FoxP3+Regulatory T Cells Suppress Effector T-Cell Function at Pathologic Site in Miliary Tuberculosis

Current status of interleukin-10 and regulatory T-cells in cancer

PURPOSE OF REVIEW

Tumor growth elicits antigen-specific cytotoxic as well as immune suppressive responses. Interleukin-10 (IL-10) is a key immune-suppressive cytokine produced by regulatory T-cells and by helper T-cells. Here, we review pleiotropic functions of IL-10 that impact the immune pathology of cancer.

RECENT FINDINGS

The role of IL-10 in cancer has become less certain with the knowledge of its immune stimulatory functions. IL-10 is needed for T-helper cell functions, T-cell immune surveillance, and suppression of cancer-associated inflammation. By promoting tumor-specific immune surveillance and hindering pathogenic inflammation, IL-10 is emerging as a key cytokine in the battle of the host against cancer.

SUMMARY

IL-10 functions at the cross-roads of immune stimulation and immune suppression in cancer. Immunological mechanisms of action of IL-10 can be ultimately exploited to develop novel and effective cancer therapies.

CD4(+) CD25(high) forkhead box protein 3(+) regulatory T lymphocytes suppress interferon-γ and CD107 expression in CD4(+) and CD8(+) T cells from tuberculous pleural effusions

Tuberculous pleural effusion is characterized by a T helper type 1 (Th1) profile, but an excessive Th1 response may also cause tissue damage that might be controlled by regulatory mechanisms. In the current study we investigated the role of regulatory T cells (Treg ) in the modulation of Th1 responses in patients with tuberculous (TB) pleurisy. Using flow cytometry we evaluated the proportion of Treg (CD4(+) CD25(high) forkhead box protein 3(+) ), interferon (IFN)-γ and interleukin (IL)-10 expression and CD107 degranulation in peripheral blood (PB) and pleural fluid (PF) from patients with TB pleurisy. We demonstrated that the proportion of CD4(+) CD25(+) , CD4(+) CD25(high) FoxP3(+) and CD8(+) CD25(+) cells were increased in PF compared to PB samples. Mycobacterium tuberculosis stimulation increased the proportion of CD4(+) CD25(low/neg) IL-10(+) in PB and CD4(+) CD25(low/neg) IFN-γ(+) in PF; meanwhile, CD25(high) mainly expressed IL-10 in both compartments. A high proportion of CD4(+) CD107(+) and CD8(+) CD107(+) cells was observed in PF. Treg depletion enhanced the in-vitro M. tuberculosis-induced IFN-γ and CD4(+) and CD8(+) degranulation responses and decreased CD4(+) IL-10(+) cells in PF. Our results demonstrated that in TB pleurisy Treg cells effectively inhibit not only IFN-γ expression but also the ability of CD4(+) and CD8(+) cells to degranulate in response to M. tuberculosis.

Clinical relevance of ground glass opacity in 105 patients with miliary tuberculosis

BACKGROUND

After the application of chest computed tomography (CT), ground glass opacity (GGO) was introduced as one of major accompanying findings of miliary tuberculosis (MT) in addition to miliary nodules. However, little is known about whether GGO is associated with the clinical manifestations and outcomes of MT. Therefore, the present study examined the clinical relevance of GGO in patients with MT.

METHODS

Chest radiographs and CT scans of MT patients were retrospectively reviewed. Clinical manifestations and outcomes were compared in terms of the extent of GGO revealed by chest CT.

RESULTS

Confirmed 105 MT patients were included. GGO was observed in 70 (67%) patients. MT patients with an extent of GGO >50% (n = 21) had symptoms of shorter duration, more frequent dyspnea, and more pronounced changes in the levels of acute phase reactants. Miliary nodules were less discernible on CT in those with an extent of GGO >50%. MT patients with an extent of GGO >50% were significantly associated with a longer hospital stay (p = 0.02) and with acute respiratory failure (p < 0.001) than those with an extent of GGO ≤ 50%. However, mortality among MT patients was not associated with the extent of GGO.

CONCLUSION

MT patients with an extent of GGO >50% had more rapidly progressive manifestations and a greater potential for delayed diagnosis and poorer prognosis. Nevertheless, mortality was not higher in confirmed MT patients with an extent of GGO >50% than in those with an extent of GGO ≤ 50%.

How to avoid the impact of environmental mycobacteria towards the efficacy of BCG vaccination against tuberculosis?

Bacillus Calmette-Guérin (BCG) remains the only widely used vaccine against tuberculosis (TB). Consistent efficacy has been proved in infants but not in adults from developing countries. Epidemiological and experimental studies have pointed out that, prior exposure to prevailing environmental mycobacteria could be responsible for the poor efficacy of BCG as an anti-TB vaccine in adults living in developing countries. Sensitization by environmental mycobacteria may down-modulate the immunologic behavior of BCG on the one hand and may mask its efficacy on the other hand. Some of the important deciding factors for poor efficacy of BCG, due to exposure of the subjects to prevailing environmental mycobacteria, are thought to be (i) Life stage: neonatus versus adolescence; (ii) shared antigens between prevailing environmental mycobacteria and BCG; and (iii) generation of cross-reactive T-regulatory cells against environmental mycobacteria and BCG. In this communication, some novel strategies have been discussed for countering the down modulating impact of environmental mycobacteria towards performance of BCG as an anti-TB vaccine.

Increase in TGF-β secreting CD4⁺CD25⁺ FOXP3⁺ T regulatory cells in anergic lepromatous leprosy patients

BACKGROUND

Lepromatous leprosy caused by Mycobacterium leprae is associated with antigen specific T cell unresponsiveness/anergy whose underlying mechanisms are not fully defined. We investigated the role of CD25(+)FOXP3(+) regulatory T cells in both skin lesions and M.leprae stimulated PBMC cultures of 28 each of freshly diagnosed patients with borderline tuberculoid (BT) and lepromatous leprosy (LL) as well as 7 healthy household contacts of leprosy patients and 4 normal skin samples.

METHODOLOGY/PRINCIPLE FINDINGS

Quantitative reverse transcribed PCR (qPCR), immuno-histochemistry/flowcytometry and ELISA were used respectively for gene expression, phenotype characterization and cytokine levels in PBMC culture supernatants. Both skin lesions as well as in vitro antigen stimulated PBMC showed increased percentage/mean fluorescence intensity of cells and higher gene expression for FOXP3(+), TGF-β in lepromatous (p<0.01) as compared to tuberculoid leprosy patients. CD4(+)CD25(+)FOXP3(+) T cells (Tregs) were increased in unstimulated basal cultures (p<0.0003) and showed further increase in in vitro antigen but not mitogen (phytohemaglutinin) stimulated PBMC (iTreg) in lepromatous as compared to tuberculoid leprosy patients (p<0.002). iTregs of lepromatous patients showed intracellular TGF-β which was further confirmed by increase in TGF-β in culture supernatants (p<0.003). Furthermore, TGF-β in iTreg cells was associated with phosphorylation of STAT5A. TGF-β was seen in CD25(+) cells of the CD4(+) but not that of CD8(+) T cell lineage in leprosy patients. iTregs did not show intracellular IFN-γ or IL-17 in lepromatous leprosy patients.

