Purified allergens vs. complete extract in the diagnosis of plane tree pollen allergy.

BACKGROUND: Plane tree pollen allergy is a clinical disorder affecting human population in cities of Europe, North America, South Africa, and Australia. OBJECTIVE: To compare IgE-reactivity of the natural and recombinant forms of two major plane allergens, Pla a 1 and Pla a 2, with the reactivity of Platanus acerifolia pollen extract. METHODS: Forty-seven patients with P. acerifolia allergy, 15 of them monosensitized, and 24 control subjects were included in the study. Natural Pla a 1 and Pla a 2 were purified by standard chromatographic methods and recombinant proteins were expressed in Escherichia coli. Skin prick test and determination of specific IgE were performed with commercial P. acerifolia extract and natural and recombinant purified allergens. RESULTS: Pla a 1 and Pla a 2 were responsible for 79% of the IgE-binding capacity against P. acerifolia pollen extract. A high correlation has been found between the IgE response to nPla a 1 (R = 0.80; P < 0.001) or nPla a 2 (R = 0.79; P < 0.001) vs. P. acerifolia extract as well as between natural and recombinant Pla a 1 (R = 0.89; P < 0.001). Skin testing showed no significant differences between extract and nPla a 2, whereas a higher reactivity was found with nPla a 1. In contrast, rPla a 1 revealed markedly reduced sensitivity in comparison with extract by skin prick test and specific IgE. The sensitivity of the mix Pla a 1+Pla a 2 was 100% and 87.5% for monosensitized and polysensitized patients, respectively, with no false-positive reactions detected. Conclusion Pla a 1 and Pla 2 are sufficient for a reliable diagnosis of P. acerifolia in most patients and induce comparable skin test reactivity as a whole extract.