Analysis of Mycobacterium tuberculosis-specific CD8 T-cells in patients with active tuberculosis and in individuals with latent infection

CD8 T-cells contribute to control of Mycobacterium tuberculosis infection, but little is known about the quality of the CD8 T-cell response in subjects with latent infection and in patients with active tuberculosis disease. CD8 T-cells recognizing epitopes from 6 different proteins of Mycobacterium tuberculosis were detected by tetramer staining. Intracellular cytokines staining for specific production of IFN-γ and IL-2 was performed, complemented by phenotyping of memory markers on antigen-specific CD8 T-cells. The ex-vivo frequencies of tetramer-specific CD8 T-cells in tuberculous patients before therapy were lower than in subjects with latent infection, but increased at four months after therapy to comparable percentages detected in subjects with latent infection. The majority of CD8 T-cells from subjects with latent infection expressed a terminally-differentiated phenotype (CD45RA⁺CCR7⁻). In contrast, tuberculous patients had only 35% of antigen-specific CD8 T-cells expressing this phenotype, while containing higher proportions of cells with an effector memory- and a central memory-like phenotype, and which did not change significantly after therapy. CD8 T-cells from subjects with latent infection showed a codominance of IL-2⁺/IFN-γ⁺ and IL-2⁻/IFN-γ⁺ T-cell populations; interestingly, only the IL-2⁺/IFN-γ⁺ population was reduced or absent in tuberculous patients, highly suggestive of a restricted functional profile of Mycobacterium tuberculosis-specific CD8 T-cells during active disease. These results suggest distinct Mycobacterium tuberculosis specific CD8 T-cell phenotypic and functional signatures between subjects which control infection (subjects with latent infection) and those who do not (patients with active disease).

Induced sputum as a tool for early detection of airway inflammation in connective diseases-related lung involvement

BACKGROUND

Induced sputum (IS) sampling is a safe and validated approach to study bronchial inflammation in chronic obstructive lung diseases. Although promising results have also been reported in various diffuse interstitial lung disorders, the potential use of IS in the assessment of connective tissue diseases (CTD)-related lung involvement has not yet been investigated.

AIM OF THE STUDY

To evaluate the clinical usefulness of IS in the early management of patients suffering from rheumatoid arthritis (RA) and systemic sclerosis (SSc) at the onset of respiratory symptoms.

PATIENTS AND METHODS

The study population included 19 patients (RA=12; SSc=7) and 14 age- and sex-matched healthy volunteers. Lung function testing, high resolution computed tomography (HRCT) of the thorax and IS collection were performed in all cases. Broncho-alveolar lavage (BAL) was obtained in selected patients.

RESULTS

IS samples from patients contained a significantly higher percentage of neutrophils and a lower percentage of macrophages compared to healthy subjects (p=0.002 and 0.001, respectively), while the total cell number showed no differences. In addition, sputa yielded both higher cell counts and higher neutrophils than BAL samples (p=0.02 in all instances). No correlations were found between IS findings and lung function parameters, HRCT and BAL findings.

CONCLUSIONS

This is the first study investigating the inflammatory cell pattern in IS from CTD patients with early clinical evidence of lung involvement. Future studies are needed to determine whether the assessment of airway inflammation adds significant information that may result in a relevant improvement of disease management.

Autonomic nervous system dysfunction in the course of active pulmonary tuberculosis

BACKGROUND

Functional alterations of the autonomic nervous system have been described in relation to chronic hypoxemia in chronic obstructive pulmonary diseases. Aim of the present study was to investigate the occurrence of neuro-vegetative dysfunction during active tuberculosis in the absence of hypoxemia.

MATERIALS AND METHODS

Fifteen patients affected by pulmonary tuberculosis under standard therapy and 17 matched controls were enrolled. Activation of the sympathetic system was induced by the tilt-up test. Systolic and diastolic arterial pressures and the R-R interval were monitored for 15 min by Finapres and ECG. The baroreflex sensitivity was evaluated by the spontaneous sequences method.

RESULTS

Systolic and diastolic pressures were significantly higher at basal conditions and showed a less increase during the tilt test in tuberculosis patients compared to healthy controls. The basal R-R interval was shorter and its reduction during the tilt test was less evident in patients. The baroreflex sensitivity was decreased in patients at basal conditions and its reduction during the tilt test was less evident than in controls.

