Anaphylaxis after consuming soy products in patients with birch pollinosis

Utility of the Basophil Activation Test Using Gly m 4, Gly m 5 and Gly m 6 Molecular Allergens for Characterizing Anaphylactic Reactions to Soy

There are two major clinically described forms of IgE-dependent soy allergy: (i) a primary dietary form, linked to sensitization against soy storage proteins Gly m 5 and Glym 6, and (ii) a form included in birch-soy syndromes linked to Gly m 4, a PR-10-like allergen. This second form sometimes causes severe systemic reactions, even anaphylaxis, especially on consuming certain forms of soy such as soymilks or smoothies. Skin prick tests and specific IgE assays against soy whole extracts lack sensitivity. Assays of anti-Gly m 4, Gly m 5 and Gly m 6 specific IgEs have been developed to overcome this obstacle, but they unfortunately lack specificity, especially for anti-Gly m 4. We hypothesized that the basophil activation test (BAT) using molecular soy allergens Gly m 4, Gly m 5 and Gly m 6 would both remedy the lack of sensitivity of other tests and offer, through its mechanistic contribution, greater specificity than the assay of anti-Gly m 4 specific IgEs. This would enable the two types of soy allergy to be separately identified. In a characteristic clinical example of PR-10-induced anaphylactic reaction after consuming soymilk, we report preliminary results of Gly m 4-exclusive positivity of BAT supporting our hypothesis. It will be necessary to confirm these results on more patients in subsequent studies, and to specify the place of the BAT in an overall diagnostic strategy. Meanwhile, soy BAT using molecular allergens is a promising diagnostic tool for soy allergy and probably also for follow-up in specific immunotherapies.

Components in soy allergy diagnostics: Gly m 2S albumin has the best diagnostic value in adults

BACKGROUND

Thus far, four soy allergens have been characterized. Their diagnostic value was assessed only using a case-control design with controls not suspected of soy allergy or in a soy-allergic population without controls. Our objective was to analyze the diagnostic value of specific immunoglobulin E (sIgE) to Gly m 2S albumin, Gly m 4, 5, and 6, and their possible relation with severity or culprit soy product.

METHODS

Adult patients suspected of soy allergy were included (n = 46). Allergy was confirmed by challenge (n = 19) or history (n = 16) and excluded by challenge in 11 patients. Soy components were analyzed by ImmunoCAP. Diagnostic value was assessed in the challenged patient group by an area under receiver operating characteristic (ROC) curve (AUC).

RESULTS

Specific immunoglobulin E to Gly m 2S albumin had the highest AUC (0.79), comparable to skin prick test (SPT) and sIgE to soy extract (0.76 and 0.77, respectively). All patients were sensitized to either soy extract or Gly m 4 (sIgE ≥ 0.35 kU/l). sIgE to soy extract, Gly m 5, and Gly m 6 was significantly higher in patients with mild symptoms (P = 0.04, 0.02 and 0.02, respectively). Patients only reacting to soy milk had higher sIgE levels to Gly m 4 (median 9.8 vs 1.1 kU/l, P = 0.01).

CONCLUSION

Specific immunoglobulin E to Gly m 2S albumin had the best accuracy in diagnosing soy allergy. Gly m 5 and 6 were related to mild symptoms. Higher levels of Gly m 4 were related to allergy to soy milk.

Food allergy: management, diagnosis and treatment strategies

Food allergy is an increasing problem in western countries, with strict avoidance being the only available reliable treatment. However, accidental ingestion can occur and anaphylactic reactions still happen. In recent years, many efforts have been made to better understand the humoral and cellular mechanisms involved in food allergy, and to improve the strategies for diagnosis and treatment. This review focuses on IgE-mediated food hypersensitivity and provides an overview of the diagnostic strategies and treatment advances. Specific immunotherapy, including different routes of administration and allergen sources, such as natural, recombinant and T-cell epitopes, are analyzed in detail. Other treatments such as anti-IgE monoclonal antibody therapy, adjuvant therapy and Chinese herbs will also be described.

