Soybean trypsin inhibitor is an occupational inhalant allergen

Comparison of Various Soybean Allergen Levels in Genetically and Non-Genetically Modified Soybeans

Several analyses of allergen levels have been reported as part of the safety assessment of genetically modified (GM) soybean; however, few comprehensive analyses have included new allergens. Thus, in this study the levels of eight major soybean allergens, including Gly m 7 (a newly reported soybean allergen), were semi-quantitatively detected in six GM soybeans and six non-GM soybeans using antigen-immobilized ELISA and immunoblotting. We also analyzed the IgE-reactivity to these soybeans through immunoblotting, using sera from three soybean-allergic patients. The results showed that there were no significant differences in the levels of the major soybean allergens in the GM and non-GM soybeans. Moreover, there were no significant differences in the serum IgE-reactive protein profiles of the patients, as analyzed using immunoblotting. These results indicate that, in general, CP4-EPSPS-transfected GM soybeans are not more allergenic than non-GM soybeans.

Enhancing online protein isolation as intact species from soy flour samples by actively modulated two-dimensional liquid chromatography (2D-LC)

In this study, an enhanced fully automated approach is described for the protein isolation from soy flour samples by two-dimensional liquid chromatography with active modulation interface. The use of two multi-port switching valves is proposed to on-line connect the first to the second dimension column, thus overcoming the problems associated with the re-mixing effects and incompatibility of eluent composition and pH. A 5-cm long C4 analytical column installed in the interface device allows to focus the proteins coming from the first column (size exclusion chromatography), before their selective elution in the second column (reversed-phase). A trap washing step was included in the total workflow, as a desalting step to remove buffer residues from the eluent of the first column and to enhance the chromatographic performances of the second column. The experimental conditions were optimized by analyses of mixed standard solutions of bovine serum albumin, glucose oxidase, immunoglobulin A, thyroglobulin and myoglobin. Then, the optimized 2D-LC method was applied to the protein analysis in extracts of soy flour, known worldwide as one of the major food allergen sources, with the final aim to recovery sufficient protein amounts for the molecular characterization and the assessment of the pattern of allergenic components.

Combining 2-DE immunoblots and mass spectrometry to identify putative soybean (Glycine max) allergens

Soybean is recognized as a commonly allergenic food, but the identity of important allergens is not well studied. Recently, some global regulatory agencies started requiring quantitative analysis of individual allergens, including unproven allergens, as part of the risk assessment for genetically engineered (GE) soybeans. We sought to identify soybean proteins that bind IgE from any of 10 individual soybean-sensitized subjects. Soybean IgE binding proteins were identified by 2-DE immunoblots using sera from four soy-allergic and plasma from six soy-sensitized human subjects. Corresponding spots were excised from stained gels, digested, and analyzed using a quadrupole TOF Synapt G2-S tandem mass spectrometer. Results showed the major IgE binding proteins were subunits of either β-conglycinin (Gly m 5) or glycinin (Gly m 6). Soybean Kunitz trypsin inhibitor (SKTI) was a significant IgE binding protein for four subjects. Soybean agglutinin, seed biotinylated protein (SBP) of 65 kDa, late embryogenesis protein (LEP), and sucrose-binding protein were identified as IgE binding only for soy-sensitized subjects. We conclude that the major soybean allergens are isoforms of Gly m 5, Gly m 6, and possibly SKTI and that requirements for quantitative measurement of proteins that are not clear allergens is not relevant to safety.

Assessment of endogenous allergenicity of genetically modified plants exemplified by soybean - Where do we stand?

According to EU regulation, genetically modified (GM) plants considered to be allergenic have to be assessed concerning their endogenous allergens before placement on the EU market, in line with the international standards described in Codex Alimentarius. Under such premises, a quantitative relevant increase in allergens might occur in GM plants as an unintended effect compared with conventionally produced crops, which could pose a risk to consumers. Currently, data showing a connection between dose and allergic sensitisation are scarce since the pathophysiological mechanisms of sensitisation are insufficiently understood. In contrast, data on population dose-distribution relationships acquired by oral food challenge are available showing a connection between quantity of allergenic protein consumed and the population of allergic individuals experiencing reactions. Soybean is currently the only recognised allergenic GM food by law for which EFSA has received applications and was therefore taken as an example for defining an assessment strategy. Identification of potential allergens, methodology for quantification as well as risk assessment considerations, are discussed. A strategy is proposed for the identification, assessment and evaluation of potential hazards/risks concerning endogenous allergenicity in food derived from plants developed by biotechnology. This approach could be expanded to other allergenic foods in the future, whenever required.

