Identification of the soybean hull allergens responsible for the Barcelonaasthma outbreaks

Background: Soybean hulls were identified as the etiologic agent responsibl e for the asthma outbreaks that occurred in Barcelona and Cartagena, Spain. Objective: To identify the main soybean hull allergens using the sera of 1 8 asthmatic epidemic patients from Barcelona and to compare the results to those previously reported. Methods: Specific IgE to a soybean hull allergen extract was determined by radioimmunoassay and by sodium dodecyl sulfate-p olyacrylamide gel electrophoresis (SDS-PAGE) in a 10-20% Tris-tricine gradi ent gel followed by Western blot. Results: Specific IgE, which was detected in 15 of the 18 (83.3%) sera, indicated two nonoverlapping band patterns o n the SDS-PAGE/Western blot: (1) pattern 1, present in 11 sera, consisted o f three bands with estimated molecular weights (MWs) of 8, 7.5 and 7 kD, wh ich are the MWs described for the allergens Gly m 2, Gly m 1A and Gly m 1B, respectively, and (2) pattern 2, present in 3 sera, consisted of a band wi th an estimated MW of 8.2-8.3 kD and four additional bands in a MW range of 25-36 kD, The remaining positive sera indicated very faint bands. Conclusi ons: This study confirms that soybean hulls contain three main allergens wi th MWs of 8, 7.5 and 7 kD, and indicates additional higher MW allergens, wh ich selectively bind specific IgE of the sera that do not react with the th ree low MW components. This dichotomous and nonoverlapping pattern of aller gen recognition has not been previously described.