation of therapy. Flow cytometry assessed CD4+/CD8+ T cell subsets and activation markers CD38/HLA-DR. Antigen specific responses to TB proteins were assessed by intracellular cytokine detection and proliferation. HIV+ TB+ subjects had significantly higher markers of immune activation in the CD4+ and CD8+ T cells compared to TB+ subjects. HIV+ TB+ had lower numbers of TB-specific CD4+ T cells at baseline. Plasma IFNγ levels were similar between HIV+ TB+ and TB+ subjects. No differences were observed in in-vitro proliferative capacity to TB antigens between HIV+ TB+ and TB+ subjects. Subjects with HIV+ TB+ coinfection demonstrate in vivo expansion of TB-specific CD4+ T cells. Immunodeficiency associated with CD4+ T cell depletion may be less significant compared to immunosuppression associated with HIV viremia or untreated TB infection.

Could inducible protein-10 and heparin-binding hemagglutinin improve the detection of Mycobacterium tuberculosis-infected subjects in a country with low incidence of tuberculosis?

BACKGROUND

This study aimed to evaluate inducible protein-10 (IP-10) as a biomarker besides interferon-gamma (IFN-γ) to improve the identification of active tuberculosis (TB) and latent tubercular infection (LTBI) in a country with a low incidence of TB.

METHODS

Whole blood from Mycobacterium tuberculosis-infected subjects was stimulated with region-of-difference-1 (RD1)-specific peptides and with heparin-binding hemagglutinin (HBHA) to determine the release of IP-10 and IFN-γ.

RESULTS

No statistically significant difference was observed between positive rates of IP-10 and IFN-γ after RD1-specific peptide stimulation in the TB and LTBI groups; a different response was detected in QuantiFERON TB-gold test-negative (QFT-) subjects. A significantly different proportion of positive responses was observed between IP-10 and IFN-γ following HBHA stimulation in the TB group and in the QFT- group but not in the LTBI group.

CONCLUSIONS

The IP-10 test seemed to identify false-negative QFT results in some subjects with a positive IFN-γ/IP-10/HBHA pattern.

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.

Specific in vitro interferon-gamma and IL-2 production as biomarkers during treatment of chronic Q fever

BACKGROUND

Antibiotic treatment of chronic Q fever is cumbersome and of long duration. To monitor treatment, there is a need for alternative biomarkers. Coxiella burnetii-specific interferon (IFN)-γ and interleukin (IL)-2 production reflect the type of effector and memory T-cell response. In chronic Q fever, C. burnetii-specific IFN-γ production is higher and IL-2 production is lower than in individuals with past Q fever. Here we explore whether C. burnetii-specific IFN-γ and IL-2 production correlate to treatment response.

METHODS

We studied the longitudinal C. burnetii-specific IFN-γ/IL-2 ratio in fifteen proven chronic Q fever patients. All patients were followed for at least 18 months during antibiotic treatment. Treatment was considered successful when clinical recovery was observed, a positive PCR for C. burnetii DNA in blood became persistently negative, anti-phase I IgG showed a fourfold decrease or more, and imaging techniques showed disappearance of infectious foci.

RESULTS

Overall, the IFN-γ/IL-2 ratio declined when patients experienced a successful treatment outcome. When treatment failed, IFN-γ/IL-2 ratios did not significantly decrease. The median (±IQR) slope of the longitudinal IFN-γ/IL-2 ratio with successful treatment was -2.10 (-7.02 to -0.06), and -0.15 (-1.13 to 0.25) with unsuccessful treatment (P = 0.19). Q fever endocarditis patients had higher IFN-γ/IL-2 ratios than patients with endovascular infections.

CONCLUSION

We propose that the IFN-γ/IL-2 ratio can be used as an additional biomarker for monitoring chronic Q fever treatment, with declining ratios being indicative of successful treatment.

