Henrique Couto Teixeira

T-Cell Responses to the Mycobacterium tuberculosis-Specific Antigen ESAT-6 in Brazilian Tuberculosis Patients

ABSTRACT The Mycobacterium tuberculosis-specific ESAT-6 antigen induces highly potent T-cell responses and production of gamma interferon (IFN-γ), which play a critical role in protective cell-mediated immunity against tuberculosis (TB). In the present study, IFN-γ secretion by peripheral blood mononuclear cells (PBMCs) in response to M. tuberculosis ESAT-6 in Brazilian TB patients was investigated in relation to clinical disease types, such as pleurisy and cavitary pulmonary TB. Leprosy patients, patients with pulmonary diseases other than TB, and healthy donors were assayed as control groups. Sixty percent of the TB patients indeed recognized M. tuberculosis ESAT-6, as did 50% of the leprosy patients and 60% of the non-TB controls. Nevertheless, the levels of IFN-γ in response to the antigen ESAT, but not to antigen 85B (Ag85B) and purified protein derivative (PPD), were significantly lower in controls than in patients with treated TB or pleural or cavitary TB. Moreover, according to Mycobacterium bovis BCG vaccination status, only 59% of the vaccinated TB patients responded to ESAT in vitro, whereas 100% of them responded to PPD. Both CD4 and CD8 T cells were able to release IFN-γ in response to ESAT. The present data demonstrate the specificity of ESAT-6 of M. tuberculosis and its ability to discriminate TB patients from controls, including leprosy patients. However, to obtain specificity, it is necessary to include quantitative IFN-γ production in response to the antigen as well, and this might limit the use of ESAT-6-based immunodiagnosis of M. tuberculosis infection in an area of TB endemicity.

Increased IgG1, IFN-γ, TNF-α and IL-6 responses to Mycobacterium tuberculosis antigens in patients with Tuberculosis are lower after chemotherapy

Detection of specific antibodies may represent an additional tool in diagnosis of tuberculosis (TB). Herein, levels of serum IgG antibodies against early secreted antigenic target (ESAT-6), culture filtrate antigen-10 (CFP-10) and 16 kDa Mycobacterium tuberculosis antigens were measured in 33 active pulmonary TB patients (0M-TB), in 47 patients after 1-3 months of treatment (3M-TB) and in 22 patients who had completed 6 months of chemotherapy (6M-TB). The control group consisted of 38 BCG-vaccinated healthy controls (HC). In addition, IFN-gamma, tumor necrosis factor (TNF)-alpha, IL-6, IL-2, IL-4 and IL-10 production in PBMC cultures from 20 patients were measured following stimulation with the M. tuberculosis-specific fusion protein ESAT-6/CFP-10. Elevated levels of IgG against ESAT-6, CFP-10 and 16 kDa antigens were detected in 0M-TB and 3M-TB patients in comparison to the HC and 6M-TB groups. Receiver operating characteristic analysis indicated sensitivity of 85, 94 and 61% and specificity of 89, 87 and 89% for serum IgG against ESAT-6, CFP-10 and 16 kDa, respectively. A predominant IgG1 response to ESAT-6 and CFP-10 was observed in 0M-TB patients, together with ESAT-6/CFP-10-specific IFN-gamma, TNF-alpha and IL-6 that were produced at lower levels in the 6M-TB group. These data indicate that a T(h)1 phenotype against early phase Mtb antigens appears to be dominant in the peripheral blood of patients with active pulmonary TB that is reduced after chemotherapy. Taken together, ESAT-6/CFP-10 cytokine tests together with detecting IgG antibodies specific to ESAT-6 and CFP-10 may be the useful TB disease biomarkers in monitoring treatment success.

