There are no published data on peanut sensitization in Egypt and the problem of peanut allergy seems underestimated. We sought to screen for peanut sensitization in a group of atopic Egyptian children in relation to their phenotypic manifestations.
We consecutively enrolled 100 allergic children; 2-10 years old (mean 6.5 yr). The study measurements included clinical evaluation for site of allergy, possible precipitating factors, consumption of peanuts (starting age and last consumption), duration of breast feeding, current treatment, and family history of allergy as well as skin prick testing with a commercial peanut extract, and serum peanut specific and total IgE estimation. Children who were found sensitized to peanuts were subjected to an open oral peanut challenge test taking all necessary precautions.
Seven subjects (7%) were sensitized and three out of six of them had positive oral challenge denoting allergy to peanuts. The sensitization rates did not vary significantly with gender, age, family history of allergy, breast feeding duration, clinical form of allergy, serum total IgE, or absolute eosinophil count. All peanut sensitive subjects had skin with or without respiratory allergy.
Peanut allergy does not seem to be rare in atopic children in Egypt. Skin prick and specific IgE testing are effective screening tools to determine candidates for peanut oral challenging. Wider scale multicenter population-based studies are needed to assess the prevalence of peanut allergy and its clinical correlates in our country.
IgE-mediated peanut allergy is a complex trait with strong heritability, but its genetic basis is currently unknown. Loss-of-function mutations within the filaggrin gene are associated with atopic dermatitis and other atopic diseases; therefore, filaggrin is a candidate gene in the etiology of peanut allergy.
To investigate the association between filaggrin loss-of-function mutations and peanut allergy.
Case-control study of 71 English, Dutch, and Irish oral food challenge–positive patients with peanut allergy and 1000 non peanut-sensitized English population controls. Replication was tested in 390 white Canadian patients with peanut allergy (defined by food challenge, or clinical history and skin prick test wheal to peanut ≥8 mm and/or peanut-specific IgE ≥15 kUL−1) and 891 white Canadian population controls. The most prevalent filaggrin loss-of-function mutations were assayed in each population: R501X and 2282del4 in the Europeans, and R501X, 2282del4, R2447X, and S3247X in the Canadians. The Fisher exact test and logistic regression were used to test for association; covariate analysis controlled for coexistent atopic dermatitis.
Filaggrin loss-of-function mutations showed a strong and significant association with peanut allergy in the food challenge–positive patients (P = 3.0 × 10−6; odds ratio, 5.3; 95% CI, 2.8-10.2), and this association was replicated in the Canadian study (P = 5.4 × 10−5; odds ratio, 1.9; 95% CI, 1.4-2.6). The association of filaggrin mutations with peanut allergy remains significant (P = .0008) after controlling for coexistent atopic dermatitis.
Filaggrin mutations represent a significant risk factor for IgE-mediated peanut allergy, indicating a role for epithelial barrier dysfunction in the pathogenesis of this disease.
Atopic dermatitis; filaggrin; IgE; peanut allergy; risk factor; AD, Atopic dermatitis; ALSPAC, Avon Longitudinal Study of Parents and Children; FLG, Filaggrin; OR, Odds ratio; SPT, Skin prick test; UK, United Kingdom
Open-label oral immunotherapy (OIT) protocols have been used to treat small numbers of patients with peanut allergy. Peanut OIT has not been evaluated in double-blind, placebo-controlled trials.
To investigate the safety and effectiveness of OIT for peanut allergy in a double blind, placebo-controlled study.
In this multicenter study, peanut-allergic children ages 1-16 years received OIT with peanut flour or placebo. Initial escalation, build-up, and maintenance phases were followed by an oral food challenge at approximately one year. Titrated skin prick tests (SPT) and laboratory studies were performed at regular intervals.
Twenty-eight subjects were enrolled in the study. Three peanut OIT subjects withdrew early in the study due to allergic side effects. During the double-blind, placebo-controlled food challenge, all remaining peanut OIT subjects (N=16) ingested the maximum cumulative dose of 5000 mg (approximately 20 peanuts), while placebo subjects (N=9) ingested a median cumulative dose of 280 mg (range, 0-1900 mg) [p<0.001]. In contrast to the placebo group, the peanut OIT group showed reductions in SPT size (p<0.001), IL-5 (p=0.01), and IL-13 (p=0.02) and increases in peanut-specific IgG4 (p<0.001). Peanut OIT subjects had initial increases in peanut-specific IgE (p<0.01) but did not show significant change from baseline by the time of OFC. The ratio of FoxP3 hi: FoxP3 intermediate CD4+CD25+ T cells increased at the time of OFC (p=0.04) in peanut OIT subjects.
