Molecular signatures distinguishing active from latent tuberculosis in peripheral blood mononuclear cells, after in vitro antigenic stimulation with purified protein derivative of tuberculin (PPD) or Candida: a preliminary report

Impact and prognosis of the expression of IFN-α among tuberculosis patients

Mycobacterium tuberculosis (M.tb) infection stimulates the release of cytokines, including interferons (IFNs). IFNs are initiators, regulators, and effectors of innate and adaptive immunity. Accordingly, the expression levels of Type I (α, β) and II (γ) IFNs, among untreated tuberculosis (TB) patients and household contacts (HHC) clinically free of TB was assessed. A total of 264 individuals (TB patients-123; HHC-86; laboratory volunteers-55; Treated TB patients-36) were enrolled for this study. IFN-α mRNA expression levels predominated compared to IFN-γ and IFN-β among untreated TB patients. IFN-α transcripts were ~3.5 folds higher in TB patients compared to HHC, (p<0.0001). High expression of IFN-α was seen among 46% (56/ 123) of the TB patients and 26%, (22/86) of HHCs. The expression levels of IFN-α correlated with that of IFN transcriptional release factor 7 (IRF) (p<0.0001). In contrast, an inverse relationship exists between PGE2 and IFN-α expression levels; high IFN-α expressers were associated with low levels of PGE2 and vice-versa (Spearman’s rho = -0.563; p<0.0001). In-vitro, IFN-α failed to restrict the replication of intracellular M.tb. The anti-mycobacterial activity of IFN-γ was compromised in the presence of IFN-α, but not by IFN-β. The expression of IFN-α and β diminished or is absent, among successfully treated TB patients. These observations suggest the utility of assessment of Type I IFNs expression levels as a prognostic marker to monitor tuberculosis patient response to chemotherapy because changes in Type I IFNs expression are expected to precede the clearance and /reduction in bacterial load.

Decoding the similarities and specific differences between latent and active tuberculosis infections based on consistently differential expression networks

Although intensive efforts have been devoted to investigating latent tuberculosis (LTB) and active tuberculosis (PTB) infections, the similarities and differences in the host responses to these two closely associated stages remain elusive, probably due to the difficulty in identifying informative genes related to LTB using traditional methods. Herein, we developed a framework known as the consistently differential expression network to identify tuberculosis (TB)-related gene pairs by combining microarray profiles and protein-protein interactions. We thus obtained 774 and 693 pairs corresponding to the PTB and LTB stages, respectively. The PTB-specific genes showed higher expression values and fold-changes than the LTB-specific genes. Furthermore, the PTB-related pairs generally had higher expression correlations and would be more activated compared to their LTB-related counterparts. The module analysis implied that the detected gene pairs tended to cluster in the topological and functional modules. Functional analysis indicated that the LTB- and PTB-specific genes were enriched in different pathways and had remarkably different locations in the NF-κB signaling pathway. Finally, we showed that the identified genes and gene pairs had the potential to distinguish TB patients in different disease stages and could be considered as drug targets for the specific treatment of patients with LTB or PTB.

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.

A Two-Way Proteome Microarray Strategy to Identify Novel Mycobacterium tuberculosis-Human Interactors

Tuberculosis (TB) is still a serious threat to human health which is caused by mycobacterium tuberculosis (Mtb). The main reason for failure to eliminate TB is lack of clearly understanding the molecular mechanism of Mtb pathogenesis. Determining human Mtb-interacting proteins enables us to characterize the mechanism and identify potential molecular targets for TB diagnosis and treatment. However, experimentally systematic Mtb interactors are not readily available. In this study, we performed an unbiased, comprehensive two-way proteome microarray based approach to systematically screen global human Mtb interactors and determine the binding partners of Mtb effectors. Our results, for the first time, screened 84 potential human Mtb interactors. Bioinformatic analysis further highlighted these protein candidates might engage in a wide range of cellular functions such as activation of DNA endogenous promoters, transcription of DNA/RNA and necrosis, as well as immune-related signaling pathways. Then, using Mtb proteome microarray followed His tagged pull-down assay and Co-IP, we identified one interacting partner (Rv0577) for the protein candidate NRF1 and three binding partners (Rv0577, Rv2117, Rv2423) for SMAD2, respectively. This study gives new insights into the profile of global Mtb interactors potentially involved in Mtb pathogenesis and demonstrates a powerful strategy in the discovery of Mtb effectors.

