Cross-modulation by transforming growth factor beta in human tuberculosis: suppression of antigen-driven blastogenesis and interferon gamma production

Immunopathology in human pulmonary tuberculosis: Inflammatory changes in the plasma milieu and impaired host immune cell functions

Host immune response is key for protection in tuberculosis, but the causative agent, Mycobacterium (M.) tuberculosis, manages to survive despite immune surveillance. Key mechanisms of immune protection have been identified, but the role of immunopathology in the peripheral blood of tuberculosis patients remains unclear. Tuberculosis immunopathology in the blood is characterised by patterns of immunosuppression and hyperinflammation. These seemingly contradictory findings and the pronounced heterogeneity made it difficult to interpret the results from previous studies and to derive implications of immunopathology. However, novel approaches based on comprehensive data analyses and revitalisation of an ancient plasma milieu in vitro assay connected inflammation with immunosuppressive factors in tuberculosis. Moreover, interrelations between the aberrant plasma milieu and immune cell pathology were observed. This review provides an overview of studies on changes in plasma milieu and discusses recent findings linking plasma factors to T-cell and monocyte/macrophage pathology in pulmonary tuberculosis patients.

Significance of extracellular vesicles in orchestration of immune responses in Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (M.tb), the causative agent of Tuberculosis, is an intracellular bacterium well known for its ability to subvert host energy and metabolic pathways to maintain its intracellular survival. For this purpose, the bacteria utilize various mechanisms of which extracellular vehicles (EVs) related mechanisms attracted more attention. EVs are nanosized particles that are released by almost all cell types containing active biomolecules from the cell of origin and can target bioactive pathways in the recipient cells upon uptake. It is hypothesized that M.tb dictates the processes of host EV biogenesis pathways, selectively incorporating its molecules into the host EV to direct immune responses in its favor. During infection with Mtb, both mycobacteria and host cells release EVs. The composition of these EVs varies over time, influenced by the physiological and nutritional state of the host environment. Additionally, different EV populations contribute differently to the pathogenesis of disease at various stages of illness participating in a complex interplay between host cells and pathogens. These interactions ultimately influence immune responses and disease outcomes. However, the precise mechanisms and roles of EVs in pathogenicity and disease outcomes remain to be fully elucidated. In this review, we explored the properties and function of EVs in the context of M.tb infection within the host microenvironment and discussed their capacity as a novel therapeutic strategy to combat tuberculosis.

Circular RNAs in tuberculosis: From mechanism of action to potential diagnostic biomarker

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M. tuberculosis), continues to be a major global health concern. Understanding the molecular intricacies of TB pathogenesis is crucial for developing effective diagnostic and therapeutic approaches. Circular RNAs (circRNAs), a class of single-stranded RNA molecules characterized by covalently closed loops, have recently emerged as potential diagnostic biomarkers in various diseases. CircRNAs have been demonstrated to modulate the host's immunological responses against TB, specifically by reducing monocyte apoptosis, augmenting autophagy, and facilitating macrophage polarization. This review comprehensively explores the roles and mechanisms of circRNAs in TB pathogenesis. We also discuss the growing body of evidence supporting their utility as promising diagnostic biomarkers for TB. By bridging the gap between fundamental circRNA biology and TB diagnostics, this review offers insights into the exciting potential of circRNAs in combatting this infectious disease.

NHS-IL12 and bintrafusp alfa combination therapy enhances antitumor activity in preclinical cancer models

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Combination therapy induced both adaptive and innate antitumor immunity.

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Combination therapy significantly enhanced antitumor activity.

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Combination therapy generated tumor antigen specific immune memory.

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Bintrafusp alfa mediated the reduction of lung metastases.

Combinatorial immunotherapy approaches are emerging as viable cancer therapeutic strategies for improving patient responses and outcomes. This study investigated whether two such immunotherapies, with complementary mechanisms of action, could enhance antitumor activity in murine tumor models. The immunocytokine NHS-IL12, and surrogate NHS-muIL12, are designed to deliver IL-12 and muIL-12, respectively, to the tumor microenvironment (TME) to activate NK cells and CD8⁺ T cells and increase their cytotoxic functions. Bintrafusp alfa (BA) is a bifunctional fusion protein composed of the extracellular domains of the TGF-β receptor II to function as a TGF-β “trap” fused to a human IgG1 antibody blocking PD-L1. With this dual-targeting strategy, BA enhances efficacy over that of monotherapies in preclinical studies. In this study, NHS-muIL12 and BA combination therapy enhanced antitumor activity, prolonged survival, and induced tumor-specific antitumor immunity. This combination therapy increased tumor-specific CD8⁺ T cells and induced immune profiles, consistent with the activation of both adaptive and innate immune systems. In addition, BA reduced lung metastasis in the 4T1 model. Collectively, these findings could support clinical trials designed to investigate NHS-IL12 and BA combination therapy for patients with advanced solid tumors

The multi-faceted roles of TGF-β in regulation of immunity to infection

Transforming Growth Factor-β is a potent regulator of the immune system, acting at every stage from thymic differentiation, population of the periphery, control of responsiveness, tissue repair and generation of memory. It is therefore a central player in the immune response to infectious pathogens, but its contribution is often clouded by multiple roles acting on different cells in time and space. Hence, context is all-important in understanding when TGF-β is beneficial or detrimental to the outcome of infection. In this review, a full range of infectious agents from viruses to helminth parasites are explored within this framework, drawing contrasts and general conclusions about the importance of TGF-β in these diseases.

Integrative Multi-Omics Reveals Serum Markers of Tuberculosis in Advanced HIV

Tuberculosis (TB) accounts for disproportionate morbidity and mortality among persons living with HIV (PLWH). Conventional methods of TB diagnosis, including smear microscopy and Xpert MTB/RIF, have lower sensitivity in PLWH. Novel high-throughput approaches, such as miRNAomics and metabolomics, may advance our ability to recognize subclinical and difficult-to-diagnose TB, especially in very advanced HIV. We conducted a case-control study leveraging REMEMBER, a multi-country, open-label randomized controlled trial comparing 4-drug empiric standard TB treatment with isoniazid preventive therapy in PLWH initiating antiretroviral therapy (ART) with CD4 cell counts <50 cells/μL. Twenty-three cases of incident TB were site-matched with 32 controls to identify microRNAs (miRNAs), metabolites, and cytokines/chemokines, associated with the development of newly diagnosed TB in PLWH. Differentially expressed miRNA analysis revealed 11 altered miRNAs with a fold change higher than 1.4 or lower than -1.4 in cases relative to controls (p<0.05). Our analysis revealed no differentially abundant metabolites between cases and controls. We found higher TNFα and IP-10/CXCL10 in cases (p=0.011, p=0.0005), and higher MDC/CCL22 in controls (p=0.0072). A decision-tree algorithm identified gamma-glutamylthreonine and hsa-miR-215-5p as the optimal variables to classify incident TB cases (AUC 0.965; 95% CI 0.925-1.000). hsa-miR-215-5p, which targets genes in the TGF-β signaling pathway, was downregulated in cases. Gamma-glutamylthreonine, a breakdown product of protein catabolism, was less abundant in cases. To our knowledge, this is one of the first uses of a multi-omics approach to identify incident TB in severely immunosuppressed PLWH.