Increased percentage of IFN-γ producing CD56+CD3+ cells in active tuberculosis patients upon CFP-10 stimulation of peripheral mononuclear cells

Aiming to identify a possible biomarker that distinguishes immune cellular response of active tuberculosis from latent infection. Peripheral blood mononuclear cells (PBMCs) of pulmonary tuberculosis patients (PTB), tuberculin positive household contacts (TST(+) HHC), and tuberculin negative non-household contacts (TST− Non HHC) were stimulated with PPD or CFP-10 and the percentage of CD69(+) cells, proliferating precursor and IFN-γ producing CD4(+), CD8(+), CD56(+)CD3(−) and CD56(+)CD3(+) cells were compared. IL-2, IL-12p70, IL-15, IL-18 and IL-10 were measured in culture supernatants. PTB and TST+ HHC presented higher percentages of CD69(+) cells, IFN-γ(+) and proliferating precursors in all subpopulations studied and higher IL-12p70 levels than TST- Non HHC. The increased percentage of IFN-γ producing CD56(+)CD3(+) cells in response to CFP-10 in PTB, compared with TST− Non HHC and the ratios between the percentage of CD56(+)CD3(+) cells/CD56(+)CD3(−) and CD8(+) cells producing IFN-γ suggest that these parameters may distinguish active TB from latently infected individuals.

Discrimination between active and latent tuberculosis based on ratio of antigen-specific to mitogen-induced IP-10 production

Mycobacterium tuberculosis is the major causative agent of tuberculosis (TB). The gamma interferon (IFN-γ) release assay (IGRA) has been widely used to diagnose TB by testing cell-mediated immune responses but has no capacity for distinguishing between active TB and latent TB infection (LTBI). This study aims to identify a parameter that will help to discriminate active TB and LTBI. Whole-blood samples from 33 active TB patients, 20 individuals with LTBI, and 26 non-TB controls were applied to the commercial IFN-γ release assay, QuantiFERON-TB Gold In-Tube, and plasma samples were analyzed for interleukin-2 (IL-2), IL-6, IL-8, IL-10, IL-13, tumor necrosis factor-alpha (TNF-α), IFN-γ, monokine induced by IFN-γ (MIG), interferon gamma inducible protein 10 (IP-10), interferon-inducible T cell alpha chemoattractant (I-TAC), and monocyte chemoattractant protein 1 (MCP-1) by using a commercial cytometric bead array. The Mycobacterium tuberculosis antigen-specific production of most of the assayed cytokines and chemokines was higher in the active TB than in the LTBI group. The mitogen-induced responses were lower in the active TB than in the LTBI group. When the ratio of TB-specific to mitogen-induced responses was calculated, IL-2, IL-6, IL-10, IL-13, TNF-α, IFN-γ, MIG, and IP-10 were more useful in discriminating active TB from LTBI. In particular, most patients showed higher IP-10 production to Mycobacterium tuberculosis antigens than to mitogen at the individual level, and the ratio for IP-10 was the strongest indicator of active infection versus LTBI with 93.9% sensitivity and 90% specificity. In conclusion, the ratio of the TB-specific to the mitogen-induced IP-10 responses showed the most promising accuracy for discriminating active TB versus LTBI and should be further studied to determine whether it can serve as a biomarker that might help clinicians administer appropriate treatments.

Characterization of a novel antigen of Mycobacterium tuberculosis K strain and its use in immunodiagnosis of tuberculosis

Mycobacterium tuberculosis-specific antigens would be of great value in developing immunodiagnostic tests for tuberculosis (TB), but regional differences in molecular types of the organism may result in antigenic variation, which in turn affects the outcome of the tests. For example, the Beijing strains of M. tuberculosis are prevalent in East Asia, and in particular, the K strain and related strains of the Beijing family, are most frequently isolated during school outbreaks of TB in South Korea. From comparison of genome sequences between M. tuberculosis K strain and the H37Rv strain, a non-Beijing type, we identified a K strain-specific gene, InsB, which has substantial homology with the ESAT-6-like proteins. This study was, therefore, initiated to characterize the InsB protein for its immunogenicity in mice and to confirm its expression in TB patients by detecting antibodies to the protein. The InsB gene was cloned from M. tuberculosis K strain and expressed in Escherichia coli. The recombinant InsB protein was used for immunization of mice. All mice showed strong antibody responses to the InsB protein, and splenocytes stimulated with InsB showed strong IFN-γ and IL-17 responses and a weak IL-2 response, all of which have been implicated in disease expression and used for the immunodiagnosis of TB. Serum samples from TB patients also showed significant antibody responses to the InsB protein as compared to healthy control samples. These results indicate that the InsB protein is an M. tuberculosis K-strain-specific antigen that could further improve the current immunodiagnostic methods, especially for the South Korean population.

