Clinical update on peanut allergy

What Is Anaphylaxis? Pediatric Residents' Perception and Treatment of Anaphylactic Reactions

To assess knowledge regarding symptoms and treatment of anaphylaxis, a vignette of a child having an allergic reaction to a peanut was presented to residents in an allergy clinic. Twelve sets of clinical outcomes ranging from severe multi-organ to mild single organ involvement were described, and residents were asked if each symptom set met criteria for diagnosis of anaphylaxis, whether epinephrine should be administered acutely and prescribed at follow-up, and whether peanuts should be avoided in the future. Of cases that met the definition of anaphylaxis 28.8% were incorrectly diagnosed, in 13.6% of cases they would allow peanuts to be eaten again, and in 23.9% of cases they would not prescribe epinephrine at follow-up. In 26.1% of cases meeting criteria for acute anaphylaxis residents would not administer epinephrine. Deficits regarding the diagnosis and treatment of anaphylaxis by residents were identified, and increased educational efforts are needed.

Loss of IL-4Rα-mediated PI3K signaling accelerates the progression of IgE/mast cell-mediated reactions

Clinical and experimental evidence indicate that polymorphisms within the interleukin 4 (IL‐4) receptor (IL‐4R) chain are sufficient for altered strength of IL‐4/IL‐13 signaling, leading to an exaggerated allergic inflammatory response and increase susceptibility to allergic phenotypes. In the present study, we show that ablation of IL‐4Rα–induced phosphatidylinositol 3‐kinase (PI3K) activating signal by germline point mutation within the IL‐4Rα motif (Y500F) did not alter susceptibility to IgE‐mediated, food‐induced experimental anaphylaxis. Moreover, diarrhea occurrence, antigen‐specific IgE and intestinal mastocytosis were comparable between WT and IL‐4Rα^Y500F mice. However, mice unable to stimulate IL‐4Rα–mediated PI3K signaling had accelerated disease progression. Notably, the accelerated anaphylactic response was associated with more rapid histamine‐induced hypovolemia. Mechanistic in vitro and in vivo analyses revealed that endothelial IL‐4Rα PI3K signaling negatively regulates the histamine‐induced endothelial leak response. These results define an unanticipated role for IL‐4Rα–mediated PI3K signaling in negative regulation of IgE‐mediated anaphylactic reactions.

Molecular sIgE profile in infants and young children with peanut sensitization and eczema

Background:

Many children develop a sensitization to peanut in early infancy, even before peanut is introduced in their diet. Sensitization is particularly common in young children with eczema. There have been scant data available to date on the sensitization pattern for specific peanut allergens in this patient group. The aim of this study was to investigate the allergen profile of infants and young children with peanut sensitization and eczema.

Methods:

Sera from 53 children aged ≤ 20 months with eczema and sensitization to peanut but who had not yet consumed products containing peanuts were included in the analysis. Sera were analyzed using microarray immunoassay (ImmunoCAP ISAC).

Results:

In total, 63 % of peanut-sensitized children showed specific immunoglobulin E (sIgE) against at least one peanut allergen on the microarray. Specific IgE to the 7S globulin Ara h 1 was detected in 40 % of the children, to the 2S albumin Ara h 2 in 30 % and to the 11S globulin Ara h 3 in 23 %. Only one child had sIgE to Arah 8, the homologoue of Bet-v-1. Data on clinical relevance were available for 24 of 53 children: 14 of 24 patients had objective allergic reactions to peanut, while 10 children were peanut-tolerant. The seed storage protein Ara h 2 was not detected on microarray in 43 % (6 of 14) of children with peanut allergy. Two of these six children were mono-sensitized to Ara h 1 and two to Ara h 3, while in three children none of these seed storage proteins was detected.

Discussion:

It could be shown that infants and young children with eczema and sensitization to peanut recognize predominantly seed storage proteins from peanut, even before the introduction of peanut into their diet. Sensitization to pollen-related food allergens seems to be rare at this age. At this age not only Ara h 2, but also Ara h 1 seems to be related to clinical relevance.

Food hypersensitivity in patients over 14 years of age suffering from atopic dermatitis

BACKGROUND

Patients suffering from atopic dermatitis often describe food hypersensitivity. Rising prevalence of food hypersensitivity and severe allergic reactions to foods have been reported, but the data are scarce.

AIMS AND OBJECTIVES

Evaluation of food hypersensitivity reactions in patients suffering from atopic dermatitis.

MATERIALS AND METHODS

The dermatological examination was performed in patients of age 14 years and above and the detailed history was taken concerning the food hypersensitivity.

