The Seed Biotinylated Protein of Soybean (Glycine max): A Boiling-Resistant New Allergen (Gly m 7) with the Capacity To Induce IgE-Mediated Allergic Responses

Food allergy - New risks through vegan diet? Overview of new allergen sources and current data on the potential risk of anaphylaxis

A vegan diet is increasingly en vogue, i.e., a diet based on plants, in which animal products are completely avoided, often for health and environmental reasons. The menu is supplemented with pulses (e.g., soy, lentils, peas), nuts (e.g., cashew, macadamia, almond, pecan, para, walnut) and seeds (e.g., chia, flaxseed) or pseudo-grains (quinoa, buckwheat). Indeed, the product range is expanding to include vegan foods such as milk alternatives (e.g., oat, almond, soy drinks) and cheese or meat substitutes (e.g., soy-based). Food allergies are also on the rise, with an increasing prevalence worldwide. It is worthy of note that the main allergens of anaphylactic reactions to food in adults are predominantly of plant origin, mainly pulses and nuts - the very foods that form the main source of protein in the vegan diet. In this context, allergies to storage proteins (e.g., Gly m 5 and Gly m 6 from soya beans) can lead to severe anaphylactic reactions, while highly processed substitute products containing plant protein isolates (e.g., pea flour) in concentrated form continue to be of particular concern and may therefore be allergologically problematic. In this article, we aim to provide an overview of allergens and emerging allergen sources in vegan foods and highlight the anaphylaxis risk of the vegan diet.

Nahrungsmittelallergie - Neue Risiken durch vegane Ernährung? Überblick zu neuen Allergenquellen und aktuelle Daten zum Anaphylaxierisiko: Food allergy - New risks through vegan diet? Overview of new allergen sources and current data on the potential risk of anaphylaxis

Zunehmend mehr Menschen ernähren sich aus gesundheitlichen und Umweltaspekten ausschließlich von pflanzlichen Nahrungsmitteln (vegan). Dabei werden vielfach Hülsenfrüchte (wie Soja, Linsen, Erbsen), Schalenfrüchte (Cashew, Macadamia, Mandel, Pekan‐, Para‐ und Walnuss), Samen und Saaten (wie Chia, Leinsamen) oder (Pseudo‐)Getreide (wie Quinoa, Buchweizen) verzehrt. Vegane Milchalternativen sind Hafer‐, Mandel‐ und Sojadrinks, auch Käse‐ sowie Fleischersatzprodukte basieren oft auf einer Sojagrundlage. Gleichzeitig nimmt die Prävalenz von Nahrungsmittelallergien weltweit zu. Pflanzenallergene aus Hülsen‐ und Schalenfrüchten, die in der veganen Ernährung die Hauptproteinquelle ausmachen, zählen zu den häufigsten Auslösern von Nahrungsmittelallergien bei Erwachsenen. Dabei kommt es bei Allergien auf Speicherproteine (wie Gly m 5 und Gly m 6 aus der Sojabohne) zu teils schweren anaphylaktischen Reaktionen. Besonderes Augenmerk liegt weiter auf hochverarbeiteten Ersatzprodukten, die Pflanzenproteinisolate (zum Beispiel Erbsenmehl) in konzentrierter Form enthalten und damit allergologisch problematisch werden können. In diesem Artikel geben wir einen Überblick über wichtige Allergene und neue Allergenquellen in ausgesuchten veganen Nahrungsmitteln und betrachten die vegane Ernährung unter allergologischen Aspekten.