Long-term IFN-γ and IL-2 response for detection of latent tuberculosis infection in healthcare workers with discordant immunologic results

Discordant results between the interferon-gamma release assays (IGRAs) and tuberculin skin test (TST) are common in latent tuberculosis infection (LTBI). We evaluated whether the measurement of IFN-γ and interleukin (IL)-2T-cell responses, after prolonged Mycobacterium tuberculosis-specific antigen stimulation, can be used as adjunctive biomarker for LTBI detection in subjects with discordant results between TST and QuantiFERON-Gold In-Tube (QFT). 196 healthcare workers were screened for LTBI and in 90 of those participants, the QFT was repeated after 18 h, and IFN-γ/IL-2 immune response was measured after 72 h long-term stimulation. Of the 196 patients, 34 had positive, 155 negative, and 7 indeterminate QFT results. Discordant TST+/QFT- results were found in 29 (14.7%) patients, of whom 6 (20.6%) were Bacillus Calmette-Guerin (BCG) vaccinated. None of 23 non-BCG vaccinated subjects showed a specific IFN-γ immune response after 18 h nor 72 h of incubation, whereas 3/23 (13.04%) discordant subjects produced a specific long-term IL-2 response, which might reflect a LTBI status. In LTBI group (TST+/QFT+) both cytokine levels were increased after long-term in comparison to short-term stimulation. No significant long-term IFN-γ/IL-2 secretion was detected in control group (TST-/QFT-). Taken together, our data showed that the 87% of discordant patients who did not respond to the long-term assay, as controls subjects, were judged LTBI negative. The use of classic QFT and long-term IL-2 response may have a potential role to clarify the LTBI status in individuals in whom the diagnosis of LTBI is uncertain due to the discordance of the available diagnostic tests, such as TST and IGRA.

Diagnostic accuracy of IL-2 for the diagnosis of latent tuberculosis: a systematic review and meta-analysis

We conducted a systematic review and meta-analysis to evaluate the diagnostic potential of interleukin-2 (IL-2) as biomarkers for the diagnosis of latent tuberculosis. Related studies were identified through searches of PubMed, Embase, Web of Science, and complementary manual searches up to December 30, 2013. We used standard methods recommended for meta-analyses of diagnostic test evaluations. The analysis was based on a summary receiver operating characteristic (SROC) curve. Meta-regression analysis was used to assess the effects of some confounding factors on the results of the meta-analysis. The potential presence of publication bias was tested using the Deeks' funnel plots. The pooled estimates of IL-2 for latent tuberculosis infection (LTBI) diagnosis were as follows: sensitivity, 0.81 [95 % confidence interval (CI), 0.60 to 0.92]; specificity, 0.95 (95 % CI, 0.90 to 0.97); positive likelihood ratio (PLR), 15.2 (95 % CI, 8.1to 28.4); negative likelihood ratio (NLR), 0.20 (95 % CI, 0.09 to 0.47). We found that the SROC curve is positioned near the upper left corner of the curve and the area under the curve (AUC) was 0.96 (95 % CI, 0.94 to 0.98). In conclusion, according to the meta-analysis, IL-2 is a valid marker for the diagnosis of LTBI. When there is no definite gold standard for the diagnosis of LTBI, IL-2 release assay in addition to interferon-gamma release assays (IGRAs) can improve the ability of IGRAs to identify individuals with LTBI.

Multi-functional flow cytometry analysis of CD4+ T cells as an immune biomarker for latent tuberculosis status in patients treated with tumour necrosis factor (TNF) antagonists

Although monitoring tuberculosis (TB) infection during long-term treatment with tumour necrosis factor (TNF) antagonists is of great importance, no monitoring strategy has yet proved successful. Indeed, even the newly proposed interferon-gamma release assays (IGRAs) are known to produce dynamic changes in IFN-γ plasma levels, making them unreliable indicators of patients' pathological/clinical status. We used intracellular cytokine flow cytometry (ICCFC) to investigate the performance of multi-functional CD4(+) T cells producing IFN-γ, interleukin (IL)-2 and/or TNF in response to Mycobacterium tuberculosis-specific antigens in subjects treated with TNF antagonists. Patients were classified into three groups based on their TB status before commencement of treatment and on IFN-γ level fluctuations evaluated by IGRA during a 36-month follow-up period. The cytokine profile of M. tuberculosis-specific CD4(+) T cells showed that latent tuberculosis infection (LTBI) subjects had a higher frequency of double-positive IFN-γ(+) IL-2(+) CD4(+) T cells and triple-positive IFN-γ(+) IL-2(+) TNF(+) CD4(+) T cells compared to those without LTBI, who showed IFN-γ-level fluctuations over time. In contrast, this latter group of patients showed similar proportions of cells producing IFN-γ alone, IL-2 alone and IL-2 in combination with TNF in response to M. tuberculosis-specific antigens. It therefore appears that patients with and without LTBI infection are characterized by different intracellular cytokine profiles. This is the first study evaluating ICCFC in patients treated with TNF antagonists, and suggests that multi-functional analysis of CD4(+) T cells could be useful for ruling out TB infection in patients classified at screening as LTBI-negative but who show IGRA fluctuations under long-term TNF antagonist treatment.

