Allergic reactions to hydrolysed wheat proteins: clinical aspects and molecular structures of the allergens involved

Application of AllerCatPro 2.0 for protein safety assessments of consumer products

Foreign proteins are potentially immunogenic, and a proportion of these are able to induce immune responses that result in allergic sensitization. Subsequent exposure of sensitized subjects to the inducing protein can provoke a variety of allergic reactions that may be severe, or even fatal. It has therefore been recognized for some time that it is important to determine a priori whether a given protein has the potential to induce allergic responses in exposed subjects. For example, the need to assess whether transgene products expressed in genetically engineered crop plants have allergenic properties. This is not necessarily a straightforward exercise (as discussed elsewhere in this edition), but the task becomes even more challenging when there is a need to conduct an overall allergenicity safety assessment of complex mixtures of proteins in botanicals or other natural sources that are to be used in consumer products. This paper describes a new paradigm for the allergenicity safety assessment of proteins that is based on the use of AllerCatPro 2.0, a new version of a previously described web application model developed for the characterization of the allergenic potential of proteins. Operational aspects of AllerCatPro 2.0 are described with emphasis on the application of new features that provide improvements in the predictions of allergenic properties such as the identification of proteins with high allergenic concern. Furthermore, the paper provides a description of strategies of how AllerCatPro 2.0 can best be deployed as a screening tool for identifying suitable proteins as ingredients in consumer products as well as a tool, in conjunction with label-free proteomic analysis, for identifying and semiquantifying protein allergens in complex materials. Lastly, the paper discusses the steps that are recommended for formal allergenicity safety assessment of novel consumer products which contain proteins, including consideration and integration of predicted consumer exposure metrics. The article therefore provides a holistic perspective of the processes through which effective protein safety assessments can be made of potential allergenic hazards and risks associated with exposure to proteins in consumer products, with a particular focus on the use of AllerCatPro 2.0 for this purpose.

Allergenicity of wheat protein in diet: Mechanisms, modifications and challenges

Wheat is widely available in people's daily diets. However, some people are currently experiencing IgE-mediated allergic reactions to wheat-based foods, which seriously impact their quality of life. Thus, it is imperative to provide comprehensive knowledge and effective methods to reduce the risk of wheat allergy (WA) in food. In the present review, recent advances in WA symptoms, the major allergens, detection methods, opportunities and challenges in establishing animal models of WA are summarized and discussed. Furthermore, an updated overview of the different modification methods that are currently being applied to wheat-based foods is provided. This study concludes that future approaches to food allergen detection will focus on combining multiple tools to rapidly and accurately quantify individual allergens in complex food matrices. Besides, biological modification has many advantages over physical or chemical modification methods in the development of hypoallergenic wheat products, such as enzymatic hydrolysis and fermentation. It is worth noting that using biotechnology to edit wheat allergen genes to produce allergen-free food may be a promising method in the future which could improve the safety of wheat foods and the health of allergy sufferers.

Positive rate of wheat allergens in the Chinese allergic population: a systematic review and meta-analysis

In recent years, the prevalence of allergic diseases has increased significantly, causing great concern, and wheat, as one of the top 8 food allergens, is a common allergy trigger. Nevertheless, reliable estimates of the positivity rate of wheat allergens in the allergic population in China are still lacking. The systematic review and meta-analysis aims to evaluate the positive detection rate of wheat allergens in the Chinese allergic population and further provide a reference for the prevention of allergy. CNKI, CQVIP, WAN-FANG DATA, Sino Med, PubMed, Web of Science, Cochrane Library, and Embase databases were retrieved. Related research and case reports about the positive rate of wheat allergen in the Chinese allergic population published from inception to June 30, 2022, were searched, and meta-analysis was performed using Stata software. The pooled positive rate of wheat allergens and 95% confidence interval were calculated by random effect models, and the publication bias was evaluated using Egger's test. A total of 13 articles were included for the final meta-analysis, in which wheat allergen detection methods involved only serum sIgE testing and SPT assessment. The results showed that the wheat allergen positivity detection rate in Chinese allergic patients was 7.30% (95% CI 5.68-8.92%). Subgroup analysis showed that the positivity rate of wheat allergens was influenced by region, but hardly by age and assessment method. The positive rates of wheat allergy in the population with allergic diseases were 2.74% (95% CI 0.90-4.58%) and 11.47% (95% CI 7.08-15.87%) in southern and northern China, respectively. In particular, the positive rates of wheat allergens were greater than 10% in Shaanxi, Henan and Nei Mongol, all of which belong to the northern region. These results suggest that wheat allergens are an important cause of sensitization in allergic populations from northern China, and therefore attention should be paid to early prevention in high-risk populations.

