Molecular cloning, recombinant expression and IgE-binding epitope of omega-5 gliadin, a major allergen in wheat-dependent exercise-induced anaphylaxis

Identification of RNAi hypoallergic bread wheat lines for wheat-dependent exercise-induced anaphylaxis patients

Wheat-dependent exercise-induced anaphylaxis (WDEIA) is one of the most severe forms of wheat allergy. It occurs in patients when they exercise after ingesting wheat-containing foods. Nowadays, the only possible alternative for WDEIA patients is to avoid such foods. This study investigated the potential of six RNA of interference (RNAi) wheat lines with low-prolamin content as alternatives for WDEIA patients. For that purpose, a high performance-liquid chromatography (HPLC) analysis was performed to evaluate differences in gluten protein fractions among these lines. Next, western blots were conducted to measure the immunoglobulin E (IgE) reactivity to wheat proteins in sera from five WDEIA patients. Additionally, monoclonal antibodies (moAb) recognition sites and the IgE binding sites were searched in all peptides identified by LC-MS/MS after protein digestion. The results showed a 61.4%-81.2% reduction in the gliadin content of the RNAi lines, accompanied by an increase in their high-molecular weight (HMW) glutenin content compared to the wild type bread wheat line (WT). In all cases, the reduction in gliadin content correlated with a decrease in IgE reactivity observed in the sera of WDEIA patients, highlighting the E82 and H320 lines. These two RNAi lines exhibited a ≤90% reduction in IgE reactivity. This reduction could be attributed to an absence of IgE binding sites associated with α- and ω5-gliadins, which were present in the WT. Overall, these lines offer a potential alternative for foodstuff for individuals with WDEIA.

Low Allergenicity in Processed Wheat Flour Products Using Tannins from Agri-Food Wastes

The present study aimed to investigate the effect of the addition of tannins from unutilized resources on wheat allergen reduction, antioxidant properties, and quality by substituting 3%, 5%, and 10% of the flour with chestnut inner skin (CIS) and young persimmon fruit (YPF) powders to produce cookies. The enzyme-linked immunosorbent assay and Western blotting showed significantly lower wheat allergen content in CIS- or YPF-substituted cookies than in control cookies, and this effect was pronounced for CIS-substituted cookies. In addition, the tannin content and antioxidant properties of the CIS- or YPF-substituted cookies were markedly higher than those of the control cookies. Quality analysis of the CIS- and YPF-substituted cookies showed that the specific volume and spread factor, which are quality indicators for cookies, were slightly lower in the CIS- and YPF-substituted cookies than in the control cookies. Compared to the control, CIS substitution did not affect the breaking stress and total energy values of the cookies; however, YPF substitution at 10% increased these values. Color was also affected by the addition of CIS and YPF. The results suggest that the addition of CIS and YPF can reduce wheat allergens in cookies and improve tannin content and antioxidant properties.

A Narrative Mini Review on Current Status of Hypoallergenic Wheat Development for IgE-Mediated Wheat Allergy, Wheat-Dependent Exercise-Induced Anaphylaxis

Immunoglobulin E (IgE)-mediated food allergies to wheat that develop after school age typically shows a type of wheat-dependent exercise-induced anaphylaxis (WDEIA). At present, avoidance of wheat products or postprandial rest after ingesting wheat is recommended for patients with WDEIA, depending on the severity of the allergy symptoms. ω5-Gliadin has been identified as the major allergen in WDEIA. In addition, α/β-, γ-, and ω1,2-gliadins, high and low molecular weight-glutenins, and a few water-soluble wheat proteins have been identified as IgE-binding allergens in a small proportion of patients with IgE-mediated wheat allergies. A variety of approaches have been manufactured to develop hypoallergenic wheat products that can be consumed by patients with IgE-mediated wheat allergies. In order to analyze such approaches, and to contribute to the further improvement, this study outlined the current status of these hypoallergenic wheat productions, including wheat lines with a reduced allergenicity that are mostly constructed for the patients sensitized to ω5-gliadin, hypoallergenic wheat by enzymic degradation/ion exchanger deamidation, and hypoallergenic wheat by thioredoxin treatment. The wheat products obtained by these approaches significantly reduced the reactivity of Serum IgE in wheat-allergic patients. However, either these were not effective on some populations of the patients, or low-level IgE-reactivity to some allergens of the products was observed in the patients. These results highlight some of the difficulties faced in creating hypoallergenic wheat products or hypoallergenic wheat lines through either traditional breeding or biotechnology approaches in developing hypoallergenic wheat completely safe for all the patients allergic to wheat.

In Vitro Effect of Flavonoids on Basophils Degranulation and Intestinal Epithelial Barrier Damage Induced by ω-5 Gliadin-Derived Peptide

Flavonoids have antioxidant, anti-inflammatory and immunomodulatory properties, and may alleviate food allergic reactions and intestinal inflammation induced by ω-5 gliadin, a main allergen of wheat food allergy in children. In this study, a human basophil KU812 cell degranulation model and a Caco-2 monolayer cell model were constructed in vitro to evaluate the effects of four flavonoids on the allergenicity of ω-5 gliadin peptides and ω-5 gliadin peptide-induced barrier damage in Caco-2 intestinal epithelial monolayers. The results show that baicalein, luteolin, isorhamnetin and naringenin can significantly inhibit the degranulation of KU812 cells stimulated by ω-5 gliadin-derived peptide P4 and the release of IL-6 and TNF-α. In addition, the four flavonoids significantly inhibited the ω-5 gliadin-derived peptide P4 to induce the release of IL-6, IL-8 in Caco-2 cells, inhibited the release of zonulin, and significantly increase the expression of tight junction proteins Occludin and ZO-1 in the Caco-2 cell monolayer. In conclusion, baicalein, luteolin, isorhamnetin and naringenin inhibit degranulation stimulated by wheat allergen and enhance intestinal barrier functions, which supports the potential pharmaceutical application of the four flavonoids treatment for wheat food allergy.

Does Nitrogen Fertilization Affect the Secondary Structures of Gliadin Proteins in Hypoallergenic Wheat?

One of the macronutrients indispensable for plant growth and development is nitrogen (N). It is responsible for starch and storage protein (gliadins and glutenins) biosynthesis and, in consequence, influences kernels’ quality and yields. However, applying N-fertilizers increases gluten content in wheat, and it may intensify the risk of developing allergy symptoms in gluten-sensitive individuals. The purpose of our research was to analyse whether and how the elimination of N-fertilizers during the cultivation of wasko.gl− wheat (modified genotype lacking ω-gliadins) changes the secondary structures of gliadin proteins. To this aim, using the FT-Raman technique, we examined flour and gliadin protein extracts obtained from kernels of two winter wheat lines: wasko.gl+ (with a full set of gliadin proteins) and wasko.gl− (without ω-gliadin fraction) cultivated on two different N-fertilization levels—0 and 120 kg N·ha⁻¹. On the basis of the obtained results, we proved that nitrogen fertilization does not have a major impact on the stability of the secondary structures of gliadin proteins for wasko.gl− wheat line with reduced allergenic properties. Furthermore, the results presented herein suggest the possibility of increasing the stability of glutenin structures as a result of the N-fertilization of wasko.gl− wheat line, which gives hope for its use in the production of wheat articles devoted to people suffering from diseases related to gluten sensitivity.