Functional Signatures of Human CD4 and CD8 T Cell Responses to Mycobacterium tuberculosis

With 1.4 million deaths and 8.7 million new cases in 2011, tuberculosis (TB) remains a global health care problem and together with HIV and Malaria represents one of the three infectious diseases world-wide. Control of the global TB epidemic has been impaired by the lack of an effective vaccine, by the emergence of drug-resistant forms of Mycobacterium tuberculosis (Mtb) and by the lack of sensitive and rapid diagnostics. It is estimated, by epidemiological reports, that one third of the world’s population is latently infected with Mtb, but the majority of infected individuals develop long-lived protective immunity, which controls and contains Mtb in a T cell-dependent manner. Development of TB disease results from interactions among the environment, the host, and the pathogen, and known risk factors include HIV co-infection, immunodeficiency, diabetes mellitus, overcrowding, malnutrition, and general poverty; therefore, an effective T cell response determines whether the infection resolves or develops into clinically evident disease. Consequently, there is great interest in determining which T cells subsets mediate anti-mycobacterial immunity, delineating their effector functions. On the other hand, many aspects remain unsolved in understanding why some individuals are protected from Mtb infection while others go on to develop disease. Several studies have demonstrated that CD4⁺ T cells are involved in protection against Mtb, as supported by the evidence that CD4⁺ T cell depletion is responsible for Mtb reactivation in HIV-infected individuals. There are many subsets of CD4⁺ T cells, such as T-helper 1 (Th1), Th2, Th17, and regulatory T cells (Tregs), and all these subsets co-operate or interfere with each other to control infection; the dominant subset may differ between active and latent Mtb infection cases. Mtb-specific-CD4⁺ Th1 cell response is considered to have a protective role for the ability to produce cytokines such as IFN-γ or TNF-α that contribute to the recruitment and activation of innate immune cells, like monocytes and granulocytes. Thus, while other antigen (Ag)-specific T cells such as CD8⁺ T cells, natural killer (NK) cells, γδ T cells, and CD1-restricted T cells can also produce IFN-γ during Mtb infection, they cannot compensate for the lack of CD4⁺ T cells. The detection of Ag-specific cytokine production by intracellular cytokine staining (ICS) and the use of flow cytometry techniques are a common routine that supports the studies aimed at focusing the role of the immune system in infectious diseases. Flow cytometry permits to evaluate simultaneously the presence of different cytokines that can delineate different subsets of cells as having “multifunctional/polyfunctional” profile. It has been proposed that polyfunctional T cells, are associated with protective immunity toward Mtb, in particular it has been highlighted that the number of Mtb-specific T cells producing a combination of IFN-γ, IL-2, and/or TNF-α may be correlated with the mycobacterial load, while other studies have associated the presence of this particular functional profile as marker of TB disease activity. Although the role of CD8 T cells in TB is less clear than CD4 T cells, they are generally considered to contribute to optimal immunity and protection. CD8 T cells possess a number of anti-microbial effector mechanisms that are less prominent or absent in CD4 Th1 and Th17 T cells. The interest in studying CD8 T cells that are either MHC-class Ia or MHC-class Ib-restricted, has gained more attention. These studies include the role of HLA-E-restricted cells, lung mucosal-associated invariant T-cells (MAIT), and CD1-restricted cells. Nevertheless, the knowledge about the role of CD8⁺ T cells in Mtb infection is relatively new and recent studies have delineated that CD8 T cells, which display a functional profile termed “multifunctional,” can be a better marker of protection in TB than CD4⁺ T cells. Their effector mechanisms could contribute to control Mtb infection, as upon activation, CD8 T cells release cytokines or cytotoxic molecules, which cause apoptosis of target cells. Taken together, the balance of the immune response in the control of infection and possibly bacterial eradication is important in understanding whether the host immune response will be appropriate in contrasting the infection or not, and, consequently, the inability of the immune response, will determine the dissemination and the transmission of bacilli to new subjects. In conclusion, the recent highlights on the role of different functional signatures of T cell subsets in the immune response toward Mtb infection will be discerned in this review, in order to summarize what is known about the immune response in human TB. In particular, we will discuss the role of CD4 and CD8 T cells in contrasting the advance of the intracellular pathogen in already infected people or the progression to active disease in subjects with latent infection. All the information will be aimed at increasing the knowledge of this complex disease in order to improve diagnosis, prognosis, drug treatment, and vaccination.

