Specific IgE determination to epitope peptides of omega-5 gliadin and high molecular weight glutenin subunit is a useful tool for diagnosis of wheat-dependent exercise-induced anaphylaxis

Evaluation of reduced allergenicity of deamidated gliadin in a mouse model of wheat-gliadin allergy using an antibody prepared by a peptide containing three epitopes

Gliadin is the principal allergen of wheat-dependent exercise-induced anaphylaxis (WDEIA). The primary structure of IgE-binding epitopes in wheat gliadin includes tandem sequencing sites of glutamine residues. Therefore, deamidation would be an effective approach to reduce the allergenicity of wheat proteins. In our previous study, we deamidated wheat gliadin without causing peptide-bond hydrolysis or polymerization by use of carboxylated cation-exchange resins, and we found that the deamidated gliadin scarcely reacted with the sera of patients radioallergosorbent test (RAST)-positive to wheat. In this study, we examined the allergenicity of deamidated gliadin in a mouse model of wheat-gliadin allergy. Oral administration of deamidated gliadin to gliadin-sensitized mice suppressed enhancement in intestinal permeability, serum allergen level, serum allergen-specific IgE level, mast-cell-surface expression of FcεRI, and serum and intestinal histamine levels. Our results indicate that gliadin deamidated with no peptide-bond hydrolysis by cation-exchange resins has low allergenicity even under in vivo conditions.

US perspective on gluten-related diseases

The incidence of allergy and autoimmune disease in the US and other industrialized nations is increasing, and gluten-related disorders are no exception. The US has documented a profound rise in celiac disease that cannot be fully explained by improved serological techniques or better recognition by physicians. Non-celiac gluten sensitivity, a condition only recently recognized by the medical community, has become a commonly diagnosed entity. Proteins, including gluten are increasingly being identified as a source of wheat allergy. Although the gluten free diet represents a safe and effective treatment for these conditions, there is still much to be learned about the development of gluten-related disorders and the apparent increase in incidence within the US. In this article, we present a review of current knowledge on the epidemiology of gluten-related disorders within a global context, with a focus on diagnostic trends and the evaluation of potential risk factors.

Wheat - Dependent Exercise-Induced Anaphylaxis Occurred With a Delayed Onset of 10 to 24 hours After Wheat Ingestion: A Case Report

Wheat-dependent exercise-induced anaphylaxis (WDEIA) usually occurs 1 to 4 hours after wheat ingestion and the pathophysiology of WDEIA remains unknown. It is recommended that WDEIA patients refrain from exercise for 4 to 6 hours after wheat ingestion. We report a case of a 51-year-old man who experienced 5 anaphylaxis attacks; two of which occurred 10 to 24 hours after wheat ingestion and exercise. He has a history of chronic gastroenteritis that responds well to antihistamine drugs but not proton pump inhibitors (PPIs) and prokinetic agents. Abdominal CT results implied the possibility of superior mesenteric artery syndrome. We suggest that WDEIA occurs 6 hours after wheat ingestion in cases compounded by obstructive gastrointestinal diseases.

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.

Advances in in vitro diagnostics in allergy, asthma, and immunology in 2012

Laboratory tests play an increasing role in risk assessment, diagnostics, and disease monitoring. Great advances have been achieved lately, particularly in the field of clinical immunology and allergy. These include neonatal screening of immunodeficiencies and asthma biomarkers and investigation into the role of recombinant allergens in in vitro testing. The latter area has implications for the diagnostics of food allergy, pollen-induced allergies, asthma, and insect allergies.

MS(E) based multiplex protein analysis quantified important allergenic proteins and detected relevant peptides carrying known epitopes in wheat grain extracts

The amount of clinically relevant, allergy-related proteins in wheat grain is still largely unknown. The application of proteomics may create a platform not only for identification and characterization, but also for quantitation of these proteins. The aim of this study was to evaluate the data-independent quantitative mass spectrometry (MS(E)) approach in combination with 76 wheat allergenic sequences downloaded from the AllergenOnline database ( www.allergenonline.org ) as a starting point. Alcohol soluble extracts of gliadin and glutenin proteins were analyzed. This approach has resulted in identification and quantification of 15 allergenic protein isoforms that belong to amylase/trypsin inhibitors, γ-gliadins, and high or low molecular weight glutenins. Additionally, several peptides carrying four previously discovered epitopes of γ-gliadin B precursor have been detected. These data were validated against the UniProt database, which contained 11764 Triticeae protein sequences. The identified allergens are discussed in relation to Baker's asthma, food allergy, wheat dependent exercise induced anaphylaxis, atopic dermatitis, and celiac disease (i.e., gluten-sensitive enteropathy). In summary, the results showed that the MS(E) approach is suitable for quantitative analysis and allergens profiling in wheat varieties and/or other food matrices.

About the role and underlying mechanisms of cofactors in anaphylaxis

Anaphylaxis is the systemic and most severe presentation of type I allergy. A number of conditions were identified that modulate the onset of anaphylaxis such as co- or augmentation factors, which significantly lower the allergen dose necessary for triggering anaphylaxis. Next to physical exercise or alcohol consumption, co-administration of nonsteroidal anti-inflammatory drugs (NSAID) or concomitant infectious diseases are well-documented cofactors of anaphylaxis. Registries for anaphylaxis document a role for cofactors in about 30% of anaphylactic reactions. Some disease entities such as 'wheat-dependent exercise-induced anaphylaxis' (WDEIA) are explicitly characterized by elicitation of anaphylaxis only in the presence of at least one such cofactor. Using WDEIA as a model disease, studies demonstrated that exercise increases skin prick test reactivity to and bioavailability of the allergen. Additional data indicate that alcohol consumption and NSAID administration display similar effects. Modulation of the cellular activation threshold is another mechanism underlying cofactor-induced anaphylaxis, most likely also functional when infectious diseases orchestrate elicitation of anaphylaxis. Cofactors are increasingly accepted to play a fundamental role in eliciting anaphylaxis. Consequently, to improve patient management modalities, a better understanding of the underlying mechanisms is warranted. This review aims to update clinicians and clinical scientists on recent developments.

