The Severity and Frequency of Systemic Reactions to Hazelnut Are Significantly Higher in Hazelnut Allergic Patients Monosensitized to Cor a 8 than in Patients Polysensitized to Cor a 1, Cor a 8, and Cor a 9.

INTRODUCTION: Hazelnuts are a leading trigger of food allergy. To date, several molecular components of hazelnut are available for component-resolved diagnosis. However, little is known about how simultaneous sensitization to multiple allergens affects the severity of the hazelnut-induced reaction. In a previous study, our group demonstrated a lower risk of systemic reactions to peach in patients sensitized to both Pru p 3 and Pru p 1 than in the patient monosensitized to peach LTP. We aimed to assess whether this was also true in hazelnut allergy in a cohort of adult patients. METHODS: Patients were selected based on a history of symptoms such as urticaria, vomiting, diarrhea, asthma, and anaphylaxis indicative of hazelnut IgE-mediated food allergy and graded according to a clinical severity scale. For all patients, specific IgE was determined for Cor a 1 and Cor a 8 and, for most patients, also Cor a 9. Patients were offered an oral food challenge in open format (OFC) with a cocoa-based roasted hazelnut spread on a voluntary basis in order to prescribe an appropriate diet. RESULTS: A total of two hundred and fourteen patients were recruited. Among these, 43 patients were monosensitized to Cor a 8. One hundred and seventy-one patients were sensitized to Cor a 1 (79.9%), and, among them, 48/171 (28.1%) were also Cor a 8 positive. Cor a 9 was evaluated in 124/214 patients, testing positive in 21/124 (16.9%). Patients monosensitized to Cor a 8 experienced systemic reactions more frequently than those sensitized to Cor a 1 ± Cor a 8 (p < 0.00001), with significantly more severe reactions (p < 0.0005) and testing more frequently positive at OFC (p < 0.0001). Regarding Cor a 9, the sensitized patients were significantly younger (p = 0.0013) and showed reactions of similar severity to patients who tested Cor a 9 negative, and these reactions were milder than in patients monosensitized only to Cor a 8. DISCUSSION/CONCLUSION: Sensitization to Cor a 1 seems to protect from the development of the severe systemic reactions induced by Cor a 8 sensitization, Cor a 9 does not influence the severity of symptoms in adult patients. The OFC with roasted hazelnut may help in dietary guidance.

Tolerance of peanuts and tree nuts in Spanish children with exclusive sensitization to lipid transfer proteins.

BACKGROUND: Allergy to peanuts and tree nuts is a common cause of food allergy in Spain, with lipid transfer proteins (LTP) being the most frequently recognized panallergen. LTP sensitization often leads to multiple food group sensitivities, resulting in overly restrictive diets that hinder patient's quality of life. This study aimed to assess the tolerance of peanuts and tree nuts (hazelnuts and walnuts) in children sensitized to LTP, potentially mitigating the need for such diets. METHODS: This prospective study enrolled individuals diagnosed with allergy to peanuts, hazelnuts, or walnuts. Data were collected from medical records, including demographics and clinical history. Allergological assessment comprised skin prick tests using commercial extracts and the nuts in question, alongside measurements of total and specific IgE to nuts and their primary molecular components. Participants showing positive LTP sensitization without sensitization to seed storage proteins underwent open oral nut challenges. RESULTS: A total of 75 individuals labeled as allergic to peanuts, 44 to hazelnuts, and 51 to walnuts were included. All of them underwent an open oral provocation test with the incriminated nut, showing a high tolerance rate. Peanut was tolerated by 98.6% of patients, 97.72% tolerated hazelnut, and 84.3% tolerated walnut. CONCLUSION: The findings suggest that the majority of patients allergic to peanuts, hazelnuts, or walnuts, due to LTP sensitization and lacking IgE reactivity to seed storage proteins, can tolerate these nuts. This supports the need for personalized nut tolerance assessments to avoid unnecessary dietary restrictions.

