Corn allergens: IgE antibody reactivity and cross-reactivity with rice, soy, and peanut

In vitro assessment of allergenicity features and localization of probable IgE binding regions

Rice is cultivated as a staple grain crop in many countries, especially in Asia. In the present study, recombinant rice chitinase was expressed, purified and characterized by in silico and immunobiochemical methods. Rice chitinase was affinity purified and it resolved at 24 kDa on SDS-PAGE. Purified protein was analyzed for pepsin resistance, heat stability, and IgE binding using atopic patients' sera. Chitinase was resistant to pepsin digestion and heat treatment at 90 °C for 1 h. It showed significant IgE binding with 7 of 110 patients' sera positive to different food allergens. Homology modeled 3D structure of rice chitinase was used for B cell epitope prediction. In silico predicted B cell peptides were assessed for IgE binding by ELISA using food allergic patients' sera, epitope RC2 showed IgE binding comparable to chitinase. In conclusion, chitinase was identified as a potential allergen and may share cross reactive epitopes with food allergens.

Identification of major rice allergen and their clinical significance in children

Purpose

Recently, an increase in the number of patients sensitized to rice allergen with or without clinical symptoms has been reported. This study was designed to determine the major allergens in rice and their clinical significance.

Methods

Twenty-four children (15 boys and 9 girls; mean age, 16.3 months) with allergic disease, who were sensitized to rice antigen (by UniCAP) in the Pediatric Allergy Respiratory Center at Soonchunhyang University Hospital, were enrolled in this study. The allergenicity of various types of rice (raw, cooked, and heat-treated, simulated gastric fluid [SGF], and simulated intestinal fluid [SIF]) was investigated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoglobulin E (IgE) immunoblots. The patients' medical records, including laboratory data and allergy symptoms after ingestion of rice were reviewed.

Results

Patients were sensitized to an average of 13.5 food antigens and their mean total IgE was 6,888.7 kU/L. In SDS-PAGE, more than 16 protein bands were observed in the raw rice, whereas only 14-16 kDa and 31-35 kDa protein bands were observed in cooked rice. The common SDS-PAGE protein bands observed in SGF-, SIF-, and heat-treated rice were 9, 14, and 31 kDa. In a heated-rice IgE immunoblot, protein bands of 9, 14, and 31-33 kDa were found in 27.8%, 38.9%, and 38.9% of all sera, respectively, and in 50%, 50%, and 75%, of ser a from the 4 symptomatic patients, respectively.

Conclusion

The 9-, 14-, and 31-kDa protein bands appeared to be the major allergens responsible for rice allergy symptoms.

An adjuvant free mouse model of oral allergenic sensitization to rice seeds protein

Background

Rice is commonly known as a staple crop consumed worldwide, though with several rice proteins being reported for allergic properties in clinical studies. Thus, there is a growing need for the development of an animal model to better understand the allergenicity of rice proteins and the immunological and pathophysiological mechanisms underlying the development of food allergy.

Methods

Groups of BALB/c mice were sensitized daily with freshly homogenized rice flour (30 mg or 80 mg) without adjuvant by intragastric gavage. In addition, the mice were challenged with extracted rice flour proteins at several time points intragastrically. Hypersensitivity symptoms in mice were evaluated according to a scoring system. Vascular leakage, ELISA of rice protein-specific IgE, histopathology of small intestine, and passive cutaneous anaphylaxis were conducted on challenged mice.

Results

An adjuvant free mouse model of rice allergy was established with sensitized mice showing increased scratching behaviors and increased vascular permeability. Rice protein-specific IgE was detected after eighteen days of sensitization and from the fifth challenge onwards. Inflammatory damage to the epithelium in the small intestine of mice was observed beyond one month of sensitization. Passive cutaneous anaphylaxis results confirmed the positive rice allergy in the mouse model.

Conclusions

We introduced a BALB/c mouse model of rice allergy with simple oral sensitization without the use of adjuvant. This model would serve as a useful tool for further analysis on the immunopathogenic mechanisms of the various rice allergens, for the evaluation of the hypersensitivity of rice or other cereal grains, and to serve as a platform for the development of immunotherapies against rice allergens.

