Background: Baker's asthma is a frequent IgE-mediated occupational disorder mainly provoked by inhalation of cereal flour. Allergy to kiwifruit has being increasingly reported in the past few years. No association between both allergic disorders has been described so far.
Methods: Twenty patients with occupational asthma caused by wheat flour inhalation were studied. Kiwi allergens Act d 1 and Act d 2 were purified by cation-exchange chromatography. Wheat, rye, and kiwi extracts, purified kiwi allergens, and model plant glycoproteins were analyzed by IgE immunodetection, enzyme-linked immunosorbent assay (ELISA), and inhibition ELISAs.
Results: Kiwifruit ingestion elicited oral allergy syndrome in 7 of the 20 patients (35%) with baker's asthma. Positive specific IgE and skin prick test responses to this fruit were found in all these kiwi allergic patients, and IgE to Act d 1 and Act d 2 was detected in 57% and 43%, respectively, of the corresponding sera. Actinidin Act d 1 and bromelain (harboring cross-reactive carbohydrate determinants) reached above 50% inhibition of the IgE binding to wheat and/or kiwi extracts.
Conclusions: A potential association between respiratory allergy to cereal flour and allergy to kiwifruit has been disclosed. Cross-reactive carbohydrate determinants and thiol-proteaseshomologous to Act d 1 are responsible for wheat-kiwi crossreactivity in some patients.