IDENTIFICATION OF THE ALLERGENIC COMPONENTS OF KIWI FRUIT AND EVALUATION OF THEIR CROSS-REACTIVITY WITH TIMOTHY AND BIRCH POLLENS

Background: Only a few food allergens have as yet been identified, mai nly because of the difficulty of obtaining a sufficient number of pati ents who are clinically sensitized to a given food. This is more feasi ble in the case of the oral allergy syndrome (OAS), a common form of f ood allergy, which is especially prevalent in patients with pollinosis . Objective: We designed a study to identify the allergens of kiwi fru it (Actinidia chinensis) by analyzing the sera of patients with OAS fo r kiwi and to examine the cross-reactivity of these allergens with tim othy and birch pollen. allergens. Methods: Twenty-seven patients with OAS for kiwi, a positive skin prick test response and serum IgE antibo dy to kiwi, and a positive open kiwi challenge test result and three p atients who had OAS with severe systemic symptoms, which excluded a ch allenge test, were included in this study. The different polypeptide c omponents of an extinct of fresh kiwi were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and analyzed by IgE immunob lotting with sera from these patients. Cross-reactivity with the two p ollen. extracts was assessed by inhibition of the immunoblots with poo led and individual patients' sera. Results: Twelve IgE-binding compone nts with molecular weights ranging from 12 to 64 kd were identified in the kiwi extract, bur only a 30 kd component acted as major allergen, being recognized by sera of 100% of these patients. Inhibition of kiw i immunoblots with timothy and birch pollen extracts demonstrated stro ng cross-reactivity with some of the kiwi allergens, suggesting comple te identity between certain food and pollen allergens; whereas others, particularly the 30 kd allergen were only partially inhibited suggest ing much weaker cross-reactivity. Conclusions: Kiwi fruit contains a l arge number of allergens widely cross-reacting with allergens in grass and birch pollen extracts. Nevertheless, the major allergen at 30 kd appears to be specific for kiwi.