Measurement of IgE to hazelnut allergen components cannot replace hazelnut challenge in Dutch adults.

BACKGROUND: Component-resolved diagnostics (CRD) help predict hazelnut allergy (HA) in children, but are of unknown diagnostic value in adults. This study aimed to evaluate the diagnostic accuracy of IgE to hazelnut extract and components in adults. METHODS: A Dutch population of consecutively presenting adults suspected of HA, who underwent a double-blind placebo-controlled food challenge, were included. Serum IgE to hazelnut extract and Cor a 1, 8, 9, and 14 was measured on ImmunoCAP. Diagnostic accuracy was assessed by area under the curve (AUC) analysis. RESULTS: Of 89 patients undergoing challenge, 46 had challenge-confirmed HA: 17 based on objective and 29 based on subjective symptoms. At commonly applied cutoffs 0.1 and 0.35 kUA /L, high sensitivity was observed for IgE to hazelnut extract and Cor a 1 (range 85-91%), and high specificity for IgE to Cor a 8, 9 and 14 (range 77-95%). However, the AUCs for hazelnut extract and components were too low for accurate prediction of HA (range 0.50-0.56). Combining hazelnut extract and component IgE measurements did not significantly improve accuracy. Higher IgE levels to Cor a 9 and 14 were tentatively associated with HA with objective symptoms, but the corresponding AUCs still only reached 0.68 and 0.63, respectively. CONCLUSIONS: Although hazelnut allergic adults are generally sensitized to hazelnut extract and Cor a 1, and hazelnut tolerant adults are usually not sensitized to Cor a 8, 9, or 14, challenge testing is still needed to accurately discriminate between presence and absence of HA in adults from a birch-endemic country.

Co-sensitization to the three non-homologous major cashew allergens Ana o 1, Ana o 2 and Ana o 3 is caused by IgE cross-reactivity.

BACKGROUND: Cashew nuts often cause strong allergic reactions, even exceeding those of peanuts. Ana o 1 (vicilin), Ana o 2 (legumin) and Ana o 3 (2S albumin) are major cashew allergens. Co-sensitization to all three non-homologous cashew nut allergens has been observed. We hypothesize that this might be due to IgE cross-reactivity. METHODS: IgE cross-inhibitions were performed with Ana o 1-3 using sera from cashew nut allergic patients. Related hazelnut allergens Cor a 11, 9 and 14 were used as controls. For comparison, IgE cross-reactivity between the hazelnut allergens was investigated using sera from hazelnut allergic patients. RESULTS: Median percentages of cross-inhibitions between Ana o 1-3 were 84-99%. In comparison, medians of cross-inhibitions between hazelnut allergens were 33-62%. The IC50 values revealed the highest IgE affinity to Ana o 3 and Cor a 14. Hazelnut legumin Cor a 9 inhibited IgE-binding to Ana o 1, 2, and 3 with median percentages of 75%, 56%, and 48%, respectively. No cross-reactivity was observed between allergenic vicilins or between 2S albumins from cashew and hazelnut. In silico identified potentially cross-reactive peptides of Ana o 3 overlapped with previously reported IgE epitopes of all three allergens. CONCLUSIONS: IgE with high affinity to Ana o 3 that cross-reacts with the other two major non-homologous cashew nut allergens might be responsible for the high allergenic potency of cashew nut. These cross-reactive IgE comprises the major fraction of specific IgE in cashew allergic patients, and might be responsible for cross-reactivity between unrelated tree nuts.

Multiplex component-based allergen macroarray test is useful to predict clinical reactivity to tree nuts in children.

