Diagnosis of soybean-induced asthma

Levels of Airborne Soybean Allergen (Gly m 1) in a Brazilian Soybean Production City: A Pilot Study

Asthma epidemics have been shown to be related to where soybeans are loaded and handled, but data are scarce in the literature. This pilot study evaluated the levels of Gly m 1 in dust samples collected in Maringá, Brazil, a city with high soy production and processing. A dust impactor was used to collect seven isolated samples during 2015 and 2016. Samples were analyzed by an ELISA (enzyme-linked immunosorbent assay) detection method. Gly m 1 was found in all samples, ranging from 0.82-24.38 ng/m3 (median 2.41), regardless of the month or year evaluated. The levels of Gly m 1 were considered low, but the concentrations required to cause sensitization and symptoms are uncertain.

Occupational asthma caused by soybean flour in bakers--differences with soybean-induced epidemic asthma

BACKGROUND

Soybean dust has been identified as the causative agent of occupational asthma and asthma epidemics. Two main soybean hull allergens responsible for asthma outbreaks, Gly m 1 and Gly m 2, have been identified and purified.

OBJECTIVE

The soybean allergens causing occupational asthma in exposed bakers were investigated and compared with those involved in epidemic asthma.

METHODS

We report four bakers or confectioners with work-related respiratory symptoms who were exposed to soybean flour used as a baking additive. The causative role of soybean flour was investigated by immunological tests and specific inhalation challenge tests. Soybean flour allergens causing occupational asthma were characterized by immunoblotting. Immunoglobulin (Ig) E-reactivity to Gly m 1 and Gly m 2 was assessed using enzyme-linked immunosorbent assay.

RESULTS

Sensitization to soybean flour was demonstrated by skin and serological tests and was confirmed by positive inhalation tests. Bronchial challenge test to soybean flour extract elicited immediate or dual asthmatic responses. Immunoblotting with soybean flour and soybean hull extracts showed IgE-binding mainly to high molecular weight (MW) allergens. There was an important individually different allergic response to inhalant soybean components. None of the patients showed IgE-reactivity against Gly m 1 and only one patient showed IgE-reactivity to the soybean hull allergen Gly m 2.

CONCLUSION

These bakery workers had developed IgE-mediated occupational asthma to soybean flour. The allergens involved in occupational asthma caused by soybean flour are predominantly high MW proteins that are present both in soybean hull and flour, and they are different from the allergens causing asthma outbreaks, which are mainly low MW proteins concentrated in the hull.

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 aeroallergens responsible for soybean asthma outbreaks. However, the prevalence of sensitization to SH allergens in subjects from Argentina, a country where soybeans are produced, is unknown.

OBJECTIVE

The purpose of this study was to determine the prevalence of sensitization to SH by in vivo and in vitro tests in subjects with asthma or allergic rhinitis and in control subjects from Argentina who have been exposed 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) urban = urbanized areas without a known source of SDI. Two groups were studied. Group 1 consisted of 365 subjects with asthma or allergic rhinitis and group 2 (control group) of 50 healthy individuals. Subjects from both groups were classified according to their exposure to SDI. All subjects completed standard questionnaires. Prick skin tests (STs) with an SH extract and with common allergens were performed on all subjects. Specific IgE and IgG4 to SH were measured in sera of 51 of 56 subjects from group 1 who had a positive 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 >/=0.5). In group 1, positive STs to SH were 38.7%, 20.3%, and 8.2% in subjects with direct, indirect, and urban exposures, respectively (P <.001). Monosensitization 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 those 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 exclusively sensitized to mites, had a higher frequency of daily or weekly symptoms (59.4% vs 25.7%, respectively, P <.001) and a higher percent of glucocorticoid dependence (52.8% vs 34%, respectively, P <.01). Percent positive IgE in group 1 and group 2 were 39.2% and 10% (P <.001) and percents positive IgG4 are 27.4% and 12%, respectively (not significant). In subjects from 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%, respectively (P < .02). IgG4 in group 1 was significantly higher in subjects with direct exposure compared with subjects with indirect or urban exposure.

CONCLUSION

This study demonstrated that there was (1) a high prevalence of sensitivity to SH in subjects with asthma or allergic rhinitis from Argentina and (2) an association between sensitivity to SH and severity of asthma and level of exposure to SDI.

