Allergenicity Of Food Proteins Research Articles

Immunotherapy for food allergy: current proposals to improve safety and efficacy

Abstract This review mainly focuses on the novel approaches that improve the safety and efficacy of immunotherapies, namely SLIT [alone or as pre-treatment of oral immunotherapy (OIT)], epicutaneous immunotherapy (EPIT), combination of anti-IgE into OIT or sublingual immunotherapy (SLIT) and introduction of hypoallergenic allergens by modifying native food products (boiling, baking, etc.) or manufacturing recombinant proteins. Among these proposals, some are clinically proven safe such as the use of anti-IgE while some are still under preclinical trials such as the use of some newly developed recombinant food protein allergens. What is certain is that more preclinical and clinical reviews and trials would be required on all these proposals before they could be maturely, safely, and effectively promoted in the clinical settings for patients’ use.

Discovery, verification, and validation of walnut protein marker peptides using LC-MS approaches.

A key requirement of liquid chromatography-mass spectrometry (LC-MS)-based allergenic food protein analysis methods is to use protein marker peptides with good analytical performances in LC-MS analysis of commercial processed foods. In this study, we developed a multi-stage walnut protein marker peptide selection strategy involving marker peptide discovery and verification and LC-MS validation of chemically equivalent stable isotope-labeled peptides. This strategy proposed three walnut protein marker peptides, including two new marker peptides. Our LC-MS-based walnut protein analysis method using the three stable isotope-labeled peptides showed acceptable linearity (R2>0.99), matrix effects (coefficient of variation <±15%), sensitivity (limit of detection>0.3pg/μL, limit of quantification>0.8pg/μL), recovery (85.1-103.4%), accuracy, and precision (coefficient of variation<10%). In conclusion, our multi-stage marker peptide selection strategy effectively selects specific protein marker peptides for sensitive detection and absolute quantification of walnut proteins in LC-MS analysis of commercial processed foods.

In-house validation of an LC-MS method for the multiplexed quantitative determination of total allergenic food in chocolate.

Mass spectrometry has been widely accepted as a confirmatory tool for the sensitive detection of undeclared presence of allergenic ingredients. Multiple methods have been developed so far, achieving different levels of sensitivity and robustness, still lacking harmonization of the analytical validation and impairing comparability of results. In this investigation, a quantitative method has been validated in-house for the determination of six allergenic ingredients (cow's milk, hen's egg, peanut, soybean, hazelnut, and almond) in a chocolate-based matrix. The latter has been produced in a food pilot plant to provide a real and well-characterized matrix for proper assessment of method performance characteristics according to official guidelines. In particular, recent considerations issued by the European Committee for Standardization have been followed to guide a rigorous single-laboratory validation and to feature the main method performance, such as selectivity, linearity, and sensitivity. Synthetic surrogates of the peptide markers have been used both in native and labelled forms in matrix-matched calibration curves as external calibrants and internal standards, respectively. A two-order of magnitude range was investigated, focusing on the low concentration range for proper assessment of the detection and quantification limits (LOD and LOQ) by rigorous calibration approach. Conversion factors for all six allergenic ingredients have been determined for the first time to report the final quantitative information as fraction of total allergenic food protein (TAFP) per mass of food (µgTAFP/gfood), since such areporting unit isexploitable in allergenic risk assessment plans. The method achieved good sensitivity with LOD values ranging between 0.08 and 0.2 µgTAFP/gfood, for all ingredients besides egg and soybean, whose quantitative markers reported a slightly higher limit (1.1 and 1.2 µgTAFP/gfood, respectively). Different samples of chocolate bar incurred at four defined concentration levels close to the currently available threshold doses have been analyzed to test the quantitative performance of the analytical method, with a proper estimate of the measurement uncertainty from different sources of variability. The sensitivity achieved resulted in compliance with the various threshold doses issued or recommended worldwide.