BACKGROUND: In tree nut (TN) allergy, singleplex tests showed the diagnostic utility of rAna o 3, rCor a 14/nCor a 9, and nJug r 1/nJug r 4 for cashew/pistachio, hazelnut, and walnut allergies, respectively. However, disadvantages of the tests include high costs and excessive blood sampling in multi-sensitized patients, and a limited number of components. We investigated the utility of a multiplex macroarray (i.e., the ALEX2 test) in TN allergy. METHODS: In 169 children, skin prick test, the component- and extract-specific IgEs of TNs were investigated for clinical reactivity and tolerance. RESULTS: The predictors (AUC = 0.962-0.749) of clinical reactivity to cashew, pistachio, hazelnut, and walnut were rPis v 1/rAna o 3, rPis v 1/rAna o 3/nPis v 2/nPis v 3, rCor a 14/nCor a 11/nCor a 9, and nJug r 1/nJug r 2/nJug r 6/nJug r 4, respectively. More than 93% of the patients with clinical reactivity to pistachio/cashew, hazelnut and walnut had positivity of (≥0.3 kUA/L) rPis v 1/rAna o 3, rCor a 14 and nJug r 1/nJug r 2, respectively. The highest accuracies of clinical reactivity to culprit nut were obtained with combination of rPis v 1, sIgE and SPT positivities for cashew/pistachio, rPis v 1 ≥ 1.0 kUA/L for pistachio, rCor a 14 ≥ 1.0 kUA/L for hazelnut and combination of nJug r 1 and nJug r 2 positivities for walnut, respectively. Also, higher concentrations of rPis v 1 (≥15.0 kUA/L), rCor a 14 (≥5.0 kUA/L) and nJug r 1/nJug r 2 (≥15.0 kUA/L) had %100 specificity and PPV in predicting clinical reactivity to cashew, hazelnut and walnut, respectively. CONCLUSIONS: Multiplex macroarray test is useful and reliable in the diagnosis of TN allergy in children, confirms and expands existing knowledge, and can be used as a stand-alone tool in the bottom-up diagnostic approach.

Oleosin Cor a 15 is a novel allergen for Italian hazelnut allergic children.

BACKGROUND: Hazelnut allergy, which is characterized by symptoms that range from mild to severe, is one of the most common allergies in children throughout Europe, and an accurate diagnosis of this allergy is therefore essential. However, lipophilic allergens, such as oleosins, are generally underrepresented in diagnostic tests. We therefore sought to characterize the IgE reactivity of raw and roasted hazelnut oleosins, using the sera of hazelnut-allergic pediatric patients. METHODS: Raw and roasted hazelnut oil body-associated proteins were analyzed by means of 1D and 2D electrophoresis and MS. Oleosin IgE reactivity was assessed by immunoblotting with the sera of 27 children who have confirmed hazelnut allergies and from 10 tolerant subjects. A molecular characterization of the oleosins was performed by interrogating the C. avellana cv. Jefferson and cv. TGL genomes, and through expression and purification of the recombinant new allergen. RESULTS: A proteomic and genomic investigation allowed two new oleosins to be identified, in addition to Cor a 12 and Cor a 13, in hazelnut oil bodies. One of the new oleosins was registered as a new allergen, according to the WHO/IUIS Allergen Nomenclature Subcommittee criteria, and termed Cor a 15. Cor a 15 was the most frequently immunorecognized oleosin in our cohort. Oleosins resulted to be the only immunorecognized allergens in a subgroup of allergic patients who showed low ImmunoCAP assay IgE values and positive OFC and PbP. Hazelnut roasting resulted in an increase in oleosin immunoreactivity. CONCLUSION: A novel hazelnut oleosin, named Cor a 15, has been discovered. Cor a 15 could play a role in eliciting an allergic reaction in a subgroup of pediatric patients that exclusively immunorecognize oleosins. The high prevalence of hazelnut oleosin sensitization here reported further confirms the need to include oleosins in routine diagnostic procedures.

Hazelnut Allergy.