CONCLUSIONS

Our preliminary results suggest the presence in tuberculosis patients of an altered autonomic cardiovascular regulation, which is a reduced function of the baroreflex control of the sinus node.

New insights on the perturbations of T cell cycle during HIV infection

The role of the Human Immunodeficiency Virus (HIV) in the pathogenesis of the Acquired Immune-Deficiency Syndrome (AIDS) is changed. Direct HIV-mediated killing of CD4(+) T cells is not the only mechanism leading to lymphocyte depletion. There is increasing evidence that, during the chronic phases of infection, T cell activation, accelerated cell turnover, and cytokines imbalance induce the so-called cell cycle dysregulation (CCD). CCD is a recently discovered immune-pathogenic mechanism that mainly induces the depletion of both CD4(+) and CD8(+) uninfected T cells. It is due to a significant perturbation of protein metabolism as ubiquitin pathway defects of protein degradation are associated with an increased and unscheduled expression of cyclin B and p34 cdc kinase. Moreover, significant changes in the nucleolar structure and post-translational regulation of nucleolin have also been described. As modulation of CCD by anti-retroviral and immune-therapies has been suggested to predict a good immunological response in HIV-infected patients, a better understanding of such a mechanism is needed in order to further clarify its role in the pathogenesis and progression of HIV infection.

Does sphingosine 1-phosphate play a protective role in the course of pulmonary tuberculosis?

Sphingosine 1-phosphate (S1P) has recently been reported to induce antimycobacterial activity in vitro and in a mouse model of in vivo Mycobacterium tuberculosis infection. However, its role in the course of pulmonary tuberculosis in humans is still not known. This study shows that S1P levels in airway surface fluid of tuberculosis (TB) patients are significantly less than those observed in non-TB control patients. Moreover, the in vitro stimulation of bronchoalveolar lavage cells coming from TB patients with S1P significantly reduces intracellular growth of endogenous mycobacterial isolates. These results show that, in the course of pulmonary TB, airway epithelial fluid-associated S1P may play a protective role in the containment of intracellular mycobacterial growth and that its decrease may represent a novel pathogenic mechanism through which M. tuberculosis favors its replication.

Immunogenetics of severe respiratory infections: models for the development of new therapeutic strategies

Innate and adaptive immunity plays a critical role in the defence of the lung and other mucosal surfaces exposed to micro-organisms. Anti-microbial peptides and proteins, cytokines and chemokines are important immune weapons as they build up the protective front for the respiratory tract. The notion that susceptibility to infectious diseases may be inherited is widely accepted and, as it is the failure to activate adaptive immunity that may allow infection to become established and progress toward invasion and dissemination, the recognition of specific gene defects affecting the ability of the immune system to overcome invading pathogens may shed light upon those mechanisms of immune regulation that are playing the most critical roles. The aim of the present review is to discuss some of the advances in infection immunogenetics that may lead to identify new strategies in the development of new anti-infectious and anti-inflammatory drugs.

Transcriptional profile of the immune response in the lungs of patients with active tuberculosis

Despite advances in diagnosis and treatment, Mycobacterium tuberculosis causes active disease in about 8 million people worldwide annually. The study of the interplay between the host and the pathogen at the site of infection in human TB may contribute to elucidate the pathogenesis of the disease. In this work, using macroarray technology and real-time PCR, we analyzed the modulation of 847 genes encoding immune-inflammatory mediators in BALF samples of patients affected by active pulmonary TB (PTB) and control patients affected by non-TB diseases. The data show that the PTB milieu contains a complex network of gene activation. Different genes with adhesive properties and involved in tissue repair and fibrosis were modulated. In TB patients, we observed the up-regulation of cytokines, including IFN-gamma and IFN-gamma pathway genes, of several apoptotic genes, and of potent transcriptional activators. These findings can contribute to elucidate the mechanisms of MTB pathogenicity in humans.

