Eosinophils in bronchial mucosa of asthmatics after allergen challenge: effect of anti-IgE treatment

Anti-IgE, omalizumab, inhibits the allergen response in patients with asthma. This has not been directly related to changes in inflammatory conditions. We hypothesized that anti-IgE exerts its effects by reducing airway inflammation. To that end, the effect of anti-IgE on allergen-induced inflammation in bronchial biopsies in 25 patients with asthma was investigated in a randomized, double-blind, placebo-controlled study. Allergen challenge followed by a bronchoscopy at 24 h was performed at baseline and after 12 weeks of treatment with anti-IgE or placebo. Provocative concentration that causes a 20% fall in forced expiratory volume in 1 s (PC(20)) methacholine and induced sputum was performed at baseline, 8 and 12 weeks of treatment. Changes in the early and late responses to allergen, PC(20), inflammatory cells in biopsies and sputum were assessed. Both the early and late asthmatic responses were suppressed to 15.3% and 4.7% following anti-IgE treatment as compared with placebo (P < 0.002). This was paralleled by a decrease in eosinophil counts in sputum (4-0.5%) and postallergen biopsies (15-2 cells/0.1 mm(2)) (P < 0.03). Furthermore, biopsy IgE+ cells were significantly reduced between both the groups, whereas high-affinity IgE receptor and CD4+ cells were decreased within the anti-IgE group. There were no significant differences for PC(20) methacholine. The response to inhaled allergen in asthma is diminished by anti-IgE, which in bronchial mucosa is paralleled by a reduction in eosinophils and a decline in IgE-bearing cells postallergen without changing PC(20) methacholine. This suggests that the benefits of anti-IgE in asthma may be explained by a decrease in eosinophilic inflammation and IgE-bearing cells.

Leukotriene B(4) is essential for selective eosinophil recruitment following allergen challenge of CD4(+) cells in a model of chronic eosinophilic inflammation

Subcutaneous heat-coagulated egg white implants (EWI) induce chronic, intense local eosinophilia in mice, followed by asthma-like responses to airway ovalbumin challenge. Our goal was to define the mechanisms of selective eosinophil accumulation in the EWI model. EWI carriers were challenged i.p. with ovalbumin and the contributions of cellular immunity and inflammatory mediators to the resulting leukocyte accumulation were defined through cell transfer and pharmacological inhibition protocols. Eosinophil recruitment required Major Histocompatibility Complex Class It expression, and was abolished by the leukotriene B4 (LTB4) receptor antagonist CP 105.696, the 5-lipoxygenase inhibitor BWA4C and the 5-lipoxygenase activating protein inhibitor MK886. Eosinophil recruitment in EWI carriers followed transfer of: a) CD4(+) (but not CD4(-)) cells, harvested from EWI donors and restimulated ex vivo; b) their cell-free supernatants, containing LTB4. Restimulation in the presence of MK886 was ineffective. CC chemokine receptor ligand (CCL)5 and CCL2 were induced by ovalbumin challenge in vivo. mRNA for CCL17 and CCL11 was induced in ovalbumin-restimulated CD4(+) cells ex vivo. MK886 blocked induction of CCL17 Pretreatment of EWI carriers with MK886 eliminated the effectiveness of exogenously administered CCL11, CCL2 and CCL5. In conclusion, chemokine-producing, ovalburnin-restimulated CD4(+) cells initiate eosinophil recruitment which is strictly dependent on LTB4 production. (C) 2008 Elsevier Inc. All rights reserved.

Leukotriene B(4) is essential for selective eosinophil recruitment following allergen challenge of CD4(+) cells in a model of chronic eosinophilic inflammation

Subcutaneous heat-coagulated egg white implants (EWI) induce chronic, intense local eosinophilia in mice, followed by asthma-like responses to airway ovalbumin challenge. Our goal was to define the mechanisms of selective eosinophil accumulation in the EWI model. EWI carriers were challenged i.p. with ovalbumin and the contributions of cellular immunity and inflammatory mediators to the resulting leukocyte accumulation were defined through cell transfer and pharmacological inhibition protocols. Eosinophil recruitment required Major Histocompatibility Complex Class It expression, and was abolished by the leukotriene B4 (LTB4) receptor antagonist CP 105.696, the 5-lipoxygenase inhibitor BWA4C and the 5-lipoxygenase activating protein inhibitor MK886. Eosinophil recruitment in EWI carriers followed transfer of: a) CD4(+) (but not CD4(-)) cells, harvested from EWI donors and restimulated ex vivo; b) their cell-free supernatants, containing LTB4. Restimulation in the presence of MK886 was ineffective. CC chemokine receptor ligand (CCL)5 and CCL2 were induced by ovalbumin challenge in vivo. mRNA for CCL17 and CCL11 was induced in ovalbumin-restimulated CD4(+) cells ex vivo. MK886 blocked induction of CCL17 Pretreatment of EWI carriers with MK886 eliminated the effectiveness of exogenously administered CCL11, CCL2 and CCL5. In conclusion, chemokine-producing, ovalburnin-restimulated CD4(+) cells initiate eosinophil recruitment which is strictly dependent on LTB4 production. (C) 2008 Elsevier B.V. All rights reserved.

