An amplified ELISA inhibition method for the measurement of airborne soybean allergens

A rapid test for soy aeroallergens exposure assessment

BACKGROUND

Determining soy aeroallergens levels is extremely important in the assessment of health risks due to these airborne substances. Currently, soy aeroallergens exposure in the environment is monitored using enzyme immunoassays (EIA) which must be evaluated in a specialized laboratory by skilled personnel.

OBJECTIVE

To describe the development and performance of a rapid immunochromatography assay for the detection of soy aeroallergens in environmental samples.

METHODS

A test strip using gold labeled anti-soy hull low molecular weight extract (SHLMWE) antibody for the rapid detection of soy aeroallergens in environmental samples was developed. One hundred nineteen airborne samples were analysed in parallel by the strip assay and the anti-SHLMWE sandwich EIA. The assay results were visually analysed by three independent observers who ranked samples as: -, + or ++. Strips were also scanned and analysed by densitometry.

RESULTS

The rapid test detected a range of concentrations from 6.25 to 25 ng/mL. Agreement in strip assay interpretations between evaluators was substantial (Kappa = 0.63; CI 0.544-0.715). Visual interpretation also gave a good concordance with EIA results, with sensitivity ranging from 77.3 to 100 and specificity from 65 to 83.5 depending on the observer. Furthermore, a strong correlation was observed between densitometry results of strip assay and EIA determinations.

CONCLUSIONS

The strip assay developed is rapid, simple, and sensitive and does not require expensive equipment or specific skills. It has considerable potential in the environmental monitoring field for screening soy aeroallergens levels in port cities where allergen measurements are not currently performed. Due to its simplicity, the test will improve the management of soy allergic patients by controlling environmental allergen exposure without the need for apparatus or skilled personnel.

[Risk management of soybean-related asthma: monitoring and surveillance]

OBJECTIVES

Allergen emissions during soybean unloading operations in the Barcelona harbor have caused asthma epidemics. The present article aimed to describe the surveillance and control measures carried out by the public health services.

METHODS

Data were extracted from control systems from 1999 to 2009, with description of the surveillance schemes for allergen emissions, environmental concentrations (with defined reference levels) and for health.

RESULTS

Of 95 studies of plant emission, four were above the reference levels, and filters were found to be the most likely cause. Mean environmental concentrations were low but were above the reference levels on 13 days; these levels were related to adverse meteorological conditions and incidents in the plants. No health effects were detected in the panel of patients nor epidemic asthma days.

CONCLUSIONS

The system detects incidents and has shown its usefulness in protecting public health.

[Soybean hull unloading in Tarragona (Spain) and asthma outbreak risk]

OBJECTIVES

From 2007 to 2008, 215,000 tons of soybean hull were unloaded in the Port of Tarragona. Soybean hull was identified as the etiologic agent causing bronchial asthma outbreaks. The aim of the present study was to identify the characteristics of soybean unloading, soybean allergen dispersion, and the population risk.

METHODS

Data on soybean hull unloading, carriage and storage, meteorological conditions and the number of emergency room admissions for asthma were recorded. Allergen concentrations were obtained by sampling PM(10) filters retaining particles of less than 10 microns for 24 hours in the atmospheric contamination surveillance stations. Sensitized patients underwent clinical examination consisting of skin prick test, total and specific IgE and immunoblotting to soybean extracts.

RESULTS

Allergen emissions were moderate at one kilometer from the unloading source (above 300 U/m(3) on 3 days, maximum 441 U/m(3)). The protein pattern of hull soybean extracts was similar to that found in asthma epidemics in Barcelona. Ninety-two percent of the patients were sensitized to soybean hull extracts. No asthma epidemic was detected during unloading days. In addition to the low molecular weight soybean proteins identified in previous studies (6 and 14-17 kDa), high molecular weight proteins were found (14-49 kDa).

CONCLUSIONS

There is allergen dispersion at a short distance from the unloading source, posing a risk to sensitized patients. Technical measures are required during soybean hull operations to reduce particle emissions.

