Mapping and conformational analysis of IgE-binding epitopic regions on the molecular surface of the major Ara h 3 legumin allergen of peanut (Arachis hypogaea).

Eight distinct sequential IgE-binding epitopes were identified along the amino acid sequence of Ara h 3 using the Spot technology. They essentially correspond to preferencially electropositive regions exposed on the molecular surface of the protein. A few IgE-binding epitopes are coalescent to create more extended IgE-binding regions exposed on the surface of the allergen. Ara h 3 contains a core region corresponding to the cupin motifs and predicted to be preserved upon the trypsin and chymotrypsin attack in the gastro-intestinal tract. Some of the identified IgE-binding epitopes should remain unaltered in the core region to subsequently interact with the local immune system. They most probably account for the strong allergenic potency of Ara h 3. Most of the identified IgE-binding epitopes of Ara h 3 readily differ from the corresponding regions of other legume and tree-nut legumin allergens except for epitope #1 and #7 which are rather conserved essentially in other allergens. These structurally related epitopes could account for some cross-reactions occurring between Ara h 3 and other legumin allergens.