Identification of a 36-kDa olive-pollen allergen by in vitro and in vivo studies

Ole e 1 has been considered the major allergen of olive (Olea europaea) pollen. Some other relevant allergens (Ole e 2, 3, 4, and 6) have been recently described. This work aimed to study the IgE-binding frequency of a 36-kDa protein from O. europaea pollen in a large population of olive-allergic patients, its allergenic reactivity in vivo, and its presence in olive pollens of different origin, as well as in other relevant allergenic pollens.

Identification of IgE-binding components from O. europaea pollen extracts was elucidated by inhibition of SDS-PAGE immunoblotting using recombinant profilin (Ole e 2) and Ole e 1 molecules. The IgE-binding frequency of the 36-kDa protein was estimated by Western blot in a sample of 120 sera from olive-allergic patients. The cutaneous test with the 36-kDa protein was performed by intradermoreaction in allergic patients and control subjects.

Exactly 83% of the sera from O. europaea-allergic patients recognized a protein with an apparent molecular weight of 36 kDa, under reducing conditions. It was detected by sera from monosensitized and polysensitized patients, showing a higher IgE frequency than the major allergen Ole e 1 (59%) and the minor profilin (Ole e 2) allergen (27%). Similar reactivity rates (79%) was found by intradermal test. Extracts from olive pollens collected in California presented a much higher amount (around 16-fold on average) of the 36-kDa protein than those from pollens of Spanish origin. The presence of similar allergens was detected only in closely related species (Syringa, Fraxinus, Ligustrum), and not in other common allergenic pollens.

The 36-kDa protein constitutes a major allergen for olive-sensitized patients, but it is not equally represented in O. europaea pollens of different origins.