Assessment of soy aeroallergen levels in different work environments

BACKGROUND

Airborne soybean hull proteins are known causes of asthma epidemics around harbours and soy processing plants. Soy flour dust proteins may cause occupational allergy in food and feed industries.

OBJECTIVE

To compare enzyme immunoassays (EIAs) for soy hull and soy flour aeroallergens, exposure assessment in various work environments.

METHODS

Airborne dust samples (n=324) from soy unloading and/or processing plants, the animal feed industry and pig stables were analysed by two soy flour assays: one assay for measuring complete soy hull proteins and two assays for measuring the purified low-molecular-weight (LMW) soy hull allergens.

RESULTS

Immunoblotting confirmed strong differences between antibody specificities and soy preparations. The results of the two soy flour assays and the assay for measuring complete soy hull proteins were highly correlated (r>0.85). The two LMW soy hull assays also showed a strong mutual correlation (r=0.91), but much less correlation with assays for measuring soy flour and complete soy hull. The levels of LMW soy hull proteins were the highest at sites of soybean unloading or processing, while soy flour levels were particularly high in the soy and animal feed industry.

CONCLUSIONS

The optimal EIA procedure for soy aeroallergen exposure assessment depends on the type of work environment and the local soy dust composition. Thus, the type of work environment should always be taken into account in future soy allergy studies in order to prevent a possible underestimation of the workers' actual risk of developing soy allergy.

An amplified sandwich EIA for the measurement of soy aeroallergens

BACKGROUND

Soy hull low-molecular-weight (SHLMW) allergens were responsible for the soy asthma epidemics in Barcelona, with one 7.5 kDa protein (Gly m 1) being the main IgE-binding component. The aims of this study were to develop a sensitive sandwich enzyme immunoassay (EIA) using rabbit polyclonal antibodies to measure low levels of SHLMW allergens, and to compare this method with the previously described human IgE EIA-inhibition technique.

METHODS

IgG was isolated from serum of rabbits immunized with a chromatographically purified SHLMW extract (SHLMWE). Antibody-binding profiles were compared with those of human IgE anti-soy protein antibodies by Western blot analysis. An amplified sandwich EIA was developed using the purified SHLMWE as a calibration standard. Results were expressed in nanograms per millilitre. To compare the two assays, 54 air samples were analysed by both methods.

RESULTS

SDS-PAGE of the SHLMWE revealed four bands of 6, 8, 15 and 17 kDa. Gly m 1 in the SHLMWE was identified by fingerprinting. The detection limit of the assay was 40 pg/mL. The two methods correlated well (r=0.89; P<0.001). The allergen concentration was detected in all 54 (100%) samples by the sandwich EIA but in only 37 (68.5%) by the EIA inhibition.

CONCLUSIONS

The amplified sandwich EIA for SHLMW components has a high sensitivity and appeared to be a useful tool for the measurement of airborne SHLMW allergens, even at relatively low concentrations. Moreover, the method uses rabbit antibodies at high dilutions and does not require human sera, with limited availability and quantitative and qualitative pool-to-pool variability.

Epidemic soybean asthma and public health: new control systems and initial evaluation in Barcelona, 1996-98

OBJECTIVE

To evaluate the new measures adopted to control the risks from soybean unloading operations in the Port of Barcelona, after an episode of epidemic asthma in June 1996.

METHODS

After an initial cautionary suspension of all soybean unloading operations, they were subsequently resumed under restrictive criteria for time, flux, simultaneity, and meteorological conditions. Emission filtration systems based on either micro pore size filters or polytetrafluoroethylene membranes on tetratex filters showed promising results.

RESULTS

Allergen emission underwent a very important decrease to levels 95% to 98% lower. Emissions from the two plants with unloading operations are in the same order of magnitude as the processing plant that does not unload soybean. Allergen concentration levels presented fluctuations initially, but the new filters decreased mean values; despite increased unloading, allergen levels did not increase-mean allergen levels on unloading days (67 U/m(3)) and on days without unloading operations (63 U/m(3)) are similar. A panel of patients detected a cluster of increased symptoms during unloading operations on a day with suboptimal meteorological conditions and comparatively low allergen levels (225-415 U/m(3)). Since the June 1996 episode, no further asthma outbreak has been detected.