Comparison of biochemical parameters and chemokine levels in pleural fluid between patients with anergic and non-anergic tuberculous pleural effusion

Pleural fluid (PF) immune response in anergic tuberculous pleural effusion (TPE) patients is poorly understood. This study aimed to compare PF biochemical parameters and chemokine levels between anergic and non-anergic TPE patients. Chemokine arrays, cytokine measurements, and flow cytometry were performed in 58 patients (TPE [non-anergic (n = 32) and anergic (n = 10)] and malignant pleural effusion (MPE) [n = 16]). PF adenosine deaminase 2 (ADA2) levels were significantly lower in anergic TPE patients than in non-anergic TPE patients (p = 0.048). Among the 40 chemokines tested, PF CCL27 levels were significantly higher in anergic TPE patients than in non-anergic TPE and MPE patients (p < 0.001). The percentage of CD4⁺CCR10⁺T cells in PF was higher in anergic TPE patients than in non-anergic TPE and MPE patients (p = 0.001). We reported here that CCL27/CCR10 interactions might contribute to pathophysiology in anergic TPE. PF CCL27 and CD4⁺CCR10⁺T cells may help in diagnosing TPE in patients with moderate elevation of PF ADA levels.

Target the Host, Kill the Bug; Targeting Host Respiratory Immunosuppressive Responses as a Novel Strategy to Improve Bacterial Clearance During Lung Infection

The lung is under constant pressure to protect the body from invading bacteria. An effective inflammatory immune response must be tightly orchestrated to ensure complete clearance of any invading bacteria, while simultaneously ensuring that inflammation is kept under strict control to preserve lung viability. Chronic bacterial lung infections are seen as a major threat to human life with the treatment of these infections becoming more arduous as the prevalence of antibiotic resistance becomes increasingly commonplace. In order to survive within the lung bacteria target the host immune system to prevent eradication. Many bacteria directly target inflammatory cells and cytokines to impair inflammatory responses. However, bacteria also have the capacity to take advantage of and strongly promote anti-inflammatory immune responses in the host lung to inhibit local pro-inflammatory responses that are critical to bacterial elimination. Host cells such as T regulatory cells and myeloid-derived suppressor cells are often enhanced in number and activity during chronic pulmonary infection. By increasing suppressive cell populations and cytokines, bacteria promote a permissive environment suitable for their prolonged survival. This review will explore the anti-inflammatory aspects of the lung immune system that are targeted by bacteria and how bacterial-induced immunosuppression could be inhibited through the use of host-directed therapies to improve treatment options for chronic lung infections.

Elevated Cyclic AMP Inhibits Mycobacterium tuberculosis-Stimulated T-cell IFN-γ Secretion Through Type I Protein Kinase A

Cyclic adenosine monophosphate (cAMP) is critical in immune regulation, and its role in tuberculosis infection remains unclear. We determined the levels of cAMP in peripheral blood mononuclear cells (PBMC) from tuberculosis patients and the mechanisms for cAMP suppression of IFN-γ production. PBMC from tuberculosis patients contained significantly elevated cAMP than latent tuberculosis infected subjects (LTBI), with an inverse correlation with IFN-γ production. Consistent with this, the expression of cAMP response element binding protein (CREB), activating transcription factor (ATF)-2 and c-Jun were reduced in tuberculosis patients compared with LTBI. PKA type I specific cAMP analogs inhibited Mtb-stimulated IFN-g production by PBMC through suppression of Mtb-induced IFN-γ promoter binding activities of CREB, ATF-2, and c-Jun and also miR155, the target miRNA of these transcription factors. Neutralizing both IL-10 and TGF-β1 or supplementation of IL-12 restored cAMP-suppressed IFN-g production. We conclude that increased cAMP inhibits IFN-g production through PKA type I pathway in tuberculosis infection.

Deletion of TGF-β1 Increases Bacterial Clearance by Cytotoxic T Cells in a Tuberculosis Granuloma Model

Mycobacterium tuberculosis is the pathogenic bacterium that causes tuberculosis (TB), one of the most lethal infectious diseases in the world. The only vaccine against TB is minimally protective, and multi-drug resistant TB necessitates new therapeutics to treat infection. Developing new therapies requires a better understanding of the complex host immune response to infection, including dissecting the processes leading to formation of granulomas, the dense cellular lesions associated with TB. In this work, we pair experimental and computational modeling studies to explore cytokine regulation in the context of TB. We use our next-generation hybrid multi-scale model of granuloma formation (GranSim) to capture molecular, cellular, and tissue scale dynamics of granuloma formation. We identify TGF-β1 as a major inhibitor of cytotoxic T-cell effector function in granulomas. Deletion of TGF-β1 from the system results in improved bacterial clearance and lesion sterilization. We also identify a novel dichotomous regulation of cytotoxic T cells and macrophages by TGF-β1 and IL-10, respectively. These findings suggest that increasing cytotoxic T-cell effector functions may increase bacterial clearance in granulomas and highlight potential new therapeutic targets for treating TB.

Pyopericardium with Cardiac Tamponade in a Nigerian Child with Acute Osteomyelitis

In pyopericardium, pus accumulates in the pericardial space as a result of infection by pyogenic organisms, most common of which are Staphylococcus aureus and Mycobacterium tuberculosis. These patients are at risk of cardiac tamponade. Apart from pericardiocentesis in the management of these patients, definitive drug treatment may pose a formidable challenge in a setting of coinfection as in patients with tuberculosis who are predisposed to secondary bacterial infections. This was the case of our patient. We here highlight the challenges faced with etiologic diagnosis in resource-limited settings.

T Cell Responses and Regulation and the Impact of In Vitro IL-10 and TGF-β Modulation During Treatment of Active Tuberculosis

Mycobacterium tuberculosis (Mtb) is particularly challenging for the immune system being an intracellular pathogen, and a variety of T cell subpopulations are activated by the host defence mechanism. In this study, we investigated T cell responses and regulation in active TB patients with drug-sensitive Mtb (N = 18) during 24 weeks of efficient anti-TB therapy. T cell activation, differentiation, regulatory T cell (Treg) subsets, Mtb-induced T cell proliferation and in vitro IL-10 and TGF-β modulation were analysed by flow cytometry at baseline and after 8 and 24 weeks of therapy, while soluble cytokines in culture supernatants were analysed by a 9-plex Luminex assay. Successful treatment resulted in significantly reduced co-expression of HLA-DR/CD38 and PD-1/CD38 on both CD4⁺ and CD8⁺ T cells, while the fraction of CD4⁺ CD25^high CD127^low Tregs (P = 0.017) and CD4⁺ CD25^high CD127^low CD147⁺ Tregs (P = 0.029) showed significant transient increase at week 8. In vitro blockade of IL-10/TGF-β upon Mtb antigen stimulation significantly lowered the fraction of ESAT-6-specific CD4⁺ CD25^high CD127^low Tregs at baseline (P = 0.047), while T cell proliferation and cytokine production were unaffected. Phenotypical and Mtb-specific T cell signatures may serve as markers of effective therapy, while the IL-10/TGF-β pathway could be a target for early inhibition to facilitate Mtb clearance. However, larger clinical studies are needed for verification before concluding.