These results conclusively demonstrate that peanut OIT induces desensitization and concurrent immune modulation. The present study continues and is evaluating the hypothesis that peanut OIT causes long-term immune tolerance.
peanut allergy; oral immunotherapy; desensitization; food allergy
The botanical relation between grass and cereal grains may be relevant when diagnosing food allergy to cereals. The aim was to investigate the diagnostic specificity of skin prick test (SPT) and specific immunoglobulin E (sIgE) tests to cereals and peanut in grass pollen allergic subjects without history of, and clinically reactions to foods botanically related to grass.
70 subjects (41 females; mean age 32 years) and 20 healthy controls (13 females; mean age 24 years) were tested by open food challenge (OFC) with cereals and peanut. SPT and sIgE both with Immulite® (Siemens) and ImmunoCAP® (Phadia) to grass and birch pollen, cereals, peanut and bromelain were performed.
Of the 65 OFC-negative subjects 29-46% (SPT, depending on cut-off), 20% (Immulite) and 38% (ImmunoCAP) had positive results to one or more of the foods tested. Controls were negative in all tests. Cross-reactive carbohydrate determinants (CCD) as evidenced by reaction to bromelain could explain only a minority of the measured IgE-sensitizations.
Grass pollen allergic patients with documented food tolerance to cereals and peanut may express significant sensitization. False-positive cereal or peanut allergy diagnoses may be a quantitatively important problem both in routine clinical work and epidemiological studies.
Cereals; cross-reaction; diagnosis; food challenge; grass pollen allergy
Peanut allergy is relatively common, typically permanent, and often severe. Double-blind, placebo-controlled food challenge is considered the gold standard for the diagnosis of food allergy–related disorders. However, the complexity and potential of double-blind, placebo-controlled food challenge to cause life-threatening allergic reactions affects its clinical application. A laboratory test that could accurately diagnose symptomatic peanut allergy would greatly facilitate clinical practice.
We sought to develop an allergy diagnostic method that could correctly predict symptomatic peanut allergy by using peptide microarray immunoassays and bioinformatic methods.
Microarray immunoassays were performed by using the sera from 62 patients (31 with symptomatic peanut allergy and 31 who had outgrown their peanut allergy or were sensitized but were clinically tolerant to peanut). Specific IgE and IgG4 binding to 419 overlapping peptides (15 mers, 3 offset) covering the amino acid sequences of Ara h 1, Ara h 2, and Ara h 3 were measured by using a peptide microarray immunoassay. Bioinformatic methods were applied for data analysis.
Individuals with peanut allergy showed significantly greater IgE binding and broader epitope diversity than did peanut-tolerant individuals. No significant difference in IgG4 binding was found between groups. By using machine learning methods, 4 peptide biomarkers were identified and prediction models that can predict the outcome of double-blind, placebo-controlled food challenges with high accuracy were developed by using a combination of the biomarkers.
In this study, we developed a novel diagnostic approach that can predict peanut allergy with high accuracy by combining the results of a peptide microarray immunoassay and bioinformatic methods. Further studies are needed to validate the efficacy of this assay in clinical practice.
Epitope mapping; peptide microarray; peanut allergy; bioinformatics; machine learning; allergy diagnosis; epitope biomarker
The objective of this study was to determine the risk of peanut allergy in siblings of peanut-allergic children. In 2005-2006, 560 households of children born in 1995 in the province of Manitoba, Canada, were surveyed. The index children (8-to 10-year-olds) were assessed by a pediatric allergist and had skin-prick testing and/or capRAST for peanut allergy. Surveys were completed by parents for siblings to determine the presence of peanut allergy. Of 560 surveys, 514 (92%) were completed. Twenty-nine (5.6%) index children were peanut allergic. Fifteen of 900 (1.7%) siblings had peanut allergy. Four of 47 (8.5%) were siblings of peanut-allergic children and 11 of 853 (1.3%) were siblings of non-peanut-allergic children. The risk of peanut allergy was markedly increased in siblings of a peanut-allergic child (odds ratio 6.72, 95% confidence interval 2.04-22.12). Siblings of peanut-allergic children are much more likely to be allergic to peanut. An allergy assessment by a qualified allergist should be routinely recommended before feeding peanut to these children.
allergy tests; cohort study; odds ratio; peanut allergy; siblings
There are no treatments currently available for peanut allergy. Sublingual immunotherapy is a novel approach to the treatment of peanut allergy.
