Cultivar-specific IgE-epitopes in date (Phoenix dactylifera L.) fruit allergy - Correlation of skin test reactivity and IgE-binding properties in selecting date cultivars for allergen standardization

Background: Date fruits are allergenic and standardized extracts are requir ed for diagnosis and therapy of this allergy. Since there are several culti vars of dates, this study was carried out to assess the allergenicity of di fferent cultivars in order to select suitable source material for standardi zation. Methods: The protein profiles of 18 of the most commonly sold varie ties were compared by SDS-PAGE and their relative allergenicity assessed by SPT and IgE-based ELISA and immunoblotting. Thirty-two date fruit-sensitiv e patients were skin tested with a pooled extract from all the cultivars. S ix of the patients with high SPT results (greater than or equal to 3+) who volunteered were further tested with the 18 cultivars and their sera used i n ELISA and immunoblotting. Results: Six of the cultivars gave high SPT-pos itive reactions in greater than or equal to4 of patients. Five of these hig h SPT-reactive cultivars gave high IgE ELISA scores (greater than or equal to0.58) but individual cultivars varied in their number of IgE immunoblot b ands. Cultivar-specific IgE-binding patterns indicated that only certain cu ltivars bound IgE at molecular weights of less than or equal to 14.3 and 27 -33 kDa whilst all cultivars bound to a 54-58 kDa doublet. Cultivars that b ind to the less than or equal to 14.3 and 27-33 kDa bands appeared to form the majority of the high SPT-reactive cultivars. When individual sera of 24 of the 32 SPT-positive patients were used in IgE immunoblots with the pool ed cultivar extract, all sera bound IgE at less than or equal to 14.3 and 2 7-33 kDa and about 60% of sera bound to a 54-58 kDa doublet bands. Conclusi ons: These results indicate that allergenicity of date fruits is a cultivar -specific phenomenon. Sixty to 100% of sera from date fruit-allergic patien ts bind IgE to three major allergens of less than or equal to 14.3, 27-33 a nd 54-58 kDa. Five of the cultivars that evoke high SPT reactions, high IgE ELISA scores and bind IgE to the major allergens, can be selected for the preparation of 'in-house' allergen extracts and for allergen standardizatio n. Copyright (C) 2000 S. Karger AG,Basel.