Background and Objectives: Hazelnuts are frequently involved in IgE-mediated reactions and represent the main culprit of nut allergy in Europe. The clinical presentation varies from mild symptoms limited to the oropharynx [oral allergy syndrome (OAS)], due to the cross-reaction with homologues in pollen allergens and more severe events caused by the primary sensitization to highly stable molecules contained in hazelnuts. The aim of this review is to summarize the most relevant concepts in the field of hazelnut allergy and to provide a practical approach useful in the clinical practice Materials and Methods: References were identified by PubMed searches dating from January 2000 up to November 2020 using the search terms: "component resolved diagnosis" and "Hazelnut allergy. Results: The storage proteins Cor a 9 and Cor a 14 resulted highly specific for primary hazelnut allergy and strongly associated with severe reactions, while the cross reactive Cor a 1, an homolog of the birch Bet v1, were related to OAS. Any cut-off has shown a specificity and sensitivity pattern as high as to replace the oral food challenge (OFC), which still remains the gold standard in the diagnosis of hazelnut allergy. To date there is still no definitive treatment. Hazelnut free-diet and treatment of symptoms with emergency management, including the prescription of auto-injective epinephrine, still represent the main approach. Oral allergen immunotherapy (AIT) appears a promising therapeutic strategy and the definition of individual clinical threshold would be useful for sensitized individuals, caregivers, and physicians to reduce social limitation, anxiety, and better manage food allergy. Conclusions: An accurate diagnostic work-up including clinical history, in vivo and in vitro test including component resolved diagnosis and OFC are essential to confirm the diagnosis, to assess the risk of a severe reaction, and to prescribe an adequate diet and treatment.

Component-resolved diagnostics can be useful for identifying hazelnut allergy in Japanese children.

BACKGROUND: Cor a 9 and Cor a 14 are effective markers for predicting hazelnut allergy. However, there have been no reports on the component-resolved diagnostics (CRD) of hazelnut allergy using an oral food challenge (OFC) for diagnosis in Asia. We hypothesized that CRD would improve the accuracy of diagnosing hazelnut allergies in Japanese children. METHODS: We recruited 91 subjects (median age: 7.3 years) who were sensitized to hazelnuts and had performed a hazelnut OFC at the National Hospital Organization Sagamihara National Hospital between 2006 and 2017. All subjects were classified as allergic or asymptomatic to 3 g of hazelnuts. The sIgE levels (hazelnut/Cor a 1/Cor a 8/Cor a 9/Cor a 14/alder pollen) were measured using ImmunoCAP. We aimed to determine the predictive factors of hazelnut allergy. RESULTS: Nine subjects (10%) were allergic to ≤3 g of hazelnuts. Levels of sIgE for Cor a 9 in hazelnut-allergic subjects were significantly higher than those in asymptomatic subjects (4.47 vs. 0.76 kUA/L, p = 0.039). Levels of sIgE to alder pollen and Cor a 1 in hazelnut-allergic subjects were significantly lower than those in asymptomatic subjects (<0.10 vs 13.0 kUA/L, p = 0.004; <0.10 vs 5.03 kUA/L, p = 0.025). The area under the receiver operating characteristics curve for hazelnut/alder/Cor a 1/Cor a 9 was 0.55/0.78/0.72/0.71, respectively, with p = 0.651/0.006/0.029/0.040, respectively. CONCLUSIONS: The findings of a high sIgE level for Cor a 9 and a low sIgE level for Cor a 1 can improve the diagnostic accuracy to better identify Japanese children sensitized to hazelnuts.

Retrospective definition of reaction risk in Italian children with peanut, hazelnut and walnut allergy through component-resolved diagnosis.