Shaping the niche in macrophages: Genetic diversity of the M. tuberculosis complex and its consequences for the infected host

Pathogenic mycobacteria of the Mycobacterium tuberculosis complex (MTBC) have co-evolved with their individual hosts and are able to transform the hostile environment of the macrophage into a permissive cellular habitat. The impact of MTBC genetic variability has long been considered largely unimportant in TB pathogenesis. Members of the MTBC can now be distinguished into three major phylogenetic groups consisting of 7 phylogenetic lineages and more than 30 so called sub-lineages/subgroups. MTBC genetic diversity indeed influences the transmissibility and virulence of clinical MTBC isolates as well as the immune response and the clinical outcome. Here we review the genetic diversity and epidemiology of MTBC strains and describe the current knowledge about the host immune response to infection with MTBC clinical isolates using human and murine experimental model systems in vivo and in vitro. We discuss the role of innate cytokines in detail and portray two in our group recently developed approaches to characterize the intracellular niches of MTBC strains. Characterizing the niches and deciphering the strategies of MTBC strains to transform an antibacterial effector cell into a permissive cellular habitat offers the opportunity to identify strain- and lineage-specific key factors which may represent targets for novel antimicrobial or host directed therapies for tuberculosis.

Identification of Host Proteins Predictive of Early Stage Mycobacterium tuberculosis Infection

The objective of this study was to identify blood-based protein biomarkers of early stage Mycobacterium tuberculosis (Mtb) infection. We utilized plasma and serum specimens from TB patients and their contacts (age ≥ 12) enrolled in a household contact study in Uganda. In the discovery phase cross-sectional samples from 104 HIV-uninfected persons classified as either active TB, latent Mtb infection (LTBI), tuberculin skin test (TST) converters, or persistent TST-negative were analyzed. Two hundred eighty-nine statistically significant (false discovery rate corrected p < 0.05) differentially expressed proteins were identified across all comparisons. Proteins associated with cellular immunity and lipid metabolism were induced early after Mtb infection. One hundred and fifty-nine proteins were selected for a targeted mass spectrometry assay. A set of longitudinal samples from 52 TST-negative subjects who converted to TST-positive or remained TST-negative were analyzed, and multivariate logistic regression was used to identify unique protein panels able to predict TST conversion with cross-validated AUC > 0.85. Panel performance was confirmed with an independent validation set of longitudinal samples from 16 subjects. These candidate protein biomarkers may allow for the identification of recently Mtb infected individuals at highest risk for developing active TB and most likely to benefit from preventive therapy.

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Changes in host proteins can be detected in M. tuberculosis infection, even prior to tuberculin skin test conversion.

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Early M. tuberculosis infection provoked host responses related to inflammation, immune-response, and lipid metabolism.

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Protein panels were able to predict tuberculin skin test conversion and development of latent M. tuberculosis infection.

Developing a diagnostic test that identifies recent M. tuberculosis infection would allow for targeted treatment of those persons most likely to progress to active tuberculosis (TB). Current tests for M. tuberculosis infection are unable to differentiate between latent M. tuberculosis infection (LTBI) and active TB, nor distinguish recent from remote infection. This study identified human host proteins capable of predicting tuberculin skin test conversion, and the development of LTBI. These candidate protein biomarkers may allow for the identification of recently Mtb infected individuals who are at highest risk for developing active TB and would most benefit from preventive therapy.

Diagnostic 'omics' for active tuberculosis

The decision to treat active tuberculosis (TB) is dependent on microbiological tests for the organism or evidence of disease compatible with TB in people with a high demographic risk of exposure. The tuberculin skin test and peripheral blood interferon-γ release assays do not distinguish active TB from a cleared or latent infection. Microbiological culture of mycobacteria is slow. Moreover, the sensitivities of culture and microscopy for acid-fast bacilli and nucleic acid detection by PCR are often compromised by difficulty in obtaining samples from the site of disease. Consequently, we need sensitive and rapid tests for easily obtained clinical samples, which can be deployed to assess patients exposed to TB, discriminate TB from other infectious, inflammatory or autoimmune diseases, and to identify subclinical TB in HIV-1 infected patients prior to commencing antiretroviral therapy. We discuss the evaluation of peripheral blood transcriptomics, proteomics and metabolomics to develop the next generation of rapid diagnostics for active TB. We catalogue the studies published to date seeking to discriminate active TB from healthy volunteers, patients with latent infection and those with other diseases. We identify the limitations of these studies and the barriers to their adoption in clinical practice. In so doing, we aim to develop a framework to guide our approach to discovery and development of diagnostic biomarkers for active TB.