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.

Lipid transfer proteins: the most frequent sensitizer in Italian subjects with food-dependent exercise-induced anaphylaxis

BACKGROUND

Specific food-dependent exercise-induced anaphylaxis (S-FDEIAn) is a distinct form of food allergy in which symptoms are elicited by exercise performed after ingesting food to which the patient has become sensitised. Non-specific FDEIAn (NS-FDEIAn) is a syndrome provoked by exercise performed after ingesting any food.

OBJECTIVE

We sought to identify the culprit allergenic molecules in patients with FDEIAn, combining 'classic' allergy testing with an allergenic molecule-based microarray approach for IgE detection.

METHODS

All subjects were evaluated who reported at least one episode of anaphylaxis in association with physical exercise performed within 4 h after a meal. We performed skin prick tests (SPT) with commercial food extracts, prick plus prick tests (P + P) with fresh foods (P + P), and serum specific IgE assays by means of both the ImmunoCAP (CAP) and the ISAC 89 microarray system (ISAC).

RESULTS

Among our 82 FDEIAn patients, the most frequent suspected foods were tomato, cereals, and peanut. SPT, P + P, and CAP displayed different degrees of sensitivity. Each test disclosed some positivities not discovered by others. Seventy-nine subjects were positive to at least one food (49 to more than 20), whereas three were negative. All suspected foods were positive to at least one of SPT, P + P, and CAP. When tested using the ISAC, 64 (78%) subjects were positive to Pru p 3 [peach lipid transfer protein (LTP)], 13 were positive to other food allergen molecules, and five displayed negative results to all food allergenic molecules. Overall, 79 patients probably had S-FDEIAn and the other 3 NS-FDEIAn.

CONCLUSIONS

Multiple food hypersensitivity represents a clinical hallmark of a large percentage of FDEIAn patients. The very high prevalence of IgE to the LTP suggests a role of this allergen group in causing S-FDEIAn.

Wheat-dependent exercise-induced anaphylaxis sensitized with hydrolyzed wheat protein in soap

Wheat-dependent exercise-induced anaphylaxis (WDEIA) is a specific form of wheat allergy typically induced by exercise after ingestion of wheat products. Wheat ω-5 gliadin is a major allergen associated with conventional WDEIA, and detection of serum immunoglobulin E (IgE) specific to recombinant ω-5 gliadin is a reliable method for its diagnosis. Recently, an increased incidence of a new subtype of WDEIA, which is likely to be sensitized via a percutaneous and/or rhinoconjunctival route to hydrolyzed wheat protein (HWP), has been observed. All of the patients with this new subtype had used the same brand of soap, which contained HWP. Approximately half of these patients developed contact allergy several months later and subsequently developed WDEIA. In each of these patients, contact allergy with soap exposure preceded food ingestion-induced reactions. Other patients directly developed generalized symptoms upon ingestion of wheat products. The predominant observed symptom of the new WDEIA subtype was angioedema of the eyelids; a number of patients developed anaphylaxis. This new subtype of WDEIA has little serum ω-5 gliadin-specific serum IgE.

IgE detection to α/β/γ-gliadin and its clinical relevance in wheat-dependent exercise-induced anaphylaxis

Wheat-dependent exercise-induced anaphylaxis (WDEIA) is characterized by anaphylactic reactions after wheat ingestion and physical exercise. IgE antibodies to recombinant ω(5) -gliadin are detectable in a majority of WDEIA patients, but other wheat allergens may also play a role in elicitation of WDEIA. Here, we performed a comprehensive analysis of IgE reactivity to different wheat proteins in 17 patients with confirmed WDEIA by ImmunoCAP research prototypes and a semi-quantitative microarray immunoassay with α/β/γ-gliadin, high-molecular-weight (HMW) glutenin, alpha-amylase inhibitor (AAI) dimer, and wheat lipid transfer protein (LTP). By ImmunoCAP, IgE to recombinant ω(5) -gliadin was detectable in 14/17 patients (82%), to α/β/γ-gliadin in 82% including the three patients lacking IgE to ω(5) -gliadin, and to HMW glutenin in 59%. The microarray revealed specifically γ-gliadin as the second most important allergen. These results demonstrate the additional diagnostic value of α/β- and γ-gliadin in particular in ω(5) -gliadin-negative patients in the diagnosis of WDEIA.

Allergy to deamidated gluten in patients tolerant to wheat: specific epitopes linked to deamidation

BACKGROUND

Gluten proteins can be modified by deamidation to enhance their solubility and technological applications. However, severe allergic reactions have been reported after the consumption of food products containing deamidated gluten (DG) in subjects tolerant to wheat. This work aimed to characterize allergen profiles for these patients in comparison with those of patients allergic to wheat and to identify IgE-binding epitopes.

METHODS

Sera were obtained from 15 patients allergic to DG and from nine patients allergic to wheat proteins (WP). IgE-binding profiles were characterized both in ELISA and in a humanized rat basophilic leukaemia (RBL) cell model. Epitopes were mapped on γ- and ω2-gliadin sequences by Pepscan, and effect of glutamine/glutamic acid substitutions was studied.

