Background The 2S-albumin Ara h 2 is the most potent peanut allergen and a good predictor of clinical reactivity in allergic children. Posttranslational hydroxylation of proline residues occurs in ...DPYSPOH S motifs, which are repeated 2 or 3 times in different isoforms. Objectives We investigated the effect of proline hydroxylation on IgE binding and the relative contributions of linear and conformational epitopes to Ara h 2 allergenicity. Methods Peptides containing DPYSPOH S motifs were synthesized. A recombinant variant of Ara h 2 without DPYSPOH S motifs was generated by means of deletion mutagenesis. IgE reactivity of 18 French and 5 American patients with peanut allergy toward synthetic peptides and recombinant allergens was assessed by using IgE-binding inhibition assays and degranulation tests of humanized rat basophilic leukemia cells. Results Hydroxyproline-containing peptides exhibited an IgE-binding activity equivalent to that of the unfolded Ara h 2. In contrast, corresponding peptides without hydroxyprolines displayed a very weak IgE-binding capacity. Despite removal of the DPYSPOH S motifs, the deletion variant still displayed Ara h 2 conformational epitopes. The IgE-binding capacity of Ara h 2 was then recapitulated with an equimolar mixture of a hydroxylated peptide and the deletion variant. Hydroxylated peptides of 15 and 27 amino acid residues were also able to trigger cell degranulation. Conclusions Sensitization toward linear and conformational epitopes of Ara h 2 is variable among patients with peanut allergy. Optimal IgE binding to linear epitopes of Ara h 2 requires posttranslational hydroxylation of proline residues. The absence of hydroxyprolines could then affect the accuracy of component-resolved diagnostics by using rAra h 2.
To provide updated data on the characteristics (eg, structure, function, stability) of the main milk proteins identified as allergens and on the characterization of their epitopes.
Basic literature ...and the most relevant original recent publications on clinical and epidemiologic aspects of milk allergy and the biochemistry and immunochemistry of milk proteins.
The expert opinion of the author was used to select the relevant data for the review.
Most milk proteins, even proteins present at low concentrations, are potential allergens. Epitopes on milk proteins are both conformational and linear epitopes, widely spread throughout the protein molecules. They may be short fragments, located in hydrophobic parts of the molecule, that comprise highly conserved sequences responsible for IgE cross-reactivity with corresponding milk proteins of other mammals, including humans. Those sequential epitopes have also been proposed as good markers of persistent allergy to milk proteins and may be of particular clinical significance.
No specific structure or function is associated with allergenicity of milk proteins. Due to the great variability and heterogeneity of the human IgE response, no single allergen or particular structure can account for a major part of milk allergenicity. Furthermore, the available evidence is not sufficient to establish an intake threshold below which allergic reactions are not triggered or to predict reliably the effect of food processing on allergenic potential of milk proteins.
Scope: Roasting rather than boiling and Maillard modifications may modulate peanut allergenicity. We investigated how these factors affect the allergenic properties of a major peanut allergen, Ara h ...1.
Methods and results: Ara h 1 was purified from either raw (N‐Ara h 1) or roasted (R‐Ara h 1) peanuts. Boiling (100°C 15 min; H‐Ara h 1) resulted in a partial loss of Ara h 1 secondary structure and formation of rod‐like branched aggregates with reduced IgE‐binding capacity and impaired ability to induce mediator release. Glycated Ara h 1 (G‐Ara h 1) formed by boiling in the presence of glucose behaved similarly. However, H‐ and G‐Ara h1 retained the T‐cell reactivity of N‐Ara h 1. R‐Ara h 1 was denatured, comprised compact, globular aggregates, and showed no evidence of glycation but retained the IgE‐binding capacity of the native protein.
Conclusion: Ara h 1 aggregates formed by boiling were morphologically distinct from those formed by roasting and had lower allergenic activity. Glycation had no additional effect on Ara h 1 allergenicity compared with heating alone. Taken together with published data on the loss of Ara h 2/6 from boiled peanuts, this supports the hypothesis that boiling reduces the allergenicity of peanuts.
