Multiple IgE recognition on the major allergen of the Parietaria pollen Par j 2

• We performed in silico prediction of IgE binding regions on the major allergen of the Parietaria pollen Par j 2.
• Par j 2 was fragmented by genetic engineering and expressed in E. coli.
• Seventy nine Parietaria allergic children were selected and their sera collected.
• IgE reactivity of the fragments was evaluated by means of western blotting.

The interaction between IgE antibodies and allergens is a key event in triggering an allergic reaction. The characterization of this region provides information of paramount importance for diagnosis and therapy. Par j 2 Lipid Transfer Protein is one of the most important allergens in southern Europe and a well-established marker of sensitization in Parietaria pollen allergy. The main aim of this study was to map the IgE binding regions of this allergen and to study the pattern of reactivity of individual Parietaria-allergic patients. By means of gene fragmentation, six overlapping peptides were expressed in Escherichia coli, and their IgE binding activity was evaluated by immunoblotting in a cohort of 79 Parietaria-allergic patients. Our results showed that Pj-allergic patients display a heterogeneous pattern of IgE binding to the different recombinant fragments, and that patients reacted simultaneously against several protein domains spread all the over the molecule, even in fragments which do not contain structural features resembling the native allergen. Our results reveal the presence of a large number of linear and conformational epitopes on the Par j 2 sequence, which probably explains the high allergenic activity of this allergen.