Consumer attitudes and risks associated with packaged foods having advisory labeling regarding the presence of peanuts

BACKGROUND: Foods with advisory labeling (eg, "may contain") are increasingly prevalent. Consumers with food allergies might ignore advisory labeling advice. OBJECTIVE: We sought to determine whether consumers with food allergy heeded advisory labels and whether products with advisory labels contained detectable peanut allergen. METHODS: Surveys (n = 625 in 2003 and n = 645 in 2006) were conducted at Food Allergy & Anaphylaxis Network patient conferences. Food products bearing advisory statements regarding peanuts were analyzed for the presence of peanut. RESULTS: Consumers were less likely to heed advisory labeling in 2006 (75%) compared with in 2003 (85%, P < .01); behavior varied significantly according to the form of the statement. Peanut protein was detected in 10% (20/200) of total food products bearing advisory statements, although clinically significant levels of peanut (>1 mg of peanut or >0.25 mg of peanut protein) were detected in only 13 of 200 such products. CONCLUSION: Consumers with food allergy are increasingly ignoring advisory labeling. Because food products with advisory labeling do contain detectable levels of peanuts, a risk exists to consumers choosing to eat such foods. The format of the labeling statement did not influence the likelihood of finding detectable peanut, except for products listing peanuts as a minor ingredient, but did influence the choices of consumers with food allergy. CLINICAL IMPLICATIONS: Allergic patients are taking risks by increasingly disregarding advisory labeling.     

Recent advances in peanut allergy

Peanut remains preeminent as the food allergen most associated with severe and fatal allergic reactions. Reactions are frequent despite patients' best efforts to avoid peanut. In the future, better information sharing and communication between families and both schools and restaurants may lead to a decrease in the rate of severe reactions induced by exposure to peanut outside the home. Reaction severity may increase over time but up to 25% of young peanut allergic individuals may outgrow their peanut allergy. Personalized care plans and education programmes may have an impact on avoidance of peanut and on the appropriate responses of caregivers. Peanut's allergenicity may be affected by the method of cooking, with roasted peanuts appearing more allergenic than boiled or fried peanuts. Immunotherapy with modified peanut allergens and DNA based vaccines may soon move from animal studies to clinical trials.     

Immunoassay of peanut allergens in food-processing materials and finished foods

To quantitate trace amounts of peanut allergens in food-processing materials and finished foods, we established a solid-phase radioimmunoassay inhibition using pooled sera from five peanut-sensitive subjects and a roasted peanut-meal extract covalently linked to polyacrylamide beads. Test samples were extracted, dialyzed, lyophilized, and reconstituted at 10 to 225 mg of dry weight per milliliter concentrations. The peanut-allergen content of test samples was expressed relative to a reference extract of roasted peanut meal that was assigned an arbitrary potency of 100,000 U/ml. In confectionery products spiked with varying quantities of peanut (0.7% to 0.0175%), the recovery of peanut allergen ranged from 31% to 94%. The sensitivity of the assay was 2.5 U/mg of dry weight from these samples (0.00875% peanut). Peanut allergens were undetectable in virgin vegetable oil used to roast peanuts, but 600 to 7600 U/mg of dry weight were present in oil after varying periods of use. The allergen content of used oil was reduced to 8 U/mg of dry weight by filtration and steam cleaning. The availability of such assays provides a means of monitoring finished food products for potential allergens. This monitoring in turn will provide the means to correlate symptoms experienced by sensitive patients with the exact quantity of allergen ingested. At the present time, there is little information on the quantities of ingested peanut allergen that pose risks to peanut-sensitive subjects.     

