Clinical study of peanut and nut allergy in 62 consecutive patients: new features and associations.

OBJECTIVE--To investigate clinical features of acute allergic reactions to peanuts and other nuts. DESIGN--Analysis of data from consecutive patients seen by one doctor over one year in an allergy clinic at a regional referral centre. SUBJECTS--62 patients aged 11 months to 53 years seen between October 1993 and September 1994. MAIN OUTCOME MEASURES--Type and severity of allergic reactions, age at onset of symptoms, type of nut causing allergy, results of skin prick tests, and incidence of other allergic diseases and associated allergies. RESULTS--Peanuts were the commonest cause of allergy (47) followed by Brazil nut (18), almond (14), and hazelnut (13). Onset of allergic symptoms occurred by the age of 2 years in 33/60 and by the age of 7 in 55/60. Peanuts accounted for all allergies in children sensitised in the first year of life and for 82% (27/33) of allergies in children sensitised by the third year of life. Multiple allergies appeared progressively with age. The commonest symptom was facial angioedema, and the major feature accounting for life threatening reactions was laryngeal oedema. Hypotension was uncommon. Of 55 patients, 53 were atopic--that is, had positive skin results of tests to common inhaled allergens--and all 53 had other allergic disorders (asthma, rhinitis, eczema) due to several inhaled allergens and other foods. CONCLUSIONS--Sensitisation, mainly to peanuts, is occurring in very young children, and multiple peanut/nut allergies appear progressively. Peanut and nut allergy is becoming common and can cause life threatening reactions. The main danger is laryngeal oedema. Young atopic children should avoid peanuts and nuts to prevent the development of this allergy.     

Peanut allergy in relation to heredity,maternal diet,and other atopic diseases: results of a questionnaire survey,skin prick testing,and food challenges.

OBJECTIVES: To determine rates of other atopic manifestations in people with peanut allergy and the prevalence of such allergy in their families. DESIGN: A survey of people with self reported peanut allergy and people referred by their general practitioner for suspected peanut allergy; survey and skin testing of 50 children with reported peanut allergy and their available first degree relatives. SUBJECTS: 622 adults and children with reported, suspected, or known peanut allergy. MAIN OUTCOME MEASURES: Prevalence of peanut allergy and other allergies in the families of people with peanut allergy. RESULTS: 622 valid completed questionnaires were returned out of the 833 questionnaires dispatched (74.7%). All forms of atopy were both more common in successive generations (P < 0.0001) and more common in maternal than paternal relatives (P < 0.0001). Peanut allergy was reported by 0.1% (3/2409) of grandparents, 0.6% (7/1213) of aunts and uncles, 1.6% (19/1218) of parents, and 6.9% (42/610) of siblings. Consumption of peanuts while pregnant or breast feeding was more common among mothers of probands aged < or = 5 years than mothers of probands aged > 5 years (P < 0.001). Age of onset correlated inversely with year of birth (r = -0.6, P < 0.001). Skin prick testing of 50 children with reported peanut allergy and their families: 7 probands (14%) had a negative result for peanut. Peanut allergy was refuted by food challenge in all those tested (5/7). No parent and 13% (5/39) of siblings had a positive result on skin prick testing for peanut. Two of these siblings had negative challenge with peanuts. The prevalence of peanut allergy in siblings is therefore 3/39 (7%). CONCLUSIONS: Peanut allergy is more common in siblings of people with peanut allergy than in the parents or the general population. Its apparently increasing prevalence may reflect a general increase of atopy, which is inherited more commonly from the mother. Peanut allergy is presenting earlier in life, possibly reflecting increased consumption of peanut by pregnant and nursing mothers.     

Randomised,double blind,crossover challenge study of allergenicity of peanut oils in subjects allergic to peanuts.

OBJECTIVE: To determine the in vivo allergenicity of two grades of peanut oil for a large group of subjects with proved allergy to peanuts. DESIGN: Double blind, crossover food challenge with crude peanut oil and refined peanut oil. SETTING: Dedicated clinical investigation unit in a university hospital. SUBJECTS: 60 subjects allergic to peanuts; allergy was confirmed by challenge tests. OUTCOME MEASURES: Allergic reaction to the tested peanut oils. RESULTS: None of the 60 subjects reacted to the refined oil; six (10%) reacted to the crude oil. Supervised peanut challenge caused considerably less severe reactions than subjects had reported previously. CONCLUSIONS: Crude peanut oil caused allergic reactions in 10% of allergic subjects studied and should continue to be avoided. Refined peanut oil did not pose a risk to any of the subjects. It would be reasonable to recommend a change in labelling to distinguish refined from crude peanut oil.     