CONCLUSIONS/SIGNIFICANCE

Our results indicate that FOXP3(+) iTregs with TGF-β may down regulate T cell responses leading to the antigen specific anergy associated with lepromatous leprosy.

An increased alveolar CD4 + CD25 + Foxp3 + T-regulatory cell ratio in acute respiratory distress syndrome is associated with increased 30-day mortality

Purpose

Cell therapy may become an option for lung injury treatment. However, no data are available on the alveolar presence and time course of CD4+ CD25 + Foxp3 + T-regulatory lymphocyte cells (Tregs) in acute respiratory distress syndrome (ARDS). Accordingly, we (1) measured the ratio of CD4 + CD25 + Foxp3 + Tregs to all (CD4+) lymphocytes in the bronchoalveolar lavage (BAL) of ARDS patients and of control subjects without lung disease and (2) assessed their impact on 30-day mortality.

Methods

In a prospective study, the ratios of CD4 + CD25 + Foxp3 + T-regulatory cells to all CD4+ cells were measured (FACS) within 24 h of the patients’ ICU referral in the BAL and in the blood of 47 patients with ARDS (32 males, 15 females; mean age 44 years ±13) as well as in 8 controls undergoing elective abdominal surgery (5 men, 3 women; mean age 49 years ±4). BAL concentrations of several cytokines were also measured in ARDS patients.

Results

Tregs were detected in the BAL of control subjects and ARDS patients. However, the mean ratio of Tregs to all CD4+ lymphocytes was threefold greater in ARDS non-survivors (16.5 %; p = 0.025) and almost twofold greater in ARDS survivors (9.0 %; p = 0.015) compared to controls (5.9 %). Multivariate Cox regression analysis revealed the ratio of CD4 + CD25 + Foxp3 + T-regulatory lymphocytes to all CD4+ lymphocytes in the BAL to be an important and independent prognostic factor for 30-day survival (HR 6.5; 95 % CI, 1.7–25; p = 0.006).

Conclusion

An increased T-regulatory cell ratio in the admission BAL of patients with ARDS is an important and independent risk factor for 30-day mortality.

Regulatory T cells attenuate mycobacterial stasis in alveolar and blood-derived macrophages from patients with tuberculosis

RATIONALE

There are hardly any data about the frequency of CD4(+)CD25(+)Foxp3(+) regulatory T cells (T-Regs) in the lungs of patients with active tuberculosis (TB).

OBJECTIVES

To obtain data about the frequency of CD4(+)CD25(+)Foxp3(+) T-Regs, and their impact on mycobacterial containment, in the lungs of patients with active TB.

METHODS

Patients with pulmonary TB (n = 49) and healthy volunteers with presumed latent TB infection (LTBI; n = 38) donated blood and/or bronchoalveolar lavage (BAL) cells obtained by bronchoscopy. T-cell phenotype (Th1/Th2/Th17/T-Reg) and functional status was evaluated using flow-cytometry and (3)H-thymidine proliferation assays, respectively. H37Rv-infected alveolar and monocyte-derived macrophages were cocultured with autologous T-Regs and purified protein derivative (PPD) preprimed T-Reg-depleted effector cells. Mycobacterial containment was evaluated by counting CFUs.

MEASUREMENTS AND MAIN RESULTS

In blood and BAL T-Reg levels were higher in TB versus LTBI (P < 0.04), and in TB the frequency of T-Regs was significantly higher in BAL versus blood (P < 0.001). T-Reg-mediated suppression of T-cell proliferation in blood and BAL was concentration-dependent. Restriction of mycobacterial growth in infected alveolar and monocyte-derived macrophages was significantly diminished, and by up to 50%, when T-Regs were cocultured with PPD-primed CD4(+) effector T cells. The levels of CD8(+) T-Regs (CD8(+)CD25(+)Foxp3(+)), IL-17-producing T-Regs (IL-17(+)CD4(+)CD25(+)Foxp3(+)), and IL-17-producing T cells were similar in BAL-TB versus BAL-LTBI. Within the TB group compartmentalization of responses was prominent (T-Reg, IFN-γ, tumor necrosis factor-α, IL-17, and IL-22 significantly higher in BAL vs. blood).

CONCLUSIONS

In patients with TB the alveolar compartment is enriched for CD4(+) T-Regs. Peripheral blood-derived T-Regs decrease the ability of alveolar and monocyte-derived macrophages to restrict the growth of Mycobacterium tuberculosis in the presence of effector cells. Collectively, these data suggest that CD4(+)CD25(+)FoxP3(+) T-Regs subvert antimycobacterial immunity in human TB.

Foxp3(+) regulatory T cells in tuberculosis

The immune response to Mycobacterium tuberculosis (Mtb) must be tightly regulated to mount a sufficient response to limit bacterial growth and dissemination while avoiding excessive inflammation that could damage host tissues. A wide variety of cell types, cell surface molecules, and cytokines are likely to contribute to this regulation, but recent studies have revealed that a subset of CD4 T cells expressing the transcription factor Foxp3, called regulatory T (reg) cells, play a critical role [1-3]. Although the first reports of T reg cells in tuberculosis (TB) occurred only recently (i.e., 2006) [4, 5], we have already gained many insights into their activity during TB. While it is likely that T reg cells do play some beneficial roles by preventing inflammation-mediated damage to host tissues during TB, this aspect of their function has not been well studied to date. What is clear, however, is that during the initial T cell response to Mtb infection, Mtb induces the expansions of T reg cells that delay the onset of adaptive immunity, suggesting that Mtb has hijacked T reg cell-mediated immune suppression to allow it to replicate unabated in the lung until T cells finally arrive [6]. In this chapter, we will first provide an overview of the delayed T cell response to Mtb and a brief introduction to regulatory T cells. We will then review what is known about T reg cells from observations in human populations, discuss mechanistic insights revealed in the mouse model, and speculate about the relevance of this understanding for future efforts to prevent and treat TB.