Elevated serum IL-35 and increased expression of IL-35-p35 or -EBI3 in CD4(+)CD25(+) T cells in patients with active tuberculosis

Despite the recent appreciation of interleukin 35 (IL-35) function in inflammatory diseases, little is known for IL-35 response in patients with active tuberculosis (ATB). In the current study, we demonstrated that ATB patients exhibited increases in serum IL-35 and in mRNA expression of both subunits of IL-35 (p35 and EBI3) in white blood cells and peripheral blood mononuclear cells. Consistently, anti-TB drug treatment led to reduction in serum IL-35 level and p35 or EBI3 expression. TB infection was associated with expression of p35 or EBI3 protein in CD4(+) but not CD8(+) T cells. Most p35(+)CD4(+) T cells and EBI3(+)CD4(+) T cells expressed Treg-associated marker CD25. Our findings may be important in understanding immune pathogenesis of TB. IL-35 in the blood may potentially serve as a biomarker for immune status and prognosis in TB.

A novel role of Yin-Yang-1 in pulmonary tuberculosis through the regulation of the chemokine CCL4

Mycobacterium tuberculosis (M. tb) is the etiological agent of pulmonary tuberculosis (TB); this disease remains a worldwide health problem. Yin-Yang-1 (YY1) plays a major role in the maintenance and progression of some pulmonary diseases, including pulmonary fibrosis. However, the role of YY1 in TB remains unknown. The aim of this study was to elucidate the role of YY1 in the regulation of CCL4 and its implication in TB. We determined whether YY1 regulates CCL4 using reporter plasmids, ChIP and siRNA assays. Immunohistochemistry and digital pathology were used to measure the expression of YY1 and CCL4 in a mouse model of TB. A retrospective comparison of patients with TB and control subjects was used to measure the expression of YY1 and CCL4 using tissue microarrays. Our results showed that YY1 regulates the transcription of CCL4; moreover, YY1, CCL4 and TGF-β were overexpressed in the lung tissues of mice with TB during the late stages of the disease and the tissues of TB patients. The expression of CCL4 and TGF-β correlated with YY1 expression. In conclusion, YY1 regulates CCL4 transcription; moreover, YY1 is overexpressed in experimental and human TB and is positively correlated with CCL4 and TGF-β expression. Therefore, treatments that decrease YY1 expression may be a new therapeutic strategy against TB.

Effect of isoniazid preventive therapy on immune responses to mycobacterium tuberculosis: an open label randomised, controlled, exploratory study

Background

With the renewed emphasis to implement isoniazid preventive therapy (IPT) in Sub-Saharan Africa, we investigated the effect of IPT on immunological profiles among household contacts with latent tuberculosis.

Methods

Household contacts of confirmed tuberculosis patients were tested for latent tuberculosis using the QuantiFERON®-TB Gold In-Tube (QFN) assay and tuberculin skin test (TST). HIV negative contacts aged above 5 years, positive to both QFN and TST, were randomly assigned to IPT and monthly visits or monthly visits only. QFN culture supernatants from enrolment and six months’ follow-up were analysed for M.tb-specific Th1, Th2, Th17, and regulatory cytokines by Luminex assay, and for M.tb-specific IgG antibody concentrations by ELISA. Effects of IPT were assessed as the net cytokine and antibody production at the end of six months.

Results

Sixteen percent of contacts investigated (47/291) were randomised to IPT (n = 24) or no IPT (n = 23). After adjusting for baseline cytokine or antibody responses, and for presence of a BCG scar, IPT (compared to no IPT) resulted in a relative decline in M.tb-specific production of IFN gamma (adjusted mean difference at the end of six months (bootstrap 95 % confidence interval (CI), p-value) -1488.6 pg/ml ((−2682.5, −294.8), p = 0.01), and IL- 2 (−213.1 pg/ml (−419.2, −7.0), p = 0.04). A similar decline was found in anti-CFP-10 antibody levels (adjusted geometric mean ratio (bootstrap 95 % CI), p-value) 0.58 ((0.35, 0.98), p = 0.04). We found no effect on M.tb-specific Th2 or regulatory or Th17 cytokine responses, or on antibody concentrations to PPD and ESAT-6.

Conclusions

IPT led to a decrease in Th1 cytokine production, and also in the anti CFP-10 antibody concentration. This could be secondary to a reduction in mycobacterial burden or as a possible direct effect of isoniazid induced T cell apoptosis, and may have implications for protective immunity following IPT in tuberculosis-endemic countries.

Trial registration

ISRCTN registry, ISRCTN15705625. Registered on 30^th September 2015.

Latent tuberculosis infection--Revisiting and revising concepts

Host- and pathogen-specific factors interplay with the environment in a complex fashion to determine the outcome of infection with Mycobacterium tuberculosis (Mtb), resulting in one of three possible outcomes: cure, latency or active disease. Although much remains unknown about its pathophysiology, latent tuberculosis infection (LTBI) defined by immunologic evidence of Mtb infection is a continuum between self-cure and asymptomatic, yet active tuberculosis (TB) disease. Strain virulence, intensity of exposure to the index case, size of the bacterial inoculum, and host factors such as age and co-morbidities, each contribute to where one settles on the continuum. Currently, the diagnosis of LTBI is based on reactive tuberculin skin testing (TST) and/or a positive interferon-gamma release assay (IGRA). Neither diagnostic test reflects the activity of the infectious focus or the risk of progression to active TB. This is a critical shortcoming, as accurate and efficient detection of those with LTBI at higher risk of progression to TB disease would allow for provision of targeted preventive therapy to those most likely to benefit. Host biomarkers may prove of value in stratifying risk of development of TB. New guidelines are required for interpretation of discordance between TST and IGRA, which may be due in part to a lack of stability (that is reproducibility) of IGRA or TST results or to a delay in conversion of IGRA to positivity compared to TST. In this review, the authors elaborate on the definition, diagnosis, pathophysiology and natural history of LTBI, as well as promising methods for better stratifying risk of progression to TB. The review is centered on the human host and the clinical and epidemiologic features of LTBI that are relevant to the development of new and improved diagnostic tools.

Outcome of Mycobacterium tuberculosis and Toll-like receptor interaction: immune response or immune evasion?

Mycobacterium tuberculosis (M. tuberculosis), the causative agent of tuberculosis, is an intracellular bacterium capable of surviving and persisting within host mononuclear cells. The host response against tubercle bacilli is dominated by fine-tuned interaction of innate and adaptive immune responses. Toll-like receptors (TLRs) play a critical role in the formation of this immune response by facilitating in elaboration of protective T helper type 1 (Th1) cytokines and microbicidal molecules, but the intracellular persistence of M. tuberculosis in the phagosome and processing and presentation of TLR ligands by host antigen-presenting cell leads to continuous and chronic TLR2 signaling. The prolonged stimulation of TLR ultimately results in elaboration of immunosuppressive cytokines and downregulation of antigen presentation by major histocompatibility complex (MHC) class II and therefore becomes beneficial for M. tuberculosis, resulting in its continued survival inside macrophages. An understanding of the host-pathogen interaction in tuberculosis is important to delineate the mechanisms that can modulate the immune response toward protection. This review focuses on the role of TLRs in immune response and immune evasion and how M. tuberculosis maintains its dominance over the host during infection. A precise understanding of the TLRs and M. tuberculosis interaction will undoubtedly lead to the development of novel therapies to combat tuberculosis.