BACKGROUND: Serum IgE evaluation of peanut, hazelnut and walnut allergens through the use of component-resolved diagnosis (CRD) can be more accurate than IgE against whole food to associate with severe or mild reactions. OBJECTIVES: The aim of the study was to retrospectively define the level of reaction risk in children with peanut, hazelnut and walnut sensitization through the use of CRD. METHODS: 34 patients [n=22 males, 65%; median age eight years, interquartile range (IQR) 5.0-11.0 years] with a reported history of reactions to peanut and/or hazelnut and/or walnut had their serum analyzed for specific IgE (s-IgE) by ImmunoCAP® and ISAC® microarray technique. RESULTS: In children with previous reactions to peanut, the positivity of Arah1 and Arah2 s-IgE was associated with a history of anaphylaxis to such food, while the positivity of Arah8 s-IgE were associated with mild reactions. Regarding hazelnut, the presence of positive Cora9 and, particularly, Cora14 s-IgE was associated with a history of anaphylaxis, while positive Cora1.0401 s-IgE were associated with mild reactions. Concerning walnut, the presence of positive Jug r 1, Jug r 2, Jug r 3 s-IgE was associated with a history of anaphylaxis to such food. ImmmunoCAP® proved to be more useful in retrospectively defining the risk of hazelnut anaphylaxis, because of the possibility of measuring Cor a14 s-IgE. CONCLUSIONS: Our data show that the use of CRD in patients with allergy to peanut, hazelnut and walnut could allow for greater accuracy in retrospectively defining the risk of anaphylactic reaction to such foods.

Component-resolved diagnosis and beyond: Multivariable regression models to predict severity of hazelnut allergy.

BACKGROUND: Component-resolved diagnosis (CRD) has revealed significant associations between IgE against individual allergens and severity of hazelnut allergy. Less attention has been given to combining them with clinical factors in predicting severity. AIM: To analyze associations between severity and sensitization patterns, patient characteristics and clinical history, and to develop models to improve predictive accuracy. METHODS: Patients reporting hazelnut allergy (n = 423) from 12 European cities were tested for IgE against individual hazelnut allergens. Symptoms (reported and during Double-blind placebo-controlled food challenge [DBPCFC]) were categorized in mild, moderate, and severe. Multiple regression models to predict severity were generated from clinical factors and sensitization patterns (CRD- and extract-based). Odds ratios (ORs) and areas under receiver-operating characteristic (ROC) curves (AUCs) were used to evaluate their predictive value. RESULTS: Cor a 9 and 14 were positively (OR 10.5 and 10.1, respectively), and Cor a 1 negatively (OR 0.14) associated with severe symptoms during DBPCFC, with AUCs of 0.70-073. Combining Cor a 1 and 9 improved this to 0.76. A model using a combination of atopic dermatitis (risk), pollen allergy (protection), IgE against Cor a 14 (risk) and walnut (risk) increased the AUC to 0.91. At 92% sensitivity, the specificity was 76.3%, and the positive and negative predictive values 62.2% and 95.7%, respectively. For reported symptoms, associations and generated models proved to be almost identical but weaker. CONCLUSION: A model combining CRD with clinical background and extract-based serology is superior to CRD alone in assessing the risk of severe reactions to hazelnut, particular in ruling out severe reactions.

Cor a 14 is the superior serological marker for hazelnut allergy in children, independent of concomitant peanut allergy.

BACKGROUND: Hazelnut is the most frequent cause of tree nut allergy, but up to half of all children with hazelnut allergy additionally suffer from peanut allergy. Our aim was to identify diagnostic values of the most promising serological markers (Cor a 9 and Cor a 14) and to address the influence of concomitant peanut allergy and PR10 sensitization. METHOD: We included 155 children suspected of hazelnut allergy and challenged according to the guidelines. Concomitant allergy to peanuts was verified or ruled out by challenge. Skin prick test, s-IgE and CRD to hazelnut, peanut, PR10 and LPT protein families were measured using ImmunoCAP. RESULTS: Sixty-five children had a positive hazelnut challenge, and 60% of these also had a concomitant peanut allergy. Children allergic to hazelnut were sensitized to Cor a 9 and Cor a 14; peanut-allergic children were sensitized to Ara h 2. Sensitization to PR10 protein components was seen in 45% of all included children, irrelevant to allergy to peanut or hazelnut. A cut-off >0.72 kU/L of IgE towards Cor a 14 diagnosed 87% correctly, making Cor a 14 the superior serology marker. However, nine hazelnut-allergic children were primarily sensitized to Cor a 9. CONCLUSION: Concomitant peanut allergy is common in hazelnut-allergic children, but decision points as well as diagnostic values for Cor a 14 are not affected. We found three independent and well-characterized serotypes; hazelnut-allergic children were sensitized to Cor a 14, peanut-allergic children were sensitized to Ara h 2, and independently of this were children sensitized to birch pollen (Bet v 1).

