Peanut allergy and anaphylaxis

Progress in genetic engineering and genome editing of peanuts: revealing the future of crop improvement

Peanut (Arachis hypogaea L.), also known as groundnut, is cultivated globally and is a widely consumed oilseed crop. Its nutritional composition and abundance in lipids, proteins, vitamins, and essential mineral elements position it as a nutritious food in various forms across the globe, ranging from nuts and confections to peanut butter. Cultivating peanuts provides significant challenges due to abiotic and biotic stress factors and health concerns linked to their consumption, including aflatoxins and allergens. These factors pose risks not only to human health but also to the long-term sustainability of peanut production. Conventional methods, such as traditional and mutation breeding, are time-consuming and do not provide desired genetic variations for peanut improvement. Fortunately, recent advancements in next-generation sequencing and genome editing technologies, coupled with the availability of the complete genome sequence of peanuts, offer promising opportunities to discover novel traits and enhance peanut productivity through innovative biotechnological approaches. In addition, these advancements create opportunities for developing peanut varieties with improved traits, such as increased resistance to pests and diseases, enhanced nutritional content, reduced levels of toxins, anti-nutritional factors and allergens, and increased overall productivity. To achieve these goals, it is crucial to focus on optimizing peanut transformation techniques, genome editing methodologies, stress tolerance mechanisms, functional validation of key genes, and exploring potential applications for peanut improvement. This review aims to illuminate the progress in peanut genetic engineering and genome editing. By closely examining these advancements, we can better understand the developments achieved in these areas.

Enhanced Gut Microbiome Capacity for Amino Acid Metabolism is associated with Peanut Oral Immunotherapy Failure

Peanut Oral Immunotherapy (POIT) holds promise for remission of peanut allergy, though treatment is protracted and successful in only a subset of patients. Because the gut microbiome is linked to food allergy, we sought to identify fecal microbial predictors of POIT efficacy and to develop mechanistic insights into treatment response. Longitudinal functional analysis of the fecal microbiome of children (n=79) undergoing POIT in a first double-blind, placebo-controlled clinical trial, identified five microbial-derived bile acids enriched in fecal samples prior to POIT initiation that predicted treatment efficacy (AUC 0.71). Failure to induce disease remission was associated with a distinct fecal microbiome with enhanced capacity for bile acid deconjugation, amino acid metabolism, and increased peanut peptide degradation in vitro . Thus, microbiome mechanisms of POIT failure appear to include depletion of immunomodulatory secondary bile and amino acids and the antigenic peanut peptides necessary to promote peanut allergy desensitization and remission.

Transfer and distribution of antibiotic resistance genes in the soil-peanut system receiving manure for years

Antibiotic resistance gene (ARG)-contaminated food from manure application is gaining widespread interest, but little is known about the distribution and uptake of ARGs in peanuts that are subjected to manure routinely. In this study, the ARG profile and bacterial community in soil and peanut plants from a 7-year manure-fertilized field were investigated using high-throughput qPCR and 16S rRNA gene sequencing. Manure application increased the abundance of ARGs in soil and peanuts by 59-72 and 4-10 fold, respectively. The abundance of ARGs from high to low was as follows: manure, shell-sphere soil, rhizosphere soil, bulk soil, stems, shells, needles, kernels, and roots. Source-tracker analyses were used to investigate the potential source of ARGs in peanut kernels, which revealed that the ARGs in peanut kernels may be primarily absorbed by the roots from the soil. The horizontal gene transfer (HGT) of ARGs was the primary factor in the spread of ARGs, and Proteobacteria were the primary agents of HGT between different parts of peanut plants. Additionally, norank_Chloroplast from the phylum Cyanobacteria was the most important contributor to the abundance of ARGs in peanut kernels. Overall, our findings fill a gap in our understanding of the distribution patterns of ARGs in peanut plants and the migratory pathways of ARGs from soil to peanut kernels.