RESULTS

A total of 228 patients were examined-72 men, 156 women, average age 26.2 (SD 9.5) years. The food hypersensitivity reactions were recorded in 196 patients from 228 (86%), no reactions were recorded in 32 patients (24%). Foods with the most often recorded reactions are: Nuts (in 35% of patients), tomatoes (in 20%), and kiwi (in 17, 5%), apples and spices (in 16%), tangerines and oranges (in 15%), capsicum (in 13%), fishes (in 12%), celery (in 9%), and chocolate (in 7%).

CONCLUSION

Food hypersensitivity reactions are recorded in 86% of patients suffering from atopic dermatitis. Nuts, tomatoes, and pollen-associated foods play a role in the majority of patients suffering from atopic dermatitis.

Advances in diagnosing peanut allergy

Peanut allergy is often severe, potentially fatal, usually persistent, and appears to have increased in prevalence. An accurate diagnosis is essential because there is a significant burden on quality of life. The tools available for diagnosis include the medical history, skin prick test (SPT), determination of serum peanut-specific IgE antibodies (PN-IgE), and medically supervised oral food challenges. Numerous studies, almost exclusively in children, have correlated clinical outcomes against SPTs and PN-IgE with informative results. The diagnostic utility of SPT and PN-IgE is maximized by considering the degree of positive result and consideration of the medical history (a priori estimation of risk). Emerging tests that evaluate IgE binding to specific proteins in peanut (component testing) add important additional diagnostic information in specific settings. Studies are increasingly focused on how the results of tests considered in combination (or performed serially) may increase diagnostic accuracy. Here, we review the utility of currently available tests and provide suggestions on how to best use them to accurately predict peanut allergy. Still, the physician-supervised oral food challenge remains the most definitive test available.

Impact of thermal processing on legume allergens

Food induced allergic manifestations are reported from several parts of the world. Food proteins exert their allergenic potential by absorption through the gastrointestinal tract and can even induce life threatening anaphylaxis reactions. Among all food allergens, legume allergens play an important role in induction of allergy because legumes are a major source of protein for vegetarians. Most of the legumes are cooked either by boiling, roasting or frying before consumption, which can be considered a form of thermal treatment. Thermal processing may also include autoclaving, microwave heating, blanching, pasteurization, canning, or steaming. Thermal processing of legumes may reduce, eliminate or enhance the allergenic potential of a respective legume. In most of the cases, minimization of allergenic potential on thermal treatment has generally been reported. Thus, thermal processing can be considered an important tool by indirectly prevent allergenicity in susceptible individuals, thereby reducing treatment costs and reducing industry/office/school absence in case of working population/school going children. The present review attempts to explore various possibilities of reducing or eliminating allergenicity of leguminous food using different methods of thermal processing. Further, this review summarizes different methods of food processing, major legumes and their predominant allergenic proteins, thermal treatment and its relation with antigenicity, effect of thermal processing on legume allergens; also suggests a path that may be taken for future research to reduce the allergenicity using conventional/nonconventional methods.

Oral immunotherapy for the treatment of peanut allergy: systematic review of six case series studies

BACKGROUND

Allergy to peanuts is associated with considerable morbidity and, in a minority of cases, mortality. Natural resolution to peanut allergy occurs in only a few cases, hence the need to find effective interventions. Peanut oral immunotherapy (OIT) is a potentially important new therapeutic development.

AIMS

To assess the benefits and harms of OIT for peanut allergy.

METHODS

Fourteen databases were searched for published reports and unpublished/in-progress studies. We included studies employing randomised controlled trial (RCT), quasi-RCT, controlled clinical trial, controlled before-and-after, interrupted time series, and case series designs.

RESULTS

Six studies enrolling a total of 85 participants satisfied our inclusion criteria. All studies employed a case series design and were thus judged to be at high risk of bias. Overall, this body of evidence provided suggestive evidence that it is possible for many participants to increase their threshold dose for peanut exposure whilst receiving treatment. Adverse reactions were common and, whilst most of these were relatively minor, some were potentially life-threatening.

CONCLUSIONS

OIT appears to be a potentially promising new therapy for the short- to medium-term management of carefully selected and monitored patients with peanut allergy. The effectiveness and cost-effectiveness of OIT - particularly over the longer term - need to be clearly established using more robust designs before its clinical use can be contemplated. Given the risk of triggering serious adverse reactions, OIT should not be administered outside clinical trial settings.

Genetics of food allergy

PURPOSE OF REVIEW

Food allergy, a growing clinical and public health problem in the United States and worldwide, is likely determined by multiple environmental and genetic factors. The purpose of this review is to summarize recent advances in food allergy genetic research.

RECENT FINDINGS

There is compelling evidence that genetic factors may play a role in food allergy. However, the specific genetic loci that may modulate individual risk of food allergy remain to be identified. To date, only a limited number of candidate gene association studies of food allergy have been reported. Polymorphism(s) in nine genes have been associated with the incidence of food allergy or food allergy severity in at least one study. But most of these findings remain to be replicated in independent populations. In contrast, there are considerable advances in genetics of other allergic diseases such as asthma and atopic dermatitis. Although asthma and atopic dermatitis often coexist with food allergy, the relevance of their candidate genes to food allergy remains to be evaluated.