Comparison of proanthocyanidins A2 and B2 on IgE-reactivity and epitopes in Gly m 6 using multispectral, LC/MS-MS and molecular docking

This study comparatively analyzed the changes in IgE-reactivity and epitopes in proanthocyanidins A2- (PA-Gly m 6) and B2-Gly m 6 (PB-Gly m 6) conjugates prepared by alkali treatment at 80 °C for 20 min. Similar to the western blot, ELISA also showed a higher reduced IgE-reactivity in PA-Gly m 6 (70.12 %) than PB-Gly m 6 (63.17 %). SDS-PAGE demonstrated that proanthocyanidins A2 caused more formation of >180 kDa polymers than proanthocyanidins B2. Multispectral analyses revealed that PA-Gly m 6 exhibited more structural alteration (e.g., a decrease of α-helical content and ANS fluorescence intensity) to unfold protein structure than proanthocyanidins B2, improving the accessibility to modify Gly m 6 for shielding or destroying conformational epitopes. LC/MS-MS revealed that PA-Gly m 6 conjugates had a lower abundance of allergens, peptides and linear epitopes than PB-Gly m 6 conjugates. Molecular docking showed that proanthocyanidins A2 and B2 reacted with Gln-317 and Asn-94 of epitopes, respectively. Overall, proanthocyanidins A2 is more effective than proanthocyanidins B2 to decrease the IgE-reactivity of Gly m 6 due to more shielding or destruction of conformational epitopes and lower content allergens and linear epitopes, which was attributed to more protein-crosslinks formation and structural changes in PA-Gly m 6 conjugates.

ELISA Based Immunoreactivity Reduction of Soy Allergens through Thermal Processing

Allergens are proteins and are, therefore, likely to be denatured when subjected to thermal treatment. Traditional cooking has so far been able to reduce allergen sensitivity by around 70–90%. This study was aimed at evaluating the effect of a broad range of thermal treatments on the reduction of soy immunoreactivity (IR) in a 5% slurry using a sandwich ELISA technique. Cooking at 100 °C (10–60 min) and different thermal processing conditions, such as in commercial sterilization (with a process lethality (Fo) between 3 and 5 min) and selected severe thermal processing conditions (Fo > 5 and up to 23 min) were used in the study to evaluate their influence on allergen IR. Based on an IR comparison with an internal soy allergen standard, the allergen concentration in the untreated soy sample was calculated to be equivalent to 333 mg/kg (ppm). Cooking conditions only reduced the IR sensitivity to about 10 mg/kg (~1.5 log reductions), while the thermal processing treatments lowered the allergen IR up to 23 × 10−3 mg/kg (or 23 ppb) (>4 log reductions). FTIR analysis indicated significant changes in protein structure resulting from the thermal processing treatments, with a higher degree of allergen reduction corresponding with a higher value of random coil percentages. The influence of process severity on color and rheological properties was, however, minimal.

Hydrolysis of Soybean Milk Protein by Papain: Antioxidant, Anti-Angiotensin, Antigenic and Digestibility Perspectives

The objective of the investigation was to understand the biochemical activities of hydrolysate of soybean milk protein (SMP). Hydrolysis was carried out by different concentrations of papain (0.008 g·L⁻¹, 0.016 g·L⁻¹, 0.032 g·L⁻¹ and 0.064 g·L⁻¹). The antioxidant capacity was measured by the ferric-reducing ability of plasma (FRAP) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assays. The anti-angiotensin activity of hydrolysate was measured by the recombinant angiotensin converting enzyme and substrate Abz-FRK(Dnp)-P. The contributions of the Kunitz trypsin inhibitor (KTI) and Bowman–Birk inhibitor (BBI) on antigenicity, and the in vitro digestion of papain-hydrolyzed SMP were studied. Rabbit polyclonal anti-KTI and anti-BBI antibodies together with peroxidase-labelled goat anti-Rb IgG secondary antibody were used to identify the antigenicity of KTI and BBI in unhydrolyzed and papain-hydrolyzed SMP. The antioxidant capacity and anti-angiotensin activity of SMP were increased after the papain hydrolysis of SMP. The KTI- and BBI-specific antigenicity were reduced in SMP by increasing the concentration of papain. However, there was interaction between papain-hydrolyzed SMP and trypsin in native gel, while interaction with chymotrypsin was absent. The interaction between trypsin and SMP was reduced due to the hydrolysis of papain in a concentration-dependent manner. According to the in vitro gastrointestinal digestion simulation protocol (Infogest), the digestibility of SMP was not statistically increased.