Focus: Allergic Diseases and Type II Immunity: Development of New White Fish Allergy after Bone Marrow Transplantation from a Non-atopic Donor

Background: Transplant-acquired food allergy has become increasingly recognized in solid organ and bone marrow transplantation. As food allergy has no cure and causes considerable impact on the lives of patients who require strict avoidance of foods to avoid potentially severe or fatal reactions, it is crucial for physicians to better understand the risk factors and mechanisms driving development of food allergy post-transplant. We report a case of new food allergy to whitefish in an elderly patient post-bone marrow transplant in which neither donor nor recipient had a history of atopy. Methods: A 70-year-old man experienced an anaphylactic reaction to Swai whitefish (Pangasius hypophthalmus) 6 months post-transplant that he had previously tolerated on multiple occasions both pre-transplant and in the preceding months post-transplant. This allergy was investigated by commercial serum specific IgE testing and fresh prick-to-prick skin test to Swai whitefish. Results: Fresh prick-to-prick demonstrated large positive reaction to the Swai whitefish with wheal of 10 mm and flare of 22 mm compared to positive histamine control with a wheal/flare of 5x8mm. Serum specific IgE testing to commercial whitefish was negative (specific IgE <0.10kU/L). The patient continues to strictly avoid Swai whitefish but tolerates all other fish and shellfish. Conclusions: The unique development of specific Swai whitefish allergy in an elderly man after bone marrow transplant where both donor and recipient had no prior history of atopy strongly supports transplant-related immunomodulation as a major mechanism for transplant-acquired allergy and suggests that that absence of atopy or advanced age may not necessarily be protective.     

High frequency of IgE sensitization towards kiwi seed storage proteins among peanut allergic individuals also reporting allergy to kiwi

Background

IgE sensitization to storage proteins from nuts and seed is often related to severe allergic symptoms. There is a risk of immunological IgE cross-reactivity between storage proteins from different species. The potential clinical implication of such cross-reactivity is that allergens other than the known sensitizer can cause allergic symptoms. Previous studies have suggested that kiwi seed storage proteins may constitute hidden food allergens causing cross-reactive IgE-binding with peanut and other tree nut homologs, thereby mediating a potential risk of causing allergy symptoms among peanut ant tree nut allergic individuals. The objective of this study was to investigate the degree of sensitization towards kiwi fruit seed storage proteins in a cohort of peanut allergic individuals.

Methods

A cohort of 59 adolescents and adults with peanut allergy was studied, and self reported allergies to a number of additional foods were collected. Quantitative IgE measurements to seed storage proteins from kiwi and peanut were performed.

Results

In the cohort, 23 out of the 59 individuals were reporting kiwi fruit allergy (39%). The frequency of IgE sensitization to kiwi fruit and to any kiwi seed storage protein was higher among peanut allergic individuals also reporting kiwi fruit allergy (P = 0.0001 and P = 0.01). A positive relationship was found between IgE levels to 11S globulin (r = 0.65) and 7S globulin (r = 0.48) allergens from kiwi and peanut, but IgE levels to 2S albumin homologs did not correlate. Patients reporting kiwi fruit allergy also reported allergy to hazelnut (P = 0.015), soy (P < 0.0001), pea (P = 0.0002) and almond (P = 0.016) to a higher extent than peanut allergic individuals without kiwi allergy.

Conclusions

Thirty-nine percent of the peanut allergic patients in this cohort also reported kiwi fruit allergy, they displayed a higher degree of sensitization to kiwi storage proteins from both kiwi and peanut, and they also reported a higher extent of allergy to other nuts and legumes. On the molecular level, there was a correlation between IgE levels to 11S and 7S storage proteins from kiwi and peanut. Taken together, reported symptoms and serological findings to kiwi in this cohort of patients with concurrent allergy to peanut and kiwi fruit, could be explained by a combination of cross-reactivity between the 11S and 7S globulins and co-sensitization to the 2S albumin Act d 13.