To investigate the safety, clinical effectiveness and immunologic changes with sublingual immunotherapy in peanut-allergic children.
In this double-blind, placebo-controlled study, subjects underwent 6 months of dose escalation and 6 months of maintenance dosing followed by a double-blind, placebo-controlled food challenge.
Eighteen children ages 1 to 11 years completed 12 months of dosing and the food challenge. Dosing side effects were primarily oropharyngeal and uncommonly required treatment. During the double-blind, placebo-controlled food challenge, the treatment group safely ingested 20 times more peanut protein than the placebo group (median 1710 mg vs. 85 mg, p=0.011). Mechanistic studies demonstrated a decrease in prick skin test wheal size (p=0.020) and decreased basophil responsiveness after stimulation with 10−2 mcg/ml (p=0.009) and 10−3 mcg/ml (p=0.009) of peanut. Peanut-specific IgE increased over the initial 4 months (p=0.002) then steadily decreased over the remaining 8 months (p=0.003) while peanut-specific IgG4 increased during the 12 months (p=0.014). Lastly, IL-5 levels decreased after 12 months (p=0.015). No statistically significant changes were found in IL-13 levels, the percent of T regulatory cells, or IL-10 and IFN-gamma production.
Peanut sublingual immunotherapy is able to safely induce clinical desensitization in peanut allergic children with evidence of immunologic changes suggesting a significant change in the allergic response. Further study is required to determine if continued peanut sublingual immunotherapy is able to induce long-term immune tolerance.
peanut allergy; sublingual immunotherapy; desensitization; food allergy
Prenatal factors may contribute to the development of peanut allergy. We evaluated the risk of childhood peanut allergy in association with pregnancy exposure to Rh immune globulin, folic acid and ingestion of peanut-containing foods.
We conducted a web-based case-control survey using the Anaphylaxis Canada Registry, a pre-existing database of persons with a history of anaphylaxis. A total of 1300 case children with reported peanut allergy were compared to 113 control children with shellfish allergy. All were evaluated for maternal exposure in pregnancy to Rh immune globulin and folic acid tablet supplements, as well as maternal avoidance of dietary peanut intake in pregnancy.
Receipt of Rh immune globulin in pregnancy was not associated with a higher risk of peanut allergy (odds ratio [OR] 0.86, 95% confidence interval [CI] 0.51 to 1.45), nor was initiation of folic acid tablet supplements before or after conception (OR 0.53, 95% CI 0.19 to 1.48). Complete avoidance of peanut-containing products in pregnancy was associated with a non-significantly lower risk of peanut allergy (OR 0.53, 95% CI 0.27 to 1.03).
The risk of childhood peanut allergy was not modified by the following common maternal exposures in pregnancy: Rh immune globulin, folic acid or peanut-containing foods.
Rh immune globulin, folic acid supplement use and peanut avoidance in pregnancy have yet to be proven to modulate the risk of childhood anaphylaxis to peanuts.
Identification of prenatal factors that contribute to peanut allergy might allow for prevention of this life-threatening condition. This article explores the role of three such factors.
Allergy; peanut; shellfish; prenatal; antenatal; pregnancy; folic acid; Rh immune globulin; survey
Peanut-allergic children might be at risk for reactions to other legumes. However, it is not always possible to perform multiple oral food challenges in children. On the basis of patient case history, in vitro diagnostic tests, and eventually food challenges, we aimed at developing an algorithm for risk assessment of possible clinical reactions to other legumes (soybean, lupine, fresh, and blanched green pea). Seventy-five consecutive patients with a positive oral food challenge to peanut were included in the study. All tests were run as part of the routine allergy examination. A high proportion of patients and/or caretakers refused the administered legume oral food challenges. Obtained diagnoses from histamine release did not correlate significantly to the outcome of the algorithm. Interestingly, threshold from peanut challenges did not correlate with the risk assessment.