Cytometric analysis reveals an association between allergen-responsive natural killer cells and human peanut allergy

Food allergies are a leading cause of anaphylaxis, and allergen-specific immune responses in both the innate and the adaptive immune system play key roles in its pathogenesis. We conducted a comprehensive phenotypic and functional investigation of immune cell responses from nonallergic (NA) and peanut allergic (PA) participants cultured with media alone or peanut protein and found, surprisingly, that NK cell activation was strongly associated with the immune response to allergen in PA participants. Peanut-responsive NK cells manifested a distinct expression pattern in PA participants compared with NA participants. Allergen-activated NK cells expressed both Th2 and immune regulatory cytokines, hinting at a potential functional role in mediating and regulating the Th2 allergic response. Depletion of CD3⁺ T cells attenuated the response of NK cells to peanut-allergen stimulation, suggesting that peanut-responsive NK cells are T cell dependent. We also showed that oral immune therapy was associated with decreased NK responses to peanut allergen stimulation in vitro. These results demonstrate that NK cells are associated with the food-allergic immune response, and the magnitude of this mobilized cell population suggests that they play a functional role in allergic immunity.

Use of a Liver-targeting Nanoparticle Platform to Intervene in Peanut-induced anaphylaxis through delivery of an Ara h2 T-cell Epitope

To address the urgent need for safe food allergen immunotherapy, we have developed a liver-targeting nanoparticle platform, capable of intervening in allergic inflammation, mast cell release and anaphylaxis through the generation of regulatory T-cells (Treg). In this communication, we demonstrate the use of a poly (lactide-co-glycolide acid) (PLGA) nanoparticle platform for intervening in peanut anaphylaxis through the encapsulation and delivery of a dominant protein allergen, Ara h 2 and representative T-cell epitopes, to liver sinusoidal endothelial cells (LSECs). These cells have the capacity to act as natural tolerogenic antigen-presenting cells (APC), capable of Treg generation by T-cell epitope presentation by histocompatibility (MHC) type II complexes on the LSEC surface. This allowed us to address the hypothesis that the tolerogenic nanoparticles platform could be used as an effective, safe, and scalable intervention for suppressing anaphylaxis to crude peanut allergen extract. Following the analysis of purified Ara h 2 and representative MHC-II epitopes Treg generation in vivo, a study was carried out to compare the best-performing Ara h 2 T-cell epitope with a purified Ara h 2 allergen, a crude peanut protein extract (CPPE) and a control peptide in an oral sensitization model. Prophylactic as well as post-sensitization administration of the dominant encapsulated Ara h 2 T-cell epitope was more effective than the purified Ara h2 in eliminating anaphylactic manifestations, hypothermia, and mast cell protease release in a frequently used peanut anaphylaxis model. This was accompanied by decreased peanut-specific IgE blood levels and increased TGF-β release in the abdominal cavity. The duration of the prophylactic effect was sustained for two months. These results demonstrate that targeted delivery of carefully selected T-cell epitopes to natural tolerogenic liver APC could serve as an effective platform for the treatment of peanut allergen anaphylaxis.

White paper on peanut allergy - part 1: Epidemiology, burden of disease, health economic aspects

Peanuts are Leguminosae, commonly known as the legume or pea family, and peanut allergy is among the most common food allergies and the most common cause of fatal food reactions and anaphylaxis.

The prevalence of peanut allergy increased 3.5-fold over the past two decades reaching 1.4–2% in Europe and the United States. The reasons for this increase in prevalence are likely multifaceted. Sensitization via the skin appears to be associated with the development of peanut allergy and atopic eczema in infancy is associated with a high risk of developing peanut allergy.

Until recently, the only possible management strategy for peanut allergy was strict allergen avoidance and emergency treatment including adrenaline auto-injector in cases of accidental exposure and reaction.

This paper discusses the various factors that impact the risks of peanut allergy and the burden of self-management on peanut-allergic children and their caregivers.