     

Measles immunisation in children with allergy to egg.

OBJECTIVE--To examine the occurrence of adverse reactions to measles vaccine given as a single dose to children with egg allergy, and to determine if the administration of single dose to children with a positive result in an intradermal skin prick test with the vaccine is associated with adverse reactions. DESIGN--Review of results of immunisation and prospective study of 96 consecutively presenting children given intradermal skin testing with the vaccine. SETTING--Children''s allergy centre. SUBJECTS--410 children sensitive to egg referred to the allergy unit for advice about measles immunisation. MAIN OUTCOME MEASURES--Nature and severity of reactions associated with the administration of measles vaccine. RESULTS--All children had a positive result in a skin prick test with egg white, and five had a positive result in a skin prick test with vaccine. Of 96 consecutive children, 46 had a positive result in an intradermal test with vaccine. After immunisation with a full dose (0.5 ml) of vaccine adverse reactions were associated with a mild reaction in four children, none of whom required treatment. Only one of the 46 children with a positive result in an intradermal vaccine skin test had a reaction associated with vaccine administration. None of the children with a positive result in a skin prick test with measles vaccine reacted to the vaccine. The rate of minor reactions to the vaccine not requiring treatment was 0.98% (95% confidence interval 0.27% to 2.48%) and serious reactions requiring treatment was 0% (0% to 0.9%). CONCLUSION--Children with IgE mediated allergic reactions to egg protein should be investigated and managed by practitioners with special knowledge in this subject. Measles immunisation should be performed in a setting where any adverse reactions can be dealt with appropriately. Skin tests and measles vaccine and desensitisation are not necessary.     

Immunotherapy using algal‐produced Ara h 1 core domain suppresses peanut allergy in mice

Peanut allergy is an IgE‐mediated adverse reaction to a subset of proteins found in peanuts. Immunotherapy aims to desensitize allergic patients through repeated and escalating exposures for several months to years using extracts or flours. The complex mix of proteins and variability between preparations complicates immunotherapy studies. Moreover, peanut immunotherapy is associated with frequent negative side effects and patients are often at risk of allergic reactions once immunotherapy is discontinued. Allergen‐specific approaches using recombinant proteins are an attractive alternative because they allow more precise dosing and the opportunity to engineer proteins with improved safety profiles. We tested whether Ara h 1 and Ara h 2, two major peanut allergens, could be produced using chloroplast of the unicellular eukaryotic alga, Chlamydomonas reinhardtii. C. reinhardtii is novel host for producing allergens that is genetically tractable, inexpensive and easy to grow, and is able to produce more complex proteins than bacterial hosts. Compared to the native proteins, algal‐produced Ara h 1 core domain and Ara h 2 have a reduced affinity for IgE from peanut‐allergic patients. We further found that immunotherapy using algal‐produced Ara h 1 core domain confers protection from peanut‐induced anaphylaxis in a murine model of peanut allergy.     

Prevalence of positive atopy patch test in an unselected pediatric population

Background

In the latest decades, epidemiological studies on allergic disorders in children, including atopic dermatitis, rhinitis and asthma, demonstrated a continuous increase in prevalence. However, such studies are usually performed by questionnaires and, sometimes, by skin prick test or in vitro IgE tests, while the portion of allergy sustained by the cell-mediated mechanism is neglected, because the essential test, i.e. the atopy patch test is not performed.

Methods

This cross-sectional survey studied by a specific questionnaire, skin prick test and atopy patch test, an unselected population, represented by the entire scholastic population attending a Primary school and a Junior Secondary school in the rural town of San Marco in Lamis, 12.000 inhabitants (Puglia, Italy).

Results

Among the 456 subjects included, 78 (17.1 %) had a positive skin prick test and 57 (12.5 %) had a positive atopy patch test. In particular, 13.4 % of subjects were positive only to skin prick test and 8.8 % were positive only to atopy patch test. The allergen most frequently positive was the house dust mite, with 41 positive results to skin prick test and 55 to atopy patch test, while for pollen positive results concerned almost exclusively the skin prick test.