SUMMARY

Genetics in food allergy is a promising research area but is still in its infancy. More studies are needed to dissect susceptible genes of food allergy. A genome-wide association approach may serve as a powerful tool to identify novel genes related to food allergy. Furthermore, the role of gene-environment interaction, gene-gene interaction, and epigenetics in food allergy remains largely unexplored. Given the complex nature of food allergy, future studies need to integrate environment, genomics, and epigenomics in order to better understand the multifaceted etiology and biological mechanisms of food allergy.

Association analysis of food allergens

Food allergy patients are known to present with allergic reactions to multiple allergens, but extrapolating these associations is difficult. Data mining, a procedure that analyzes characteristic combinations among large amounts of information, is often used to analyze and predict consumer purchasing behaviour. We applied this technique to the extrapolation of food allergen associations in allergy patients. We sent 1510 families our 'Questionnaire survey for the prevention of food allergies'. Responses noting 6549 allergens came from 878 families with 1383 patients, including 402 with anaphylaxis. Some results of the survey have already been published and here we presented the results of our association analysis of combinations of food allergens. Egg, milk, wheat, peanuts, and buckwheat are the most common food allergens. The most common simultaneous combinations of these allergens were 'egg-milk', 'egg-wheat', and 'milk-wheat'. The occurrence probability of a combination (i.e. one person suffering from a certain allergen also suffers from another) is called 'confidence'. Confidence was higher for 'chicken-egg', 'abalone-salmon eggs', and 'matsutake mushroom-milk'. As well, the combinations of 'crab-shrimp', 'squid-shrimp', and 'squid-crab' also indicated higher values in a statistical examination of the occurrence probabilities of these allergen combinations (Z-score). From the results of the association analysis, we speculated that some food allergens, such as abalone, orange, salmon, chicken, pork, matsutake mushroom, peach and apple did not independently induce food allergies. We also found that combinations, such as 'crab-shrimp', 'squid-shrimp', 'squid-crab', 'chicken-beef', and 'salmon-mackerel' had strong associations.

Anaphylactic reactions on the beach: a cause for concern?

BACKGROUND

The commonest causes of anaphylaxis include hymenoptera bites, high-risk food, exercise, and jellyfish bites and may often be encountered on the beach. Therefore, millions of visitors at popular touristic locations are exposed to increased risk of anaphylactic reactions every year. At least 35 cases of acute allergic reactions requiring medical attention took place on the beaches of Crete, Greece during the previous summer.

OBJECTIVE

To evaluate the level of training of lifeguards working on the beaches of the island of Crete, Greece, with regard to emergency management of anaphylaxis as well as to assess the sufficiency of medical equipment that lifeguards possess to treat an anaphylactic reaction.

METHODS

A questionnaire was prepared by the authors and administered to 50 lifeguards working on various beaches of Crete. Queries included the definition of anaphylaxis, proper medical treatment, and the existence or not and composition of an emergency kit with regard to the management of acute allergic reactions.

RESULTS

Our series consisted of 50 lifeguards, 39 (78%) male and 11 female (22%). Although 41 (80%) lifeguards were aware of an acceptable definition of anaphylaxis, no one knew that epinephrine is the first-choice treatment, and 32 (60%) lifeguards replied that steroids should be used for emergency treatment. Additionally, no one possessed an emergency kit that would qualify for management of acute allergic reactions.

CONCLUSIONS

The beach should be considered as a high-risk place for the appearance of anaphylactic reactions. Lifeguards who would be the first trained personnel to encounter this condition should be sufficiently trained and equipped for emergency treatment. Our department is currently introducing a training program to local authorities for the proper training and equipping of lifeguards in the island of Crete.

Purification, crystallization and preliminary X-ray characterization of prunin-1, a major component of the almond (Prunus dulcis) allergen amandin

The 11S globulins from plant seeds account for a number of major food allergens. Because of the interest in the structural basis underlying the allergenicity of food allergens, we sought to crystallize the main 11S seed storage protein from almond ( Prunus dulcis). Prunin-1 (Pru1) was purified from defatted almond flour by water extraction, cryoprecipitation, followed by sequential anion exchange, hydrophobic interaction, and size exclusion chromatography. Single crystals of Pru1 were obtained in a screening with a crystal screen kit, using the hanging-drop vapor diffusion method. Diffraction quality crystals were grown after optimization. The Pru1 crystals diffracted to at least 3.0 A and belong to the tetragonal space group P4(1)22, with unit cell parameters of a = b = 150.912 A, c = 165.248 A. Self-rotation functions and molecular replacement calculations showed that there are three molecules in the asymmetry unit with water content of 51.41%. The three Pru1 protomers are related by a noncrystallographic 3-fold axis and they form a doughnut-shaped trimer. Two prunin trimers form a homohexamer. Elucidation of prunin structure will allow further characterization of the allergenic features of the 11S protein allergens at the molecular level.