CD4(+)FoxP3(+) T regulatory cells in drug-susceptible and multidrug-resistant tuberculosis

Regulatory T cells (Treg) increase in active tuberculosis (TB). However, whether Treg-mediated immune suppression affect the susceptibility to active TB or development of multidrug-resistant (MDR) TB is not yet clear. We compared circulatory Treg frequencies in drug susceptible (DS) and MDR TB before and after anti-TB treatment. Circulatory Treg frequencies were measured in blood samples from 33 DS TB, 7 mycobacterial culture-positive active MDR TB, 16 stable MDR TB who had been culture negative for at least 6 months, and 14 healthy controls before and after treatment. Treg frequency was measured by flow cytometry using cell-surface marker CD4 and intracellular marker FoxP3. Treg frequency was higher in DS TB and active MDR TB patients than in healthy controls (p < 0.05), with no significant difference between the former. Treg frequency was higher in patients with sputum acid-fast bacilli smear-positive TB than in patients with smear-negative TB, but the increase did not correlate with the radiologic extent of TB or presence of a cavity. After successful treatment, Treg decreased to control levels in DS TB and MDR TB patents. The pattern of change, in which Treg frequency increased during active infection and normalized to control levels after successful treatment, was similar in DS and MDR TB patients.

Expansion of pathogen-specific T-helper 1 and T-helper 17 cells in pulmonary tuberculosis with coincident type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus (DM) is a major risk factor for the development of active pulmonary tuberculosis, although the immunological mechanisms underlying this interaction remain unexplored. The influence of poorly controlled diabetes on pathogen-specific T-helper 1 (Th1) and T-helper 17 (Th17) responses have not been examined.

METHODS

To identify the role of Th1 and Th17 cells in tuberculosis with coincident DM, we examined mycobacteria-specific immune responses in the whole blood of individuals who had tuberculosis with DM and compared them to those in individuals who had tuberculosis without DM.

RESULTS

Tuberculosis coincident with DM is characterized by elevated frequencies of monofunctional and dual-functional CD4(+) Th1 cells following Mycobacterium tuberculosis antigen stimulation and elevated frequencies of Th17 subsets at both baseline and following antigen stimulation. This was associated with increased systemic (plasma) levels of both Th1 and Th17 cytokines and decreased baseline frequencies of natural regulatory T cells but not interleukin 10 or transforming growth factor β.

CONCLUSIONS

Therefore, our data reveal that tuberculosis in persons with DM is characterized by elevated frequencies of Th1 and Th17 cells, indicating that DM is associated with an alteration in the immune response to tuberculosis, leading to a biased induction of Th1- and Th17-mediated cellular responses and likely contributing to increased immune pathology in M. tuberculosis infection.

Inhibiting the programmed death 1 pathway rescues Mycobacterium tuberculosis-specific interferon γ-producing T cells from apoptosis in patients with pulmonary tuberculosis

BACKGROUND

Overexpression of programmed death 1 (PD-1) receptor is thought to inhibit the effector T-cell response in human tuberculosis. However, the precise mechanism of such inhibition remains unclear. The present study addresses the role of PD-1 in dampening host T-cell function among patients with pulmonary tuberculosis.

METHODS

Expression of PD-1 and its ligands (PD-L1/L2) on T cells, B cells, and monocytes was evaluated by flow cytometry (FACS). In vitro stimulation of peripheral blood mononuclear cells in the presence of Mycobacterium tuberculosis antigens was performed with and without blocking PD-1, and intracellular cytokine production was measured by FACS.

RESULTS

We showed higher frequencies of T cells, monocytes, and B cells expressing PD-1 and its ligand(s) among patients with pulmonary tuberculosis. Infections with live M. tuberculosis upregulated PD-L1 expression on monocytes. In vitro PD-1 blocking rescued M. tuberculosis-specific interferon γ (IFN-γ)-producing T cells from undergoing apoptosis. The number of PD-1-expressing T cells decreased significantly during therapy and inversely correlated with IFN-γ-dominant T-cell response against M. tuberculosis.

CONCLUSIONS

Manipulation of PD-1 signaling may restore the host T-cell response and thus may have therapeutic potential. PD-1 also may serve as a biomarker to monitor host immunity among patients with tuberculosis during therapy and vaccine studies.

Recruitment of Th1 effector cells in human tuberculosis: hierarchy of chemokine receptor(s) and their ligands

Selective recruitment of IFN-γ biased Th1 effector cells at the pathologic site(s) determines the local immunity of tuberculosis (TB). We observed the enrichment of CXCR3, CCR5 and CD11a(high) T cells in the peripheral blood, pleural fluid and bronchoalveolar lavage of TB pleural effusion (TB-PE) and miliary tuberculosis (MTB) patients respectively. CXCR3(+)CCR5(+) T cells were significantly high at the local disease site(s) in both the forms of TB and their frequency was highest among activated lymphocytes in TB-PE. Interestingly, all CCR5(+) cells were invariably positive for CXCR3 but all CXCR3(+) cells did not co-express CCR5 in pleural fluid whereas the situation was reverse in bronchoalveolar lavage. These CXCR3(+)CCR5(+) cells dominantly produced IFN-γ in response to Mycobacterium tuberculosis antigen. In vitro chemotaxis assay indicates dominant role of RANTES and IP-10 in the selective recruitment of CXCR3(+)CCR5(+)cells at the tubercular pathologic sites.

Subpopulations of helper T lymphocytes in tuberculous pleurisy

Although it is curable, tuberculosis continues to be is a major global public health problem, especially in developing countries. Tuberculous pleural effusion (TPE) is one of the most common forms of extrapulmonary tuberculosis. It has been well documented that CD4(+) T lymphocytes are dominant leukocytes present in TPE. Traditionally, CD4(+) T cells have been classified into two functionally distinct subsets, helper T-cell type 1 (Th1) and Th2 cells, based on their cytokine production profiles. Recently, regulatory T cells, Th17 cells, Th9 cells, and Th22 cells have been added to the 'portfolio' of Th cells. In this review, we summarize recent findings regarding the phenotypic characteristics of the above Th cells, the mechanisms of differentiation and recruitment of Th cells into pleural space, and the immune regulation of Th cells in TPE environment. We also describe the interplay between different Th cells, as well as between Th cells and other type of cells, such as pleural mesothelial cells in TPE. Further studies should be directed at identifying the mediators and mechanisms involved in the immunoregulatory properties of pleural Th cells in tuberculosis infection.