RESULTS

Compared to the heterogeneous pattern of allergens detected by IgE from patients allergic to WP, responses of patients allergic to DG were homogeneous. In ELISA, all the sera displayed IgE binding to deamidated γ- and ω2-gliadins and deamidated total gliadins, frequently with high concentrations. These modified proteins induced RBL degranulation with most of the sera from DG-allergic patients. A consensus epitope was found on native γ- and ω2-gliadins (QPQQPFPQ); it was repeated several times in their sequences. The substitution of two or three glutamines of this epitope into glutamic acid at positions Q3 or Q4 and Q8 (QPEEPFPE) increased its recognition the best.

CONCLUSION

Allergy to DG is a separate entity from wheat allergy. It can be evidenced by strong IgE binding to deamidated gliadins or peptides of the type QPEEPFPE.

Prevalence of wheat allergy in Japanese adults

BACKGROUND

Wheat is one of the most common causes of food allergies. The exact prevalence of wheat allergy has not been well delineated in Japanese adults.

METHODS

We enrolled 935 adults in a cohort study established by Shimane University in order to examine the determinants of lifestyle-related diseases. A screening was conducted by a questionnaire-based examination and a detection of serum omega-5 gliadin-specific IgE. Subjects who tested positive in the questionnaire-based examination and/or the serum omega-5 gliadin-specific IgE test were further examined by detailed interviews and skin prick tests.

RESULTS

A total of 22 subjects were picked up by the screening process, and 17 of these were further examined by secondary testing. Only two subjects were conclusively identified as having wheat allergy.

CONCLUSIONS

The prevalence of wheat allergy in Japanese adults was found to be 0.21% by using a combination of questionnaire-based examination, skin prick test and serum omega-5 gliadin-specific IgE test.

Comparison of oxidized and reduced glutathione in the bread-making qualities of rice batter

The demand for gluten-free bread is growing as the recognition of celiac disease and wheat allergy has increased worldwide. In our previous study, reduced glutathione (GSH) was found to improve the gas-retaining properties of rice batter used for gluten-free bread. In this article, oxidized glutathione (GSSG) was shown to have the same effect. Moreover, sensory tests revealed that GSSG bread had a significantly reduced sulfurous odor. Analyses by a gas chromatography-flame photometric detector demonstrated the presence of hydrogen sulfide and methyl mercaptan in the headspace of GSH bread, and also their significant reduction in GSSG bread. The viscoelastic properties and microstructures of GSSG and GSH bread did not noticeably differ. These observations suggest the usefulness of GSSG in making gluten-free rice bread and extend our knowledge of the use of glutathione in food processing. Practical Application: Glutathione, a widely-distributed peptide in cells, improves the bread-making quality of gluten-free rice batter. While both the reduced (GSH) and oxidized (GSSG) glutathione are effective, GSSG-bread has significantly reduced sulfurous odor compared to GSH-bread.

Food production and processing considerations of allergenic food ingredients: a review

Although most consumers show no adverse symptoms to food allergens, health consequences for sensitized individuals can be very serious. As a result, the Codex General Standard for the Labelling of Prepackaged Foods has specified a series of allergenic ingredients/substances requiring mandatory declaration when present in processed prepackaged food products. Countries adhering to international standards are required to observe this minimum of eight substances, but additional priority allergens are included in the list in some countries. Enforcement agencies have traditionally focused their effort on surveillance of prepackaged goods, but there is a growing need to apply a bottom-up approach to allergen risk management in food manufacturing starting from primary food processing operations in order to minimize the possibility of allergen contamination in finished products. The present paper aims to review food production considerations that impact allergen risk management, and it is directed mainly to food manufacturers and policy makers. Furthermore, a series of food ingredients and the allergenic fractions identified from them, as well as the current methodology used for detection of these allergenic foods, is provided.

Microarray of allergenic component-based diagnosis in food allergy

PURPOSE OF REVIEW

The determination of specific IgE (sIgE) against allergenic components fixed in a solid support that is provided as a microarray of high capacity and allows a more precise evaluation in the food allergy diagnosis. In this review, we will analyze the results obtained to date with this technology applied to the component-based diagnosis of food allergy.

RECENT FINDINGS

Microarrays of proteins or glycoproteins allow us to know the profile of sensitization of a patient with food allergy. At present, a commercially available technique exists which allows sIgE to be detected against 103 allergenic molecules. Several laboratories worldwide have explored and optimized this technique for few allergen extracts and the results have been promising with high reliabilities and sensitivities and above all, good correlations with previous existing conventional assays.

SUMMARY

In recent years, as a result of advances in molecular biology, together with the development of new technologies of producing high-capacity solid-phase matrices such as microarrays, the diagnosis of food allergy has improved and the basic situation of analyzing sIgE against an allergenic source has now become real the possibility of analyzing sIgE against an allergenic protein or glycoprotein. This change has not only led to a more precise diagnosis of sensitization, but can also be used to explain the different hazards of certain molecular sensitizations, crossreactivity phenomena in many cases and can even change the clinical management according to the information provided. Further studies are clearly needed to evaluate more precisely the scope of this new technique.

Immunoglobulin-E-binding epitopes of wheat allergens in patients with food allergy to wheat and in mice experimentally sensitized to wheat proteins

BACKGROUND

At present, B cell epitopes involved in food allergy to wheat are known only for a few allergens and a few categories of patients.