The algorithm presented in this study can be used when advising peanut-allergic children and their caretakers about what other legumes to avoid in the diet.
cross-reactivity; histamine release; lupine; oral food challenge; pea; peanut allergy; skin prick test; soy; specific IgE
Sesame and coconut are emerging food allergens in the US. We sought to examine whether children allergic to peanuts and tree nuts are at increased risk of having an allergy to sesame or coconut. We performed a retrospective chart review of children who underwent skin prick testing (SPT) to sesame and coconut and identified 191 children who underwent SPT to sesame and 40 to coconut. Sensitization to sesame was more likely in children with positive SPT to peanuts (odds ratio [OR] = 6.7, 95% confidence interval [CI] [2.7–16.8], P<0.001) and tree nuts (OR = 10.5, 95% CI [4.0–27.7], P<0.001). Children with histories of both peanut and tree nut reaction were more likely to have a history of sesame reaction (OR = 10.2, 95% CI [2.7–38.7], P<0.001). Children with sensitization or allergy to peanuts or tree nuts were not more likely to be sensitized or allergic to coconut. In conclusion, children with peanut or tree nut sensitization were more likely to be sensitized to sesame but not coconut. Children with clinical histories of both peanut and tree nut allergy were more likely to be allergic to sesame.
sesame; coconut; peanut; tree nut; skin prick test; food allergy
OBJECTIVE: To determine the in vivo allergenicity of two grades of peanut oil for a large group of subjects with proved allergy to peanuts. DESIGN: Double blind, crossover food challenge with crude peanut oil and refined peanut oil. SETTING: Dedicated clinical investigation unit in a university hospital. SUBJECTS: 60 subjects allergic to peanuts; allergy was confirmed by challenge tests. OUTCOME MEASURES: Allergic reaction to the tested peanut oils. RESULTS: None of the 60 subjects reacted to the refined oil; six (10%) reacted to the crude oil. Supervised peanut challenge caused considerably less severe reactions than subjects had reported previously. CONCLUSIONS: Crude peanut oil caused allergic reactions in 10% of allergic subjects studied and should continue to be avoided. Refined peanut oil did not pose a risk to any of the subjects. It would be reasonable to recommend a change in labelling to distinguish refined from crude peanut oil.
Peanut allergy is the leading cause of food-related anaphylaxis and accidental exposures are common. Oral immunotherapy has been posited as a potential treatment.
Patients ages 3–65 with peanut-specific IgE ≥ 7 kU/L and/or a positive skin prick test with a history of an allergic reaction to peanut were recruited to undergo an oral immunotherapy protocol. All adverse reactions were recorded by research staff or patients in real time.
Twenty-four patients received 6662 doses. Symptoms have been mostly mild (84%) and only 3 severe gastrointestinal reactions required the administration of epinephrine. Abdominal pain has been the most common reaction, followed by oropharyngeal and lip pruritis. Respiratory symptoms have been rare.
In this trial of oral immunotherapy in adults and children, most reactions have been mild.
food allergy; oral immunotherapy; peanut allergy
Children with food-specific IgE (FSIgE) ≤2 kUa/L to milk, egg, or peanut (or ≤5kUa/L to peanut without history of previous reaction) are appropriate candidates for oral food challenge (OFC) to investigate resolution of food allergy, because these FSIgE cutoffs are associated with ∼50% likelihood of negative OFC. This study was designed to identify characteristics of children undergoing OFC, based on these FSIgE levels, who are most likely to show negative OFC. We collected demographics, severity of previous reaction, history of atopic diseases, total IgE and FSIgE values, and skin tests results on children who underwent OFCs to milk, egg, or peanut, based on the recommended FSIgE cutoffs. We identified independent factors associated with negative OFCs. Four hundred forty-four OFCs met our inclusion criteria. The proportions of negative OFCs performed based on FSIgE cutoffs alone were 58, 42, and 63% to milk, egg, and peanuts, respectively. Regression models identified independent factors associated with negative OFCs: lower FSIgE levels (all three foods), higher total IgE (milk), consumption of baked egg products (egg), and non-Caucasian race (eggs and peanuts). Combinations of these factors identified subgroups of children with proportions of negative OFCs of 83, 75, and 75% for milk, eggs, and peanuts, respectively. Combinations of clinical and laboratory elements, together with FSIgE values, might identify more children who are likely to have negative OFCs compared with current recommendations using FSIgE values alone. Once validated in a different population, these factors might be used for selection of patients who are most likely to show negative OFCs.