Conclusions

This survey on an unselected population of children detected a prevalence of positive results to atopy patch test not so distant from the positive results to skin prick test, and in 8.8 % of subjects the atopy patch test was the only positive test. This would suggest to add the atopy patch test in future epidemiological studies on allergy, in order to avoid to overlook the not negligible portion of patients with T-cell-mediated allergy.     

Induction of Allergic Responses to Peanut Allergen in Sheep

Peanut allergy is the leading cause of deaths due to food-induced anaphylaxis but despite continued research, there are currently no specific treatments available. Challenge testing is limited in patients due to the high risk of adverse reactions, emphasising the need for an appropriate animal model. In the present study we examine the induction of allergic responses in a sheep model for peanut allergy. Sheep were sensitised with peanut (PN) extract and in separate injections with ovalbumin (OVA) or house dust mite (HDM) extract. Serum PN-specific IgE responses were detected in 40–50% of immunised sheep, while only 10% (1 of 10 sheep) showed detectable OVA-specific IgE. All PN-allergic sheep tested showed an Ara h 1-specific IgE response, while four out of five allergic sheep showed an Ara h 2-specific IgE response. Animals with high serum IgE levels to HDM were also PN IgE-positive. Of the PN-sensitised animals with high PN-specific IgE, 80% also showed an immediate hypersensitivity reaction following an intradermal PN injection. This new large animal model of peanut allergy may provide a useful tool for future investigations of allergen-associated immune mechanisms and specific immunotherapy.     

Birch pollen-associated peanut allergies in children

Panallergens show structural similarities, and they are responsible for many cross-reactions between pollen and plant food sources. The aim of the present study was to investigate IgE reactivity to peanut allergen components in children with birch pollen allergy. Patients experienced symptoms of allergic asthma, allergic rhinitis, and urticaria, and they underwent a complete diagnostic evaluation, including skin prick test (SPT), specific IgE (sIgE) to birch pollen allergen (t3), peanut allergen (f13). In addition, measurement of sIgE to the major birch allergen components, Betula verrucosa (Bet v1, Bet v2), and to peanut allergen components, Arachis hypogaea (genuine componens: Ara h1, Ara h2, Ara h3, and cross-reactive Ara h8) was performed, by using a microarray technique (component resolved diagnosis, CRD). SPT to birch extract was positive in all children, and SPT to peanut extract was positive in 51 % of them. sIgE to both allergens was increased in 39 % of children, 55 % of them had increased sIgE (t3), and one child had increased sIgE (f13). CRD results confirmed that some children were sensitized to Bet v1 only, and some children to genuine Ara h only. Bet v1/Ara h8 cross-reactivity was found in 16 % of children. Results of the present study reveal that SPT, sIgE, and CRD may detect sensitization and co-sensitization with birch and peanut allergens/allergen components, and CRD may help to differentiate sensitization to genuine peanut components from sensitization to peanut cross-reactive component in birch-sensitive children. Diagnostic approach has to be individualized for each patient.     

The peanut allergy epidemic: allergen molecular characterisation and prospects for specific therapy

Peanut (Arachis hypogaea) allergy is a major cause of food-induced anaphylaxis, with increasing prevalence worldwide. To date, there is no cure for peanut allergy, and, unlike many other food allergies, it usually persists through to adulthood. Prevention of exposure to peanuts is managed through strict avoidance, which can be compromised by the frequent use of peanuts and peanut products in food preparations. Conventional subcutaneous-injection allergen immunotherapy using crude peanut extract is not a recommended treatment because of the risk of severe side effects, largely as a result of specific IgE antibodies. Consequently, there is an urgent need to develop a suitable peanut allergen preparation that can induce specific clinical and immunological tolerance to peanuts in allergic individuals without adverse side effects. This requires detailed molecular and immunological characterisation of the allergenic components of peanut. This article reviews current knowledge on clinically relevant peanut allergens, in particular Ara h 1, Ara h 2 and Ara h 3, together with options for T-cell-reactive but non-IgE-binding allergen variants for specific immunotherapeutic strategies. These include T-cell-epitope peptide and hypoallergenic mutant vaccines. Alternative routes of administration such as sublingual are also considered, and appropriate adjuvants for delivering effective treatments at these sites examined.     