OBJECTIVE

To characterize the epitopes of different wheat kernel allergens: α-, γ, ω2, and ω5-gliadin, a low-molecular-weight (LMW) glutenin subunit, and a lipid transfer protein (LTP1) recognized by allergic patients and by sensitized mice and provide further understanding of the role of structure in determining allergic response.

METHODS

Sera were obtained from 39 patients suffering from food allergy to wheat. BALB/c mice were sensitized to gliadins or LTP1 by intraperitoneal immunizations. Continuous epitopes bound by IgE were delineated by the Pepscan technique. The response to reduced, alkylated LTP1 was compared with that of the native form to evaluate the importance of protein folding on IgE reactivity.

RESULTS

Few continuous epitopes of LTP1 reacted with IgE from allergic patients and mice, but one of them was common to several patients and sensitized mice. The unfolded protein was not recognized by either patient or mouse IgE, emphasizing the major role of LTP1 folding and discontinuous epitopes in IgE-binding. In contrast, many continuous epitopes were detected by patient and mouse IgE especially for an ω5-gliadin, which is an unstructured protein, and to a lesser extent, for the other gliadins and a LMW-glutenin subunit.

CONCLUSION AND CLINICAL RELEVANCE

The conformation of LTP1 appeared to have a strong impact on the type of IgE-binding epitopes elicited by this protein in both man and mouse. The responses in mice sensitized to gliadins or LTP1 were sufficiently comparable with the human response in terms of IgE-binding epitopes to provide support for the use of the mouse model in further investigations.

The diagnosis of food allergy

BACKGROUND

Food allergy is increasingly common; however, there is a discrepancy between the large number of people who believe they or their children are affected and the actual number with true food allergies. It is therefore imperative that physicians evaluating patients with possible adverse reactions to foods understand the current modalities used to diagnose food allergies.

METHODS

Simple tests including skin-prick testing (SPT) and serum food-specific IgE testing are the most commonly used diagnostic tests to evaluate for IgE-mediated food reactions. However, these tests have pitfalls and their usefulness must be appreciated to avoid over- and underdiagnosis.

RESULTS

A firm diagnosis is imperative because a misdiagnosis could lead to life-threatening reactions and overdiagnosis will lead to unnecessary elimination diets with nutritional and social implications. Physician-supervised oral food challenges (OFC) remain the gold standard for food allergy diagnosis; however, a careful medical history and simple tests can often provide a reliable diagnosis.

CONCLUSION

In this review, we examine the usefulness and pitfalls of SPT used by allergists and serum food-specific IgE levels that are available to all practitioners. We also review the OFC as a diagnostic modality in food allergy. Finally, we describe emerging tests, such as the basophil activation test, atopy patch testing, and component-resolved diagnostics, that may be of benefit in the future.

Identification of IgE-reactive proteins in patients with wheat protein contact dermatitis

BACKGROUND

Wheat protein and its derivatives can cause protein contact dermatitis (PCD), which mainly occurs in bakers. Few studies have attempted to identify the allergens responsible for wheat PCD.

OBJECTIVES

The aim of this study was to identify allergenic wheat proteins in patients with wheat PCD.

METHODS

Water-soluble and water-insoluble wheat flour proteins were separated by 1- or 2-dimensional gel electrophoresis. IgE-binding proteins were detected by immunoblotting with sera from 3 wheat PCD patients and identified by N-terminal amino acid sequence analysis. The IgE-binding proteins were recombinantly expressed in Escherichia coli and tested against patients' sera.

RESULTS

IgE antibodies from the patients' sera reacted with water-soluble proteins rather than water-insoluble proteins, and the 2-dimensional electrophoresis and immunoblotting produced individual IgE-binding patterns. Analysis of the N-terminal amino acid sequence of the IgE-binding proteins from the 2-dimensional gel led to the identification of three glycoproteins, wheat 27-kDa allergen, peroxidase, and purple acid phosphatase. No specific IgE antibodies to their non-glycosylated recombinant proteins were observed.

CONCLUSIONS

We identified wheat 27-kDa allergen, peroxidase and purple acid phosphatase as candidate allergens for wheat PCD. Our results suggest that glycan moieties in these proteins are involved in IgE binding.

Identification of IgE sequential epitopes of lentil (Len c 1) by means of peptide microarray immunoassay

BACKGROUND

Lentils are often responsible for allergic reactions to legumes in Mediterranean children. Although the primary sequence of the major allergen Len c 1 is known, the location of the IgE-binding epitopes remains undefined.

OBJECTIVE

We sought to identify IgE-binding epitopes of Len c 1 and relate epitope binding to clinical characteristics.

METHODS

One hundred thirty-five peptides corresponding to the primary sequence of Len c 1 were probed with sera from 33 patients with lentil allergy and 15 nonatopic control subjects by means of microarray immunoassay. Lentil-specific IgE levels, skin prick test responses, and clinical reactions to lentil were determined. Epitopes were defined as overlapping signal above interslide and intraslide cutoffs and confirmed by using inhibition assays with a peptide from the respective region. Hierarchic clustering of microarray data was used to correlate binding patterns with clinical findings.

RESULTS

The patients with lentil allergy specifically recognized IgE-binding epitopes located in the C-terminal region between peptides 107 and 135. Inhibition experiments confirmed the specificity of IgE binding in this region, identifying different epitopes. Linkage of cluster results with clinical data and lentil-specific IgE levels displayed a positive correlation between lentil-specific IgE levels, epitope recognition, and respiratory symptoms. Modeling based on the 3-dimensional structure of a homologous soy vicilin suggests that the Len c 1 epitopes identified are exposed on the surface of the molecule.