Role of selenium in IgE mediated soybean allergy development

Food allergy is a pathological immune reaction triggered by normal innocuous dietary proteins. Soybean is widely used in many food products and has long been recognized as a source of high-quality proteins. However, soybean is listed as one of the 8 most significant food allergens. The prevalence of soybean allergy is increasing worldwide and impacts the quality of life of patients. Currently, the only strategy to manage food allergy relies on strict avoidance of the offending food. Nutritional supplementation is a new prevention strategy which is currently under evaluation. Selenium (Se), as one of the essential micronutrients for humans and animals, carries out biological effects through its incorporation into selenoproteins. The use of interventions with micronutrients, like Se, might be an interesting new approach. In this review we describe the involvement of Se in a variety of processes, including maintaining immune homeostasis, preventing free radical damage, and modulating the gut microbiome, all of which may contribute to in both the prevention and treatment of food allergy. Se interventions could be an interesting new approach for future treatment strategies to manage soybean allergy, and food allergy in general, and could help to improve the quality of life for food allergic patients.

Detection and Characterization of the Soybean Allergen Gly m 7 in Soybeans and Processed Soybean Foods

Gly m 7, a novel soybean allergen, was recently reported. In this study, we attempted to detect Gly m 7 in various soybeans and processed soybean foods using raised anti-Gly m 7 antibodies and enzyme-linked streptavidin, specifically binding to the biotin moiety of Gly m 7. There was a large difference in Gly m 7 levels in various soybean-processed foods. When Gly m 7 levels were determined, all cultivars contained this allergen almost completely, but the biotin moiety detected by streptavidin varied, suggesting that biotinylated levels of Gly m 7 might differ among cultivars. The thermal stability of Gly m 7 was determined by heating soybean extracts. During detection using anti-peptide antibodies, detectable intact Gly m 7 was gradually reduced by heating. Gly m 7 was not detected by peptide or biotin detection in worm-wounded soybeans. Soybeans were immersed in distilled water as a pretreatment step for germination, and Gly m 7 levels were compared by immersion time (4–96 h). Intact Gly m 7 was rapidly degraded in detection by both peptide and biotin moieties. This suggested that Gly m 7 was degraded by some protease(s) during germination. These results would be useful for understanding the properties or risk assessment of Gly m 7, a newly discovered soybean allergen.

Human-Soybean Allergies: Elucidation of the Seed Proteome and Comprehensive Protein-Protein Interaction Prediction

The soybean crop, Glycine max (L.) Merr., is consumed by humans, Homo sapiens, worldwide. While the respective bodies of literature and -omics data for each of these organisms are extensive, comparatively few studies investigate the molecular biological processes occurring between the two. We are interested in elucidating the network of protein-protein interactions (PPIs) involved in human-soybean allergies. To this end, we leverage state-of-the-art sequence-based PPI predictors amenable to predicting the enormous comprehensive interactome between human and soybean. A network-based analytical approach is proposed, leveraging similar interaction profiles to identify candidate allergens and proteins involved in the allergy response. Interestingly, the predicted interactome can be explored from two complementary perspectives: which soybean proteins are predicted to interact with specific human proteins and which human proteins are predicted to interact with specific soybean proteins. A total of eight proteins (six specific to the human proteome and two to the soy proteome) have been identified and supported by the literature to be involved in human health, specifically related to immunological and neurological pathways. This study, beyond generating the most comprehensive human-soybean interactome to date, elucidated a soybean seed interactome and identified several proteins putatively consequential to human health.