Hypoallergenic Wheat Line (1BS-18H) Lacking ω5-Gliadin Induces Oral Tolerance to Wheat Gluten Proteins in a Rat Model of Wheat Allergy

The early ingestion of food can prevent the onset of food allergy related to inducing oral tolerance (OT). We developed the Hokushin wheat line as a hypoallergenic wheat (1BS-18H) lacking ω5-gliadin, a major allergen of wheat-dependent exercise-induced anaphylaxis (WDEIA). The 1BS-18H wheat had lower ability of sensitization for ω5-gliadin compared with Hokushin wheat. Here, we evaluated the induction of OT to gluten and ω5-gliadin by the early consecutive ingestion of 1BS-18H gluten using a rat model of wheat allergy. Rats were subcutaneously immunized with commercial gluten or native ω5-gliadin following the daily oral administration of gluten. The daily oral administration of 1BS-18H gluten for 5 days before immunization suppressed the increase in gluten- or ω5-gliadin-specific IgE and IgG₁ antibodies induced by immunization to a level similar to Hokushin gluten. Intravenous challenge with gluten or ω5-gliadin did not decrease the rectal temperature in rats with OT induced by 1BS-18H or Hokushin gluten, although it was decreased in non-OT rats. In conclusion, the early consecutive ingestion of 1BS-18H wheat before sensitization induced OT to gluten and ω5-gliadin. These findings support the benefit of 1BS-18H wheat to prevent wheat allergy including WDEIA by consecutive ingestion in humans.

The Fate of IgE Epitopes and Coeliac Toxic Motifs during Simulated Gastrointestinal Digestion of Pizza Base

Understanding how food processing may modify allergen bioaccessibility and the evolution of immunologically active peptides in the gastrointestinal tract is essential if knowledge-based approaches to reducing the allergenicity of food are to be realised. A soy-enriched wheat-based pizza base was subjected to in vitro oral–gastro–duodenal digestion and resulting digests analysed using a combination of sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry (MS). The digestion profile of pizza base resembled that of bread crust where higher temperatures during baking reduced protein solubility but still resulted in the generation of a complex mixture of peptides. MS profiling showed numerous peptides carrying IgE epitopes, and coeliac toxic motifs were in excess of 20–30 residues long and were only released after either 120 min of gastric digestion or a combination of gastric and duodenal digestion. In silico prediction tools showed an overestimated number of cleavage sites identified experimentally, with low levels of atypical peptic and chymotryptic cleavage sites identified particularly at glutamine residues. These data suggest that such alternative pepsin cleavage sites may play a role in digestion of glutamine-rich cereal foods. They also contribute to efforts to provide benchmarks for mapping in vitro digestion products of novel proteins which form part of the allergenicity risk assessment.

Consumption of Tritordeum Bread Reduces Immunogenic Gluten Intake without Altering the Gut Microbiota

Gluten proteins are responsible for the wheat breadmaking quality. However, gluten is also related to human pathologies for which the only treatment is a gluten-free diet (GFD). GFD has gained popularity among individuals who want to reduce their gluten intake. Tritordeum is a cereal species that originated after crossing durum wheat with wild barley and differs from bread wheat in its gluten composition. In this work, we have characterized the immunogenic epitopes of tritordeum bread and results from a four-phase study with healthy adults for preferences of bread and alterations in the gut microbiota after consuming wheat bread, gluten-free bread, and tritordeum bread are reported. Tritordeum presented fewer peptides related to gluten proteins, CD-epitopes, and IgE binding sites than bread wheat. Participants rated tritordeum bread higher than gluten-free bread. Gut microbiota analysis revealed that the adherence to a strict GFD involves some minor changes, especially altering the species producing short-chain fatty acids. However, the short-term consumption of tritordeum bread does not induce significant changes in the diversity or community composition of the intestinal microbiota in healthy individuals. Therefore, tritordeum bread could be an alternative for healthy individuals without wheat-related pathologies who want to reduce their gluten consumption without harming their gut health.

Basophil Activation to Gluten and Non-Gluten Proteins in Wheat-Dependent Exercise-Induced Anaphylaxis

Wheat-dependent exercise-induced anaphylaxis (WDEIA) is a cofactor-induced wheat allergy. Gluten proteins, especially ω5-gliadins, are known as major allergens, but partially hydrolyzed wheat proteins (HWPs) also play a role. Our study investigated the link between the molecular composition of gluten or HWP and allergenicity. Saline extracts of gluten (G), gluten with reduced content of ω5-gliadins (G-ω5), slightly treated HWPs (sHWPs), and extensively treated HWPs (eHWPs) were prepared as allergen test solutions and their allergenicity assessed using the skin prick test and basophil activation test (BAT) on twelve patients with WDEIA and ten controls. Complementary sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE), high-performance liquid chromatography (HPLC), and mass spectrometry (MS) analyses revealed that non-gluten proteins, mainly α-amylase/trypsin inhibitors (ATIs), were predominant in the allergen test solutions of G, G-ω5, and sHWPs. Only eHWPs contained gliadins and glutenins as major fraction. All allergen test solutions induced significantly higher %CD63⁺ basophils/anti-FcεRI ratios in patients compared with controls. BAT using sHWPs yielded 100% sensitivity and 83% specificity at optimal cut-off and may be useful as another tool in WDEIA diagnosis. Our findings indicate that non-gluten proteins carrying yet unidentified allergenic epitopes appear to be relevant in WDEIA. Further research is needed to clarify the role of nutritional ATIs in WDEIA and identify specific mechanisms of immune activation.