CONCLUSIONS

The evaluation shows the effectiveness of the new filters in the control of soybean dust emission. With a systematic control programme, industrial soybean operations may function near urban centres without public health risks. These data may be useful in the development of future standards for allergenic agents.

Epidemic asthma in Barcelona: an evaluation of new strategies for the control of soybean dust emission

BACKGROUND

Asthma attacks and mortality due to inhalation of soybean antigens in Barcelona have been well documented. Strict protective measures in the unloading process were established in 1998 to avoid the release of soybean dust into the atmosphere. The present study was undertaken to assess the effectiveness of these latest environmental measures, and, if effective, to recommend their implementation in the many harbours where soybean is unloaded.

METHODS

Levels of soybean aeroallergen were analysed daily during a period of 5 years and 2 months in a total of 1,854 samples, 125 from the pre-intervention period and 1,729 from the postintervention period. Additionally, the number of asthma admissions to the emergency rooms of the city's three largest hospitals was recorded. Asthma patients attended at home by the public home emergency service and judicial autopsies registering asthma deaths were also investigated.

RESULTS

The mean concentration of soybean aeroallergen was 159 U/m(3) in the pre-intervention period and 39 U/m(3) in the postintervention period (p < 0.0001). Significant differences in postintervention aeroallergen concentrations were found between days of soybean unloading (42 U/m(3)) and days of no unloading (33 U/m(3)), with p < 0.0001. No significant relationship was found between concentrations of environmental soybean aeroallergens and the number of emergency room admissions for asthma.

CONCLUSIONS

Implementation of stricter protective measures in silos for the soybean unloading process has reduced the concentration of soybean dust in the atmosphere and evidences the effectiveness of the measures adopted.

An ELISA-based method for measurement of food-specific IgE antibody in mouse serum: an alternative to the passive cutaneous anaphylaxis assay

Passive cutaneous anaphylaxis (PCA) assay has been a gold standard method to measure allergen-specific IgE antibody (ASIgE Ab) levels in allergy mouse models. Many factors including stringent guidelines for laboratory animal use make PCA a difficult choice. Therefore, alternative methods are needed that can be readily applied for measurement of specific IgE antibody levels in mouse serum. Herein we describe a novel ELISA-based method that is more sensitive in comparison to PCA, IgE isotype-specific (because it has little cross-reactivity with IgG1 or IgG2a isotype) and highly reproducible (<10% inter- or intra-assay variation). Furthermore, we demonstrate the utility of this assay to measure specific IgE Ab against a variety of food extracts including chicken egg, peanut, almond, filbert/hazelnut and sweet potato. These findings are of particular interest to those who are seeking (i) to measure food-extract-specific IgE antibody in animal models and (ii) an alternative to the animal-based PCA method to measure mouse IgE antibodies.

A comparative study of the correction of systematic errors in the quantitation of pyrethroids in vegetables using calibration curves prepared using standards in pure solvent

A comparative study of two mathematical approaches was performed in order to correct systematic errors due to the presence of the unexpected interferences which appear when the quantitation of the analyte in real samples is carried out with calibration curves built using standards in pure solvent. These methods consisted in the establishment of different mathematical expressions which transform the concentration (Cs) obtained using calibration graphs built using pure solvent into the corrected concentration (C(M)) that should be obtained if the quantitation is carried out with calibration curves built using standards dissolved in blank matrix extracts. In the two approaches the correction is performed from the results of an intermediate precision study which was carried out using both calibration graphs (prepared using pure solvent and blank matrix extract). By using ANCOVA to compare the slope of both solvent-based and matrix-matched calibration graphs, matrix effect was found in the determination of deltamethrin in tomato and acrinathrin in tomato and pepper. In these cases, both approaches led to good results.