Cross-reactive epitopes and their role in food allergy

Allergenic cross-reactivity among food allergens complicates the diagnosis and management of food allergy. This can result in many patients being sensitized (having allergen-specific IgE) to foods without exhibiting clinical reactivity. Some food groups such as shellfish, fish, tree nuts, and peanuts have very high rates of cross-reactivity. In contrast, relatively low rates are noted for grains and milk, whereas many other food families have variable rates of cross-reactivity or are not well studied. Although classical cross-reactive carbohydrate determinants are clinically not relevant, α-Gal in red meat through tick bites can lead to severe reactions. Multiple sensitizations to tree nuts complicate the diagnosis and management of patients allergic to peanut and tree nut. This review discusses cross-reactive allergens and cross-reactive carbohydrate determinants in the major food groups, and where available, describes their B-cell and T-cell epitopes. The clinical relevance of these cross-reactive B-cell and T-cell epitopes is highlighted and their possible impact on allergen-specific immunotherapy for food allergy is discussed.

Review article: Diagnosis of coeliac disease: a perspective on current and future approaches

Diagnostics will play a central role in addressing the ongoing dramatic rise in global prevalence of coeliac disease, and in deploying new non-dietary therapeutics. Clearer understanding of the immunopathogenesis of coeliac disease and the utility of serology has led to partial acceptance of non-biopsy diagnosis in selected cases. Non-biopsy diagnosis may expand further because research methods for measuring gluten-specific CD4+ T cells and the acute recall response to gluten ingestion in patients is now relatively straightforward. This perspective on diagnosis in the context of the immunopathogenesis of coeliac disease sets out to highlight current consensus, limitations of current practices, gluten food challenge for diagnosis and the potential for diagnostics that measure the underlying cause for coeliac disease, gluten-specific immunity.

Acid Hydrolysis of Gluten Enhances the Skin Sensitizing Potential and Drives Diversification of IgE Reactivity to Unmodified Gluten Proteins

SCOPE

Personal care products containing hydrolyzed gluten have been linked to spontaneous sensitization through the skin, however the impact of the hydrolysate characteristics on the sensitizing capacity is generally unknown.

METHODS AND RESULTS

The physicochemical properties of five different wheat-derived gluten products (one unmodified, one enzyme hydrolyzed, and three acid hydrolyzed) are investigated, and the skin sensitizing capacity is determined in allergy-prone Brown Norway rats. Acid hydrolyzed gluten products exhibited the strongest intrinsic sensitizing capacity via the skin. All hydrolyzed gluten products induced cross-reactivity to unmodified gluten in the absence of oral tolerance to wheat, but were unable to break tolerance in animals on a wheat-containing diet. Still, the degree of deamidation in acid hydrolyzed products is associated with product-specific sensitization in wheat tolerant rats. Sensitization to acid hydrolyzed gluten products is associated with a more diverse IgE reactivity profile to unmodified gluten proteins compared to sensitization induced by unmodified gluten or enzyme hydrolyzed gluten.

CONCLUSION

Acid hydrolysis enhances the skin sensitizing capacity of gluten and drives IgE reactivity to more gluten proteins. This property of acid hydrolyzed gluten may be related to the degree of product deamidation, and could be a strong trigger of wheat allergy in susceptible individuals.

Creating hypo-/nonallergenic wheat products using processing methods: Fact or fiction?

Wheat allergy is a potentiallylife-threatening disease that affects millions of people around the world. Food processing has been shown to influence the allergenicity of wheat and other major foods. However, a comprehensive review evaluating whether or not food processing can be used to develop hypo-/nonallergenic wheat products is unavailable. There were three objectives for this study: (1) to critically evaluate the evidence on the effect of fermentation, thermal processing, and enzyme or acid hydrolysis on wheat allergenicity so as to identify the potential for and challenges of using these methods to produce hypo-/nonallergenic wheat products; (2) to identify the molecular effects of food processing needed to create such products; and (3) to map the concept questions for future research and development to produce hypo-/nonallergenic wheat products. We performed literature research using PubMed and Google Scholar databases with various combinations of keywords to generate the data to accomplish these objectives. We found that: (1) food processing significantly modulates wheat allergenicity; while some methods can reduce or even abolish the allergenicity, others can create mega allergens; and (2) fermentation and enzymatic hydrolysis hold the most potential to create novel hypo-/nonallergenic wheat products; however, preclinical validation and human clinical trials are currently lacking. We also identify five specific research concepts to advance the research to enable the creation of hypo-/nonallergenic wheat products for application in food, medical, and cosmetic industries.

l-Arabinose Attenuates Gliadin-Induced Food Allergy via Regulation of Th1/Th2 Balance and Upregulation of Regulatory T Cells in Mice