Biomarkers of tuberculosis: a research roadmap

Tuberculosis (TB) continues to represent a major public health problem worldwide. Prompt and accurate diagnosis and effective treatment are fundamental to reducing morbidity and mortality and curtailing spread of infection. Furthermore, tackling the large reservoir of latent infection is the cornerstone to TB control in many high income low TB incidence countries. However, our existing toolkit for prevention, diagnosis and treatment remains outdated and inadequate. Here, we discuss the key targets for biomarker research and discovery in TB and recent developments in the field. We focus on host biomarkers, in particular: correlates of vaccine efficacy and sterilizing immunity; biomarkers of latent TB infection, including diagnosis, risk of progression to active TB and response to treatment; and markers of active TB, including diagnosis, response to treatment and risk of relapse. Recent scientific and technological advances have contributed to significant recent progression in biomarker discovery. Although there are clear remaining paucities, continued efforts within scientific, translational and clinical studies are likely to yield a number of clinically useful biomarkers of TB in the foreseeable future.

The use of acoustic force capture to ultra-purify lymphocyte subpopulations from human adult whole blood

Pre-analytical enrichment of cell populations prior to therapeutic delivery is of paramount interest throughout the fields of regenerative medicine and clinical interventional therapies. Enrichment of a cell population typically involves two aspects: (a) the increase in concentration of particular subpopulation of the total cell fraction by means of removal of other cells of no interest to the particular interrogation; and (b) improvement of resolution of signal by removal of 'noise' mostly arising from cellular debris in the treated sample. In this research, leukocyte populations were obtained from erythrocyte-depleted primary whole blood from human adults and subjected to flow through acoustic fields within the ultrasound range to remove cellular debris. It was possible to demonstrate aggregation and holding of leukocytes by using ultrasound within the frequency range 11.448-11.483 MHz, which facilitated removal of cellular debris by washing under continuous perfusion. The T-lymphocyte population were phenotypically characterized using CD4/CD8 (T(h)/T(c)) immunocytochemistry by flow cytometry and demonstrated a significant decrease in 'false-positive' events during cellular analysis, due to the efficient eradication of non-specifically reactive cells and tissue debris from the cell populations of interest. Therefore, it was possible to conclude that flow through an ultrasonic acoustic system was capable of providing a non-destructive method for the hyper-purification of primary derived cell populations, with potential exploitations throughout the fields of cellular research, medical diagnostics and clinical therapies.

Comparative analysis of whole-blood interferon-γ and flow cytometry assays for detecting post-treatment immune responses in patients with active tuberculosis

BACKGROUND

Intracellular cytokine flow cytometry (ICCFC) has been explored to detect tuberculosis (TB) infections; however, there are little data regarding its use to examine the dynamic responses of Mycobacterium tuberculosis (MTB)-specific T-cells after anti-tuberculous therapy. The aim of this study was to analyze both dynamic changes in functional MTB antigen-specific T-cell subsets and interferon-gamma (IFN-γ) levels using ICCFC and the QuantiFERON-TB Gold In-Tube (QFT-IT) test, respectively, following anti-tuberculous treatment in patients with active TB.

METHODS

Twenty-six patients with active TB were enrolled in the study, and QFT-IT and ICCFC were performed simultaneously both before and after treatment. IFN-γ levels (QFT-IT test) and the numbers of IFN-γ- or tumor necrosis factor-alpha (TNF-α)-expressing T-cells (ICCFC assay) were examined after stimulation with MTB antigen.

RESULTS

There was no significant reduction in the mean IFN-γ concentrations measured by the QFT-IT test after anti-tuberculous treatment (P = 0.314). ICCFC analysis showed that the numbers of IFN-γ(+) /CD4(-) T-cells, and CD4(+) T-cells producing TNF-α, either alone or in combination with IFN-γ, were significantly reduced after anti-tuberculous treatment. The IFN-γ(+) /TNF-α(+) /CD4(+) T-cell subset showed the greatest difference between untreated and treated patients with active TB (area under the curve = 0.734, P = 0.004).