Foxp3 expression and nitric oxide production in peripheral blood mononuclear cells of communicants with pulmonary tuberculosis

The understanding of the mechanisms involved in the immune response is of significant relevance to the control of tuberculosis (TB), especially in individuals living with patients with TB. To characterize the nitric oxide (NO) production and the Foxp3 marker expression in this population, peripheral blood mononuclear cells of intradomiciliary contacts of individuals with pulmonary tuberculosis with (CTb, susceptible) and without (STb, resistant) previous history of active infection were stimulated in vitro with Mycobacterium tuberculosis antigen (TbAg) and with the mitogen Concanavalin A for 24 and 48 h. The groups analysed did not present significant difference in the Foxp3 mRNA expression nor in the NO production. Negative correlation (P = 0.09) between NO and Foxp3 after a 48-h stimulation with TbAg was observed in the STb group. In this group, after a 24-h culture stimulated with TbAg (P = 0.03), this same correlation was observed. In comparison with the cytokines previously studied by our group (Cavalcanti et al., 2009), a positive correlation was observed between IL-10 and Foxp3 after a 48-h culture of cells from communicants susceptible to tuberculosis (STb) stimulated with TbAg (P = 0.04). Evaluating the entire population, a positive correlation was observed between the cytokine TNF-α and the Foxp3 marker in the cultures stimulated for 24 (P = 0.03) and 48 (P = 0.02) hours with TbAg. Therefore, considering the similarity in the exposure and the individual capacity of responding to the contact with M. tuberculosis, the present study contributes to the comprehension of the immune regulation in individuals living with patients with TB.

Different immunosuppressive mechanisms in multi-drug-resistant tuberculosis and non-tuberculous mycobacteria patients

Previous studies have demonstrated that cells from both multi-drug-resistant tuberculosis (MDR-TB) and non-tuberculous mycobacteria (NTM) patients respond poorly to mycobacterial antigens in vitro. In the present study, we compared the in vitro response of cells isolated from sensitive TB (NR-TB)-, MDR-TB- and NTM-infected patients. Analysis of T cell phenotype ex vivo revealed that both MDR-TB and NTM patients present an increased percentage of CD4(+) CD25(+-) forkhead box protein 3 (FoxP3)(+) and CD4(+) CD25(+) CD127(-) regulatory T (T(reg) ) cells when compared to NR-TB. Increased numbers of T(reg) cells and interleukin (IL)-10 serum levels were detected in MDR-TB, whereas elevated serum transforming growth factor (TGF)-β was found in the NTM group. Cells of MDR-TB patients stimulated with early secretory antigenic target (ESAT)-6, but not purified protein derivative (PPD), showed a lower frequency of CD4(+) /interferon (IFN)-γ(+) T cells and enhanced CD4(+) CD25(+) FoxP3(+) , CD4(+) CD25(+) CD127(-) and CD4(+) CD25(+) IL-10(+) T cell population. In addition, increased IL-10 secretion was observed in cultured MDR-TB cells following ESAT-6 stimulation, but not in NR-TB or NTM patients. In vitro blockade of IL-10 or IL-10Rα decreased the CD4(+) CD25(+) FoxP3(+) frequencies induced by ESAT-6 in MDR-TB, suggesting a role of IL-10 on impaired IFN-γ responses seen in MDR-TB. Depletion of CD4(+) CD25(+) T lymphocytes restored the capacity of MDR-TB T cells to respond to ESAT-6 in vitro, which suggests a potential role for T(reg) /T regulatory 1 cells in the pathogenesis of MDR-TB. Together, our results indicate that although the similarities in chronicity, NTM- and MDR-TB-impaired antigenic responses involve different mechanisms.

Expansion of pathogen-specific mono- and multifunctional Th1 and Th17 cells in multi-focal tuberculous lymphadenitis

Background

Th1 and Th17 responses are known to play an important role in immunity to pulmonary tuberculosis (PTB), although little is known about their role in extrapulmonary forms of tuberculosis (TB).

Methods

To identify the role of Th1, Th17, and Th22 cells in multi-focal TB lymphadenitis (TBL), we examined mycobacteria–specific immune responses in the whole blood of individuals with PTB (n = 20) and compared them with those with TBL (n = 25).

Results

Elevated frequencies of CD4⁺ T cells expressing IFN- γ, TNF-α, and IL-2 were present in individuals with TBL compared with those with PTB at baseline and in response to ESAT-6 and CFP-10. Similarly, increased frequencies of CD4⁺ T cells expressing IL-17A, IL-17F, and IFN-γ were also present in individuals with TBL at baseline and following ESAT-6 and CFP-10 stimulation although no significant difference in frequency of Th22 cells was observed. Finally, frequencies of Th1 (but not Th17) cells exhibited a significantly negative correlation with natural regulatory T cell frequencies at baseline.

Conclusions

Multi-focal TB lymphadenitis is therefore characterized by elevated frequencies of Th1 and Th17 cells, indicating that Th1 and Th17 responses in TB disease are probably correlates of disease severity rather than of protective immunity.

Diagnosis and management of miliary tuberculosis: current state and future perspectives

Tuberculosis (TB) remains one of the most important causes of death from an infectious disease, and it poses formidable challenges to global health at the public health, scientific, and political level. Miliary TB is a potentially fatal form of TB that results from massive lymphohematogenous dissemination of Mycobacterium tuberculosis bacilli. The epidemiology of miliary TB has been altered by the emergence of the human immunodeficiency virus (HIV) infection and widespread use of immunosuppressive drugs. Diagnosis of miliary TB is a challenge that can perplex even the most experienced clinicians. There are nonspecific clinical symptoms, and the chest radiographs do not always reveal classical miliary changes. Atypical presentations like cryptic miliary TB and acute respiratory distress syndrome often lead to delayed diagnosis. High-resolution computed tomography (HRCT) is relatively more sensitive and shows randomly distributed miliary nodules. In extrapulmonary locations, ultrasonography, CT, and magnetic resonance imaging are useful in discerning the extent of organ involvement by lesions of miliary TB. Recently, positron-emission tomographic CT has been investigated as a promising tool for evaluation of suspected TB. Fundus examination for choroid tubercles, histopathological examination of tissue biopsy specimens, and rapid culture methods for isolation of M. tuberculosis in sputum, body fluids, and other body tissues aid in confirming the diagnosis. Several novel diagnostic tests have recently become available for detecting active TB disease, screening for latent M. tuberculosis infection, and identifying drug-resistant strains of M. tuberculosis. However, progress toward a robust point-of-care test has been limited, and novel biomarker discovery remains challenging. A high index of clinical suspicion and early diagnosis and timely institution of antituberculosis treatment can be lifesaving. Response to first-line antituberculosis drugs is good, but drug-induced hepatotoxicity and drug-drug interactions in HIV/TB coinfected patients create significant problems during treatment. Data available from randomized controlled trials are insufficient to define the optimum regimen and duration of treatment in patients with drug-sensitive as well as drug-resistant miliary TB, including those with HIV/AIDS, and the role of adjunctive corticosteroid treatment has not been properly studied. Research is going on worldwide in an attempt to provide a more effective vaccine than bacille Calmette-Guérin. This review highlights the epidemiology and clinical manifestation of miliary TB, challenges, recent advances, needs, and opportunities related to TB diagnostics and treatment.

