The
allergens associated with cashew
food allergy have not been well-characterized. We sought to identify the major
allergens in cashew nut by performing
IgE immunoblots to dissociated and reduced or nonreduced cashew
protein extracts, followed by sequencing of the
peptides of interest. Sera from 15 subjects with life-threatening reactions to cashews and 8 subjects who tolerate cashews but have life-threatening reactions to other tree nuts were compared. An aqueous cashew
protein extract containing
albumin/
globulin was separated by
sodium dodecyl sulfate-
polyacrylamide gel electrophoresis (SDS-PAGE) and subjected to
IgE immunoblotting using patient sera. Selected
IgE reactive bands were subjected to N-terminal
amino acid sequencing. Each of the 15 sera from cashew-allergic subjects showed
IgE binding to the cashew
protein extract. The dominant
IgE-binding
antigens in the reduced preparations included
peptides in the 31-35 kD range, consistent with the large subunits of the major storage 13S
globulin (
legumin-like
protein). Low-molecular-weight
polypeptides of the 2S
albumin family, with similarity to the major walnut
allergen Jug r 1, also bound
IgE. The sera from eight patients who tolerate cashew but displayed
allergies to other tree nuts showed only minimal or no
IgE binding to cashew. Cashew
food allergy is associated with the presence of
IgE directed against the major
seed storage proteins in cashew, including the 13S
globulin (
legumin group) and 2S
albumins, both of which represent major
allergen classes in several plant seeds. Thus, the
legumin-group
proteins and 2S
albumins are again identified as major food
allergens, which will help further research into seed
protein allergenicity.