Protein profile of mature soybean seeds and prepared soybean milk

The soybean (Glycine max (L.) Merrill) is economically the most important bean in the world, providing a wide range of vegetable proteins. Soybean milk is a colloidal solution obtained as water extract from swelled and ground soybean seeds. Soybean proteins represent about 35-40% on a dry weight basis and they are receiving increasing attention with respect to their health effects. However, the soybean is a well-recognized allergenic food, and therefore, it is urgent to define its protein components responsible for the allergenicity in order to develop hypoallergenic soybean products for sensitive people. The main aim of this work was the characterization of seed and milk soybean proteome and their comparison in terms of protein content and specific proteins. Using a shotgun proteomics approach, 243 nonredundant proteins were identified in mature soybean seeds.

Diagnosis and management of grain-induced asthma

Grain-induced asthma is a frequent occupational allergic disease mainly caused by inhalation of cereal flour or powder. The main professions affected are bakers, confectioners, pastry factory workers, millers, farmers, and cereal handlers. This disorder is usually due to an IgE-mediated allergic response to inhalation of cereal flour proteins. The major causative allergens of grain-related asthma are proteins derived from wheat, rye and barley flour, although baking additives, such as fungal α-amylase are also important. This review deals with the current diagnosis and treatment of grain-induced asthma, emphasizing the role of cereal allergens as molecular tools to enhance diagnosis and management of this disorder. Asthma-like symptoms caused by endotoxin exposure among grain workers are beyond the scope of this review. Progress is being made in the characterization of grain and bakery allergens, particularly cereal-derived allergens, as well as in the standardization of allergy tests. Salt-soluble proteins (albumins plus globulins), particularly members of the α-amylase/trypsin inhibitor family, thioredoxins, peroxidase, lipid transfer protein and other soluble enzymes show the strongest IgE reactivities in wheat flour. In addition, prolamins (not extractable by salt solutions) have also been claimed as potential allergens. However, the large variability of IgE-binding patterns of cereal proteins among patients with grain-induced asthma, together with the great differences in the concentrations of potential allergens observed in commercial cereal extracts used for diagnosis, highlight the necessity to standardize and improve the diagnostic tools. Removal from exposure to the offending agents is the cornerstone of the management of grain-induced asthma. The availability of purified allergens should be very helpful for a more refined diagnosis, and new immunomodulatory treatments, including allergen immunotherapy and biological drugs, should aid in the management of patients with this disorder.

Sensitization and symptoms associated with soybean exposure in processing plants in South Africa

BACKGROUND

Following the results of a previous study that highlighted the potential for significant levels of dust exposure in South African soybean processing plants, a clinical investigation was undertaken to study the respiratory health of workers in this industry.

METHODS

Workers from three soybean-processing plants were studied with a respiratory questionnaire and estimation of atopy and specific soybean IgE.

RESULTS

A total of 144 of the 181 (79.6% participation rate) plant employees completed the questionnaire and 136 (75.1%) gave blood samples for analysis of specific IgE. There was a significant association between work-related chest tightness (OR 4.0 [95% CI 1.3-12.6]), work-related nasal symptoms (OR 4.3 [95% CI 1.3-14.6]) and cough or chest tightness after handling soybean (OR 3.6 [95% CI 1.1-11.6]) and soybean sensitization. There was a significant association between current exposure to dust during soybean off-loading and "flu-like" illness (OR 2.7 [95% CI 1.0-7.2]), and cough or chest tightness after such work (OR 7.4 [95% CI 2.4-23.6]). The strongest predictor of work related nasal symptoms was sensitization to soybean, the latter strongly predicted by the presence of atopy (OR 34.7 [95% CI 6.6-182.5]).

CONCLUSIONS

Exposure and sensitization to soybean were associated with the presence of work related symptoms, including flu-like symptoms, cough, chest tightness, and nasal symptoms. The aetiology of these symptoms and more particularly the best intervention strategies require more detailed investigation.