De Novo Genome Assembly of the Japanese Wheat Cultivar Norin 61 Highlights Functional Variation in Flowering Time and Fusarium-Resistant Genes in East Asian Genotypes

Bread wheat is a major crop that has long been the focus of basic and breeding research. Assembly of its genome has been difficult because of its large size and allohexaploid nature (AABBDD genome). Following the first reported assembly of the genome of the experimental strain Chinese Spring (CS), the 10+ Wheat Genomes Project was launched to produce multiple assemblies of worldwide modern cultivars. The only Asian cultivar in the project is Norin 61, a representative Japanese cultivar adapted to grow across a broad latitudinal range, mostly characterized by a wet climate and a short growing season. Here, we characterize the key aspects of its chromosome-scale genome assembly spanning 15 Gb with a raw scaffold N50 of 22 Mb. Analysis of the repetitive elements identified chromosomal regions unique to Norin 61 that encompass a tandem array of the pathogenesis-related 13 family. We report novel copy-number variations in the B homeolog of the florigen gene FT1/VRN3, pseudogenization of its D homeolog and the association of its A homeologous alleles with the spring/winter growth habit. Furthermore, the Norin 61 genome carries typical East Asian functional variants different from CS, ranging from a single nucleotide to multi-Mb scale. Examples of such variation are the Fhb1 locus, which confers Fusarium head-blight resistance, Ppd-D1a, which confers early flowering, Glu-D1f for Asian noodle quality and Rht-D1b, which introduced semi-dwarfism during the green revolution. The adoption of Norin 61 as a reference assembly for functional and evolutionary studies will enable comprehensive characterization of the underexploited Asian bread wheat diversity.

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.

Comparison of MALDI-TOF-MS and RP-HPLC as Rapid Screening Methods for Wheat Lines With Altered Gliadin Compositions

The wheat gliadins are a complex group of flour proteins that can trigger celiac disease and serious food allergies. As a result, mutation breeding and biotechnology approaches are being used to develop new wheat lines with reduced immunogenic potential. Key to these efforts is the development of rapid, high-throughput methods that can be used as a first step in selecting lines with altered gliadin contents. In this paper, we optimized matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and reversed-phase high-performance liquid chromatography (RP-HPLC) methods for the separation of gliadins from Triticum aestivum cv. Chinese Spring (CS). We evaluated the quality of the resulting profiles using the complete set of gliadin gene sequences recently obtained from this cultivar as well as a set of aneuploid lines in CS. The gliadins were resolved into 13 peaks by MALDI-TOF-MS. α- or γ-gliadins that contain abundant celiac disease epitopes and are likely targets for efforts to reduce the immunogenicity of flour were found in several peaks. However, other peaks contained multiple α- and γ-gliadins, including one peak with as many as 12 different gliadins. In comparison, separation of proteins by RP-HPLC yielded 28 gliadin peaks, including 13 peaks containing α-gliadins and eight peaks containing γ-gliadins. While the separation of α- and γ-gliadins gliadins achieved by RP-HPLC was better than that achieved by MALDI-TOF-MS, it was not possible to link peaks with individual protein sequences. Both MALDI-TOF-MS and RP-HPLC provided adequate separation of ω-gliadins. While MALDI-TOF-MS is faster and could prove useful in studies that target specific gliadins, RP-HPLC is an effective method that can be applied more broadly to detect changes in gliadin composition.

Characterization and Relative Quantitation of Wheat, Rye, and Barley Gluten Protein Types by Liquid Chromatography-Tandem Mass Spectrometry

The consumption of wheat, rye, and barley may cause adverse reactions to wheat such as celiac disease, non-celiac gluten/wheat sensitivity, or wheat allergy. The storage proteins (gluten) are known as major triggers, but also other functional protein groups such as α-amylase/trypsin-inhibitors or enzymes are possibly harmful for people suffering of adverse reactions to wheat. Gluten is widely used as a collective term for the complex protein mixture of wheat, rye or barley and can be subdivided into the following gluten protein types (GPTs): α-gliadins, γ-gliadins, ω5-gliadins, ω1,2-gliadins, high- and low-molecular-weight glutenin subunits of wheat, ω-secalins, high-molecular-weight secalins, γ-75k-secalins and γ-40k-secalins of rye, and C-hordeins, γ-hordeins, B-hordeins, and D-hordeins of barley. GPTs isolated from the flours are useful as reference materials for clinical studies, diagnostics or in food analyses and to elucidate disease mechanisms. A combined strategy of protein separation according to solubility followed by preparative reversed-phase high-performance liquid chromatography was employed to purify the GPTs according to hydrophobicity. Due to the heterogeneity of gluten proteins and their partly polymeric nature, it is a challenge to obtain highly purified GPTs with only one protein group. Therefore, it is essential to characterize and identify the proteins and their proportions in each GPT. In this study, the complexity of gluten from wheat, rye, and barley was demonstrated by identification of the individual proteins employing an undirected proteomics strategy involving liquid chromatography-tandem mass spectrometry of tryptic and chymotryptic hydrolysates of the GPTs. Different protein groups were obtained and the relative composition of the GPTs was revealed. Multiple reaction monitoring liquid chromatography-tandem mass spectrometry was used for the relative quantitation of the most abundant gluten proteins. These analyses also allowed the identification of known wheat allergens and celiac disease-active peptides. Combined with functional assays, these findings may shed light on the mechanisms of gluten/wheat-related disorders and may be useful to characterize reference materials for analytical or diagnostic assays more precisely.

Evaluation of the allergenicity of ω5-gliadin-deficient Hokushin wheat (1BS-18) in a wheat allergy rat model

We previously developed Hokushin wheat line as a hypoallergenic wheat lacking ω5-gliadin (1BS-18), a major allergen for wheat-dependent exercise-induced anaphylaxis. However, the allergenicity of 1BS-18 has not been understood completely. In this study, we evaluated the allergenicity of 1BS-18 such as anaphylactic elicitation ability and sensitization ability using rats sensitized with ω5-gliadin or glutens prepared from Hokushin (Hokushin gluten) or 1BS-18 (1BS-18 gluten). Rats were sensitized by intraperitoneal administration of ω5-gliadin, Hokushin gluten or 1BS-18 gluten. Immunoglobulin E-mediated systemic anaphylaxis was evaluated by measuring changes in rectal temperature for 30 min after intravenous challenge with ω5-gliadin or the test glutens in unsensitized rats or rats sensitized with ω5-gliadin or the test glutens. In ω5-gliadin-sensitized rats, intravenous challenge with ω5-gliadin or Hokushin gluten significantly decreased the rectal temperature at 30 min after challenge while challenge with 1BS-18 gluten did not reduce the rectal temperature. Furthermore, intravenous challenge with ω5-gliadin significantly decreased the rectal temperature in rats sensitized with Hokushin gluten or 1BS-18 gluten. However, the reduced degree observed in 1BS-18 gluten-sensitized rats was smaller than that in Hokushin gluten-sensitized rats. In conclusion, 1BS-18 elicited no allergic reaction in ω5-gliadin-sensitized rats and had less sensitization ability for ω5-gliadin than that of Hokushin wheat.

Intestinal absorption of the wheat allergen gliadin in rats

BACKGROUND

Aspirin enhances food allergy symptoms by increasing absorption of ingested allergens. The objective of this study is to elucidate the role of aspirin in facilitating intestinal absorption of the wheat allergen, gliadin, in rats.