CONCLUSION

Several IgE-binding sequential epitopes of Len c 1 have been identified. Epitopes are located in the C-terminal region and are predicted to be exposed on the surface of the protein. Epitope diversity is positively correlated with IgE levels, pointing to a more polyclonal IgE response.

Molecular diagnosis in allergy

Development and progress made in the field of recombinant allergens have allowed for the development of a new concept in allergy diagnosis, molecular diagnosis (MD), which makes it possible to identify potential disease-eliciting molecules. Microarray-based testing performed with a small amount of serum sample enables clinicians to determine specific-IgE antibodies against multiple recombinants or purified natural allergen components. Performance characteristics of allergens so far tested are comparable with current diagnostic tests, but have to be confirmed in larger studies. The use of allergen components and the successful interpretation of test results in the clinic require some degree of knowledge about the basis of allergen components and their clinical implications. Allergen components can be classified by protein families based on their function and structure. This review provides a brief overview of basic information on allergen components, recombinants or purified, currently available or soon to become commercially available in ImmunoCAP or ISAC systems, including names, protein family and function. Special consideration is given to primary or species-specific sensitization and possible cross-reactivity, because one of the most important clinical utility of MD is its ability to reveal whether the sensitization is genuine in nature (primary, species-specific) or if it is due to cross-reactivity to proteins with similar protein structures, which may help to evaluate the risk of reaction on exposure to different allergen sources. MD can be a support tool for choosing the right treatment for the right patient with the right timing. Such information will eventually give clinicians the possibility to individualize the actions taken, including an advice on targeted allergen exposure reduction, selection of suitable allergens for specific immunotherapy, or the need to perform food challenges. Nevertheless, all in vitro tests should be evaluated together with the clinical history, because allergen sensitization does not necessarily imply clinical responsiveness.

Improvements in the bread-making quality of gluten-free rice batter by glutathione

The wide prevalence of celiac disease and wheat allergy has led to a growing demand for gluten-free foods. Rice proteins do not possess the viscoelastic properties typically found in gluten, thus making rice flour unsuitable for the production of yeast-leavened products. In the present study, we found that the addition of glutathione to rice batter improves its gas-retaining properties. Glutathione was found to prevent the formation of the disulfide-linked macromolecular protein barrier, which is reported to confer resistance to the deformation of rice batter in the baking process. Also, glutathione appeared to gelatinize rice starch at lower temperatures. Microstructure analyses of glutathione-added rice bread revealed it to have a perforated structure like wheat bread but with a smoother-looking surface. These data collectively suggest that glutathione facilitates the deformation of rice batter, thus increasing its elasticity in the early stages of bread baking and the volume of the resulting bread.

Component-resolved allergy diagnosis by microarray: potential, pitfalls, and prospects

Diagnosis of IgE-mediated allergies is not always straightforward, as traditional tests can yield equivocal or negative results and provocation tests are hampered by several practical and ethical limitations. During the last decades two new in vitro techniques have entered the field of allergy diagnosis, that is, flow-assisted analysis of allergen-specific activated basophils and component-resolved diagnosis (CRD). This review focuses on component-resolved allergy diagnosis by microarray that has evolved from recent advances in molecular allergology and biochip technology. The technique allows a comprehensive analysis of individual sensitization profiles with multiplexed purified and recombinant allergens within a single run using only a minute amount of serum, providing information that largely exceeds the output from current sIgE capturing tools. Actually, multiplexing allows identification of diagnostic patterns that may facilitate the formulation of diagnostic algorithms. Although CRD by microarray sounds promising, the diagnostic performance requires further intensive assessment before it can enter mainstream application. In our opinion, the technique should currently be considered a complementary diagnostic tool rather than a first-line choice.

Microarrays: molecular allergology and nanotechnology for personalised medicine (I)

The diagnosis of antibody-mediated allergic disorders is based on the clinical findings and the detection of allergen-specific IgE based on in vitro and in vivo techniques, together with allergen provocation tests. In vitro diagnostic techniques have progressed enormously following the introduction of the advances made in proteomics and nanotechnology--offering tools for the diagnosis and investigation of allergy at molecular level. The most advanced developments are the microarray techniques, which in genomics allowed rapid description of the human genetic code, and which now have been applied to proteomics, broadening the field for research and clinical use. Together with these technological advances, the characterisation of most of the different proteins generating specific IgE and which conform each natural allergen, as well as their purification or genetic engineering-based synthesis, have been crucial elements--offering the possibility of identifying disease-causing allergens at molecular level, establishing a component-resolved diagnosis (CRD), using them to study the natural course of the disease, and applying them to improvements in specific immunotherapy. Microarrays of allergic components offer results relating to hundreds of these allergenic components in a single test, and use a small amount of serum that can be obtained from capillary blood. The availability of new molecules will allow the development of panels including new allergenic components and sources, which will require evaluation for clinical use. The present study reviews these new developments, component-resolved diagnosis, and the development of microarray techniques as a critical element for furthering our knowledge of allergic disease.

Measurement of IgE antibodies to shrimp tropomyosin is superior to skin prick testing with commercial extract and measurement of IgE to shrimp for predicting clinically relevant allergic reactions after shrimp ingestion

BACKGROUND

Shrimp is a frequent cause of food allergy. Tropomyosin is the major allergen in shrimp, and it shares homology to tropomyosins from other crustaceans, dust mites, cockroach, and parasites.

OBJECTIVE

The aim of this study was to determine the value of detection of IgE to shrimp tropomyosin in the diagnosis of shrimp allergy.