Comparison of Various Soybean Allergen Levels in Genetically and Non-Genetically Modified Soybeans

Several analyses of allergen levels have been reported as part of the safety assessment of genetically modified (GM) soybean; however, few comprehensive analyses have included new allergens. Thus, in this study the levels of eight major soybean allergens, including Gly m 7 (a newly reported soybean allergen), were semi-quantitatively detected in six GM soybeans and six non-GM soybeans using antigen-immobilized ELISA and immunoblotting. We also analyzed the IgE-reactivity to these soybeans through immunoblotting, using sera from three soybean-allergic patients. The results showed that there were no significant differences in the levels of the major soybean allergens in the GM and non-GM soybeans. Moreover, there were no significant differences in the serum IgE-reactive protein profiles of the patients, as analyzed using immunoblotting. These results indicate that, in general, CP4-EPSPS-transfected GM soybeans are not more allergenic than non-GM soybeans.

Simplified Tracking of a Soy Allergen in Processed Food Using a Monoclonal Antibody-Based Sandwich ELISA Targeting the Soybean 2S Albumin Gly m 8

Soybean allergens in food samples are currently detected in most cases using enzyme-linked immunosorbent assays (ELISAs) based on antibodies raised against bulk soybean proteins or specifically targeting soybean trypsin inhibitor, conglycinin, or glycinin. The various commercial ELISAs lack standardized reference material, and the results are often inaccurate because the antibodies cross-react with proteins from other legumes. Furthermore, the isolation of allergenic proteins involves laborious denaturing extraction conditions. To tackle these challenges, we have developed a novel sandwich ELISA based on monoclonal antibodies raised against the soybean 2S albumin Gly m 8 and a recombinant Gly m 8 reference protein with native-analogous characteristics. The antibodies do not cross-react with other legume proteins, and the extraordinary stability and solubility of Gly m 8 allows it to be extracted even from complex matrices after processing. The Gly m 8 ELISA therefore achieves greater specificity and reproducibility than current ELISA tests.

Anti-allergic activity of mung bean (Vigna radiata (L.) Wilczek) protein hydrolysates produced by enzymatic hydrolysis using non-gastrointestinal and gastrointestinal enzymes

Mung bean seed is a well-known plant protein consumed in Asian countries but the protein is usually retrieved as a waste product during starch production. This study investigated the anti-allergic property of mung bean protein hydrolysates (MBPH) produced by enzymatic hydrolysis using non-gastrointestinal (non-GI), GI and a combination of non-GI+GI enzymes. The hydrolysates were investigated for any anti-allergic property by detecting the amount of β-hexosaminidase released in RBL-2H3 cells, and complemented with the MTT assay to show cell viability. It was found that MBPH hydrolyzed by a combination of flavourzyme (non-GI enzyme) and pancreatin (GI enzyme) exhibited the highest anti-allergic activity (135.61%), followed by those produced with alcalase, a non-GI enzyme (121.74%) and 80.32% for pancreatin (GI enzyme). Minimal toxicity (<30%) of all hydrolysates on RBL-2H3 cells line was observed. The results suggest that MBPH can potentially serve as a hypoallergenic food ingredient or supplement. PRACTICAL APPLICATIONS: Mung bean (Vigna radiata L. (Wilczek)) is also known as "green gram" and it is an excellent source of protein. The major mung bean storage proteins are the globulin, albumin and legumin, which are also referred to as legume allergens. Our study showed that mung bean peptides obtained after enzymatic hydrolysis influenced β-hexosaminidase inhibition without any toxic effect on RBL-2H3 cells. This indicates that mung bean allergenicity can be reduced after enzymatic hydrolysis and the protein hydrolysates could be as a hypoallergic food, ingredient, supplement and/or protein substitute in the formulation of food products.