Significance of the frequency of CD4+CD25+CD127- T-cells in patients with pulmonary tuberculosis and diabetes mellitus

BACKGROUND AND OBJECTIVE

Pulmonary tuberculosis and diabetes mellitus (DM) are closely associated. The objective of this study was to determine whether the expression of CD4+CD25+CD127- T-cells (regulatory T-cells (Treg)) is associated with diabetic pulmonary tuberculosis.

METHODS

Flow cytometry was used to determine the frequencies of CD4+CD25+ and CD4+CD25+CD127- T-cells in peripheral blood, bronchoalveolar lavage fluid (BALF) and pleural effusions from 120 patients (30 with pulmonary tuberculosis and DM (TBDM), 30 with pulmonary tuberculosis without DM (TB), 30 with tuberculous pleurisy without DM (TBP) and 30 healthy volunteers). The concentrations of interferon (IFN)-γ and interleukin (IL)-10 in BALF and pleural effusions were determined by enzyme-linked immunosorbent assay.

RESULTS

Treg frequencies in peripheral blood were significantly higher in patients with TBDM, TB and TBP than in the control group, with the frequency in TBDM being the highest (P < 0.01 for all). In TBP patients, Treg frequencies were significantly lower in pleural effusions than in peripheral blood. In TB patients, Treg frequencies in BALF and peripheral blood were not significantly different. However, in TBDM patients, Treg frequencies were significantly higher in BALF than in peripheral blood. IL-10 expression was significantly higher, and IFN-γ expression was significantly lower in BALF of TBDM patients compared with BALF and pleural effusions of TB patients.

CONCLUSIONS

In patients with pulmonary tuberculosis and DM, the imbalance between Treg and effector T-cells at pathological sites may be associated with weakened immunity and clinical manifestations of 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.

Peripheral T cell cytokine responses for diagnosis of active tuberculosis

BACKGROUND

A test for diagnosis of active Tuberculosis (TB) from peripheral blood could tremendously improve clinical management of patients.

METHODS

Of 178 prospectively enrolled patients with possible TB, 60 patients were diagnosed with pulmonary and 27 patients with extrapulmonary TB. The frequencies of Mycobacterium tuberculosis (MTB) specific CD4(+) T cells and CD8(+) T cells producing cytokines were assessed using overnight stimulation with purified protein derivate (PPD) or early secretory antigenic target (ESAT)-6, respectively.

RESULTS

Among patients with active TB, an increased type 1 cytokine profile consisting of mainly CD4(+) T cell derived interferon (IFN)-γ was detectable. Despite contributing to the cytokine profile as a whole, the independent diagnostic performance of one cytokine producing T cells as well as polyfunctional T cells was poor. IFN-γ/Interleukin(IL)-2 cytokine ratios discriminated best between active TB and other diseases.

CONCLUSION

T cells producing one cytokine and polyfunctional T cells have a limited role in diagnosis of active TB. The significant shift from a "memory type" to an "effector type" cytokine profile may be useful for further development of a rapid immune-diagnostic tool for active TB.

IL-2 simultaneously expands Foxp3+ T regulatory and T effector cells and confers resistance to severe tuberculosis (TB): implicative Treg-T effector cooperation in immunity to TB

The possibility that simultaneous expansion of T regulatory cells (Treg) and T effector cells early postinfection can confer some immunological benefits has not been studied. In this study, we tested the hypothesis that early, simultaneous cytokine expansion of Treg and T effector cells in a tissue infection site can allow these T cell populations to act in concert to control tissue inflammation/damage while containing infection. IL-2 treatments early after Mycobacterium tuberculosis infection of macaques induced simultaneous expansion of CD4(+)CD25(+)Foxp3(+) Treg, CD8(+)CD25(+)Foxp3(+) T cells, and CD4(+) T effector/CD8(+) T effector/Vγ2Vδ2 T effector populations producing anti-M. tuberculosis cytokines IFN-γ and perforin, and conferred resistance to severe TB inflammation and lesions. IL-2-expanded Foxp3(+) Treg readily accumulated in pulmonary compartment, but despite this, rapid pulmonary trafficking/accumulation of IL-2-activated T effector populations still occurred. Such simultaneous recruitments of IL-2-expanded Treg and T effector populations to pulmonary compartment during M. tuberculosis infection correlated with IL-2-induced resistance to TB lesions without causing Treg-associated increases in M. tuberculosis burdens. In vivo depletion of IL-2-expanded CD4(+)Foxp3(+) Treg and CD4(+) T effectors during IL-2 treatment of M. tuberculosis-infected macaques significantly reduced IL-2-induced resistance to TB lesions, suggesting that IL-2-expanded CD4(+) T effector cells and Treg contributed to anti-TB immunity. Thus, IL-2 can simultaneously activate and expand T effector cells and Foxp3(+) Treg populations and confer resistance to severe TB without enhancing M. tuberculosis infection.

Regulatory T cells suppress T cell activation at the pathologic site of human visceral leishmaniasis

Suppression of T cell response is thought to be involved in the pathogenesis of visceral leishmaniasis (VL). Regulatory T cell (Treg) mediated immune-suppression is reported in animal models of Leishmania infection. However, their precise role among human patients still requires pathologic validation. The present study is aimed at understanding the frequency dynamics and function of Treg cells in the blood and bone marrow (BM) of VL patients. The study included 42 parasitologically confirmed patients, 17 healthy contact and 9 normal bone marrow specimens (NBM). We show i) the selective accumulation of Treg cells at one of the disease inflicted site(s), the BM, ii) their in vitro expansion in response to LD antigen and iii) persistence after successful chemotherapy. Results indicate that the Treg cells isolated from BM produces IL-10 and may inhibit T cell activation in IL-10 dependent manner. Moreover, we observed significantly higher levels of IL-10 among drug unresponsive patients, suggesting their critical role in suppression of immunity among VL patients. Our results suggest that IL-10 plays an important role in suppression of host immunity in human VL and possibly determines the efficacy of chemotherapy.