Children; food allergy; food specific IgE; oral food challenge; regression models; skin test; total IgE
The evaluation of soy allergy in patients over 14 years of age suffering from atopic dermatitis. The evaluation of the correlation to the occurence of peanut and pollen allergy.
Materials and Methods:
Altogether 175 persons suffering from atopic dermatitis were included in the study: Specific IgE, skin prick tests, atopy patch tests to soy, history and food allergy to peanut and pollen allergy were evaluated.
The early allergic reaction to soy was recorded in 2.8% patients. Sensitization to soy was found in another 27.2% patients with no clinical manifestation after soy ingestion. The correlation between the positive results of examinations to soy and between the occurence of peanut and pollen allergy was confirmed in statistics.
Almost one third of patients suffering from atopic dermatitis are sensitized to soy without clinical symptoms. The early allergic reaction to soy occur in minority of patients suffering from atopic dermatitis.
Atopic dermatitis; pollen allergy; peanut allergy; soy allergy; specific IgE; skin prick tests
A 47-year-old woman underwent bilateral lung transplantation for nonspecific interstitial pneumonitis and received donor lungs from a 12-year-old patient with a known peanut allergy. Post-transplant, the patient experienced four anaphylaxis-like reactions. A skin prick test to peanut was initially positive; however, it steadily declined over serial assessments and reverted to negative one year post-transplant. The patient subsequently had a negative oral peanut challenge. Transfer of food allergy post-transplantation is theorized to occur via transfer of donor B lymphocytes producing peanut-specific immunoglobulin E into the circulation of the recipient. An alternate mechanism proposes passive transfer of immunoglobulin E-sensitized mast cells and/or basophils within the transplanted tissue that subsequently migrate into recipient tissues. The gradual decline in the magnitude of the peanut skin prick test and its return to negative over the course of one year supports the gradual depletion of sensitized cells in the recipient (B lymphocytes and, possibly, mast cells), and supports the initial passive transfer of sensitized cells from donor tissue during transplantation. This should be considered when donor organs are obtained from allergic individuals.
Anaphylaxis; Basophil; Lung transplantation; Mast cell; Peanut
Oral immunotherapy (OIT) has been thought to induce clinical desensitization to allergenic foods, but trials coupling the clinical response and immunologic effects of peanut OIT have not been reported.
The study objective was to investigate the clinical efficacy and immunologic changes associated with OIT.
Peanut-allergic children underwent an OIT protocol including initial day escalation, build-up, and maintenance phases, and then oral food challenge. Clinical response and immunologic changes were evaluated.
Of 29 subjects who completed the protocol, 27 ingested 3.9 g peanut protein during food challenge. Most symptoms noted during OIT resolved spontaneously or with antihistamines. By 6 months, titrated skin prick tests and activation of basophils significantly declined. Peanut-specific IgE decreased by 12–18 months, while IgG4 increased significantly. Serum factors inhibited IgE–peanut complex formation in an IgE-facilitated allergen binding assay. Secretion of IL-10, IL-5, IFN-γ, and TNF-α from PBMCs increased over 6–12 months. Peanut-specific FoxP3 T cells increased until 12 months and then decreased thereafter. Additionally, T cell microarrays showed downregulation of genes in apoptotic pathways.
OIT induces clinical desensitization to peanut, with significant longer term humoral and cellular changes. Microarray data suggest a novel role for apoptosis in OIT.
Peanut hypersensitivity; immunotherapy; immune tolerance; apoptosis; immunoglobulin E; immunoglobulin G; interleukin-5; interleukin-10
Immune features of infants with food allergy have not been delineated.