Investigation of the interaction of allergens of Glycine max with IgE-antibody for designing of peptidomimetics based anti-allergen

Allergen induced IgE dependent type I hypersensitivity is the main cause of the allergy, which would be a burden on medical setup in coming years. Allergens of Glycine max have been isolated, and their disease relationships are documented. Therefore, it becomes important to investigate the interaction of different allergens of Glycine max with IgE and also screen suitable therapeutics to prevent this interaction. The amino acid sequences of all allergens of Glycine max and their isoallergens have been taken, and 3D structure of allergens (Gly m 3, Gly m 4, Gly m 5, Gly m 6 and Gly m 8) and their isoallergens were generated using Modeller v9.17. The modeled structures were further validated using PSVS, ProSA, RAMPAGE, and PDBsum. HL domain of Fab region of human IgE (PDBID: 2R56) was generated using UCSFchimera. The HL domain was minimized by Schrodinger software using the OPLS_2005 force field. SiteMap identified epitope binding site of the minimized domain. All the predicted epitopes of different allergens were docked to the binding site of HL domain using the Patchdock server. We have also designed a peptidomimetics based inhibitor targeted at interaction interface of Gly m8 and IgE, using in-silico virtual screening, molecular mechanics, and molecular dynamics simulation studies. These studies identified BDE32166344 ((N-(1-{[1-(1-aminocyclopentanecarbonyl)-3-hydroxypyrrolidin-3-yl]methyl}piperidin-4-yl)acetamide) as a peptidomimetics based lead with binding energy of -72.77 kcal/mol. Therefore, the present study investigates the interaction between different Gly m allergens and IgE antibody and identifies peptidomimetics based lead that might be developed as a suitable therapeutics against allergy caused by allergen of Glycine max.

Combining 2-DE immunoblots and mass spectrometry to identify putative soybean (Glycine max) allergens

Soybean is recognized as a commonly allergenic food, but the identity of important allergens is not well studied. Recently, some global regulatory agencies started requiring quantitative analysis of individual allergens, including unproven allergens, as part of the risk assessment for genetically engineered (GE) soybeans. We sought to identify soybean proteins that bind IgE from any of 10 individual soybean-sensitized subjects. Soybean IgE binding proteins were identified by 2-DE immunoblots using sera from four soy-allergic and plasma from six soy-sensitized human subjects. Corresponding spots were excised from stained gels, digested, and analyzed using a quadrupole TOF Synapt G2-S tandem mass spectrometer. Results showed the major IgE binding proteins were subunits of either β-conglycinin (Gly m 5) or glycinin (Gly m 6). Soybean Kunitz trypsin inhibitor (SKTI) was a significant IgE binding protein for four subjects. Soybean agglutinin, seed biotinylated protein (SBP) of 65 kDa, late embryogenesis protein (LEP), and sucrose-binding protein were identified as IgE binding only for soy-sensitized subjects. We conclude that the major soybean allergens are isoforms of Gly m 5, Gly m 6, and possibly SKTI and that requirements for quantitative measurement of proteins that are not clear allergens is not relevant to safety.

Effects of daily food processing on allergenicity

Daily food processing has the potential to alter the allergenicity of foods due to modification of the physico-chemical properties of proteins. The degree of such modifications depends on factors such as processing conditions, type of food considered, allergenic content, etc. The impact of daily food processing like boiling, roasting, frying or baking on food allergenicity have been extensively studied. The influence of other thermal treatments such as microwave heating or pressure cooking on allergenicity has also been analyzed. Non-thermal treatment such as peeling impacts on the allergenic content of certain foods such as fruits. In this review, we give an updated overview of the effects of daily processing treatments on the allergenicity of a wide variety of foods. The different variables that contribute to the modification of food allergenicity due to processing are also reviewed and discussed.

Soluble Sugar Accumulation Can Influence Seed Size via AN3-YDA Gene Cascade

In higher plants, seed size is central to many aspects in evolutionary fitness and is a crucial agricultural trait. In this study, Arabidopsis an3 (angustifolia3) mutants present with increased seed size. Target-gene analysis revealed that YDA, which encodes a mitogen-activated protein kinase kinase kinase, is a target gene of AN3. Indeed, the loss of YDA function decreases seed size. Furthermore, AN3 and YDA mutations both disrupt normal sucrose and glucose contents and cause altered seed size in an3 or yda mutants. With these results, we provide a molecular model in which soluble sugar accumulation might affect seed size regulation via the AN3-YDA gene cascade. Our findings guide the synthesis of a model that predicts the integration of soluble sugar accumulation at AN3 to control the establishment of seed size.