Rice (Oryza sativa) allergy in rhinitis and asthma patients: a clinico-immunological study

Sensitization to foods varies in different countries reflecting a possible interaction of genetic factors, cultural and dietary habits. Rice is a major food consumed world wide and needs evaluation for IgE mediated reactions. The present study was carried out to identify rice allergy in patients of rhinitis and asthma and identify the allergenic proteins in raw and cooked rice. Of 1200 patients screened using standard questionnaire, 165 presented with history of rice allergy. Of these, 20 (12.1%) patients demonstrated marked positive skin prick test (SPT) and 13 showed significantly raised specific IgE to rice compared to normal controls. Double blind placebo controlled food challenge (DBPCFC) confirmed rice allergy in 6/10 patients. Immunoblot with hypersensitive individual patients' sera showed 14-16, 33, 56 and 60 kDa proteins as major IgE-binding components in rice. Boiled rice retained four IgE reactive proteins of 16, 23, 33 and 53 kDa. In summary, IgE-mediated rice allergy affects 0.8% [(0.42-1.58) at 95% CI] of asthma and rhinitis cases. The subjects with severe SPT reactions (4 mm or above) and specific IgE, 6.9 ng/ml to rice demonstrated positive blinded food challenge with clinical symptoms.

Proteome analysis of maize pollen for allergy-relevant components

Over the last few decades, the cultivation of maize (Zea mays) has strongly increased in Central Europe. We therefore decided to study the allergen composition and the allergenic potency of its pollen in comparison with pollen from timothy grass (Phleum pratense), a typical representative of the native grasses. We found that 65% of the sera reactive to timothy pollen also bound to maize pollen proteins. By using 2-DE immunoblotting, followed by incubation with mAbs directed against known allergens or protein sequencing, those IgE-reactive components were further classified. Although novel, maize-specific pollen allergens could not be found, the presence of crossreacting allergens belonging to groups 1 and 13 (Zea m 1 and 13), both having high IgE prevalence, as well as the presence of the less important group 3 and 12 allergens was found. The structural variability of Zea m 1 and Zea m 13 was determined by sequencing clones isolated from a maize pollen cDNA library. This revealed sequence identities of 72 and 70%, respectively, to the corresponding Phl p 1 and Phl p 13 allergens of timothy grass pollen. IgE-crossreactivity was further studied using immunoblot inhibition tests. Here, timothy pollen extract completely blocked IgE binding to maize, whereas maize pollen extract blocked IgE reactivity to only some timothy pollen allergens.

A hydrolysed rice-based formula is tolerated by children with cow's milk allergy: a multi-centre study

BACKGROUND

Children allergic to cow's milk are fed a soy- or a hydrolysed cow's milk-based substitute. Neither can rule out a sensitization risk. Previous studies have shown that hydrolysed rice is tolerated by animals and children with multiple food hypersensitivities.

OBJECTIVE

A prospective clinical assessment of tolerance to a rice-based hydrolysed formula was carried out in children allergic to cow's milk. Patients and methods One hundred children (42 girls and 58 boys, mean age 3.17+/-2.93 years, median 2.20, range 0.18-14.6 years) with a history of immediate reactions to cow's milk and confirmed at double-blind, placebo-controlled food challenge (DBPCFC) when not contraindicated were assessed for clinical tolerance to cow's milk proteins. Their allergy work-up included skin prick tests with whole milk, alpha-lactalbumin (ALA), beta-lactoglobulin (BLG) and total caseins, and specific IgE determinations using CAP technology were performed against whole milk, ALA, BLG and casein. Sensitization to rice and rice-based hydrolysed formula was similarly investigated. Patients' sera were evaluated at immunoblotting for specific IgE to cow's milk proteins, rice and rice-based hydrolysed formula. DBPCFC was carried out with increasing doses of a rice-based hydrolysed formula.

RESULTS

All patients were sensitized to cow's milk and/or at least one cow's milk protein fraction. Eighty-seven out of 99 were positive to cow's milk and/or a cow's milk protein fraction at skin prick test. Positive (>0.35 kUA/L) specific IgE determinations were found for cow's milk and/or milk fractions (92/95), rice (21/91) and hydrolysed rice infant formula (4/91). At immunoblotting, sera from 96 children were positive to alpha-casein (n=54), beta-casein (n=38), ALA (n=57), BLG (n=37) and bovine serum albumin (n=61). Similarly, although patients' sera often contained specific IgE against rice proteins at CAP (21/91) and immunoblotting (70/96), only six very weakly positive responses were observed against rice-based hydrolysed formula. All DBPCFC with rice-based hydrolysed formula were negative.

CONCLUSIONS

Rice-based hydrolysed formula is a possible alternative not only for children with multiple allergies, but also for children with cow's milk allergy.