Immunoneuropathogenesis of HIV-1 clades B and C: role of redox expression and thiol modification

Previous studies have shown that, during infection, HIV-1 clade B and clade C differentially contribute to the neuropathogenesis and development of HIV-associated neurocognitive disorders (HANDs). The low-molecular-weight tripeptide glutathione (GSH) alters the redox balance and leads to the generation of reactive oxygen species, which play a significant role in the neuropathogenesis of HANDs. We hypothesized that the HIV-1 clade B and clade C viruses and their respective Tat proteins exert differential effects on monocyte-derived immature dendritic cells (IDCs) and neuroblastoma cells (SK-N-MC) by redox activation, which leads to immunoneuropathogenesis. The GSH/GSSG ratio and mRNA expression levels and protein modification of glutathione synthetase (GSS), glutathione peroxidase 1 (GPx1), superoxide dismutase 1 (SOD1), and catalase (CAT) were analyzed in IDCs infected with HIV-1 clade B or clade C as well as in cells treated with the respective Tat proteins. The results indicated that HIV-1 clade B virus and its Tat protein significantly increased the production of reactive oxygen species and reduced the GSH/GSSG ratio and subsequent downregulation of gene expression and protein modification of GSS, GPx1, SOD1, and CAT compared to infection with the clade C virus or treatment with the clade C Tat protein. Thus, our studies demonstrate that HIV-1 clades B and C exert differential effects of redox expression and thiol modification. HIV-1 clade B potentially induces oxidative stress, leading to more immunoneuropathogenesis than infection with HIV-1 clade C.

Ursolic and oleanolic acids as antimicrobial and immunomodulatory compounds for tuberculosis treatment

BACKGROUND

New alternatives for the treatment of Tuberculosis (TB) are urgently needed and medicinal plants represent a potential option. Chamaedora tepejilote and Lantana hispida are medicinal plants from Mexico and their hexanic extracts have shown antimycobacterial activity. Bioguided investigation of these extracts showed that the active compounds were ursolic acid (UA) and oleanolic acid (OA).

METHODS

The activity of UA and OA against Mycobacterium tuberculosis H37Rv, four monoresistant strains, and two drug-resistant clinical isolates were determined by MABA test. The intracellular activity of UA and OA against M. tuberculosis H37Rv and a MDR clinical isolate were evaluated in a macrophage cell line. Finally, the antitubercular activity of UA and OA was tested in BALB/c mice infected with M. tuberculosis H37Rv or a MDR strain, by determining pulmonary bacilli loads, tissue damage by automated histomorphometry, and expression of IFN-γ, TNF-α, and iNOS by quantitative RT-PCR.

RESULTS

The in vitro assay showed that the UA/OA mixture has synergistic activity. The intracellular activity of these compounds against M. tuberculosis H37Rv and a MDR clinical isolate in a macrophage cell line showed that both compounds, alone and in combination, were active against intracellular mycobacteria even at low doses. Moreover, when both compounds were used to treat BALB/c mice with TB induced by H37Rv or MDR bacilli, a significant reduction of bacterial loads and pneumonia were observed compared to the control. Interestingly, animals treated with UA and OA showed a higher expression of IFN-γ and TNF-α in their lungs, than control animals.

CONCLUSION

UA and OA showed antimicrobial activity plus an immune-stimulatory effect that permitted the control of experimental pulmonary TB.

Modulation of NKG2D expression in human CD8(+) T cells corresponding with tuberculosis drug cure

Background

Biomarkers predicting tuberculosis treatment response and cure would facilitate drug development. This study investigated expression patterns of the co-stimulation molecule NKG2D in human tuberculosis and treatment to determine its potential usefulness as a host biomarker of tuberculosis drug efficacy.

Methods

Tuberculosis patients (n = 26) were recruited in Lahore, Pakistan, at diagnosis and followed up during treatment. Household contacts (n = 24) were also recruited. NKG2D expression was measured by qRT-PCR in RNA samples both ex vivo and following overnight mycobacterial stimulation in vitro. Protein expression of NKG2D and granzyme B was measured by flow cytometry.

Results

NKG2D expression in newly diagnosed tuberculosis patients was similar to household contacts in ex vivo RNA, but was higher following in vitro stimulation. The NKG2D expression was dramatically reduced by intensive phase chemotherapy, in both ex vivo blood RNA and CD8⁺ T cell protein expression, but then reverted to higher levels after the continuation phase in successfully treated patients.

Conclusion

The changes in NKG2D expression through successful treatment reflect modulation of the peripheral cytotoxic T cell response. This likely reflects firstly in vivo stimulation by live Mycobacterium tuberculosis, followed by the response to dead bacilli, antigen-release and finally immunopathology resolution. Such changes in host peripheral gene expression, alongside clinical and microbiological indices, could be developed into a biosignature of tuberculosis drug-induced cure to be used in future clinical trials.

Frequency of regulatory T-cells in the peripheral blood of patients with pulmonary tuberculosis from shanxi province, china

BACKGROUND

Tuberculosis (TB) is a disease caused by the chronic and continuous infection of the pathogen Mycobacterium tuberculosis (M. tuberculosis). M. tuberculosis is an intracellular bacterial pathogen and is eliminated mainly through CD4(+) effector Th cells. M. tuberculosis induces regulatory T lymphocytes (Tregs) that mediate immune suppression by cell-to-cell contact or by secreting cytokines such as transforming growth factor-β (TGF-β). To understand the role of regulatory T-cells in the pathogenesis of TB, we have measured the in vivo frequency of regulatory T-cells and associated in vivo cytokine production in pulmonary tuberculosis patients.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we analyzed blood samples from 3 different populations (Group 1: patients with active TB, Group 2: patients recovered from TB and Group 3: healthy controls). We measured natural regulatory T-cell expression in peripheral blood using flow cytometry, and levels of blood serum IFN-γ and TGF-β1 using ELISA. The in vivo function of inductive regulatory T cells was mainly indicated by the expression of IFN-γ, TGF-β1, etc. Frequencyof natural regulatory T cells and inductive regulatory T cells in the peripheral blood samples from Group 1 patients were all significantly higher (P<0.05) than those from Groups 2 and 3.

CONCLUSION/SIGNIFICANCE

Our results indicate that frequency of natural regulatory T cells and inductive regulatory T cells are significantly higher in the peripheral blood of patients with active pulmonary tuberculosis. These findings have potential application in improving TB diagnostic methods.

IL-10 dependent suppression of type 1, type 2 and type 17 cytokines in active pulmonary tuberculosis

Background

Although Type 1 cytokine responses are considered protective in pulmonary tuberculosis (PTB), their role as well as those of Type 2, 17 and immunoregulatory cytokines in tuberculous lymphadenitis (TBL) and latent tuberculosis (LTB) have not been well studied.

Aim and Methods

To identify cytokine responses associated with pulmonary tuberculosis (TB), TB lymphadenitits and latent TB, we examined mycobacterial antigen-specific immune responses of PTB, TBL and LTB individuals. More specifically, we examined ESAT-6 and CFP-10 induced Type 1, Type 2 and Type 17 cytokine production and their regulation using multiplex ELISA.