Research on the Structure of Peanut Allergen Protein Ara h1 Based on Aquaphotomics

Peanut allergy is becoming a life-threatening disease that could induce severe allergic reactions in modern society, especially for children. The most promising method applied for deallergization is heating pretreatment. However, the mechanism from the view of spectroscopy has not been illustrated. In this study, near-infrared spectroscopy (NIRS) combined with aquaphotomics was introduced to help us understand the detailed structural changes information during the heating process. First, near-infrared (NIR) spectra of Ara h1 were acquired from 25 to 80°C. Then, aquaphotomics processing tools including principal component analysis (PCA), continuous wavelet transform (CWT), and two-dimensional correlation spectroscopy (2D-COS) were utilized for better understanding the thermodynamic changes, secondary structure, and the hydrogen bond network of Ara h1. The results indicated that about 55°C could be a key temperature, which was the structural change point. During the heating process, the hydrogen bond network was destroyed, free water was increased, and the content of protein secondary structure was changed. Moreover, it could reveal the interaction between the water structure and Ara h1 from the perspective of water molecules, and explain the effect of temperature on the Ara h1 structure and hydrogen-bonding system. Thus, this study described a new way to explore the thermodynamic properties of Ara h1 from the perspective of spectroscopy and laid a theoretical foundation for the application of temperature-desensitized protein products.

Effects of Maillard reaction on structural modification and potential allergenicity of peanut 7S globulin (Ara h 1)

BACKGROUND

Ara h 1 is a major food allergen in peanuts. Recently, many studies have revealed that the Maillard reaction (MR) affects the allergenicity of food proteins.

RESULTS

To investigate the influence of the MR on the allergenicity of Ara h 1, R-Ara h 1 was processed with glucose in dry heating conditions for different periods. The extent of the MR was assessed by four methods. The changes in secondary and tertiary structures were characterized through spectroscopy assays. Advanced glycation end products (AGE) structures were identified by protein sample dry heating for 60 min, indicating the formation of AGE-Ara h 1. Simulated gastric fluid (SGF) digestion analysis showed that AGE-Ara h 1 has higher resistance to peptic digestion than R-Ara h 1. The BALB/c mouse model was also utilized to explore the effect of the MR on the allergenicity of Ara h 1, and the results showed that the Th2-type cytokines, antibodies, and histamine content increased, and there was a greater degree of degranulation of rat basophilic leukemia (RBL) cells in the AGE-Ara h 1 group compared with the R-Ara h 1 group.

CONCLUSION

During the process of dry heating, proteins participated in the MR with changes in secondary and tertiary structures. The condition applying a temperature of 100 °C for 60 min caused the formation of AGE-Ara h 1. Simulated gastric fluid digestion analysis showed that AGE-Ara h 1 had a greater resistance to peptic digestion than R-Ara h 1. The BALB/c mouse model showed that AGE-Ara h 1 had more allergenicity, indicating that the MR could enhance the allergenicity of Ara h 1. © 2020 Society of Chemical Industry.

Hyperspectral Shortwave Infrared Image Analysis for Detection of Adulterants in Almond Powder with One-Class Classification Method

The widely used techniques for analyzing the quality of powdered food products focus on targeted detection with a low-throughput screening of samples. Owing to potentially significant health threats and large-scale adulterations, food regulatory agencies and industries require rapid and non-destructive analytical techniques for the detection of unexpected compounds present in products. Accordingly, shortwave-infrared hyperspectral imaging (SWIR-HSI) for high throughput authenticity analysis of almond powder was investigated in this study. Two different varieties of almond powder, adulterated with apricot and peanut powder at different concentrations, were imaged using the SWIR-HSI system. A one-class classifier technique, known as data-driven soft independent modeling of class analogy (DD-SIMCA), was used on collected data sets of pure and adulterated samples. A partial least square regression (PLSR) model was further developed to predict adulterant concentrations in almond powder. Classification results from DD-SIMCA yielded 100% sensitivity and 89-100% specificity for different validation sets of adulterated samples. The results obtained from the PLSR analysis yielded a high determination coefficient (R2) and low error values (<1%) for each variety of almond powder adulterated with apricot; however, a relatively higher error rates of 2.5% and 4.4% for the two varieties of almond powder adulterated with peanut powder, which indicates the performance of quantitative analysis model could vary with sample condition, such as variety, originality, etc. PLSR-based concentration mapped images visually characterized the adulterant (apricot) concentration in the almond powder. These results demonstrate that the SWIR-HSI technique combined with the one-class classifier DD-SIMCA can be used effectively for a high-throughput quality screening of almond powder regarding potential adulteration.