A EuroPrevall review of factors affecting incidence of peanut allergy: priorities for research and policy

Peanuts are extensively cultivated around the world, providing a foodstuff that is both cheap to produce and nutritious. However, allergy to peanuts is of growing global concern, particularly given the severity of peanut-allergic reactions, which can include anaphylaxis and death. Consequently, it is important to understand the factors related to the prevalence of peanut allergy in order to inform efforts to ameliorate or pre-empt the condition. In this article we review evidence for the relevance of factors hypothesized to have some association with allergy prevalence, including both genetic and environmental factors. Although our analysis does indicate some empirical support for the importance of a number of factors, the key finding is that there are significant data gaps in the literature that undermine our ability to provide firm conclusions. We highlight these gaps, indicating questions that need to be addressed by future research.

A survey of patients with self-reported severe food allergies in Japan

Food allergies have increased in recent years in Japan. Details of causative foods, places where anaphylaxis developed, and other allergic factors remain unknown, and we investigated them. A'questionnaire survey for the prevention of food allergies' was conducted using a nationwide group of patients with food allergies. A total of 1383 patients from 878 families (including 319 patients who experienced anaphylaxis) provided valid answers to the questionnaire. The average age of the first anaphylactic attack was 3.20 +/- 6.327 yr. The most common allergens causing anaphylaxis were in order milk, eggs, wheat, peanuts, and soybeans, followed by sesame and buckwheat. The most common place where anaphylaxis developed was the patient's own home, followed by fast food restaurants, places visited, restaurants, and schools. In patients' own homes, fast food restaurants (buffet), places visited and schools, the most common allergens were milk, eggs, and wheat. In restaurants and accommodation facilities, eggs were the most common allergen followed by milk. As possible food allergies can cause anaphylaxis, it is necessary to provide precise information for consumers regarding packaged and processed foods.

Purification, crystallization and initial crystallographic characterization of brazil-nut allergen Ber e 2

Peanut and tree-nut allergies have attracted considerable attention because of their frequency and their lifelong persistence. Brazil-nut (Bertholletia excelsa) allergies have been well documented and the 11S legumin-like seed storage protein Ber e 2 (excelsin) is one of the two known brazil-nut allergens. In this study, Ber e 2 was extracted from brazil-nut kernels and purified to high purity by crystalline precipitation and gel-filtration chromatography. Well diffracting single crystals were obtained using the hanging-drop vapour-diffusion method. A molecular-replacement structural solution has been obtained. Refinement of the structure is currently under way.

Peanut allergy: Emerging concepts and approaches for an apparent epidemic

Peanut allergy is typically lifelong, often severe, and potentially fatal. Because reactions can occur from small amounts, the allergy presents patients with significant obstacles to avoid allergic reactions. In North America and the United Kingdom, prevalence rates among schoolchildren are now in excess of 1%, framing an increasing public health concern and raising research questions about environmental, immunologic, and genetic factors that may influence outcomes of peanut allergy. This review focuses on recent observations that continue to question the influences of maternal and infant diet on outcomes of peanut allergy, and explore how peanut may be uniquely suited to induce an allergic response. We highlight studies that affect current diagnosis, management, and the nature of advice that can be provided to patients, including the utility of diagnostic tests, doses that elicit reactions, characteristics of reactions from exposure, issues of cross-reactivity, concerns about peanut contamination of manufactured goods, and the natural course of the allergy. Clinical, molecular, and immunologic advances are reviewed, highlighting research discoveries that influence strategies for improved diagnosis, prevention, and treatment. Among the therapeutic strategies reviewed are sublingual and oral immunotherapy, anti-IgE, Chinese herbal medicine, and vaccine strategies.

