Gastrointestinal digestion of hazelnut allergens on molecular level: Elucidation of degradation kinetics and resistant immunoactive peptides using mass spectrometry.
SCOPE: Allergy to hazelnut seeds ranks among the most prevalent food allergies in Europe. The aim of this study was to elucidate the gastrointestinal digestion of hazelnut allergens on molecular level. METHODS AND RESULTS: Hazelnut flour was digested in vitro following the Infogest consensus model. For six allergenic proteins, the time-dependent course of digestion was monitored by SDS-PAGE and HPLC-MS/MS, and degradation products were characterized by a bottom-up proteomics approach. Depending on the molecular structure, a specific biochemical fate was observed for each allergen, and degradation kinetics were traced back to the peptide level. 1183 peptides were characterized, including 130 peptides that carry known IgE-binding epitopes and may represent sensitizers for hazelnut allergy. The kinetics of peptide formation and degradation were determined by label free quantification and follow a complex multi-stage mechanism. CONCLUSION: We present a comprehensive survey on the gastrointestinal digestion of a relevant allergenic food on level of the peptidome, including the first systematic characterization and quantification of degradation products. This provides information on the differential resistance of plant food allergens and their structural elements undergoing digestion and forms the basis for a deeper understanding of the molecular principles responsible for sensitization to food allergy.
Prediction of cashew nut allergy in sensitised children.
As an alternative to the costly, time-consuming and possibly stressful double-blind, placebo-controlled challenge (DBPCFC) test, a model to predict the risk of cashew nut allergy was studied incorporating patient characteristics, standard diagnostic parameters (specific IgE (sIgE) and Skin Prick Test (SPT)) as well as component resolved diagnosis (CRD).
Characteristics of tree nut challenges in tree nut allergic and tree nut sensitized individuals.
BACKGROUND: Characteristics and outcomes of tree nut (TN) oral food challenges (OFCs) in patients with TN allergy or sensitization alone are poorly studied. OBJECTIVE: To determine the relation between TN sensitization levels and OFC outcomes. METHODS: Open TN OFCs performed from 2007 through 2015 at a referral center were analyzed to compare outcome based on skin prick test (SPT) wheal size, food-specific immunoglobulin E (sIgE), peanut co-allergy, and TN sensitization only vs TN allergy with sensitization to other TNs. Delayed OFC was defined as longer than 12 months from the time of an sIgE level lower than 2 kUA/L. RESULTS: Overall passage rate was 86% for 156 TN OFCs in 109 patients (54 almond, 28 cashew, 27 walnut, 18 hazelnut, 14 pecan, 13 pistachio, and 2 Brazil nut). Passage rates were 76% (n = 67) in patients with a history of TN allergy who were challenged to another TN to which they were sensitized and 91% (n = 65) in those with TN sensitization only (mean sIgE 1.53 kUA/L; range 0.35-9.14). Passage rates were 89% (n = 110 of 124) for a TN sIgE level lower than 2 kUA/L and 69% (11 of 16) for a TN sIgE level of at least 2 kUA/L. In 44 challenges in patients with peanut allergy and TN co-sensitization, the TN OFC passage rate was 96%. In 41 TN OFCs with a TN SPT wheal size of at least 3 mm, 61% passed, with a mean wheal size of 4.8 mm (range 3-11) in those passing vs 9 mm (range 3-20) in those failing. CONCLUSION: TN challenges are frequently passed in patients with TN sensitization with or without a history of TN reactivity despite a TN SPT wheal of at least 3 mm or a TN sIgE level of at least 2 kUA/L. Nearly all patients with peanut allergy and TN co-sensitization passed the TN challenge, questioning the clinical relevance of "co-allergy."
Association of Clinical Reactivity with Sensitization to Allergen Components in Multifood-Allergic Children.
