Diversité de la réponse IgE dans l'allergie à l'arachide : caractérisation des allergènes et devenir de leur potentiel allergénique lors des traitements thermiques et des processus digestifs

L’allergie à l’arachide représente un tiers des allergies alimentaires en France. Elle entraîne des réactions souvent sévères et ne s’atténue que rarement avec l’âge. Elle relève principalement d’une réaction d’hypersensibilité immédiate médiée par les immunoglobulines de type E (IgE) spécifiques de certaines protéines de l’arachide. De nombreuses protéines et fragments peptidiques extraits de la graine, purifiés par chromatographies et caractérisés par séquençage ainsi que par analyse protéomique, ont pu être classés dans trois familles de protéines de réserve des plantes, les globulines 7S, 11S et les albumines 2S. L’étude de la capacité de liaison aux IgE de ces protéines et des peptides qui en dérivent a été menée à l’aide de 80 sérums de patients allergiques à l’arachide par des techniques de type ELISA. Des allergènes majeurs (entraînant une réponse IgE spécifique intense chez la majorité des patients) se retrouvent dans chacune des familles. Les albumines 2S présentent le potentiel allergénique le plus marqué. Chaque patient est sensibilisé à plusieurs protéines. De plus, pour chaque allergène, les IgE peuvent reconnaître plusieurs régions intramoléculaires. Selon les protéines, les différents traitements thermiques peuvent modifier ou non le potentiel allergénique. Les processus digestifs réalisés in vivo et dans des tests de digestibilité in vitro dégradent complètement les protéines mais ne suppriment pas le potentiel allergénique de l’arachide. Les fragments peptidiques de faible masse moléculaire tels que ceux issus de ces hydrolyses enzymatiques jouent vraisemblablement un rôle important dans la mise en place et le développement de l’allergie à l’arachide.\ud ________________________________________________________________________________________________________\ud Peanut allergy represents about 30% of food allergies in France. It is one of the most frequent cause of severe food-associated anaphylaxis and it tends to persist throughout life. Allergy to peanut is an IgE-mediated reaction. Several proteins and peptide fragments derived therefrom were extracted from the kernels. They were purified by a combinaison of selective precipitations and chromatographic separations, then characterized by N-terminal amino acid sequencing and proteomics. They belong to 3 major plant storage protein families, i.e. the 7S and 11S globulins and 2S albumins. The analysis of the IgE-binding capacity of those proteins and derived peptides was performed by Enzyme AllergoSorbent Test (EAST) and EAST inhibition using the sera of 80 peanut allergic patients. The major allergens which lead to an intense specific IgE response in the vast majority of patients were found in each plant protein family. 2S albumins exhibited the most important allergenic potential. Each patient appeared to be sensitized to numerous proteins. Moreover, for each allergen, several intramolecular regions were recognized by specific IgE. Depending on the allergen, the different thermal processings either modified or did not modify the allergenic potential. Proteins were extensively degraded during in vivo and in vitro digestion but their allergenic potential was not abolished. Low molecular weight peptide fragments such as those formed by pepsin and pepsin, trypsin and chymotrypin hydrolysis certainly play a central role in the sensitization process and the development of peanut allergy

Epicutaneous Immunotherapy (EPIT) Blocks the Allergic Esophago-Gastro-Enteropathy Induced by Sustained Oral Exposure to Peanuts in Sensitized Mice

Background: Food allergy may affect the gastrointestinal tract and eosinophilia is often associated with allergic gastrointestinal disorders. Allergy to peanuts is a life-threatening condition and effective and safe treatments still need to be developed. The present study aimed to evaluate the effects of sustained oral exposure to peanuts on the esophageal and jejunal mucosa in sensitized mice. We also evaluated the effects of desensitization with epicutaneous immunotherapy (EPIT) on these processes. Methods: Mice were sensitized by gavages with whole peanut protein extract (PPE) given with cholera toxin. Sensitized mice were subsequently exposed to peanuts via a specific regimen and were then analysed for eosinophilia in the esophagus and gut. We also assessed mRNA expression in the esophagus, antibody levels, and peripheral T-cell response. The effects of EPIT were tested when intercalated with sensitization and sustained oral peanut exposure. Results: Sustained oral exposure to peanuts in sensitized mice led to severe esophageal eosinophilia and intestinal villus sub-atrophia, i.e. significantly increased influx of eosinophils into the esophageal mucosa (136 eosinophils/mm2) and reduced villus/crypt ratios (1.660.15). In the sera, specific IgE levels significantly increased as did secretion of Th2 cytokines by peanut-reactivated splenocytes. EPIT of sensitized mice significantly reduced Th2 immunological response (IgE response and splenocyte secretion of Th2 cytokines) as well as esophageal eosinophilia (50 eosinophils/mm2, p,0.05), mRNA expression of Th2 cytokines in tissue - eotaxin (p,0.05), IL-5 (p,0.05), and IL-13 (p,0.05) -, GATA-3 (p,0.05), and intestinal villus sub-atrophia (2.360.15). EPIT also increased specific IgG2a (p,0.05) and mRNA expression of Foxp3 (p,0.05) in the esophageal mucosa. Conclusions: Gastro-intestinal lesions induced by sustained oral exposure in sensitized mice are efficaciously treated by allergen specific EPIT

