Molecular cloning and epitope analysis of the peanut allergen Ara h 3

Peanut allergy is a significant IgE-mediated health problem because of the increased prevalence, potential severity, and chronicity of the reaction. F ollowing our characterization of the two peanut allergens Ara h 1 and Am h 2, we have isolated a cDNA clone encoding a third peanut allergen, Ara h 3. The deduced amino acid sequence of Ara h 3 shows homology to 11S seed-stor age proteins. The recombinant form of this protein was expressed in a bacte rial system and was recognized by serum IgE from similar to 45% of our pean ut-allergic patient population. Serum IgE from these patients and overlappi ng, synthetic peptides were used to map the linear, IgE-binding epitopes of Ara h 3. Four epitopes, between 10 and 15 amino acids in length, were foun d within the primary sequence, with no obvious sequence motif shared by the peptides. One epitope is recognized by all Ara h 3-allergic patients. Muta tional analysis of the epitopes revealed that single amino acid changes wit hin these peptides could lead to a reduction or loss of IgE binding. By det ermining which amino acids are critical for IgE binding, it might be possib le to alter the Ara h 3 cDNA to encode a protein with a reduced IgE-binding capacity. These results will enable the design of improved diagnostic and therapeutic approaches for food-hypersensitivity reactions.