Single-Cell Cytokine Gene Expression in Peripheral Blood Cells Correlates with Latent Tuberculosis Status

RNA flow cytometry (FISH-Flow) achieves high-throughput measurement of single-cell gene expression by combining in-situ nucleic acid hybridization with flow cytometry. We tested whether antigen-specific T-cell responses detected by FISH-Flow correlated with latent tuberculosis infection (LTBI), a condition affecting one-third of the world population. Peripheral-blood mononuclear cells from donors, identified as positive or negative for LTBI by current medical practice, were stimulated ex vivo with mycobacterial antigen. IFNG and IL2 mRNA production was assayed by FISH-Flow. Concurrently, immunophenotypes of the cytokine mRNA-positive cells were characterized by conventional, antibody-based staining of cell-surface markers. An association was found between donor LTBI status and antigen-specific induction of IFNG and IL2 transcripts. Induction of these cytokine genes, which was detected by FISH-Flow in a quarter the time required to see release of the corresponding proteins by ELISA, occurred primarily in activated CD4+ T cells via T-cell receptor engagement. Moreover, NK cells contributed to IFNG gene induction. These results show that antigen-driven induction of T-cell cytokine mRNA is a measurable single-cell parameter of the host responses associated with latent tuberculosis. FISH-Flow read-outs contribute a multi-scale dimension to the immunophenotyping afforded by antibody-based flow cytometry. Multi-scale, single-cell analyses may satisfy the need to determine disease stage and therapy response for tuberculosis and other infectious pathologies.

High levels of anti-tuberculin (IgG) antibodies correlate with the blocking of T-cell proliferation in individuals with high exposure to Mycobacterium tuberculosis

OBJECTIVES

To determine the effect of anti-tuberculin antibodies in the T-cell proliferation in response to tuberculin and Candida antigens in individuals with different levels of tuberculosis (TB) risk.

METHODS

Sixteen high-risk TB individuals, 30 with an intermediate TB risk (group A), and 45 with a low TB risk (group B), as well as 49 control individuals, were studied. Tuberculin skin test (TST) results were analyzed and serum levels of antibodies (IgG and IgM) against purified protein derivative (PPD) were measured by ELISA. Tuberculin and Candida antigens were used to stimulate T-cell proliferation in the presence of human AB serum or autologous serum.

RESULTS

High levels of anti-tuberculin IgG antibodies were found to be significantly associated with the blocking of T-cell proliferation responses in cultures stimulated with tuberculin but not with Candida antigens in the presence of autologous serum. This phenomenon was particularly frequent in high-risk individuals with high levels of anti-tuberculin IgG antibodies in the autologous serum when compared to the other risk groups, which exhibited lower levels of anti-tuberculin antibodies.

CONCLUSIONS

Although cellular immunity plays a central role in the protection against TB, humoral immunity is critical in the control of Mycobacterium tuberculosis infection in high-risk individuals with latent TB infection.

Identifcation of differentially expressed long non-coding RNAs in CD4+ T cells response to latent tuberculosis infection

Objective

To identify differentially expressed long non-coding RNAs (lncRNAs) in CD4⁺ T cells triggered upon latent tuberculosis (TB) infection.

Methods

Expression profiles of lncRNAs and mRNAs in CD4⁺ T cells from individuals with latent TB infection (LTBI), active TB and healthy controls were analyzed by microarray assay and four lncRNAs were selected for validation using real time-quantitative polymerase chain reaction (RT-qPCR). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway based approaches were used to investigate biological functions and signaling pathways affected by the differentially expressed mRNAs.

Results

LncRNAs and mRNAs in CD4⁺ T cells were involved in LTBI and active TB disease. Compared with healthy controls, 449 lncRNAs and 461 mRNAs were deregulated in LTBI group, 1,113 lncRNAs and 1,490 mRNAs were deregulated in active TB group, as well as 163 lncRNAs and 187 mRNAs were differentially expressed in both LTBI and active TB group. It was worth noting that 41 lncRNAs and 60 mRNAs were deregulated between three groups. Most deregulated lncRNAs were from intergenic regions (∼50%), natural antisense to protein-coding loci (∼20%), or intronic antisense to protein-coding loci (∼10%). Significantly enriched signaling pathways based on deregulated mRNAs were mainly involved in mitogen-activated protein kinase (MAPK) signaling pathway, cytokine–cytokine receptor interaction, Toll-like receptor signaling pathway, etc.

Conclusions

The study was the first report of differentially expressed lncRNAs in CD4⁺ T cells response to TB infection and indicated that some lncRNAs may be involved in regulating host immune response to TB infection. Future studies are needed to further elucidate potential roles of these deregulated lncRNAs in LTBI and its reactivation.