Effectiveness of different proteases in reducing allergen content and IgE-binding of raw peanuts

The effectiveness of some non-specific proteases in reducing raw peanut allergenicity was investigated. Peanut kernels were treated by Alcalase, papain, Neutrase and bromelain, respectively. The residues of major peanut allergens Ara h 1, Ara h 2 and Ara h 6 were determined by sandwich ELISA and SDS-PAGE, and the allergenicities of treated peanuts were compared to that of untreated peanuts by western blot. All tested proteases were effective in reducing Ara h 1, but their effectiveness in hydrolyzing Ara h 2 and Ara h 6 varied greatly. The maximal reductions of extractable Ara h 1, Ara h 2 and Ara h 6 were 100%, 100% and 99.8%, respectively, achieved by Alcalase hydrolysis. Alcalase was more effective in overall allergenicity reduction; bromelain and Neutrase were the least effective in reducing Ara h 2 and Ara h 6, respectively. The hydrolysis of original allergens also produced some smaller peptides with strong IgE-binding.

Screening of Nanobody Specific for Peanut Major Allergen Ara h 3 by Phage Display

Peanut allergy is a major health problem worldwide. Detection of food allergens is a critical aspect of food safety. The VHH domain of single chain antibody from camelids, also known as nanobody (Nb), showed its advantages in the development of biosensors because of its high stability, small molecular size, and ease of production. However, no nanobody specific to peanut allergens has been developed. In this study, we constructed a library with random triplets (NNK) in its CDR regions of a camel nanobody backbone. We screened the library with peanut allergy Ara h 3 and obtained several candidate nanobodies. One of the promising nanobodies, Nb16 was further biochemical characterization by gel filtration, isothermal titration calorimetry (ITC), cocrystallization, and Western blot in terms of its interaction with Ara h 3. Nb16 specifically binds to peanut major allergen Ara h 3 with a dissociation constant of 400 nM. Furthermore, we obtained the Ara h 3-Nb16 complex crystals. Structure analysis shows the packing mode is completely different between the Ara h 3-Nb16 complex crystal and the native Ara h 3 crystal. Structural determination of Ara h 3-Nb16 will provide the necessary information to understand the allergenicity of this important peanut allergen. The nanobody Nb16 may have application in the development of biosensors for peanut allergen detection.

Suspected Anaphylactic Reaction to Ketamine in 3 Yucatan Swine (Sus scrofa)

This case series describes the clinical courses of 3 juvenile Yucatan miniature swine (Sus scrofa) that experienced a suspected anaphylactic reaction to ketamine hydrochloride during premedication for protocol-related surgery. All 3 swine rapidly developed diffuse erythema shortly after injection with ketamine-containing drug combinations. Clinical signs ranged from tachycardia and erythema alone to tachycardia and erythema followed by respiratory and cardiac arrest. Ketamine was considered the most likely cause of these reactions because it was the only agent in the premedication sedation combination that was used in all 3 swine. Subsequent intradermal skin testing confirmed this suspicion. With supportive care measures and standard medical interventions for anaphylaxis, all 3 animals recovered well and went on to be successful experimental subjects when an alternative anesthetic regimen that did not contain ketamine was used. To our knowledge, this report is the first description of a suspected adverse ketamine reaction of this type in swine despite the widespread use of the drug in this species. Ketamine anaphylaxis is rare in people, but the few cases described presented with symptoms similar to the clinical signs seen in the pigs in this report. In addition to highlighting a potential adverse drug reaction to ketamine in swine, this case series demonstrates the value of emergency preparedness for even the most routine of procedures.

Different thermal processing effects on peanut allergenicity

BACKGROUND

Peanut allergy is one of the most common food allergies worldwide. Studies have shown that the incidence of peanut allergies in Western-born Asians is higher than that in Asia-born Asians. Notably, Europeans and Americans mostly eat roasted peanuts, whereas Asians mostly eat boiled or fried peanuts.