Food allergy: nuts and tree nuts

Nuts are a well-defined cause of food allergy, which affect approximately 1 % of the general population in the UK and the USA. There do appear to be differences in the frequency of nut allergy between different countries because of different dietary habits and cooking procedures. For example, in the USA and France, peanuts are one of the most frequent causes of food allergy, but in other countries, it seems to be less common. Genetic factors, in particular, appear to play a role in the development of peanut allergy. While the majority of nut allergens are seed storage proteins, other nut allergens are profilins and pathogenesis-related protein homologues, considered as panallergens because of their widespread distribution in plants. The presence of specific IgE antibodies to several nuts is a common clinical finding, but the clinical relevance of this cross-reactivity is usually limited. Allergic reactions to nuts appear to be particularly severe, sometimes even life-threatening, and fatal reactions following their ingestion have been documented. Food allergy is diagnosed by identifying an underlying immunological mechanism (i.e. allergic testing), and establishing a causal relationship between food ingestion and symptoms (i.e. oral challenges). In natural history investigations carried out in peanut-allergic children, approximately 20 % of the cases outgrew their allergy or developed oral tolerance. The treatment of nut allergies should include patient and family education about avoiding all presentations of the food and the potential for a severe reaction caused by accidental ingestion. Patients and families should be instructed how to recognise early symptoms of an allergic reaction and how to treat severe anaphylaxis promptly.

Food allergy and the introduction of solid foods to infants: a consensus document. Adverse Reactions to Foods Committee, American College of Allergy, Asthma and Immunology

OBJECTIVE

To make recommendations based on a critical review of the evidence for the timing of the introduction of solid foods and its possible role in the development of food allergy.

DATA SOURCES

MEDLINE searches using the following search algorithm: [weaning AND infant AND allergy]/[food allergy AND sensitization]/[dietary prevention AND food allergy OR allergens]/[Jan 1980-Feb 2006].

STUDY SELECTION

Using the authors' clinical experience and research expertise, 52 studies were retrieved that satisfied the following conditions: English language, journal impact factor above 1 or scientific society, expert, or institutional publication, and appraisable using the World Health Organization categories of evidence.

RESULTS

Available information suggests that early introduction can increase the risk of food allergy, that avoidance of solids can prevent the development of specific food allergies, that some foods are more allergenic than others, and that some food allergies are more persistent than others.

CONCLUSIONS

Pediatricians and allergists should cautiously individualize the introduction of solids into the infants' diet. With assessed risk of allergy, the optimal age for the introduction of selected supplemental foods should be 6 months, dairy products 12 months, hen's egg 24 months, and peanut, tree nuts, fish, and seafood at least 36 months. For all infants, complementary feeding can be introduced from the sixth month, and egg, peanut, tree nuts, fish, and seafood introduction require caution. Foods should be introduced one at a time in small amounts. Mixed foods containing various food allergens should not be given unless tolerance to every ingredient has been assessed.

Genetics of food allergy

Allergic reactions to foods are an important medical problem throughout the industrialized world. The occurrence of food allergy appears to be strongly influenced by genetics, but the basis of the genetic predisposition to food allergy has not been differentiated from that for atopy in general. In addition, genetic susceptibility alone does not explain the prevalence of food allergy satisfactorily, leaving ample room to consider the importance of environmental influences (external, maternal, and gastrointestinal environment) and interactions between the host and the environment. Several features of food allergy are highlighted in this review: 1) patients with severe food allergies are overwhelmingly atopic, but food allergy occurs only in approximately 10% of patients with other atopic diseases; 2) most patients are clinically reactive to a single food, and although a substantial minority have multiple food allergies, the variety of bone fide food allergies in a given individual is limited; 3) foods contain multiple proteins whereas only a small subset are allergenic; 4) there is likely an important contribution of the environment, becoming manifest in genetically susceptible individuals.

Development of a competitive liposome-based lateral flow assay for the rapid detection of the allergenic peanut protein Ara h1

A competitive lateral flow assay for detecting the major peanut allergen, Ara h1, has been developed. The detector reagents are Ara h1-tagged liposomes, and the capture reagents are anti-Ara h1 polyclonal antibodies. Two types of rabbit polyclonal antibodies were raised either against the entire Ara h1 molecules (anti-Ara h1 Ab) or against an immunodominant epitope on Ara h1 (anti-peptide Ab). All of them reacted specifically with Ara h1 in Western Blot against crude peanut proteins. Moreover, the anti-Ara h1 Ab was chosen for this assay development because of its highest immunoactivity to Ara h1-tagged liposomes in the lateral flow assay. The calculated limit of detection (LOD) of this assay is 0.45 microg mL(-1) of Ara h1 with a dynamic range between 0.1 and 10 microg mL(-1) of Ara h1 in buffer. Additionally, the visually determined detection range is from 1 to 10 microg mL(-1) of Ara h1 in buffer. Results using this assay can be obtained within 30 min without the need of sophisticated equipment or techniques; therefore, this lateral flow assay has the potential to be a cost-effective, fast, simple, and sensitive method for on-site screening of peanut allergens.