Unexpected role for IL-17 in protective immunity against hypervirulent Mycobacterium tuberculosis HN878 infection

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), infects one third of the world's population. Among these infections, clinical isolates belonging to the W-Beijing appear to be emerging, representing about 50% of Mtb isolates in East Asia, and about 13% of all Mtb isolates worldwide. In animal models, infection with W-Beijing strain, Mtb HN878, is considered "hypervirulent" as it results in increased mortality and causes exacerbated immunopathology in infected animals. We had previously shown the Interleukin (IL) -17 pathway is dispensable for primary immunity against infection with the lab adapted Mtb H37Rv strain. However, it is not known whether IL-17 has any role to play in protective immunity against infection with clinical Mtb isolates. We report here that lab adapted Mtb strains, such as H37Rv, or less virulent Mtb clinical isolates, such as Mtb CDC1551, do not require IL-17 for protective immunity against infection while infection with Mtb HN878 requires IL-17 for early protective immunity. Unexpectedly, Mtb HN878 induces robust production of IL-1β through a TLR-2-dependent mechanism, which supports potent IL-17 responses. We also show that the role for IL-17 in mediating protective immunity against Mtb HN878 is through IL-17 Receptor signaling in non-hematopoietic cells, mediating the induction of the chemokine, CXCL-13, which is required for localization of T cells within lung lymphoid follicles. Correct T cell localization within lymphoid follicles in the lung is required for maximal macrophage activation and Mtb control. Since IL-17 has a critical role in vaccine-induced immunity against TB, our results have far reaching implications for the design of vaccines and therapies to prevent and treat emerging Mtb strains. In addition, our data changes the existing paradigm that IL-17 is dispensable for primary immunity against Mtb infection, and instead suggests a differential role for IL-17 in early protective immunity against emerging Mtb strains.

Tuberculosis antigen-induced expression of IFN-α in tuberculosis patients inhibits production of IL-1β

The mechanism by which IFN-α regulates the host response to Mycobacterium tuberculosis (M.tb) infection in humans is poorly understood. In the present study, we found that freshly isolated pleural fluid mononuclear cells (PFMCs) from tuberculous pleural effusion but not peripheral blood mononuclear cells (PBMCs) spontaneously expressed IFN-α and IL-1β in vivo. In addition, exogenous IFN-α significantly inhibited production of IL-1β in PFMCs after stimulation with Bacillus Calmette-Guérin (BCG). To further evaluate the effect of endogenous IFN-α on BCG-induced IL-1β production, a neutralizing antibody to IFN-α was added to the cultures of BCG-stimulated PFMCs. As expected, neutralization of IFN-α by antibody significantly enhanced the production of IL-1β. Notably, we showed that IFN-α inhibited production of IL-1β through 2 distinct mechanisms: IFN-α signaling, via the STAT1 transcription factor, suppressed caspase-1-dependent IL-1β maturation, and IFN-α induced the production of IL-10 in a STAT1-dependent manner in which IL-10 reduced the abundance of IL-1β. In contrast, we found that IFN-α enhanced the production of IFN-γ, and IFN-γ also suppressed IL-1β production in the PFMCs during BCG stimulation. Our findings demonstrate that IFN-α employs distinct pathways for regulating IL-1β production and reveal that in the case of M.tb infection, the induction of IFN-α and IFN-γ might be associated with M.tb immune escape and disease progression in infected humans.-Ma, J., Yang, B., Yu, S., Zhang, Y., Zhang, X., Lao, S., Chen, X., Li, B., Wu, C. Tuberculosis antigen-induced expression of IFN-α in tuberculosis patients inhibits production of IL-1β.

Association study of genes controlling IL-12-dependent IFN-γ immunity: STAT4 alleles increase risk of pulmonary tuberculosis in Morocco

Background. Only a minority of individuals infected with Mycobacterium tuberculosis develop clinical tuberculosis. Genetic epidemiological evidence suggests that pulmonary tuberculosis has a strong human genetic component. Previous genetic findings in Mendelian predisposition to more severe mycobacterial infections, including by M. tuberculosis, underlined the importance of the interleukin 12 (IL-12)/interferon γ (IFN-γ) circuit in antimycobacterial immunity.

Methods. We conducted an association study in Morocco between pulmonary tuberculosis and a panel of single-nucleotide polymorphisms (SNPs) covering 14 core IL-12/IFN-γ circuit genes. The analyses were performed in a discovery family-based sample followed by replication in a case-control population.

Results. Out of 228 SNPs tested in the family-based sample, 6 STAT4 SNPs were associated with pulmonary tuberculosis (P = .0013–.01). We replicated the same direction of association for 1 cluster of 3 SNPs encompassing the promoter region of STAT4. In the combined sample, the association was stronger among younger subjects (pulmonary tuberculosis onset <25 years) with an odds ratio of developing pulmonary tuberculosis at rs897200 for GG vs AG/AA subjects of 1.47 (1.06–2.04). Previous functional experiments showed that the G allele of rs897200 was associated with lower STAT4 expression.

