Title: IgE from Some Green Kiwifruit Allergic Individuals Binds to Proteins in Hardy Kiwifruit, a Third Cultivated Species of the Genus Actinidia
Abstract: RATIONALE: Since hardy kiwifruit (Acintinidia arguta) is now cultivated in western North America, we tested protein extracts of hardy, green (Actinidia deliciosa) and gold (Actinidia chinensis) kiwifruit for IgE binding using sera from individuals with clinically diagnosed food allergies to green kiwifruit, to evaluate potential cross-reactivity. METHODS: Sera from twelve green kiwifruit-allergic subjects (eight were positive by DBPCFC, four severe reactors were not challenged but had positive ImmunoCAP) and control subjects were assayed for IgE binding to soluble proteins in green, gold and hardy kiwifruits using reducing and non-reducing SDS-PAGE immunoblots and direct enzyme linked immunosorbent assays (ELISA). RESULTS: IgE-ELISA results of all kiwi-allergic subjects were positive compared to controls for one or more kiwifruit extracts. Immunoblot results demonstrated individual patient and species variability. Two sera with strong ELISA positive results to both hardy and green, but not gold kiwifruit did not show marked IgE binding to kiwifruit proteins on immunoblots with reduced, heat denatured extracts, but clearly bound two or more proteins from non-reduced, unheated extracts of hardy, but not green kiwifruit. One kiwifruit-allergic individual had marked binding to non-reduced, unheated gold kiwifruit proteins. Only one kiwifruit-allergic individual had marked binding to proteins of all species on the reduced gel blot. Some control sera showed marked IgE binding to high molecular weight proteins on immunblots. CONCLUSIONS: These results suggest some kiwifruit-allergic individuals may suffer allergic cross-reactions if they consume hardy kiwifruit. They also demonstrate the difficulty in developing in vitro reagents for accurate diagnosis of kiwifruit allergy and for correctly identifying major allergens.