METHODS

We have studied 35 patients with asthma, rhinitis, or both who were sensitized to Dermatophagoides pteronyssinus. All subjects underwent skin prick testing in addition to double-blind, placebo-controlled food challenges (DBPCFC); oral open challenges; or both with shrimp. Measurements of IgE to shrimp and shrimp tropomyosin were carried out by means of CAP and chimeric ELISA, respectively.

RESULTS

Oral challenges confirmed the diagnosis of shrimp allergy in 7 patients. IgE measurement to shrimp tropomyosin was positive in 71.4% of the patients with shrimp allergy. Of the 28 patients without shrimp allergy, only 7.1% (2/28) had IgE to shrimp tropomyosin compared with 25% (7/28) who had IgE to shrimp and 35.7% (10/28) who had positive skin prick test responses to shrimp. Sensitivity was similar for all 3 methods (71.4%); in contrast, specificity of IgE to shrimp tropomyosin (92.8%) was greater than that of IgE to shrimp (75%) and skin prick testing (64.2%). With regard to diagnostic efficiency, measurement of IgE to shrimp tropomyosin was superior to measurement of IgE to shrimp and skin prick testing (88.5%, 74.2%, and 65.7%, respectively).

CONCLUSION

Use of measurements of IgE to shrimp tropomyosin provided added value to the diagnosis of shrimp allergy.

The prognosis of wheat hypersensitivity in children

The study was aimed to determine the natural history of wheat hypersensitivity, to define risk factors for persistent wheat hypersensitivity, and to evaluate the development of respiratory allergy in children with wheat hypersensitivity. The development and subsequent disappearance of wheat hypersensitivity, clinical findings, skin prick test (SPT) reactivity, and the development of allergic rhinoconjunctivitis and asthma were charted retrospectively in 28 children with wheat hypersensitivity proven by the open oral challenge at the median age of 21 months (range 6 to 75 months). Appearance of skin symptoms during the diagnostic wheat challenge was related to SPT-positive wheat hypersensitivity, while the appearance of gastrointestinal symptoms alone was associated with SPT-negative wheat hypersensitivity (p=0.002). Wheat was tolerated by 59%, 69%, 84%, and 96%, by age 4, 6, 10, and 16, respectively. Sensitization to gliadin with a SPT wheal of >or=5 mm at the time of the diagnostic challenge was associated with a slower course of recovery from wheat hypersensitivity (p=0.019), and a SPT wheal of >or=3 mm to gliadin at any time was associated with the development of asthma (p=0.022). SPT reactivity to wheat was associated with later SPT reactivity to birch pollen (p=0.001), and the development of allergic rhinoconjunctivitis (p=0.001). In conclusion, almost all children with wheat hypersensitivity can tolerate wheat by adolescence. Sensitization to gliadin is associated with a slower achievement of tolerance and an increased risk of asthma.

Food-dependent exercise-induced anaphylaxis -importance of omega-5 gliadin and HMW-glutenin as causative antigens for wheat-dependent exercise-induced anaphylaxis-

Food-dependent exercise-induced anaphylaxis (FDEIA) is a special form of food allergy where a food-intake alone does not induce any symptoms. However, allergic symptoms are elicited when triggering factors such as exercise or aspirin-intake are added after ingestion of the causative food. The most frequent causative foodstuff in Japan is wheat. The triggering factors, both exercise and aspirin-intake, facilitate allergen absorption from the gastrointestinal tract, resulting in allergic symptoms in the patients with wheat-dependent exercise-induced anaphylaxis (WDEIA). Analysis using purified wheat proteins revealed that approximately 80% of the patients with WDEIA have IgE reacting to omega-5 gliadin and the remaining of the patients to high molecular weight glutenin (HMW-glutenin). Simultaneous measurement of specific IgE to omega-5 gliadin and HMW-glutenin was found to be highly useful in diagnosing WDEIA compared with the routine diagnostic system for wheat.

Value of eight-amino-acid matches in predicting the allergenicity status of proteins: an empirical bioinformatic investigation

The use of biotechnological techniques to introduce novel proteins into food crops (transgenic or GM crops) has motivated investigation into the properties of proteins that favor their potential to elicit allergic reactions. As part of the allergenicity assessment, bioinformatic approaches are used to compare the amino-acid sequence of candidate proteins with sequences in a database of known allergens to predict potential cross reactivity between novel food proteins and proteins to which people have become sensitized. Two criteria commonly used for these queries are searches over 80-amino-acid stretches for >35% identity, and searches for 8-amino-acid contiguous matches. We investigated the added value provided by the 8-amino-acid criterion over that provided by the >35%-identity-over-80-amino-acid criterion, by identifying allergens pairs that only met the former criterion, but not the latter criterion. We found that the allergen-sequence pairs only sharing 8-amino-acid identity, but not >35% identity over 80 amino acids, were unlikely to be cross reactive allergens. Thus, the common search for 8-amino-acid identity between novel proteins and known allergens appears to be of little additional value in assessing the potential allergenicity of novel proteins.