Results

PTB individuals exhibited a significantly lower baseline as well as antigen-specific production of Type 1 (IFNγ, TNFα and IL-2); Type 2 (IL-4) and Type 17 (IL-17A and IL-17F) cytokines in comparison to both TBL and LTB individuals. TBL individuals exhibited significantly lower antigen-specific IFNγ responses alone in comparison to LTB individuals. Although, IL-10 levels were not significantly higher, neutralization of IL-10 during antigen stimulation resulted in significantly enhanced production of IFNγ, IL-4 and IL-17A in PTB individuals, indicating that IL-10 mediates (at least partially) the suppression of cytokine responses in PTB.

Conclusion

Pulmonary TB is characterized by an IL-10 dependent antigen-specific suppression of Type 1, Type 2 and Type 17 cytokines, reflecting an important association of these cytokines in the pathogenesis of active TB.

Foxp3+ regulatory T cells among tuberculosis patients: impact on prognosis and restoration of antigen specific IFN-γ producing T cells

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) and programmed death-1 (PD-1) molecules have emerged as pivotal players in immune suppression of chronic diseases. However, their impact on the disease severity, therapeutic response and restoration of immune response in human tuberculosis remains unclear. Here, we describe the possible role of Treg cells, their M. tuberculosis driven expansion and contribution of PD-1 pathway to the suppressive function of Treg cells among pulmonary tuberculosis (PTB) patients. Multicolor flow cytometry, cell culture, cells sorting and ELISA were employed to execute the study. Our results showed significant increase in frequency of antigen-reactive Treg cells, which gradually declined during successful therapy and paralleled with decline of M. tuberculosis-specific IL-10 along with elevation of IFN-γ production, and raising the IFN-γ/IL-4 ratio. Interestingly, persistence of Treg cells tightly correlated with MDR tuberculosis. Also, we show that blocking PD-1/PD-L1 pathway abrogates Treg-mediated suppression, suggesting that the PD-1/PD-L1 pathway is required for Treg-mediated suppression of the antigen-specific T cells. Treg cells possibly play a role in dampening the effector immune response and abrogating PD-1 pathway on Treg cells significantly rescued protective T cell response, suggesting its importance in immune restoration among tuberculosis patients.

Distinguishing Latent from Active Mycobacterium tuberculosis Infection Using Elispot Assays: Looking Beyond Interferon-gamma

Mycobacterium tuberculosis (MTB) is a global heath epidemic, its threat amplified by HIV infection and the emergence of multidrug-resistant tuberculosis (MDR-TB). Interferon (IFN)-gamma release assays (IGRAs) have improved the accuracy of detection of MTB exposure in some subject groups as compared to the Tuberculin Skin Test (TST). However, as IFN-gamma is produced by both fully rested and more recently activated populations of memory T cells, it is not surprising that the measurement of this cytokine alone cannot accurately distinguish Latent TB Infected (LTBI) subjects from those with active (infectious) disease. Accurate and rapid diagnosis of infectious individuals would allow medication to be properly allocated and other actions taken to more effectively curtail MTB spread. Analysis of multi-cytokine profiles ex vivo after stimulation of PBMCs from LTBI and active MTB subjects indicate the real possibility of successfully discerning these two disease states within 24 hours of a subject’s blood draw. Due to the unparalleled sensitivity, low cost, and ease of use of Elispot assays, we propose that via a multiplex Elispot platform the accurate distinction of LTBI from active MTB-infected individuals is within reach.

Tuberculosis and HIV co-infection

Tuberculosis (TB) and HIV co-infections place an immense burden on health care systems and pose particular diagnostic and therapeutic challenges. Infection with HIV is the most powerful known risk factor predisposing for Mycobacterium tuberculosis infection and progression to active disease, which increases the risk of latent TB reactivation 20-fold. TB is also the most common cause of AIDS-related death. Thus, M. tuberculosis and HIV act in synergy, accelerating the decline of immunological functions and leading to subsequent death if untreated. The mechanisms behind the breakdown of the immune defense of the co-infected individual are not well known. The aim of this review is to highlight immunological events that may accelerate the development of one of the two diseases in the presence of the co-infecting organism. We also review possible animal models for studies of the interaction of the two pathogens, and describe gaps in knowledge and needs for future studies to develop preventive measures against the two diseases.

The pathology of Mycobacterium tuberculosis infection

Mycobacterium tuberculosis is an old enemy of the human race, with evidence of infection observed as early as 5000 years ago. Although more host-restricted than Mycobacterium bovis, which can infect all warm-blooded vertebrates, M. tuberculosis can infect, and cause morbidity and mortality in, several veterinary species as well. As M. tuberculosis is one of the earliest described bacterial pathogens, the literature describing this organism is vast and overwhelming. This review strives to distill what is currently known about this bacterium and the disease it causes for the veterinary pathologist.

Glutathione and adaptive immune responses against Mycobacterium tuberculosis infection in healthy and HIV infected individuals

Glutathione (GSH), a tripeptide antioxidant, is essential for cellular homeostasis and plays a vital role in diverse cellular functions. Individuals who are infected with Human immuno deficiency virus (HIV) are known to be susceptible to Mycobacterium tuberculosis (M. tb) infection. We report that by enhancing GSH levels, T-cells are able to inhibit the growth of M. tb inside macrophages. In addition, those GSH-replenished T cell cultures produced increased levels of Interleukin-2 (IL-2), Interleukin-12 (IL-12), and Interferon-gamma (IFN-γ), cytokines, which are known to be crucial for the control of intracellular pathogens. Our study reveals that T lymphocytes that are derived from HIV infected individuals are deficient in GSH, and that this deficiency correlates with decreased levels of Th1 cytokines and enhanced growth of M. tb inside human macrophages.

Immunological basis for the introduction of immunotherapy with Mycobacterium vaccae into the routine treatment of TB

An account is given of the immunological investigations carried out in Rosario (Argentina) to identify suitable methods for the assessment of the efficacy of immunotherapy for TB. Some of these were then applied to three small studies: one of a single injected dose of heat-killed, borate-buffered Mycobacterium vaccae administered early in treatment, another of three such doses administered at monthly intervals from the start of treatment, and the third of ten oral doses at frequent intervals throughout short-course chemotherapy. All three displayed better clearance of bacilli from the sputum, faster improvement in clinical symptoms, better radiological resolution of lesions and a return of most immunological parameters towards those of healthy persons. In principle, the immune change achieved is an increase in Th1 mechanisms, notably IL-2 and -12 with downregulation of the tissue damaging aspects of Th2. As an addition to chemotherapy for drug-susceptible or drug-resistant TB, with or without concomitant HIV infection, this immunotherapy offers a safe and effective improvement.

CD4(+) regulatory T cells in a cynomolgus macaque model of Mycobacterium tuberculosis infection

BACKGROUND

Mycobacterium tuberculosis infection in humans results in either latent infection or active tuberculosis. We sought to determine whether a higher frequency of regulatory T (T(reg)) cells predispose an individual toward active disease or whether T(reg) cells develop in response to active disease.

METHODS

In cynomolgus macaques infected with a low dose of M. tuberculosis, approximately 50% develop primary tuberculosis, and approximately 50% become latently infected. Forty-one animals were monitored for 6-8 months to assess the correlation of the frequency of Foxp3(+) cells in peripheral blood and airways with the outcome of infection.