Diagnóstico imunológico da tuberculose: problemas e estratégias para o sucesso

Tuberculosis remains a serious social and public health problem, affecting millions of people annually. The bacille Calmette-Guerin (BCG) vaccine, used prophylactically, does not impede the progression of the disease, which usually manifests as decreased cellular immunity. Early diagnosis, together with polychemotherapy, can control the dissemination of the tuberculosis infection. The current diagnostic methods present certain problems. Such problems include the low sensitivity of sputum smear microscopy, the fact that performing microbiological cultures is quite time-consuming, and the low specificity of the skin test with the purified protein derivative of M. tuberculosis. New diagnostic methods, which use specific antigens such as the early secreted antigenic target 6-kDa and culture filtrate protein 10kDa, are being evaluated. The genes that encode these antigens are located in the DNA region of difference 1 of M. tuberculosis, M. africanum and M. bovis. However, they are absent from the M. bovis (BCG) and from most environmental mycobacteria. Diagnostic methods such as QuantiFERON-TB(R) and T SPOT.TB(R), which are based on the production of interferon-gamma by T lymphocytes, in response to those antigens, are being tested and have been found to outstrip the purified protein derivative skin test in the following characteristics: greater sensitivity; lower cross-reactivity due to BCG vaccination or infection with environmental mycobacteria; and execution time. The introduction of diagnostic methods that are more specific and sensitive, together with gaining a better understanding of the molecular and cellular mechanisms that regulate the parasite-host interaction, can increase the efficiency of strategies devised to combat tuberculosis.

Genistein down-modulates pro-inflammatory cytokines and reverses clinical signs of experimental autoimmune encephalomyelitis.

Multiple sclerosis (MS) is the most common non-traumatic, disabling neurological human inflammatory demyelinating disease of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) models MS and is characterized as a CD4+ T-helper type 1 (Th1) cell-mediated autoimmune disease. It is characterized by an influx of activated leukocytes into the CNS. Genistein, occurring abundantly in soy products, has apoptotic, antioxidant, and anti-inflammatory properties. In the present report, we investigated the use of genistein for the treatment of the murine model of MS. After induction of EAE with myelin oligodendrocyte glycoprotein 35-55 peptide (MOG(35-55)), we observed that genistein treatment ameliorated significantly the clinical symptoms, modulating pro- and anti-inflammatory cytokines. Moreover, we analyzed the leukocyte rolling and adherence in the CNS by performing intravital microscopy. Genistein treatment resulted in decreased rolling and adhering of leukocytes as compared to the untreated group. Our data suggest that genistein might be a potential therapy for MS.

Lack of Endogenous IL-10 Enhances Production of Proinflammatory Cytokines and Leads to Brucella abortus Clearance in Mice

IL-10 is a cytokine that regulates the balance between pathogen clearance and immunopathology. Brucella abortus is an intracellular bacterium that causes chronic disease in humans and domestic animals. Here we evaluated the contribution of IL-10 in host immune response and pathology during B. abortus infection. To assess the role of IL-10 in vivo, IL-10 knockout (KO) or 129 Sv/Ev (wild-type) mice were infected with B. abortus and the number of viable bacteria from the spleen was determined at 1, 2, 3, 6 and 14-weeks postinfection. IL-10 KO mice showed reduced bacterial loads in the spleen when compared to wild-type mice during all time points studied. Additionally, at 14-weeks postinfection IL-10 KO mice had totally cleared the infection. This clearance was preceded by an enhanced IFN-γ, TNF-α and IL-17 responses in both the serum and the spleen of IL-10 KO mice. Additionally, dendritic cells from infected IL-10 KO mice produced elevated levels of IL-12 and TNF-α compared to wild-type animals. Histopathology analysis was performed and both KO and wild-type mice developed multifocal granulomas and necrosis in the liver. However, at six-weeks postinfection reduced numbers of granulomas was detected in IL-10 KO mice compared to wild-type animals. This reduced liver pathology at later stage of infection was accompanied by increased numbers of CD4+CD25+foxp3+ T cells and expression of TGF-β in IL-10 KO splenocytes. Taken together, our findings demonstrate that IL-10 modulates the proinflammatory immune response to B. abortus infection and the lack of IL-10 increases resistance to Brucella infection.