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.

Allergen chip diagnosis for soy-allergic patients: Gly m 4 as a marker for severe food-allergic reactions to soy

BACKGROUND

Gly m 5 and Gly m 6 are known to induce severe reactions in soy-allergic patients. For birch pollen (BP)-allergic patients, the Bet v 1 homologous allergen Gly m 4 is also a potential trigger of generalized severe reactions upon soy consumption. Therefore, reliable component-resolved diagnosis of soy allergy is needed.

METHODS

IgE reactivity from sera of 20 patients from a BP environment with reported soy allergy was assessed. Skin prick tests (SPT) with BP and soy drink were performed. Specific IgE for BP, soy, Bet v 1 and Gly m 4 was analyzed by ImmunoCAP. In addition, ISAC microarray profiling was performed.

RESULTS

Nineteen of 20 patients were BP allergic (positive SPT and/or CAP results for BP extract and Bet v 1). Eighteen soy-allergic patients were tested positive with soy drink in SPT. Soy CAP results were negative in the majority of tests (15/20), whereas 19/20 sera had specific IgE to Gly m 4. In the microarray approach, 14/20 sera displayed Gly m 4-specific IgE, the additional 6 sera had IgE levels below 0.3 ISAC standardized units. The BP-negative serum had Gly m 5- and Gly m 6-specific IgE which correlated with positive soy ImmunoCAP.

CONCLUSIONS

Soy sensitization detected by SPT and Gly m 4 ImmunoCAP were in good qualitative agreement with ISAC results. Soy ImmunoCAP was only specific for Gly m 5 and Gly m 6 sensitization. Gly m 4 ImmunoCAP has a higher sensitivity than ImmunoCAP ISAC. In this patient cohort, Gly m 4 sensitization was linked to the development of severe and generalized allergic reactions upon soy consumption.

Determinants of food allergy

Food allergy is an emerging epidemic in the United States and the Western world. The determination of factors that make certain foods allergenic is still not clearly understood. Only a tiny fraction of thousands of proteins and other molecules is responsible for inducing food allergy. In this review, the authors present 3 examples of food allergies with disparate clinical presentations: peanut, soy, and mammalian meat. The potential relationships between allergen structure and function, emphasizing the importance of cross-reactive determinants, immunoglobulin E antibodies to the oligosaccharides, and the immune responses induced in humans are discussed.

A food matrix reduces digestion and absorption of food allergens in vivo

SCOPE

Food allergy is caused by primary (class 1) food allergens, e.g. Bos d 5 (cow's milk) and Cor a 8 (hazelnut) or secondary (class 2) food allergens, e.g. Mal d 1 (apple). The latter cannot sensitize susceptible individuals but can cause allergy due to immunological cross-reactivity with homologous respiratory allergens. Here, we studied the effects of food matrix on gastrointestinal proteolysis, epithelial transport and in vivo absorption of class 1 and class 2 food allergens.

METHODS AND RESULTS

Mal d 1 lost its IgE-reactivity immediately after simulated gastric digestion whereas Bos d 5 and Cor a 8 did not. Only Cor a 8 maintained IgE-binding capacity after simulated intestinal proteolysis. The presence of hazelnut and peanut extracts, which served as protein-rich model food matrices, delayed gastrointestinal degradation and reduced epithelial transport rates of all allergens through CaCo-2 monolayers. Finally, IgE-reactive allergens were assessed at different time points in sera from rats fed with all three allergens with or without hazelnut extract. The levels of all allergens peaked 2 h after animals were fed without matrix and increased over 8 h after feeding.

CONCLUSIONS

A protein-rich food matrix delays gastrointestinal digestion and epithelial transport of food allergens and thereby may affect their sensitizing capacity and clinical symptoms.