Conclusions. Our present findings in a Moroccan population support an association of pulmonary tuberculosis with STAT4 promoter-region polymorphisms that may impact STAT4 expression.

Identification of a 251 gene expression signature that can accurately detect M. tuberculosis in patients with and without HIV co-infection

Background

Co-infection with tuberculosis (TB) is the leading cause of death in HIV-infected individuals. However, diagnosis of TB, especially in the presence of an HIV co-infection, can be limiting due to the high inaccuracy associated with the use of conventional diagnostic methods. Here we report a gene signature that can identify a tuberculosis infection in patients co-infected with HIV as well as in the absence of HIV.

Methods

We analyzed global gene expression data from peripheral blood mononuclear cell (PBMC) samples of patients that were either mono-infected with HIV or co-infected with HIV/TB and used support vector machines to identify a gene signature that can distinguish between the two classes. We then validated our results using publically available gene expression data from patients mono-infected with TB.

Results

Our analysis successfully identified a 251-gene signature that accurately distinguishes patients co-infected with HIV/TB from those infected with HIV only, with an overall accuracy of 81.4% (sensitivity = 76.2%, specificity = 86.4%). Furthermore, we show that our 251-gene signature can also accurately distinguish patients with active TB in the absence of an HIV infection from both patients with a latent TB infection and healthy controls (88.9–94.7% accuracy; 69.2–90% sensitivity and 90.3–100% specificity). We also demonstrate that the expression levels of the 251-gene signature diminish as a correlate of the length of TB treatment.

Conclusions

A 251-gene signature is described to (a) detect TB in the presence or absence of an HIV co-infection, and (b) assess response to treatment following anti-TB therapy.

S100A8/A9 proteins mediate neutrophilic inflammation and lung pathology during tuberculosis

RATIONALE

A hallmark of pulmonary tuberculosis (TB) is the formation of granulomas. However, the immune factors that drive the formation of a protective granuloma during latent TB, and the factors that drive the formation of inflammatory granulomas during active TB, are not well defined.

OBJECTIVES

The objective of this study was to identify the underlying immune mechanisms involved in formation of inflammatory granulomas seen during active TB.

METHODS

The immune mediators involved in inflammatory granuloma formation during TB were assessed using human samples and experimental models of Mycobacterium tuberculosis infection, using molecular and immunologic techniques.

MEASUREMENTS AND MAIN RESULTS

We demonstrate that in human patients with active TB and in nonhuman primate models of M. tuberculosis infection, neutrophils producing S100 proteins are dominant within the inflammatory lung granulomas seen during active TB. Using the mouse model of TB, we demonstrate that the exacerbated lung inflammation seen as a result of neutrophilic accumulation is dependent on S100A8/A9 proteins. S100A8/A9 proteins promote neutrophil accumulation by inducing production of proinflammatory chemokines and cytokines, and influencing leukocyte trafficking. Importantly, serum levels of S100A8/A9 proteins along with neutrophil-associated chemokines, such as keratinocyte chemoattractant, can be used as potential surrogate biomarkers to assess lung inflammation and disease severity in human TB.

CONCLUSIONS

Our results thus show a major pathologic role for S100A8/A9 proteins in mediating neutrophil accumulation and inflammation associated with TB. Thus, targeting specific molecules, such as S100A8/A9 proteins, has the potential to decrease lung tissue damage without impacting protective immunity against TB.

Pattern recognition receptors and cytokines in Mycobacterium tuberculosis infection--the double-edged sword?

Tuberculosis, an infectious disease caused by Mycobacterium tuberculosis (Mtb), remains a major cause of human death worldwide. Innate immunity provides host defense against Mtb. Phagocytosis, characterized by recognition of Mtb by macrophages and dendritic cells (DCs), is the first step of the innate immune defense mechanism. The recognition of Mtb is mediated by pattern recognition receptors (PRRs), expressed on innate immune cells, including toll-like receptors (TLRs), complement receptors, nucleotide oligomerization domain like receptors, dendritic cell-specific intercellular adhesion molecule grabbing nonintegrin (DC-SIGN), mannose receptors, CD14 receptors, scavenger receptors, and FCγ receptors. Interaction of mycobacterial ligands with PRRs leads macrophages and DCs to secrete selected cytokines, which in turn induce interferon-γ- (IFNγ-) dominated immunity. IFNγ and other cytokines like tumor necrosis factor-α (TNFα) regulate mycobacterial growth, granuloma formation, and initiation of the adaptive immune response to Mtb and finally provide protection to the host. However, Mtb can evade destruction by antimicrobial defense mechanisms of the innate immune system as some components of the system may promote survival of the bacteria in these cells and facilitate pathogenesis. Thus, although innate immunity components generally play a protective role against Mtb, they may also facilitate Mtb survival. The involvement of selected PRRs and cytokines on these seemingly contradictory roles is discussed.