Crohn's disease and Mycobacterium avium subsp. paratuberculosis: the need for a study is long overdue

The initial suggestion that Mycobacterium avium subsp. paratuberculosis (Map) might be involved in the pathogenesis of Crohn's disease (CD) was based on the apparent similarity of lesions in the intestine of patients with CD with those present in cattle infected with Map, the etiological agent of Johne's disease (JD). Recent investigations have now revealed the presence of Map or Map DNA in blood or lesions from adults and children with CD. Of special interest, Map has also been found in patients with other diseases as well as healthy subjects. The latter observations indicate all humans are susceptible to infection with Map and that, like with other mycobacterial pathogens such as Mycobacterium tuberculosis, infection does not invariably lead to development of clinical disease but rather development of a persistent latent stage of infection where an immune response controls but does not eliminate the pathogen. Limited information has been obtained on the immune response to Map in healthy subjects and patients with CD. Understanding how Map may be involved in the pathogenesis of CD will require a better understanding of the immune response to Map in one of its common hosts as well as healthy humans and patients with CD.

Increased frequency of regulatory T cells and T lymphocyte activation in persons with previously treated extrapulmonary tuberculosis

Extrapulmonary tuberculosis may be due to underlying immune compromise. Immunosuppressive regulatory T cells (Treg cells), and CD4(+) T lymphocytes in general, are important in the host immune response to Mycobacterium tuberculosis. We evaluated T lymphocytes from patients after recovery from extrapulmonary tuberculosis, which may reflect conditions before M. tuberculosis infection. A case-control study was conducted among HIV-uninfected adults with previously treated extrapulmonary tuberculosis and 3 sets of controls: (i) subjects with previously treated pulmonary tuberculosis, (ii) close tuberculosis contacts with M. tuberculosis infection, and (iii) close tuberculosis contacts with no infection. Monocyte-depleted peripheral blood mononuclear cells (PBMC-M) were stained for CD4(+) CD25(hi) CD127(low) FoxP3(+) cell (Treg cell) and T lymphocyte activation. Both characteristics were compared as continuous variables between groups with the Kruskal-Wallis test. There were 7 extrapulmonary tuberculosis cases, 18 pulmonary tuberculosis controls, 17 controls with M. tuberculosis infection, and 18 controls without M. tuberculosis infection. The median Treg cell proportion was highest among persons with previous extrapulmonary tuberculosis (1.23%) compared to subjects with pulmonary tuberculosis (0.56%), latent M. tuberculosis infection (0.14%), or no M. tuberculosis infection (0.20%) (P = 0.001). The median proportion of CD4(+) T lymphocytes that expressed the activation markers HLA-DR and CD38 was highest for CD4(+) T lymphocytes from persons with previous extrapulmonary tuberculosis (0.79%) compared to subjects with pulmonary tuberculosis (0.44%), latent M. tuberculosis infection (0.14%), or no M. tuberculosis infection (0.32%) (P = 0.005). Compared with controls, persons with previously treated extrapulmonary tuberculosis had the highest Treg cell frequency, but also the highest levels of CD4(+) T lymphocyte activation. Immune dysregulation may be a feature of individuals at risk for extrapulmonary tuberculosis.

Tuberculosis pathogenesis and immunity

Despite the development of potentially curative chemotherapy, tuberculosis (TB) continues to cause increasing worldwide morbidity and is a leading cause of human mortality in the developing world. Recent advances in bacterial molecular genetics, immunology, and human genetics have yielded insight into the molecular determinants of virulence, the immune responses that are essential for restricting progressive disease, and the determinants of immunopathology in TB. Despite these advances, a large knowledge gap still exists that limits the development and testing of new interventions, including novel drugs and efficacious vaccines. This review focuses on our current knowledge of TB pathogenesis and immunity that has been derived from in vitro and in vivo studies. In addition, it highlights topics that need to be better understood to provide improved means of controlling TB worldwide.

Immune Responses of HIV-1 Tat Transgenic Mice to Mycobacterium Tuberculosis W-Beijing SA161

Background:

Mycobacterium tuberculosis remains among the leading causes of death from an infectious agent in the world and exacerbates disease caused by the human immunodeficiency virus (HIV). HIV infected individuals are prone to lung infections by a variety of microbial pathogens, including M. tuberculosis. While the destruction of the adaptive immune response by HIV is well understood, the actual pathogenesis of tuberculosis in co-infected individuals remains unclear. Tat is an HIV protein essential for efficient viral gene transcription, is secreted from infected cells, and is known to influence a variety of host inflammatory responses. We hypothesize Tat contributes to pathophysiological changes in the lung microenvironment, resulting in impaired host immune responses to infection by M. tuberculosis.

Results:

Herein, we show transgenic mice that express Tat by lung alveolar cells are more susceptible than non-transgenic control littermates to a low-dose aerosol infection of M. tuberculosis W-Beijing SA161. Survival assays demonstrate accelerated mortality rates of the Tat transgenic mice compared to non-transgenics. Tat transgenic mice also showed poorly organized lung granulomata-like lesions. Analysis of the host immune response using quantitative RT-PCR, flow cytometry for surface markers, and intracellular cytokine staining showed increased expression of pro-inflammatory cytokines in the lungs, increased numbers of cells expressing ICAM1, increased numbers of CD4+CD25+Foxp3+ T regulatory cells, and IL-4 producing CD4+ T cells in the Tat transgenics compared to infected non-tg mice.

Conclusions:

Our data show quantitative differences in the inflammatory response to the SA161 clinical isolate of M. tuberculosis W-Beijing between Tat transgenic and non-transgenic mice, suggesting Tat contributes to the pathogenesis of tuberculosis.

Increased virulence of an epidemic strain of Mycobacterium massiliense in mice

BACKGROUND

Chronic pulmonary disease and skin/soft tissue infections due to non-tuberculous mycobacteria (NTM) of the Mycobacterium chelonae-abscessus-massiliense group is an emerging health problem worldwide. Moreover, the cure rate for the infections this group causes is low despite aggressive treatment. Post-surgical outbreaks that reached epidemic proportions in Brazil recently were caused by M. massiliense isolates resistant to high-level disinfection with glutaraldehyde (GTA). Understanding the differences in the virulence and host immune responses induced by NTM differing in their sensitivity to disinfectants, and therefore their relative threat of causing outbreaks in hospitals, is an important issue.

METHODOLOGY/PRINCIPAL FINDING

We compared the replication and survival inside macrophages of a GTA-susceptible reference Mycobacterium massiliense clinical isolate CIP 108297 and an epidemic strain from Brazil, CRM-0019, and characterized the immune responses of IFNγ knockout mice exposed to a high dose aerosol with these two isolates. CRM-0019 replicated more efficiently than CIP 108297 inside mouse bone marrow macrophages. Moreover, the animals infected with CRM-0019 showed a progressive lung infection characterized by a delayed influx of CD4+ and CD8+ T cells, culminating in extensive lung consolidation and demonstrated increased numbers of pulmonary CD4+ Foxp3+ regulatory T cells compared to those infected with the reference strain. Immunosuppressive activity of regulatory T cells may contribute to the progression and worsening of NTM disease by preventing the induction of specific protective immune responses.