Distribution of peanut allergen in the environment

BACKGROUND: Patients with peanut allergy can have serious reactions to very small quantities of peanut allergen and often go to extreme measures to avoid potential contact with this allergen. OBJECTIVE: The purpose of this study was to detect peanut allergen under various environmental conditions and examine the effectiveness of cleaning agents for allergen removal. METHODS: A monoclonal-based ELISA for Arachis hypogaea allergen 1 (Ara h 1; range of detection, 30-2000 ng/mL) was used to assess peanut contamination on cafeteria tables and other surfaces in schools, the presence of residual peanut protein after using various cleaning products on hands and tabletops, and airborne peanut allergen during the consumption of several forms of peanut. RESULTS: After hand washing with liquid soap, bar soap, or commercial wipes, Ara h 1 was undetectable. Plain water and antibacterial hand sanitizer left detectable Ara h 1 on 3 of 12 and 6 of 12 hands, respectively. Common household cleaning agents removed peanut allergen from tabletops, except dishwashing liquid, which left Ara h 1 on 4 of 12 tables. Of the 6 area preschools and schools evaluated, Ara h 1 was found on 1 of 13 water fountains, 0 of 22 desks, and 0 of 36 cafeteria tables. Airborne Ara h 1 was undetectable in simulated real-life situations when participants consumed peanut butter, shelled peanuts, and unshelled peanuts. CONCLUSION: The major peanut allergen, Ara h 1, is relatively easily cleaned from hands and tabletops with common cleaning agents and does not appear to be widely distributed in preschools and schools. We were not able to detect airborne allergen in many simulated environments.     

Lupine-induced anaphylaxis in a child without known food allergy.

BACKGROUND: Lupine allergy is caused by ingestion of the flour of a plant called Lupinus albus, a member of the Leguminosae family. Lupine allergy has been described in adult patients previously known to have peanut allergy (cross-reactivity). OBJECTIVE: To describe the first case of an anaphylactic reaction caused by ingestion of lupine flour in a pediatric patient without a known peanut allergy. METHODS: Symptom assessment, nutritional history, and skin and blood tests. RESULTS: An otherwise healthy 8-year-old boy had nose and eye discharge followed by facial edema and difficulty breathing 30 minutes after eating an industrially prepared waffle containing eggs, sugar, and lupine flour. He had no history of food allergy and was eating a normal diet, including peanuts and other legumes. Results of skin prick tests using commercial extracts were positive to peanuts and negative to eggs, soy, and nuts; results of a prick-to-prick test using lupine flour were strongly positive (+ + + +). His total IgE level was 1,237 UI/mL. Specific IgE antibodies were positive to lupine seeds (20.8 kU/L) and peanuts (> 100 kU/L). CONCLUSIONS: To our knowledge, we describe the first case of an anaphylactic reaction after ingestion of lupine flour in a child without known allergy. In the case of peanut allergy or any anaphylactic reaction without evident cause, especially after industrially prepared food ingestion, lupine should be considered in the list of allergens tested. Lupine is increasingly used in industrially prepared food but is not regularly declared in the composition, leading to difficulties in allergen avoidance.     

Monitoring peanut allergen in food products by measuring Ara h 1

BACKGROUND: Peanut allergy is an important health problem in the United States, affecting approximately 0.6% of children. Inadvertent exposure to peanut is a risk factor for life-threatening food-induced anaphylaxis. OBJECTIVE: The purpose of this investigation was to develop an immunoassay for a major peanut allergen, Ara h 1, to detect peanut allergen in foods so that the risk of inadvertent exposure can be reduced. METHODS: A specific 2-site monoclonal antibody-based ELISA was developed to measure Ara h 1 in foods. The sensitivity of the assay was 30 ng/mL. Ara h 1 was measured in foods (n = 83) with or without peanut and in experiments to optimize allergen yield and to determine peanut contamination in spiked foods. RESULTS: Ara h 1 levels in food products ranged from less than 0.1 microg/g to 500 microg/g. Ara h 1 measured in ng/mL was transformed to microg/g for food products. Peanut butter contained the highest amounts of Ara h 1. Peanut extracts contained from 0.5 to 15 mg Ara h 1/g of peanut depending on the extraction conditions. Optimal extraction of Ara h 1 was obtained by using phosphate buffer with 1 mol/L NaCl and Tween at 60 degrees C. Ara h 1 was not always detected in presence of chocolate under the extraction conditions tested. Spiking experiments showed that the assay could detect approximately 0.1% Ara h 1 contamination of food with ground peanut. There was an excellent correlation between Ara h 1 levels and peanut content measured by using a commercial polyclonal antibody-based ELISA (r = 93, n = 31, P <.001). CONCLUSION: A new sensitive and specific monoclonal antibody-based ELISA was used to monitor Ara h 1 content in food products. This assay should be useful for monitoring peanut contamination in the food manufacturing and processing industry and in developing thresholds for sensitization or allergic reaction in persons with peanut allergy.     