Aptamer-functionalized stir bar sorptive extraction for selective isolation, identification, and determination of concanavalin A in food by MALDI-TOF-MS

An aptamer-functionalized stir bar sorptive extraction (SBSE) coating is described for the first time devoted to selective isolation and preconcentration of an allergenic food protein, concavanalin A (Con A), followed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS) determination. For this purpose, the polytetrafluoroethylene surface of commercial magnetic stir bars was properly modified and vinylized to immobilize a thiol-modified aptamer against Con A via straightforward “thiol-ene” click chemistry. The aptamer-functionalized stir bar was employed as SBSE sorbent to isolate Con A, and several parameters that can affect the extraction efficiency were investigated. Under the optimized conditions, Con A was extracted and desorbed during 30 and 45 min, respectively, at 25 °C and 600 rpm. The SBSE MALDI-TOF-MS method provided limits of detection of 0.5 μg mL−1 for Con A. Furthermore, the SBSE coating was highly selective to Con A compared to other lectins. The developed method was successfully applied to the determination of low levels of Con A in several food matrices (i.e., white beans as well as chickpea, lentils, and wheat flours). Recoveries ranged from 81 to 97% with relative standard deviations below 7%. The aptamer-based stir bars presented suitable physical and chemical long-term stability (1 month) and a reusability of 10 and 5 extraction cycles with standards and food extracts, respectively. The developed aptamer-affinity extraction devices open up the possibility of developing novel highly selective SBSE coatings for the extraction of proteins and peptides from complex samples.Graphical abstract

Molecular Approaches for Food Protein Allergenicity Assessment and the Diagnosis and Treatment of Food Allergies

Food allergy, an adverse immune reaction triggered by commonly innocuous food proteins, is a health problem that affects millions of people worldwide (around 10% of the global population), and the most recent reports suggest its increasing progression [...].

Tackling food allergens-The role of food processing on proteins' allergenicity.

This chapter examines how innovative and emerging food processing technologies, such as those that use heat, electricity, electromagnetic waves, and pressure, can modify protein denaturation, aggregation, and intermolecular interactions pathways, which can result in varying immunoreactive responses. It emphasizes the need to understand how these processing methods affect the protein epitopes recognized by antibodies and their respective priming pathways, especially during the sensitization stage that precedes an allergic response. Although traditional processing methods have been investigated, the impact of novel technologies on food protein allergenicity remains largely unknown. The chapter specifically focuses on milk proteins, which have clinical significance and are associated with cow's milk allergy, one of the most common food allergies in young children. Additionally, it examines potential scientific advancements that novel processing methods may bring to this field.

Allergenic food protein consumption is associated with systemic IgG antibody responses in non-allergic individuals

Although food-directed immunoglobulin E (IgE) has been studied in the context of allergies, the prevalence and magnitude of IgG responses against dietary antigens are incompletely characterized in the general population. Here, we measured IgG binding against food and environmental antigens obtained from allergen databases and the immune epitope database (IEDB), represented in a phage displayed library of 58,233 peptides. By profiling blood samples of a large cohort representing the average adult Israeli population (n= 1,003), we showed that many food antigens elicited systemic IgG in up to 50% of individuals. Dietary intake of specific food protein correlated with antibody binding, suggesting that diet can shape the IgG epitope repertoire. Our work documents abundant systemic IgG responses against food antigens and provides a reference map of the exact immunogenic epitopes on a population scale, laying the foundation to unravel the role of food- and environmental antigen-directed antibody binding in disease contexts.

Expression, purification, characterization, and patient IgE reactivity of new macadamia nut iso-allergen

Structural and functional information about food allergens is essential for understanding the allergenicity of food proteins. All allergens belong to a small number of protein families. Various allergens from different families have been successfully produced recombinantly in E. coli for their characterization and applications in allergy diagnosis and treatment. However, recombinant hexameric 11S seed storage protein has not been reported, although numerous 11S legumins are known to be food allergens, including the recently identified macadamia nut allergen Mac i 2. Here we report the production of a macadamia nut legumin by expressing it in E. coli with a substrate site of HRV 3C protease and cleaving the purified protein with HRV 3C protease. The protease divided the protein into two chains and left a native terminus for the C-terminal chain, resulting in a recombinant hexameric 11S allergen for the first time after the residues upstream to the cleavage site flipped out of the way of the trimer-trimer interaction. The 11S allergens are known to have multiple isoforms in many species. The present study removed an obstacle in obtaining homogeneous allergens needed for studying allergens and mitigating allergenicity. Immunoreactivity of the protein with serum IgE confirmed it to be a new isoform of Mac i 2.