CONCLUSIONS/SIGNIFICANCE

These results provide the first direct evidence of the increased virulence in macrophages and mice and pathogenicity in vivo of the Brazilian epidemic isolate and the first observation that NTM infections can be associated with variable levels of regulatory T cells which may impact on their virulence and ability to persist in the host.

Identification of M. tuberculosis-specific Th1 cells expressing CD69 generated in vivo in pleural fluid cells from patients with tuberculous pleurisy

Th1 cell-mediated immune responses at the site of active infection are important to restrict the growth of M.tuberculosis (MTB) and for the spontaneous resolution of patients with tuberculous pleurisy (TBP). In the present study, we found that without any stimulation, CD4⁺ T cells in pleural fluid cells (PFCs) from patients with TBP expressed significantly higher levels of CD69 than PBMCs from patients with tuberculosis (TB) or healthy donors. CD4⁺CD69⁺ T cells expressed T-bet and IL-12Rβ2. After stimulation with MTB-specific antigens, CD4⁺CD69⁺ T cells expressed significantly higher levels of IFN-γ, IL-2 and TNF-α than CD4⁺CD69⁻ T cells, demonstrating that CD4⁺CD69⁺ T cells were MTB-specific Th1 cells. In addition, CD4⁺CD69⁺ T cells were mostly polyfunctional Th1 cells that simultaneously produced IFN-γ, IL-2, TNF-α and displayed an effector or effector memory phenotype (CD45RA⁻CCR7⁻CD62L⁻CD27⁻). Moreover, the percentages of CD4⁺CD69⁺ T cells were significantly and positively correlated with polyfunctional T cells. Interestingly, sorted CD4⁺CD69⁺ but not CD4⁺CD69⁻ fractions by flow cytometry produced IFN-γ, IL-2 and TNF-α that were significantly regulated by CD4⁺CD25⁺ Treg cells. Taken together, based on the expression of CD69, we found a direct quantitative and qualitative method to detect and evaluate the in vivo generated MTB-specific polyfunctional CD4⁺ T cells in PFCs from patients with TBP. This method can be used for the potential diagnosis and enrichment or isolation of MTB-specific Th1 cells in the investigations.

Imbalance of Th17 cells and regulatory T cells in tuberculous pleural effusion

Both T helper interleukin 17 (IL-17)-producing cells (Th17 cells) and regulatory T cells (Tregs) have been found to be increased in human tuberculous pleural effusion (TPE); however, the possible interaction between Th17 cells and Tregs in TPE remains to be elucidated. The objective of the present study was to investigate the distribution of Th17 cells in relation to Tregs, as well as the mechanism of Tregs in regulating generation and differentiation of Th17 cells in TPE. In the present study, the numbers of Th17 cells and Tregs in TPE and blood were determined by flow cytometry. The regulation and mechanism of CD39(+) Tregs on generation and differentiation of Th17 cells were explored. Our data demonstrated that the numbers of Th17 cells and CD39(+) Tregs were both increased in TPE compared with blood. Th17 cell numbers were correlated negatively with Tregs in TPE but not in blood. When naïve CD4(+) T cells were cultured with CD39(+) Tregs, Th17 cell numbers decreased as CD39(+) Treg numbers increased, and the addition of the anti-latency-associated peptide monoclonal antibody to the coculture reversed the inhibitory effect exerted by CD39(+) Tregs. This study shows that Th17/Treg imbalance exists in TPE and that pleural CD39(+) Tregs inhibit generation and differentiation of Th17 cells via a latency-associated peptide-dependent mechanism.

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.

Experimental infection of a bovine model with human isolates of Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subsp. paratuberculosis (Map), the etiologic agent of Johne's disease (JD) in ruminants, has been implicated in the pathogenesis of Crohn's disease (CD) in humans. We developed a bovine ileal cannulation model to facilitate comparison of the immune response to Map and the mechanisms of pathogenesis in cattle and humans. Initial studies showed a T cannula could be maintained for up to a year in calves without inducing inflammation or adversely affecting intestinal function. Map introduced through the cannula established a persistent low level of infection without inflammation. Infection elicited an immune response to Map antigens detectable by flow cytometry. Further studies now show the cannulation model can be used with cows during the later stage of infection, affording access to the target tissue at all stages of infection. The studies also revealed no difference in infectivity or immunogenicity of isolates of Map obtained from cattle or humans with CD. Comparison of the immune response to Map during the early and late stages of infection using PCR, flow cytometry and QRT-PCR, showed the immune response early in the disease process is dominated by CD4 T cells. A CD8 response is delayed but comparable at later stages of infection. Genes for pro-inflammatory cytokines IFN-γ and the recently identified genes encoding IL-17 and IL-22 are up regulated in infected animals. These findings reveal that both human and bovine isolates of Map can establish infection and induce similar immune responses in a bovine model. They also reveal the cytokine responses elicited in cattle are similar to those implicated in CD pathogenesis.

Evaluation of two mutants of Mycobacterium avium subsp. paratuberculosis as candidates for a live attenuated vaccine for Johne's disease

Control of Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis, has been difficult because of a lack of an effective vaccine. To address this problem we used targeted gene disruption to develop candidate mutants with impaired capacity to survive ex vivo and in vivo to test as a vaccine. We selected relA and pknG, genes known to be important virulence factors in Mycobacterium tuberculosis and Mycobacterium bovis, for initial studies. Deletion mutants were made in a wild type Map (K10) and its recombinant strain expressing the green fluorescent protein (K10-GFP). Comparison of survival in an ex vivo assay revealed deletion of either gene attenuated survival in monocyte-derived macrophages compared to survival of wild-type K10. In contrast, study in calves revealed survival in vivo was mainly affected by deletion of relA. Bacteria were detected in tissues from wild-type and the pknG mutant infected calves by bacterial culture and PCR at three months post infection. No bacteria were detected in tissues from calves infected with the relA mutant (P<0.05). Flow cytometric analysis of the immune response to the wild-type K10-GFP and the mutant strains showed deletion of either gene did not affect their capacity to elicit a strong proliferative response to soluble antigen extract or live Map. Quantitative RT-PCR revealed genes encoding IFN-γ, IL-17, IL-22, T-bet, RORC, and granulysin were up-regulated in PBMC stimulated with live Map three months post infection compared to the response of PBMC pre-infection. A challenge study in kid goats showed deletion of pknG did not interfere with establishment of an infection. As in calves, deletion of relA attenuated survival in vivo. The mutant also elicited an immune response that limited colonization by challenge wild type Map. The findings show the relA mutant is a good candidate for development of a live attenuated vaccine for Johne's disease.

