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

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Update of the S2k guideline on the management of IgE-mediated food allergies

Not available.

Allergen component analysis as a tool in the diagnosis and management of occupational allergy

We are now in the epoch of "molecular allergology" and numerous clinically relevant allergenic molecules are available improving the performance of in vitro allergen tests and allergen detection methods. This review is focusing on characterized occupational allergens and their implementation into the in vitro diagnosis for occupational allergy and in allergen detection methods. More than 400 occupational agents are identified and documented as being 'respiratory sensitizers', but currently only a limited number of them are characterized on the molecular level and available for routine diagnosis as native or recombinant allergens. One exception, however, is natural rubber latex (NRL) from Hevea brasiliensis still remaining an important occupational allergen source. Characterization of 15 NRL allergens led to the development of assays for the determination of allergen content of NRL materials and the implementation of component-resolved diagnosis (CRD) for specific IgE antibody measurement. Microarray or singleplex using recombinant or native allergens are reliable tools for NRL allergy diagnosis. In addition, NRL allergy is an excellent model for improving extract-based specific IgE measurement by amplification of NRL extract preparation with stable recombinant major allergen rHev b 5. Despite the many efforts to characterize the occupationally relevant wheat allergens for baker's asthma, the most frequently occurring forms of occupational asthma, the results are highly diverse. Wheat sensitization profiles of bakers showed great interindividual variability and no wheat allergen could be classified as the major allergen. For diagnosis of baker's asthma, a whole wheat extract is still the best option for specific IgE determination. But single wheat allergens might help to discriminate between wheat-induced food allergy, grass pollen allergy and baker's asthma. For workplace-related allergens like coffee, wood, soybean, seafood and moulds allergens are characterized and few of them are available, but their relevance for occupational sensitization routes should be verified in the further studies.

Addressing Molecular Diagnosis of Occupational Allergies

PURPOSE OF REVIEW

Numerous clinically relevant allergenic molecules enhance the performance of specific (s) IgE tests and improve the specificity of allergy diagnosis. This review aimed to summarize our current knowledge of the high-molecular-weight allergens involved in the development of occupational asthma and rhinitis and to critically analyze the contribution of component-resolved diagnosis in the management of these conditions.

RECENT FINDINGS

There is a lack of standardization and validation for most available extracts of occupational agents, and assessment of sIgE reactivity to occupational allergen components has been poorly investigated, with the notable exception of natural rubber latex (NRL) and wheat flour. In the case of NRL, the application of recombinant single allergens and amplification of natural extracts with stable recombinant allergens improved the test sensitivity. IgE-sensitization profile in patients with baker's asthma showed great interindividual variation, and extract-based diagnostic is still recommended. For other occupational allergens, it remains necessary to evaluate the relevance of single allergen molecules for the sensitization induced by occupational exposure. Progress has been made to characterize occupational allergens especially NRL and wheat, although there is still an unmet need to increase the knowledge of occupational allergens, to include standardized tools into routine diagnostic, and to evaluate their usefulness in clinical practice.

Rare and new occupational inhalant allergens

Occupational airway diseases induced by the inhalation of allergens at workplaces have become common, but the inducing substances are diverse and their pathomechanisms are not always clear. Only few allergens were studied in detail (like wheat flour dust and natural rubber latex) and most of the occupational airway sensitizers were documented only as case reports. In this review rare and exotic occupational Type I-aeroallergens according to their workplace application area (e.g., production of dough and bakery products, handling with decorative and economic plants, wood processing, fish-, shellfish-processing and fish breeding) are described.

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.

[Workplace-related respiratory allergies. Current developments]

It is common that the inhalation of occupational allergens induces occupational airway diseases, but the inducers are diverse and complex, and the pathomechanism of the disease is not clear in every case. Only few allergens have been studied in detail (e.g., wheat flour and natural rubber latex), and most of the occupational airway sensitizers have only been documented as case reports. This review describes occupational type I aeroallergens according to their source (plant, animal, microbial, and chemical) and workplace application area. New aspects on the diagnosis and legal preventive regulations for occupational allergic airway diseases are described.