METHODS

Plasma concentrations of gliadin were determined after oral administration by gavage or administration into a closed intestinal loop in rats. We used an in situ intestinal re-circulating perfusion experiment to examine the effect of pepsin on aspirin-facilitated gliadin absorption. Fluorescein isothiocyanate (FITC)-labeled dextran-40 (FD-40) was used as a marker of non-specific absorption. The molecular size of gliadin and its allergenicity in plasma were examined using immunoblot analysis and intradermal reaction tests with Evans blue dye (EBD) extravasation, respectively.

RESULTS

Aspirin increased plasma concentrations of gliadin after oral administration but had no effect in the closed intestinal loop study. An in situ intestinal re-circulating perfusion study showed that FITC-labeled gliadin was absorbed similarly to FD-40. Aspirin increased absorption of both intact and pepsin-digested gliadin, with a more significant effect on absorption of pepsin-treated gliadin. Immunoblotting showed that most gliadin was absorbed in intact form. When the gliadin fraction was extracted from rat plasma after gavage and injected intradermally into gliadin-sensitized rats, EBD extravasation was observed at injection sites in a gliadin dose-dependent manner.

CONCLUSIONS

Aspirin increased the absorption of intact and pepsin-digested gliadin via the paracellular pathway, maintaining their allergenicity. Moreover, the effect of aspirin on gliadin absorption was enhanced by modification and digestion of gliadin in the stomach.

Genome mapping of seed-borne allergens and immunoresponsive proteins in wheat

Wheat is an important staple grain for humankind globally because of its end-use quality and nutritional properties and its adaptability to diverse climates. For a small proportion of the population, specific wheat proteins can trigger adverse immune responses and clinical manifestations such as celiac disease, wheat allergy, baker's asthma, and wheat-dependent exercise-induced anaphylaxis (WDEIA). Establishing the content and distribution of the immunostimulatory regions in wheat has been hampered by the complexity of the wheat genome and the lack of complete genome sequence information. We provide novel insights into the wheat grain proteins based on a comprehensive analysis and annotation of the wheat prolamin Pfam clan grain proteins and other non-prolamin allergens implicated in these disorders using the new International Wheat Genome Sequencing Consortium bread wheat reference genome sequence, RefSeq v1.0. Celiac disease and WDEIA genes are primarily expressed in the starchy endosperm and show wide variation in protein- and transcript-level expression in response to temperature stress. Nonspecific lipid transfer proteins and α-amylase trypsin inhibitor gene families, implicated in baker's asthma, are primarily expressed in the aleurone layer and transfer cells of grains and are more sensitive to cold temperature. The study establishes a new reference map for immunostimulatory wheat proteins and provides a fresh basis for selecting wheat lines and developing diagnostics for products with more favorable consumer attributes.

Anaphylaxis in the 21st century: phenotypes, endotypes, and biomarkers

Anaphylaxis is the most serious of all allergic reactions and can be fatal. The diagnosis is frequently delayed, and misdiagnosis often occurs with asthma or urticaria. Biomarkers such as tryptase are not routinely checked, and appropriate treatment with epinephrine is not administered in a majority of cases, increasing the risk of poor outcomes. The objective of this review is to provide a better understanding of the pathophysiology of anaphylaxis with a description of phenotypes, endotypes, and biomarkers available in both the clinical and research settings. Expanding knowledge with regard to the presentation, causes, and triggers for anaphylaxis among health care providers will improve its diagnosis and management, increase patient safety, and decrease morbidity and mortality.

Proteomic Profiling and Epitope Analysis of the Complex α-, γ-, and ω-Gliadin Families in a Commercial Bread Wheat

Wheat gliadins are a complex group of proteins that contribute to the functional properties of wheat flour doughs and contain epitopes that are relevant for celiac disease (CD) and wheat-dependent exercise-induced anaphylaxis (WDEIA). In this study, we extracted ethanol-soluble gliadin fractions from flour of the Korean bread wheat cultivar Keumkang. Proteins were separated by 2-dimensional gel electrophoresis (2-DE) using a pI range of 6-11 in the first dimension and subjected to tandem mass spectrometry. α-, γ-, and ω-gliadins were identified as the predominant proteins in 31, 28, and one 2-DE spot, respectively. An additional six ω-gliadins were identified in a separate experiment in which a pI range of 3-11 was used for protein separation. We analyzed the composition of CD- and WDEIA-relevant epitopes in the gliadin sequences from Keumkang flour, demonstrating the immunogenic potential of this cultivar. Detailed knowledge about the complement of gliadins accumulated in Keumkang flour provides the background necessary to devise either breeding or biotechnology strategies to improve the functional properties and reduce the adverse health effects of the flour.

Molecular cloning and functional characterization of two novel high molecular weight glutenin subunit genes in Aegilops markgrafii

The high molecular weight glutenin subunits (HMW-GS) in bread wheat are major determinants of the viscoelastic properties of dough and the end-use quality of wheat flour. Two novel HMW-GSs, 1Cx1.1 and 1Cy9.1, from the diploid species Aegilops markgrafii (CC) were identified in the present study. The corresponding open-reading frames of the genes of 1Cx1.1 and 1Cy9.1 were isolated and sequenced using allele-specific polymerase chain reaction. Sequence comparison demonstrated that the HMW-GSs from Ae. markgrafii possess a similar primary structure to the homologous proteins in wheat and related species. A tandem tripeptide exists in the central repetitive domain of 1Cx1.1, and this unique structure is very rare in the HMW-GSs of other genomes. To confirm the authenticity of these isolated endogenous HMW-GS, the heterologous proteins produced by removing the signal peptides expressed by E. coli exhibited the same electrophoretic mobility as the native proteins. Subsequently, the single protein was purified at a sufficient scale for incorporation into flour to performsodium dodecyl sulphate (SDS) sedimentation testing. Notably, the SDS sedimentation volume was less with the addition of 1Cx1.1 than it was with 1Cy9.1.

Enzyme-Free Immunoassay Using Silver Nanoparticles for Detection of Gliadin at Ultralow Concentrations

Determination of biomarkers in clinical or food samples is of crucial importance for monitoring, prevention, and care of public health. The standard procedure used for this purpose is the enzyme-linked immunosorbent assay (ELISA), which makes use of the specific antibody-antigen biorecognition and the catalytic effect of the enzymes. One of the main shortcomings of this technique is the use of enzymes that often present low chemical and thermal stabilities compared to other chemicals. Other drawbacks include the nonspecific binding process that could lead to false-positive results, the use of relatively large amounts of the sample, and the number of time-consuming steps involved. Recently, an enzyme-free and ultrasensitive analytical method for antigen detection denoted as intensity depletion immunolinked assay (IDILA) has been proposed by our laboratory. The assay is based on the inhibition to form Ag nanosphere dimers linked by a specific antibody in the presence of the corresponding antigen. In this work, we go a step further demonstrating how the performance of this method could be improved by using silver nanoparticles (Ag NPs) of different diameters (58 and 78 nm). The experiments are performed for detecting gliadin, an antigen of utmost importance in celiac disease, and the results are compared with ELISA, the standard technique homologated by the Food Codex Alimentarius. It is found that the IDILA assay could be around 1000 or 10 000 times more sensitive than ELISA, also having lower limits of detection, depending on the conditions explored (fraction of dimers and Ag NP diameter). Using the appropriate conditions, the IDILA assay is shown to be able to detect femtomolar concentrations of the antigen, besides being robust, reliable, cheap, rapid (around 2 h), and of easy implementation using the standard equipment and biomolecular reagents used for the ELISA assay.