Peptide array-based analysis of the specific IgE and IgG4 in cow's milk allergens and its use in allergy evaluation

Cow's milk (CM) is one of the major causes of food allergies in children. We constructed a peptide array consisting of a linear 16-mer peptide library with an offset of 3-mer, which corresponds to the primary sequences of six major CM allergens. The immune reactivity to cow's milk proteins diminishes with age and clinical tolerance commonly occurs. Although the central role of IgE in allergy is well established, the role of other specific antibody classes in obtaining immunotolerance is not well known. The hypothesis that patients become tolerant when they develop immunological changes particularly with the IgG4 isotype has been proposed. In this study, the binding pattern of the CM protein-specific IgE and IgG4 epitopes was measured using the peptide array with sera of 12 patients with persistent CM allergy (CMA), sera of 5 children who outgrew CMA, and sera of 7 CM-sensitized children without allergy symptoms. In CMA patients the IgG4/IgE fluorescence intensity ratios varied greatly from peptide to peptide, and the scatter plots of IgE versus IgG4 signals using significant IgE-binding peptides showed different distribution patterns. When setting the boundary line based on the IgG4/IgE ratio (IgG4/IgE=2), patients with persistent CMA and CM-sensitized children can be distinguished by the plot pattern of peptides. Furthermore, the number of peptide plots in these regions was less in children who outgrew CMA. The approach employed in this study will allow for the distinction between CMA and CM-sensitization, and will enable the estimation of CMA outgrow by monitoring the time elapsed data.

Identification of two pistachio allergens, Pis v 1 and Pis v 2, belonging to the 2S albumin and 11S globulin family

BACKGROUND

IgE-mediated allergic reactions to pistachio appear to be occurring more frequently; however, little is known about its allergenic proteins.

OBJECTIVE

We attempted to identify pistachio allergens and to clone the encoding genes.

METHODS

Pistachio proteins were extracted and separated by SDS-PAGE. Immunolabelling was performed with sera from 28 pistachio-allergic individuals. Proteins of interest were further analysed by Edman sequencing and mass spectrometry/mass spectrometry (MS/MS). In parallel, a cDNA library was generated from immature pistachios and screened with primers designed on the basis of internal sequences and peptide spectra. Full-length cDNA clones were isolated from the library and sequenced. Recombinant proteins were expressed and tested with sera from pistachio-allergic patients.

RESULTS

Nineteen out of 28 patients (68%) showed IgE binding to a 7 kDa protein fraction, while 14 (50%) showed specific IgE to a 32 kDa protein fraction. Analysis by Edman sequencing and MS/MS revealed that these proteins were homologue to the cashew nut allergens Ana o 3 and Ana o 2, respectively. Screening of the pistachio cDNA library resulted in isolation of novel protein cDNAs. Open-reading frame translation provided the complete amino acid sequences of two new allergenic pistachio proteins. Recombinant proteins were recognized by six out of six selected patients. Therefore, these new allergens were named Pis v 1 and Pis v 2 by the Allergen Nomenclature Subcommittee.

CONCLUSION

Novel allergens in pistachio, Pis v 1 and Pis v 2, which belong to 2S albumin and 11S globulin family, respectively, were isolated and the genes encoding these allergens were identified.

Wheat allergy

PURPOSE OF REVIEW

This review describes the diverse clinical manifestations of IgE-mediated allergy to ingested wheat and summarizes recent advances in characterization of clinically significant allergens and diagnostic workup.

RECENT FINDINGS

Recent population-based studies have shown the prevalence of wheat allergy and sensitization more precisely than past studies among small populations and in hospital settings. Intensive research has demonstrated the diverse profile of both water/salt-soluble and insoluble allergens involved in clinical types of wheat allergies determined depending on the patient age, the sensitization route, and the protein state during the exposure. Consequently, some new allergens, including nonspecific lipid transfer protein (Tri a 14), have been identified. For diagnosis, the role of water/salt-insoluble gliadins, particularly omega-5 gliadin, a major allergen of wheat-dependent, exercise-induced anaphylaxis, was assessed as compared with the results of oral challenges. The mechanisms of eliciting anaphylactic symptoms by exercise in wheat-dependent, exercise-induced anaphylaxis were speculated upon; one is the allergenicity strengthened by activated tissue transglutaminase and another is the increased absorption of allergens through the gastrointestinal tract.

SUMMARY

Findings of the recent studies show potential for more precise diagnosis in each clinical type of wheat allergies.

Antigen-induced expression of CD203c on basophils predicts IgE-mediated wheat allergy

BACKGROUND

For in vitro diagnosis of wheat allergy, specific IgE to wheat is known to be a poor predictive marker. Oral food challenge, the gold standard for the diagnosis, is accompanied by a risk of severe induced reactions. Reliable in vitro tests are needed to be developed for safe indication for oral challenge.

OBJECTIVE

We examined the utility of a basophil activation marker, CD203c, for the diagnosis of IgE-mediated wheat allergy.

METHODS

Fifty-eight children with suspected wheat allergy with positive CAP-FEIA to wheat were enrolled. On 70 occasions, the clinical distinction between patients with wheat allergy (WA) and patients tolerant to wheat (TW) was made by means of an oral food challenge test or recent history of immediate allergic reactions or tolerance after ingestion of wheat. Twelve replicate evaluations were performed in 9 patients over more than a 6-month interval. Thirty two patients on 43 occasions were diagnosed with WA and 27 were confirmed to be TW. One patient had both diagnoses 18 months apart. Peripheral blood was incubated with fractionated wheat extracts, purified native omega-5 gliadin (nOG5) and recombinant omega-5 gliadin (rOG5). Expression of CD203c on basophils was then analyzed by flow cytometry using a commercial kit.

RESULTS

All wheat proteins induced concentration-dependent enhancement of CD203c expression in WA, but did not in TW. The analysis of receiver operating characteristics (ROC) showed that nOG5-induced CD203c(high)% values provided the best power for discriminating between WA and TW, with a sensitivity of 85.0% and specificity of 77.0% at the cut-off level of 14.4%. AUC for CD203c with nOG5 were significantly higher than that for conventional CAP-FEIA, 0.89 and 0.73, respectively (p < 0.01).