PPAR-gamma agonists, mainly 15d-PGJ(2), reduce eosinophil recruitment following allergen challenge

We evaluate the immunomodulation of Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists 15d-PGJ(2) and rosiglitazone (RGZ) in a model of chronic eosinophilia. 15d-PGJ(2) and RGZ significantly reduce eosinophil migration into the peritoneal cavity and down-regulate the eosinopoiesis. The synthesis of IL-5 was decreased after the treatment with 15d-PGJ(2) and RGZ corroborating with the eosinophil migration inhibition. However, IgE was decreased only after the administration of 15d-PGJ(2) in part due to B-cell inhibition. We also observed a decrease in the synthesis of IL-33, IL-17 and IL-23, suggesting that besides the modulation of Th2 pattern, there is a modulation via IL-23 and IL-17 suggesting a role of these cytokines in the eosinophil recruitment. In fact IL-17(-1-) mice failed to develop an eosinophilic response. Altogether, the results showed that PPAR-gamma agonists mainly 15d-PGJ(2), have therapeutic efficacy in eosinophil-induced diseases with an alternative mechanism of control, via IL-23/IL-17 and IL-33. (C) 2011 Elsevier Inc. All rights reserved.

Allergen-induced IgE-dependent gut inflammation in a human PBMC-engrafted murine model of allergy.

BACKGROUND: Humanized murine models comprise a new tool to analyze novel therapeutic strategies for allergic diseases of the intestine.¦OBJECTIVE: In this study we developed a human PBMC-engrafted murine model of allergen-driven gut inflammation and analyzed the underlying immunologic mechanisms.¦METHODS: Nonobese diabetic (NOD)-scid-γc(-/-) mice were injected intraperitoneally with human PBMCs from allergic donors together with the respective allergen or not. Three weeks later, mice were challenged with the allergen orally or rectally, and gut inflammation was monitored with a high-resolution video miniendoscopic system, as well as histologically.¦RESULTS: Using the aeroallergens birch or grass pollen as model allergens and, for some donors, also hazelnut allergen, we show that allergen-specific human IgE in murine sera and allergen-specific proliferation and cytokine production of human CD4(+) T cells recovered from spleens after 3 weeks could only be measured in mice treated with PBMCs plus allergen. Importantly, these mice had the highest endoscopic scores evaluating translucent structure, granularity, fibrin, vascularity, and stool after oral or rectal allergen challenge and a strong histologic inflammation of the colon. Analyzing the underlying mechanisms, we demonstrate that allergen-associated colitis was dependent on IgE, human IgE receptor-expressing effector cells, and the mediators histamine and platelet-activating factor.¦CONCLUSION: These results demonstrate that allergic gut inflammation can be induced in human PBMC-engrafted mice, allowing the investigation of pathophysiologic mechanisms of allergic diseases of the intestine and evaluation of therapeutic interventions.

Neurokinin-1 receptor, a new modulator of lymphangiogenesis in obese-asthma phenotype

Aims Obesity and asthma are widely prevalent and associated disorders. Recent studies of our group revealed that Substance P (SP) is involved in pathophysiology of obese-asthma phenotype in mice through its selective NK1 receptor (NK1-R). Lymphangiogenesis is impaired in asthma and obesity, and SP activates contractile and inflammatory pathways in lymphatics. Our aim was to study whether NK1-R expression was involved in lymphangiogenesis on visceral (VAT) and subcutaneous (SAT) adipose tissues and in the lungs, in obese-allergen sensitized mice. Main methods Diet-induced obese and ovalbumin (OVA)-sensitized Balb/c mice were treated with a selective NK1-R antagonist (CJ 12,255, Pfizer Inc., USA) or placebo. Lymphatic structures (LYVE-1 +) and NK1-R expression were analyzed by immunohistochemistry. A semi-quantitative score methodology was used for NK1-R expression. Key findings Obesity and allergen-sensitization together increased the number of LYVE-1 + lymphatics in VAT and decreased it in SAT and lungs. NK1-R was mainly expressed on adipocyte membranes of VAT, blood vessel areas of SAT, and in lung epithelium. Obesity and allergen-sensitization combined increased the expression of NK1-R in VAT, SAT and lungs. NK1-R antagonist treatment reversed the effects observed in lymphangiogenesis in those tissues. Significance The obese-asthma phenotype in mice is accompanied by increased expression of NK1-R on adipose tissues and lung epithelium, reflecting that SP released during inflammation may act directly on these tissues. Blocking NK1-R affects lymphangiogenesis, implying a role of SP, with opposite physiological consequences in VAT, and in SAT and lungs. Our results provide a clue for a novel SP role in the obese-asthma phenotype.