This document provides supplementary guidance on specific topics for the allergenicity risk assessment of genetically modified plants. In particular, it supplements general recommendations outlined ...in previous EFSA GMO Panel guidelines and Implementing Regulation (EU) No 503/2013. The topics addressed are non‐IgE‐mediated adverse immune reactions to foods, in vitro protein digestibility tests and endogenous allergenicity. New scientific and regulatory developments regarding these three topics are described in this document. Considerations on the practical implementation of those developments in the risk assessment of genetically modified plants are discussed and recommended, where appropriate.
This publication is linked to the following EFSA Supporting Publications article: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2017.EN-1259/full
Recommendations and guidelines on the prevention of food allergy have changed in recent decades. The aim of this review of the current evidence and ongoing studies is to provide a comprehensive and ...up to date picture of prevention of food allergy for healthcare professionals. The review was undertaken as part of the European Union funded Integrated Approaches to Food Allergy and Allergen Management (iFAAM) study. This is a wide ranging project bringing together expertise across the breadth of food allergy research. Specifically, the review discusses dietary manipulation in food allergy prevention, and covers the possible preventive strategies of allergen avoidance, early allergen introduction, general nutrition and supplements, as well as other strategies, such as prebiotics and probiotics. The review concludes that despite agreement that allergen avoidance strategies should not be undertaken for allergy prevention, there is currently no consensus regarding what actions should be recommended beyond exclusive breastfeeding for the first 4–6 months of life. Recent and upcoming trial results, which are detailed in this review, should help inform the debate and add clarity to the topic.
In June 2005, the work of the EU Integrated Project EuroPrevall was started. EuroPrevall is the largest research project on food allergy ever performed in Europe. Major aims of the project are to ...generate for the first time reliable data on the prevalence of food allergies across Europe and on the natural course of food allergy development in infants. Improvement of in vitro diagnosis of food allergies is another important aim of the project. The present review summarizes current knowledge about the clinical presentation of food allergy and critically reviews available diagnostic tools at the beginning of the project period. A major problem in diagnosis is a relatively poor ‘clinical specificity’, i. e. both positive skin tests and in vitro tests for specific IgE are frequent in sensitized subjects without food allergy symptoms. So far, no in vitro test reliably predicts clinical food allergy. EuroPrevall aims at improving the predictive value of such tests by proceeding from diagnosis based on allergen extracts to purified allergen molecules, taking into account the affinity of the IgE–allergen interaction, and evaluating the potential of biological in vitro tests such as histamine release tests or basophil activation tests including assays performed with permanently growing cell lines.
Scope
2S‐albumins Ara h 2 and Ara h 6 are the most widely recognized and potent allergens for peanut‐allergic patients. These allergens are particularly resistant to proteolysis and the digestion ...products generally retain significant allergenicity. Five disulfide bridges (DB) stabilize Ara h 6 overall structure and their influence on the trypsin resistance and on the allergenicity of the digestion products was investigated.
Methods and results
Progressive disruption of each DB was performed by site‐directed mutagenesis. Successful refolding of Ara h 6 variants was confirmed by circular dichroism. Trypsin resistance, IgE‐binding capacity and allergenic potency, as assessed by in vitro mediator release assay with sera from peanut‐allergic patients, was not affected by the deletion of the C‐terminal DB at Cys84‐Cys124. Additional disruption of DB at Cys14‐Cys71 or at Cys73‐Cys115 rendered Arg16/20 or Arg114 susceptible to trypsinolysis, respectively, but affected principally the IgE‐binding capacity of Ara h 6. DB disruption at Cys26‐Cys58 or at Cys59‐Cys107 led to an extensive proteolytic degradation and a complete loss of allergenic potency of the digestion products.
Conclusion
Selective disruption of the DB stabilizing the protease‐resistant core of Ara h 6 eliminated the IgE‐binding capacity of the trypsin‐degradation products and their ability to trigger mast cell degranulation.