Biochemical and clinical studies of putative allergens to assess what distinguishes them from other non-allergenic proteins in the same family

Many protein families have numerous members listed in databases as allergens; however, some allergen database entries, herein called “orphan allergens”, are members of large families of which all other members are not allergens. These orphan allergens provide an opportunity to assess whether specific structural features render a protein allergenic. Three orphan allergens [Cladosporium herbarum aldehyde dehydrogenase (ChALDH), Alternaria alternata ALDH (AaALDH), and C. herbarum mannitol dehydrogenase (ChMDH)] were recombinantly produced and purified for structure characterization and for clinical skin prick testing (SPT) in mold allergic participants. Examination of the X-ray crystal structures of ChALDH and ChMDH and a homology structure model of AaALDH did not identify any discernable epitopes that distinguish these putative orphan allergens from their non-allergenic protein relatives. SPT results were aligned with ChMDH being an allergen, 53% of the participants were SPT (+). AaALDH did not elicit SPT reactivity above control proteins not in allergen databases (i.e., Psedomonas syringae indole-3-acetaldehyde dehydrogenase and Zea mays ALDH). Although published results showed consequential human IgE reactivity with ChALDH, no SPT reactivity was observed in this study. With only one of these three orphan allergens, ChMDH, eliciting SPT(+) reactions consistent with the protein being included in allergen databases, this underscores the complicated nature of how bioinformatics is used to assess the potential allergenicity of food proteins that could be newly added to human diets and, when needed, the subsequent clinical testing of that bioinformatic assessment.Trial registration number and date of registration AAC-2017-0467, approved as WIRB protocol #20172536 on 07DEC2017 by WIRB-Copernicus (OHRP/FDA Registration #: IRB00000533, organization #: IORG0000432).

Gastrointestinal fate of food allergens and its relationship with allergenicity.

Food allergens are closely related to their gastrointestinal digestion fate, but the changes in food allergens during digestion and related mechanisms are quite complicated. This review presents in detail digestion models for predicting allergenicity, the fates of food allergens in oral, gastric and duodenal digestion, and the applications of digestomics in mapping IgE-binding epitopes of digestion-resistant peptides. Moreover, this review highlights the structure-activity relationships of food allergens during gastrointestinal digestion. Digestion-labile allergens may share common structural characteristics, such as high flexibility, rendering them easier to be hydrolyzed into small fragments with decreased or eliminated allergenicity. In contrast, the presence of disulfide bonds, tightly wound α-helical structures, or hydrophobic domains in food allergens helps them resist gastrointestinal digestion, stabilizing IgE-binding epitopes, thus maintaining their sensitization. In rare cases, digestion leads to increased allergenicity due to exposure of new epitopes. Finally, the action of the food matrix and processing on the digestion and allergenicity of food allergens as well as the underlying mechanisms was overviewed. The food matrix can directly act on the allergen by forming complexes or new epitopes to affect its gastrointestinal digestibility and thereby alter its allergenicity or indirectly affect the allergenicity by competing for enzymatic cleavage or influencing gastrointestinal pH and microbial flora. Several processing techniques attenuate the allergenicity of food proteins by altering their conformation to improve susceptibility to degradation by digestive enzymes. Given the complexity of food components, the food itself rather than a single allergen should be used to obtain more accurate data for allergenicity assessment. PRACTICAL APPLICATION: The review article will help to understand the relationship between food protein digestion and allergenicity, and may provide fundamental information for evaluating and reducing the allergenicity of food proteins.

A new paradigm to search for allergenic proteins in novel foods by integrating proteomics analysis and in silico sequence homology prediction: Focus on spirulina and chlorella microalgae.