BACKGROUND: Thirty percent of children with food allergies have multiple simultaneous allergies; however, the features of these multiple allergies are not well characterized serologically or clinically. OBJECTIVE: We comprehensively evaluated 60 multifood-allergic patients by measuring serum IgE to key allergen components, evaluating clinical histories and medication use, performing skin tests, and conducting double-blind, placebo-controlled food challenges (DBPCFCs). METHODS: Sixty participants with multiple food allergies were characterized by clinical history, DBPCFCs, total IgE, specific IgE, and component-resolved diagnostics (IgE and IgG4) data. The food allergens tested were almond, egg, milk, sesame, peanut, pecan, walnut, hazelnut, cashew, pistachio, soy, and wheat. RESULTS: Our data demonstrate that of the reactions observed during a graded DBPCFC, gastrointestinal reactions occurred more often in boys than in girls, as well as in individuals with high levels of IgE to 2S albumins from cashew, walnut, and hazelnut. Certain food allergies often occurred concomitantly in individuals (ie, cashew/pistachio and walnut/pecan/hazelnut). IgE testing to components further corroborated serological relationships between and among these clustered food allergies. CONCLUSIONS: Associations of certain food allergies were shown by DBPCFC outcomes as well as by correlations in IgE reactivity to structurally related food allergen components. Each of these criteria independently demonstrated a significant association between allergies to cashew and pistachio, as well as among allergies to walnut, pecan, and hazelnut.
Peanut oleosins associated with severe peanut allergy-Importance of lipophilic allergens for comprehensive allergy diagnostics.
BACKGROUND: Peanut allergy is one of the most common and most severe food allergies in Western countries and its accurate diagnosis to prevent potential life-threatening allergic reactions is crucial. However, aqueous extracts used for routine diagnostic measurements are devoid of lipophilic allergens such as oleosins. We have recently succeeded in the isolation and purification of these unique proteins, and the current study evaluates their allergenic potential and clinical relevance. OBJECTIVE: We sought to assess allergenicity and sensitization prevalence of oleosins obtained from both raw and in-shell roasted peanuts. Additionally, we tested the utilization of natural and recombinant oleosins for allergy diagnostic purposes. METHODS: Oleosin sensitization, prevalence, and impact of thermal processing were analyzed by immunoblot with sera from 52 peanut-allergic individuals displaying different clinical phenotypes. The application of natural and recombinant oleosins for allergy diagnostics was investigated by basophil activation test (BAT). IgE-binding epitopes were identified by oligopeptide microarray. RESULTS: Sensitization to oleosins was observed exclusively in peanut-allergic subjects suffering from severe systemic reactions. IgE-binding capacity of oleosins derived from in-shell roasted peanuts was increased as shown by immunoblot analysis and BAT. Both natural and recombinant molecules can be used to identify oleosin-sensitized patients by BAT. A linear epitope of Ara h 15 was determined which displays high similarity to other seed-derived oleosins. CONCLUSION: Oleosins are clinically relevant peanut allergens and most likely associated with severe allergic symptoms. In-shell roasting increases their allergenicity, which is consistent with the observation that most allergic reactions are in connection with roasted peanuts.
Update on Timing and Source of ‘Allergenic' Foods.
As the prevalence of food allergies in many communities continues to rise, the question of when in infancy to introduce any solid foods, or specific 'more allergenic' foods, as a food allergy prevention strategy has been debated. Observational studies have found that introducing any solid foods prior to 4 months of age was associated with an increased risk of allergic disease. Hence, the current allergy prevention consensus recommendation is that the introduction of any solid foods should commence after 4 months of age. Over recent years, several randomized controlled trials have been conducted to investigate the 'ideal' timing of introduction of some specific 'more allergenic' foods (including peanuts and eggs) into infant diets. To date, the results from three of these trials have determined that there is no reason to delay the introduction of the 'more allergenic' foods into the infant's diet after solid foods have commenced. However, these trials have also highlighted the finding that some infants are sensitized to food allergens before any known ingestion of solid foods. Thus, future research needs to focus on strategies to prevent early-life food allergen sensitization prior to complementary feeding.
The role of dietary interventions in the prevention of IgE‐mediated food allergy in children.
Over the last 30 years, the prevalence of food allergy has been on the rise and remains a disease that can have a significant impact on the quality of life of children and their families. There are several hypotheses that have been suggested to account for the increasing prevalence, but this review will focus on the impact that dietary factors have on food allergy development. In the past food allergy, prevalence has largely focused on allergen avoidance; however, there is increasing evidence from interventional studies that have shown that early introduction to potential food allergens may have a beneficial role in allergy prevention. This review aims to look at the evidence in support of early introduction of allergens into infant diets to prevent against the development of food allergy.
A Multi‐Center Study on Anaphylaxis caused by Peanut, Tree Nuts and Seeds in Children and Adolescents.