Lysophosphatidic acid enhances antimycobacterial activity both in vitro and ex vivo

Lysophosphatidic acid (LPA) is a polar lipid metabolite which is involved in a wide range of biological processes, including cell proliferation and migration, wound healing, and increase of endothelial permeability. The present study reports evidences showing that LPA is able to enhance the antimicrobial activity of human macrophages and of bronchoalveolar lavage cells from tuberculosis patients leading to intracellular growth control of Mycobacterium tuberculosis. Such antimicrobial activity is mediated by the activation of phospholipase D which in turn induces acidification of M. tuberculosis containing phagosomes and is associated with the enhanced expression of Cathepsin D. These results suggest the possible protective role of this lysophospholipid in the activation of innate antimycobacterial response.

Molecular diagnosis of fatal Nocardia farcinica pneumonia in an HIV-negative patient

Nocardiosis is a rare and potentially life-threatening infection caused by several species of the Nocardia genus. Most cases occur in immunocompromised patients, and a delay in establishing the diagnosis is common due to the non-specific clinical presentations and the difficulty in cultivating Nocardia. Although the majority of pulmonary nocardiosis cases are caused by Nocardia asteroides, cases of human infection due to N. farcinica are increasingly diagnosed due to recent developments in taxonomy and diagnostic methods. N. farcinica is a separate species from N. asteroides and appears to be more virulent and resistant to antibiotics. Herein, we describe the case of a 65-year-old HIV-negative immunocompromised patient with a fulminant bilateral pulmonary nocardiosis while on empirical treatment with trimethoprim/sulfamethoxazole and imipenem. Post-mortem diagnosis of N. farcinica infection was performed by means of DNA amplification and sequencing of the 65-kDa bacterial heat shock protein.

Cost determinants of tuberculosis management in a low-prevalence country

SETTING

Division of respiratory medicine in a specialised infectious disease hospital in Rome, Italy.

OBJECTIVE

Retrospective evaluation of tuberculosis (TB) care associated costs in an integrated in- and out-patient management programme.

DESIGN

Review of the medical records of 92 human immunodeficiency virus negative TB cases admitted between September 2000 and May 2003.

RESULTS

Length of in-hospital stay (45 +/- 35 days) was the major cost determinant, as hospitalisation accounted for almost 80% of the total costs of the case, with fixed bed-per-day charges amounting to 76% of hospital costs. Factors associated with higher costs were chest X-ray score, fever, sputum bacterial load and multidrug resistance (P < 0.05). Cure/treatment completion was achieved in 82% of patients entering the out-patient programme (63% of all cases). Homelessness, age and comorbidities were associated with unfavourable outcomes.

CONCLUSIONS

A closely followed hospital-centred protocol carried out in a high-resource setting may produce acceptable cure/completion treatment rates. As a too high fraction of resources invested in TB control goes toward hospital costs, out-patient treatment strategies should be implemented.

Expansion of CCR5+ CD4+ T-lymphocytes in the course of active pulmonary tuberculosis

Nonsyncytium inducing, macrophage tropic HIV strains predominate in the course of active tuberculosis (TB). The present study assesses the expression of CCR5 in CD4+ T-lymphocytes from blood and bronchoalveolar lavage (BAL) of TB patients, non-TB lung disease controls and healthy controls. Memory (CD45RO+), recently activated (CD69+), proliferating (Ki67+) CCR5+ or CCR3+ CD4+ T-lymphocytes were determined by multiparametric flow cytometry analysis. Results show that BAL CD4+ T-lymphocytes expressing CCR5 or CCR3 were significantly increased when compared to peripheral blood both in patients and in healthy controls. However, the data show that the proportions of peripheral blood CCR5+ CD4+ and CCR3+ CD4+ T-lymphocytes and BAL CCR5+ CD4+ T-lymphocytes, but not BAL CCR3+ CD4+ T-lymphocytes, were significantly increased in TB patients. Furthermore, the observation that BAL CCR5+ CD4+ T-lymphocytes from TB patients expressed early activation markers, were not proliferating and showed down-regulation of CCR5 expression suggests recruitment and trapping at the site of disease. Altogether, these results suggest that the lower respiratory tract mucosa may provide cellular targets accessible for efficient transmission of macrophage tropic HIV-1 variants and that tuberculosis may enhance this phenomenon.

