Desensitization and remission after peanut sublingual immunotherapy in 1- to 4-year-old peanut-allergic children: A randomized, placebo-controlled trial

BACKGROUND

Prior studies of peanut sublingual immunotherapy (SLIT) have suggested a potential advantage with younger age at treatment initiation.

OBJECTIVE

We studied the safety and efficacy of SLIT for peanut allergy in 1- to 4-year-old children.

METHODS

Peanut-allergic 1- to 4-year-old children were randomized to receive 4 mg peanut SLIT versus placebo. Desensitization was assessed by double-blind, placebo-controlled food challenge (DBPCFC) after 36 months of treatment. Participants desensitized to at least 443 mg peanut protein discontinued therapy for 3 months and then underwent DBPCFC to assess for remission. Biomarkers were measured at baseline and longitudinally during treatment.

RESULTS

Fifty participants (25 peanut SLIT, 25 placebo) with a median age of 2.4 years were enrolled across 2 sites. The primary end point of desensitization was met with actively treated versus placebo participants having a significantly greater median cumulative tolerated dose (4443 mg vs 143 mg), higher likelihood of passing the month 36 DBPCFC (60% vs 0), and higher likelihood of demonstrating remission (48% vs 0). The highest rate of desensitization and remission was seen in 1- to 2-year-olds, followed by 2- to 3-year-olds and 3- to 4-year-olds. Longitudinal changes in peanut skin prick testing, peanut-specific IgG4, and peanut-specific IgG4/IgE ratio were seen in peanut SLIT but not placebo participants. Oropharyngeal itching was more commonly reported by peanut SLIT than placebo participants. Skin, gastrointestinal, upper respiratory, lower respiratory, and multisystem adverse events were similar between treatment groups.

CONCLUSION

Peanut SLIT safely induces desensitization and remission in 1- to 4-year-old children, with improved outcomes seen with younger age at initiation.

Environmental Exposure to Foods as a Risk Factor for Food Allergy

PURPOSE OF REVIEW

Many factors have been reported to contribute to the development of food allergy. Here, we summarize the role of environmental exposure to foods as a major risk factor for developing food allergy.

RECENT FINDINGS

Peanut proteins are detectable and biologically active in household environments, where infants spend a majority of their time, providing an environmental source of allergen exposure. Recent evidence from clinical studies and mouse models suggests both the airway and skin are routes of exposure that lead to peanut sensitization. Environmental exposure to peanut has been clearly associated with the development of peanut allergy, although other factors such as genetic predisposition, microbial exposures, and timing of oral feeding of allergens also likely contribute. Future studies should more comprehensively assess the contributions of each of these factors for a variety of food allergens to provide more clear targets for prevention of food allergy.

Association Between Earlier Introduction of Peanut and Prevalence of Peanut Allergy in Infants in Australia

IMPORTANCE

Randomized clinical trials showed that earlier peanut introduction can prevent peanut allergy in select high-risk populations. This led to changes in infant feeding guidelines in 2016 to recommend early peanut introduction for all infants to reduce the risk of peanut allergy.

OBJECTIVE

To measure the change in population prevalence of peanut allergy in infants after the introduction of these new guidelines and evaluate the association between early peanut introduction and peanut allergy.

DESIGN

Two population-based cross-sectional samples of infants aged 12 months were recruited 10 years apart using the same sampling frame and methods to allow comparison of changes over time. Infants were recruited from immunization centers around Melbourne, Australia. Infants attending their 12-month immunization visit were eligible to participate (eligible age range, 11-15 months), regardless of history of peanut exposure or allergy history.

EXPOSURES

Questionnaires collected data on demographics, food allergy risk factors, peanut introduction, and reactions.

MAIN OUTCOME AND MEASURES

All infants underwent skin prick tests to peanut and those with positive results underwent oral food challenges. Prevalence estimates were standardized to account for changes in population demographics over time.

RESULTS

This study included 7209 infants (1933 in 2018-2019 and 5276 in 2007-2011). Of the participants in the older vs more recent cohort, 51.8% vs 50.8% were male; median (IQR) ages were 12.5 (12.2-13.0) months vs 12.4 (12.2-12.9) months. There was an increase in infants of East Asian ancestry over time (16.5% in 2018-2019 vs 10.5% in 2007-2011), which is a food allergy risk factor. After standardizing for infant ancestry and other demographics changes, peanut allergy prevalence was 2.6% (95% CI, 1.8%-3.4%) in 2018-2019, compared with 3.1% in 2007-2011 (difference, -0.5% [95% CI, -1.4% to 0.4%]; P = .26). Earlier age of peanut introduction was significantly associated with a lower risk of peanut allergy among infants of Australian ancestry in 2018-2019 (age 12 months compared with age 6 months or younger: adjusted odds ratio, 0.08 [05% CI, 0.02-0.36]; age 12 months compared with 7 to less than 10 months: adjusted odds ratio, 0.09 [95% CI, 0.02-0.53]), but not significant among infants of East Asian ancestry (P for interaction = .002).

CONCLUSIONS AND RELEVANCE

In cross-sectional analyses, introduction of a guideline recommending early peanut introduction in Australia was not associated with a statistically significant lower or higher prevalence of peanut allergy across the population.

