Ana o 1, a cashew (Anacardium occidental) allergen of the vicilin seed storage protein family.

BACKGROUND The allergens responsible for cashew food allergy have not been well characterized. OBJECTIVES We initiated a study to clone cDNAs encoding cashew food allergens. METHODS A cashew cDNA library was screened with human serum for IgE-reactive clones and rabbit IgG anti-cashew extract antisera. Reactive clones were sequenced and expressed, and linear epitopes were identified by means of solid-phase overlapping peptide analysis. Immunoblot inhibition was used to identify the native peptide in cashew extract. RESULTS Four closely related clones reactive with both human and rabbit antisera were sequenced. Sequence analysis showed that these encode members of the vicilin/sucrose-binding protein family of plant seed storage proteins. Screening of the recombinant protein with sera from 20 patients with cashew allergy and 8 cashew-tolerant patients with allergies to other tree nuts showed that 50% and 25% of sera from patients with cashew allergy and cashew-tolerant subjects, respectively, bound the recombinant protein. The corresponding native allergen protein, designated Ana o 1, was located at approximately 50 kd. Epitope mapping revealed 11 linear IgE-binding epitopes, of which 3 appear to be immunodominant. None of the epitopes were shared in common with those of the peanut vicilin allergen Ara h 1. CONCLUSION Ana o 1, a vicilin-like protein, is a major food allergen in cashews. Cashew and peanut vicilins do not share linear epitopes.