Determinants of Allergic Rhinitis in Young Children with Asthma

Background

In the preschool period, allergic rhinitis (AR) is infrequent and thus under-diagnosed. However, recent works have highlighted the occurrence of AR in toddlers although the causes of AR in this young population remain unknown. The objective of this study was to identify determinants of AR in young children with asthma.

Methods

We carried out a case-control study of 227 children with active asthma and enrolled in the Trousseau Asthma Program. AR and other allergic diseases (asthma, food allergy and eczema) were diagnosed by medical doctors using standardized questionnaires. Parental history of AR and asthma, biological markers of atopy (total IgE, blood eosinophilia, allergic sensitization towards food and aeroallergens) and environmental parameters were also collected.

Results

Forty one of the children (18.1%) had AR. By univariate logistic regression analysis, AR was mainly associated with peanut sensitization (OR = 6.75; p = 0.002); food allergy (OR = 4.31; p = 0.026); mold exposure (OR = 3.81 p<0.01) and parental history of AR (OR = 1.42; p = 0.046). Due to the strong link between food allergy and peanut sensitization three models of multivariate logistic regression were performed and confirmed that AR is associated with peanut sensitization but also food allergy and mold exposure. A random forest analysis was also performed to explain AR. The results reinforced the logistic analysis that peanut sensitization and mold exposure were the principal determinants of AR.

Conclusions & Clinical Relevance

These results stress the importance of investigating AR in young children with asthma to potentially diagnose a particularly severe allergic asthmatic phenotype. Moreover, these data evoke the hypothesis that peanut could be an aeroallergen.     

Evaluation of basophil allergen threshold sensitivity (CD-sens) to peanut and Ara h 8 in children IgE-sensitized to Ara h 8

Background

Diagnosing peanut allergy properly is important and can be achieved by combining clinical history with various diagnostic methods such as IgE-antibody (IgE-ab) measurements, skin-prick test, basophil allergen threshold sensitivity (CD-sens) and food challenge. We aimed to evaluate CD-sens to peanut, Ara h 8 and Gly m 4 in relation to an oral peanut challenge in children IgE-sensitized to birch, peanut and Ara h 8 avoiding peanuts.

Methods

Twenty children IgE-sensitized to birch pollen and Ara h 8, but not to Ara h 1, Ara h 2 or Ara h 3 were challenged orally with roasted peanuts. Blood samples were drawn for IgE-ab and CD-sens analysis. To measure CD-sens, basophils were stimulated in vitro with decreasing doses of allergens until threshold sensitivity was reached.

Results

All children passed challenge without objective symptoms, but mild oral allergy syndrome (OAS) symptoms were reported in 6/20 children. Nineteen of twenty children were negative in CD-sens to peanut but 17/20 were positive to rAra h 8. Eleven of twenty children were positive in CD-sens to rGly m 4.

Conclusion

Positive CD-sens to rAra h 8 show that the Ara h 8 IgE-ab sensitized basophils can be activated by a rAra h 8 allergen and initiate an allergic inflammation despite a negative challenge. Hence, children sensitized to Ara h 8 but not to peanut storage proteins may be at risk for systemic allergic reaction when eating larger amounts of peanuts but most likely don’t have to fear smaller amounts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12948-014-0007-3) contains supplementary material, which is available to authorized users.     

Structure and Function of the Peanut Panallergen Ara h 8

The incidence of peanut allergy continues to rise in the United States and Europe. Whereas exposure to the major allergens Ara h 1, 2, 3, and 6 can cause fatal anaphylaxis, exposure to the minor allergens usually does not. Ara h 8 is a minor allergen. Importantly, it is the minor food allergens that are thought to be responsible for oral allergy syndrome (OAS), in which sensitization to airborne allergens causes a Type 2 allergic reaction to ingested foods. Furthermore, it is believed that similar protein structure rather than a similar linear sequence is the cause of OAS. Bet v 1 from birch pollen is a common sensitizing agent, and OAS results when patients consume certain fruits, vegetables, tree nuts, and peanuts. Here, we report the three-dimensional structure of Ara h 8, a Bet v 1 homolog. The overall fold is very similar to that of Bet v 1, Api g 1 (celery), Gly m 4 (soy), and Pru av 1 (cherry). Ara h 8 binds the isoflavones quercetin and apigenin as well as resveratrol avidly.     