Aeroallergen sensitization in wheezing children from rosario, Argentina

Background

Wheezing is a highly frequent symptom in infants and children. Its major causes are respiratory infections and bronchial asthma. In this context, allergen sensitization plays an important role, and it can be detected by a skin prick test, a safe and effective technique that can be easily performed on any age-group. To assess the prevalence of aeroallergen sensitization in a pediatric population with recurrent episodes of wheezing.

Materials and Methods

Cross-sectional study that evaluated 100 patients, 50 (50%) girls and 50 (50%) boys, from 6 months to 10 years. These children had consulted frequently at the Allergy and Immunology Division of the Eva Perón School Hospital due to recurrent episodes of wheezing. Skin prick test were performed on all of them and also on 20 healthy children.

Results

Overall, 58% of the patients presented sensitization to dust mite, 13% to pollen, 9% to epithelium, 8% to fungi, 6% to cockroach, and 1% to soybean hull. Overall, 60% of the patients were positive to at least one of the extracts, and we observed a significant and gradual increase in the frequency of sensitization in older age-groups (P < 0.005). This increase persisted when analyzing separately the dust mite group and the pollen group. None of the cases presented any adverse local or systemic reaction during the procedure or the following 24 hours after the procedure. The 20 individuals in the control group turned out negative when tested.

Conclusions

This study found high aeroallergen sensitization prevalence in a pediatric population with recurrent episodes of wheezing examined in the Allergy and Immunology Division of the Eva Perón School Hospital, which is in the southern area of the province of Santa Fe in Argentina.

Occupational sensitization to soy allergens in workers at a processing facility

BACKGROUND

Exposure to soy antigens has been associated with asthma in community outbreaks and in some workplaces. Recently, 135 soy flake processing workers (SPWs) in a Tennessee facility were evaluated for immune reactivity to soy. Allergic sensitization to soy was common and was five times more prevalent than in health care worker controls (HCWs) with no known soy exposure.

OBJECTIVE

To characterize sensitization to soy allergens in SPWs.

METHODS

Sera that were positive to soy ImmunoCAP (n=27) were tested in IgE immunoblots. Wild-type (WT) and transgenic (TG) antigens were sequenced using nanoscale Ultra-Performance Liquid Chromatography Tandem Mass Spectrometry (nanoUPLC MS/MS). IgE reactivity towards 5-enolpyruvylshikimate-3-phosphate synthase (CP4-EPSP), a protein found in TG soy, was additionally investigated. De-identified sera from 50 HCWs were used as a control.

RESULTS

Immunoblotting of WT and TG soy flake extracts revealed IgE against multiple soy antigens with reactivity towards 48, 54, and 62 kDa bands being the most common. The prominent proteins that bound SPW IgE were identified by nanoUPLC MS/MS analysis to be the high molecular weight soybean storage proteins, β-conglycinin (Gly m 5), and Glycinin (Gly m 6). No specific IgE reactivity could be detected to lower molecular weight soy allergens, Gly m 1 and Gly m 2, in soybean hull (SH) extracts. IgE reactivity was comparable between WT and TG extracts; however, IgE antibodies to CP4-EPSP could not be detected.

CONCLUSIONS AND CLINICAL RELEVANCE

SPWs with specific IgE to soy reacted most commonly with higher molecular weight soybean storage proteins compared with the lower molecular weight SH allergens identified in community asthma studies. IgE reactivity was comparable between WT and TG soy extracts, while no IgE reactivity to CP4-EPSP was observed. High molecular weight soybean storage allergens, Gly m 5 and Gly m 6, may be respiratory sensitizers in occupational exposed SPWs.