Role of mycobacteria-induced monocyte/macrophage apoptosis in the pathogenesis of human tuberculosis

Apoptosis is a physiological programmed cell death process whose dysregulation plays an important role in different human infectious diseases. An increasing number of intracellular pathogens are known to induce target cell apoptosis, while some other parasites inhibit it. Unlike necrosis, apoptosis is a silent immunological event occurring without inflammation. Infection-induced target cell apoptosis may be a successful strategy to eliminate pathogens and assure host survival. Conversely, apoptosis inhibition could represent an adaptive mechanism for pathogen survival, while it may be beneficial for the host to initiate an effective immune response. The worldwide increase in tuberculosis has stimulated more research aimed at defining the interaction between Mycobacterium tuberculosis and the immune system. M. tuberculosis possesses sophisticated strategies to circumvent its fate within target monocytic cells. Apoptosis of alveolar macrophages and monocytes has been described as a consequence of M. tuberculosis infection. Moreover, the observation that mycobacterial lipoproteins activate macrophages through Toll-like receptor (TLR) 2 suggests that innate immune receptors contribute to defence against M. tuberculosis. There is evidence that TLR-induced apoptosis modulates inflammation and immune activation during M. tuberculosis infection. Finally, the role of apoptotic-infected cells as a source of microbial antigens for cross-priming of effector T-cells is also discussed.

Induction of Apoptosis and Release of Interleukin‐1β by Cell Wall–Associated 19‐kDa Lipoprotein during the Course of Mycobacterial Infection

Mycobacterium tuberculosis induces apoptosis in human monocyte-derived macrophages (MDMs) during the early stages of infection. We investigated the proapoptotic role of cell wall-associated mycobacterial 19-kDa lipoprotein and the possible association between 19-kDa lipoprotein signaling and production of proinflammatory cytokines. Purified mycobacterial 19-kDa lipoprotein, 19-kDa lipoprotein-expressing M. smegmatis (M. smegmatis 19+), 19-kDa lipoprotein knockout (KO) M. tuberculosis, and 19-kDa lipoprotein KO M. bovis bacille Calmette-Guerin (BCG) strains were analyzed for their ability to induce apoptosis in MDMs. The 19-kDa lipoprotein and infection with M. smegmatis 19+ induced apoptosis in MDMs. M. tuberculosis and BCG KO strains had significantly decreased abilities to induce apoptosis. The 19-kDa lipoprotein proapoptotic signal was mediated by Toll-like receptor 2 but not by tumor necrosis factor-alpha. Only the release of interleukin (IL)-1 beta was decreased after infection with 19-kDa lipoprotein KO strains. These findings indicate that the 19-kDa lipoprotein is the main signal required to trigger both apoptosis and the release of IL-1 beta during the early stages of mycobacterial infection.

Difficult diagnosis of Infliximab-related miliary tuberculosis

The use of Infliximab in the treatment of patients with rheumatoid diseases unresponsive to conventional therapies has been reported to be complicated by opportunistic infections. We report the case of a 56-yr old female rheumatoid arthritis patient complaining of fever and respiratory symptoms 9 months after commencing Infliximab, who received no ethiologic diagnosis for the six months before admission. Tuberculosis was suspected upon chest radiographic pictures and empirical treatment for miliary tuberculosis instated in the wake of microbiological confirmation. The case typifies the difficulties of diagnosing miliary tuberculosis in the immunocompromised as well as in the immunocompetent patient.

Specific changes in the posttranslational regulation of nucleolin in lymphocytes from patients infected with human immunodeficiency virus

Lymphocytes isolated from human immunodeficiency virus (HIV)-infected patients have dysregulated cell-cycle control, consisting of increased activation of the cyclin B1/p34 cdc2 complex and abnormal nucleolar structure. To better characterize the molecular features of the HIV-associated cell-cycle perturbations, we performed a detailed analysis of the posttranslational regulation of nucleolin, a key structural protein in the nucleolus. We found that, in concanavalin A-stimulated lymphocytes from HIV-infected patients, the inappropriate activation of the cyclin B1/p34 cdc2 kinase complex is temporally associated with increased threonine phosphorylation, augmented fragmentation, and prominent extranuclear and cell-surface localization of nucleolin. Importantly, increased lymphocyte apoptosis is observed at the time of cell-surface localization of nucleolin. These results may delineate a direct molecular link between abnormal activation of cyclin B1/p34 cdc2 and the changes in the nucleolar structure, thus providing a better molecular definition of HIV-associated cell-cycle dysregulation.