Influence of thermal processing on the allergenicity of peanut proteins

Peanuts are one of the most common and severe food allergens. Nevertheless, the occurrence of peanut allergy varies between countries and depends on both the exposure and the way peanuts are consumed. Processing is known to influence the allergenicity of peanut proteins. The aim of this study was to assess the effect of thermal processing on the IgE-binding capacity of whole peanut protein extracts and of the major peanut allergens Ara h 1 and Ara h 2. Whole proteins, Ara h 1, and Ara h 2 were extracted and purified from raw, roasted and boiled peanuts using selective precipitation and multiple chromatographic steps, and were then characterized by electrophoresis and mass spectrometry. The immunoreactivity of whole peanut extracts and purified proteins was analyzed by the enzyme allergosorbent test (EAST) and EAST inhibition using the sera of 37 peanut-allergic patients. The composition of the whole protein extracts was modified after heat processing, especially after boiling. The electrophoretic pattern showed protein bands of low molecular weight that were less marked in boiled than in raw and roasted peanuts. The same low-molecular-weight proteins were found in the cooking water of peanuts. Whole peanut protein extracts obtained after the different processes were all recognized by the IgE of the 37 patients. The IgE-binding capacity of the whole peanut protein extracts prepared from boiled peanuts was 2-fold lower than that of the extracts prepared from raw and roasted peanuts. No significant difference was observed between protein extracts from raw and roasted peanuts. It is noteworthy that the proteins present in the cooking water were also recognized by the IgE of peanut-allergic patients. IgE immunoreactivity of purified Ara h 1 and Ara h 2 prepared from roasted peanuts was higher than that of their counterparts prepared from raw and boiled peanuts. The IgE-binding capacity of purified Ara h 1 and Ara h 2 was altered by heat treatment and in particular was increased by roasting. However, no significant difference in IgE immunoreactivity was observed between whole protein extracts from raw and roasted peanuts. The decrease in allergenicity of boiled peanuts results mainly from a transfer of low-molecular-weight allergens into the water during cooking.

Genomic organization of peanut allergen gene, Ara h 3

Type 1 hypersensitivity to peanut proteins is a well-recognized health problem. Several peanut seed storage proteins have been identified as allergens. Ara h 3, a glycinin protein, is one of the important peanut allergens. Although amino acid and cDNA sequences are available for Ara h 3, there is not information at the genomic level. The objectives of this study were to isolate, sequence, and characterize the genomic clone of peanut allergen, Ara h 3. A peanut genomic library was screened, using two [32P] end-labeled oligonucleotide probes designed based on cDNA sequences of Ara h 3 and Ara h 4. Four positives lambda FIX II clones were obtained after four rounds of screenings. Digestion with Sac I resulted in two fragments of 1.5 and 10 kb hybridizing to the probes. Both fragments were subcloned into p-Bluescript vector and sequenced. The Ara h 3 gene spans 3.5 kb and consists of four exons, three introns, 5' and 3' flanking regions. The open reading frame is 2008 bp long and can encode a polypeptide of 538 amino acids residues. Sequences analogous to a TATA-box (TATAAAT), CAAT-box (AGGA), G-box (TCCTACGTGTCC) and several cis-elements were found in the promoter region. In the 3' downstream region, three polyadenylation signals (AATAAA) were identified.

Clinical tolerance of processed foods

OBJECTIVE

To review the effects of technological processing on selected foods of relevance to childhood allergy from the viewpoints of reduced allergenicity, contamination of processed foods by allergens introduced during processing, and ad hoc technologies to produce reduced hypoallergenic products.

DATA SOURCES

We searched the literature (PubMed/MEDLINE) for articles published between January 1994 and April 2004 using the following keywords: food allergy AND process* OR heat* OR cooking OR toleran*.

STUDY SELECTION

We drew on our collective clinical and biological experience to restrict retrieved studies to those of more frequent relevance to a hospital allergy practice.

RESULTS

Comparatively few clinical studies address the modification of allergenicity of food through cooking or processing. Dairy foods are largely unaffected by processing and may be contaminated by, or themselves become, hidden allergens. Hypoallergenic formulas based on milk, soy, or rice and homogenized beef are successful applications of allergenicity reduction via technological processing. Egg, fish, condiments, and vegetables all carry heat-resistant allergens and should also be considered contaminants. Cereals and bakery products are generally well tolerated, but their allergenicity may be enhanced by processing; the case of rice is still open. Peanut allergens are stable, and the evidence is scant that thermal processing affects the allergenicity of soybean and soy hydrolysates. The debate is ongoing about the tolerance of vegetable oils.

CONCLUSIONS

It is too early to systematize clinical studies based on single procedures. Processing affects antigenicity, but this does not always translate into safety recommendations. Industrial processing is liable to contamination, and monitoring and labeling are industry priorities. Clinicians should evaluate foods by as complete a workup as possible before recommending processed foods.

Ara h 8, a Bet v 1–homologous allergen from peanut, is a major allergen in patients with combined birch pollen and peanut allergy

BACKGROUND

We recently described patients with soybean allergy mainly mediated by cross-reactivity to birch pollen allergens. A majority of those patients were reported to have peanut allergy.

