Identification and characterization of percutaneously sensitizing fruit allergens

Background and objectives: Recently, transdermal sensitization, in which food antigens enter through the skin and sensitize, has been attracting attention as a route for the development of food allergy. Fruits are used not only as food, but also in some cosmetics, and are often in contact with the skin. In this study, we investigated the dermal sensitization potential of cherries, kiwifruit (green/gold), and mangoes, and identified and characterized dermal sensitization antigens. Methods: Six-week-old female BALB/c mice were divided into a control group and each fruit group. Once a week at the time of blood collection, the back of the head was shaved and tape-stripped, and 5% SDS was applied. Each sample was applied 4 times a week to each group. Only 5% SDS was applied for the control group and fruit extract/5% SDS for each fruit group, and serum levels of fruit specific IgE and IgG1 and the binding protein(s) of each antibody (candidate transdermal sensitization antigen) were detected by ELISA and immunoblotting (IB), and the antibody-binding proteins were purified by various chromatographic methods. Results: Applied fruit specific IgE and IgG1 production was confirmed in each fruit group by ELISA. The IgE and IgG1 binding proteins were detected around 18, 23~25 kDa in kiwifruit, 27 kDa in cherry and 28 kDa in mango, depending on the IB. Obtained results suggest that these fruit proteins have transdermal sensitizing ability. Next, we purified and identified the sensitizing antigens and found kiwellin (Act d 5) in kiwifruit and thaumatin- like protein (Pru av 2) in cherry as the putative transdermal sensitizing allergens. Discussion: Both kiwellin and thaumatin-like protein identified in this experiment are commonly found in plants and have a protective effect against infection. Therefore, it is suggested that the transdermal sensitization antigens of fruits might be related to plant defense proteins. In addition, it is notable that these proteins contain many S-S bonds in molecules. Identification of sensitizing antigens in mango is under progress.