IgE-Mediated Peanut Allergy: Current and Novel Predictive Biomarkers for Clinical Phenotypes Using Multi-Omics Approaches

Food allergy is a collective term for several immune-mediated responses to food. IgE-mediated food allergy is the best-known subtype. The patients present with a marked diversity of clinical profiles including symptomatic manifestations, threshold reactivity and reaction kinetics. In-vitro predictors of these clinical phenotypes are evasive and considered as knowledge gaps in food allergy diagnosis and risk management. Peanut allergy is a relevant disease model where pioneer discoveries were made in diagnosis, immunotherapy and prevention. This review provides an overview on the immune basis for phenotype variations in peanut-allergic individuals, in the light of future patient stratification along emerging omic-areas. Beyond specific IgE-signatures and basophil reactivity profiles with established correlation to clinical outcome, allergenomics, mass spectrometric resolution of peripheral allergen tracing, might be a fundamental approach to understand disease pathophysiology underlying biomarker discovery. Deep immune phenotyping is thought to reveal differential cell responses but also, gene expression and gene methylation profiles (eg, peanut severity genes) are promising areas for biomarker research. Finally, the study of microbiome-host interactions with a focus on the immune system modulation might hold the key to understand tissue-specific responses and symptoms. The immune mechanism underlying acute food-allergic events remains elusive until today. Deciphering this immunological response shall enable to identify novel biomarker for stratification of patients into reaction endotypes. The availability of powerful multi-omics technologies, together with integrated data analysis, network-based approaches and unbiased machine learning holds out the prospect of providing clinically useful biomarkers or biomarker signatures being predictive for reaction phenotypes.

Transcriptional frameshifts contribute to protein allergenicity

Transcription infidelity (TI) is a mechanism that increases RNA and protein diversity. We found that single-base omissions (i.e., gaps) occurred at significantly higher rates in the RNA of highly allergenic legumes. Transcripts from peanut, soybean, sesame, and mite allergens contained a higher density of gaps than those of nonallergens. Allergen transcripts translate into proteins with a cationic carboxy terminus depleted in hydrophobic residues. In mice, recombinant TI variants of the peanut allergen Ara h 2, but not the canonical allergen itself, induced, without adjuvant, the production of anaphylactogenic specific IgE (sIgE), binding to linear epitopes on both canonical and TI segments of the TI variants. The removal of cationic proteins from bovine lactoserum markedly reduced its capacity to induce sIgE. In peanut-allergic children, the sIgE reactivity was directed toward both canonical and TI segments of Ara h 2 variants. We discovered 2 peanut allergens, which we believe to be previously unreported, because of their RNA-DNA divergence gap patterns and TI peptide amino acid composition. Finally, we showed that the sIgE of children with IgE-negative milk allergy targeted cationic proteins in lactoserum. We propose that it is not the canonical allergens, but their TI variants, that initiate sIgE isotype switching, while both canonical and TI variants elicit clinical allergic reactions.

Detection of Peanut Allergen Ara h 6 in Commercially Processed Foods using a Single-Walled Carbon Nanotube-Based Biosensor

BACKGROUND

The peanut protein Arachis hypogaea (Ara h) 6 is one of the most serious food allergens that contributes to food-related, life-threatening problems worldwide. The extremely low allergic dose demands for more selective and rapid methods for detecting Ara h 6.

OBJECTIVE

The goal of this study was to develop a single-walled carbon nanotube (SWCNT)-based biosensor for the rapid detection of Ara h 6 in commercial food products.

METHODS

The detection principle of this biosensor was based on the binding of Ara h 6 to the anti-Ara h 6 antibody (pAb) through 1-pyrenibutanoic acid succinimidyl ester. The resistance difference (ΔR) was calculated via linear sweep voltammetry using a potentiostat.

RESULTS

The ΔR increased as the Ara h 6 concentrations increased above the range of 100-107 pg/L. A specificity analysis showed that the anti-Ara h 6 pAb selectively interacted with Ara h 6 molecules in the buffer solution (pH 7.4).

CONCLUSIONS

This research proposes that an SWCNT-based biosensor in self-assembly with antibodies could be an effective tool for the rapid detection of allergen proteins in food.

HIGHLIGHTS

The developed biosensor exhibited higher sensitivity and selectivity. Application studies resulted in precise Ara h 6 detection in peanut-containing processed food.

Ara h2 levels in dust from homes of individuals with peanut allergy and individuals with peanut tolerance

BACKGROUND

Approximately 1% of the U.S. population has a peanut allergy. Previous studies that measured peanut protein in house dust support the hypothesis that household peanut consumption may lead to clinical sensitization through transdermal exposure.

OBJECTIVE

The aim of this pilot study was to characterize Ara h2 levels in house dust from homes with and without individuals with peanut allergy.

METHODS

Household dust was obtained from homes with an individual with peanut allergy and from homes with no individual with peanut allergy. Ara h2 levels were determined by using a monoclonal antibody-based immunoassay with a level of determination of 150 ng per gram of dust. Peanut consumption information was obtained by questionnaire.