Programmed death 1 and cytokine inducible SH2-containing protein dependent expansion of regulatory T cells upon stimulation With Mycobacterium tuberculosis

We previously found that CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) expand in response to Mycobacterium tuberculosis infection in individuals who are healthy tuberculin reactors, but not in tuberculin-negative individuals. We also found that the M. tuberculosis mannose-capped lipoarabinomannan and prostaglandin E2 produced by monocytes are involved in Treg expansion. In this study, we found that Tregs expanded from CD4(+)CCR4(+) cells but not from CCR4(-) cells. However, introduction of CCR4 small interfering RNA (siRNA) into CD4(+) cells only marginally reduced expansion of Tregs. Using siRNA and neutralizing antibodies, we found that expansion of Tregs by M. tuberculosis required expression of programmed death1 (PD-1) and expression of the signaling molecule, cytokine inducible SH2-containing protein (CISH). Anti-PD-1 siRNA inhibited expression of CISH by expanded Tregs. M. tuberculosis-expanded Tregs produced transforming growth factor β and interleukin 10 and reduced the frequency of interferon γ-producing autologous CD8(+) cells. We conclude that M. tuberculosis infection induces development of Tregs from CCR4(+) cells through a process that depends on PD-1and CISH.

Mycobacterium tuberculosis PPD-induced immune biomarkers measurable in vitro following BCG vaccination of UK adolescents by multiplex bead array and intracellular cytokine staining

Background

The vaccine efficacy reported following Mycobacterium bovis Bacillus Calmette Guerin (BCG) administration to UK adolescents is 77% and defining the cellular immune response in this group can inform us as to the nature of effective immunity against tuberculosis. The aim of this study was to identify which cytokines and lymphocyte populations characterise the peripheral blood cellular immune response following BCG vaccination.

Results

Diluted blood from before and after vaccination was stimulated with Mycobacterium tuberculosis purified protein derivative for 6 days, after which soluble biomarkers in supernatants were assayed by multiplex bead array. Ten out of twenty biomarkers measured were significantly increased (p < 0.0025) 1 month after BCG vaccination when compared to paired samples (n = 12) taken prior to vaccination (IFNγ, TNFα, IL-1α, IL-2, IL-6, IL-10, IL-17, GM-CSF, MIP1α, IP-10). All of these remained detectable by multiplex bead array in samples taken 12 months after BCG vaccination of a partially overlapping adolescent group (n = 12). Intracellular cytokine staining after 24 hour Mycobacterium tuberculosis purified protein derivative stimulation of PBMC samples from the 12 month group revealed that IFNγ expression was detectable in CD4 and CD8 T-cells and natural killer cells. Polyfunctional flow cytometry analysis demonstrated that cells expressing IFNγ alone formed the majority in each subpopulation of cells. Only in CD4 T-cells and NK cells were there a notable proportion of responding cells of a different phenotype and these were single positive, TNFα producers. No significant expression of the cytokines IL-2, IL-17 or IL-10 was seen in any population of cells.

Conclusions

The broad array of biomarker responses detected by multiplex bead array suggests that BCG vaccination is capable, in this setting, of inducing a complex immune phenotype. Although polyfunctional T-cells have been proposed to play a role in protective immunity, they were not present in vaccinated adolescents who, based on earlier epidemiological studies, should have developed protection against pulmonary tuberculosis. This may be due to the later sampling time point available for testing or on the kinetics of the assays used.

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.

T regulatory cells and Th1/Th2 cytokines in peripheral blood from tuberculosis patients

About 10% of people infected with Mycobacterium tuberculosis develop active tuberculosis (TB), and Th1 effector cells and Th1 cytokines play key roles in controlling M. tuberculosis infection. Here, we hypothesise that this susceptibility to M. tuberculosis infection is linked to increased T regulatory (Treg) cells and Th2 cytokines in TB patients. To test this, we recruited 101 participants (71 TB patients, 12 non-TB pulmonary diseases and 18 healthy subjects) and investigated Treg cells and Th1/Th2 cytokines in peripheral blood. CD4(+)CD25(+) T cells and CD4(+)CD25(+)FoxP3(+) T cells significantly increased and IL-5 dramatically decreased in TB patients relative to healthy subjects. CD8(+)CD28(-) T cells, IFN-gamma, TNF-alpha, IL-10 and IL-4 significantly increased in patients with culture and sputum smear-positive pulmonary TB (PTB(+)) compared with healthy subjects. CD4(+)CD25(+)FoxP3(+) and CD8(+)CD28(-) T cells significantly decreased in PTB(+) after one month of chemotherapy. CD4(+), CD4(+)CD25(+) and CD8(+)CD28(+) T cells significantly increased in extra-pulmonary TB patients after one month of chemotherapy. These findings suggest that M. tuberculosis infection induces circulating CD4(+)CD25(+)FoxP3(+) and CD8(+)CD28(-) T cell expansion, which may be related to the progression of M. tuberculosis infection, and that the balance between effector immune responses and suppression immune responses is essential to control M. tuberculosis infection.

Biomarkers of disease activity, cure, and relapse in tuberculosis

The changing face of tuberculosis, with epidemics fueled by HIV and urbanization in much of the world and a relative increase in the importance of latent tuberculosis as a source of cases in the more economically developed countries, has led to a demand for more robust, clinically applicable diagnostic tools. As a result, research aiming to identify biomarkers of Mycobacterium tuberculosis infection and disease has flourished. This article discusses the most recent findings of that work.

How tolerogenic dendritic cells induce regulatory T cells

Since their discovery by Steinman and Cohn in 1973, dendritic cells (DCs) have become increasingly recognized for their crucial role as regulators of innate and adaptive immunity. DCs are exquisitely adept at acquiring, processing, and presenting antigens to T cells. They also adjust the context (and hence the outcome) of antigen presentation in response to a plethora of environmental inputs that signal the occurrence of pathogens or tissue damage. Such signals generally boost DC maturation, which promotes their migration from peripheral tissues into and within secondary lymphoid organs and their capacity to induce and regulate effector T cell responses. Conversely, more recent observations indicate that DCs are also crucial to ensure immunological peace. Indeed, DCs constantly present innocuous self- and nonself-antigens in a fashion that promotes tolerance, at least in part, through the control of regulatory T cells (Tregs). Tregs are specialized T cells that exert their immunosuppressive function through a variety of mechanisms affecting both DCs and effector cells. Here, we review recent advances in our understanding of the relationship between tolerogenic DCs and Tregs.