Assessment of endogenous allergenicity of genetically modified plants exemplified by soybean - Where do we stand?

According to EU regulation, genetically modified (GM) plants considered to be allergenic have to be assessed concerning their endogenous allergens before placement on the EU market, in line with the international standards described in Codex Alimentarius. Under such premises, a quantitative relevant increase in allergens might occur in GM plants as an unintended effect compared with conventionally produced crops, which could pose a risk to consumers. Currently, data showing a connection between dose and allergic sensitisation are scarce since the pathophysiological mechanisms of sensitisation are insufficiently understood. In contrast, data on population dose-distribution relationships acquired by oral food challenge are available showing a connection between quantity of allergenic protein consumed and the population of allergic individuals experiencing reactions. Soybean is currently the only recognised allergenic GM food by law for which EFSA has received applications and was therefore taken as an example for defining an assessment strategy. Identification of potential allergens, methodology for quantification as well as risk assessment considerations, are discussed. A strategy is proposed for the identification, assessment and evaluation of potential hazards/risks concerning endogenous allergenicity in food derived from plants developed by biotechnology. This approach could be expanded to other allergenic foods in the future, whenever required.

Kinetic Stability of Proteins in Beans and Peas: Implications for Protein Digestibility, Seed Germination, and Plant Adaptation

Kinetically stable proteins (KSPs) are resistant to the denaturing detergent sodium dodecyl sulfate (SDS). Such resilience makes KSPs resistant to proteolytic degradation and may have arisen in nature as a mechanism for organismal adaptation and survival against harsh conditions. Legumes are well-known for possessing degradation-resistant proteins that often diminish their nutritional value. Here we applied diagonal two-dimensional (D2D) SDS-polyacrylamide gel electrophoresis (PAGE), a method that allows for the proteomics-level identification of KSPs, to a group of 12 legumes (mostly beans and peas) of agricultural and nutritional importance. Our proteomics results show beans that are more difficult to digest, such as soybean, lima beans, and various common beans, have high contents of KSPs. In contrast, mung bean, red lentil, and various peas that are highly digestible contain low amounts of KSPs. Identified proteins with high kinetic stability are associated with warm-season beans, which germinate at higher temperatures. In contrast, peas and red lentil, which are cool-season legumes, contain low levels of KSPs. Thus, our results show protein kinetic stability is an important factor in the digestibility of legume proteins and may relate to nutrition efficiency, timing of seed germination, and legume resistance to biotic stressors. Furthermore, we show D2D SDS-PAGE is a powerful method that could be applied for determining the abundance and identity of KSPs in engineered and wild legumes and for advancing basic research and associated applications.

Mass Spectrometric Analysis of N-Glycoforms of Soybean Allergenic Glycoproteins Separated by SDS-PAGE

Glycosylation of many proteins has been revealed to be closely related with food allergies, and screening and structural analysis of related glycoproteins and glycoallergens are essential for studies in this field. Herein, we describe detailed N-glycoform analysis of all glycoprotein fractions of soybean protein isolate (SPI) separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to disclose structural features of the glycan moieties of more soybean glycoproteins. SPI was fractionated by SDS-PAGE, and the generated protein bands were recovered and subjected to in-gel N-glycan release and labeling using a one-pot method newly developed by our group, followed by detailed analysis by electrospray ionization mass spectrometry (ESI-MS) and online hydrophilic interaction liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HILIC-ESI-MS/MS). As a result, we found seven bands mainly containing oligomannose-type glycans; two mainly contain core α1,3-fucosylated glycans, and six have no glycans. This study is the first report that discovers core α1,3-fucosylated N-glycans in bands 1, 2, and 6 and discloses bands 3, 4, 5, and 7 as glycoproteins and their N-glycoforms. Therefore, it can expand our knowledge about soybean protein glycosylation and provide significant structural reference for research of soybean allergens.