Gliadins from wheat grain: an overview, from primary structure to nanostructures of aggregates

Gliadins are well-known wheat grain proteins, particularly important in food science. They were studied as early as the 1700s. Despite their long history, it has been difficult to identify their higher-order structure as they aggregate in aqueous solution. Consequently, most studies have been performed by extracting the proteins in 70% ethanol or dilute acidic solutions. The carboxy-terminal half of α- and γ-gliadins have α-helix-rich secondary structures stabilized with intramolecular disulfide bonds, which are present in either aqueous ethanol or pure water. The amino-terminal-repeat region of α- and γ-gliadins has poly-L-proline II and β-reverse-turn structures. ω-Gliadins also have poly-L-proline II and β-reverse-turn structures, but no α-helix structure. The size and shape of gliadin molecules have been determined by assessing a variety of parameters: their sedimentation velocity in the analytical ultracentrifuge, intrinsic viscosity, small-angle X-ray scattering profile, and images of the proteins from scanning probe microscopes such as a tunneling electron microscope and atomic force microscope. Models for gliadins are either rods or prolate ellipsoids whether in aqueous ethanol, dilute acid, or pure water. Recently, gliadins have been shown to be soluble in pure water, and a novel extraction method into pure water has been established. This has made it possible to analyze gliadins in pure water at neutral pH, and permitted the characterization of hydrated gliadins. They formed hierarchical nanoscale structures with internal density fluctuations at high protein concentrations.

Diagnosis and management of anaphylaxis in precision medicine

Anaphylaxis is the most severe and frightening of the allergic reactions, placing patients at high risk and demanding prompt recognition and immediate management by health care providers. Yet because its symptoms imitate those of other diseases, such as asthma and urticaria, current data suggest that its diagnosis is often missed, with underuse of tryptase measurement; its treatment is delayed, with little use of epinephrine; and its underlying cause or causes are poorly investigated. Deaths from anaphylaxis are difficult to investigate because of miscoding. Surprisingly, patients treated with new and powerful chemotherapy agents and humanized mAbs present with nonclassical symptoms of anaphylaxis, and patients may present with unrecognized clonal mast cell disorders with KIT mutations may present as Hymenoptera-induced or idiopathic anaphylaxis. The goal of this review is to recognize the presentations of anaphylaxis with the description of its current phenotypes, to provide new insight and understanding of its mechanisms and causes through its endotypes, and to address its biomarkers for broad clinical use. Ultimately, the aim is to empower allergists and heath care providers with new tools that can help alleviate patients' symptoms, preventing and protecting them against anaphylaxis.

Molecular features of grass allergens and development of biotechnological approaches for allergy prevention

Allergic diseases are characterized by elevated allergen-specific IgE and excessive inflammatory cell responses. Among the reported plant allergens, grass pollen and grain allergens, derived from agriculturally important members of the Poaceae family such as rice, wheat and barley, are the most dominant and difficult to prevent. Although many allergen homologs have been predicted from species such as wheat and timothy grass, fundamental aspects such as the evolution and function of plant pollen allergens remain largely unclear. With the development of genetic engineering and genomics, more primary sequences, functions and structures of plant allergens have been uncovered, and molecular component-based allergen-specific immunotherapies are being developed. In this review, we aim to provide an update on (i) the distribution and importance of pollen and grain allergens of the Poaceae family, (ii) the origin and evolution, and functional aspects of plant pollen allergens, (iii) developments of allergen-specific immunotherapy for pollen allergy using biotechnology and (iv) development of less allergenic plants using gene engineering techniques. We also discuss future trends in revealing fundamental aspects of grass pollen allergens and possible biotechnological approaches to reduce the amount of pollen allergens in grasses.

Isolation and characterization of gluten protein types from wheat, rye, barley and oats for use as reference materials

Gluten proteins from wheat, rye, barley and, in rare cases, oats, are responsible for triggering hypersensitivity reactions such as celiac disease, non-celiac gluten sensitivity and wheat allergy. Well-defined reference materials (RM) are essential for clinical studies, diagnostics, elucidation of disease mechanisms and food analyses to ensure the safety of gluten-free foods. Various RM are currently used, but a thorough characterization of the gluten source, content and composition is often missing. However, this characterization is essential due to the complexity and heterogeneity of gluten to avoid ambiguous results caused by differences in the RM used. A comprehensive strategy to isolate gluten protein fractions and gluten protein types (GPT) from wheat, rye, barley and oat flours was developed to obtain well-defined RM for clinical assays and gluten-free compliance testing. All isolated GPT (ω5-gliadins, ω1,2-gliadins, α-gliadins, γ-gliadins and high- and low-molecular-weight glutenin subunits from wheat, ω-secalins, γ-75k-secalins, γ-40k-secalins and high-molecular-weight secalins from rye, C-hordeins, γ-hordeins, B-hordeins and D-hordeins from barley and avenins from oats) were fully characterized using analytical reversed-phase high-performance liquid chromatography (RP-HPLC), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), N-terminal sequencing, electrospray-ionization quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS) and untargeted LC-MS/MS of chymotryptic hydrolyzates of the single GPT. Taken together, the analytical methods confirmed that all GPT were reproducibly isolated in high purity from the flours and were suitable to be used as RM, e.g., for calibration of LC-MS/MS methods or enzyme-linked immunosorbent assays (ELISAs).

Wheat-dependent exercise-induced anaphylaxis

Wheat-dependent exercise-induced anaphylaxis (WDEIA) is a rare, but potentially severe food allergy exclusively occurring when wheat ingestion is accompanied by augmenting cofactors. It is clinically characterized by anaphylactic reactions ranging from urticaria and angioedema to dyspnoea, hypotension, collapse, and shock. WDEIA usually develops after ingestion of wheat products followed by physical exercise. Other cofactors are acetylsalicylic acid and other non-steroidal anti-inflammatory drugs, alcohol, and infections. The precise mechanisms of WDEIA remain unclear; exercise and other cofactors might increase gastrointestinal allergen permeability and osmolality, redistribute blood flow, or lower the threshold for IgE-mediated mast cell degranulation. Among wheat proteins, ω5-gliadin and high-molecular-weight glutenin subunits have been reported to be the major allergens. In some patients, WDEIA has been discussed to be caused by epicutaneous sensitization with hydrolysed wheat gluten included in cosmetics. Diagnosis is made based on the patient's history in combination with allergy skin testing, determination of wheat-specific IgE serum antibodies, basophil activation test, histamine release test, and/or exercise challenge test. Acute treatment includes application of adrenaline or antihistamines. The most reliable prophylaxis of WDEIA is a gluten-free diet. In less severe cases, a strict limitation of wheat ingestion before exercise and avoidance of other cofactors may be sufficient.