RESULTS

A total of 85 dust samples were collected: 38 from homes with a individual with peanut allergy and 47 from control homes. The median Ara h2 level in homes with an individual with peanut allergy was 1236 ng/g (interquartile range [IQR], 256-1342 ng/g), whereas the median Ara h2 level in homes without an individual with peanut allergy was 650 ng/g (IQR, 163-2201 ng/g). Ara h2 levels in dust from homes of individuals with peanut allergy were not significantly lower than in dust from control homes. Of the homes with an individual with peanut allergy, 15 reported complete avoidance of peanut in the home (39%). Ara h2 levels in homes that completely avoided peanuts were not significantly lower than Ara h2 levels in homes that did not restrict peanuts (p = 0.531).

CONCLUSION

Although families may restrict peanuts and peanut products in the home, there was still detectable Ara h2 levels found in homes. Each subject's definition of restriction may vary, there seemed to be peanut protein entering the home, although the protein origin is not known. Possibilities include cross-reactivity with another antigen or transport into the home on some vector. Further investigation of hypotheses regarding cross-reactivity and environmental exposure to Ara h2 is necessary.

Ara h 6 sensitization in peanut allergy: friend, foe or innocent bystander?

The clinical role of Ara h 6 sensitization in peanut allergy is a current matter of debate. We investigated the role of Ara h 6 sensitization patterns in a sample of young adults from different Italian cities. Sera of 33 patients with specific IgE against Ara h 6 were selected. According to clinical symptoms upon peanut ingestion, patients were divided into severe reaction (SR) and mild-tolerant (MT) subgroups. While the SR group mainly showed sensitization patterns involving Ara h 2 and other major allergenic components, a previously undescribed association between Ara h 6 and Ara h 9 was found in the MT group. This pattern seems to be clustered in Mediterranean Italy and associated with Pru p 3 sensitization. This finding might shed a new light on the role of Ara h 6 sensitization in peanut allergy.

Consensus communication on early peanut introduction and the prevention of peanut allergy in high-risk infants

The purpose of this brief communication is to highlight emerging evidence to existing guidelines regarding potential benefits of supporting early, rather than delayed, peanut introduction during the period of complementary food introduction in infants. This document should be considered as interim guidance based on consensus among the following organizations: American Academy of Allergy, Asthma & Immunology, American Academy of Pediatrics, American College of Allergy, Asthma & Immunology, Australasian Society of Clinical Immunology and Allergy, Canadian Society of Allergy and Clinical Immunology, European Academy of Allergy and Clinical Immunology, Israel Association of Allergy and Clinical Immunology, Japanese Society for Allergology, Society for Pediatric Dermatology, and World Allergy Organization. More formal guidelines regarding early-life, complementary feeding practices and the risk of allergy development will follow in the next year from the National Institute of Allergy and Infectious Diseases-sponsored Working Group and the European Academy of Allergy and Clinical Immunology.

Skin exposure promotes a Th2-dependent sensitization to peanut allergens

Sensitization to foods often occurs in infancy, without a known prior oral exposure, suggesting that alternative exposure routes contribute to food allergy. Here, we tested the hypothesis that peanut proteins activate innate immune pathways in the skin that promote sensitization. We exposed mice to peanut protein extract on undamaged areas of skin and observed that repeated topical exposure to peanut allergens led to sensitization and anaphylaxis upon rechallenge. In mice, this epicutaneous peanut exposure induced sensitization to the peanut components Ara h 1 and Ara h 2, which is also observed in human peanut allergy. Both crude peanut extract and Ara h 2 alone served as adjuvants, as both induced a bystander sensitization that was similar to that induced by the atopic dermatitis-associated staphylococcal enterotoxin B. In cultured human keratinocytes and in murine skin, peanut extract directly induced cytokine expression. Moreover, topical peanut extract application induced an alteration dependent on the IL-33 receptor ST2 in skin-draining DCs, resulting in Th2 cytokine production from T cells. Together, our data support the hypothesis that peanuts are allergenic due to inherent adjuvant activity and suggest that skin exposure to food allergens contributes to sensitization to foods in early life.

Peanut allergens

The earliest known evidence of peanut farming dates back 7,600 years. With a prevalence of roughly 1%, peanut allergy is a diagnostic and treatment challenge, but is also a very good model for studying all aspects of food allergy, including its molecular basis and pathomechanisms. Therefore, the very starting point for elucidating all these aspects is the identification of peanut allergens with subsequent clearing of their structure and their preparation as pure recombinant and/or natural allergens. This is the basis for in vitro diagnostic tests as well as the development of immunotherapeutic drugs. With regard to class I food allergy, peanut allergy affects by far the largest group of patients. In peanuts, 12 allergens have been identified and their molecular characteristics are described herein. Ara h 1, Ara h 3.01 and Ara h 3.02 (the former Ara h 4) belong to the cupin superfamily. The conglutins Ara h 2, Ara h 6 and Ara h 7, and the non-specific lipid transfer protein Ara h 9 belong to the prolamin superfamily. Ara h 5 (profilin) and Ara h 8 (Bet v 1-homologous protein) cause class II food allergies and are associated with inhalation allergy to pollen via the sequential and/or conformational similarity of molecules. Two peanut oleosins are listed as Ara h 10 and Ara h 11 and two defensins as Ara h 12 and Ara h 13 by the WHO/IUIS Allergen Nomenclature Subcommittee. The effect of the above-specified allergens has to be considered in the context of their matrix, which is influenced by processing factors and the individual's immune system.

