Identification of gibberellin-regulated protein as a new allergen in orange allergy.

BACKGROUND: To date, three orange allergens have been reported. However, it is still unclear whether gibberellin-regulated proteins (GRPs), identified as new allergens in other fruit allergies, are also involved in orange allergy.

OBJECTIVE: To investigate the allergenicity of orange GRP and to determine the clinical characteristics of patients with orange allergy who are sensitized to orange GRP.

METHODS: We enrolled 14 patients (four men, 10 women, mean age: 29.6 years) who were diagnosed with orange allergy based on relevant clinical history, positive skin test, and/or positive challenge test. Orange GRP (molecular weight: 6941.6 Da) was purified by ion-exchange column chromatography. To test for orange GRP-specific IgE, we performed ELISA, basophil activation tests, and skin prick tests. Cross-reactivity of orange GRP with native peach allergen nPru p 7 and Japanese apricot nPru m 7 was analysed by ELISA inhibition assays. IgE specific for orange, grapefruit, and peach allergens rPru p 1, rPru p 3, and rPru p 4 was measured using ImmunoCAP.

RESULTS: Twelve of the 14 patients (85.7%) were positive for orange GRP allergy in at least one test: 71.4% (10/14) were positive by ELISA, 50% (3/6) were positive in the basophil activation test, and 100% (4/4) were positive in the skin prick test. ELISA inhibition assays revealed cross-reactivity of orange GRP with both nPru p 7 and nPru m 7. The patients showed variable positivity for specific IgE against orange, grapefruit, rPru p 1, rPru p 3, and rPru p 4 (57.1%, 71.4%, 7.1%, 0%, and 21.4%, respectively). The most frequent symptoms of orange GRP allergy were facial swelling and oropharyngeal symptoms.

CONCLUSIONS AND CLINICAL RELEVANCE: Orange GRP may be involved in orange allergy and may be a cross-reactive allergen between citrus fruits and the Rosaceae family of fruits.