Molecular characterization of the IgE-binding epitopes in the fast ω-gliadins of Triticeae in relation to wheat-dependent, exercise-induced anaphylaxis

Fast ω-gliadins were minor components of wheat storage proteins but a major antigen triggering allergy to wheat. Sixty-six novel full-length fast ω-gliadin genes with unique characteristics were cloned and sequenced from wheat and its relative species using a PCR-based strategy. Their coding regions ranged from 177bp to 987bp in length and encoded 4.28kDa to 37.56kDa proteins. On the base of first three deduced amino acids at the N-terminal, these genes could be classified into the six subclasses of SRL-, TRQ-, GRL-, NRL-, SRP- and SRM-type ω-gliadin genes. Compared by multiple alignments, these genes were significantly different from each other, due to the insertion or deletion at the repetitive domain. An analysis of the IgE-binding epitopes of the 66 deduced fast ω-gliadins demonstrated that they contained 0-24 IgE-binding epitopes. The phylogenetic tree demonstrated that the fast ω-gliadins and slow ω-gliadins were separated into two groups and their divergence time was 21.64millionyears ago. Sequence data of the fast ω-gliadin genes assist in the study of the origins and evolutions of the different types of ω-gliadins while also providing a basis for the synthesis of monoclonal antibodies to detect wheat antigen content.

Preparation of gluten free bread enriched with green mussel (Perna canaliculus) protein hydrolysates and characterization of peptides responsible for mussel flavour

Green mussel protein hydrolysates (GMPH) utilization for the enrichment of gluten-free bread followed by characterization of flavour peptides using chromatography and electronic nose techniques have been done. The degree of hydrolysis was carried out in each protease digest, and the higher degree of hydrolysis was observed in pepsin digestion. Gluten-free (GF) bread was formulated by using buckwheat flour (BWF), rice flour (RF) and chickpea flour (CPF) (70:20:10) and GMPH were added in the range of 0-20% in the GF bread for enrichment with GMPH. Radar plot of the electronic nose analysis showed that the sensors P30/2, T30/1 and T70/2 had a higher response to the GF bread and GMPH. Consequently, the peptide sequence was obtained manually by ESI-MS spectra of GMPH (KGYSSYICDK) and F-II (SSYCIVKICDK). Flavour quality was 97% discriminately comparable to the GMPH and F-II fractions. Mussel flavoured GF bread can be included in the celiac diet.

Assessment of the Allergenic Potential of Transgenic Wheat (Triticum aestivum) with Reduced Levels of ω5-Gliadins, the Major Sensitizing Allergen in Wheat-Dependent Exercise-Induced Anaphylaxis

The ω5-gliadins are the major sensitizing allergens in wheat-dependent exercise-induced anaphylaxis (WDEIA). In this study, two-dimensional immunoblot analysis was used to assess the allergenic potential of two transgenic wheat lines in which ω5-gliadin genes were silenced by RNA interference. Sera from 7 of 11 WDEIA patients showed greatly reduced levels of immunoglobulin E (IgE) reactivity to ω5-gliadins in both transgenic lines. However, these sera also showed low levels of reactivity to other gluten proteins. Sera from three patients showed the greatest reactivity to proteins other than ω5-gliadins, either high-molecular-weight glutenin subunits (HMW-GSs), α-gliadins, or non-gluten proteins. The complexity of immunological responses among these patients suggests that flour from the transgenic lines would not be suitable for individuals already diagnosed with WDEIA. However, the introduction of wheat lacking ω5-gliadins could reduce the number of people sensitized to these proteins and thereby decrease the overall incidence of this serious food allergy.

Common food allergens and their IgE-binding epitopes

Food allergy is an adverse immune response to certain kinds of food. Although any food can cause allergic reactions, chicken egg, cow's milk, wheat, shellfish, fruit, and buckwheat account for 75% of food allergies in Japan. Allergen-specific immunoglobulin E (IgE) antibodies play a pivotal role in the development of food allergy. Recent advances in molecular biological techniques have enabled the efficient analysis of food allergens. As a result, many food allergens have been identified, and their molecular structure and IgE-binding epitopes have also been identified. Studies of allergens have demonstrated that IgE antibodies specific to allergen components and/or the peptide epitopes are good indicators for the identification of patients with food allergy, prediction of clinical severity and development of tolerance. In this review, we summarize our current knowledge regarding the allergens and IgE epitopes in the well-researched allergies to chicken egg, cow's milk, wheat, shrimp, and peanut.

Structural Basis of IgE Binding to α- and γ-Gliadins: Contribution of Disulfide Bonds and Repetitive and Nonrepetitive Domains

Wheat products cause IgE-mediated allergies. The present study aimed to decipher the molecular basis of α- and γ-gliadin allergenicity. Gliadins and their domains, the repetitive N-terminal and the nonrepetitive C-terminal domains, were cloned and expressed in Escherichia coli. Their secondary structures and their IgE binding capacity were compared with those of natural proteins before and after reduction/alkylation. Allergenicity was evaluated with sera from patients who had a wheat food allergy or baker's asthma. The secondary structures of natural and recombinant proteins were slightly different. Compared with natural gliadins, recombinant proteins retained IgE binding but with reduced reactivity. Reduction/alkylation decreased IgE binding for both natural and recombinant gliadins. Although more continuous epitopes were identified in the N-terminal domains of α- and γ-gliadins, both the N-terminal and C-terminal domains contributed to IgE binding. As for other members of the prolamin superfamily, disulfide bonds appear to be of high importance for IgE binding.