Bayesian sample size determination for case-control studies when exposure may be misclassified

Odds ratios are frequently used for estimating the effect of an exposure on the probability of disease in case-control studies. In planning such studies, methods for sample size determination are required to ensure sufficient accuracy in estimating odds ratios once the data are collected. Often, the exposure used in epidemiologic studies is not perfectly ascertained. This can arise from recall bias, the use of a proxy exposure measurement, uncertain work exposure history, and laboratory or other errors. The resulting misclassification can have large impacts on the accuracy and precision of estimators, and specialized estimation techniques have been developed to adjust for these biases. However, much less work has been done to account for the anticipated decrease in the precision of estimators at the design stage. Here, we develop methods for sample size determination for odds ratios in the presence of exposure misclassification by using several interval-based Bayesian criteria. By using a series of prototypical examples, we compare sample size requirements after adjustment for misclassification with those required when this problem is ignored. We illustrate the methods by planning a case-control study of the effect of late introduction of peanut to the diet of children to the subsequent development of peanut allergy.

Global proteomic screening of protein allergens and advanced glycation endproducts in thermally processed peanuts

Peanuts (Arachis hypogaea) are the cause of one of the most prevalent food allergies worldwide. Thermal processing (e.g., roasting) of peanuts and peanut-containing foods results in complex chemical reactions that alter structural conformations of peanut proteins, preventing accurate detection of allergens by most immunochemical and targeted screening methodologies. To improve food allergen detection and support more accurate food labeling, traditional methods for peanut protein extraction were modified to include protein denaturants and solubilization agents. Qualitative characterization by SDS-PAGE and Western blot analyses of raw and variably roasted peanut extracts confirmed improvements in total protein recovery and provided evidence for the incorporation of Ara h 1, Ara h 3, and, to a lesser extent, Ara h 2 into high molecular weight protein complexes upon roasting. Relative quantification of allergens in peanut lysates was accomplished by label-free spectral feature (MS1) LC-MS/MS methodologies, by which peanut allergen peptides exhibiting a differential MS response in raw versus roasted peanuts were considered to be candidate targets of thermal modification. Identification of lysine-modified Maillard advanced glycation endproducts (AGE) by LC-MS/MS confirmed the formation of (carboxymethyl)lysine (CML), (carboxyethyl)lysine (CEL), and pyrraline (Pyr) protein modifications on Ara h 1 and Ara h 3 tryptic peptides in roasted peanut varieties. These results suggest that complex processed food matrices require initial analysis by an untargeted LC-MS/MS approach to determine optimum analytes for subsequent targeted allergen analyses.

Impact of thermal processing on ELISA detection of peanut allergens

This study examined the effect of heat treatment on the solubility of peanut proteins and compared the performances of two commercial ELISA kits (Veratox Quantitative Peanut Allergen Test and BioKits Peanut Assay Kit) for quantitation of peanut residues as affected by different heat treatments (moist and dry heat) and detection targets (mixture of proteins vs specific protein). Both laboratory-prepared and commercial peanut flour preparations were used for the evaluation. The two ELISA kits tended to underestimate the levels of protein in samples that were subjected to elevated heat, respectively, by more than 60- or 400-fold lower for the autoclaved samples and by as much as 70- or 2000-fold lower for the dark-roast commercial flour samples. The BioKits test, which employs antibodies specific to a heat labile protein (Ara h 1), in general exhibited a greater degree of underestimation. These results suggest that commercial ELISA kits may not be able to accurately determine the amount of proteins present in thermally processed foods due to changes in the solubility and immunoreactivity of the target proteins. Users need to be aware of such limitations before applying ELISA kits for evaluation of food allergen control programs.

Significance of Ara h 2 in clinical reactivity and effect of cooking methods on allergenicity

BACKGROUND

The prevalence and clinical severity of peanut allergy vary between Western countries and Asia. It has been suggested that cooking methods are responsible for this discrepancy.

OBJECTIVES

To evaluate the specific IgE responses to major peanut allergens in peanut allergic Korean children and to examine the influence of different cooking methods on peanut proteins.

METHODS

Raw peanut protein extracts were immunolabeled with serum samples from 42 children with a level of peanut specific IgE of 15 kUA/L or higher to detect specific binding to Ara h 1, Ara h 2, and Ara h 3. Clinical severity scores were assessed on a scale of 0 to 5. Protein extracts from boiled, roasted, fried, and pickled peanuts were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with pooled serum samples from 7 patients.

RESULTS

Most patients' serum samples reacted with Ara h 1 (76.2%) and Ara h 3 (78.6%) from raw peanuts, whereas only 53.0% of patients had specific IgE against Ara h 2. IgE binding to Ara h 2 was more prevalent in patients with more severe reaction than in those with mild reactions. IgE binding to Ara h 2 was increased by roasting, but there was significantly less IgE binding after vinegar treatment.

CONCLUSION

Our results suggest that Ara h 2 is an important allergen to predict clinical symptoms but less prevalent in Korean children than in Western children. This finding may be attributed in part to different cooking methods and dietary habits among regions.