The major peanut allergen,Ara h 2, functions as a trypsin inhibitor,and roasting enhances this function

BACKGROUND: The widespread use of peanut products, the severity of the symptoms, and its persistence in afflicted individuals has made peanut allergy a major health concern in western countries such as the United States, United Kingdom, and Canada. In a previous study, the authors showed that the allergenic properties of peanut proteins are enhanced as a result of thermal processing. OBJECTIVE: The purpose of this investigation was to determine whether any specific functions are associated with the major peanut allergen, Ara h 2, and whether the functionality of this protein is influenced by processing. An assay was developed and used to assess structure/function changes in Ara h 2 induced by roasting and the effect of these alterations on the allergenic properties of this major peanut allergen. METHODS: A protein domain homology search was used to determine possible functions for Ara h 2. One of the putative functions (protease inhibition) was tested by means of appropriate enzyme assays and protein gel electrophoresis. Circular dichroism was used to compare the structural properties of Ara h 2 purified from raw and roasted peanuts. RESULTS: Ara h 2 purified from peanuts is homologous to and functions as a trypsin inhibitor. Roasting caused a 3.6-fold increase in trypsin inhibitory activity. Functional and structural comparison of the Ara h 2 purified from roasted peanuts to native and reduced Ara h 2 from raw peanuts revealed that the roasted Ara h 2 mimics the behavior of native Ara h 2 in a partially reduced form. CONCLUSIONS: The data indicate that thermal processing might play an important role in enhancing the allergenic properties of peanuts. Not only has it previously been shown to affect the structural and allergic properties of peanut proteins but also, for the first time, the functional characteristics of an allergen. These structural and functional alterations are likely to influence the allergenicity of peanuts.     

Digested Ara h 1 has sensitizing capacity in Brown Norway rats

Background Food allergies are a public health issue of growing concern, with peanuts in particular being associated with severe reactions. The peanut allergen, Ara h 1, belongs to the cupin plant food allergen family, which, unlike other structural families, appears to be broken down rapidly following gastrointestinal digestion.
Objective Using Ara h 1 as a model allergen, the ability of digested protein to sensitize has been investigated.
Methods Ara h 1 was purified from whole roasted peanuts. Intact Ara h 1 was digested in an in vitro model, simulating the human gastrointestinal digestion process. Digestion products were analysed for peptide sizes and their ability to aggregate. Brown Norway (BN) rats, used as an animal model, were immunized with purified intact Ara h 1 or the gastrointestinal digestion products thereof. The sensitizing capacity was evaluated by analyses of specific antibody (IgG1, IgG2a and IgE) responses and ability to trigger mediator release of rat basophilic leukaemia (RBL)-2H3 cells.
Results The present study showed that Ara h 1 was broken down, resulting in peptide fragments of sizes <2.0 kDa, of which approximately 50% was in aggregated complexes of M _r up to 20 kDa. Ara h 1 digesta were shown to have sensitizing capacity in BN rats, being capable of inducing specific IgG and IgE antibodies. The IgE response was functional, having the capacity to induce specific degranulation of RBL cells.
Conclusion From this study, it can be concluded that lability of a food allergen to gastrointestinal digestion does not necessarily abrogate its allergenic sensitizing potential.     