Neurokinin-1 receptor, a new modulator of lymphangiogenesis in obese-asthma phenotype

Aims: Obesity and asthma are widely prevalent and associated disorders. Recent studies of our group revealed that Substance P (SP) is involved in pathophysiology of obese-asthma phenotype in mice through its selective NK1 receptor (NK1-R). Lymphangiogenesis is impaired in asthma and obesity, and SP activates contractile and inflammatory pathways in lymphatics. Our aim was to study whether NK1-R expression was involved in lymphangiogenesis on visceral (VAT) and subcutaneous (SAT) adipose tissues and in the lungs, in obeseallergen sensitized mice. Main methods: Diet-induced obese and ovalbumin (OVA)-sensitized Balb/c mice were treated with a selective NK1-R antagonist (CJ 12,255, Pfizer Inc., USA) or placebo. Lymphatic structures (LYVE-1+) and NK1-R expression were analyzed by immunohistochemistry. A semi-quantitative score methodology was used for NK1-R expression. Key findings: Obesity and allergen-sensitization together increased the number of LYVE-1+ lymphatics in VAT and decreased it in SAT and lungs. NK1-R was mainly expressed on adipocyte membranes of VAT, blood vessel areas of SAT, and in lung epithelium. Obesity and allergen-sensitization combined increased the expression of NK1-R in VAT, SAT and lungs. NK1-R antagonist treatment reversed the effects observed in lymphangiogenesis in those tissues. Significance: The obese-asthma phenotype in mice is accompanied by increased expression of NK1-R on adipose tissues and lung epithelium, reflecting that SP released during inflammation may act directly on these tissues. Blocking NK1-R affects lymphangiogenesis, implying a role of SP, with opposite physiological consequences in VAT, and in SAT and lungs. Our results provide a clue for a novel SP role in the obese-asthma phenotype.

Neutrophil defensins: their possible role in allergic asthma.

BACKGROUND Neutrophil defensins, originally identified as broad-spectrum antimicrobial peptides, have been implicated in the regulation of inflammatory and immunological processes. OBJECTIVES To investigate whether the in vitro challenge of neutrophils from patients with bronchial asthma with allergens stimulated the release of alpha-defensins and whether levels released were dependent on lung infections. METHOD The neutrophils were cultivated with different agonists and the concentration of alpha-defensin in cell-free supernatant was measured with enzyme-linked immunosorbent assay (ELISA). RESULTS Neutrophils from allergic patients released alpha-defensins via an allergen-dependent mechanism. Our results indicate that the in vitro activation of neutrophils is highly allergen-specific. In this context, allergens other than those which produced clinical symptoms did not elicit alpha-defensin release, and allergens had no effect on neutrophils from healthy donors. However, neutrophils from both allergic patients and healthy controls were able to release alpha-defensins upon treatment with PMA. In the allergen-stimulated neutrophils, cells from asthmatic patients stimulated with a sensitizing allergen showed a significantly higher production of alpha-defensin under respiratory tract infection than cells from the same patients without such an infection. CONCLUSION Neutrophils from allergic patients release alpha-defensins via an allergen-dependent mechanism.

Role of CD4+CD25+ regulatory T cells in the antigen specific induction of tolerance "via" the nasal route