Biochemical, biophysical and IgE-epitope characterization of the wheat food allergen, Tri a 37

Wheat is an important staple food and potent allergen source. Recently, we isolated a cDNA coding for wheat alpha-purothionin which is recognized by wheat food allergic patients at risk for severe wheat-induced allergy. The purpose of the present study was the biochemical, biophysical and IgE epitope characterization of recombinant alpha-purothionin. Synthetic genes coding for alpha-purothionin were expressed in a prokaryotic system using Escherichia coli and in a eukaryotic expression system based on baculovirus-infected Sf9-insect cells. Recombinant proteins were purified and characterized by SDS-PAGE, mass spectrometry, circular dichroism, chemical cross-linking and size exclusion chromatography. Five overlapping peptid were synthesized for epitope mapping. Alpha-purothionin-specific rabbit antibodies were raised to perform IgE-inhibition experiments and to study the resistance to digestion. The IgE reactivity of the proteins and peptides from ten wheat food allergic patients was studied in non-denaturing RAST-based binding assays. Alpha-purothionin was expressed in the prokaryotic (EcTri a 37) and in the eukaryotic system (BvTri a 37) as a soluble and monomeric protein. However, circular dichroism analysis revealed that EcTri a 37 was unfolded whereas BvTri a 37 was a folded protein. Both proteins showed comparable IgE-reactivity and the epitope mapping revealed the presence of sequential IgE epitopes in the N-terminal basic thionin domain (peptide1:KSCCRSTLGRNCYNLCRARGAQKLCAGVCR) and in the C-terminal acidic extension domain (peptide3:KGFPKLALESNSDEPDTIEYCNLGCRSSVC, peptide4:CNLGCRSSVCDYMVNAAADDEEMKLYVEN). Natural Tri a 37 was digested under gastric conditions but resistant to duodenal digestion. Immunization with EcTri a 37 induced IgG antibodies which recognized similar epitopes as IgE antibodies from allergic patients and inhibited allergic patients' IgE binding. Reactivity to Tri a 37 does not require a folded protein and the presence of sequential IgE epitopes indicates that sensitization to alpha-purothionin occurs via the gut. Both allergens can be used for in-vitro diagnosis of wheat food allergy. The induction of blocking IgG antibodies suggests the usefulness for immunotherapy.

The high molecular weight glutenin subunit Bx7 allergen from wheat contains repetitive IgE epitopes

BACKGROUND

Wheat is one of the most common food allergen sources for children and adults. The aim of this study was to characterize new wheat allergens using an IgE discovery approach and to investigate their IgE epitopes.

METHODS

A cDNA expression library representing the wheat transcriptome was constructed in phage lambda gt11 and screened with IgE antibodies from wheat food allergic patients. IgE-reactive cDNA clones coding for portions of high molecular weight (HMW) glutenin subunits were identified by sequence analysis of positive clones. IgE epitopes were characterized using recombinant fragments from the HMW Bx7 and synthetic peptides thereof for testing of allergic patients' sera and in basophil degranulation assays.

RESULTS

We found that the major IgE-reactive areas of HMW glutenins are located in the repetitive regions of the protein and could show that two independent IgE-reactive fragments from HMW Bx7 contained repetitive IgE epitopes.

CONCLUSIONS

Our results demonstrate that IgE antibodies from wheat food allergic patients can recognize repetitive epitopes in one of the important wheat food allergens. Recombinant HMW Bx7 may be included into the panel of allergens for component-resolved diagnosis of wheat food allergy.

Characterization of causative allergens for wheat-dependent exercise-induced anaphylaxis sensitized with hydrolyzed wheat proteins in facial soap

BACKGROUND

In Japan, hydrolyzed wheat proteins (HWP) have been reported to cause wheat-dependent exercise-induced anaphylaxis (WDEIA) by transcutaneous sensitization using HWP-containing soap. Patients develop allergic reactions not only with soap use, but also with exercise after the intake of wheat protein (WP). ω5-Gliadin and HMW-glutenin were identified as major allergens in conventional WP-WDEIA patients. However, the allergens in HWP-WDEIA have yet to be elucidated.

METHODS

Sera were obtained from 22 patients with HWP-sensitized WDEIA. The allergenic activities of HWP and six recombinant wheat gluten proteins, including α/β-, γ-, ω1,2- and ω5-gliadin and low- and high molecular weight (HMW)-glutenins, were characterized by immunoblot analysis and histamine releasing test. IgE-binding epitopes were identified using arrays of overlapping peptides synthesized on SPOTs membrane.

RESULTS

Immunoblot analysis showed that IgE antibodies (Abs) from HWP-WDEIA bound to α/β-, γ- and ω1,2-gliadin. Recombinant γ-gliadin induced significant histamine release from basophils in eight of 11 patients with HWP-WDEIA. An IgE-binding epitope "QPQQPFPQ" was identified within the primary sequence of γ-gliadin, and the deamidated peptide containing the "PEEPFP" sequence bound with IgE Abs more strongly compared to the native epitope-peptide. The epitope-peptide inhibited IgE-binding to HWP, indicating that the specific IgE to HWP cross-reacts with γ-gliadin.

CONCLUSIONS

HWP-WDEIA patients could be sensitized to HWP containing a PEEPFP sequence, and WDEIA symptoms after WP ingestion could partly be induced by γ-gliadin. These findings could be useful to help develop tools for diagnosis and desensitization therapy for HWP-WDEIA.

The sensitivity and clinical course of patients with wheat-dependent exercise-induced anaphylaxis sensitized to hydrolyzed wheat protein in facial soap - secondary publication

BACKGROUND

Recently, an increasing number of patients with wheat-dependent exercise-induced anaphylaxis (WDEIA) have been reported in Japan. Most of them had developed this condition during or after using hydrolyzed wheat protein (HWP)-containing soap (HWP-WDEIA).

METHODS

To clarify the relation between WDEIA and HWP-containing soap and their prognosis, we retrospectively studied the patients who visited Hiroshima University Hospital and were diagnosed as WDEIA from January 2010 to June 2011. We took detailed clinical histories, performed skin prick tests, serum immunoassays for antigen-specific IgE and basophil histamine release test, and followed up their clinical courses after the diagnosis.

RESULTS

Among 36 patients with WDEIA, 30 patients had used only one type of HWP-soap. The patients with HWP-WDEIA were mainly women and had developed facial symptoms and angioedema. They suffered from blood pressure reductions less frequently than patients with conventional WDEIA. The levels of gluten-specific IgE were higher than those of omega-5 gliadin in patients with HWP-WDEIA (P < 0.05, One-way ANOVA). All patients with HWP-WDEIA were positive against HWP in histamine release test. Among the conventional wheat antigens, glutenins induced the highest histamine release from basophils of patients with HWP-WDEIA. The sensitivities of patients against glutens and glutenins were reduced over months along with the discontinuance of HWP-soap.

CONCLUSIONS

The development of HWP-WDEIA is associated with the use of HWP-soap. The sensitivity to HWP that cross reacts with non-processed wheat may be reduced or possibly cured after the discontinuation of HWP-soap.

Serum gliadin monitoring extracts patients with false negative results in challenge tests for the diagnosis of wheat-dependent exercise-induced anaphylaxis

BACKGROUND

Challenge testing with wheat plus exercise and/or aspirin is a gold standard for the diagnosis of wheat-dependent exercise-induced anaphylaxis (WDEIA); however, the test may often yield false-negative results. Our previous study suggested that an increase in serum wheat gliadin levels is required to induce allergic symptoms in patients with WDEIA. Based on this knowledge, we sought to extract the patients with false negative results in the challenge tests of WDEIA.