Long term outcome of soybean epidemic asthma after an allergen reduction intervention

BACKGROUND

Asthma outbreaks due to the inhalation of soybean dust released from handling of soybean in the city harbour occurred in Barcelona, Spain from 1981 to 1987. The installation of bag filters in the responsible silo was followed by a substantial reduction of airborne soybean dust released into the atmosphere and the disappearance of asthma outbreaks. A study was undertaken to assess the relevant outcomes in asthma patients affected by soybean epidemic asthma eight years after this environmental intervention.

METHODS

A repeat case-control study was performed in 1995 on a population of subjects with epidemic and non-epidemic asthma previously assessed in 1989. The same protocol was used in both surveys to collect data from patients via a questionnaire and respiratory function, skin and laboratory tests were performed under blinded conditions with regard to epidemic and non-epidemic status. Environmental soybean allergen in pollution filters was measured by means of a RAST inhibition technique.

RESULTS

During 1995 and 1996 the 24 hour mean airborne levels of soybean allergen on a sample of 39 unloading days (range 31-269 U/m(3)) were systematically below the lowest level ever detected during an epidemic day (1500 U/m(3)). Measurable levels of serum IgE antibodies against soybean were still present in 55% of patients with epidemic asthma compared with 6.0% of those with non-epidemic asthma (p<0.05). These proportions were almost identical to those observed in 1989. The proportion of patients with soybean asthma with symptoms in 1989 who reported the absence of symptoms in 1995 was similar to the control subjects, so most of the relative risks (RRs) of improvement were near to 1. The only statistically significant differences between the two groups were a smaller proportion of patients with epidemic asthma showing improvement in terms of being woken up by attacks of coughing (RR improvement 0.47; 95% CI 0.22 to 0.99) and the need for treatment at the emergency room (RR improvement 0.63; 95% CI 0.41 to 0.96).

CONCLUSIONS

Eight years after a large reduction in the levels of airborne soybean allergen half of the former soybean epidemic asthma patients were still sensitised to soybean. These results indicate an initial improvement in soybean epidemic asthma in the two years following the intervention with no further improvement in subsequent years.

Increased positivity of skin test and allergenic stability of glycerinated soybean hull extracts

BACKGROUND

Results obtained from previous experiences with soybean hull antigens suggest that the addition of glycerine to the extract increases positivity of the skin test.

OBJECTIVE

The purpose of this study was to investigate the effect of this glycerine addition and the influence of different storage temperatures on the potency of soybean hull extracts.

METHODS

Twenty-two asthmatic patients admitted to emergency rooms during one of the soybean-related Barcelona asthma epidemics were evaluated 2 years after the last epidemic for: (1) sensitivity to prick test with glycerinated and non-glycerinated extracts, both fresh and stored at 4 degrees C, - 20 degrees C and - 70 degrees C for 30 days, and (2) specific IgE to a fresh hull extract. All extracts were also studied by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE).

RESULTS

No differences in positivities were detected for prick tests performed the same day of preparation between non-glycerinated (5/22; 22.7%) and glycerinated (4/22; 18.2%) extracts. After 30 days storage, positivities of prick test with non-glycerinated extracts stored at 4 degrees C did not significantly differ from the results obtained on the first day. However, prick tests performed with glycerinated extracts stored for 30 days showed increased positivity for the extracts stored at 4 degrees C (7/22; 31%) (P < 0.05) as well as for those stored at - 20 degrees C and - 70 degrees C (9/22; 40.9%) (P < 0.001). This latter percentage is similar to that of specific immunoglobulin E detected by radioimmunoassay (10/22; 45. 4%). Also, for the glycerinated extracts only, the quantitative response showed an increase in mean diameter of the induration at 30 days at the three temperatures, even though owing to the great standard deviation and limited number of patients, it was only significant for the extract stored at - 20 degrees C (P < 0.01). SDS-PAGE gel densitometry at 30 days demonstrated a loss of protein in the bands with a molecular weight higher than 66.2 kDa for non-glycerinated extracts stored at 4 degrees C.

CONCLUSIONS

The results of this study confirm previous observations with soybean hull allergen extracts and indicate that (1) storage of soybean hull extracts with glycerine addition for 30 days at the concentration studied (1:100 w/v) determines a significant increase in the positivity of skin tests, and (2) glycerine addition stabilizes soybean hull extracts at any of the temperatures studied.

