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

Pollen allergens are multivalent proteins that cross-link: IgE antibodies o n mast or basophil cells, inducing secretion of biologic mediators, and res ulting in various allergic symptoms. The IgE-binding regions of the Parieta ria judaica (Pj) pollen major allergen rPar j 2 were investigated. Twenty-n ine single sera from Pj-allergic subjects were tested by Western brat again st five recombinant peptides. At least four putative IgE-binding epitopes w ere identified. The analysis of their diffusion suggested a heterogeneous I gE-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 no ne with peptide 48-76. These five peptides were analyzed with the histamine -release assay. Only peptide 48-101 was capable of inducing degranulation a nd release of histamine. These results suggest that the recombinant rPar j 2 allergen contains IgE epitopes that are heterogeneously recognized by sen sitive patients, and that therefore the therapeutic approach based on the u se of haptenic peptides needs a careful evaluation.