CONCLUSIONS

Measurement of nOG-induced enhancement of CD203c on basophils is useful for the diagnosis of immediate wheat allergy in children.

Recombinant lipid transfer protein Tri a 14: a novel heat and proteolytic resistant tool for the diagnosis of baker's asthma

BACKGROUND

Baker's asthma is an important occupational allergic disease. Wheat lipid transfer protein (LTP) Tri a 14 is a major allergen associated with wheat allergy. No panel of wheat recombinant allergens for component-resolved diagnosis of baker's asthma is currently available.

OBJECTIVE

To evaluate the potential role of recombinant Tri a 14 as a novel tool for the diagnosis of baker's asthma, and to test the heat and proteolytic resistance of the wheat LTP allergen.

METHODS

A cDNA encoding Tri a 14 was isolated and sequenced, the recombinant allergen produced in Pichia pastoris and purified by chromatographic methods. Physicochemical and immunological comparison of the natural and recombinant forms of Tri a 14 was carried out by N-terminal amino acid sequencing, matrix-assisted laser desorption/ionization mass spectrometry, circular dichroism (CD) analysis, IgE immunodetection, and specific IgE determination and ELISA-inhibition assays using a pool or individual sera from 26 patients with baker's asthma. Thermal denaturation and simulated gastrointestinal digestion of both Tri a 14 forms were checked by spectroscopic and electrophoretic methods, respectively, and biological activity by basophil activation test (BAT).

RESULTS

Natural and recombinant Tri a 14 were similarly folded, as indicated by their nearly identical CD spectra and heat denaturation profiles. A high interclass correlation coefficient (0.882) was found between specific IgE levels to both Tri a 14 proteins in individual sera from baker's asthma patients, but a slightly lower IgE-binding potency of rTri a 14 was detected by ELISA-inhibition assays. Natural and recombinant Tri a 14 elicited positive BAT in two and one out of three patients, respectively. Heat denaturation profiles and simulated gastrointestinal digestion assays indicated that Tri a 14 displayed a high heat and digestive proteolytic resistance, comparable to those of peach Pru p 3, the model food allergen of the LTP family.

CONCLUSIONS

Recombinant Tri a 14 is a potential tool for baker's asthma diagnosis, based on its physicochemical and immunological similarity with its natural counterpart. Wheat Tri a 14 shows a high thermal stability and resistance to gastrointestinal digestion.

Salt-soluble proteins from wheat-derived foodstuffs show lower allergenic potency than those from raw flour

Salt-soluble proteins from wheat flour have been described as main allergens associated with both baker's asthma and food allergy. However, most studies have used raw flour as starting material, thus not considering potential changes in allergenic properties induced by the heat treatment and other industrial processing to produce wheat-derived foodstuffs. Salt extracts from different commercial wheat-derived products were obtained and their allergenic properties investigated by IgE-immunodetection, ELISA assays, and skin prick test. The IgE-binding capacity of salt-soluble proteins from commercial breads and cooked pastas was reduced around 50% compared with that of raw flour, the reduction being less dramatic in noncooked pastas and biscuits. Several wheat-derived foodstuffs showed major IgE-binding components of 20 and 35 kDa, identified as avenin-like and globulin proteins, respectively. These proteins, as well as most flour and bread salt-soluble proteins, were hydrolyzed when subjected to simulated gastrointestinal digestion. However, the digested products still exhibited a residual IgE-binding capacity. Therefore, processing of wheat flour to obtain derived foodstuffs decreases the IgE binding-capacity of the major salt-soluble wheat proteins. Moreover, simulated gastric fluid digestion further inactivates some heat-resistant IgE-binding proteins.

Soybean beta-conglycinin as the main allergen in a patient with food-dependent exercise-induced anaphylaxis by tofu: food processing alters pepsin resistance

BACKGROUND

Food-dependent exercise-induced anaphylaxis (FDEIA) due to soybeans is a rare disorder. The allergen responsible for FDEIA due to soybeans has not yet been determined.

OBJECTIVE

We characterized the clinical features of a patient with FDEIA due to tofu, who was well tolerant to drinking soy milk. We then sought to identify the responsible soybean allergen(s) in that patient. We further studied whether different stabilities of the allergen(s) to pepsin digestion between two soybean products are related to their clinical allergenicity.

METHODS

Skin prick tests and provocation tests using soybean products were performed to detect the responsible food and other factors that induced the allergic symptoms. Specific IgE to various soybean allergens were examined by ImmunoCAP, ELISA and protein microarray assays. Immunoblotting for soybeans and soybean products using the patient's serum was also performed. Soybean products were serially digested by pepsin to disclose the stability of the allergens.

RESULTS

Provocation with ingestion of tofu and exercise induced the allergic symptoms, while ingestion of soy milk and exercise did not. Immunoblot analysis, ELISA and protein microarray assay revealed that beta-conglycinin mainly reacts with IgE antibodies in the patient's serum. By immunoblot analysis, beta-conglycinin in soy milk completely disappeared after pepsin digestion within 20 min, whereas beta-conglycinin in tofu was almost intact after more than 120 min of pepsin digestion.

CONCLUSION

We identified beta-conglycinin as the causative allergen in a patient with FDEIA induced by tofu. The difference in resistance to pepsin digestion between tofu and soy milk suggests that the presence of undigested allergens in the digestive tract is a prerequisite for the development of FDEIA.