ABSTRACT Asthma is a complex inflammatory syndrome caused by environmental factors in predisposed individuals (atopics). Its severity correlates with the presence of activated T lymphocytes and eosinophils in the bronchoalveolar lavage fluid (BALF). Induction of tolerance via the nasal route results in reduced recruitment of eosinophils into BALF upon challenge, inhibition of TH2 pro-inflammatory cytokine secretion and T cell hyporesponsiveness. Recently, CD4+CD25+ natural regulatory T cells (Treg) were proposed as key players in controlling the development of asthma and allergic disease. The objective of the present study is to investigate the role of CD4+CD25+ regulatory T cells in the mechanisms leading to tolerance in an established model of asthma. In this goal we depleted CD4+CD25+ T cells at different times during asthma and tolerance induction protocol in mice and looked at efficiency of tolerization (intranasal application of high dose of allergen) in the absence of natural Tregs. First, ovalbumin-sensitized mice were depleted of CD25+ T cells by intraperitoneal injection of anti-CD25 mAb (PC61) either for along-term (repeated injections of anti-CD25 from day 31 until the end of the protocol) or a short-term period (single injection of anti-CD25 before or after tolerance induction). We demonstrated that the long-term depletion of CD4+CD25+ T cells severely hampered tolerance induction (marked enhancement in eosinophil recruitment into BALF and a vigorous antigen specific T cell response to OVA upon allergen challenge) whereas transient depletions were not sufficient to do so. We then characterized T cell subsets by flow cytometry and observed that a large part of CD4+CD25+ T cells express Foxp3, an established marker of regulatory T cells. We also tested in-vitro suppressor activity of CD4+CD25+ T cells from tolerized mice by cell proliferation assay in coculture and observed a strong suppressive activity. Our data suggest that CD4+CD25+ T cells with regulatory properties play a crucial role in the induction of tolerance via the nasal route. The relationship between CD25+ natural Treg and inducible IL-10+ TRl-type Treg will have to be defined. RESUME L'asthme est un syndrome inflammatoire complexe provoqué par des facteurs environnementaux chez des individus génétiquement prédisposés (atopiques). Sa sévérité corrèle avec la présence des lymphocytes T activés et d'éosinophiles dans le lavage bronchoalvéolaire (BAL). L'induction de la tolérance par la voie nasale résulte en une diminution du recrutement des eosinophils dans le BAL, une inhibition de la sécrétion de cytokines pro-inflammatoires de type TH2 et de l'hypo-réponse des cellules T à l'allergène. Récemment, les cellules régulatrices «naturelles » de type CD4+CD25+ T (Tregs) ont été proposées comme acteurs essentiels dans le développement de l'asthme et de l'allergie. L'objectif de cette étude est d'étudier le rôle des cellules régulatrices CD4+CD25+ T dans les mécanismes menant à la tolérance dans un modèle établi d'asthme. Dans ce but nous avons déplété les cellules de CD4+CD25+ T à différents temps au cours du protocole d'induction d'asthme et de tolérance et nous avons regardé l'efficacité de l'induction de tolérance (application intranasale d'une dose importante d'allergène) en l'absence de Tregs. Dans un premier temps des souris sensibilisées à l'ovalbumine (OVA) ont été déplétées en cellules CD25+ T par l'injection intrapéritonéale d'anti-CD25 mAb (PC61) pour une longue période (injections répétées d'anti-CD25 du jour 31 jusqu'à la fin du protocole) ou pour une courte période (injection unique d'anti-CD25 avant ou après l'induction de tolérance). Nous avons démontré que la déplétion à long t erme des cellules de CD4+CD25+ T a empêché l'induction de tolérance (recrutement accru d'éosinophiles dans le BAL et une réponse vigoureuse des cellules T spécifiques de l'antigène après exposition à l'allergène) tandis des déplétions à court-terme n'ont pas cet effet. Nous avons ensuite caractérisé des sous-populations de cellules T par cytométrie de flux. Nous avons observé que la majorité des cellules CD4+CD25+ T expriment Foxp3, un marqueur établi des cellules régulatrices. Nous avons également examiné in vitro l'activité régulatrice des cellules T CD4+CD25+ issues de souris tolérisées. La prolifération de cellules T en coculture a démontré une forte activité suppressive des cellules CD4+CD25+. Nos données suggèrent que des cellules T CD4+CD25+ ayant des propriétés régulatrices jouent un rôle crucial dans l'induction de la tolérance par la voie nasale. Le rapport entre les cellules régulatrices naturelles CD4+CD25+ et les cellules régulatrices inductible de type TR1 I1-10+ devra être défini. RESUME DESTINE A UN LARGE PUBLIC L'asthme est une maladie inflammatoire des bronches, caractérisée par des crises de dyspnée (gêne respiratoire) témoignant d'une activation brutale des muscles bronchoconstricteurs, auxquelles s'associent un oedème et une hypersécrétion des muqueuses des voies aériennes ainsi qu'une importante production d'anticorps de l'allergie (IgE). Chez la plupart des enfants atteints et chez près de la moitié des adultes concernés par l'asthme, c'est une allergie à des substances présentes dans l'air environnant (acariens, pollens ou poils d'animaux) qui est à l'origine de la maladie. . Le traitement actuel de l'asthme repose d'une part sur le soulagement des symptômes grâce à des produits à base de stéroïdes ou des bronchodilatateurs. D'autre part, l'immunothérapie spécifique (aussi appelée désensibilisation) permet d'améliorer l'asthme et de «reprogrammer» le système immunitaire. C'est à ce jour, le seul moyen connu de faire régresser une allergie. Cependant l'immunothérapie prend beaucoup de temps (3 à 5 ans) et ne marche pas à tous les coups ni pour tous les antigènes. Il est donc important de mieux comprendre les mécanismes impliqués lors d'un tel traitement afin d'en améliorer l'efficacité. Af n de pouvoir investiguer en détail ces mécanismes des modèles d'immunothérapie ont été mis au point chez la souris. Notre étude se base sur un modèle d'asthme allergique chez la souris. Des souris sont rendues allergiques à l'ovalbumine (OVA) et présentent alors les caractéristiques majeures de l'asthme humain (recrutement de cellules inflammatoires dans les poumons, augmentation de la production d'IgE et de la résistance des bronches aux flux respiratoires). Ces souris asthmatiques une fois traitées par l'application nasale d'OVA (forme d'immunothérapie muqueuse) ne développent plus de réaction allergique lors d'une ré-exposition à l'allergène. Notre hypothèse est que cette «guérison» (tolérance) est liée à l'action de cellules (lymphocytes T CD4) dites «régulatrices» et caractérisées par le marqueur CD25. Pour le démontrer, nous avons éliminé ces cellules «régulatrices» CD25 de nos souris asthmatiques grâce à un anticorps monoclonal spécifique. Nous n'avons dès lors plus été en mesure d'induire une tolérance à l'allergène. Ceci suggère donc un rôle clé des cellules «régulatrices» T CD4+CD25+ dans la réussite de l'immunothérapie nasale dans notre modèle. Nos résultats n'excluent pas la participation d'autres cellules telles que les lymphocytes producteurs d'IL-10 (lymphocytes régulateurs induits). Le rôle respectif de ces sous-populations régulatrices devra être examiné dans les études à venir. Une meilleure maîtrise des mécanismes de régulation pourrait s'avérer cruciale pour améliorer les thérapies de l'asthme.

