Olive allergen-specific IgE responses in patients with Olea europaea pollinosis

Background Olive tree (Olea europuea) pollen is an important cause of pollinosis in the countries of the Mediterranean area. Objective This work aimed to study the IgE-binding frequency of Ole a 1, Ole a 2, Ole a 3, Ole e 6 and Ole e 7 from O. europaea pollen in a large population of olive pollen-allergic patients. Methods We studied: 119 consecutive patients with seasonal rhinitis and/or asthma and a positive skin prick test to O. europaea pollen extract; 10 atopic patients without history of pollinosis and a negative skin prick test to O. europaea; and 10 healthy controls. Allergens were purified from O. europaea pollen extract by reverse phase HPLC and characterized by N-terminal amino acid sequencing, MALDI analysis, and specific IgE immunodetection. Skin prick tests and ELISA titration against above mentioned purified olive pollen allergens were performed in all pollinic patients and controls. Results One-hundred and seven (90.7%) patients had a positive skin response to Ole a 1; 88 (74.6%) reacted to Ole a 2; 57 (47.9%) reacted to both Ole e 6 and Ole a 7; and 43 (37.8%) reacted to Ole a 3. The allergenic activity determined by ELISA to Ole e 1 was found in 84%; to Ole e 2 in 61.3%; to Ole e 3 in 31.9%; to Ole e 6 in 39.4%; and to Ole e 7 in 41.2% of patients. All patients had positive skin responses to at least one of the allergens tested, However, a combination of Ole e 1 and Ole e 2 together with a minor allergen Ole e 6 or Ole a 7, disclosed the same diagnostic value that was obtained with the use of crude olive pollen extract. The nonatopic and atopic control subjects did not react to any purified allergens on the skin prick test. Conclusions These results indicate that Ole e 1 and Ole e 2 are major allergens in patients with O. ettropuea pollinosis in our population. A combination of a few olive pollen allergens can substitute the crude extract for in vivo as well as in vitro diagnostic purposes.