HLA class II genes in soybean epidemic asthma patients

From 1981 to 1987, 26 outbreaks of asthma caused by the inhalation of soybean dust, affecting a total of 688 individuals, were detected in Barcelona, Spain. Because only a small proportion of asthmatic individuals living in Barcelona expressed the epidemic phenotype, it is hypothesized that a genetically determined human leukocyte antigen (HLA) Class II factor could have played a role in the susceptible individuals. Accordingly, we studied the distribution of both HLA-DR and HLA-DQ in soybean epidemic asthmatic patients. An analysis of the HLA-DR and HLA-DQ genes for genetic polymorphisms of the beta 1 chain was done with the polymerase chain reaction (PCR) in 78 soybean epidemic asthma patients, and the findings were compared with those for 67 nonepidemic asthmatic individuals and 168 individuals from the general population. An allelic disequilibrium could be established; the risk of epidemic asthma was particularly associated with the DRB1*13 gene (p value corrected for multiple comparisons < 0.02). The association observed for the DRB1*13 gene was stronger in individuals in the lowest tertile for total IgE, with an estimated risk with a 95% confidence interval (CI), of 14.5 (1.6 to 130.8). The combination of two genes from among the DRB1*05-05, DRB1*05-06, and DRB1*06-06 genes was present in epidemic asthmatic subjects only. No association with an HLA-DQB1 allele could be observed. Genetic predisposition could contribute to the response of some asthmatic patients to exposure to soybean dust, having led to their being affected during the epidemics of asthma in Barcelona.

Identification of IgE-binding components in occupational asthma caused by corn dust

BACKGROUND

There have been some reports of corn dust-induced occupational asthma that suggest nonimmunologic mechanism. In this paper, we present a case of occupational asthma and rhinitis caused by corn dust where bronchoconstriction was induced by an IgE-mediated reaction.

METHODS AND RESULTS

The patient had positive responses to weed and grass pollens as well as corn dust extracts. The bronchoprovocation test elicited an early asthmatic response to corn dust extracts. Serum-specific IgE and IgG4 antibodies to corn dust extracts were detected by enzyme-linked immunosorbent assay (ELISA). In order to identify further the allergenic component of the extracts, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and electroblotting studies were performed. Ten IgE-binding components (9 to 140 kD) were detected within the corn dust extracts.

CONCLUSION

These results suggest that inhalation of corn dust can cause IgE-mediated bronchoconstriction in an exposed worker.

Specific immunoglobulins to soybean hull allergens in soybean asthma

Soybean asthma, which occurred as an epidemic among patients in Barcelona, Spain, is associated with specific IgE to soybean hull allergens. The purpose of this study was to investigate the possible role of specific IgG, IgG subclasses, IgA, and IgM in the pathogenesis of soybean asthma. We studied 3 groups of subjects from Barcelona: group 1, 12 asthmatic epidemic patients; group 2, 23 asthmatic nonepidemic patients; and group 3, 32 nonallergic subjects. Specific IgE was determined by radioimmunoassay and specific IgG, IgG subclasses (1, 2, 3, and 4), IgA, and IgM by amplified enzyme-linked immunosorbent assay. Cross-inhibition studies were performed for specific IgE and IgG4. We partially characterized the soybean hull allergens that bind specific IgE, IgG, and IgG4 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis/Western blot. Percentage of positive results for the assays of the 8 Igs are as follows: for group 1, 100% (IgE), 75% (IgG), 16.6% (IgG1), 8.3% (IgG2), 0% (IgG3), 66.6% (IgG4), 25% (IgA), and 25% (IgM); for group 2, 4.3% were positive for specific IgE only; and for group 3, 0% (IgE), 0% (IgG), 6.2% (IgG1), 9.4% (IgG2), 9.4% (IgG3), 9.4% (IgG4), 6.2% (IgA), and 6.2% (IgM). The correlation between the specific IgE and the other specific Igs was significant between IgE and IgG4 in group 1 only (r = 0.752, p < 0.01). Cross-inhibition studies demonstrated a higher inhibitory capacity for IgG4 than for IgE. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis/ Western blot demonstrates three low molecular weight protein bands that bind specific IgE, IgG, and IgG4. This study suggests that specific IgG4 to soybean hull allergens plays a role in the pathogenesis of soybean asthma and corroborates the role of specific IgE in the same disease.