Unexpected allergenic 11S globulin (Act d 12) and 2S albumin (Act d 13) from kiwi seeds as novel masked relevant components in kiwifruit allergy

Abstract

Background: Kiwifruit is a common cause of IgE-mediated food allergy. Component-resolved diagnosis of kiwifruit allergy suggests that relevant allergenic components are still undiscovered. The presence of allergens in kiwi seeds has not been investigated in detail so far. Objective: To increase the diagnostic sensitivity of kiwifruit allergy by identifying new allergens that might have been masked due to their specific location in seeds. Methods: Fifty-five kiwifruit allergic patients were included in the study. Immunoblotting, proteomic tools and Edman degradation were used to identify and purify IgE-reactive proteins from kiwi seeds. Circular dichroism, mass spectrometry, immunoblotting, enzyme-linked immunosorbent assay, skin prick test and IgE-inhibition experiments were used for structural and immunological characterization of purified allergens. Results: Two novel allergens, an 11S globulin (Act d 12) and a 2S albumin (Act d 13) have been identified and purified from kiwi seeds. Both purified molecules display the typical structural features reported for other members of their corresponding protein families. Act d 12 and Act d 13 retain IgEbinding capacity and are recognized by 70.9 % and 18.2 %, respectively, of the tested kiwifruit allergic patients. Both purified allergens show in vivo allergenicity and display in vitro IgE-cross reactivity with homologous counterparts from peanut and tree nuts. Conclusion: The identifica tion of 11S globulin Act d 12 and 2S albumin Act d 13 as novel relevant allergens from kiwi seeds and their availability as well-defined molecules might contribute to improve the diagnosis of kiwifruit allergy.