Hazelnut Allergens: Molecular Characterization, Detection, and Clinical Relevance.

In last few years, special attention has been given to food-induced allergies, in which hazelnut allergy is highlighted. Hazelnut is one of the most commonly consumed tree nuts, being largely used by the food industry in a variety of processed foods. It has been regarded as a food with potential health benefits, but also as a source of allergens capable of inducing mild to severe allergic reactions in sensitized individuals. Considering the great number of reports addressing hazelnut allergens, with an estimated increasing trend, this review intends to assemble all the relevant information available so far on the following main issues: prevalence of tree nut allergy, clinical threshold levels, molecular characterization of hazelnut allergens (Cor a 1, Cor a 2, Cor a 8, Cor a 9, Cor a 10, Cor a 11, Cor a 12, Cor a 14, and Cor a TLP) and their clinical relevance, and methodologies for detection of hazelnut allergens in foods. A comprehensive overview of the current data about the molecular characterization of hazelnut allergens is presented, relating to biochemical classification and biological function with clinical importance. Recent advances in hazelnut allergen detection methodologies are summarized and compared, including all the novel protein-based and DNA-based approaches.

Hazelnut allergy across Europe dissected molecularly: A EuroPrevall outpatient clinic survey.

BACKGROUND: Hazelnut allergy is birch pollen-driven in Northern/Western Europe and lipid transfer protein-driven in Spain and Italy. Little is known about other regions and other allergens. OBJECTIVE: Establishing a molecular map of hazelnut allergy across Europe. METHODS: In 12 European cities, subjects reporting reactions to hazelnut (n = 731) were evaluated and sensitization to 24 foods, 12 respiratory allergen sources, and latex was tested by using skin prick test and ImmunoCAP. A subset (124 of 731) underwent a double-blind placebo-controlled food challenge to hazelnut. Sera of 423 of 731 subjects were analyzed for IgE against 7 hazelnut allergens and cross-reactive carbohydrate determinants by ImmunoCAP. RESULTS: Hazelnut allergy was confirmed in 70% of those undergoing double-blind placebo-controlled food challenges. Birch pollen-driven hazelnut sensitization (Cor a 1) dominated in most cities, except in Reykjavik, Sofia, Athens, and Madrid, where reporting of hazelnut allergy was less frequent anyhow. In Athens, IgE against Cor a 8 dominated and strongly correlated with IgE against walnut, peach, and apple and against Chenopodium, plane tree, and mugwort pollen. Sensitization to seed storage proteins was observed in less than 10%, mainly in children, and correlated with IgE to nuts, seeds, and legumes. IgE to Cor a 12, observed in all cities (10% to 25%), correlated with IgE to nuts, seeds, and pollen. CONCLUSIONS: In adulthood, the importance of hazelnut sensitization to storage proteins, oleosin (Cor a 12), and Cor a 8 is diluted by the increased role of birch pollen cross-reactivity with Cor a 1. Cor a 8 sensitization in the Mediterranean is probably driven by diet in combination with pollen exposure. Hazelnut oleosin sensitization is prevalent across Europe; however, the clinical relevance remains to be established.

Peanut allergy is common among hazelnut-sensitized subjects but is not primarily the result of IgE cross-reactivity.

