Allergen Profile of London Plane Tree Pollen: Clinical and Molecular Pattern in Central Spain

Abstract

Background: Platanus acerifolia is a deciduous tree of the Platanaceae family. Sensitisation to this plant varies with geography. Madrid, located in central Spain, has one of the highest pollen concentration levels of this tree of the Iberian Peninsula. Objectives: We evaluated both the clinical characteristics and molecular sensitisation pattern of patients with allergy to the London Plane tree in the region of Madrid. Patients and Methods: Thirty-eight patients allergic to London Plane tree pollen were selected according to clinical symptoms, positive skin prick test, and/or specific IgE. Serum was collected and allergen components were evaluated by immunodetection techniques as well as ImmunoCAP. IgE-binding proteins detected were identified and characterised by mass spectrometry. Results: Analysis of serum samples from allergic patients revealed 9 IgE-binding bands in London Plane tree-pollen extract. Among these, the 45-kDa protein, corresponding to Pla a 2, was detected in 76.3% of patients. However, the 18-kDa (Pla a 1) and 9-kDa (Pla a 3) bands were detected in 44.7% and 23.7% of sera, respectively. These results were confirmed using purified proteins. Allergen characterisation identified the 27-kDa protein to be glutathione-S-transferase. Conclusions: The molecular profile of patients sensitised to London Plane tree pollen differs from that reported in studies from other locations. Our population showed a higher prevalence of Pla a 2 compared to Pla a 1 and Pla a 3. In addition, the minor allergen previously referred to as Pla a 4 was characterised as glutathione-S-transferase.