Impact of cytotoxic and targeted antineoplastic drugs on the validity of the mitogen-induced interferon-gamma release assay for latent tuberculosis infection: results of a prospective trial at a comprehensive cancer center

Abstract The T-SPOT.TB test (TS.TB), an interferon-gamma (IFN-γ) release assay (IGRA), is superior in diagnosing latent tuberculosis infection compared with the conventional tuberculin skin test (TST). However, whether cytotoxic chemotherapy and treatment with new-generation antineoplastic monoclonal antibodies affects the TS.TB is not certain. We evaluated the feasibility of using the TS.TB in this population. Sixteen cancer patients at high risk for tuberculosis exposure were prospectively evaluated with the TST and TS.TB. Blood samples were obtained 7.5 ± 89.3 days after the most recent cycle of antineoplastic therapy. Six patients (38%) were febrile within 24 h of blood sampling; high-dose corticosteroid therapy and profound treatment-induced neutropenia were present in 1 patient each. In all patients, TS.TB showed no evidence of latent tuberculosis infection. A robust mitogen-induced IFN-γ response was seen in samples from 14 patients (88%) despite therapy with high-dose corticosteroids, cyclophosphamide, fludarabine, gemtuzumab ozogamicin, and alemtuzumab. The presence of fever or profound neutropenia did not negatively impact mitogen response by peripheral lymphocytes. The 2 patients whose peripheral blood lymphocytes (> 500 cells/ml) failed to generate a cytokine response to ex vivo mitogen stimulation had refractory advanced cancer. Unlike the TST, a negative TS.TB provided interpretable results even in cancer patients undergoing new-generation immunosuppressive therapy.

The roles of microRNAs on tuberculosis infection: meaning or myth?

The central proteins for protection against tuberculosis are attributed to interferon-γ, tumor necrosis factor-α, interleukin (IL)-6 and IL-1β, while IL-10 primarily suppresses anti-mycobacterial responses. Several studies found alteration of expression profile of genes involved in anti-mycobacterial responses in macrophages and natural killer (NK) cells from active and latent tuberculosis and from tuberculosis and healthy controls. This alteration of cellular composition might be regulated by microRNAs (miRNAs). Albeit only 1% of the genomic transcripts in mammalian cells encode miRNA, they are predicted to control the activity of more than 60% of all protein-coding genes and they have a huge influence in pathogenesis theory, diagnosis and treatment approach to some diseases. Several miRNAs have been found to regulate T cell differentiation and function and have critical role in regulating the innate function of macrophages, dendritic cells and NK cells. Here, we have reviewed the role of miRNAs implicated in tuberculosis infection, especially related to their new roles in the molecular pathology of tuberculosis immunology and as new targets for future tuberculosis diagnostics.

Differential gene expression segregates cattle confirmed positive for bovine tuberculosis from antemortem tuberculosis test-false positive cattle originating from herds free of bovine tuberculosis

Antemortem tests for bovine tuberculosis (bTB) currently used in the US measure cell-mediated immune responses against Mycobacterium bovis. Postmortem tests for bTB rely on observation of gross and histologic lesions of bTB, followed by bacterial isolation or molecular diagnostics. Cumulative data from the state of Michigan indicates that 98 to 99% of cattle that react positively in antemortem tests are not confirmed positive for bTB at postmortem examination. Understanding the fundamental differences in gene regulation between antemortem test-false positive cattle and cattle that have bTB may allow identification of molecular markers that can be exploited to better separate infected from noninfected cattle. An immunospecific cDNA microarray was used to identify altered gene expression (P ≤ 0.01) of 122 gene features between antemortem test-false positive cattle and bTB-infected cattle following a 4-hour stimulation of whole blood with tuberculin. Further analysis using quantitative real-time PCR assays validated altered expression of 8 genes that had differential power (adj  P ≤ 0.05) to segregate cattle confirmed positive for bovine tuberculosis from antemortem tuberculosis test-false positive cattle originating from herds free of bovine tuberculosis.

Cellular and humoral mechanisms involved in the control of tuberculosis

Mycobacterium tuberculosis (Mtb) infection is a major international public health problem. One-third of the world's population is thought to have latent tuberculosis, a condition where individuals are infected by the intracellular bacteria without active disease but are at risk for reactivation, if their immune system fails. Here, we discuss the role of nonspecific inflammatory responses mediated by cytokines and chemokines induced by interaction of innate receptors expressed in macrophages and dendritic cells (DCs). We also review current information regarding the importance of several cytokines including IL-17/IL-23 in the development of protective cellular and antibody-mediated protective responses against Mtb and their influence in containment of the infection. Finally, in this paper, emphasis is placed on the mechanisms of failure of Mtb control, including the immune dysregulation induced by the treatment with biological drugs in different autoimmune diseases. Further functional studies, focused on the mechanisms involved in the early host-Mtb interactions and the interplay between host innate and acquired immunity against Mtb, may be helpful to improve the understanding of protective responses in the lung and in the development of novel therapeutic and prophylactic tools in TB.