RESULTS

BALB/c mice were sensitized using purified protein from raw, roasted or boiled peanuts, then fed the same by oral gavage. The relevant allergic reactions were studied using BALB/c mice model, including a rat basophilic leukemia (RBL) cell model, simulated gastric fluid experiments, and ultraviolet (UV) and circular dichroism (CD) spectral analysis. Serological studies showed increased levels of immunoglobulin E, interleukin-4 and interleukin-5, and pathological studies showed mast cell degranulation and inflammatory changes in jejunal tissues, with an increase in thymic stromal lymphopoietin (TSLP) gene expression in all treatment groups compared with the control group (phosphate-buffered saline). Compared with the raw peanut group, sera from the roasted peanut group produced a significant increase in RBL β-hexosaminidase A release in vitro, and roasted peanuts showed increased resistance to digestion in simulated gastric fluid experiments. Ultraviolet and CD spectral analyses showed that the roasting and boiling processes altered the structure of the major peanut allergens, which may have contributed to the differences observed in peanut allergenicity.

CONCLUSION

Our findings indicate that peanut allergies are related to peanut thermal processing methods. In our mouse model, the raw, roasted and boiled peanuts elicited different degrees of allergic response. Compared with raw peanut, roasted peanuts show a higher allergenicity, whereas the boiled peanuts show a lower allergenicity. © 2018 Society of Chemical Industry.

Markers of anaphylaxis - a systematic review

Anaphylaxis is defined as severe, life-threatening, systemic or general, immediate reaction of hypersensitivity, with repeatable symptoms caused by the dose of stimulus which is well tolerated by healthy persons. The proper diagnosis, immediate treatment and differential diagnosis are crucial for saving patient's life. However, anaphylaxis is relatively frequently misdiagnosed or confused with other clinical entities. Thus, there is a continuous need for identifying detectable markers improving the proper diagnosis of anaphylaxis. Here we presented currently known markers of anaphylaxis and discussed in more detail the most clinically valuable ones: tryptase, platelet activacting factor (PAF), PAF-acethylhydrolase, histamine and its metabolites.

Age-Based Causes and Clinical Characteristics of Immediate-Type Food Allergy in Korean Children

PURPOSE

Age-based causes and clinical characteristics of immediate-type food allergy (FA) have not been sufficiently studied. Therefore, we investigated age-dependent clinical profiles of FA in Korean children through an extensive multicenter investigation.

METHODS

Using a case report form developed by the authors, a retrospective medical record review was performed of patients (0-18 years old) diagnosed with immediate-type FA between September 2014 and August 2015 in 14 tertiary hospitals in Korea.

RESULTS

A total of 1,353 children and adolescents, 93% younger than 7 years, were enrolled in the present study, and 1,661 cases of immediate-type FA were recorded in these patients. The 7 major causative foods were cow's milk (28.1%), hen's eggs (27.6%), wheat (7.9%), walnuts (7.3%), peanuts (5.3%), buckwheat (1.9%), and shrimps (1.9%). Categorizing the patients into 4 age groups revealed that the most common causative food was different for each age group: cow's milk (<2 years), walnuts (2-6 years), walnuts (7-12 years), and buckwheat (13-18 years). The onset time of symptoms was less than 10 minutes in 49%, between 10 and 30 minutes in 17%, and between 30 minutes and 2 hours in 34% of cases. Food-induced anaphylaxis was reported in 506 (30.5%) out of 1,661 cases, and the 7 major causes of food-induced anaphylaxis was cow's milk (27.5%), hen's eggs (21.9%), wheat (11.3%), walnuts (10.5%), peanuts (5.9%), buckwheat (4.2%), and pine nuts (3.0%). The proportion of anaphylaxis was highest in the patients allergic to buckwheat (67.7%), followed by those allergic to pine nuts (57.7%), walnuts (43.8%), wheat (43.5%), and peanuts (34.1%).

CONCLUSIONS

The 5 major causative foods of immediate-type FA in Korean children were cow's milk, hen's eggs, wheat, walnuts, and peanuts. The distribution of causative foods was considerably distinctive according to different age groups. Anaphylaxis was reported in 30.5% of immediate-type FA cases.