Peanut (PN) and tree nuts (TNs) are common causes of anaphylaxis in Western countries, but no information is available in Korea. To feature clinical characteristics of anaphylaxis caused by PN, TNs, and seeds, a retrospective medical record review was performed in 14 university hospitals in Korea (2009-2013). One hundred and twenty-six cases were identified, with the mean age of 4.9 years. PN, walnut (WN), and pine nut accounted for 32.5%, 41.3%, and 7.1%, respectively. The median values of specific IgE (sIgE) to PN, WN, and pine nut were 10.50, 8.74, and 4.61 kUA /l, respectively. Among 50 cases managed in the emergency department, 52.0% were treated with epinephrine, 66.0% with steroid, 94.0% with antihistamines, 36.0% with oxygen, and 48.0% with bronchodilator. In conclusion, WN, PN, and pine nut were the three most common triggers of anaphylaxis in Korean children, and anaphylaxis could occur at remarkably low levels of sIgE.
Identifying Epithelial Endocytotic Mechanisms of the Peanut Allergens Ara h 1 and Ara h 2.
BACKGROUND: Peanuts are still one of the highest contributors to anaphylactic deaths after ingestion of a food allergen. At the molecular level, interactions between peanut allergens and the intestinal epithelium are largely unexplored. Previous findings by our research group demonstrated that the major peanut allergens, i.e., Ara h 1, Ara h 2, Ara h 3, and Ara h 6, were able to cross the Caco-2 human cell culture model of the intestinal epithelium. This research broadened our investigation to identify the mechanisms by which the Caco-2 monolayers uptake peanut allergens, specifically by endocytosis. Here, we aim to increase our understanding of allergen-epithelial interactions and, more broadly, the pathway from allergen to allergy. METHODS: The human Caco-2 cell culture model was exposed to peanut extract and a combination of confocal microscopy and inhibition studies were used to identify the endocytotic mechanisms of peanut allergens in intestinal epithelia. RESULTS: Our findings demonstrate that the peanut allergens Ara h 1 and Ara h 2 are transported through intestinal epithelia initially via early endosomes using multiple endocytotic mechanisms. From there, they are then transported to late endosomes and ultimately to lysosomes. CONCLUSIONS: These novel findings provide insight into the allergen-epithelial interactions of peanut allergens with the intestinal epithelium. Consequently, this opens the possibility of the use of these endocytotic pathways as targets for inhibitors in therapeutic development and preventative measures for peanut allergy in the future.
Low percentage of clinically relevant pistachio nut and mango co-sensitisation in cashew nut sensitised children.
BACKGROUND: Cashew nut, pistachio nut and mango belong to the Anacardiaceae family and are botanically related. Therefore, cashew nut sensitised children are frequently advised to eliminate cashew nuts and pistachio nuts from their diet. The 'Improvement of Diagnostic mEthods for ALlergy assessment (IDEAL trial number NTR3572) study showed that cashew nut sensitised children were co-sensitised to pistachio nut in 98% of cases and to mango in 21% of cases. The aim of this follow-up study to IDEAL is to assess the clinical relevance of co-sensitisation to pistachio nut and mango in cashew nut sensitised children. METHODS: Children were recruited from the study: 'Improvement of Diagnostic mEthods for ALlergy assessment (IDEAL trial number NTR3572). Inclusion criterion for the IDEAL study was sensitization to cashew nut as demonstrated by either SPT or sIgE, and a clinical history of reactions to cashew nuts or no previous (known) exposure. Sensitized children who were tolerant to cashew nuts were excluded. Inclusion criterion for this IDEAL follow-up study was co-sensitization to pistachio nut, regardless the result of the DBPCFC with cashew nut. In this follow-up study a double-blind placebo-controlled food challenge with pistachio nut and an open food challenge with mango were performed. RESULTS: Twenty-nine children (mean age of 11.6 years, 62% male) were included. Pistachio nut sensitisation was clinically relevant in only 34% of cashew-sensitised children and only 31% of cashew challenge positive children. None of the children was challenge positive to mango. CONCLUSION: Although co-sensitisation between cashew nut and pistachio nut was observed in 98%, pistachio nut sensitisation was only clinically relevant in 34% of the children. Therefore, a challenge test with pistachio nut is recommended in children with cashew nut and pistachio nut sensitisation. Trial registration The study was registered in the Dutch trial register (registration number 3572) on 10 August 2012 (retrospectively registered).