From pathogen defence to food allergy; The multiple facets of the mucosal immune system

Résumé destiné à un large public Le système immunitaire associé aux muqueuses gastro-intestinales doit être capable de protéger notre organisme contre l'invasion de pathogènes. Parallèlement, il doit identifier en Cant que tels, des composés inoffensifs comme la nourriture ou les milliards de bactéries qui résident dans notre intestin. Le travail présenté ici aborde ces deux aspects essentiels au bon fonctionnement de notre muqueuse intestinale. Dans une première partie, la protéine nommée pièce sécrétoire a été étudiée pour ses propriétés protectrices contre le pathogène viral rotavirus. Le rôle de la pièce sécrétoire est de transporter les anticorps que nous produisons vers la surface des muqueuses. En dehors de cette fonction bien connue, il se peut que cette protéine soit également capable de protéger notre organisme contre certains virus. L'hypothèse de travail était donc que la pièce sécrétoire se lie directement au virus, l'empêchant ainsi d'infecter des cellules épithéliales de l'intestin. En utilisant différentes techniques biochimiques, cette hypothèse s'est révélée fausse car aucune interaction entre la pièce sécrétoire et le virus n'a pu être observée, et logiquement, aucune protection n'a pu prendre place. En revanche, la pièce sécrétoire se lie à d'autres structures pathogéniques et permet ainsi de neutraliser leurs effets néfastes. La pièce sécrétoire participe donc activement à la protection de nos muqueuses, en plus de son rôle de transporteur. La deuxième partie de ce travail avait pour sujet les réactions inappropriées que le système immunitaire induit parfois contre un aliment, ou, autrement dit, les allergies alimentaires. Un modèle d'allergie alimentaire à donc été développé chez la souris et a permis de mesurer plusieurs symptômes et facteurs liés à l'allergie. Puis, ce modèle a été utilisé afin de tester les effets bénéfiques d'une bactérie lactique, dite probiotique, sur le développement de l'allergie. Il a été observé que, sous certaines circonstances, l'administration de la bactérie lactique protégeait entièrement les souris contre les réactions allergiques. L'effet bénéfique dépend donc du probiotique mais également d'autres facteurs encore inconnus â ce jour. Cette étude ouvre la voie sur la compréhension des mécanismes liés aux allergies alimentaires et sur l'impact que peuvent avoir les bactéries probiotiques sur cette maladie. Résumé Le système immunitaire associé aux muqueuses intestinales doit être capable de différencier les antigènes inoffensifs tels que 1a nourriture ou les bactéries commensales des microorganismes potentiellement dangereux. Cet aspect est essentiel pour le maintien de l'homéostase intestinale et fait l'objet du travail présenté ici. Dans un premier projet, les propriétés protectrices de la protéine appelée pièce sécrétoire (SC) ont été étudiées. SC est une protéine connue pour le transport des immunoglobulines à la surface des muqueuses. Cette protéine est fortement glycosylée paz des sucres complexes, ce qui nous a mené à postuler que SC puisse interagir avec le pathogène rotavirus. Cette hypothèse était soutenue par le fait que ce virus adhère aux cellules épithéliales par des résidus glycosylés. Des analyses biochimiques et biologiques ont démontré qu'aucune interaction entre SC et le virus ne prenait place, et que par conséquent SC n'offrait aucune protection contre ce pathogène. En revanche, SC interagit avec d'autres structures pathogéniques, comme la toxine A de Clostridium difficile, et la molécule d'adhésion intimine de la bactérie entéropathogène Escherichia coli. La liaison se fait par l'intermédiaire des sucres et confère ainsi une protection contre ces pathogènes. Ainsi, SC a été identifié comme agent neutralisant au niveau de l'intestin. La deuxième partie de ce travail abordait le sujet des allergies alimentaires, et avait pour but de tester les effets bénéfiques potentiels d'une bactérie probiotique, Lactobacillus paracasei NCC2461, contre les réactions allergiques. Un modèle marin d'allergie alimentaire a été mis au point, permettant de mesurer des immunoglobulines E, des symptômes allergiques, et la dégranulation de mastocytes. Lorsque le probiotique a été administré aux souris, celles-ci ont été complètement protégées des réactions allergiques dans une première expérience. Cependant, cette protection n'a pas été reproduite et suggère que des facteurs environnementaux encore inconnus sont critiques pour que le probiotique agisse positivement. Ce travail a permis de mettre en évidence la complexité de l'approche des traitements liés aux probiotiques et ouvre la voie sur la compréhension des mécanismes liés à l'allergie. Abstract The mucosal immune system associated to the gastrointestinal mucosa must efficiently distinguish between innocuous antigens, such as food proteins and commensal bacteria and potentially infectious agents. The work presented here deals with these two essential aspects guaranteeing intestinal homeostasis. In the first part of this work, the protective properties of secretory component (SC) toward the pathogen rotavirus were investigated. SC, which allows the transport of polymeric immunoglobulins (Ig) to mucosal surfaces, is highly glycosylated with complex glycan structures. The abundance and the nature of these carbohydrates led us to speculate that SC might interact with rotavirus, which is known to bind target cells with glycan receptors. Using various biological and biochemical techniques, we demonstrated that SC did not interact with rotaviruses, nor protected epithelial cells from infection. However, SC was shown to bind to Clostridium difficile toxin A and to the enteropathogenic Echerischia coli adhesion molecule intimin in a glycan-dependent fashion. These interactions allow in vitro protection of epithelial cells using physiological concentrations of SC. These data identify SC as a microbial scavenger at mucosal surfaces, and in the context of secretory IgA, further enhance the neutralising properties of the complex. The second project was inscribed in the domain of food allergy and aimed to test the modulatory functions of a probiotic strain of Lactobacillus paracasei toward allergic reactions. A model of food-mediated allergy was developed in the mouse using mucosal sensitisation. Several parameters associated to allergy were quantified after allergen challenge, and included allergen-specific IgE, allergic signs like diarrhea and temperature drop, and degranulation of mast cells. Administration of the probiotic strain was shown to completely protect mice from allergic reactions. However, these data were not reproduced, suggesting that unknown environmental factors are required so that protection mediated by the probiotic strain occurs. This study paves the way to the understanding of the mechanisms associated to allergy, and highlights the tremendous complexity that probiotic treatments will have to face.