Anaphylaxis Imaging: Non-Invasive Measurement of Surface Body Temperature and Physical Activity in Small Animals

In highly sensitized patients, the encounter with a specific allergen from food, insect stings or medications may rapidly induce systemic anaphylaxis with potentially lethal symptoms. Countless animal models of anaphylaxis, most often in BALB/c mice, were established to understand the pathophysiology and to prove the safety of different treatments. The most common symptoms during anaphylactic shock are drop of body temperature and reduced physical activity. To refine, improve and objectify the currently applied manual monitoring methods, we developed an imaging method for the automated, non-invasive measurement of the whole-body surface temperature and, at the same time, of the horizontal and vertical movement activity of small animals. We tested the anaphylaxis imaging in three in vivo allergy mouse models for i) milk allergy, ii) peanut allergy and iii) egg allergy. These proof-of-principle experiments suggest that the imaging technology represents a reliable non-invasive method for the objective monitoring of small animals during anaphylaxis over time. We propose that the method will be useful for monitoring diseases associated with both, changes in body temperature and in physical behaviour.

Allergens of Arachis hypogaea and the effect of processing on their detection by ELISA

Food allergies are an emerging public health problem in industrialized areas of the world. They represent a considerable health problem in these areas because of the relatively high number of reported cases. Usually, food allergens are proteins or glycoproteins with a molecular mass ranging from 10 to 70 kDa. Among the food allergies, peanut is accounted to be responsible for more than 50% of the food allergy fatalities. Threshold doses for peanut allergenic reactions have been found to range from as low as 100 µg to 1 g of peanut protein, which equal to 400 µg to 4 g peanut meal. Allergens from peanut are mainly seed storage proteins that are composed of conglutin, vicilin, and glycinin families. Several peanut proteins have been identified to induce allergic reactions, particularly Ara h 1-11. This review is mainly focused on different classes of peanut allergens, the effect of thermal and chemical treatment of peanut allergens on the IgY binding and detectability of these allergens by enzyme linked immunosorbent assay (ELISA) to provide knowledge for food industry.

Ten-year review reveals changing trends and severity of allergic reactions to nuts and other foods

AIM

Over the past few decades, the incidence of food allergies has risen and Sweden has increased its import of peanuts and exotic nuts, such as cashew nuts, which may cause severe allergic reactions. This study aimed to retrospectively investigate paediatric emergency visits due to food reactions over a 10-year period, focusing on reactions to peanuts and tree nuts.

METHODS

Emergency visits to Uppsala University Children's Hospital, Sweden, between September 2001 and December 2010, were reviewed, and cases containing diagnostic codes for anaphylaxis, allergic reactions or allergy and hypersensitivity not caused by drugs or biological substances were retrieved.

RESULTS

We analysed 703 emergency visits made by 578 individuals with food allergies. Peanuts and tree nuts accounted for 50% of the food allergies and were more frequently associated with adrenaline treatment and hospitalisation than other foods. Cashew nut reactions increased over the study period, and together with peanuts, they were responsible for more anaphylactic reactions than hazelnuts.

CONCLUSION

Peanut and tree nut reactions were more likely to result in adrenaline treatment and hospitalisation than other food reactions. Peanut and cashew nut reactions were more likely to cause anaphylaxis than hazelnuts. Cashew nut reactions increased during the study period.

Immunogenicity of peanut proteins containing poly(anhydride) nanoparticles

In the last decade, peanut allergy has increased substantially. Significant differences in the prevalence among different countries are attributed to the type of thermal processing. In spite of the high prevalence and the severe reaction induced by peanuts, there is no immunotherapy available. The aim of this work was to evaluate the potential application of poly(anhydride) nanoparticles (NPs) as immunoadjuvants for peanut oral immunotherapy. NPs loaded with raw or roasted peanut proteins were prepared by a solvent displacement method and dried by either lyophilization or spray-drying. After physicochemical characterization, their adjuvant capacity was evaluated after oral immunization of C57BL/6 mice. All nanoparticle formulations induced a balanced T(H)1 and T(H)2 antibody response, accompanied by low specific IgE induction. In addition, oral immunization with spray-dried NPs loaded with peanut proteins was associated with a significant decrease in splenic T(H)2 cytokines (interleukin 4 [IL-4], IL-5, and IL-6) and enhancement of both T(H)1 (gamma interferon [IFN-γ]) and regulatory (IL-10) cytokines. In conclusion, oral immunization with poly(anhydride) NPs, particularly spray-dried formulations, led to a pro-T(H)1 immune response.

