Sensitization to the major allergen of Brazil nut is correlated with the clinical expression of allergy

Background: Only a few studies have investigated the clinical role of food allergens, especially the relationship between sensitization to a given all ergen and occurrence of adverse reactions when eating the relevant food ite m. Objective: This study evaluated the clinical role of the allergens of Brazi l nut by comparing the patterns of IgE binding in sera from II patients wit h anaphylaxis after eating Brazil nuts with those from 10 subjects with no symptoms to this food item. Both groups had specific IgE to Brazil nut. Methods: Allergens in the in-house extract of Brazil nut were identified by SDS-PAGE/immunoblotting, the major allergen was purified by HPLC, and its N-terminal sequence was determined by a protein sequencer. Results: SDS-PAGE/immunoblotting detected a number of allergenic components with molecular weights ranging from 4 to 58 kd. All sera from symptomatic patients recognized a 9-kd allergen corresponding (as established by amino acid sequencing) to a 2S albumin already described as a major allergen of B razil nut, whereas the other allergens each bound IgE from less than 50% of sera. No sera from asymptomatic subjects showed IgE binding to the 9-kd al lergen, but they did recognize components from 25 to 58 kd, which are minor allergens. Conclusions: These findings indicate that the allergen underlying clinical reactions to Brazil nut is a 2S albumin of 9 kd and that in vitro reactivit y to this allergen identifies subjects who react in vivo to ingestion of th is food.