Poppy Seed Allergy: Molecular Diagnosis and Cross-Reactivity With Tree Nuts

Background: Poppy seed (PS) can be a cause of severe allergic reactions, especially in individuals with concurrent allergy to tree nuts and other seeds, but diagnostic criteria and sensitization patterns are lacking. Objective: To assess the role of PS extract and individual allergens in diagnosing PS allergy and their cross-reactivities with tree nuts and buckwheat. Methods: Our retrospective study included 36 PS-sensitized patients; 10 with a positive and 26 with a negative oral food challenge (OFC). We identified individual PS allergens and compared the diagnostic performance of specific IgE (sIgE) to PS extract with its allergens. Cross-reactivities between PS and related allergens from other seeds were assessed by a competitive enzyme-linked immunosorbent assay. Results: We identified 4 novel PS allergens: Pap s 1 (vicilin), Pap s 1 (27-424) (alpha-hairpinin), Pap s 2 (legumin), and Pap s 3 (small hydrophilic seed protein). A positive OFC correlated with higher PS-sIgE levels and elevated sIgE levels for the PS allergens, except for Pap s 3. PS and alpha-hairpinin-sIgE effectively differentiated allergic from tolerant patients, with area under the curve values of 0.95 and 0.94. PS-sIgE >10.00 kU(A)/L exhibited 90% sensitivity and 73% specificity, whereas alpha-hairpinin-sIgE >2.60 kU(A)/L showed 100% sensitivity and 77% specificity. PS vicilin and legumin highly cross-reacted with hazelnut and buckwheat homologs, whereas alpha-hairpinin-sIgE cross-reacted with the related almond allergen. Conclusions: This is the most extensive study on PS allergy to date. PS and alpha-hairpinin-sIgE are highly sensitive indicators of clinical reactivity to PS, whereas vicilin and legumin-sIgE contribute to concurrent sensitization to hazelnut and buckwheat.