Since novel nutrient sources with high protein content, such as yeast, fungi, bacteria, algae, and insects, are increasingly introduced in the consumer market, safety evaluation studies on their potentially allergenic proteins are required. A pipeline for in silico establishing the sequence-based homology between proteins of spirulina (Arthrospira platensis) and chlorella (Chlorella vulgaris) micro-algae and those included in the AllergenOnline (AO) database (AllergenOnline.org) is described. The extracted proteins were first identified through tryptic peptides analysis by reversed-phase liquid chromatography and high resolution/accuracy Fourier-transform tandem mass spectrometry (RPLC-ESI-FTMS/MS), followed by a quest on the UniProt database. The AO database was subsequently interrogated to assess sequence similarity between identified microalgal proteins and known allergens, based on criteria established by the World Health Organization (WHO) and Food and Agriculture Organization (FAO). A direct search for microalgal proteins already included in allergen databases was also performed using the Allergome database. Six proteins exhibiting a significant homology with food allergens were identified in spirulina extracts. Five of them, i.e., two thioredoxins (D4ZSU6, K1VP15), a superoxide dismutase (C3V3P3), a glyceraldehyde-3-phosphate dehydrogenase (K1W168), and a triosephosphate isomerase (D5A635), resulted from the search on AO. The sixth protein, C-phycocyanin beta subunit (P72508), was directly obtained after examining the Allergome database. Two proteins exhibiting significant sequence homology with food allergens were retrieved in chlorella extracts, viz. calmodulin (A0A2P6TFR8), which is related to troponin c (D7F1Q2), and fructose-bisphosphate aldolase (A0A2P6TDD0). Specific serum screenings based on immunochemical tests should be undertaken to confirm or rule out the allergenicity of the identified proteins.

A Novel Photoelectrochemical Immunosensor for Sensitive Detection of Milk α-Lactalbumin Based on CdWO4 –CdS Heterojunction

Cow milk is an important source of protein, but it is also a food that can cause allergies. In this research, a novel photoelectrochemical immunosensor based on CdWO4–CdS type-II heterojunction was constructed for the detection of allergen [Formula: see text]-lactalbumin ([Formula: see text]-Lac) in milk. CdWO4–CdS heterojunction was synthesized by one-step hydrothermal method. Compared with pure CdWO4, the CdWO4–CdS heterojunction significantly improved the photocurrent intensity. The polydopamine (PDA) was used as a crosslinking agent to couple basis materials and biomolecules. Ascorbic acid was used as an efficient electron donor to eliminate the photo-generated holes and inhibit the recombination of photo-generated electrons and holes. Under the optimum experimental conditions, the photocurrent intensity reduced linearly with the logarithm of [Formula: see text]-Lac concentration ranging from 0.001 ng[Formula: see text]mL[Formula: see text] to 10 ng[Formula: see text]mL[Formula: see text] and the limit of detection was 0.17[Formula: see text]pg[Formula: see text]mL[Formula: see text]. The constructed photoelectrochemical immunosensor exhibited excellent stability, selectivity and reproducibility, which provided a novel ideal for sensitive detection of [Formula: see text]-Lac and shed light on monitoring of other allergenic proteins in foods.

Controlling cross‐contamination by food allergens

Controlling cross‐contamination by food allergens

Effect of Processing on Fish Protein Antigenicity and Allergenicity.

Fish allergy is a life-long food allergy whose prevalence is affected by many demographic factors. Currently, there is no cure for fish allergy, which can only be managed by strict avoidance of fish in the diet. According to the WHO/IUIS Allergen Nomenclature Sub-Committee, 12 fish proteins are recognized as allergens. Different processing (thermal and non-thermal) techniques are applied to fish and fishery products to reduce microorganisms, extend shelf life, and alter organoleptic/nutritional properties. In this concise review, the development of a consistent terminology for studying food protein immunogenicity, antigenicity, and allergenicity is proposed. It also summarizes that food processing may lead to a decrease, no change, or even increase in fish antigenicity and allergenicity due to the change of protein solubility, protein denaturation, and the modification of linear or conformational epitopes. Recent studies investigated the effect of processing on fish antigenicity/allergenicity and were mainly conducted on commonly consumed fish species and major fish allergens using in vitro methods. Future research areas such as novel fish species/allergens and ex vivo/in vivo evaluation methods would convey a comprehensive view of the relationship between processing and fish allergy.