Ara h 6 complements Ara h 2 as an important marker for IgE reactivity to peanut

The similarities of two major peanut allergens, Ara h 2 and Ara h 6, in molecular size, amino acid sequence, and structure have made it difficult to obtain natural Ara h 6 free of Ara h 2. The objectives of this study were to purify natural Ara h 6 that is essentially free of Ara h 2 and to compare its IgE reactivity and potency in histamine release assays to Ara h 2. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the highly purified allergen (<0.01% Ara h 2) revealed a single 14.5 kD band, and the identity of Ara h 6 was confirmed by liquid chromatography-tandem mass spectrometry. Ara h 6 showed a higher seroprevalence in chimeric IgE enzyme-linked immunosorbent assay (n = 54) but a weaker biological activity in basophil histamine release assays than Ara h 2. Purified Ara h 6 will be useful for diagnostic IgE antibody assays as well as molecular and cellular studies to investigate the immunological mechanisms of peanut allergy.

Blockade of peanut allergy with a novel Ara h 2-Fcγ fusion protein in mice

BACKGROUND

Conventional immunotherapy for peanut allergy using crude peanut extracts is not recommended because of the unacceptably high risk of anaphylaxis. Allergen-specific immunotherapy is not currently undertaken for peanut allergy.

OBJECTIVES

The objective of this study was to develop a novel peanut-human fusion protein to block peanut-induced anaphylaxis.

METHODS

We genetically designed and expressed a novel plant-human fusion protein composed of the major peanut allergen Ara h 2 and human IgG Fcγ1. We tested the Ara h 2-Fcγ fusion protein (AHG2)'s function in purified human basophils. Transgenic mice expressing human FcεRIα and a murine peanut allergy model were used.

RESULTS

AHG2 inhibited histamine release induced by whole peanut extract (WPE) from basophils of patients with peanut allergy, whereas the fusion protein itself did not induce mediator release. AHG2 inhibited the WPE-induced, peanut-specific, IgE-mediated passive cutaneous anaphylaxis in hFcεRIα transgenic mice. AHG2 also significantly inhibited acute anaphylactic reactivity, including the prototypical decrease in body temperature in WPE-sensitized mice challenged with crude peanut extract. Histologic evaluation of the airways showed that AHG2 decreased peanut-induced inflammation, whereas the fusion protein itself did not induce airway inflammation in peanut-sensitized mice. AHG2 did not exert an inhibitory effect in mice lacking FcγRII.

CONCLUSION

AHG2 inhibited peanut-specific IgE-mediated allergic reactions in vitro and in vivo. Linking specific peanut allergen to Fcγ can provide a new approach for the allergen immunotherapy of peanut allergy.

Dietary medium-chain triglycerides promote oral allergic sensitization and orally induced anaphylaxis to peanut protein in mice

BACKGROUND

The prevalence of peanut allergies is increasing. Peanuts and many other allergen sources contain significant amounts of triglycerides, which affect absorption of antigens but have unknown effects on sensitization and anaphylaxis. We recently reported that dietary medium-chain triglycerides (MCTs), which bypass mesenteric lymph and directly enter portal blood, reduce intestinal antigen absorption into blood compared with long-chain triglycerides (LCTs), which stimulate mesenteric lymph flow and are absorbed in chylomicrons through mesenteric lymph.

OBJECTIVE

We sought to test how dietary MCTs affect food allergy.

METHODS

C3H/HeJ mice were fed peanut butter protein in MCT, LCT (peanut oil), or LCT plus an inhibitor of chylomicron formation (Pluronic L81). Peanut-specific antibodies in plasma, responses of the mice to antigen challenges, and intestinal epithelial cytokine expression were subsequently measured.