Splenectomy Increases Atherosclerotic Lesions in Apolipoprotein E Deficient Mice

BACKGROUND Atherosclerosis is an inflammatory immune disease associated with lipid accumulation in the intima layer of arteries. The spleen plays an important immune function, but its influence in development of atherosclerosis remains unclear. Evaluation of the role of the spleen in atherosclerosis is justified due to the high frequency of total splenectomies. In this work, the effect of splenectomy on the development of atherosclerosis in apolipoprotein E (ApoE) deficient mice was investigated. METHODS ApoE deficient mice were divided into a sham-operated control group (CT) and a splenectomized group (SP). Thirty days after surgery, animals were fed a high fat western diet. After 8 wk, mice were euthanized and their blood, heart, and aorta were subjected to analysis. Atherosclerotic lesion areas in the aortic root were stained with hematoxylin-eosin and quantified by morphometry. The atherosclerotic lesions in the thoracic and abdominal portions of aorta were determined by assessing the percentage of the luminal surface area stained by Sudan IV. Total serum cholesterol and anti-oxidized LDL antibodies were measured. RESULTS Levels of total serum cholesterol did not vary significantly after splenectomy. Anti-oxidized LDL IgG antibodies were similar between groups. However, compared with the control group, lesions in the aortic root were significantly larger in splenectomized mice (P<0.01). These data were confirmed by the increase of atherosclerotic area in the thoracic and abdominal portions of aorta in splenectomized mice. CONCLUSIONS These data indicate that splenectomy increases atherosclerotic lesions in ApoE deficient mice fed an atherogenic diet, suggesting an atheroprotector role of the spleen.

Human T Cell and Antibody-Mediated Responses to the Mycobacterium tuberculosis Recombinant 85A, 85B, and ESAT-6 Antigens

Tuberculosis remains a major health problem throughout the world causing large number of deaths. Effective disease control and eradication programs require the identification of major antigens recognized by the protective responses against M. tuberculosis. In this study, we have investigated humoral and cellular immune responses to M. tuberculosis-specific Ag85A, Ag85B, and ESAT-6 antigens in Brazilian patients with pulmonary (P, n = 13) or extrapulmonary (EP, n = 12) tuberculosis, patients undergoing chemotherapy (PT, n = 23), and noninfected healthy individuals (NI, n = 7). Compared to NI, we observed increased levels of IgG1 responses to Ag85B and ESAT-6 in P and PT groups. Regarding cellular immunity, Ag85A and ESAT-6 were able to discriminate P, PT, and EP patients from healthy individuals by IFN-γ production and P and PT groups from EP individuals by production of TNF-α. In summary, these findings demonstrate the ability of Ag85A, Ag85B, and ESAT-6 to differentiate TB patients from controls by IgG1, IFN-γ and TNF-α production.

Apoptosis of macrophages during pulmonary Mycobacterium bovis infection: correlation with intracellular bacillary load and cytokine levels

Apoptosis of macrophages infected with pathogenic mycobacteria is an alternative host defence capable of removing the environment supporting bacterial growth. In this work the influence of virulence and bacterial load on apoptosis of alveolar macrophages during the initial phase of infection by Mycobacterium bovis was investigated. BALB/c mice were infected intratracheally with high or low doses of the virulent (ATCC19274) or attenuated (bacillus Calmette–Guérin Moreau) strains of M. bovis. The frequency of macrophage apoptosis, the growth of mycobacteria in macrophages, and the in situ levels of the cytokines tumour necrosis factor‐α (TNF‐α), interleukin‐10 (IL‐10) and IL‐12 and of the anti‐apoptotic protein Bcl‐2 were measured at day 3 and day 7 post‐infection. An increase of macrophage apoptosis was observed after infection with both strains but the virulent strain induced less apoptosis than the attenuated strain. On the 3rd day after infection with the virulent strain macrophage apoptosis was reduced in the high‐dose group, while on the 7th day post‐infection macrophage apoptosis was reduced in the low‐dose group. Inhibition of apoptosis was correlated with increased production of IL‐10, reduced production of TNF‐α and increased production of Bcl‐2. In addition, the production of IL‐12 was reduced at points where the lowest levels of macrophage apoptosis were observed. Our results indicate that virulent mycobacteria are able to modulate macrophage apoptosis to an extent dependent on the intracellular bacterial burden, which benefits its intracellular growth and dissemination to adjacent cells.