Predicting the allergenicity of legume proteins using a PBMC gene expression assay

BackgroundFood proteins differ in their allergenic potential. Currently, there is no predictive and validated bio-assay to evaluate the allergenicity of novel food proteins. The objective of this study was to investigate the potential of a human peripheral blood mononuclear cell (PBMC) gene expression assay to identify biomarkers to predict the allergenicity of legume proteins.ResultsPBMCs from healthy donors were exposed to weakly and strongly allergenic legume proteins (2S albumins, and 7S and 11S globulins from white bean, soybean, peanut, pea and lupine) in three experiments. Possible biomarkers for allergenicity were investigated by exposing PBMCs to a protein pair of weakly (white bean) and strongly allergenic (soybean) 7S globulins in a pilot experiment. Gene expression was measured by RNA-sequencing and differentially expressed genes were selected as biomarkers. 153 genes were identified as having significantly different expression levels to the 7S globulin of white bean compared to soybean. Inclusion of multiple protein pairs from 2S albumins (lupine and peanut) and 7S globulins (white bean and soybean) in a larger study, led to the selection of CCL2, CCL7, and RASD2 as biomarkers to distinguish weakly from strongly allergenic proteins. The relevance of these three biomarkers was confirmed by qPCR when PBMCs were exposed to a larger panel of weakly and strongly allergenic legume proteins (2S albumins, and 7S and 11S globulins from white bean, soybean, peanut, pea and lupine).ConclusionsThe PBMC gene expression assay can potentially distinguish weakly from strongly allergenic legume proteins within a protein family, though it will be challenging to develop a generic method for all protein families from plant and animal sources. Graded responses within a protein family might be of more value in allergenicity prediction instead of a yes or no classification.

A Comparative Analysis of Novel Deep Learning and Ensemble Learning Models to Predict the Allergenicity of Food Proteins.

Traditional food allergen identification mainly relies on in vivo and in vitro experiments, which often needs a long period and high cost. The artificial intelligence (AI)-driven rapid food allergen identification method has solved the above mentioned some drawbacks and is becoming an efficient auxiliary tool. Aiming to overcome the limitations of lower accuracy of traditional machine learning models in predicting the allergenicity of food proteins, this work proposed to introduce deep learning model—transformer with self-attention mechanism, ensemble learning models (representative as Light Gradient Boosting Machine (LightGBM) eXtreme Gradient Boosting (XGBoost)) to solve the problem. In order to highlight the superiority of the proposed novel method, the study also selected various commonly used machine learning models as the baseline classifiers. The results of 5-fold cross-validation showed that the area under the receiver operating characteristic curve (AUC) of the deep model was the highest (0.9578), which was better than the ensemble learning and baseline algorithms. But the deep model need to be pre-trained, and the training time is the longest. By comparing the characteristics of the transformer model and boosting models, it can be analyzed that, each model has its own advantage, which provides novel clues and inspiration for the rapid prediction of food allergens in the future.

Nutritional Factors in the Prevention of Atopic Dermatitis in Children.

Atopic dermatitis is one of the most frequent chronic skin diseases worldwide and often develops within the first few years of life. Recent advancements in our knowledge of its pathophysiology have brought to light the role of genetic predisposition and environmental triggers. With the increasing prevalence of allergic diseases, there is a strong need for a better understanding of the various modifiable eliciting factors of such conditions. The concomitant rise in food allergy and insights into the skin barrier function has highlighted the role of nutrition and diet in the prevention and modification of allergic disorders. Furthermore, the identification of the skin as an important route of sensitization, and the risk of progression to asthma later in life, stress the significance of optimizing our management of skin inflammation in the prevention of allergies. Many nutritional factors, including the type of maternal diet during pregnancy, the duration of breastfeeding, the epicutaneous exposure of allergenic food proteins in the first few years of life, the timing of the introduction of complementary foods, the supplementation of vitamins and probiotics/prebiotics during prenatal and early life, have been assessed as potential targets for the prevention of atopy and eczema. Here, we review the latest data addressing prenatal and perinatal nutritional and dietary interventions in the primary prevention of atopic dermatitis. Also, we define knowledge gaps and targets for future research in the prevention of atopic dermatitis.