BACKGROUND: Hazelnut and peanut are botanically unrelated foods, but patients are often sensitized and allergic to both, for reasons that are not well understood. METHODS: To investigate molecular cosensitization and cross-reactivity to peanut in hazelnut-sensitized individuals, children (n = 81) and adults (n = 80) were retrospectively selected based on sensitization to hazelnut. IgE to hazelnut extract, Cor a 1, 8, 9 and 14, to peanut extract, Ara h 1, 2, 3, 8 and 9, and to Bet v 1 was determined by ImmunoCAP. Allergy to hazelnut and peanut was established by DBPCFC and/or detailed clinical history. Patients were either tolerant or displayed subjective or objective symptoms to either food. IgE cross-reactivity between hazelnut and peanut storage proteins was assessed by reciprocal ImmunoCAP inhibition experiments. RESULTS: Of the 161 hazelnut-sensitized subjects, 109 (68%) were also sensitized to peanut, and 73 (45%) had clinical expression of allergy to peanut that was not associated with the presence or severity of hazelnut allergy. Instead, it was associated with IgE reactivity to peanut storage proteins, in particular Ara h 2. No cross-reactivity could be detected between Ara h 2 and Cor a 14, and 2 of 13 subjects displayed extensive cross-reactivity between 11S globulins; in plasma of both individuals, Ara h 3 almost completely inhibited IgE binding to Cor a 9. CONCLUSIONS: Peanut allergy is not primarily the result of IgE cross-reactivity to hazelnut storage proteins. IgE to Cor a 14 and Ara h 2 may serve as useful markers of primary sensitization to hazelnut and peanut, respectively.

Predictive values of component-specific IgE for the outcome of peanut and hazelnut food challenges in children.

BACKGROUND: Oral challenges are the gold standard in food allergy diagnostic, but time-consuming. Aim of the study was to investigate the role of peanut- and hazelnut-component-specific IgE in the diagnostics of peanut and hazelnut allergy and to identify cutoff levels to make some challenges superfluous. METHODS: In a prospective and multicenter study, children with suspected peanut or hazelnut allergy underwent oral challenges. Specific IgE to peanut, hazelnut, and their components (Ara h 1, Ara h 2, Ara h 3, and Ara h 8, Cor a 1, Cor a 8, Cor a 9, and Cor a 14) were determined by ImmunoCAP-FEIA. RESULTS: A total of 210 children were challenged orally with peanut and 143 with hazelnut. 43% of the patients had a positive peanut and 31% a positive hazelnut challenge. With an area under the curve of 0.92 and 0.89, respectively, Ara h 2 and Cor a 14-specific IgE discriminated between allergic and tolerant children better than peanut- or hazelnut-specific IgE. For the first time, probability curves for peanut and hazelnut components have been calculated. A 90% probability for a positive peanut or hazelnut challenge was estimated for Ara h 2-specific IgE at 14.4 kU/l and for Cor a 14-specific IgE at 47.8 kU/l. A 95% probability could only be estimated for Ara h 2 at 42.2 kU/l. CONCLUSIONS: Ara h 2- and Cor a 14-specific IgE are useful to estimate the probability for a positive challenge outcome in the diagnostic work-up of peanut or hazelnut allergy making some food challenges superfluous.

Differences in the intrinsic immunogenicity and allergenicity of Bet v 1 and related food allergens revealed by site-directed mutagenesis.

BACKGROUND: Birch pollen allergies are frequently associated with adverse reactions to various fruits, nuts, or vegetables, described as pollen-food syndrome (PFS) and caused by cross-reactive IgE antibodies primarily directed against Bet v 1. Specific immunotherapy (SIT) represents an effective treatment for inhalant allergies; however, successful birch pollen SIT does not correlate well with the amelioration of concomitant food allergies. METHODS: As vaccine candidates, apple Mal d 1 as well as hazelnut Cor a 1 derivatives were designed by in silico backbone analyses of the respective allergens. The proteins were produced by site-directed mutagenesis as fold variants of their parental allergens. Because Mal d 1 and Cor a 1 form cysteine-mediated aggregates, nonaggregative cysteine to serine mutants were also generated. The proteins were characterized physicochemically, immunologically, and in in vivo models with or without adjuvant. RESULTS: The structurally modified proteins showed significantly decreased IgE binding capacity. Notably, both in vivo models revealed reduced immunogenicity of the hypoallergenic fold variants. When formulated with alum, the monomeric cysteine mutants induced a similar immune response as the aggregated parental allergens, which is in contrast with data published on Bet v 1. CONCLUSION: These findings lead to the suggestion that the Bet v 1 structure has unique intrinsic properties, which could account for its high allergenicity. Obviously, these characteristics are not entirely shared with its food homologues from apple and hazelnut. Thus, it is important to tackle pollen-related food allergies from different angles for the generation of effective vaccine candidates to treat birch PFS.