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.

Occupational asthma: etiologies and risk factors

The purpose of this article is to critically review the available evidence pertaining to occupational, environmental, and individual factors that can affect the development of occupational asthma (OA). Increasing evidence suggests that exploration of the intrinsic characteristics of OA-causing agents and associated structure-activity relationships offers promising avenues for quantifying the sensitizing potential of agents that are introduced in the workplace. The intensity of exposure to sensitizing agents has been identified as the most important environmental risk factor for OA and should remain the cornerstone for primary prevention strategies. The role of other environmental co-factors (e.g., non-respiratory routes of exposure and concomitant exposure to cigarette smoke and other pollutants) remains to be further delineated. There is convincing evidence that atopy is an important individual risk factor for OA induced by high-molecular-weight agents. There is some evidence that genetic factors, such as leukocyte antigen class II alleles, are associated with an increased risk of OA; however, the role of genetic susceptibility factors is likely to be obscured by complex gene-environment interactions. OA, as well as asthma in general, is a complex disease that results from multiple interactions between environmental factors and host susceptibilities. Determining these interactions is a crucial step towards implementing optimal prevention policies.

Tolerance mechanisms in response to antigens responsible for baker's asthma in different exposed people

BACKGROUND

Baker's asthma is among the most common occupational disease. The risk factors and immune features that may be important as predictors of tolerance or development of the disease are not completely understood.

OBJECTIVE

To study the evolution over time of antigenic reactivity on baker's asthma in Spain and in France, in order to find differences in their allergenic response and evidence of protective or risks mechanisms against this disease.

METHODS

Two groups of subjects were randomly selected. A group of bakers with asthma from Spain and a second group from France whose blood was taken 30 years ago: bakers with asthma, bakers without occupational respiratory allergy, and wives and children living close to the bakery. In all subjects skin tests were carried out with cereals, insects and the most common allergens in their area. Specific IgE, IgG(4) and IL 10 measurement were also determined.

RESULTS

Spanish patients were mainly sensitized to cereal allergens and presented higher levels of IgE (p < 0.001). French patients are more often sensitised to insects than the Spanish ones: 5.26% versus 80% (p < 0.005). Symptom free or without aggravation at work subjects have higher specific IgG(4) and IL 10 levels than the others (p < 0.01).

CONCLUSIONS

Antigens implicated in baker's asthma may change with time. The presence of higher levels of IgG(4), IL10 and diversity of sources of sensitisation in French patients may have helped them to develop a kind of natural hyposensitization.

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.

Allergic reactions to foods by inhalation

Although allergic reactions to foods occur most commonly after ingestion, inhalation of foods can also be an underlying cause of these reactions. For example, published reports have highlighted the inhalation of allergens from fish, shellfish, seeds, soybeans, cereal grains, hen's egg, cow's milk, and many other foods in allergic reactions. Symptoms have typically included respiratory manifestations such as rhinoconjunctivitis, coughing, wheezing, dyspnea, and asthma. In some cases, anaphylaxis has been observed. In addition, there have been many investigations of occupational asthma following the inhalation of relevant food allergens. This report reviews the current literature focusing on allergic reactions to foods by inhalation.

Bronchial responsiveness to bakery-derived allergens is strongly dependent on specific skin sensitivity

BACKGROUND

Quantitative relationships between immunological reactivity, non-specific bronchial responsiveness and bronchial responsiveness to allergens have scarcely been investigated in occupational asthma.

METHODS

We assessed the above relationships in 24 subjects with baker's asthma. The skin endpoint titration to bakery allergens as a measure of immunological reactivity, together with the methacholine PC20 and allergen PC20 during early asthmatic reaction were determined.