Crystal structure determination and analysis of 11S coconut allergen: Cocosin

Allergy is an abnormal immune response against an innocuous target. Food allergy is an adverse reaction caused by common foods most well-known being those involving peanuts. Apart from mono sensitized food allergy, cross-reactivity with other food allergens is also commonly observed. To understand the phenomenon of cross-reactivity related to immune response, three dimensional structures of the allergens and their antigenic epitopes has to be analysed in detail. The X-ray crystal structure of Cocosin, a common 11S food allergen from coconut, has been determined at 2.2 Å resolution using molecular replacement technique. The monomer of 52 kDa is composed of two β-jelly roll domains, one with acidic and the other with basic character. The structure shows hexameric association with two trimers facing each other. Though the overall structure of Cocosin is similar to other 11S allergens, the occurrence of experimentally determined epitopes of the peanut allergen Ara h 3 at flexible as well as variable regions could be the reason for the clinically reported result of cross-reactivity that the peanut allergic patients are not sensitized with coconut allergen.     

Development of a rapid dipstick immunoassay for the detection of peanut contamination of food

Polyclonal antisera were raised to conarachin, the 7S globulin of peanut, Arachis hypogea. The antisera were of high titre and were specific for conarachin, showing no significant cross‐reaction with proteins from a range of nuts and legumes, as determined by immunoblotting and ELISA. A dipstick ELISA was developed using these antisera as both the capture and detector elements of the assay. The final steps utilized an avidin‐biotin detection system and tetramethylbenzidine as the substrate. The dipstick assay was highly sensitive, and employed a simple one‐step extraction method. It was able to detect as little as 0.01% (w/w) of peanut in marzipan and 0.1% (w/w) of peanut in chocolate. Roasted nuts were also detected, down to a concentration of 0.1% (w/w) in both foods. The dipstick assay also functioned with a range of foodstuffs, and readily indicated any that contained peanut. This method enables analysts to test, for the first time, for the presence of peanuts in food in a fast and easy‐to‐use manner. The availability of such technology makes the task of monitoring foods for contamination by peanuts readily achievable, providing the industry with an important tool for quality control of raw materials, processes and products. Increased testing will give consumers, particularly those sensitive to this potent allergen, increased assurance as to the safety of the food they eat.     

Carob is not allergenic in peanut-allergic subjects

BACKGROUND: The antigenic potential of proteins from the carob bean, a member of the legume family used as a food additive, have not so far been investigated and legumes share antigenic proteins with peanut, a potent trigger of anaphylaxis. OBJECTIVE: To assess the carob protein determinants of sensitization in peanut-allergic children. METHODS: In a prospective, double-blind, placebo-controlled study 12 patients (median age 9.5 years) with a history of hyperreactivity to peanut (anaphylaxis) were assessed. Skin prick tests with a commercial peanut allergen, raw carob pulp, raw and cooked carob cotyledon formula were used to confirm the history. RAST for peanuts and cooked carob were used to evaluate sensitization to these proteins. Carob-specific IgE were identified by immunoblotting analyses. Allergic reactivity was evaluated during double-blind placebo-controlled food challenges (DBPCFC; 5.5 g carob extract and cooked carob cotyledon formula). RESULTS: Peanut allergen-induced skin prick test positivity in all children (confirmed during double-blinded challenge in 6/12 patients), carob pulp in 3/12 patients, raw carob bean in 6/12, and cooked carob cotyledon formula in none. RAST were positive for peanut in all cases but negative for carob beans in 9/12 cases. Immunoblot analyses found peanut-specific IgE in all cases and raw carob bean-specific IgE in eight cases. Carob allergens were identified in the 17.5, 48, and 66 kDa MW bands. The least allergenic density was found for cooked carob proteins. There was no clinical reactivity with either raw or cooked carob during DBPCFC. CONCLUSIONS: These data suggest that carob-specific sensitization, apparent both in vitro and in SPTs, can be concordant with peanut allergy and that cooked carob can be ingested by children who are allergic to peanuts. That heat-processing deactivates carob protein allergenicity has dietary implications for polyallergic children.     

Specific IgE antibodies to peanut in western Sweden – hasthe occurrence of peanut allergy increased without anincrease in consumption?