Enhancement of Th1 Lung Immunity Induced by Recombinant Mycobacterium bovis Bacillus Calmette-Guerin Attenuates Airway Allergic Disease

Mycobacterium bovis Bacillus Calmette-Guerin (BCG) has been shown to down-regulate experimental allergic asthma, a finding that reinforced the hygiene hypothesis. We have previously found that recombinant BCG (rBCG) strain that express the genetically detoxified Si subunit of pertussis toxin (rBCG-S1PT) exerts an adjuvant effect that enhances Th1 responses against BCG proteins. Here we investigated the effect of this rBCG-S1PT on the classical ovalbumin-induced mouse model of allergic lung disease. We found that rBCG-S1PT was more effective than wild-type BCG in preventing Th2-mediated allergic immune responses. The inhibition of allergic lung disease was not associated with increased concentration of suppressive cytokines or with an increased number of pulmonary regulatory T cells but was positively correlated with the increase in IFN-gamma-producing T cells and T-bet expression in the lung. In addition, an IL-12-dependent mechanism appeared to be important to the inhibition of lung allergic disease. The inhibition of allergic inflammation was found to be restricted to the lung because when allergen challenge was given by the intraperitoneal route, rBCG-S1PT administration failed to inhibit peritoneal allergic inflammation and type 2 cytokine production. Our work offers a nonclassical interpretation for the hygiene hypothesis indicating that attenuation of lung allergy by rBCG could be due to the enhancement of local lung Th1 immunity induced by rBCG-S1PT. Moreover, it highlights the possible use of rBCG strains as multipurpose immunomodulators by inducing specific immunity against microbial products while protecting against allergic asthma.

Regulatory T Cells Accumulate in the Lung Allergic Inflammation and Efficiently Suppress T-Cell Proliferation but Not Th2 Cytokine Production

Foxp3(+)CD25(+)CD4(+) regulatory T cells are vital for peripheral tolerance and control of tissue inflammation. In this study, we characterized the phenotype and monitored the migration and activity of regulatory T cells present in the airways of allergic or tolerant mice after allergen challenge. To induce lung allergic inflammation, mice were sensitized twice with ovalbumin/aluminum hydroxide gel and challenged twice with intranasal ovalbumin. Tolerance was induced by oral administration of ovalbumin for 5 consecutive days prior to OVA sensitization and challenge. We detected regulatory T cells (Foxp3(+)CD25(+)CD4(+) T cells) in the airways of allergic and tolerant mice; however, the number of regulatory T cells was more than 40-fold higher in allergic mice than in tolerant mice. Lung regulatory T cells expressed an effector/memory phenotype (CCR4(high)CD62L(low)CD44(high)CD54(high)CD69(+)) that distinguished them from naive regulatory T cells (CCR4(int)CD62L(high)CD44(int)CD54(int)CD69(-)). These regulatory T cells efficiently suppressed pulmonary T-cell proliferation but not Th2 cytokine production.

Recombinant DNA immunotherapy ameliorate established airway allergy in a IL-10 dependent pathway

Background Previous studies have established that mycobacterial infections ameliorate allergic inflammation. However, a non-infectious approach that controls allergic responses might represent a safer and more promising strategy. The 60-65 kDa heat shock protein (Hsp) family is endowed with anti-inflammatory properties, but it is still unclear whether and how single mycobacterial Hsp control allergic disorders. Objective Therefore, in this study we determined whether the administration of Mycobacterial leprae Hsp65 expressed by recombinant a DNA plasmid could attenuate a previously established allergic response. Methods We used an experimental model of airway allergic inflammation to test the effects of immunotherapy with DNA encoding Hsp65. Allergic mice, previously sensitized and challenged with ovalbumin, were treated with tree intramuscular doses of recombinant DNA encoding Hsp65. After treatment, mice received a second allergen challenge and the allergic response was measured. Results We found that immunotherapy attenuated eosinophilia, pulmonary inflammation, Th2 cytokine and mucus production. Moreover, we showed that the inhibition of allergic response is dependent on IL-10 production. Both Hsp65 and allergen-specific IL-10-producing cells contributed to this effect. Cells transferred from DNA-immunized mice to allergic mice migrated to allergic sites and down-modulated the Th2 response. Conclusions and Clinical Relevance Our findings clearly show that immunotherapy with DNA encoding Hsp65 can attenuate an established Th2 allergic inflammation through an IL-10-dependent mechanism; moreover, the migration of allergen-and Hsp65-specific cells to the allergic sites exerts a fundamental role. This work represents a novel contribution to the understanding of immune regulation by Hsp65 in allergic diseases.