RESULTS

In all animals, the frequency of T(reg) cells (CD4(+)Foxp3(+)) in peripheral blood rapidly decreased and simultaneously increased in the airways. Latently infected monkeys had a significantly higher frequency of T(reg) cells in peripheral blood before infection and during early infection, compared with monkeys that developed active disease. Monkeys with active disease experienced increased frequencies of T(reg) cells among peripheral blood mononuclear cells as they developed disease.

CONCLUSIONS

Our data suggest that increased frequencies of T(reg) cells in active disease occur in response to increased inflammation rather than act as a causative factor in progression to active disease.

Immunoregulation in TB: observations and implications

Regulation of the immune response during active tuberculosis (TB) has been partly deciphered. In pulmonary TB there is transient systemic immunosuppression due to overexpression of transforming growth factor beta and interleukin-10. This is superimposed on a primary T-cell defect. Locally there is intense inflammation (lung, pleural fluid) with overexpression of immunosuppressive factors (bronchoalveolar lavage) and extensive apoptosis. These observations suggest that immune therapies should be aimed at neutralizing the negative regulatory factors rather than accentuating an already intense immune response. Also a partially effective vaccine carries the potential risk of exacerbating disease.

Regulatory T cell frequency and modulation of IFN-gamma and IL-17 in active and latent tuberculosis

Regulatory T cells (Tregs) play an essential role in immune homeostasis. In infectious diseases Tregs may inhibit protective responses facilitating pathogen multiplication and dissemination, but they may also limit the inflammatory response diminishing tissue damage. Although there is experimental and clinical evidence that Tregs are induced during Mycobacterium tuberculosis infection, their role in the immunopathogenesis of tuberculosis is still not completely understood. In this study, the phenotype, frequency and activity of circulating Tregs in active and latent tuberculosis were evaluated. Phenotypic analysis showed that Tregs were CD4(+)CD25(high)FOXP3(+)CD45RO(+)CD127(-). High levels of circulating Tregs were found in patients with active pulmonary tuberculosis, compared to individuals with latent infection. Treg activity was evaluated by ELISPOT by determining the effect of CD25(+) cell depletion on the frequency of IFN-gamma and IL-17 producing cells after in vitro stimulation with ESAT-6, CFP-10 and PPD. Treg depletion increased the frequency of IFN-gamma producing cells, without affecting the frequency of IL-17 producing cells, in both active and latent tuberculosis, irrespective of the antigen used. Neutralization of IL-10 did not have any effect on the frequency of IFN-gamma and IL-17 producing cells. Altogether, these results suggest that during active tuberculosis Tregs inhibit protective Th1 responses, but not the proinflammatory Th17 responses, facilitating mycobacterial replication and tissue damage.

Natural killer cell-mediated cytokine response among HIV-positive south Indians with pulmonary tuberculosis

Natural killer (NK) cells control Mycobacterium tuberculosis infection mainly through secreted cytokines. Cytokine dysregulation among HIV may cause rapid disease progression. Our objective was to examine whether impaired production of innate cytokines are responsible for cytokine dysregulation during HIV infection. The study included 30 subjects each of normal healthy subjects (NHS), pulmonary tuberculosis patients (TB), HIV-infected individuals (HIV), and HIV-TB co-infected patients (HIV-TB). Intracellular cytokine staining method was used to enumerate the cytokine-positive NK cells. Unlike NHS (100%), only 27% of HIV-TB and 57% of HIV infected patients have detectable plasma interleukin (IL)-15 levels that signify impaired rather than decreased IL-15 production. Basal type 1 cytokine (IL-2, interferon-gamma [IFN-gamma], and tumor necrosis factor-alpha [TNF-alpha])-secreting NK cells (NK1 cytokines) were decreased significantly (P < 0.05) in TB, HIV, and HIV-TB, when compared with NHS. Stimulation with M. tuberculosis H37Rv enhanced the NK1 cytokines in NHS (P < 0.05), but not in other groups. With IL-15+IL-12 stimulation, we found increased NK1 cytokines (IL-2 and IFN-gamma) in HIV (P < 0.05), but not in HIV-TB, when compared to unstimulated condition. Supplementing IL-15+IL-12 has potential in improving the frequency of NK1 cytokines for HIV, but not HIV-TB, suggesting that TB influences cytokine response during HIV infection.

The immunology of tuberculosis: from bench to bedside

Tuberculosis (TB) is an international public health priority and kills almost two million people annually. TB is out of control in Africa due to increasing poverty and HIV coinfection, and drug-resistant TB threatens to destabilize TB control efforts in several regions of the world. Existing diagnostic tools and therapeutic interventions for TB are suboptimal. Thus, new vaccines, immunotherapeutic interventions and diagnostic tools are urgently required to facilitate TB control efforts. An improved understanding of the immunopathogenesis of TB can facilitate the identification of correlates of immune protection, the design of effective vaccines, the rational selection of immunotherapeutic agents, the evaluation of new drug candidates, and drive the development of new immunodiagnostic tools. Here we review the immunology of TB with a focus on aspects that are clinically and therapeutically relevant. An immunologically orientated approach to tackling TB can only succeed with concurrent efforts to alleviate poverty and reduce the global burden of HIV.

Mycolic acids constitute a scaffold for mycobacterial lipid antigens stimulating CD1-restricted T cells

CD1-restricted lipid-specific T lymphocytes are primed during infection with Mycobacterium tuberculosis, the causative agent of tuberculosis. Here we describe the antigenicity of glycerol monomycolate (GroMM), which stimulates CD1b-restricted CD4(+) T cell clones. Chemical characterization of this antigen showed that it exists as two stereoisomers, one synthetic isomer being more stimulatory than the other. The hydroxyl groups of glycerol and the mycolic acid length are critical for triggering the T cell responses. GroMM was presented by M. tuberculosis-infected dendritic cells, demonstrating that the antigen is available for presentation during natural infection. Ex vivo experiments showed that GroMM stimulated T cells from vaccinated or latently infected healthy donors but not cells from patients with active tuberculosis, suggesting that GroMM-specific T cells are primed during infection and their detection correlates with lack of clinical active disease.

Augumentation of natural killer activity with exogenous interleukins in patients with HIV and pulmonary tuberculosis coinfection

A depressed level of natural killer (NK) activity is one of the various immunological abnormalities in HIV infection. Defective NK cell functions can be partially restored in vitro by interleukin (IL)-2 and IL-12. IL-15 shares receptor and several biological properties with IL-2. The effect of IL-15 on NK cells in patients with HIV and tuberculosis coinfection (HIV-TB) is unclear. This study examined the cytotoxic activity and cytokine response of NK cells in HIV-TB after stimulation with IL-15 and IL-12/IL-2. The study includes 16 normal healthy subjects (NHS), 15 patients with pulmonary tuberculosis (TB), 15 HIV-infected subjects (HIV), and 15 HIV-TB patients. The cytotoxic activity of NK cells was assessed by dioctadecyloxacarbocyanine dye-based flow cytometry. Interferon-gamma present in the culture supernatants was measured by enzyme-linked immunosorbent assay. Basal NK cytotoxicity was found to be lower in HIV-TB (p < 0.05) and HIV when compared to NHS or TB. Maximal NK cytotoxicity (p < 0.05) was observed with an IL-15 and IL-12 combination in all the groups. At a 50:1 effector/target ratio, the mean fold increase in NK cytotoxicity upon stimulation was 2.11 for HIV and 1.84 for HIV-TB. Interferon-gamma levels from the stimulated cultures were elevated (p < 0.05) in the HIV and HIV-TB groups. We found no correlation between NK cytotoxicity and CD4 counts in HIV-TB. There is a positive correlation between NK cytotoxicity and interferon-gamma secretion for HIV-TB. The combination of IL-15 and IL-12 may have potential to improve the NK activity of HIV and HIV-TB.