RESULTS

All patients had positive skin tests to some bakery allergens (wheat and rye flour, soybean flour, fungal enzymes and egg white proteins) and bronchial hyperresponsiveness to methacholine. Specific inhalation challenge (SIC) tests were performed with aqueous allergen extracts of cereal flour (n = 14), soybean (n = 8), baking enzymes (n = 12), and egg white proteins (n = 8) in sensitized workers. A positive asthmatic reaction was observed in 84% of the inhalation challenges. SIC elicited isolated early asthmatic reactions in 62%, dual reactions in 32% and isolated late reactions in 5%. Multiple linear regression analysis showed allergen PC20 as a function of skin sensitivity to allergen and methacholine PC20, yielding the following highly significant regression formula: log-allergen PC20 = 0.18 + 0.99 log(skin sensitivity) + 0.343 log(methacholine PC20) (r = 0.89, P < 0.001). This formula predicted allergen PC20 to within one double concentration in 67%, to within two double concentrations in 85% and within three double concentrations in 97%.

CONCLUSION

The main determinant of bronchial responsiveness to allergen in patients with baker's asthma is the degree of sensitization to occupational allergens as determined by skin reactivity, modulated to a lesser extent by non-specific bronchial hyperresponsiveness.

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.

Occupational asthma due to chromium and nickel salts

BACKGROUND

Exposure to chromium and nickel salts is a poorly characterized cause of occupational asthma.

METHODS

We describe four patients with work-related asthma due to metallic salts. Skin-prick tests to potassium dichromate and nickel sulfate were performed. The patients underwent methacholine inhalation tests and specific inhalation challenges (SIC) with both chromium and nickel salts.

RESULTS

Two patients showed positive skin-prick tests to potassium dichromate and nickel sulfate. All patients had bronchial hyperresponsiveness to methacholine, which increased 24 h after SIC with metallic salts. SIC with potassium dichromate elicited late asthmatic reactions (LAR) in two workers, one subject had an early asthmatic reaction (EAR), and another subject showed a dual asthmatic reaction (DAR). SIC with nickel sulfate induced a DAR in one subject and a late asthmatic reaction in another.

CONCLUSIONS

Chromium and nickel salts can give rise to occupational asthma in exposed workers. The underlying mechanism may be IgE-mediated in some cases.

Occupational exposures as triggers of asthma

The prevalence of occupational asthma is rising, possibly due to the introduction of different chemicals and substances in the workplace. Etiologic agents include organic and inorganic compounds that are encountered in a variety of industries. Early diagnosis, adequate management of inflammation, and prevention of further exposure are essential to occupational asthma management. Reducing complications and disability while providing work rehabilitation should be the ultimate goal of the health care provider. This article discusses these issues and gives guidance to the clinician treating patients with possible occupational asthma.

Clinical value and measurement of specific IgE

The diagnosis of human allergic diseases involves the combined use of a careful clinical history, physical examination, and in vitro and in vivo assay methods for the detection of IgE antibodies of defined allergen specificities. In vivo (skin testing) and in vitro (measurement of specific IgE in serum) techniques cannot be considered interchangeable, the former reflecting not only the presence of IgE but also mast cell integrity, vascular and neural responsiveness. Both techniques have similarities and differences, advantages and disadvantages. Recently introduced "second generation" immunoassays have continued to improve the analytical sensitivity and reproducibility thanks to automation and improved reagent quality. Quantitative assays may allow the use of specific clinical thresholds able to differentiate symptomatic from asymptomatic patients. False-negative and false-positive results should derive from lability of some major extracts, and from possible cross-reactivities, respectively. Characterization of allergens at a molecular and submolecular level and, where necessary, the use of recombinant allergens can reduce cross-reactions and further improve the quality of immunoassays.

Egg white proteins as inhalant allergens associated with baker's asthma

BACKGROUND

Bakery workers may develop IgE-mediated allergy to liquid and aerosolized hen's egg proteins that are commonly used in the baking and confectionery industries.