Natural variability in abundance of prevalent soybean proteins

Soybean is an inexpensive source of protein for humans and animals. Genetic modifications (GMO) to soybean have become inevitable on two fronts, both quality and yield will need to improve to meet increasing global demand. To ensure the safety of the crop for consumers it is important to determine the natural variation in seed protein constituents as well as any unintended changes that may occur in the GMO as a result of genetic modification. Understanding the natural variation of seed proteins in wild and cultivated soybeans that have been used in conventional soybean breeding programs is critical for determining unintended protein expression in GMO soybeans. In recent years, proteomic technologies have been used as an effective analytical tool for examining modifications of protein profiles. We have standardized and applied these technologies to determine and quantify the spectrum of proteins present in soybean seed. We used two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), and liquid chromatography mass spectrometry (LC-MS) for the separation, quantification, and identification of different classes of soybean seed proteins. We have observed significant variations in different classes of proteins, including storage, allergen and anti-nutritional protein profiles, between non-GMO cultivated and wild soybean varieties. This information is useful for scientists and regulatory agencies to determine whether the unintended expression of proteins found in transgenic soybean is within the range of natural variation.

Advantages of the lab-on-a-chip method in the determination of the kunitz trypsin inhibitor in soybean varieties

Qualitative and quantitative determination of the Kunitz trypsin inhibitor (KTI) in soybean experimental lines is very important in processes of selecting and breeding of new varieties. The total enzyme activity assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and Lab-on-a-Chip (LoaC) method were used for the determination of the presence and quantity of KTI in 15 soybean experimental lines and varieties. From the total trypsin inhibitor enzyme assay, inhibitor activities were registered in all samples, even in a Kunitz variety that was a negative control. The SDS-PAGE method did not detect the presence of the KTI protein band in seven soybean experimental lines and Kunitz variety, while the LoaC method showed the absence of KTI only in the Kunitz variety sample. Results confirmed the superiority of the LoaC method over other two methods in selectivity and sensitivity when KTI determination is concerned. Relationships between the KTI content obtained by the LoaC method and total trypsin inhibitor enzyme activity were established and statistically confirmed.

Utility of proteomics techniques for assessing protein expression

Proteomic technologies are currently used as an effective analytical tool for examining modifications in protein profiles. Understanding the natural variation of soybean seed proteins is necessary to evaluate potential unintended (collateral) effects due to transgenic modifications in genetically modified (GMO) soybeans. We used two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry, and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) to separate, identify and quantify the different classes of soybean seed proteins. Sixteen soybean genotypes, including four wild and twelve cultivated genotypes, belonging to four different subgroups were used as models for protein profile evaluation. Significant variations of allergen and anti-nutritional protein profiles were observed between two different groups, cultivated and wild soybean genotypes. However, only minor variations in protein profiles were observed within the soybean samples from the same group (cultivated or wild). These results may be useful to scientists needing to compare GMO and non-GMO soybeans once additional data are generated on additional soybean varieties and the same varieties grown at different geographical locations.

Inhalable dust and protein exposure in soybean processing plants

Little is known about inhalable dust concentrations in soybean processing plants in southern Africa. This project measured inhalable dust in soybean plants in the region and correlated dust measurements with total protein and soy trypsin inhibitor. Sixty-four personal inhalable dust measurements were taken in three processing plants. Levels of total protein and soy trypsin inhibitor were determined in only two of the three plants. Correlations between inhalable dust, total protein and trypsin inhibitor were determined for 44 of 64 samples. In plants' production areas, inhalable dust levels were 0.24-35.02 mg/m3 (median 2.58 mg/m3). Total protein and soy trypsin inhibitor levels were 29.41-448.82 microg/m3 (median 90.09 microg/m3) and 0.05-2.58 microg/m3 (median 0.07 microg/m3), respectively. No statistically significant correlations between presence of inhalable dust and soy trypsin inhibitor were found. Total protein and soy trypsin inhibitor were better correlated. This study indicates that total protein might be a good proxy for soybean specific protein concentrations in soybean processing plants.

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.

Allergenicity of soybean: new developments in identification of allergenic proteins, cross-reactivities and hypoallergenization technologies

Soybean is considered one of the "big eight" foods that are believed to be responsible for 90% of all allergenic reactions. Soy allergy is of particular importance, because soybeans are widely used in processed foods and, therefore, represent a particularly insidious source of hidden allergens. Although significant advances have been made in the identification and characterization of soybean allergens, scientists are not completely certain about which proteins in soy cause allergic reactions. At least 16 allergens have been identified. Most of them, as with other plant food allergens, have a metabolic, storage, or protective function. These allergens belong to protein families which have conserved structural features in relation with their biological activity, which explains the wide immunochemical cross-recognition observed among members of the legume family. Detailed analysis of the structure-allergenicity relationships has been hampered by the complexity and heterogeneity of soybean proteins. A variety of technological approaches have been attempted to decrease soybean allergenicity. This paper provides a comprehensive review of the current body of knowledge on the identification and characterization of soybean allergens, as well as an update on current hypoallergenization techniques.

