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Variety of lentil proteins makes recommendations on avoidance difficult

Published Online: July 24, 2015

Lentils together with chickpeas are a common cause of IgE-mediated food hypersensitivity reactions in children from the Mediterranean, Middle East, and some Asian countries. In Spain lentil is the 5th and in Turkey the 6th most common food allergen in the pediatric population.  Due to changing preferences and culinary trends, consumption of lentils and related legumes, often categorized under the Indian term of “dal,” has increased in the United States and Northern Europe. Allergy to lentils has been extensively studied and allergenic peptides and epitopes have been described. In contrast to tree nut allergens, little is known about cross-reactivity among dal proteins to guide clinical management and recommendations for patients allergic to lentils.

In a recent publication in The Journal of Allergy and Clinical Immunology: In Practice, Andreae and colleagues investigated similarities and cross-reactivities among lentils and related legumes in order to better advise lentil allergic patients on appropriate food avoidance. IgE binding patterns, IgE levels, clinical reaction histories, and protein sequence similarities were investigated. Since lentil consumption varies across different parts of the world, three patients from Spain, Turkey, and the United States, each allergic to lentils, were recruited. Extracts from green lentil (lens culinaris green), toor dal (Cajanus cajan), mung dal (Vigna radiate), urad dal (Vigna mungo), chana dal (Cicer arietinum), mooth dal (Vigna aconitifolia), and masoor dal/red lentil (lens culinaris red) were prepared. IgE binding to all protein extracts was performed by immunoblotting. IgE binding patterns, protein banding patterns and clinical reaction, and avoidance histories were recorded and compared between patients. The protein sequence is known for lentil (lens culinaris), chickpea, and peanut proteins. These sequences were compared to assess the degree of similarity.

IgE binding of patients allergic to lentil was detected to all lentil-like proteins independent of specificity of clinical reactions. The majority of binding was detected in regions that were previously described as allergens in lens culinaris. The patient’s IgE binding patterns did not distinguish between tolerance and allergy. In this small sample, neither IgE levels nor co-sensitization to other legumes or pollens predicted the severity or type of reaction reported.

These results indicate a high degree of identity at the protein level between selected lentil-like (dal) proteins and other legumes. In view of the similarity noted at the protein level, no prediction about the likelihood of tolerance versus reactivity could be made, even in patients with symptoms due to distinct types of lentils. At this point, oral food challenge testing remains the only reliable method for predicting tolerance or reactivity to various lentils. Identification of the primary protein sequence and description of IgE binding epitopes together with competition and inhibition experiments will be necessary to guide clinical recommendations for allergic patients.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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