Rolle von NFATc2 in einem murinen Asthmamodell

Nuclear factor of activated T cells (NFAT) ist eine Familie der Transkriptionsfaktoren, welche eine wichtige Rolle bei der Regulation der T-Zellvermittelten Signalkaskade in der Lymphozytenpopulation spielt. In dieser Arbeit konnte gezeigt werden, dass Nuclear Factor of Activated T cells-2 (NFATc2) defiziente Mäuse einen erhöhten Atemwegswiderstand, einen pathologische Veränderung der Lunge und einen erhöhten IgE Spiegel im Vergleich zu den Wildtypen vorweisen. Die NFATc2 Defizienz konnte ebenfalls sowohl mit einer erhöhten Anzahl an Th2 und Th17 Zellen, die eine erhöhte Proliferation vorweisen, als auch einer erniedrigten Anzahl an CD8+ CD122- T-Zellen, die geringere Mengen an IFN-g produzieren, in Verbindung gebracht werden. Die aus den NFATc2(-/-) Mäusen isolierten CD4+ T-Zellen zeigen im Vergleich zu denen der Wildtypen neben der erhöhten Proliferation einen vermehrte Aktivierung (CD4higCD44highCD69high). Weiterhin konnte in dieser Arbeit gezeigt werden, dass in Anwesenheit eines Allergens, die NFATc2(-/-) Mäuse eine erhöhte Anzahl an regulatorischen T-Zellen (CD4+CD25+Foxp3+GITR++) in der Lunge vorweisen, die wiederum die Effektorzellen in diesen hemmen. Ein Grund für die geringere Freisetzung an IFN-g durch die CD8+ T-Zellen in den NFATc2 defizienten Mäusen ist eine erhöhte Subpopulation von CD8+CD122+ (IL-2Rb Kette) CD127hi (IL-7Ra Kette) „long-lived memory Zellen“ in den NFATc2(-/-) Mäusen. Diese besitzen einen regulatorischen Effekt, so dass immundefiziente SCID Mäuse, die in einem adoptiven Transfer mit OVA-spezifischen CD8+ und CD4+ T-Zellen, welchen aus NFATc2(-/-) Mäuse isoliert werden, behandelt wurden, eine erhöhten Atemwegswiderstand, eine erhöhte IL-17 und eine erniedrigte IFN-g Produktion vorweisen. Eine Depletion der memory CD8+CD122+IL-7Rhigh T-Zellen hebt dagegen die verringerte IFN-g Produktion der CD8+CD122- T-Zellen auf und führt zu einer Erniedrigung des Atemwegswiderstandes in einem SCID Model Zusammenfassend zeigen unsere Untersuchungen, dass sowohl die IFN-g Produktion der CD8+ Effektor T-Zellen als auch die Anzahl an CD4+CD25+Foxp3+GITR++ regulatorischen T-Zellen die Entwicklung der Th2 und Th17 als auch die Höhe des Atemwegswiderstandes unterdrückt.

Die Rolle der Mastzelle bei der Entstehung einer allergischen Atemwegserkrankung

In der vorliegenden Arbeit wurde die Rolle der Mastzelle und deren Mediatoren für die Entstehung einer allergischen Atemwegsentzündung untersucht. Anhand von zwei mastzelldefizienten Mausstämmen (C57BL/6-KitWsh/Wsh und WBB6FI-KitW/Wv), konnte gezeigt werden, dass Mastzellen an der Entstehung einer allergischen Entzündung und Atemwegsüberempfindlichkeit beteiligt sind. Durch die Rekonstitution von mastzelldefizienten Tieren mit aus Knochenmark gewonnenen Mastzellen (BMMC) von Wildtyp-Spendern konnte die wichtige Funktion der Mastzelle in diesem Model bestätigt werden. Überdies konnte durch die Rekonstitution mit TNF-defizienten BMMC eine wichtige Rolle für diesen mastzellproduzierten Mediator im allergischen Modell demonstriert werden. Weiterhin konnte die Arbeit zeigen, dass Mastzellen wichtig für die Migration von antigenbeladenen Dendritischen Zellen aus der Lunge in die regionalen Lymphknoten sind. Dieses stellt einen wichtigen Schritt für die Ausbildung einer lokalen allergischen Antwort dar. Im Gegensatz dazu war die Entstehung einer allergischen Atemwegserkrankung nach Transfer von in vitro generierten DC und Allergenprovokation nicht mastzellabhängig. Diese Ergebnisse zeigen, dass es auf die Wahl des Sensibilisierungs- und Provokationsmodels ankommt, um mastzellspezifische Effekte zu demonstrieren. Die vorliegende Arbeit zeigt die wichtige Rolle der Mastzelle und von mastzellproduziertem TNF bei der Ausbildung einer allergischen Entzündung der Atemwege. Die Mastzelle und deren Mediatoren stellen somit mögliche Ziele für die therapeutische Behandlung der allergischen Entzündung der Atemwege dar.