RESULTS

MCT suppressed antigen absorption into blood but stimulated absorption into Peyer patches. A single gavage of peanut protein with MCT, as well as prolonged feeding in MCT-based diets, caused spontaneous allergic sensitization. MCT-sensitized mice experienced IgG-dependent anaphylaxis on systemic challenge and IgE-dependent anaphylaxis on oral challenge. MCT feeding stimulated jejunal-epithelial thymic stromal lymphopoietin, Il25, and Il33 expression compared with that seen after LCT feeding and promoted T(H)2 cytokine responses in splenocytes. Moreover, oral challenges of sensitized mice with antigen in MCT significantly aggravated anaphylaxis compared with challenges with the LCT. Importantly, the effects of MCTs could be mimicked by adding Pluronic L81 to LCTs, and in vitro assays indicated that chylomicrons prevent basophil activation.

CONCLUSION

Dietary MCTs promote allergic sensitization and anaphylaxis by affecting antigen absorption and availability and by stimulating T(H)2 responses.

Differential immuno-kinetic assays of allergen-specific binding for peanut allergy serum analysis

A label-free nanoparticle array platform has been used to detect total peanut allergen-specific binding from whole serum of patients suffering from peanut allergy. The serum from 10 patients was screened against a four-allergen panel of cat and dog dander, dust mite and peanut allergen protein Ara h1. The IgE and IgG contributions to the total specific-binding protein load to Ara h1 were identified using two secondary IgG- and IgE-specific antibodies and were found to contribute less than 50 % of the total specific protein load. The total mass of IgE, IgE and the unresolved specific-binding protein ΔsBP for Ara h1 provides a new serum profile for high-RAST-grade patients 5 and 6 with the IgG/IgE ratio of 4 ± 2 and ΔsBP/IgE ratio of 17 ± 11, neither of which is protective for the small patient cohort.

Identification of a new IgE-binding epitope of peanut oleosin that cross-reacts with buckwheat

Peanut and buckwheat induce a severe allergic reaction, anaphylaxis, which is considered to be mediated by immunoglobulin E (IgE). We identified in this study a new IgE-binding epitope of the peanut allergen that cross-reacted with buckwheat. The phosphate-buffered saline-soluble fraction of buckwheat inhibited the binding between IgE and the peanut allergen. A cross-reactive peptide was isolated from the α-chymotrypsin hydrolysate of peanut. Based on the amino acid sequence and mass spectrometric analysis data, the peptide was identified as Ser-Asp-Gln-Thr-Arg-Thr-Gly-Tyr (SDQTRTGY); this sequence is identical to amino acids 2-9 in the N-terminal hydrophilic domain of oleosin 3 which is located on the surface of the lipid storage body. Synthetic SDQTRTGY was found to bind with IgE in the sera of all eight peanut-allergic patients tested. Since many foods of plant origin contain oleosin, the possibility of an anaphylactic cross-reaction in allergic patients should always be considered.

Heating Affects Structure, Enterocyte Adsorption and Signalling, As Well as Immunogenicity of the Peanut Allergen Ara h 2

Previous studies have indicated that specific molecular properties of proteins may determine their allergenicity. Allergen interaction with epithelia as the first contact site could be decisive for a resulting immune response. We investigate here for the major peanut allergen Ara h 2 whether thermal processing results in structural changes which may impact the protein's molecular interactions with enterocytes, subsequent cellular signalling response, and immunogenicity.Ara h 2 was heat processed and analyzed in terms of patient IgE binding, structural alterations, interaction with human enterocytes and associated signalling as well as immunogenicity in a food allergy mouse model.Heating of Ara h 2 led to significantly enhanced binding to Caco-2/TC7 human intestinal epithelial cells. Structural analyses indicated that heating caused persistent structural changes and led to the formation of Ara h 2 oligomers in solution. Heated protein exhibited a significantly higher immunogenic potential in vivo as determined by IgG and IgE serum antibody levels as well as IL-2 and IL-6 release by splenocytes. In human Caco-2/TC7 cells, Ara h 2 incubation led to a response in immune- and stress signalling related pathway components at the RNA level, whereas heated allergen induced a stress-response only.We suggest from this peanut allergen example that food processing may change the molecular immunogenicity and modulate the interaction capacity of food allergens with the intestinal epithelium. Increased binding behaviour to enterocytes and initiation of signalling pathways could trigger the epimmunome and influence the sensitization capacity of food proteins.