Tree Nuts Are Inversely Associated with Metabolic Syndrome and Obesity: The Adventist Health Study-2

Objective

To examine the relationships of nut consumption, metabolic syndrome (MetS), and obesity in the Adventist Health Study-2, a relatively healthy population with a wide range of nut intake.

Research Design and Methods

Cross-sectional analysis was conducted on clinical, dietary, anthropometric, and demographic data of 803 adults. MetS was defined according to the American Heart Association and the National Heart, Lung, and Blood Institute diagnostic criteria. We assessed intake of total nuts, tree nuts and peanuts, and also classified subjects into low tree nut/low peanut (LT/LP), low tree/high peanut (LT/HP), high tree nut/high peanut (HT/HP), and high tree/low peanut (HT/LP) consumers. Odds ratios were estimated using multivariable logistic regression.

Results

32% of subjects had MetS. Compared to LT/LP consumers, obesity was lower in LT/HP (OR = 0.89; 95% CI = 0.53, 1.48), HT/HP (OR = 0.63; 95% CI = 0.40, 0.99) and HT/LP (OR = 0.54; 95% CI = 0.34, 0.88) consumers, p for trend = 0.006. For MetS, odds ratios (95% CI) were 0.77 (0.47, 1.28), 0.65 (0.42, 1.00) and 0.68 (0.43, 1.07), respectively (p for trend = 0.056). Frequency of nut intake (once/week) had significant inverse associations with MetS (3% less for tree nuts and 2% less for total nuts) and obesity (7% less for tree nuts and 3% less for total nuts).

Conclusions

Tree nuts appear to have strong inverse association with obesity, and favorable though weaker association with MetS independent of demographic, lifestyle and dietary factors.     

Alleviating peanut allergy using genetic engineering: the silencing of the immunodominant allergen Ara h 2 leads to its significant reduction and a decrease in peanut allergenicity

Peanut allergy is one of the most life-threatening food allergies and one of the serious challenges facing the peanut and food industries. Current proposed solutions focus primarily on ways to alter the immune system of patients allergic to peanut. However, with the advent of genetic engineering novel strategies can be proposed to solve the problem of peanut allergy from the source. The objectives of this study were to eliminate the immunodominant Ara h 2 protein from transgenic peanut using RNA interference (RNAi), and to evaluate the allergenicity of resulting transgenic peanut seeds. A 265-bp-long PCR product was generated from the coding region of Ara h 2 genomic DNA, and cloned as inverted repeats in pHANNIBAL, an RNAi-inducing plant transformation vector. The Ara h 2-specific RNAi transformation cassette was subcloned into a binary pART27 vector to construct plasmid pDK28. Transgenic peanuts were produced by infecting peanut hypocotyl explants with Agrobacterium tumefaciens EHA 105 harbouring the pDK28 construct. A total of 59 kanamycin-resistant peanut plants were regenerated with phenotype and growth rates comparable to wild type. PCR and Southern analyses revealed that 44% of plants stably integrated the transgene. Sandwich ELISA performed using Ara h 2-mAbs revealed a significant ( P <  0.05) reduction in Ara h 2 content in several transgenic seeds. Western immunobloting performed with Ara h 2-mAb corroborated the results obtained with ELISA and showed absence of the Ara h 2 protein from crude extracts of several transgenic seeds of the T₀ plants. The allergenicity of transgenic peanut seeds expressed as IgE binding capacity was evaluated by ELISA using sera of patients allergic to peanut. The data showed a significant decrease in the IgE binding capacity of selected transgenic seeds compared to wild type, hence, demonstrating the feasibility of alleviating peanut allergy using the RNAi technology.     

The usefulness of casein-specific IgE and IgG4 antibodies in cow's milk allergic children

Background

Cow's milk allergy is one of the most common food allergies among younger children. We investigated IgE antibodies to milk, and IgE and IgG4 antibodies to casein, ??-lactalbumin and ??-lactoglobulin in cow's milk allergic (CMA) and non-allergic (non-CMA) children in order to study their clinical usefulness.

Methods

Eighty-three children with suspected milk allergy (median age: 3.5 years, range: 0.8-15.8 years) were diagnosed as CMA (n = 61) or non-CMA (n = 22) based on an open milk challenge or convincing clinical history. Their serum concentrations of allergen-specific (s) IgE and IgG4 antibodies were measured using ImmunoCAP^?. For the sIgG4 analysis, 28 atopic and 31 non-atopic control children were additionally included (all non-milk sensitized).