Recombinant Mycobacterium bovis BCG vector system expressing SIV Gag protein stably and persistently induces antigen-specific humoral immune response concomitant with IFN gamma response, even at three years after immunization

A vaccine against HIV-1 infection absolutely needs the ability to effectively elicit virus-specific immunity over a long term; nevertheless, there have been few studies indicating that the immunoinductivity of such a candidate vaccine has been researched for several years running. In a previous report, we demonstrated that recombinant BCG (rBCG) expressing the full-length gag gene of simian immunodeficiency virus (SIV) (rBCG-SIVgag) induced Gag-specific delayed-type hypersensitivity, T cell proliferation, gamma interferon (IFN gamma), and serum IgG responses in guinea pigs immunized intradermally (i.d.) with 0.1 mg for the 1-year period of study. Especially, the production of long-lasting Gag-specific serum IgG in the vaccinated animals perhaps reflects the persistent antigenic stimulation by rBCG-SIVgag. How long, we questioned, will such immune responses to Gag engendered by the rBCG-SIVgag vaccination persist without booster immunizations? To learn this, we examined Gag-specific IgG production in sera and Gag-specific IFN gamma mRNA expression in peripheral blood mononuclear cells (PBMC) in guinea pigs vaccinated with rBCG-SIVgag i.d. (0.1 mg) or orally (80 mg x 2) during a 3-year period. As a result, Gag-specific serum IgG was highly generated for 3 years at similar levels between the i.d. and the orally immunized guinea pigs (IgG2>IgG1). The enhancement of IFN gamma mRNA expression by in vitro restimulation with Gag antigen was also detected in PBMC from the two immunization groups throughout the 3-year observation period. In guinea pigs immunized i.d. with rBCG-SIVgag, a high level of Gag-specific IFN gamma response was observed at 1 year after vaccination, whereas the response has waned gradually. The current study indicates that i.d. and oral inoculations of rBCG-SIVgag elicit stable, strong, Gag-specific serum IgG production while exhibiting the different kinetics of Gag-specific IFN gamma responses between i.d. and oral vaccination routes. This suggests that the rBCG vector system expressing an appropriate size of foreign antigen gene should be suited for the induction of the antigen-specific humoral immunity concomitant with an IFN gamma response.

Compartmentalized bronchoalveolar IFN-gamma and IL-12 response in human pulmonary tuberculosis

Human tuberculosis (TB) principally involves the lungs, where local immunity impacts on the load of Mycobacterium tuberculosis (M.tb). Because concomitants of local Th1 immunity are still under-explored in humans, we characterized immune responses in bronchoalveolar cells (BACs) and systemically in peripheral blood mononuclear cells (PBMCs) in persons with active pulmonary TB and in healthy community controls. PPD- and live M.tb-induced IFN-gamma-production were observed in CD4(+), CD8(+), gammadeltaTCR(+), and CD56(+) alveolar T cell subpopulations and NK cells (CD3(-)CD56(+)). IFN-gamma-producing CD4(+) T cells (mostly CD45RO(+)) were more abundant (p<0.05). M.tb-induced IL-12p70, but interestingly also IL-4, was increased (p<0.05) in BACs from TB patients. Constitutive expression of IL-12Rbeta1 and IL-12Rbeta2 mRNA in BACs and PBMCs and IFN-gammaR1 in BACs was similar in both study groups. Data were normalized to account for differences in proportions of alveolar T cells and macrophages in the study groups. IFN-gamma-production and its induction by IL-12R engagement occur virtually unimpaired in the bronchoalveolar spaces of patients with pulmonary TB. The reasons for the apparent failure to control M. tuberculosis growth during active pulmonary TB disease is unknown but could be the expression of locally acting immunosuppressive mechanisms that subvert the antimycobacterial effects of IFN-gamma.

Boosting BCG vaccination with MVA85A down-regulates the immunoregulatory cytokine TGF-beta1

In clinical trials recombinant-modified vaccinia virus Ankara expressing the Mycobacterium tuberculosis antigen 85A (MVA85A) induces approximately 10 times more effector T cells than any other recombinant MVA vaccine. We have found that in BCG primed subjects MVA85A vaccination reduces transforming growth factor beta 1 (TGF-beta1) mRNA in peripheral blood lymphocytes and reduces TGF-beta1 protein in the serum, but increases IFN-gamma ELISPOT responses to the recall antigen SK/SD. TGF-beta1 is essential for the generation of regulatory T cells and we see a correlation across vaccinees between CD4+CD25hiFoxP3+ cells and TGF-beta1 serum levels. This apparent ability to counteract regulatory T cell effects suggests a potential use of MVA85A as an adjuvant for less immunogenic vaccines.

Distinct, specific IL-17- and IL-22-producing CD4+ T cell subsets contribute to the human anti-mycobacterial immune response

We investigated whether the proinflammatory T cell cytokines IL-17 and IL-22 are induced by human mycobacterial infection. Remarkably, >20% of specific cytokine-producing CD4(+) T cells in peripheral blood of healthy, mycobacteria-exposed adults expressed IL-17 or IL-22. Specific IL-17- and IL-22-producing CD4(+) T cells were distinct from each other and from Th1 cytokine-producing cells. These cells had phenotypic characteristics of long-lived central memory cells. In patients with tuberculosis disease, peripheral blood frequencies of these cells were reduced, whereas bronchoalveolar lavage fluid contained higher levels of IL-22 protein compared with healthy controls. IL-17 was not detected in this fluid, which may be due to suppression by Th1 cytokines, as PBMC IL-17 production was inhibited by IFN-gamma in vitro. However, Th1 cytokines had no effect on IL-22 production in vitro. Our results imply that the magnitude and complexity of the anti-mycobacterial immune response have historically been underestimated. IL-17- and IL-22-producing CD4(+) T cells may play important roles in the human immune response to mycobacteria.

1, 25 Dihydroxyvitamin D3 modulated cytokine response in pulmonary tuberculosis

1, 25 Dihydroxyvitamin D(3) (1, 25(OH)(2) D(3)) has gained significant importance in tuberculosis with regard to its immunoregulatory activities. Our aim was to evaluate the effect of 1, 25(OH)(2) D(3) on cytokine response to Mycobacterium tuberculosis antigens in pulmonary tuberculosis. Peripheral blood mononuclear cells obtained from 60 healthy controls and 52 pulmonary tuberculosis patients were cultured with culture filtrate antigen (CFA) of M. tuberculosis and live M. tuberculosis with and without 1, 25(OH)(2) D(3) (10(-9), 10(-8)and 10(-7)M concentrations). The culture supernatants were used to estimate IL-8, IL-6, TGF-beta, IL-10, IFN-gamma, IL-12p40, IL-2, IL-4 and IL-5 levels by ELISA. 1, 25 Dihydroxyvitamin D(3) significantly suppressed IL-12p40 and IFN-gamma production in response to CFA and live M. tuberculosis with a maximum suppression at 10(-7)M concentration (p<0.0001). In CFA stimulated cultures, addition of 1, 25(OH)(2) D(3) significantly suppressed IL-8, IL-6 and IL-10 whereas the IL-2 levels were significantly increased in controls. It variably influenced the Th2 cytokines, showing an increased trend for IL-4 and suppressed IL-5 levels. We report that 1, 25(OH)(2) D(3) differentially modulates production of cytokines in response to M. tuberculosis antigens by predominantly suppressing IL-12p40 and IFN-gamma production in a dose dependent manner. Our results suggest a role for vitamin D in restricting acquired immune response against tuberculosis by regulating cytokine production.