DNA Vaccine Using Mycobacterium bovis Ag85B Antigen Induces Partial Protection against Experimental Infection in BALB/c Mice

ABSTRACT Bovine tuberculosis is a major cause of economic loss in countries where it is endemic, and in some countries, it may be a significant zoonotic disease problem. Therefore, new strategies for vaccine development are required, and among them, genetic immunization has potential value. The main goal of this study was to test the Mycobacterium bovis Ag85B gene as a DNA vaccine following challenge with an M. bovis virulent strain (ATCC 19274). Groups of BALB/c mice (n = 10) were immunized four times intramuscularly with the pCI-Ag85B construct or the pCI vector alone as the control. High titers of total immunoglobulin G (IgG), IgG1, and IgG2a anti-Ag85B were measured in pCI-Ag85B immunized mice when compared to the pCI control group. Regarding cellular immunity, significant levels of gamma interferon (IFN-γ) (1,100 ± 157 pg/ml) and tumor necrosis factor alpha (650 ± 42 pg/ml) but not interleukin-4 were detected in splenocyte culture supernatants of pCI-Ag85B-vaccinated mice following stimulation with recombinant Ag85B. Further, the main source of IFN-γ is CD8+ T cells, as demonstrated by intracellular cytokine staining. As far as protection, a significant reduction in bacterial load in spleens (P < 0.05) was detected in pCI-Ag85B-immunized mice compared to the pCI vector control group. The results obtained here suggest that use of the Ag85B DNA vaccine is a promising strategy to control M. bovis infection due to its ability to induce a Th1 type of immune response. However, protective efficacy needs to be improved, since partial protection was achieved in spleens but not in lungs of vaccinated mice.

Immunomodulatory effects and improved prognosis of experimental autoimmune encephalomyelitis after O-tetradecanoyl-genistein treatment

Experimental autoimmune encephalomyelitis (EAE) is a murine autoimmune disease used to study multiple sclerosis (MS), a human inflammatory demyelinating disease of the central nervous system. Genistein, an isoflavonoid phytoestrogenic compound found in soy, is known to reverse clinical signs of EAE. Although genistein has some potential in clinical application, it has some disadvantages related to its chemical structure, such as rapid in vivo metabolism and a fast decline in serum after oral administration. The present work investigates the treatment of EAE by using 7-O-tetradecanoyl-genistein (TDG), a more lipophilic analog of genistein obtained by esterification. The clinical course of EAE was investigated in C57Bl/6 mice immunized with myelin oligodendrocyte glycoprotein peptide (MOG)(35-55) in complete Freunds adjuvant supplemented with Mycobacterium tuberculosis H37RA. After 14 days of MOG immunization, mice were treated with TDG for seven days. Numbers of IL-17-producing cells and Foxp3 by CD4(+) T cells and CTLA-4 expression by CD3(+) T cells from brain were determined by flow cytometry. Levels of IL-6, IFN-γ and IL-10 were evaluated by ELISA. Brain sections were stained by hematoxylin and eosin method. The data obtained indicate that TDG treatment ameliorates the clinical signs of EAE, which correlates with a decrease of IL-17-producing cells and an increase in Foxp3(+)CD4(+) cells in the brain. TDG is also shown to enhance IL-10 production and CTLA-4 expression and to reduce IFN-γ and IL-6. Altogether, these findings suggest an immunomodulatory therapeutic role for TDG in EAE and multiple sclerosis.