BACKGROUND: Sensitization to peanut has seldom been investigated in Sweden. Therefore, all IgE-specific tests for peanut during a 5-year period were reviewed to study the relation between the levels of specific IgE antibody to peanut and age, sex, symptoms, and other atopic manifestations. METHODS: All serum samples were analyzed for IgE antibodies to peanut in relation to sex, age, clinical reactions, and other food allergens. A subgroup was asked to answer a questionnaire about symptoms and atopic manifestations in relation to IgE antibody levels. RESULTS: During the study period, 2417 tests were made for peanut. There was an increased prevalence of detectable IgE antibodies during the years studied. More than 80 individuals under 2 years of age were sensitized to peanut. In the subgroup, individuals with detectable IgE antibodies reported a shorter reaction time after eating peanuts than individuals with normal IgE antibody levels (P < 0.05). CONCLUSION: The reaction pattern to peanuts in Sweden is similar to that in many other countries despite a reported steady and low consumption. The severity of symptoms was connected to age and IgE antibody level. Patients with normal or low IgE antibody levels were not always free of symptoms even though their risk of allergic symptoms was reduced.     

Basophil activation tests for the diagnosis of food allergy in children

Background Positive skin prick tests (SPT) for food allergens and specific IgE (sIgE) in serum indicate sensitization but do not enable distinction between sensitized but tolerant and clinically allergic patients.
Objective Herein, we evaluate the clinical relevance of basophil activation tests (BATs) for peanut or egg allergy diagnosis.
Methods Thirty-two peanut-allergic, 14 peanut-sensitized (sIgE⁺ and/or SPT⁺ to peanuts) but tolerant children and 29 controls with no history of an adverse reaction to peanuts were included. Similarly, 31 egg-allergic, 14 egg-sensitized children (sIgE⁺ and/or SPT⁺ to egg white) and 22 controls were studied. Flow cytometric analysis of CD63 expression or CD203c upregulation on basophils and the production of leukotrienes (LT) were performed in response to an in vitro crude peanut extract or ovalbumin (OVA) challenge.
Results After in vitro peanut challenge, the basophils from peanut-allergic children showed significantly higher levels of activation than those from controls ( P <0.001). After OVA challenge, a similar distinction ( P <0.001) was observed between egg-allergics and controls. Interestingly, the majority of egg- or peanut-sensitized children failed to activate basophils, respectively, in response to OVA and peanut challenge. The sensitivity of the CD63, CD203c and LT assay was 86.7%, 89.5% and 76.0% with a specificity of 94.1%, 97.1% and 94.6% for peanut allergy diagnosis. The corresponding performances of BATs applied to egg allergy diagnosis were 88.9%, 62.5% and 77.8% for the sensitivity and 100%, 96.4% and 96.4% for the specificity.
Conclusion Neither conventional tests nor BATs are sensitive and specific enough to predict food allergy accurately. However, BATs may helpfully complete conventional tests, especially SPT, allowing improved discrimination between allergic and non-allergic individuals.     

The ability of adults and children to visually identify peanuts and tree nuts

BackgroundPeanuts and tree nuts are common food allergens and are the leading cause of fatalities from food-induced anaphylaxis. Dietary avoidance is the primary management of these allergies and requires the ability to identify peanuts or tree nuts.ObjectivesTo investigate the ability of adults and children to visually identify peanuts and tree nuts.MethodsA nut display was assembled that held peanuts and 9 tree nuts in a total of 19 different forms. Persons 6 years or older completed a worksheet to name the items.ResultsOne-thousand one-hundred five subjects completed the study. The mean number of peanuts and tree nuts identified by all subjects was 8.4 (44.2%) out of a possible 19. The mean for children ages 6 to 18 was 4.6 (24.2%), compared with 11.1 (58.4%) for adults older than 18 (P < .001). The most commonly identified items were peanut in the shell and without the shell. The least identified was hazelnut (filbert) in the shell and without the shell. No difference was seen in the performance of peanut- or tree nut–allergic subjects compared with nonallergic subjects. Fifty percent of subjects with a peanut or tree nut allergy correctly identified all forms of peanuts or tree nuts to which they are allergic. Parents of peanut- or tree nut–allergic children did no better than parents of children without such allergy.ConclusionsOverall, both children and adults are unreliable at visually identifying most nuts. Treatment of nut allergies with dietary avoidance should include education for both adults and children on identification of peanuts and tree nuts.     