Low expression of antigen-presenting and costimulatory molecules by lung cells from tuberculosis patients

Costimulatory and antigen-presenting molecules are essential to the initiation of T cell immunity to mycobacteria. The present study analyzed by immunocytochemistry, using monoclonal antibodies and alkaline phosphatase-anti-alkaline phosphatase method, the frequency of costimulatory (CD86, CD40, CD40L, CD28, and CD152) and antigen-presenting (MHC class II and CD1) molecules expression on human lung cells recovered by sputum induction from tuberculosis (TB) patients (N = 22) and non-TB controls (N = 17). TB cases showed a statistically significant lower percentage of HLA-DR+ cells than control subjects (21.9 +/- 4.2 vs 50.0 +/- 7.2%, P < 0.001), even though similar proportions of TB cases (18/22) and control subjects (16/17, P = 0.36) had HLA-DR-positive-stained cells. In addition, fewer TB cases (10/22) compared to control subjects (16/17) possessed CD86-expressing cells (P = 0.04; OR: 0.05; 95%CI = 0.00-0.51), and TB cases expressed a lower percentage of CD86+ cells (P = 0.04). Moreover, TB patients with clinically limited disease ( pound1 lobe) on chest X-ray exhibited a lower percentage of CD86-bearing cells compared to patients with more extensive lung disease (>1 lobe) (P = 0.02). The lower expression by lung cells from TB patients of HLA-DR and CD86, molecules involved in antigen presentation and activation of T cells, may minimize T cell recognition of Mycobacterium tuberculosis, fostering an immune dysfunctional state and active TB.

Genetic polymorphisms and plasma levels of transforming growth factor-beta(1) in Chinese patients with tuberculosis in Hong Kong

Susceptibility to tuberculosis (TB) may be affected by host genetic factors. Elevated levels of transforming growth factor-beta 1 (TGF-beta(1)) were found in plasma of patients with active TB compared with those of healthy contacts. To investigate the association of TGF-beta(1) gene polymorphisms (C-509T and T869C) and plasma levels with the risk of TB in Hong Kong Chinese adults, a case-control study was carried out on 174 active TB patients and 174 healthy controls matched for age, gender and smoking. Blood samples from 180 blood donors served as another control group. Genotyping was carried out on genomic DNA using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). Plasma TGF-beta(1) was measured by commercially available ELISA kit. We found no differences in the distribution of genotypes or alleles of TGF-beta(1) gene polymorphisms at C-509T and T869C between patients and either group of healthy controls. Patients with TB had elevated plasma TGF-beta(1) levels compared with healthy controls irrespective of their genotypes (p<0.001). In conclusion, TGF-beta(1) gene polymorphism at C-509T and T869C is not associated with TB susceptibility in Hong Kong Chinese adults, but elevated plasma TGF-beta(1) levels suggests that this cytokine may play a role in the pathogenesis of tuberculosis.

In vitro expansion of CD4+CD25highFOXP3+CD127low/− regulatory T cells from peripheral blood lymphocytes of healthy Mycobacterium tuberculosis-infected humans

CD4+CD25highFOXP3+ regulatory T (Treg) cells have recently been found at elevated levels in the peripheral blood of tuberculosis patients, compared to Mycobacterium tuberculosis latently infected (LTBI) healthy individuals and non-infected controls. Here, we show that CD4+CD25highFOXP3+ T lymphocytes can be expanded in vitro from peripheral blood mononuclear cells (PBMC) of LTBI individuals, but not of uninfected controls by incubating them with BCG in the presence of TGF-beta. These expanded cells from the PBMC of LTBI subjects expressed CTLA-4, GITR and OX-40, but were CD127low/- and have therefore the phenotype of Treg cells. In addition, they inhibited in a dose-dependant manner the proliferation of freshly isolated mononuclear cells in response to polyclonal stimulation, indicating that they are functional Treg lymphocytes. In contrast, incubation of the PBMC with BCG alone preferentially induced activated CD4+ T cells, expressing CD25 and/or CD69 and secreting IFN-gamma. These results show that CD4+CD25highFOXP3+ Treg cells can be expanded or induced in the peripheral blood of LTBI individuals in conditions known to predispose to progression towards active tuberculosis and may therefore play an important role in the pathogenesis of the disease.

Mechanisms of apoptosis of T-cells in human tuberculosis

The role of TGF-beta TNF-alpha FasL and Bcl-2 in apoptosis of CD4 T-cells during active TB was studied. Coculture of PBMC from TB patients with neutralizing antibodies to TGF-beta or TNF-alpha decreased spontaneous (P < or = 0.05) and MTB-induced (P < or = 0.02) T-cell apoptosis by 50-90%, but effects were not additive. Interestingly, only levels of TGF-beta in supernatants correlated with rates of spontaneous and MTB-induced apoptosis. FasL surface and mRNA expression were higher in unstimulated and MTB-stimulated PBMC from patients than controls, and neutralization of FasL abrogated apoptosis of T-cells from patients only. Intracellular Bcl-2 protein was lower among unstimulated CD4 T-cells from patients than those from controls (P < or = 0.02), and MTB stimulation reduced intracellular Bcl-2 content in CD4 T-cells from patients only (P < or = 0.001). These findings may indicate that, during TB, predisposition of CD4 T-cells to apoptosis may involve both low expression of Bcl-2, and excessive expression of TGF-beta TNF-alpha and FasL.

Reactivation of latent tuberculosis by TNF blockade: the role of interferon gamma

Tumor necrosis factor (TNF) plays a pathogenic role in psoriasis and rheumatoid arthritis but is essential for host defenses against mycobacteria and other granulomatous pathogens. The risk of reactivation of latent Mycobacterium tuberculosis infection is significantly greater with the TNF monoclonal antibody infliximab than with the soluble TNF-receptor etanercept. We have examined the biologic basis of this difference using whole blood culture. Infliximab and adalimumab reduced the proportion of T buciclate-responsive cells by 70 and 50%, respectively, and suppressed antigen-induced IFN-gamma production by 70 and 64%. In contrast, etanercept produced no significant effect. The difference between infliximab and etanercept remained whether one compared equal or peak therapeutic drug concentrations, suggesting a relationship to mechanism of action rather than pharmacokinetics. Adalimumab and etanercept caused divergent, concentration dependent effects on control of intracellular growth of M. tuberculosis. None of the drugs induced significant levels of apoptosis or necrosis in monocytes or T cells, excluding T-cell death as a mechanism for suppression of antigen-induced responses. IL-10 production was equally suppressed by all three drugs, excluding excess IL-10 as a regulatory mechanism. The tuberculosis risk posed by infliximab may reflect its combined effects on TNF and IFNgamma.