An almond allergen with two known short peptide sequences was reported as the almond 2S albumin but was later suspected to be almond vicilin. However, this allergen was not designated by the World Health Organization/International Union of Immunological Societies. This study aimed to determine the true identity of this elusive almond allergen. cDNAs were synthesized from total RNA of the Nonpareil almond. The complete sequence of the previously reported almond allergen was determined from its coding sequence. The deduced protein was produced recombinantly and was confirmed to be a food allergen by testing with 18 almond-allergic sera. The allergen is a potential cysteine-rich antimicrobial protein with characteristic C[X]3C-[X]10-12-C[X]3C motifs of the hairpinin antimicrobial protein. This first member of a novel family of food allergens was named Pru du 8. The signature motif of the hairpinin antimicrobial protein can be found in the N-terminal region of some vicilin allergens (e.g., Ara h 1). It can also be found in the signal peptide of other vicilin allergens (e.g., Car i 2). In many species, however, vicilins do not contain such a motif, indicating that the presence of the signature motifs of the hairpinin antimicrobial protein in vicilins might be a result of translocation during evolution.
Keywords: Pru du 8; antimicrobial protein; food allergen; serum IgE; α-hairpinin.