Sensitization to Cor a 9 and Cor a 14 is highly specific for a hazelnut allergy with objective symptoms in Dutch children and adults.

BACKGROUND: Component-resolved diagnosis has been shown to improve the diagnosis of food allergy. OBJECTIVE: We sought to evaluate whether component-resolved diagnosis might help to identify patients at risk of objective allergic reactions to hazelnut. METHOD: A total of 161 hazelnut-sensitized patients were included: 40 children and 15 adults with objective symptoms on double-blind, placebo-controlled food challenges (DBPCFCs) and 24 adults with a convincing objective history were compared with 41 children and 41 adults with no or subjective symptoms on DBPCFCs (grouped together). IgE levels to hazelnut extract and single components were analyzed with ImmunoCAP. RESULTS: IgE levels to hazelnut extract were significantly higher in children with objective than with no or subjective symptoms. In 13% of children and 49% of adults with hazelnut allergy with objective symptoms, only sensitization to rCor a 1.04 was observed and not to other water-soluble allergens. Sensitization to rCor a 8 was rare, which is in contrast to rCor a 1. Sensitization to nCor a 9, rCor a 14, or both was strongly associated with hazelnut allergy with objective symptoms. By using adapted cutoff levels, a diagnostic discrimination between severity groups was obtained. IgE levels to either nCor a 9 of 1 kUA/L or greater or rCor a 14 of 5 kUA/L or greater (children) and IgE levels to either nCor a 9 of 1 kUA/L or greater or rCor a 14 of 1 kUA/L or greater (adults) had a specificity of greater than 90% and accounted for 83% of children and 44% of adults with hazelnut allergy with objective symptoms. CONCLUSION: Sensitization to Cor a 9 and Cor a 14 is highly specific for patients with objective symptoms in DBPCFCs as a marker for a more severe hazelnut allergic phenotype.

Reactivity to allergenic food contaminants: A study on products on the market.

BACKGROUND: The frequency and severity of reactions in food-allergic consumers exposed to unintentional food allergen contamination during production is unknown. To warn allergic consumers, it has been suggested for pre-packaged foods to be precautionary labelled when the food allergen contamination may exceed the amount to which 1%-5% of the population could react (ED01-ED05). ED01 for hazelnut and milk have been estimated at 0.1 and 0.2 mg, respectively, by the Voluntary Incidental Trace Allergen Labelling (VITAL) initiative. The respective reference doses recommended by the FAO/WHO Codex consultation are 3 and 2 mg. We evaluated the reactivity to potential traces of milk and hazelnut allergens in allergen-free pre-packaged products by children affected by severe allergies to milk and hazelnuts. METHODS: Oral Food Challenges with commercially available hazelnut-free wafer biscuits and milk-free chocolate pralines were administered to patients with severe food allergies to hazelnut and cow's milk, respectively. Contamination levels of milk or hazelnut allergens were measured using chromatographic separation interfaced with triple quadrupole mass spectrometry. RESULTS: No hazelnut allergic patient showed allergic reactions to exposure to biscuits, nor any milk allergic patient displayed allergic reactions to the dark chocolate praline. While no hazelnut trace was detected in biscuits, the praline was found to be contaminated by milk at concentrations ranging between 8 and 35 mg total protein/kg food. In our dose model, these amounts exceeded 1.5-10 times the VITAL ED01 and reached the threshold suggested by the FAO/WHO Codex consultation. CONCLUSIONS: Upon the consumption of food products available on the market, many patients with severe food allergies tolerate significantly higher doses of allergen than reference doses indicated in the VITAL system used for precautionary allergen labelling. These doses support the safety of the FAO/WHO recommended reference doses.