Cross-reactivity among edible nuts: double immunodiffusion, crossed immunoelectrophoresis and human specitic IgE serologic surveys

Background: As many as one third of all food allergen anaphylactic events are related to tree nut ingestion. Although concurrent allergen sensitivity to tree nuts is common, cross-reactivity among nut antigens is less well defined. Objective: To survey serologic cross-reactivities among 7 tree nuts (walnut, pecan, hazelnut, cashew, Brazil nut, pistachio, and almond) and peanut. Methods: Human specific IgE enzyme-linked immunosorbent assay inhibition was used to identify nut allergen cross-reactivities. Single-nut rabbit antisera were used in double immunodiffusion, crossed-line immunoelectrophoresis, and crossed immunoelectrophoresis with intermediate gel studies of nut antigen cross-reactivity. Results: Nut specific IgE enzyme-linked immunosorbent assay inhibition demonstrated no cross-reactivities between peanut and tree nuts. Among tree nuts, 2 groups with allergen cross-reactivity were defined: (1) walnut, pecan, and hazelnut and (2) hazelnut, cashew, Brazil nut, pistachio, and almond. Double immunodiffusion, crossed-line immunoelectrophoresis, and crossed immunoelectrophoresis with intermediate gel results supported the same groupings of cross-reactive tree nuts and identified several less prominent nut-nut antigen cross-reactivities between groups and with peanut. Conclusion: With few exceptions (notably limited peanut cross-reactivity with pistachio and walnut), peanut antigens did not serologically cross-react with tree nuts. Walnut, pecan, and hazelnut form a group of strongly cross-reactive tree nuts. Hazelnut, cashew, Brazil nut, pistachio, and almond form a group of moderately cross-reactive tree nuts. Cross-reactivities between these groups are less pronounced (notably limited cross-reactivity of walnut and pecan with Brazil nut). The strongest cross-reactivities among tree nuts follow botanical family associations: (1) walnut and pecan in the family Juglandaceae and (2) cashew and pistachio in the family Anacardiaceae.