Basophil activation reveals divergent patient-specific responses to thermally processed peanuts

INTRODUCTION

The impact of processing on the allergenicity of peanut (Arachis hypogaea) proteins has traditionally been studied using immunoglobulin (Ig) E binding assay. However, as this technique does not assess the potential of an allergen to trigger basophils and mast cells, studies based on it can hardly be considered complete. We evaluated the effect of processing on peanut allergenicity using flow-cytometric quantification of in vitro basophil activation (basophil activation test [BAT]).

PATIENTS AND METHODS

Basophils from 10 patients with severe peanut allergy and 3 peanut-tolerant individuals were stimulated with extracts from 5 raw and thermally processed peanut varieties. Data were compared using protein staining (sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE]) and IgE immunoblotting.

RESULTS

Stimulation with different extracts resulted in patient-dependent and variety-dependent effects on basophil activation. SDS-PAGE revealed a considerable loss of identifiable bands, especially for the South Africa Common Natal, Argentina Runner, and US Virginia varieties. The results of IgE immunoblotting in patients were similar, irrespective of the responses observed in the BAT.

CONCLUSIONS

The impact of thermal processing on the capacity of peanuts to trigger basophils seems highly divergent between patients and cannot be predicted using SDS-PAGE or IgE binding. BAT can be considered a complementary tool for the evaluation of food allergenicity.

IgE to peanut allergen components: relation to peanut symptoms and pollen sensitization in 8-year-olds

BACKGROUND

Allergen-specific IgE testing is often performed with crude peanut extract, but the results may be difficult to interpret because of cross-reactions between peanut and other plant allergens. The aim was to investigate IgE reactivity to peanut allergen components in children from a birch-rich region in relation to pollen sensitization and peanut symptoms.

METHODS

From a birth cohort, clinical parameters were obtained through questionnaires and IgE antibody levels to peanut and birch pollen were measured. Different peanut/birch sensitization phenotypes were defined among 200 selected children. IgE reactivity to peanut and pollen allergen components was analysed using microarray technique.

RESULTS

Peanut symptoms were reported in 87% of the children with IgE reactivity to any of the peanut allergens Ara h 1, 2 or 3 but not to Ara h 8 (n = 46) vs 17% of children with IgE reactivity to Ara h 8 but not to Ara h 1, 2 or 3 (n = 23), P < 0.001. Furthermore, symptoms were more severe in children with Ara h 1, 2 or 3 reactivity. Children with IgE reactivity both to Ara h 2 and to Ara h 1 or 3 more often reported peanut symptoms than children with IgE only to Ara h 2 (97%vs 70%, P = 0.016), particularly respiratory symptoms (50%vs 9%, P = 0.002).

CONCLUSIONS

IgE analysis to peanut allergen components may be used to distinguish between peanut-sensitized individuals at risk of severe symptoms and those likely to have milder or no symptoms to peanut if sensitized to pollen allergens and their peanut homologue allergens.

[Peanut allergy]

Peanut allergy currently affects around 1% of the UK and US paediatric population and represents a major healthcare concern because it is outgrown in less than 20% of cases and is a major cause of anaphylaxis. Its main symptoms, triggered by peanut ingestion, are cutaneous (urticaria, erythema, angioedema), gastrointestinal (abdominal pain, vomiting, diarrhoea), respiratory (wheezing, dyspnoea) and cardiovascular (hypotension, arrhythmia, shock). The usual onset of symptoms occurs soon after peanut ingestion (minutes to hours); however some patients have biphasic reactions, with exacerbations occurring up to 8 hours later. Peanut allergy diagnostic is based mainly upon the medical history (preferably including a diet diary and elimination diets), skin testing, peanut-specific IgE measurement and ideally a peanut oral challenge. Peanut allergy management includes monitorisation and education for avoiding peanut-containing foods and for recognising and treating anaphylactic episodes (self-injectable adrenalin and rapid-acting antihistamines). In the past, anti-IgE antibodies were shown to decrease the risk of anaphylaxis by reducing the allergic patients' reactivity to peanuts. Recent investigations, driven by the need to develop efficient treatment and prevention strategies for peanut allergy, suggest that oral immunotherapy with peanuts, although exposing the patients to significant risk, may represent a promising therapeutic approach. Furthermore, contrary to the general view that peanut avoidance in infants could prevent peanut allergy, a recent study shows that the opposite may be true as early consumption of peanuts in infancy is associated with a low prevalence of peanut allergy.

Allergy to peanut lipid transfer protein (LTP): frequency and cross-reactivity between peanut and peach LTP

BACKGROUND

Lipid transfer protein (LTP) is a widely cross-reacting plant pan-allergen, and sensitized patients may react to many foods. Although peanut allergy is frequently reported by LTP-allergic patients, the evidence of the presence of an allergen homologous to LTP in peanuts is limited.

OBJECTIVE

To assess the prevalence of peanut allergy in patients sensitized to LTP, detect any allergen homologous to LTP in peanuts, and assess its cross-reactivity with peach LTP.

METHODS

Spanish and Italian adults monosensitized to LTP were interviewed for possible peanut allergy and underwent skin prick tests (SPTs) with peanut extract. Sera from 32 peanut-allergic patients were assayed for peanut-specific IgE by direct ELISA and the Real Test; the serum showing the strongest reactivity was used in immunoblot analysis.