Effect of simulated gastro-duodenal digestion on the allergenic reactivity of beta-lactoglobulin

<p>Abstract</p> <p>Background</p> <p>Cow's milk (CM) allergy affects about 2% of infants. The allergenicity of dietary proteins, including those from CM, has been related to their digestibility although the generality of the link and its causality remains to be demonstrated. In this study we use an in vitro digestion system, to investigate the digestibility of β-lactoglobulin (blg) during gastrointestinal transit and to assess the impact of this process on blg allergenic reactivity in CM allergic children.</p> <p>Methods</p> <p>Blg digesta were prepared using an <it>in vitro </it>digestion protocol simulating either gastric digestion alone or followed by duodenal digestion with or without phosphatidylcholine (PC). Biochemical analysis of blg digesta was performed by SDS-PAGE and their concentration was measured by a sandwich ELISA. Assessment of their allergenic reactivity was done <it>in vitro </it>by EAST inhibition, specific basophil activation (basotest) and lymphocyte proliferation (PCNA-flow cytometry) assays using sera and cells from patients allergic to blg and <it>in vivo </it>by skin prick testing (SPT) of these patients.</p> <p>Results</p> <p>Blg was only broken down to smaller peptides after gastro-duodenal digestion although a sizeable amount of intact protein still remained. Digestion did not modify the IgE binding capacity of blg except for gastro-duodenal digestion performed in the absence of PC. These results are consistent with the quantity of intact blg remaining in the digesta. Overall both gastric and gastroduodenal digestion enhanced activation of sensitized basophils and proliferation of sensitized lymphocytes by blg. However, there was a tendency towards reduction in mean diameter of SPT following digestion, the PC alone during phase 1 digestion causing a significant increase in mean diameter.</p> <p>Conclusions</p> <p>Digestion did not reduce the allergenic reactivity of blg to a clinically insignificant extent, PC inhibiting digestion and thereby protecting blg allergenic reactivity. SPT reactivity was reduced compared to blg immunoreactivity in <it>in vitro </it>tests.</p

Antigen Uptake by Langerhans Cells Is Required for the Induction of Regulatory T Cells and the Acquisition of Tolerance During Epicutaneous Immunotherapy in OVA-Sensitized Mice

The skin is a major immunologic organ that may induce protection, sensitization or tolerance. Epicutaneous immunotherapy (EPIT) has been proposed as an attractive strategy to actively treat food allergy and has been shown to induce tolerance in sensitized mice through the induction of Foxp3+ regulatory T cells (Tregs), especially CD62L+ Tregs. Among immune cells in the skin, dendritic cells are key players in antigen-specific immune activation or regulation. The role of different populations of skin DCs in tolerance induction remains to be elucidated. Using OVA-sensitized BALB/c mice, we demonstrated that the application of a patch containing OVA-A647 to the skin resulted in allergen uptake by Langerhans cells (LCs) and CD11b+ dermal cDC2 and subsequent migration into skin draining lymph nodes. These 2 populations induced Foxp3 expression in CD4+ cells in vitro. Only LCs induced LAP+ cells and CD62L+ Tregs. Using Langerin-eGFP-DTR mice, we analyzed the role of LCs in the mechanisms of tolerance induction by EPIT in vivo. Following complete depletion of LCs, a dramatic decrease in the number of OVA+ DCs and OVA+ CD11b+ dermal cDC2 was observed in skin draining lymph nodes 48 h after epicutaneous application. Likewise, 2 weeks of EPIT in non-depleted mice induced Foxp3+ Tregs, especially CD62L+, and LAP+ Tregs in skin draining lymph nodes and spleen, whereas no induction of Tregs was observed in LC-depleted mice. Following 8 weeks of treatment, EPIT-treated mice showed significant protection against anaphylaxis accompanied by a significant increase of Foxp3+ Tregs, especially CD62L+ Tregs, which was not seen in the absence of LCs. In summary, although both LCs and CD11b+ dermal cDC2s could induce regulatory T cells, the absence of LCs during EPIT impaired treatment efficacy, indicating their crucial role in skin-induced tolerance

