Background: An association between plane tree pollen allergy and plant food allergy has been described, but the cross-reacting allergens have not yet been identified. The aim of this study was the identification of homologous non-specific lipid-transfer proteins (nsLTPs) in plane pollen, and to investigate its immunological relationship with the peach LTP, Pru p 3.
Methods: Three different patient groups were recruited in Spain: 22 plane pollen-allergic patients without food allergy (A), 36 plane pollen-allergic patients with peach allergy (B) and 10 peach-allergic patients without plane pollen allergy (C). Proteins from plane pollen extract were fractionated by ion-exchange and reversed-phase chromatography. Further methods applied were N-terminal amino acid sequence analysis, immunoblotting, enzyme allergosorbent test, CAP and basophil histamine release assays.
Results: A 10 kDa IgE-reactive protein was purified from plane pollen and identified as nsLTP. Pla a 3 was characterized as a minor allergen (27.3%) in plane pollen-allergic patients without food allergy (A) and as a major allergen in plane pollen-allergic patients with peach allergy (B) showing a prevalence of IgE-reactivity of 63.8%. Group B contained patients sensitized to Pru p 3 without IgE-reactivity to plane-LTP (16.6%). By contrast, Pla a 3 IgE-reactive patients without sensitization to Pru p 3 could be found (16.6%). The sera of patients sensitized to both LTPs (50%), Pla a 3 and Pru p 3, showed different biological activity in histamine release assay: depending on individual patient's sera tested, Pla a 3 showed a similar, a stronger or a weaker allergenic potency in comparison with Pru p 3.
Conclusions: Plane LTP is a major allergen in plane pollen-allergic patients with peach allergy recruited in the Mediterranean area. The results of histamine release tests and different IgE-binding profiles pointed towards the existence of species-specific IgE epitopes. Likewise, no general conclusion on the sensitizer could be made.