Dynamic roles of type I and type II IFNs in early infection with Mycobacterium tuberculosis

Although the protective role of type II IFN, or IFN-γ, against Mycobacterium tuberculosis has been established, the effects of type I IFNs are still unclear. One potential confounding factor is the overlap of function between the two signaling pathways. We used mice carrying null mutations in the type I IFNR, type II IFNR, or both and compared their immune responses to those of wild-type mice following aerosol infection with M. tuberculosis. We discovered that, in the absence of a response to IFN-γ, type I IFNs play a nonredundant protective role against tuberculosis. Mice unable to respond to both types of IFNs had more severe lung histopathology for similar bacterial loads and died significantly earlier than did mice with impaired IFN-γ signaling alone. We excluded a role for type I IFN in T cell recruitment, which was IFN-γ dependent, whereas both types of IFNs were required for optimal NK cell recruitment to the lungs. Type I IFN had a time-dependent influence on the composition of lung myeloid cell populations, in particular by limiting the abundance of M. tuberculosis-infected recruited macrophages after the onset of adaptive immunity. We confirmed that response to IFN-γ was essential to control intracellular mycobacterial growth, without any additional effect of type I IFN. Together, our results imply a model in which type I IFN limit the number of target cells that M. tuberculosis can infect in the lungs, whereas IFN-γ enhances their ability to restrict bacterial growth.

The role of interleukin-15 in inflammation and immune responses to infection: implications for its therapeutic use

Interleukin-15 (IL-15) is a pleiotropic cytokine with a broad range of biological functions in many diverse cell types. It plays a major role in the development of inflammatory and protective immune responses to microbial invaders and parasites by modulating immune cells of both the innate and adaptive immune systems. This review provides an overview of the mechanisms by which IL-15 modulates the host response to infectious agents and its utility as a cytokine adjuvant in vaccines against infectious pathogens.

Comparison of interferon-γ-, interleukin (IL)-17- and IL-22-expressing CD4 T cells, IL-22-expressing granulocytes and proinflammatory cytokines during latent and active tuberculosis infection

In this study, we investigated the role and expression of T helper type 17 (Th17) cells and Th17 cytokines in human tuberculosis. We show that the basal proportion of interferon (IFN)-γ-, interleukin (IL)-17- and IL-22-expressing CD4(+) T cells and IL-22-expressing granulocytes in peripheral blood were significantly lower in latently infected healthy individuals and active tuberculosis patients compared to healthy controls. In contrast, CD4(+) T cells expressing IL-17, IL-22 and IFN-γ were increased significantly following mycobacterial antigens stimulation in both latent and actively infected patients. Interestingly, proinflammatory IFN-γ and tumour necrosis factor (TNF)-α were increased following antigen stimulation in latent infection. Similarly, IL-1β, IL-4, IL-8, IL-22 and TNF-α were increased in the serum of latently infected individuals, whereas IL-6 and TNF-α were increased significantly in actively infected patients. Overall, we observed differential induction of IL-17-, IL-22- and IFN-γ-expressing CD4(+) T cells, IL-22-expressing granulocytes and proinflammatory cytokines in circulation and following antigenic stimulation in latent and active tuberculosis.

Analysis of microRNA expression profiling identifies miR-155 and miR-155* as potential diagnostic markers for active tuberculosis: a preliminary study

To explore biologic behaviors and disease relevance of microRNAs (miRNAs) in the development of active tuberculosis (ATB), we investigated the expression profile of Mycobacterium tuberculosis (MTB) purified protein derivative (PPD)-induced miRNAs to determine the specific miRNAs involved in the pathogenesis of ATB. The expression profile of miRNA under PPD challenge was first measured using microarray analysis in peripheral blood mononuclear cells isolated from ATB patients and healthy controls (HC). The remarkably reactive miRNAs were then validated in a larger cohort by quantitative real-time polymerase chain reaction (qRT-PCR). The receiver operating characteristic (ROC) curve was plotted to evaluate the diagnostic value of the determined PPD-responsive miRNAs. The potential targets for those miRNAs were also predicted by computational programs. Fourteen of 866 human miRNAs exhibited at least 1.8-fold difference in the ratio of expression level before and after stimulation with PPD between the ATB and HC groups. The qRT-PCR study validated the findings from microarray-based screening, in which miR-155 exhibited a fold change of 1.4 in the HC group and 3.7 in the ATB group upon PPD stimulation (p < 0.0001); miR-155* exhibited a fold change of 1.9 in the HC and 4.6 in the ATB group (p < 0.005). In ROC plots, the area under the curve was 0.8972 for miR-155 and 0.7945 for miR-155*. The background expression of these 2 microRNAs exhibited no differences between the ATB and HC groups. miR-155 and miR-155* exhibited characteristic expression by TB-specific antigen, suggesting that they can be potential diagnostic markers under the challenge of specific MTB antigens.

