The IgE-binding epitopes of rPar j 2, a major allergen of Parietaria judaica pollen, are heterogeneously recognized among allergic subjects


Dr Domenico Geraci, Istituto di Biologia dello Sviluppo, CNR, Via Ugo La Malfa 153, 90146 Palermo, Italy


Pollen allergens are multivalent proteins that cross-link IgE antibodies on mast or basophil cells, inducing secretion of biologic mediators, and resulting in various allergic symptoms. The IgE-binding regions of the Parietaria judaica (Pj) pollen major allergen rPar j 2 were investigated. Twenty-nine single sera from Pj-allergic subjects were tested by Western blot against five recombinant peptides. At least four putative IgE-binding epitopes were identified. The analysis of their diffusion suggested a heterogeneous IgE-binding response. In fact, 75% of the sera reacted with peptide 1–54, 48% with peptide 48–101, 24% with peptide 1–30, 7% with peptide 29–54, and none with peptide 48–76. These five peptides were analyzed with the histamine-release assay. Only peptide 48–101 was capable of inducing degranulation and release of histamine. These results suggest that the recombinant rPar j 2 allergen contains IgE epitopes that are heterogeneously recognized by sensitive patients, and that therefore the therapeutic approach based on the use of haptenic peptides needs a careful evaluation.