In January 2014, an international meeting sponsored by the International Life Sciences Institute/Health and Environmental Sciences Institute and the Canadian Food Inspection Agency titled “Genetic ...Basis of Unintended Effects in Modified Plants” was held in Ottawa, Canada, bringing together over 75 scientists from academia, government, and the agro-biotech industry. The objectives of the meeting were to explore current knowledge and identify areas requiring further study on unintended effects in plants and to discuss how this information can inform and improve genetically modified (GM) crop risk assessments. The meeting featured presentations on the molecular basis of plant genome variability in general, unintended changes at the molecular and phenotypic levels, and the development and use of hypothesis-driven evaluations of unintended effects in assessing conventional and GM crops. The development and role of emerging “omics” technologies in the assessment of unintended effects was also discussed. Several themes recurred in a number of talks; for example, a common observation was that no system for genetic modification, including conventional methods of plant breeding, is without unintended effects. Another common observation was that “unintended” does not necessarily mean “harmful”. This paper summarizes key points from the information presented at the meeting to provide readers with current viewpoints on these topics.
Peanut allergy is one of the most common and severe food allergies, and processing is known to influence the allergenicity of peanut proteins. We aimed to establish the effect of heating and ...glycation on the IgE-binding properties and biological activity of 2S albumins (Ara h 2/6) from peanut.
Native Ara h 2/6 was purified from raw peanuts and heated in solution (15 min, 110°C) in the presence or absence of glucose. Ara h 2 and 6 were also purified from roasted peanut. Using PBMC and sera from peanut-allergic patients, the cellular proliferative potency and IgE reactivity (reverse EAST inhibition) and functionality (basophil degranulation capacity) of allergens were assessed. Heating Ara h 2/6 at 110°C resulted in extensive denaturation, hydrolysis and aggregation of the protein, whilst Ara h 2 and 6 isolated from roasted peanut retained its native conformation. Allergen stimulation of PBMC induced proliferation and Th2 cytokine secretion which was unaffected by thermal processing. Conversely, IgE reactivity and functionality of Ara h 2/6 was decreased by heating. Whilst heating-glycation further reduced the IgE binding capacity of the proteins, it moderated their loss of histamine releasing capacity. Ara h 2 and 6 purified from roasted peanut demonstrated the same IgE reactivity as unheated, native Ara h 2/6.
Although no effect of processing on T-cell reactivity was observed, heat induced denaturation reduced the IgE reactivity and subsequent functionality of Ara h 2/6. Conversely, Ara h 2 and 6 purified from roasted peanut retained the structure and IgE reactivity/functionality of the native protein which may explain the allergenic potency of this protein. Through detailed molecular study and allergenicity assessment approaches, this work then gives new insights into the effect of thermal processing on structure/allergenicity of peanut proteins.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Within the frame of the EU-funded MARLON project, background data were reviewed to explore the possibility of measuring health indicators during post-market monitoring for potential effects of feeds, ...particularly genetically modified (GM) feeds, on livestock animal health, if applicable. Four case studies (CSs) of potential health effects on livestock were framed and the current knowledge of a possible effect of GM feed was reviewed. Concerning allergenicity (CS-1), there are no case-reports of allergic reactions or immunotoxic effects resulting from GM feed consumption as compared with non-GM feed. The likelihood of horizontal gene transfer (HGT; CS-2) of GMO-related DNA to different species is not different from that for other DNA and is unlikely to raise health concerns. Concerning mycotoxins (CS-3), insect-resistant GM maize may reduce fumonisins contamination as a health benefit, yet other Fusarium toxins and aflatoxins show inconclusive results. For nutritionally altered crops (CS-4), the genetic modifications applied lead to compositional changes which require special considerations of their nutritional impacts.
No health indicators were thus identified except for possible beneficial impacts of reduced mycotoxins and nutritional enhancement. More generally, veterinary health data should ideally be linked with animal exposure information so as to be able to establish cause-effect relationships.
•No case-reports of allergic reactions or immunotoxic effects were found in GM versus non GM-fed animals.•HGT probability of GM-DNA is equal to that one of non-GM, however transfer is unlikely to raise health concerns.•Scientific evidence shows that fumonisins reduction is more often an advantageous side effect in GM crop.•The potential contribution of nutritionally altered crops does not envisage nutritional imbalances in animal diets.•No animal health indicator was found to be distinctively associated with GM-crop-based feeding regimes.
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