Sensitization to soybean hull allergens in subjects exposed to different levels of soybean dust inhalation in Argentina

Background: Soybean hulls (SHs) have been identified as the source of aeroa llergens responsible for soybean asthma outbreaks. However, the prevalence of sensitization to SH allergens in subjects from Argentina, a country wher e soy beans are produced, is unknown. Objective: The purpose of this study was to determine the prevalence of sen sitization to SH by in vivo and in vitro tests in subjects with asthma or a llergic rhinitis and in control subjects from Argentina who have been expos ed to different levels of soybean dust inhalation (SDI), Methods: Exposure to SDI is defined as follows: (1) direct = occupational, (2) indirect = proximity to soybean fields or grain elevators, and (3) urba n = urbanized areas without a known source of SDI, Two groups were studied. Group 1 consisted of 365 subjects with asthma or allergic rhinitis and gro up 2 (control group) of 50 healthy individuals. Subjects from both groups w ere classified according to their exposure to SDI, All subjects completed s tandard questionnaires. Prick skin tests (STs) with an SH extract and with common allergens were performed on all subjects. Specific IgE and IgG4 to S H were measured in sera of 51 of 56 subjects from group 1 who had a positiv e ST to SH and in all sera from group 2. Results: Fifty-six (15.3%) subjects from group 1 and no subjects from group 2 had a positive ST to SH (wheal SH/wheal histamine greater than or equal to 0.5). In group 1, positive STs to SH were 38.7%, 20.3%, and 8.2% in subj ects with direct, indirect, and urban exposures, respectively (P < .001). M onosensitization to SH is absent in all subjects from group 1, The percent of subjects with positive STs to mites, pollen, and molds was highest in th ose with a positive ST to SH versus those with a negative ST to SH (P < .01 ), Asthmatic patients with a positive ST to SH, compared with those exclusi vely sensitized to mites, had a higher frequency of daily or weekly symptom s (59.4% vs 25.7%, respectively, P < .001) and a higher percent of glucocor ticoid dependence (52.8% vs 34%, respectively, P < .01). Percent positive I gE in group 1 and group 2 were 39.2% and 10% (P < .001) and percents positi ve IgG 1 are 27.4 % and 12%, respectively (not significant). In subjects fr om group 1 and group 2 with direct exposure percents positive IgE are 58.3% and 13.3% (P < .001) and percents positive IgG4 were 75% and 20%, respecti vely (P < .02). IgG4 in group I was significantly higher in subjects with d irect exposure compared with subjects with indirect or urban exposure. Conclusion: This study demonstrated that there was (1) a high prevalence of sensitivity to SII in subjects with asthma or allergic rhinitis from Argen tina and (2) an association between sensitivity to SII and severity of asth ma and level of exposure to SDI.