ORIGINAL PAPER Purified allergens vs. complete extract in the diagnosis of plane tree pollen allergy J. A. Asturias à , I. Ibarrola à , P. Amat w , R. Tella z , A. Malet w , A. Cister ´ o-Bah´ ıma z , E. Enrique ‰ , T. Malek ‰ and A. Mart´ ınez à à Bial-Ar´ ıstegui, R&D Department, Bilbao w Al.lergo Centre, Barcelona, Spain z Servicio de Alergia, Institut Universitari Dexeus-UAB, Barcelona and ‰ Servicio de Alergia, Hospital General de Castell ´ on, Spain Clinical and Experimental Allergy Correspondence: Dr Juan A. Asturias, Bial-Ar´ ısteguI, R&D, Alameda Urquijo 27, 48008-Bilbao, Spain. E-mail: juan.asturias@bial.com Summary 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 o 0.001) or nPla a 2 (R = 0.79; P o 0.001) vs. P. acerifolia extract as well as between natural and recombinant Pla a 1 (R = 0.89; P o 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 11Pla 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. Keywords component-resolved diagnosis, IgE detection, Pla a 1, Pla a 2, plane tree allergy, recombinant allergen, skin prick tests Submitted 24 February 2006; revised 31 May 2006; accepted 31 July 2006 Introduction The diagnosis of pollen allergy is based on clinical history and detection of IgE-specific antibodies with in vitro tests or skin tests, but both techniques are influenced by the inherent heterogeneity of allergenic extracts. Nowadays, purified proteins for in vitro assays instead of complex allergenic extracts are more widely used as some allergens are available, allowing a component-resolved diagnosis [1–3]. Diagnostic studies using allergenic molecule-based approaches for skin testing have also been performed [4–6]. Purified allergens have even been used for allergen-specific immunotherapy [7, 8] and for monitoring antibodies re- sponse after allergen-specific immunotherapy [9]. Platanus acerifolia is one of the most common trees found in European cities because of its resistance to diseases and urban-polluted environment. In Spain, this pollen is the most important allergen during its flowering season (March–April) [10] with prevalences by skin prick test (SPT) of 56% in Madrid, 35% in western Spain and 8.5% in Barcelona [11–13]. The clinical importance of Platanus pollen has also been demonstrated in studies from southern France and Switzerland [14, 15]. An association between Platanus pollen and some vegetable foods such as hazelnut, peanut, banana, and celery has been found in 84% of patients allergic to plant foods [16] and cross-reactivity between lettuce-LTP and Platanus- pollen extract has also been reported [17]. P. acerifolia Clinical and Experimental Allergy, 36, 1505–1512  c 2006 The Authors Journal compilation  c 2006 Blackwell Publishing Ltd