Justification of Visualization Technique of Domain Structure with Raman Scattering

Qualitative mechanism in line with experimental data on visualization of the domain structure and fine structure of the domain wall in weak ferromagnets has been proposed. The mechanism is based on the phenomenological consideration of Faraday rotation, optical absorption, and atom polarization in response to the radiation exciting Raman scattering. Qualitative agreement of estimates on the scattered radiation intensity in oppositely- magnetized domains with experimental results is good, which made it possible to attack problems of visualization of magnetic entities with nanoscale resolution. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3197

Diversité de la réponse IgE dans l'allergie à l' arachide (caractérisation des allergènes et devenir de leur potentiel allergénique lors des traitements thermiques et des processus digestifs)

L'allergie à l'arachide représente un tiers des allergies alimentaires en France. Elle entraîne des réactions souvent sévères et ne s'atténue que rarement avec l'âge. Elle relève principalement d'une réaction d'hypersensibilité immédiate médiée par les immunoglobulines de type E (IgE) spécifiques de certaines protéines de l'arachide. De nombreuses protéines et fragments peptidiques extraits de la graine, purifiés par chromatographies et caractérisés par séquençage ainsi que par analyse protéomique, ont pu être classés dans trois familles de protéines de réserve des plantes, les globulines 7S, 11S et les albumines 2S. L'étude de la capacité de liaison aux IgE de ces protéines et des peptides qui en dérivent a été menée à l'aide de 80 sérums de patients allergiques à l'arachide par des techniques de type ELISA. Des allergènes majeurs (entraînant une réponse IgE spécifique intense chez la majorité des patients) se retrouvent dans chacune des familles. Les albumines 2S présentent le potentiel allergénique le plus marqué. Chaque patient est sensibilisé à plusieurs protéines. De plus, pour chaque allergène, les IgE peuvent reconnaître plusieurs régions intramoléculaires. Selon les protéines, les différents traitements thermiques peuvent modifier ou non le potentiel allergénique. Les processus digestifs réalisés in vivo et dans des tests de digestibilité in vitro dégradent complètement les protéines mais ne suppriment pas le potentiel allergénique de l'arachide. Les fragments peptidiques de faible masse moléculaire tels que ceux issus de ces hydrolyses enzymatiques jouent vraisemblablement un rôle important dans la mise en place et le développement de l'allergie à l'arachidePeanut allergy represents about 30% of food allergies in France. It is one of the most frequent cause of severe food-associated anaphylaxis and it tends to persist throughout life. Allergy to peanut is an IgE-mediated reaction. Several proteins and peptide fragments derived therefrom were extracted from the kernels. They were purified by a combinaison of selective precipitations and chromatographic separations, then characterized by N-terminal amino acid sequencing and proteomics. They belong to 3 major plant storage protein families, i.e. the 7S and 11S globulins and 2S albumins. The analysis of the IgE-binding capacity of those proteins and derived peptides was performed by Enzyme AllergoSorbent Test (EAST) and EAST inhibition using the sera of 80 peanut allergic patients. The major allergens which lead to an intense specific IgE response in the vast majority of patients were found in each plant protein family. 2S albumins exhibited the most important allergenic potential. Each patient appeared to be sensitized to numerous proteins. Moreover, for each allergen, several intramolecular regions were recognized by specific IgE. Depending on the allergen, the different thermal processings either modified or did not modify the allergenic potential. Proteins were extensively degraded during in vivo and in vitro digestion but their allergenic potential was not abolished. Low molecular weight peptide fragments such as those formed by pepsin and pepsin, trypsin and chymotrypin hydrolysis certainly play a central role in the sensitization process and the development of peanut allergyTOULOUSE-INSA (315552106) / SudocSudocFranceF