RESULTS

74/114 (65%) patients were sensitized to peanuts, and 37 (32% of the whole population; 50% of those sensitized) were clinically allergic. Positive histories were validated by open oral food challenges in 13/13 cases. No SPT-negative patients reported clinical allergy to peanuts. Thus, in this selected population, sensitivity and negative predictive value of peanut SPTs were 100%, whereas specificity and positive predictive value were poor (52% and 32%, respectively). Only 2/32 sera scored positive in both in vitro assays and 4 reacted in the Real Test alone. In immunoblot, the serum studied reacted at about 10 kDa against the peanut extract; pre-adsorption with purified peach LTP totally inhibited such reactivity.

CONCLUSIONS

Peanut sensitization is frequent among LTP-allergic patients and is clinically significant in about 50% of cases. Peanut tolerance should be assessed in LTP-allergic patients positive on peanut SPTs. Peanut LTP seemingly shares all allergenic determinants with peach LTP.

Naseptin® and peanut oil: a survey of practitioners' awareness in the UK

Objective:

The aim of this study was to determine how aware ENT practitioners are that Naseptin® (Alliance), widely used in ENT practice, contains peanut oil and to what extent this is conveyed to patients.

Methods:

A questionnaire was sent out to all ENT practitioners registered with the British Association of Otolaryngologists.

Result:

Analysis of the data confirmed that Naseptin cream is widely used in ENT practice and showed that although most practitioners are aware that Naseptin cream contains refined peanut oil (arachis oil) (74.3 per cent of consultants and 93.6 per cent of registrars) not all ask their patients whether they are allergic to peanuts (62.6 per cent of consultants and 87.3 per cent of registrars).

Conclusion:

The results suggest that more should be done to raise awareness amongst practitioners that Naseptin cream contains peanut oil and should be avoided in patients with a peanut allergy, as recommended by national guidelines. The use of Naseptin cream when contraindicated may have medicolegal implications.

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.

Oral sensitization to peanut is highly enhanced by application of peanut extracts to intact skin, but is prevented when CpG and cholera toxin are added

BACKGROUND

CpG oligonucleotides might offer an alternative to conventional immunotherapy in preventing and potentially reversing Th2-biased immune deregulation which leads to allergy. However, non-invasive ways of administration, especially in peanut-allergic patients, should be explored.

METHODS

One hundred micrograms of whole peanut protein extract (PE) alone, or mixed with cholera toxin (CT, 50 microg) plus CpG (100 microg) as adjuvant, was applied on intact skin of mice (40 min, twice). Initiation of an immune response was monitored by detection of specific antibodies in sera. The effect of this pretreatment on a further oral sensitization by PE was then evaluated by assaying antibodies and cytokines specific for PE and purified allergens. Cytokine production in liver 40 min after skin application was also assayed.

RESULTS

Two brief skin applications of PE alone highly potentiated further oral sensitization, as demonstrated by very intense specific IgE, IL-4 and IL-5 productions. Conversely, skin pretreatment with PE and CT + CpG efficiently prevented further sensitization via gastro-intestinal exposure. In both cases, the specificity of the antibodies and cytokines was the same as in control mice. CT + CpG treatment allowed the rapid production of IL-12 and TGFbeta in liver and of specific IgG2a in sera, suggesting the activation of Th1 and/or regulatory T cells.

CONCLUSIONS

Oral sensitization to peanut is highly enhanced by a previous short exposure of allergens to intact skin. Conversely, the use of CT + CpG adjuvant for skin application efficiently prevents further oral sensitization. The potential of such treatment in specific immunotherapy needs to be evaluated.

Feeding a soy formula to children with cow's milk allergy: the development of immunoglobulin E-mediated allergy to soy and peanuts

Peanut allergy has been associated with the intake of soy milk or a soy formula. We studied the development of immunoglobulin E antibodies specific to soy and peanuts and of allergic reactions caused by peanuts, in children with confirmed cow's milk (CM) allergy fed either a soy formula or an extensively hydrolyzed formula (EHF). One hundred and seventy infants with documented CM allergy (CMA) were randomly assigned to receive either a soy formula or an EHF. The children were followed to the age of 4 yr. Peanut-specific immunoglobulin E was measured at the age of 4. A detailed history of the occurrence of allergic reactions caused by peanuts was recorded by the parents. Soy-specific immunoglobulin E antibodies were measured at the time of diagnosis and at the ages of 1, 2 and 4 yr. Immunoglobulin E antibodies to soy (> or =0.35 kU/l) were found in 22 of 70 children fed the soy formula, and in 14 of 70 of the children fed the EHF (p = 0.082). In an open challenge with soy at the age of 4, no immediate reactions were observed. One of 72 children from the soy group had a delayed reaction. immunoglobulin E antibodies to peanuts (> or =0.35 kU/l) were found in 21 of 70 children fed the soy formula and 17 of 69 infants fed the EHF (p = 0.717). The incidence of reported peanut allergy in the soy group was two of 72 (3%) and four of 76 (5%) in the EHF group (p = 0.68). Development of immunoglobulin E-associated allergy to soy and peanuts was rare in our study group of milk allergic children. The use of a soy formula during the first 2 yr of life did not increase the risk of development of peanut-specific immunoglobulin E antibodies or of clinical peanut allergy.