OBJECTIVE

We sought to study the occurrence of peanut allergy in patients allergic to birch pollen and characterized the Bet v 1-homologous peanut allergen Ara h 8.

METHODS

Recombinant Ara h 8 was cloned with degenerated primers and expressed in Escherichia coli. Nine Swiss and 11 Dutch patients with peanut and birch pollen allergy and a positive double-blind, placebo-controlled food challenge result to peanut were investigated for IgE reactivity to birch pollen and purified peanut allergens and cross-reactivity between birch and peanut. Ara h 8 stability against digestion and roasting was assessed by means of RAST inhibition. The IgE cross-linking potency of Ara h 8 was tested on the basis of basophil histamine release.

RESULTS

During double-blind, placebo-controlled food challenge, all patients experienced symptoms in the oral cavity, progressing to more severe symptoms in 40% of patients. CAP-FEIA detected recombinant (r) Ara h 8-specific IgE in 85%. IgE binding to Ara h 8 was inhibited by Bet v 1 in peanut extract immunoblotting and in RAST inhibition. In EAST inhibition recombinant rAra h 8 inhibited IgE binding to peanut in 4 of 7 tested patient sera. Antipeanut response was dominated by Ara h 8 in 12 of 17 tested patients. Furthermore, our results demonstrate a low stability of Ara h 8 to roasting and no stability to gastric digestion. Basophil histamine release with rAra h 8 was more than 20% in 5 of 7 tested sera.

CONCLUSIONS

Peanut allergy might be mediated in a subgroup of our patients by means of cross-reaction of Bet v 1 with the homologous peanut allergen Ara h 8.

Evaluation of an anaphylaxis training program for unlicensed assistive personnel

This study evaluated a training program designed to prepare unlicensed assistive personnel (UAP) in high school settings to recognize and respond effectively to an anaphylactic emergency. Subjects included 53 adults employed by a high school district in the San Francisco Bay Area of California. A training model was developed based on Bandura's theory of sources of self-efficacy. Knowledge and perceived self-efficacy of participants were measured before and after the training program to determine if a theory-based anaphylaxis recognition and epinephrine auto-injector training program would increase participants' knowledge and self-efficacy in responding to an anaphylactic emergency. Paired t tests revealed significant improvement in scores for both knowledge and perceived self-efficacy following the intervention (p < .001). This theory-based training program offers a valuable model for other school nurses in providing knowledge and skill training for unlicensed assistive personnel in other health emergencies.

Prevalence of peanut and tree nut allergy in the United States determined by means of a random digit dial telephone survey: a 5-year follow-up study

BACKGROUND

Allergy to peanuts and tree nuts (TNs) is the leading cause of fatal and near-fatal food allergic reactions. Peanut allergy appears to be increasing in prevalence.

OBJECTIVES

We sought to determine the prevalence of self-reported peanut and TN allergy among the general population of the United States in 2002 by sex and age and to compare the results with prevalence estimates obtained 5 years earlier.

METHODS

We performed a nationwide, cross-sectional, random telephone survey by using a standardized questionnaire.

RESULTS

A total of 4855 households participated (53% participation rate), representing a census of 13,493 individuals. Peanut allergy, TN allergy, or both was self-reported in 166 (1.2%; 95% CI, 1.0%-1.4%) individuals in 155 (3.2%; 95% CI, 2.7%-3.7%) households, overall prevalence rates similar to those reported in 1997. Also similar to the 1997 survey, the severity level was high, with 79% reporting respiratory or multiple organ system reactions and 66% experiencing more than 5 lifetime reactions. Despite the severity and reaction frequency, only 74% of the children and 44% of the adults sought evaluation for the allergy, and fewer than half who did were prescribed self-injectable epinephrine. Applying conservative rules to adjust for persons with unconvincing reactions and a false-positive rate of the survey instrument (7%), a final prevalence estimate of 1.04% (95% CI, 0.9%-1.24%) was obtained. A male predominance of peanut-TN allergy was reported in children younger than 18 years (1.7% vs 0.7%, P =.02), and a female predominance was reported among adults (1.7% vs 0.9%, P =.0008). Although the rate of peanut allergy, TN allergy, or both was not significantly different from 1997 to 2002 among adults, the rate increased from 0.6% to 1.2% among children, primarily as a result of an increase in reported allergy to peanut (0.4% in 1997 to 0.8% in 2002, P =.05).

CONCLUSIONS

Self-reported peanut allergy has doubled among children from 1997 to 2002, and peanut allergies, TN allergies, or both continue to be reported by more than 3 million Americans. Considering that reactions are severe and the allergy is persistent, these allergies represent an increasing health concern.