To explore basic mechanisms responsible for food allergy and identify biomarkers, e.g. prick skin tests (PST), food-specific IgE, and mononuclear cell responses in a cohort of infants with likely milk/egg allergy at increased risk of developing peanut allergy.
Infants aged 3–15 months were enrolled with a positive PST to milk or egg and either a corresponding convincing clinical history of allergy to milk or egg, or with moderate to severe atopic dermatitis (AD). Infants with known peanut allergy were excluded.
Overall, 512 infants (67% males) were studied with 308 (60%) having a history of a clinical reaction. Skin tests and/or detectable food-specific IgE revealed sensitization as follows: milk-78%, egg-89% and peanut-69%. PST and food-specific IgE levels were discrepant for peanut: 15% IgE ≥ 0.35 kUA/L/PST- versus 8% PST+/IgE < 0.35, p = 0.001. Mononuclear cell allergen stimulation screening for CD25, CISH, FOXP3, GATA3, IL-10, IL-4, IFN-gamma and TBET expression using casein, egg white and peanut revealed that only allergen-induced IL-4 expression was significantly increased in those with clinical allergy to milk (compared to non-allergic) and in those sensitized to peanut, despite the absence of an increase in GATA-3 mRNA expression.
Infants with likely milk/egg allergy are at considerably high risk of having elevated peanut-specific IgE (potential allergy). Peanut-specific serum IgE was a more sensitive indicator of sensitization than PST. Allergen-specific IL-4 expression may be a marker of allergic risk. Absence of an increase in GATA-3 mRNA expression suggests that allergen-specific IL-4 may not be of T cell origin.
food allergy; sensitization; atopy
Food allergy affects approximately 5% of children and is the leading cause of hospitalization for anaphylactic reactions in westernized countries. However, the pathways of anaphylaxis in food allergy are still relatively unknown. We investigated the effector pathways of allergic and anaphylactic responses of different strains of mice in a clinical relevant model of peanut allergy. C3H/HeOuJ, C57BL/6 and BALB/c mice were sensitized by intragastric peanut extract and challenged by intragastric or intraperitoneal injection of peanut. Peanut-specific T cell responses, IgE, IgG1 and IgG2a and mucosal mast cell degranulation were induced to different extent in C3H/HeOuJ, C57BL/6 and BALB/c mice. Interestingly, anaphylactic symptoms after systemic challenge were highest in C3H/HeOuJ followed by C57BL/6 but were absent in BALB/c mice. Mechanistic studies showed that the food allergic systemic anaphylaxis was dependent on platelets, FcRγ and mast cells, and partially dependent on platelet activating factor and monocytes/macrophages, depending on mouse strain. These data demonstrate that in three mouse strains, components of the classic and alternative anaphylactic cascade are differently expressed, leading to differential outcomes in parameters of allergic disease and food induced systemic anaphylaxis.
OBJECTIVE--To investigate clinical features of acute allergic reactions to peanuts and other nuts. DESIGN--Analysis of data from consecutive patients seen by one doctor over one year in an allergy clinic at a regional referral centre. SUBJECTS--62 patients aged 11 months to 53 years seen between October 1993 and September 1994. MAIN OUTCOME MEASURES--Type and severity of allergic reactions, age at onset of symptoms, type of nut causing allergy, results of skin prick tests, and incidence of other allergic diseases and associated allergies. RESULTS--Peanuts were the commonest cause of allergy (47) followed by Brazil nut (18), almond (14), and hazelnut (13). Onset of allergic symptoms occurred by the age of 2 years in 33/60 and by the age of 7 in 55/60. Peanuts accounted for all allergies in children sensitised in the first year of life and for 82% (27/33) of allergies in children sensitised by the third year of life. Multiple allergies appeared progressively with age. The commonest symptom was facial angioedema, and the major feature accounting for life threatening reactions was laryngeal oedema. Hypotension was uncommon. Of 55 patients, 53 were atopic--that is, had positive skin results of tests to common inhaled allergens--and all 53 had other allergic disorders (asthma, rhinitis, eczema) due to several inhaled allergens and other foods. CONCLUSIONS--Sensitisation, mainly to peanuts, is occurring in very young children, and multiple peanut/nut allergies appear progressively. Peanut and nut allergy is becoming common and can cause life threatening reactions. The main danger is laryngeal oedema. Young atopic children should avoid peanuts and nuts to prevent the development of this allergy.