Inter-laboratory validation study of five commercial ELISA test kits for the determination of peanut proteins in biscuits and dark chocolate

The results of an inter-laboratory study with five commercially available peanut ELISA test kits to detect and quantify peanut residues in two food matrices (biscuit and dark chocolate) at four different concentrations (0-10 mg peanut kg(-1) matrix corresponding to about 0-2.5 mg peanut protein kg(-1) matrix) are reported. In general the five ELISA test kits evaluated could detect peanut protein in the two food matrices. In three cases, the study challenged the test kits beyond their intended use for quantification below the manufacturers' defined cut-off limits. Generally, all five ELISA test kits performed well in the concentration range 5-10 mg kg(-1) rather than in the low concentration range (2.0 or 2.5 mg kg(-1)). The variation in the found recoveries of peanut between the different test kits had a spread of 44-191% across all concentrations. The quantification characteristics between test kits differed significantly at the very low mg kg(-1) level. Two test kits performed well even at concentrations below 5 mg kg(-1) with reproducibilities of 27-36% for biscuits and 45-57% for chocolate.

Diagnosing peanut allergy with skin prick and specific IgE testing

BACKGROUND

Food allergy is common in childhood. It has been suggested that the magnitude of a skin prick test or specific IgE result can improve diagnostic usefulness, but this has been addressed in only a few tertiary challenge-based studies.

OBJECTIVE

To determine the predictive value of a wheal > or = 8 mm or serum specific IgE > or = 15 kU A /L for clinical allergy and investigate whether results are generalizable.

METHODS

All subjects, up to 16 years of age, who had been investigated with a peanut or tree nut food challenge were eligible for the study. Subjects were referred from either a tertiary allergy clinic or a community birth cohort. All subjects with a history suggestive of food allergy were offered a challenge unless there were features of anaphylaxis. Details of challenges were prospectively recorded. Results were modeled by using logistic regression.

RESULTS

There was a total of 161 peanut challenges. Recent skin prick (longest wheal diameter) and specific IgE data were available for 135 and 136 challenges, respectively. The results suggest that a skin prick result > or = 8 mm and a specific IgE > or = 15 kU A /L have predictive values of 95% (95% CI, 76.2% to 99.9%) and 92.0% (74.0% to 99.0%), respectively, for a positive challenge. Age, the type of nut, and referral pattern of the subject did not appear to alter this relationship.

CONCLUSION

These data suggest that a skin prick result > or = 8 mm or a specific IgE > or = 15 kU A /L have a high predictive value for clinical allergy to peanut and that these cutoff figures appear generalizable to different populations of children undergoing an assessment for peanut allergy.

Peanut allergenicity

OBJECTIVE

To provide the reader with a relevant review of the structure and allergenicity of the major peanut allergens, while also exploring predictors of clinical reactivity to peanuts, the natural history of peanut allergy, and novel therapeutic strategies for peanut hypersensitivity.

DATA SOURCES

A PubMed search for the years 1980 to 2004 was performed using the following search terms: peanut allergy, food allergy, anaphylaxis, peanut allergen structure, and peanut immunotherapy.

STUDY SELECTION

Articles highlighting major advances in the study of peanut allergy were selected for further review.

RESULTS

Peanut allergy is the most serious of the hypersensitivity reactions to foods due to its persistence and high risk of severe anaphylaxis. The major peanut allergens and their associated immunodominant IgE-binding epitopes have been characterized. Definition of these allergens has lead to an increased understanding of the peanut-specific immunologic response and improved predictors of clinical reactivity to peanuts. An understanding of these mechanisms is vital for the eventual development of safe and effective immunotherapy for peanut allergic patients. Novel therapeutic and diagnostic approaches are being developed for patients with peanut hypersensitivity.

CONCLUSIONS

Improved understanding of the molecular structure of the major peanut allergens and the peanut-specific immune response has lead to significant diagnostic and therapeutic advances in the study of peanut allergy.

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.

Peanut allergy: recurrence and its management

BACKGROUND

Although peanut allergy may recur, the frequency with which this occurs is unknown.

OBJECTIVE

The goals of this study were to determine the rate of peanut allergy recurrence, identify risk factors for recurrent peanut allergy, and develop specific recommendations for the treatment of patients with resolved peanut allergy.

METHODS

Children who outgrew peanut allergy were evaluated with questionnaires, skin tests, and peanut-specific IgE levels. Patients were invited to undergo a double-blind, placebo-controlled food challenge (DBPCFC) unless the history of a possible recurrence reaction was so convincing that a challenge would be potentially dangerous.

RESULTS

Sixty-eight patients were evaluated. Forty-seven patients continued to tolerate peanut, of whom 34 ingested concentrated peanut products at least once per month and 13 ate peanut infrequently or in limited amounts but passed a DBPCFC. The status of 18 patients was indeterminate because they ate peanut infrequently or in limited amounts and declined to have a DBPCFC. After excluding 12 patients originally diagnosed with peanut allergy based solely on a positive skin prick test or peanut-specific IgE level, 3 of 15 patients who consumed peanut infrequently or in limited amounts had recurrences, compared with no recurrences in the 23 patients who ate peanut frequently ( P = .025). The recurrence rate was 7.9 (95% CI, 1.7% to 21.4%).