Allergenicity of various peanut products as determined by RAST inhibition

Extracts of 19 different peanut products and peanut oil were tested for their allergenicity by the radioallergosorbent test inhibition assay using a crude peanut extract from raw peanuts as the standard for comparison. Seventeen of the extracts were able to competitively inhibit the binding of serum IgE from peanut-sensitive patients with the solid-phase raw peanut extract. Peanut oil and the extract from hydrolyzed peanut protein did not inhibit binding, which suggests that these products are not allergenic. The peanut hull flour extract showed a slight ability to inhibit binding, suggesting that this product contains minor amounts of the peanut allergen.     

Quantification of Ara h 1 in peanuts: why roasting makes a difference

BACKGROUND: Increased allergenicity of roasted vs. raw peanut has been reported by showing higher IgE binding to roasted peanut extracts. OBJECTIVE: To study the effect of roasting on Ara h 1 quantification in peanut using a specific monoclonal antibody-based ELISA, and to compare the Ara h 1 content from different kernel size peanuts from four runner cultivars. METHODS: Raw or oven-roasted (177 degrees C for 5-30 min) runner peanuts were crushed and extracted at 60 degrees C. Inhibition ELISA was used to study binding of Ara h 1 purified from raw or roasted peanut. Runner peanuts of four different cultivars were collected, shelled, sized and roasted for 15 min at 177 degrees C. Ara h 1 in the extracts was compared by ELISA. RESULTS: Ara h 1 levels were up to 22-fold higher in roasted than in raw peanuts (820 vs. 37 microg/mL, in a representative experiment) with an Ara h 1 peak at 10-15 min of roasting. Inhibition ELISA indicated that this increase was not due to conformational changes in the Ara h 1 monoclonal antibody epitopes. Ara h 1 was found at lower levels in number 1 than in jumbo- and medium-sized peanuts, and no differences were found among cultivars. CONCLUSION: These results suggest that roasting increases the efficiency of Ara h 1 extraction, and/or that the monoclonal antibody binding epitopes were more accessible in roasted peanut. Expression of Ara h 1 is associated with peanut maturity.     

Self-reported allergic reactions to peanut on commercial airliners.

BACKGROUND: Allergic reactions to food occurring on commercial airlines have not been systematically characterized. OBJECTIVE: We sought to describe the clinical characteristics of allergic reactions to peanuts on airplanes. METHODS: Participants in the National Registry of Peanut and Tree Nut Allergy who indicated an allergic reaction while on a commercial airliner were interviewed by telephone. RESULTS: Sixty-two of 3704 National Registry of Peanut and Tree Nut Allergy participants indicated a reaction on an airplane; 42 of 48 patients or parental surrogates contacted confirmed the reaction began on the airplane (median age of affected subject, 2 years; range, 6 months to 50 years). Of these, 35 reacted to peanuts (4 were uncertain of exposure) and 7 to tree nuts, although 3 of these 7 reacted to substances that may have also contained peanut. Exposures occurred by ingestion (20 subjects), skin contact (8 subjects), and inhalation (14 subjects). Reactions generally occurred within 10 minutes of exposure (32 of 42 subjects), and reaction severity correlated with exposure route (ingestion > inhalation > skin). The causal food was generally served by the airline (37 of 42 subjects). Medications were given in flight to 19 patients (epinephrine to 5) and to an additional 14 at landing/gate return (including epinephrine to 1 and intravenous medication to 2), totaling 79% treated. Flight crews were notified in 33% of reactions. During inhalation reactions as a result of peanut allergy, greater than 25 passengers were estimated to be eating peanuts at the time of the reaction. Initial symptoms generally involved the upper airway, with progression to the skin or further lower respiratory reactions (no gastrointestinal symptoms). CONCLUSIONS: Allergic reactions to peanuts and tree nuts caused by accidental ingestion, skin contact, or inhalation occur during commercial flights, but airline personnel are usually not notified. Reactions can be severe, requiring medications, including epinephrine.     

