Concomitant sensitization to legumin, Fag e 2 and Fag e 5 predicts buckwheat allergy

BACKGROUND Buckwheat (Fagopyrum esculentum) has become increasingly popular as a healthy food in Europe. However, for sensitized individuals, consumption can cause anaphylactic reactions. The aim of this study was to identify individual well-characterized buckwheat allergens for component-resolved diagnosis. METHODS Patients were selected by positive skin prick test to buckwheat and divided into two groups: (1) sensitized to buckwheat without clinical symptoms and (2) buckwheat allergy. Buckwheat proteins were extracted from raw buckwheat seeds, purified applying a combination of protein precipitation and chromatographic methods, and analyzed by IgE immunoblotting and ELISA. RESULTS Buckwheat-allergic patients had a significantly larger median skin prick test weal diameter for buckwheat than the sensitized group and the positive control. Also, IgE immunoblotting clearly showed a distinct pattern in sera from allergic patients when compared to sensitized individuals. Several IgE-reactive proteins were purified from crude buckwheat extract, namely legumin (Fag e 1 plus its large subunit), Fag e 2 (2S albumin), and newly identified Fag e 5 (vicilin-like) as well as hevein-like antimicrobial peptides, designated Fag e 4. All four allergens showed superior diagnostic precision compared to extract-based ImmunoCAP with high sensitivity as well as high specificity. CONCLUSIONS Patients with clinical symptoms clearly show a distinct allergen recognition pattern. We characterized a buckwheat vicilin-like protein as a new relevant marker allergen, designated Fag e 5. Additionally, another new allergen, Fag e 4, potentially important for cross-reactivity to latex was added to the allergen panel of buckwheat. Further, our data show that the full-length legumin comprising both, large and small subunit should be applied for component-resolved diagnosis. Our data indicate that concomitant sensitization to legumin, Fag e 2 and Fag e 5, predicts buckwheat allergy.