Immune response to Mycobacterium tuberculosis infection in the parietal pleura of patients with tuberculous pleurisy

The T lymphocyte-mediated immune response to Mycobacterium tuberculosis infection in the parietal pleura of patients with tuberculous pleurisy is unknown. The aim of this study was to investigate the immune response in the parietal pleura of tuberculous pleurisy compared with nonspecific pleuritis. We have measured the numbers of inflammatory cells particularly T-cell subsets (Th1/Th2/Th17/Treg cells) in biopsies of parietal pleura obtained from 14 subjects with proven tuberculous pleurisy compared with a control group of 12 subjects with nonspecific pleuritis. The number of CD3+, CD4+ and CCR4+ cells and the expression of RORC2 mRNA were significantly increased in the tuberculous pleurisy patients compared with the nonspecific pleuritis subjects. The number of toluidine blue+ cells, tryptase+ cells and GATA-3+ cells was significantly decreased in the parietal pleura of patients with tuberculous pleurisy compared with the control group of nonspecific pleuritis subjects. Logistic regression with receiver operator characteristic (ROC) analysis for the three single markers was performed and showed a better performance for GATA-3 with a sensitivity of 75%, a specificity of 100% and an AUC of 0.88. There was no significant difference between the two groups of subjects in the number of CD8, CD68, neutrophil elastase, interferon (IFN)-γ, STAT4, T-bet, CCR5, CXCR3, CRTH2, STAT6 and FOXP3 positive cells. Elevated CD3, CD4, CCR4 and Th17 cells and decreased mast cells and GATA-3+ cells in the parietal pleura distinguish patients with untreated tuberculous pleurisy from those with nonspecific pleuritis.

Candida albicans dampens host defense by downregulating IL-17 production

IL-17 is one of the key cytokines that stimulate host defense during a Candida infection. Several studies have demonstrated the capacity of Candida albicans to induce a Th17 response. Surprisingly, experiments employing live C. ablicans demonstrated a specific downregulation of host IL-17 secretion in human blood mononuclear cells (PBMCs). By avoiding the direct contact of live C. albicans and PBMCs, we demonstrate that this inhibition effect is mediated by a soluble factor released by live C. albicans. However, this effect is due neither to the releasing of C. albicans pathogen-associated molecular patterns nor to the alteration of different Th cell subtypes. Rather, we found that live C. albicans shifts tryptophan metabolism by inhibiting IDO expression away from kynurenines and toward 5-hydroxytryptophan metabolites. In addition, we show that these latter 5-hydroxytryptophan metabolites inhibit IL-17 production. In conclusion, live C. albicans inhibits host Th17 responses by modulatory effects on tryptophan metabolism.

Humoral immunity in tuberculin skin test anergy and its role in high-risk persons exposed to active tuberculosis

The most common test to identify latent tuberculosis is the tuberculin skin test that detects T cell responses of delayed type hypersensitivity type IV. Since it produces false negative reactions in active tuberculosis or in high-risk persons exposed to tuberculosis patients as shown in this report, we studied antibody profiles to explain the anergy of such responses in high-risk individuals without active infection. Our results showed that humoral immunity against tuberculin, regardless of the result of the tuberculin skin test is important for protection from active tuberculosis and that the presence of high antibody titers is a more reliable indicator of infection latency suggesting that latency can be based on the levels of antibodies together with in vitro proliferation of peripheral blood mononuclear cells in the presence of the purified protein derivative. Importantly, anti-tuberculin IgG antibody levels mediate the anergy described herein, which could also prevent reactivation of disease in high-risk individuals with high antibody titers. Such anti-tuberculin IgG antibodies were also found associated with blocking and/or stimulation of in vitro cultures of PBMC with tuberculin. In this regard, future studies need to establish if immune responses to Mycobacterium tuberculosis can generate a broad spectrum of reactions either toward Th1 responses favoring stimulation by cytokines or by antibodies and those toward diminished responses by Th2 cytokines or blocking by antibodies; possibly involving mechanisms of antibody dependent protection from Mtb by different subclasses of IgG.