The allure and peril of hematopoietic stem cell transplantation: overcoming immune challenges to improve success

Food allergy has become a major public health concern in westernized countries, and allergic reactions to peanuts are particularly common and severe. Allergens are defined as antigens that elicit an IgE response, and most allergenic materials (e.g., pollens, danders, and foods) contain multiple allergenic proteins. This has led to the concept that there are “major” allergens and allergens of less importance. “Major allergens” have been defined as allergens that bind a large amount of IgE from the majority of patients and have biologic activity. However, the ability of an allergen to cross-link complexes of IgE and its high-affinity receptor FcεRI (IgE/FcεRI), which we have termed its allergic effector activity, does not correlate well with assays of IgE binding. To identify the proteins that are the most active allergens in peanuts, we and others have employed in vitro model assays of allergen-mediated cross-linking of IgE/FcεRI complexes and have demonstrated that the most potent allergens are not necessarily those that bind the most IgE. The importance of a specific allergen can be determined by measuring the allergic effector activity of that allergen following purification under non-denaturing conditions and by specifically removing the allergen from a complex allergenic extract either by chromatography or by specific immunodepletion. In our studies of peanut allergens, our laboratory has found that two related allergens, Ara h 2 and Ara h 6, together account for the majority of the effector activity in a crude peanut extract. Furthermore, murine studies demonstrated that Ara h 2 and Ara h 6 are not only the major elicitors of anaphylaxis in this system, but also can effectively desensitize peanut-allergic mice. As a result of these observations, we propose that the definition of a major allergen should be based on the potency of that allergen in assays of allergic effector activity and demonstration that removal of that allergen from an extract results in loss of potency. Using these criteria, Ara h 2 and Ara h 6 are the major peanut allergens.     

The 18 kDa peanut oleosin is a candidate allergen for IgE-mediated reactions to peanuts

Background : Peanut allergy is one of the five most frequent food allergies in children and in adults. Recently, we purified and evaluated the allergenicity of peanut oleosins, a family of small-sized proteins involved in the formation of peanut oil bodies.
Methods:  Allergenicity of the purified native protein and of the recombinant protein was tested by Western blot and by IgE-RIA.
Results:  We found IgE-binding with oleosin in 3 of 14 sera of patients who had suffered an allergic reaction to peanuts. Two sera reacted weakly against 16–18 kDa proteins corresponding to oleosin monomers, in Western blot. The main reacting bands had a molecular size estimated at ≈34 kDa, ≈50 kDa and ≈ 68 kDa and could therefore correspond to oleosin oligomers. IgE reactivity was higher in extracts from roasted peanuts. The same phenomenon occurred with crude soybean oil fraction, with two bands of 16.5 and 24 kDa corresponding to monomers, and two bands of 50 kDa and 76 kDa corresponding to dimers and trimers, respectively. The 18 kDa band was observed in the 3 Western blots of a membrane-enriched fraction of recombinant oleosin produced in the Sf 9-baculovirus expression system (performed with the 3 patient sera).
Conclusions:  We have characterized a new peanut allergen which belongs to the oleosins, a family of proteins involved in the formation of oil bodies. The protein may be involved in some of the allergic cross-reactions to peanuts and soybeans.     

The effect of cooking methods on the allergenicity of peanut

It has been rarely studied why the prevalence of peanut allergy is relative low in China. The aim of this study was to investigate: (i) the major peanut allergens in China, (ii) the effect of buffer composition on peanut allergens extraction efficiency, and (iii) the effect of cooking methods on peanut allergenicity. The allergenic property of peanut protein extracts was assessed by immunoblotting. The relative contents of the major peanut allergens were quantified by densitometry. The ability of IgE to bind to the different peanut preparations (fried, boiled and roasted) was detected with ELISA. In conclusion, Ara h 1 and several proteins belonging to the Ara h 3 were major peanut allergens. Different buffers lead to different extraction efficiency for allergen fragments. The IgE binding property of peanuts processed by cooking, frying and roasting did not differ significantly. Therefore, cooking methods may not explain the reason for the lower prevalence of peanut allergy in China.