Gliadins are the main cause of wheat allergies, and the prevalence of gliadin allergy has increased in many countries. l-Arabinose, a kind of plant-specific five-carbon aldose, possesses beneficial effects on food allergy to gliadins. This study investigated the antiallergic activities and underlying mechanisms of l-arabinose in a wheat gliadin-sensitized mouse model. BALB/c mice were sensitized to gliadin by intraperitoneal injections with gliadin followed by being given a gliadin challenge. l-arabinose-treated mice exhibited a marked reduction in the productions of total immunoglobulin E (IgE), gliadin-specific IgE, gliadin-specific IgG1, and histamine, with an increase in IgG2a level as compared with gliadin-sensitized mice. Beside that, a significant decrease in Th2-related cytokine level, IL-4, and an increase in Th1-related cytokine level, IFN-γ, in the serum and splenocytes were observed after treatment with l-arabinose. l-Arabinose treatment also improved the imbalance of Th1/Th2 immune response on the basis of the expression levels of related cytokines and key transcription factors in the small intestine and spleen of sensitized mice. In addition, gliadin-induced intestinal barrier impairment was blocked by l-arabinose treatment via regulation of TJ proteins and suppression of p38 MAPK and p65 NF-κB inflammation signaling pathways. Notably, the results confirmed that l-arabinose treatment increased CD4⁺ Foxp3⁺ T cell populations and Treg-related factors associated with increased expression of IL-2 and activation of STAT5 in gliadin-sensitized mice. In conclusion, l-arabinose attenuated the gliadin-induced allergic symptoms via maintenance of Th1/Th2 immune balance and regulation of Treg cells in a gliadin-induced mouse model, suggesting l-arabinose could be used as a promising agent to alleviate gliadin allergy.

From Polyclonal Sera to Recombinant Antibodies: A Review of Immunological Detection of Gluten in Foodstuff

Gluten is the ethanol-soluble protein fraction of cereal endosperms like wheat, rye, and barley. It is widely used in the food industry because of the physical-chemical properties it gives to dough. Nevertheless, there are some gluten-related diseases that are presenting increasing prevalences, e.g., celiac disease, for which a strict gluten-free diet is the best treatment. Due to this situation, gluten labeling legislation has been developed in several countries around the world. This article reviews the gluten immune detection systems that have been applied to comply with such regulations. These systems have followed the development of antibody biotechnology, which comprise three major methodologies: polyclonal antibodies, monoclonal antibodies (mAbs) derived from hybridoma cells (some examples are 401.21, R5, G12, and α-20 antibodies), and the most recent methodology of recombinant antibodies. Initially, the main objective was the consecution of new high-affinity antibodies, resulting in low detection and quantification limits that are mainly achieved with the R5 mAb (the gold standard for gluten detection). Increasing knowledge about the causes of gluten-related diseases has increased the complexity of research in this field, with current efforts not only focusing on the development of more specific and sensitive systems for gluten but also the detection of protein motifs related to pathogenicity. New tools based on recombinant antibodies will provide adequate safety and traceability methodologies to meet the increasing market demand for gluten-free products.

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.

Allergenicity of Fermented Foods: Emphasis on Seeds Protein-Based Products

Food allergy is an IgE-mediated abnormal response to otherwise harmless food proteins, affecting between 5% and 10% of the world preschool children population and 1% to 5% adults. Several physical, chemical, and biotechnological approaches have been used to reduce the allergenicity of food allergens. Fermentation processes that contribute to technological and desirable changes in taste, flavor, digestibility, and texture of food products constitute one of these approaches. Lactic acid bacteria (LAB), used as starter cultures in dairy products, are a subject of increasing interest in fermentation of plant proteins. However, the studies designed to assess the impact of LAB on reduction of allergenicity of seed proteins are at an early stage. This review presents the current knowledge on food fermentation, with a focus on seed proteins that are increasingly used as ingredients, and its impacts on food potential allergenicity.

Deamidation and Enzymatic Hydrolysis of Gliadins Alter Their Processing by Dendritic Cells in Vitro

Gliadins are major wheat allergens. Their treatment by acid or enzymatic hydrolysis has been shown to modify their allergenic potential. As the interaction of food proteins with dendritic cells (DCs) is a key event in allergic sensitization, we wished to investigate whether deamidation and enzymatic hydrolysis influence gliadin processing by DC and to examine the capacity of gliadins to activate DCs. We compared the uptake and degradation of native and modified gliadins by DCs using mouse bone marrow-derived DCs. We also analyzed the effects of these interactions on the phenotypes of DCs and T helper (Th) lymphocytes. Modifying gliadins induced a change in physicochemical properties (molecular weight, hydrophobicity, and sequence) and also in the peptide size. These alterations in turn led to increased uptake and intracellular degradation of the proteins by DCs. Native gliadins (NGs) (100 μg/mL), but not modified gliadins, increased the frequency of DC expressing CD80 (15.41 ± 2.36% vs 6.81 ± 1.10%, p < 0.001), CCR7 (28.53 ± 8.17% vs 17.88 ± 2.53%, p < 0.001), CXCR4 (70.14 ± 4.63% vs 42.82 ± 1.96%, p < 0.001), and CCR7-dependent migration (2.46 ± 1.45 vs 1.00 ± 0.22, p < 0.01) compared with NGs. This was accompanied by Th lymphocyte activation (30.37 ± 3.87% vs 21.53 ± 3.14%, p < 0.1) and proliferation (16.39 ± 3.97% vs 9.31 ± 2.80%, p > 0.1). Moreover, hydrolysis decreases the peptide size and induces an increase in gliadin uptake and degradation. Deamidation and extensive enzymatic hydrolysis of gliadins modify their interaction with DCs, leading to alteration of their immunostimulatory capacity. These findings demonstrate the strong relationship between the biochemical characteristics of proteins and immune cell interactions.