Purification and characterization of the main allergen of Plantago lanceolata pollen, Pla l 1

Background English plantain (Plantago lanceolata) pollen is an important ca use of pollinosis in the temperate regions of North America, Australia and Europe. However, very little is known about its allergen composition. Objective The aim of this study was to identify plantain allergens, and to isolate and characterize a major allergen. Methods Allergens were identified by immunoblotting with individual allergi c patients' sera. Isolation of the major allergen was achieved by sequentia l reverse-phase and size-exclusion HPLC. Allergenic characterization was pe rformed by ELISA and immunoblotting after SDS-PAGE with sera from plantain- allergic patients. N-terminal amino acid sequence was established by Edman degradation. Results Allergograms showed that 13 out of the 14 sera assayed had IgE to a group of proteins with a molecular weight in the range of 16-20 kd, that t urned out to be different isoforms or variants of the major allergen Pla l 1. Eighteen amino acid residues from the N-terminal end of one of the isofo rms, and 10 of three others, were sequenced, and a partial sequence identit y with Ole e 1 was found. Prevalence of specific IgE to purified Pla l 1 in plantain allergic patients was 86%, and represents about 80% of the total IgE-binding capacity of the plantain extract. Conclusions The most relevant allergen from P.lanceolata pollen, Pla l 1, h as been purified and characterized. This contributes to a greater knowledge of the allergen composition of this important weed, and clears the way for the standardization of plantain allergen products in terms of major allerg en content.