Full range of population Eliciting Dose values for 14 priority allergenic foods and recommendations for use in risk characterization

Previously, we published selected Eliciting Dose (ED) values (i.e. ED01 and ED05 values) for 14 allergenic foods, predicted to elicit objective allergic symptoms in 1% and 5%, respectively, of the allergic population (Remington et al., 2020). These ED01 and ED05 values were specifically presented and discussed in the context of establishing Reference Doses for allergen management and the calculation of Action Levels for Precautionary Allergen Labeling (PAL). In the current paper, we publish the full range of ED values for these allergenic foods and provide recommendations for their use, specifically in the context of characterizing risks of concentrations of (unintended) allergenic proteins in food products.The data provided in this publication give risk assessors access to full population ED distribution information for 14 priority allergenic foods, based on the largest threshold database worldwide. The ED distributions were established using broad international consensus regarding suitable datapoints and methods for establishing individual patient's NOAELs and LOAELs and state of the art statistical modelling. Access to these ED data enables risk assessors to use this information for state-of-the-art food allergen risk assessment. This paper contributes to a harmonization of food allergen risk assessment and risk management and PAL practices.

Are Physicochemical Properties Shaping the Allergenic Potency of Plant Allergens?

This review searched for published evidence that could explain how different physicochemical properties impact on the allergenicity of food proteins and if their effects would follow specific patterns among distinct protein families. Owing to the amount and complexity of the collected information, this literature overview was divided in two articles, the current one dedicated to protein families of plant allergens and a second one focused on animal allergens. Our extensive analysis of the available literature revealed that physicochemical characteristics had consistent effects on protein allergenicity for allergens belonging to the same protein family. For example, protein aggregation contributes to increased allergenicity of 2S albumins, while for legumins and cereal prolamins, the same phenomenon leads to a reduction. Molecular stability, related to structural resistance to heat and proteolysis, was identified as the most common feature promoting plant protein allergenicity, although it fails to explain the potency of some unstable allergens (e.g. pollen-related food allergens). Furthermore, data on physicochemical characteristics translating into clinical effects are limited, mainly because most studies are focused on in vitro IgE binding. Clinical data assessing how these parameters affect the development and clinical manifestation of allergies is minimal, with only few reports evaluating the sensitising capacity of modified proteins (addressing different physicochemical properties) in murine allergy models. In vivo testing of modified pure proteins by SPT or DBPCFC is scarce. At this stage, a systematic approach to link the physicochemical properties with clinical plant allergenicity in real-life scenarios is still missing.

Genetically modified foods and food allergy.

Genetic modification of foods is one of the many ways of processing that can enhance foods to increase desirable qualities, such as herbicide tolerance, bacteria and insect resistance, improved nutritional value, and delayed ripening. However, a theoretical potential to increase the allergenicity of food proteins has been the subject of concern from critics. To prevent adverse effects from genetically modified (GM) crops, national and international organizations tightly regulate their production and recommend rigorous safety testing. Some safety tests were developed to assess potential allergenicity by studying the product's similarity to known allergenic proteins, its resistance to pepsin digestion, and its binding to immunoglobulin E (IgE) from sera of patients with known relevant allergies. To date, these safety assessments have only identified rare GM foods with the potential to lead to immunologic reactions. These foods were stopped from being marketed commercially, and the products on the market now have passed required safety assessments. The rise in the prevalence of food allergy preceded the commercialization of GM foods and has also occurred in countries with limited access to GM crops, which highlights a lack of causative association between the two. Several studies provided further reassurance with no evidence of higher potency in specific IgE binding to GM foods. There are no studies that demonstrate adverse reactions due to GM food consumption, and GM foods may have the beneficial potential to silence major allergenic proteins. Therefore, physicians and other health-care professionals should counsel patients that the scientific data do not support an increased risk of allergic responses to GM foods.