Peanut allergy affects 1% of the population and causes the most fatal food-related anaphylactic reactions. The protein Ara h 2 is the most potent peanut allergen recognized by 80–90% of peanut allergic patients.
The crystal structure of the major peanut allergen Ara h 2 was determined for the first time at 2.7 Å resolution using a customized MBP-fusion system. IgE antibody binding to the MBP fusion construct versus the natural allergen was compared by ELISA using sera from peanut allergic patients.
The structure of Ara h 2 is a five helix bundle held together by four disulfide bonds and related to the prolamin protein superfamily. The fold is most similar to other amylase and trypsin inhibitors. The MBP-Ara h 2 fusion construct was positively recognized by IgE from 76% of allergic patients (25/33). Two populations of patients could be identified. Sub-population 1 (n=14) showed an excellent correlation of IgE antibody binding to natural versus recombinant Ara h 2. Sub-population 2 (n=15) showed significantly reduced IgE binding to the MBP fusion protein. Interestingly, about 20% of the IgE binding in sub-population 2 could be recovered by increasing the distance between MBP and Ara h 2 in a second construct.
The reduced IgE binding to the MBP-Ara h 2 of sub-population 2 indicates that the MBP molecule protects an immunodominant epitope region near the first helix of Ara h 2. Residues involved in the epitope(s) are suggested by the crystal structure. The MBP-Ara h 2 fusion constructs will be useful to further elucidate the relevance of certain epitopes to peanut allergy.
Peanut; Allergy; Ara h 2; Immunotherapy; Structure
Food allergy is defined as an adverse immunologic response to a dietary protein. Food-related reactions are associated with a broad array of signs and symptoms that may involve many bodily systems including the skin, gastrointestinal and respiratory tracts, and cardiovascular system. Food allergy is a leading cause of anaphylaxis and, therefore, referral to an allergist for appropriate and timely diagnosis and treatment is imperative. Diagnosis involves a careful history and diagnostic tests, such as skin prick testing, serum-specific immunoglobulin E (IgE) testing and, if indicated, oral food challenges. Once the diagnosis of food allergy is confirmed, strict elimination of the offending food allergen from the diet is generally necessary. For patients with significant systemic symptoms, the treatment of choice is epinephrine administered by intramuscular injection into the lateral thigh. Although most children “outgrow” allergies to milk, egg, soy and wheat, allergies to peanut, tree nuts, fish and shellfish are often lifelong. This article provides an overview of the epidemiology, pathophysiology, diagnosis, management and prognosis of patients with food allergy.
Allergic reactions to peanuts (Arachis hypogaea L.) can cause severe symptoms and in some cases can be fatal, but avoidance is difficult due to the prevalence of peanut-derived products in processed foods. One strategy of reducing the allergenicity of peanuts is to alter or eliminate the allergenic proteins through mutagenesis. Other seed quality traits could be improved by altering biosynthetic enzyme activities. Targeting Induced Local Lesions in Genomes (TILLING), a reverse-genetics approach, was used to identify mutations affecting seed traits in peanut.
Two similar copies of a major allergen gene, Ara h 1, have been identified in tetraploid peanut, one in each subgenome. The same situation has been shown for major allergen Ara h 2. Due to the challenge of discriminating between homeologous genes in allotetraploid peanut, nested PCR was employed, in which both gene copies were amplified using unlabeled primers. This was followed by a second PCR using gene-specific labeled primers, heteroduplex formation, CEL1 nuclease digestion, and electrophoretic detection of labeled fragments. Using ethyl methanesulfonate (EMS) as a mutagen, a mutation frequency of 1 SNP/967 kb (3,420 M2 individuals screened) was observed. The most significant mutations identified were a disrupted start codon in Ara h 2.02 and a premature stop codon in Ara h 1.02. Homozygous individuals were recovered in succeeding generations for each of these mutations, and elimination of Ara h 2.02 protein was confirmed. Several Ara h 1 protein isoforms were eliminated or reduced according to 2D gel analyses. TILLING also was used to identify mutations in fatty acid desaturase AhFAD2 (also present in two copies), a gene which controls the ratio of oleic to linoleic acid in the seed. A frameshift mutation was identified, resulting in truncation and inactivation of AhFAD2B protein. A mutation in AhFAD2A was predicted to restore function to the normally inactive enzyme.