METHODS

Thirty-six patients with suspected WDEIA were enrolled. First, group categorizations-Group I, challenge tests were positive; Group II, challenge tests were negative and serum gliadin were undetectable; Group III, challenge tests were negative and serum gliadin were detectable-were given according to the results of wheat plus exercise and/or aspirin challenge testing and serum gliadin levels. Second, diagnoses were made using retests and/or dietary management in Group II and III.

RESULTS

Positive results for wheat plus exercise and/or aspirin challenge tests gave a diagnosis of definite WDEIA in 17 of 36 patients (Group I). Of the remaining 19 challenge negative patients, serum gliadin was undetectable in ten patients (Group II). Of the ten patients (Group II), three of them were diagnosed as definite WDEIA by retesting and six of them were diagnosed as probable WDEIA using a wheat elimination diet, whereas one patient was non-WDEIA. In the rest of the nine challenge negative patients, serum gliadin was detectable (Group III). No allergic episodes with a normal diet provided a diagnosis of non-WDEIA in seven of the nine patients, whereas the remaining two patients were probable WDEIA or had another food allergy because of repeated episodes.

CONCLUSIONS

Our study revealed that serum gliadin monitoring during challenge testing is useful.

A recombinant ω-gliadin-like D-type glutenin and an α-gliadin from wheat (Triticum aestivum): two immunoglobulin E binding proteins, useful for the diagnosis of wheat-dependent allergies

Among the wheat prolamins, D-type glutenins display a highly repetitive sequence similar to ω-gliadins, but they contain a cysteine, that allows them to be included in the gluten macropolymers. An ω-gliadin-like D-type glutenin, an α-gliadin, and an ω5-gliadin-like D-type glutenin were obtained as recombinant proteins and compared using synchrotron radiation circular dichroism. This technique evidenced the strong thermostability of the ω5-gliadin-like protein. The IgE reactivity of recombinant proteins was evaluated using 45 sera from wheat-allergic patients. The sera from patients diagnosed with cutaneous hypersensitivity to hydrolyzed wheat proteins often reacted with the ω-gliadin-like D-type glutenin and α-gliadin, whereas the IgE reaction was less frequent after dietary sensitization. So, these two proteins could be useful to diagnose these diseases. The sera from patients with exercise-induced anaphylaxis recognized the ω5-gliadin-like protein as a positive control and, less frequently, the other proteins tested. Only some sera from patients with baker's asthma reacted with the proteins tested.

Comparative and evolutionary analysis of new variants of ω-gliadin genes from three A-genome diploid wheats

A genomic polymerase chain reaction (PCR) cloning strategy was applied to isolate ω-gliadin sequences from three A-genome diploid wheats (Triticum monococcum, T. boeoticum and T. urartu). Amplicon lengths varied from 744 and 1,044 bp, and those of the corresponding deduced mature proteins from 248 to 348 residues. The primary structure of the deduced polypeptides comprised a short N- and C-terminal conserved domain, and a long, variable repetitive domain. A phylogenetic analysis recognised several clades: the first consisted of three T. aestivum sequences; the second and the third two T. boeoticum and six T. monococcum sequences; and the rest four T. urartu and three T. aestivum sequences. Among the functional (non-pseudogene) ARQ/E-type ω-gliadin sequences, two were derived from T. boeoticum and three from T. monococcum; one of the latter sequences appeared to be a chimera originating via illegitimate recombination between the other two T. monococcum sequences. None of the 12 intact ω-gliadin sequences contained any cysteine or methionine residues. We discussed the variation and evolution of A-genome ω-gliadin genes.

Usefulness of specific IgE antibodies to ω-5 gliadin in the diagnosis and follow-up of Japanese children with wheat allergy

BACKGROUND

Gliadins have been implicated in IgE-mediated allergy to ingested wheat. ω-5 gliadin seems to be a clinically relevant allergen component in children with immediate wheat allergy (WA), but contradictory results have been published.

OBJECTIVES

To investigate whether specific IgE (sIgE) antibodies to recombinant ω-5 gliadin could be used as a marker for oral wheat challenge outcome in wheat-sensitized children and to study whether measurements of sIgE to ω-5 gliadin are useful in monitoring children with WA to assess whether the allergy is outgrown or persistent.

METHODS

Eighty-eight serum samples from children sensitized to wheat were collected consecutively. sIgE to ω-5 gliadin was related to a physician's diagnosis of WA.

RESULTS

Sixty-seven of 88 children sensitized to wheat were diagnosed as having WA. The geometric mean concentrations of sIgE to ω-5 gliadin were 2.04 kU(A)/L (range, <0.35-100 kU(A)/L) in children with WA and 0.40 kU(A)/L (range, <0.35-1.8 kU(A)/L) in children without WA. At follow-up, after being on a wheat-free diet for approximately 2 years, the sIgE titers to ω-5 gliadin were below 0.35 kU(A)/L (mean, 0.34 kU(A)/L; range, 0.34-2.3 kU(A)/L) in 10 of 15 children with outgrown WA. Conversely, in 12 of 14 children with persistent WA, the sIgE titers to ω-5 gliadin were still elevated (mean, 5.89 kU(A)/L; range, 0.34-16.3 kU(A)/L).

CONCLUSIONS

sIgE to ω-5 gliadin can be used as an accurate alternative to potentially dangerous wheat food challenges in monitoring WA.

Proteomic analysis in allergy and intolerance to wheat products

Owing to its extensive use in the human diet, wheat is among the most common causes of food-related allergies and intolerances. Allergies to wheat are provoked by ingestion, inhalation or contact with either the soluble or the insoluble gluten proteins in wheat. Gluten proteins, and particularly the gliadin fraction, are also the main factor triggering celiac disease, a common enteropathy induced by ingestion of wheat gluten proteins and related prolamins from oat, rye and barley in genetically susceptible individuals. The role of gliadin and of its derived peptides in eliciting the adverse reactions in celiac disease are still far from being completely explained. Owing to its unique pathogenesis, celiac disease is widely investigated as a model immunogenetic disorder. The structural characterization of the injuring agents, the gluten proteins, assumes a particular significance in order to deepen the understanding of the events that trigger this and similar diseases at the molecular level. Recent developments in proteomics have provided an important contribution to the understanding of several basic aspects of wheat protein-related diseases. These include: the identification of gluten fractions and derived peptides involved in wheat allergy and intolerance, including celiac disease, and the elucidation of their mechanism of toxicity; the development and validation of sensitive and specific methods for detecting trace amounts of gluten proteins in gluten-free foods for intolerant patients; and the formulation of completely new substitute foods and ingredients to replace the gluten-based ones. In this article, the main aspects of current and prospective applications of mass spectrometry and proteomic technologies to the structural characterization of gluten proteins and derived peptides are critically presented, with a focus on issues related to their detection, identification and quantification, which are relevant to the biochemical, immunological and toxicological aspects of wheat intolerance.