Results

The CMA group had significantly higher levels of milk-, casein- and ??-lactoglobulin-sIgE antibodies as compared to the non-CMA group. The casein test showed the best discriminating performance with a clinical decision point of 6.6 kU_A/L corresponding to 100% specificity. All but one of the CMA children aged > 5 years had casein-sIgE levels > 6.6 kU_A/L. The non-CMA group had significantly higher sIgG4 levels against all three milk allergens compared to the CMA group. This was most pronounced for casein-sIgG4 in non-CMA children without history of previous milk allergy. These children had significantly higher casein-sIgG4 levels compared to any other group, including the non-milk sensitized control children.

Conclusions

High levels of casein-sIgE antibodies are strongly associated with milk allergy in children and might be associated with prolonged allergy. Elevated casein-sIgG4 levels in milk-sensitized individuals on normal diet indicate a modified Th2 response. However, the protective role of IgG4 antibodies in milk allergy is unclear.     

Structural and immunologic characterization of Ara h 1, a major peanut allergen

Allergic reactions to peanuts and tree nuts are major causes of anaphylaxis in the United States. We compare different properties of natural and recombinant versions of Ara h 1, a major peanut allergen, through structural, immunologic, and bioinformatics analyses. Small angle x-ray scattering studies show that natural Ara h 1 forms higher molecular weight aggregates in solution. In contrast, the full-length recombinant protein is partially unfolded and exists as a monomer. The crystal structure of the Ara h 1 core (residues 170-586) shows that the central part of the allergen has a bicupin fold, which is in agreement with our bioinformatics analysis. In its crystalline state, the core region of Ara h 1 forms trimeric assemblies, while in solution the protein exists as higher molecular weight assemblies. This finding reveals that the residues forming the core region of the protein are sufficient for formation of Ara h 1 trimers and higher order oligomers. Natural and recombinant variants of proteins tested in in vitro gastric and duodenal digestion assays show that the natural protein is the most stable form, followed by the recombinant Ara h 1 core fragment and the full-length recombinant protein. Additionally, IgE binding studies reveal that the natural and recombinant allergens have different patterns of interaction with IgE antibodies. The molecular basis of cross-reactivity between vicilin allergens is also elucidated.     

Assessment of the Sensitizing Potential of Processed Peanut Proteins in Brown Norway Rats: Roasting Does Not Enhance Allergenicity

Background

IgE-binding of process-modified foods or proteins is the most common method for examination of how food processing affects allergenicity of food allergens. How processing affects sensitization capacity is generally studied by administration of purified food proteins or food extracts and not allergens present in their natural food matrix.

Objectives

The aim was to investigate if thermal processing increases sensitization potential of whole peanuts via the oral route. In parallel, the effect of heating on sensitization potential of the major peanut allergen Ara h 1 was assessed via the intraperitoneal route.

Methods

Sensitization potential of processed peanut products and Ara h 1 was examined in Brown Norway (BN) rats by oral administration of blanched or oil-roasted peanuts or peanut butter or by intraperitoneal immunization of purified native (N-), heated (H-) or heat glycated (G-)Ara h 1. Levels of specific IgG and IgE were determined by ELISA and IgE functionality was examined by rat basophilic leukemia (RBL) cell assay.

Results

In rats dosed orally, roasted peanuts induced significant higher levels of specific IgE to NAra h 1 and 2 than blanched peanuts or peanut butter but with the lowest level of RBL degranulation. However, extract from roasted peanuts was found to be a superior elicitor of RBL degranulation. Process-modified Ara h 1 had similar sensitizing capacity as NAra h 1 but specific IgE reacted more readily with process-modified Ara h 1 than with native.

Conclusions

Peanut products induce functional specific IgE when dosed orally to BN rats. Roasted peanuts do not have a higher sensitizing capacity than blanched peanuts. In spite of this, extract from roasted peanuts is a superior elicitor of RBL cell degranulation irrespectively of the peanut product used for sensitization. The results also suggest that new epitopes are formed or disclosed by heating Ara h 1 without glucose.