Cloning and characterization of a novel peanut allergen Ara h 3 isoform displaying potentially decreased allergenicity

Peanut allergy is one of the most serious food allergies. The major peanut allergens are designated Ara h 1, Ara h 2 and Ara h 3. A previously unidentified ara h 3-related cDNA, ara h 3-im, was isolated and its corresponding protein product confirmed in peanut seed by N-terminal sequencing. Ara h 3-im is distinct from other related allergens in having a novel N-terminal sequence, lacking two potential N-glycosylation sites, missing most of the fourth IgE-binding epitope found in Ara h 3, and having a different predicted three-dimensional structure. Immunoblotting showed that the 36 kDa Ara h 3-im polypeptide was not recognized by IgE from the sera of peanut sensitive patients that recognized other major peanut allergen polypeptides. ara h 3-im is a new peanut arachin gene that encodes an expressed protein in peanut seed, Ara h 3-im, that shares features with other 11S globulin genes. Initial results indicate that Ara h 3-im has potentially lower allergenic properties than previously characterized peanut allergens which may aid in the production of a hypoallergenic peanut.