Prevalence of peanut allergy in primary-school children in Montreal, Canada

BACKGROUND

Peanut allergy is receiving increasing attention. Only one study has estimated the prevalence in North America, but it did not corroborate history with diagnostic testing.

OBJECTIVE

We estimated the prevalence of peanut allergy in Montreal by administering questionnaires regarding peanut ingestion to children in kindergarten through grade 3 in randomly selected schools.

METHODS

Respondents were stratified as follows: (1). peanut tolerant, (2). never-rarely ingest peanut, (3). convincing history of peanut allergy, and (4). uncertain history of peanut allergy. Groups 2, 3, and 4 underwent peanut skin prick tests (SPTs), and if the responses were positive in groups 2 or 4, measurement of peanut-specific IgE were undertaken. Children in group 3 with a positive SPT response were considered allergic to peanut without further testing. Children in groups 2 and 4 with peanut-specific IgE levels of less than 15 kU/L underwent oral peanut challenges.

RESULTS

Of the 7768 children surveyed, 4339 responded, 94.6% in group 1. The prevalence of peanut allergy was 1.50% (95% CI, 1.16%-1.92%). When multiple imputation was used to incorporate data on those responding to the questionnaire but withdrawing before testing, the estimated prevalence increased to 1.76% (95% CI, 1.38%-2.21%). When data regarding the peanut allergy status of nonresponders (as declared to the school before the study) were also incorporated, the estimated prevalence was 1.34% (95% CI, 1.08%-1.64%).

CONCLUSION

Our prevalence study is the first in North America to corroborate history with confirmatory testing and the largest worldwide to incorporate these techniques. We have shown that, even with conservative assumptions, prevalence exceeds 1.0%.

Combined skin prick and patch testing enhances identification of peanut-allergic patients with atopic dermatitis

BACKGROUND

Food atopy patch tests (APTs) are considered a useful tool for the diagnosis of food allergy. Hypersensitivity to peanuts has not been investigated by means of APTs so far.

METHODS

APTs and skin prick tests (SPTs) with peanuts were performed in 136 atopic dermatitis (AD) patients. Relevance of positive and negative responses to these tests was assessed by repeated open challenges with peanuts.

RESULTS

Nine percent of our AD patients reacted to the challenge. Positive responses to APTs were recorded in 19% of the patients, whereas in 12% positive SPTs were observed. APTs were more frequently positive in subjects with eczematous responses after challenge with respect to those with urticarial reactions. SPT reactivity proved to be higher in patients above 12 years of age, whereas APT positivity was more frequent in children under 6 years. APT sensitivity proved significantly higher than SPT sensitivity, in particular in children under 12 years of age. On the contrary, SPT specificity and positive predictive value were significantly higher with respect to those of APT in the age group of subjects under 6 years of age.

CONCLUSIONS

Our data suggest that APTs with peanuts may represent a useful integration to standard testing modalities employed for the diagnosis of peanut allergy in AD patients.

Genetic susceptibility to food allergy is linked to differential TH2-TH1 responses in C3H/HeJ and BALB/c mice

BACKGROUND

Although food allergy is a serious health problem in westernized countries, factors influencing the development of food allergy are largely unknown. Appropriate murine models of food allergy would be useful in understanding the mechanisms underlying food allergy in human subjects.

OBJECTIVE

We sought to determine the susceptibility of different strains of mice to food hypersensitivity.

METHODS

C3H/HeJ and BALB/c mice were sensitized to cow's milk (CM) or peanut by means of intragastric administration, with cholera toxin as a mucosal adjuvant. Mice were then challenged with CM or peanut. Antigen-specific IgE levels, anaphylactic symptoms, plasma histamine levels, and splenocyte cytokine profiles of these 2 strains were compared.

RESULTS

CM-specific IgE levels were significantly increased only in the C3H/HeJ strain, 87% of which exhibited systemic anaphylactic reactions accompanied by significantly increased plasma histamine levels in response to challenge. BALB/c mice exhibited no significant CM-specific IgE response, increased plasma histamine levels, or anaphylactic symptoms. After peanut challenge, 100% of peanut-sensitized C3H/HeJ mice exhibited high levels of peanut-specific IgE and anaphylactic symptoms. In contrast, no hypersensitivity reactions were detected in BALB/c mice, despite the presence of significant serum peanut-specific IgE levels. Splenocytes from CM- and peanut-sensitized C3H/HeJ mice exhibited significantly increased IL-4 and IL-10 secretion, whereas splenocytes from BALB/c mice exhibited significantly increased IFN-gamma secretion.

CONCLUSION

Induction of food-induced hypersensitivity reactions in mice is strain dependent, with C3H/HeJ mice being susceptible and BALB/c mice being resistant. This strain-dependent susceptibility to food allergy is associated with differential T(H)2-T(H)1 responses after intragastric food allergen sensitization.