Screening the allergenic repertoires of wheat and maize with sera from double-blind, placebo-controlled food challenge positive patients

BACKGROUND

Food allergy to wheat and maize is an increasing factor of deterioration of life quality, especially childhood and can, in rare cases, even induce anaphylaxis. Although omega-5 gliadin from wheat and maize lipid transfer protein have been characterized as major cereal allergens on the molecular level, the list of food allergens is far to be complete.

METHODS

To identify the IgE-binding repertoires of wheat and maize we screened respective cDNA libraries displayed on phage surface with sera from patients with a confirmed food allergy. The study included six patients with a positive double-blind, placebo-controlled food challenge (DBPCFC) to wheat, nine patients with a positive DBPCFC to maize, and six patients with anaphylactic reactions after ingestion of wheat.

RESULTS

The enriched sequences encoding IgE-binding proteins showed heterogeneous repertoires for both, wheat and maize. The selected wheat repertoire yielded 12, the maize repertoire 11 open reading frames. Among these we identified allergens belonging to already characterized allergens families, such as gliadin, profilin and beta-expansin. Besides, we found novel proteins with high cross-reactive potential, such as thioredoxins, as well as sequences that had so far not been related to cereal allergy at all. The IgE-binding capacity of some selected proteins was evaluated in vitro and cross-reactivity was demonstrated by competition ELISA.

CONCLUSION

With regard to the heterogeneity of the characterized sequences as well as to the biochemical nature of the new allergens detected we conclude that wheat and maize-related food allergy is more complex than so far anticipated.

Use of hydrolysates in the treatment of cow's milk allergy

BACKGROUND

Hydrolyzed formulas (HFs) are in general well tolerated by children with cow's milk allergy (CMA), although cases of allergic reactions have been reported and residual allergenicity of HF has been demonstrated

OBJECTIVE

To review the most relevant studies of the HFs for residual allergenicity, tolerance, and safety in the past 20 years.

DATA SOURCES AND METHODS

MEDLINE searches for the years 1970 to 2001 using the following algorithm (hydrolysate and allergy; food intolerance/allergy; protein hydrolysate).

RESULTS

The literature confirmed that although some antigenicity remains, HFs are well tolerated by children with CMA. Rice HF has proven safe when tested by double-blind, placebo-controlled food challenge in a study population of 18 children allergic both to cow's milk (CM) and soy protein.

CONCLUSIONS

Absolute avoidance of CM proteins means substitution by soy-, rice-, or amino acid-based formulas. As 8 to 14% of infants allergic to CM react to soy and amino acid-based formulas are expensive, scientific societies recommend the use of formulas based on extensively hydrolyzed CM proteins as first alternatives in children with CMA. Although both soy- and rice-based HFs have now been shown to be safe for these children, further nutritional and clinical studies are needed.

Severe oral allergy syndrome and anaphylactic reactions caused by a Bet v 1- related PR-10 protein in soybean, SAM22

BACKGROUND

Anaphylactic reactions to soy products have been attributed to stable class 1 food allergens.

OBJECTIVE

IgE- mediated reactions to a soy-containing dietary food product in patients allergic to birch pollen were investigated.

METHODS

Detailed case histories were taken from 20 patients. Their sera were analyzed for IgE (UniCAP) specific for birch, grass, mugwort, the recombinant birch allergens rBet v 1 and rBet v2, and soy protein. Extracts from birch pollen, soy isolate, rBet v 1, and the recombinant PR-10 soy protein rSAM22 were coupled to paper disks or nitrocellulose for IgE measurements (enzyme allergosorbent test) or Western blot analysis. Enzyme allergosorbent testing, Western blot inhibition, and histamine release studies were performed with the same allergens.

RESULTS

Most patients (17/20) experienced facial, oropharyngeal, and/or systemic allergic symptoms within 20 minutes after ingesting the soy product for the first time. Birch pollen allergy (16/20) was common, along with oral allergy syndrome to apple (12/20) or hazelnut (11/20). IgE levels to birch and Bet v 1 but not to other inhalants were high in 18 of 20 patients. Significant IgE binding to rSAM22 occurred in 17 of 20 patients. Blot experiments with the soy isolate revealed IgE-binding bands at 17 kd (15/20), 22 kd (1/20), and 35 to 38 kd (2/20); the former was inhibited by preincubation of the sera with rBet v 1 or rSAM22. Birch extract and soy isolate, rBet v 1, and rSAM22 induced dose-dependent histamine release in the nanomolar range.

CONCLUSION

Immediate-type allergic symptoms in patients with birch pollen allergy after ingestion of soy protein-containing food items can result from cross-reactivity of Bet v 1 -specific IgE to homologous pathogenesis-related proteins, particularly the PR-10 protein SAM22.