Cell cycle dysregulation during HIV infection: perspectives of a target based therapy

Human immunodeficiency virus (HIV) infection is characterized by a severe depletion of both CD4+ and CD8+ T cells, representing the result of virus-mediated killing of infected lymphocytes and the programmed cell death (apoptosis) of the uninfected bystander cells. Since only a small fraction of T lymphocytes are depleted by viral killing, apoptosis represents one of the most important mechanism of T cell death during HIV infection. Several apoptotic pathways can be triggered by the different stimuli: persistent T lymphocyte activation; altered death receptor (Fas, TNF-R, TRAIL R1-R2) membrane expression; viral proteins as well as gp120, Tat, and Nef; host factors such as the unbalance of cytokine synthesis by lymphocyte. Nevertheless, new evidences have demonstrated that the persistent HIV induced T cell activation and proliferation cause a cell cycle dysregulation resulting in a 5-fold increase in apoptotic cells. This perturbation represents a link between HIV infection, T cell activation, accelerated cell turnover and increased apoptosis and may thus represent a new therapeutic target. In fact, Interleukin-2 administration reverts such a cell cycle dysregulation and reduces activation induced T cell apoptosis. Herein we analyze the main HIV-related mechanisms of host cell death, that are dysregulation of the cell cycle and apoptosis induction of T lymphocytes. Finally, the role of cytokines at the site of infection and their association with apoptosis will be discussed to get insights into the immunological perturbations accounting for an accelerated disease progression. Current therapeutic approaches and strategies, like HAART and recombinant cytokines, that may, successfully, improve the immune-system dysregulation, are also discussed.

Demographic risk factors and lymphocyte populations in patients with tuberculosis and their healthy contacts

SETTING

Campania, a southern region of Italy, and the Institute of Respiratory Diseases, Monaldi Hospital, University 'Federico II', Naples.

OBJECTIVE

To evaluate clinical and socio-demographic risk factors for tuberculosis (TB) infection and/or disease. Peripheral blood lymphocytes from a sub-cohort of 19 patients and 53 contacts were studied by flow cytometry.

DESIGN

A prospective study among patients with newly diagnosed pulmonary tuberculosis and their close contacts.

RESULTS

A total of 90 patients and 277 contacts were enrolled. The prevalence of infection was 45% (95%CI 39-51%) among contacts. Age, sex, delay in diagnosis and treatment, cavitation on chest radiograph, cough, unwillingness to cover the mouth, and volume of air shared by close contacts and patients were investigated as potential risk factors for infection. Only delay in diagnosis of cases remained independently associated with an increased risk of infection (P < 0.0002), and hemoptysis was the only factor capable of reducing the delay significantly. The CD8+ CD28+ cytotoxic subset was significantly diminished in the patients (P < 0.001), whereas the CD8+ CD28- and CD8+ CD57+ (suppressor and NK-like subsets) were elevated (P < 0.001 and P = 0.04).

CONCLUSIONS

These data show that delay in diagnosis of cases is a crucial factor for tuberculosis and that cytotoxic CD8+ cells play a primary role in immune response to tuberculosis.

Increased priming for interleukin-12 and tumour necrosis factor alpha in CD64 monocytes in HIV infection: modulation by cytokines and therapy

BACKGROUND

A key factor leading to impaired immunity in HIV infection is an alteration of the pattern of cytokine response, although its precise nature remains controversial, particularly the in vivo influence of HIV on interleukin (IL)-12 synthesis.

DESIGN

A cross-sectional study in 73 HIV-infected persons (28 of them receiving highly active antiretroviral therapy) and 18 HIV-seronegative healthy donors.

METHODS

The frequency of monocytes/macrophages (M/M) synthesizing IL-12, IL-10 and tumour necrosis factor alpha (TNF-alpha) was determined in peripheral blood mononuclear cells. The cells were cultured in medium or were stimulated with lipopolysaccharide; proportions of CD64 M/M producing IL-12, TNF-alpha or IL-10 was determined by cytofluorometric analysis. The influence of exogenous interferon gamma (IFN-gamma), IL-10 or IL-15 on IL-12 synthesis was tested.