CONCLUSION

Children who outgrow peanut allergy are at risk for recurrence, and this risk is significantly higher for patients who continue largely to avoid peanut after resolution of their allergy. On the basis of these findings, we now recommend that patients eat peanut frequently and carry epinephrine indefinitely until they have demonstrated ongoing peanut tolerance.

Update on food allergy

Tremendous progress has been made in our understanding of food-based allergic disorders over the past 5 years. Recent epidemiologic studies suggest that nearly 4% of Americans are afflicted with food allergies, a prevalence much higher than appreciated in the past. In addition, the prevalence of peanut allergy was found to have doubled in American children less than 5 years of age in the past 5 years. Many food allergens have been characterized at the molecular level, which has contributed to our increased understanding of the immunopathogenesis of many allergic disorders and might soon lead to novel diagnostic and immunotherapeutic approaches. The management of food allergies continues to consist of educating patients on how to avoid relevant allergens, to recognize early symptoms of an allergic reaction in case of an accidental ingestion, and to initiate the appropriate emergency therapy. However, the recent successful clinical trial of anti-IgE therapy in patients with peanut allergy and the number of immunomodulatory therapies in the pipeline provide real hope that we will soon be able to treat patients with food allergy.

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.

Presentation of allergen in different food preparations affects the nature of the allergic reaction - a case series

BACKGROUND

Characterization of fatal and non-fatal reactions to food indicates that the majority of reactions are due to the ingestion of prepared foods rather than the non-processed allergen. In an ongoing study that used a double-blind placebo-controlled food challenge to investigate peanut allergy and clinical symptoms, the observed reaction severity in four of the first six subjects was greater than anticipated. We hypothesized that this was due to differences in the composition of the challenge vehicle.

OBJECTIVE

The aim was to investigate whether the severity of observed challenge reactions would be repeated on re-challenge with a lower fat challenge vehicle.

METHODS

Peanut-allergic subjects were re-challenged with a lower fat recipe after reacting more severely than was anticipated to an initial peanut challenge. Similar challenge vehicle recipes were used, the only difference being the lower fat content (22.9% compared with 31.5%). The peanut content of the two recipes was analysed using RAST inhibition studies and ELISA tests.

RESULTS

Three of four subjects reacted to much smaller doses of peanut protein on re-challenge (mean dose equivalence - 23 times less peanut) with the lower fat recipe. RAST inhibition showed that neither recipe altered epitope recognition. The higher fat recipe required twice as much peanut to cause 50% inhibition. ELISA detected far lower levels of peanut in the higher fat recipe (220 000 parts per million (p.p.m.)) than in the lower fat recipe (990 000 p.p.m.).

CONCLUSION

The fat content of a challenge vehicle has a profound effect on the reaction experienced after allergen ingestion. This is another factor to be considered in assessing the risk of certain foods to food-allergic consumers and adds another dimension to clinical, research and regulatory practice.

Thresholds of clinical reactivity to milk, egg, peanut and sesame in immunoglobulin E-dependent allergies: evaluation by double-blind or single-blind placebo-controlled oral challenges

BACKGROUND

The prevalence of food anaphylaxis due to masked allergens has increased within the last 10 years. Contamination of manufactured products by food allergens is a key concern for food industries.

OBJECTIVE

To determine quantities eliciting reactions in patients who have an IgE-dependent food allergy, thanks to standardized oral provocation tests. To evaluate the subsequent levels of sensitivity required for the detection tests of allergens for egg, peanut, milk and sesame.

METHODS

Prick-in-prick tests, Cap system RAST, and single or double-blind placebo-controlled food challenges (SBPCFC or DBPCFC) were performed. The doses of natural food were gradually increased from 5 to 5000 mg for solid food and from 1 to 30 mL for peanut oil, sunflower oil, soy oil and sesame oil.

RESULTS

Data from 125 positive oral challenges to egg, 103 to peanut, 59 to milk and 12 to sesame seeds were analysed. Haemodynamic modifications were observed in 2%, 3%, 1.7%, and 8% of the oral challenges (OCs) to egg, peanut, milk and sesame, respectively. Respiratory symptoms were observed in 12%, 20%, 10% and 42% of egg, peanut milk and sesame allergies, respectively. A cumulative reactive dose inferior or equal to 65 mg of solid food or 0.8 mL of milk characterized 16%, 18%, 5% and 8% of egg, peanut, milk and sesame allergies, respectively. 0.8% of egg allergies, 3.9% of peanut allergies, and 1.7% of milk allergies reacted to 10 mg or less of solid food or to 0.1 mL for milk. The lowest reactive threshold has been observed at less than 2 mg of egg; 5 mg of peanut, 0.1 mL of milk and 30 mg of sesame seed. Ten out of 29 OC with peanut oil, two out of two OC with soy oil and three out of six OC with sunflower oil were positive. Five out six OC with sesame oil were positive: 1 and 5 mL induced an anaphylactic shock.

CONCLUSION

The risk of asthma and anaphylactic shock to sesame and peanut is confirmed. Minimal reactive quantities show that, in order to guarantee a 95% safety for patients who are allergic to egg, peanut and milk, and on the basis of consumption of 100 g of food, the detection tests should ensure a sensitivity of 10 p.p.m. for egg, 24 p.p.m. for peanut and 30 p.p.m. for milk proteins. Oil allergies being considered, the limit of sensitivity should fall to 5 p.p.m.