This work represents the first steps toward the goal of creating a peanut cultivar with reduced allergenicity. TILLING in peanut can be extended to virtually any gene, and could be used to modify other traits such as nutritional properties of the seed, as shown in this study.
The prevalence of peanut allergy in Korea is lower than in America. Peanut extract allergens between the two countries have not been standardized. This study was performed to compare the allergenicity of raw Korean and American peanuts with that of roasted peanuts. We prepared the peanut extracts in Korean raw (KP) and roasted peanuts (KRP), and also in American raw (AP) and roasted (ARP) peanuts. We compared the peanut extract allergens of KP, KRP, AP and ARP in vitro with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by immunoblotting, T-cell proliferation assay and skin prick test with sera from peanut-allergic patients. SDS-PAGE and Western blotting demonstrated four allergenic extracts, numerous bands that displayed a high prevalence of IgE binding. IgE-binding bands were at 64, 36 and 17 kDa. Western blot inhibition revealed that either KP or AP could almost completely inhibit the reactivity of the other extract. There were no differences between T-cell proliferation assay and skin prick test. In conclusion, this investigation showed no different allergic components in both raw and roast extracts of Korean and American peanuts.
A diagnosis of peanut allergy has a major impact on an individual’s quality of life. Exposure to even small amounts of peanut can trigger serious reactions. Common cleaning agents can easily remove peanut allergen from surfaces such as table tops. Parents of children with peanut allergy frequently ask if peanut allergen can persist on surfaces if they have not been cleaned.
The purpose of this study was to determine the persistence of peanut allergen on a typical table surface over time.
Five mL of peanut butter was evenly smeared on a 12 inch by 12 inch (30.5 by 30.5 cm) square on a nonporous (laminated plastic) table surface. Five squares were prepared in the same manner. The table was kept in a regular hospital office at room temperature and ambient lighting. No cleaning occurred for 110 days. Samples were taken at regular intervals from different areas each time. A monoclonal-based ELISA for arachis hypogaea allergen 1 (Ara h 1), range of detection 1.95-2000 ng/mL, was used to assess peanut allergen on the table surface.
At baseline, there was no detectable Ara h 1 allergen. Immediately post application and for 110 days of collecting, detectable Ara h 1 was found each time a sample was taken. There was no obvious allergen degradation over time. Active cleaning of the contaminated surface with a commercial cleaning wipe resulted in no detectable Ara h 1 allergen.
Peanut allergen is very robust. Detectable Ara h 1 was present on the table surface for 110 days. Active cleaning of peanut contaminated surfaces easily removed peanut residue and allergen. Regular cleaning of surfaces before and after eating should be reinforced as a safety measure for all individuals with peanut allergy.
Food allergy; Peanut allergen; Contamination; Ara h 1
Comparing lymphocyte responses to allergenic and nonallergenic foods could reveal the differences between pathogenic and normal immune responses to foods. Defining the cytokine-producing phenotypes of peanut-specific lymphocytes from peanut-allergic children, children who outgrew peanut allergy, and children who have always tolerated peanuts may be useful for understanding the mechanisms of food tolerance. Investigating immune responses against foods is hindered, however, by the fact that circulating food antigen–specific lymphocytes are very rare. In a novel approach we used carboxyfluorescein succinimidyl ester to detect peanut-specific lymphocytes by flow cytometry. We confirmed that these cells are indeed peanut specific by cloning. Peanut-allergic donors show Th2 polarization of cytokine production by peanut-specific cells (IFN-γ low, TNF-α low, IL-4 high, IL-5 high, IL-13 high). Conversely, nonallergic children and children who have outgrown their allergy show Th1 skewing to peanut antigens (IFN-γhigh, TNF-α high, IL-4 low, IL-5 low, IL-13low), similarly to nonallergenic food antigens (β-lactoglobulin, OVA). This finding suggests that peanut antigens do not intrinsically induce Th2 skewing, but that the type of response depends upon the donor’s allergic status. In conclusion, food allergic status is characterized by a Th2 response whereas Th1-skewed responses underlie oral tolerance.