CONCLUSIONS

Unlike the QFT-IT test, ICCFC provides diverse immunological information about dynamic changes in the number of MTB antigen-specific T-cells following anti-tuberculous therapy. Thus, analysis of MTB antigen-stimulated T-cell responses using ICCFC might have a role to play in monitoring treatment responses in patients with active TB.

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

Differentiation between active and latent TB is a diagnostic challenge in TB-endemic regions. The commercially available IFN-γ-release assays are unsuitable for achieving this discrimination. We, therefore, screened ESAT-6 and CFP-10 proteins through population coverage analysis to identify minimal sets of peptides that can discriminate between these two forms of TB in a North Indian population. Comparing the diagnostic performance of a set of 2 ESAT-6 peptides (positions: 16-36; 59-79) to that of the QuantiFERON(®)-TB Gold IT (QFTGIT) assay, we observed significant difference in IFN-γ and TNF-α levels between patients (n = 15) and their age- and sex-matched healthy household contacts (n = 15). While the mean (±SD) IFNγ titer was 241.8 (±219.24) IU/ml for patients, the same in controls was 564.2 (±334.82) IU/ml (p = 0.039). Similarly the TNFα response was significantly higher in patients, compared to controls (796.47 ± 175.21 IU/ml vs. 481.81 ± 378.72 IU/ml; p = 0.047). IL-4 response to these peptides was non- discriminatory between the two groups. The QFTGIT Assay, however, elicited no significant difference in IFN-γ, TNF-α or IL-4 levels. Hence we conclude that IFN-γ or TNF-α response to these ESAT-6 peptides has the potential to differentiate between active and latent TB in our population.

IFNγ/TNFα specific-cells and effector memory phenotype associate with active tuberculosis

OBJECTIVES

Controversial results were reported on the role of polyfunctional T-cells in tuberculosis (TB). Our aim was to simultaneously characterize the Mycobacterium tuberculosis (Mtb)-specific immune response as cytokine production and memory phenotype by flow cytometry after in vitro stimulation with region of difference 1 ("RD1") recombinant proteins (ESAT-6 and CFP-10) in patients at different TB stage in a low TB endemic country. To assess the specificity of these findings, we evaluated the response to cytomegalovirus (CMV), an unrelated antigen.

METHODS

We enrolled subjects with active TB, cured TB, latent TB infection (LTBI). Cytokine and phenotype profiles of T-cells from whole blood stimulated with "RD1" proteins and CMV were characterized by multi-parametric flow cytometry.

RESULTS

Bifunctional IFNγ(+) TNFα(+) CD4(+) T-cells and effector memory phenotype significantly associated with active TB compared to the LTBI group (p = 0.008, at least p ≤ 0.009 respectively) whereas "RD1"-T-cell response in cured TB and LTBI was characterized by a central memory phenotype (at least p ≤ 0.013 and p ≤ 0.004 respectively vs active TB). In contrast, response to CMV antigen was not associated with a TB-specific status.

CONCLUSION

We identified qualitative associations between Mtb-specific T-cell and TB status in terms of functional capacity and memory status. These immune correlates may be helpful to trace natural history of TB.

Antigen-specific CD4- and CD8-positive signatures in different phases of Mycobacterium tuberculosis infection

Current diagnostic standards for Mycobacterium tuberculosis (MTB) infection do not distinguish between active and latent tuberculosis (TB). To identify specific biomarkers characterizing the different forms of TB infection, we investigated in parallel with the QuantiFERON -TB Gold In-Tube (QFT-IT) the use of flow cytometry measuring CD4 and CD8 MTB-specific immune response in 17 active-TB patients, 21 health care workers (HCW), 14 recent contacts of TB patients (RC-TB), and 10 bacille Calmette Guerin (BCG)-vaccinated healthy controls (BCG-HC). A correlation (r = 0.4526, P = 0.0002) was found only between the amount of IFN-γ measured by QFT-IT and the frequency of CD4+/CD69+/IFN-γ+ T cells. The frequency of CD4+/CD69+/IFNγ+ responding T cells was higher in active-TB patients (0.254 ± 0.336%, P < 0.01) compared to the other groups. The response of QFT-IT antigen-specific CD8+/CD69+/IFNγ+ T cells was significantly higher in RC-TB (0.245 ± 0.305%, P < 0.05) compared to the other study groups.