Investigation on possible allergenicity of 19 different commercial enzymes used in the food industry

The aim of the study was to investigate the safety to allergic patients of 19 commercially available and authority-approved enzymes used in the food industry. Enzymes produced by genetically modified organisms were included. Four hundred consecutive adult patients with a diagnosed allergy to inhalation allergens, food allergens, bee or wasp were included. All had at least one positive skin prick test to the above allergens. Skin prick testing with the 19 enzymes was performed on the forearm and if positive (in 13 patients), in vitro histamine release from blood basophils were performed. Patients with positive results in skin prick test were subsequently reinvestigated with further purified enzymes and finally challenged orally with the enzymes in a double-blind, placebo-controlled protocol. Only one reaction to a placebo challenge was seen. In some instances a positive skin prick test result or a positive histamine release was seen elicited by the enzymes, but since none of the patients were positive to any of the commercial enzymes in the subsequent oral challenges using exaggerated dosages of the enzymes compared to normal daily intake, the findings are without clinical relevance. A wide variety of enzyme classes and origins was included in the study. Because there were no allergenic findings of clinical relevance it is concluded that ingestion of food enzymes in general is not considered to be a concern with regard to food allergy.

A systematic proteomic study of seed filling in soybean. Establishment of high-resolution two-dimensional reference maps, expression profiles, and an interactive proteome database

A high-throughput proteomic approach was employed to determine the expression profile and identity of hundreds of proteins during seed filling in soybean (Glycine max) cv Maverick. Soybean seed proteins were analyzed at 2, 3, 4, 5, and 6 weeks after flowering using two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. This led to the establishment of high-resolution proteome reference maps, expression profiles of 679 spots, and corresponding matrix-assisted laser desorption ionization time-of-flight mass spectrometry spectra for each spot. Database searching with these spectra resulted in the identification of 422 proteins representing 216 nonredundant proteins. These proteins were classified into 14 major functional categories. Proteins involved in metabolism, protein destination and storage, metabolite transport, and disease/defense were the most abundant. For each functional category, a composite expression profile is presented to gain insight into legume seed physiology and the general regulation of proteins associated with each functional class. Using this approach, an overall decrease in metabolism-related proteins versus an increase in proteins associated with destination and storage was observed during seed filling. The accumulation of unknown proteins, sucrose transport and cleavage enzymes, cysteine and methionine biosynthesis enzymes, 14-3-3-like proteins, lipoxygenases, storage proteins, and allergenic proteins during seed filling is also discussed. A user-intuitive database (http://oilseedproteomics.missouri.edu) was developed to access these data for soybean and other oilseeds currently being investigated.

Effect of cultivar and growing location on the trypsin inhibitors, tannins, and lectins of common beans (Phaseolus vulgaris L.) grown in the semiarid highlands of Mexico

Trypsin inhibitors (TI), tannins, and lectins appear to have a role in preventing chronic diseases in humans. The genetic variability of these traits in common bean needs to be ascertained in order to increase levels through breeding. The variability of TI, tannin, and lectins was determined in five bean cultivars grown at five locations in Mexico. TI and tannins contents in colored beans that belong to the Jalisco race were higher (11.1-11.9 trypsin units inhibited (TUI)/mg and 29.0-38.1 mg catechin equivalent (CE)/g, respectively) than cultivars of the Durango race (7.9-8.3 TUI/mg and 16.8-19.9 CE/mg, respectively). Bayo Victoria, a Durango race cultivar, had three times more lectins than levels reported for soybean. Cultivar influenced TI and tannins contents (p < 0.001), whereas site affected lectins (p < 0.001). An increase in levels of TI and tannins could be enhanced through breeding.

Occupational asthma caused by soybean hull: a workplace equivalent to epidemic asthma

A case showing that soya hull exposure at work causes occupational asthma without flour-related bronchoconstriction.