RESULTS

Chronic HIV disease is associated with increased priming of M/M for IL-12 (involving both p40 and p70 molecules) and TNF-alpha synthesis; this was associated with cosynthesis of both cytokines by a fraction of M/M. Priming for IL-12 was physiologically enhanced by IFN-gamma and decreased by IL-10; IL-15 had no effect. The proportion of IL-10-producing CD64 M/M was not altered in patients compared with controls but there was an inverse correlation between IL-10-producing M/M and viral load. IL-12 production was not correlated with viral load but was increased following antiretroviral therapy. Following LPS stimulation, IL-12 and TNF-alpha responses were not altered in HIV-positive patients; however, the IL-10 response was decreased but restored by antiretroviral therapy.

CONCLUSION

These observations argue for a preserved intrinsic CD64 M/M of IL-12 production in HIV pathogenesis.

HIV, cytokines and programmed cell death. A subtle interplay

HIV infection is marked by the progressive destruction of the CD4 T lymphocyte subset, an essential component of the immune system and a vital source of cytokines required for differentiation of natural killer (NK) and gamma delta T cells, for maturation of B lymphocytes into plasmocytes, and for differentiation of CD8+ T cells into virus-specific cytotoxic T lymphocytes. CD4 T lymphocytes are also a source of chemokines which control migration of lymphocytes to the site of infection and which also inhibit HIV entry into CD4-expressing targets. Continuous production of viral proteins leads to an unbalanced immune activation and to the triggering of apoptotic programs, turning mononuclear cells, including CD4 T cells, CD8 T cells and APC, into effectors of apoptosis, leading to fratricidal destruction of healthy uninfected cells expressing the death receptors. Inappropriate PCD is also responsible for the disappearance of T helper cells primed for type-1 cytokine synthesis, thus contributing to the lack of survival factors which could prevent spontaneous lymphocyte apoptosis. Under potent anti-retroviral therapies, a significant decrease in spontaneous, TCR- and CD95-induced lymphocyte apoptosis is observed, concomitant with a partial quantitative and qualitative restoration of the immune system in treated patients. However, owing to the suppressive effect of anti-retroviral drugs on physiological apoptosis, these therapies are associated with alteration of TNF-alpha-regulated T cell homeostasis, leading to an accumulation in the blood of T cells primed for TNF-alpha synthesis, and contributing to the development of a new syndrome associated with these treatments, the lipodystrophy syndrome.

Tuberculosis and lung cancer. An interesting case study

This report describes the case of a patient with lung cancer who completely recovered when he was suffering from tuberculosis. Since bacillus Calmette-Guerin (BCG) has beneficial effects in certain types of cancer, it was hypothesized that infection with Mycobacterium tuberculosis induced an effective response against the tumour. M. tuberculosis-infected blood T-lymphocytes of the patient were cultured with two lung tumour cell lines. T-lymphocytes in vitro remained attached to tumour cells that appeared reduced in number. Moreover, M. tuberculosis isolated from the patient was a strong inducer, in infected macrophages, of the expression of the inducible form of the nitric oxide synthase, that may regulate cytotoxic activity of human macrophages.

Mycobacterium tuberculosis and HIV co-infection in the lung: synergic immune dysregulation leading to disease progression

There is evidence that Mycobacterium tuberculosis (Mtb) impacts on human immunodeficiency virus (HIV) infection and that HIV promotes mycobacterial diseases. Epidemiological and clinical studies demonstrate the detrimental effect of tuberculosis (TB) on the progression of HIV infection, that is an increased risk of death among Mtb-HIV co-infected patients. Pulmonary TB may occur very early during HIV infection, whereas extrapulmonary or atypical manifestations are associated with more profound immunodeficiency, showing features like mycobacteraemia and multi-drug resistance, much more severe than in immunocompetent hosts. During the last decade, many efforts have been focused on the immunological aspects of Mtb-HIV co-infection. The host protective response to TB is mediated by cell immunity, which, mainly supported by interleukin (IL)-12 and interferon (IFN)-gamma production, leads to granuloma formation. Perturbations in the cytokine expression, that is a reduced type-1-like response, have been suggested in HIV-infected patients to contribute to their susceptibility to TB. Indeed, an impaired balance between pro-inflammatory and anti-inflammatory cytokines and apoptosis-induced depletion of immune effector cells account for the dissemination of both the pathogens and for a poor granulomatous reaction in Mtb-HIV co-infected patients. However, the recently elucidated role of chemokines and their receptors in immune regulation opens new questions on the pathogenesis of Mtb-HIV co-infection.