METHODS

We studied four bakery workers who had work-related allergic respiratory symptoms upon exposure to egg aerosols. The causative role of egg proteins in their respiratory symptoms was investigated by immunologic and specific inhalation challenge (SIC) tests.

RESULTS

Skin prick tests to egg white extract and to lysozyme gave positives responses in all the subjects, to ovalbumin in two, to ovomucoid in one and to egg yolk in two subjects. They were also sensitized to wheat, rye and barley flours. Specific IgE determinations to egg white were positive in all patients, to lysozyme in two, to ovalbumin in three, to ovomucoid in two and to egg yolk in two of them. Methacholine inhalation tests revealed bronchial hyperresponsiveness in all workers (PC20 < 16 mg/ml). SICs were performed with aqueous extracts of lysozyme (n = 4), ovalbumin (n = 2) and ovomucoid (n = 1), which elicited isolated early asthmatic reactions in all subjects. Double-blind, placebo-controlled, oral challenge tests with raw egg white were positive in three subjects.

CONCLUSIONS

These bakery workers had developed IgE-mediated occupational asthma to hen's egg white proteins.

Specific immunotherapy with a standardized latex extract in allergic workers: a double-blind, placebo-controlled study

BACKGROUND

Preventive measures have been proposed to reduce the risk of sensitization to natural rubber latex (NRL), but this is not always feasible.

OBJECTIVE

The aim of this study was to determine the efficacy and safety of specific immunotherapy with a standardized latex extract in sensitized workers.

METHODS

Twenty-four patients allergic to NRL with contact urticaria (n = 8) and rhinitis or asthma (n = 16) were included (16 in the active group and 8 in the placebo group). Treatment started in a cluster immunotherapy protocol, with injections every week for 3 months and then every other week for another 3 months.

RESULTS

Patients in the active group had significantly lower values than patients in the placebo group in skin terms of reactivity to NRL (P <.01), rubbing test results (P =.047), and latex glove use test results (P =.046) after 6 months of treatment. There were no significant differences between the active and placebo groups in symptom scores, use of medication, self-assessment, or methacholine test results either before or after treatment. Differences in nasal and bronchial symptoms during specific inhalation challenges (P = not significant and P =.05, respectively) were observed in favor of the active group. In the active group 32 systemic reactions were observed (8% of doses), mostly during the build-up period, being more frequent in patients with respiratory symptoms (P =.004). All reactions responded promptly to treatment.

CONCLUSION

Clinical efficacy was shown mainly on cutaneous symptoms, although an improvement in rhinitis and asthma symptoms was also observed during specific inhalation challenges. Latex-specific immunotherapy might be a useful approach for the treatment of latex allergy in sensitized workers.

Occupational asthma caused by high-molecular-weight substances

More than 250 agents that are encountered in the workplace have been shown to induce asthma in susceptible individuals. It is estimated that 2% to 15% of cases of asthma may be occupational. High-molecular-weight substances, such as plant and animal proteins, enzymes, and large carbohydrate molecules, can induce IgE-mediated occupational asthma. The incidence of disease varies among industries and is dependent on the physiochemical properties of the agent, the level and duration of exposure, industrial hygiene, engineering practices, and host factors. Risk factors, common high-molecular-weight workplace antigens, diagnosis, treatment, and prognosis are discussed.

Quantified environmental challenge with absorbable dusting powder aerosol from natural rubber latex gloves

BACKGROUND

There are few data that link quantified natural rubber latex (NRL) absorbable dusting powder aerosol to biologic responses in NRL-sensitized subjects.

METHODS

We conducted a study on 30 health care workers with possible occupational asthma. All the subjects but 2 had a positive skin prick test result with NRL extract. Quantified environmental challenge (QEC) with powdered NRL gloves was performed in a 7-m(3) chamber. The patients would don and discard a pair of gloves every 3 minutes up to a maximum of 60 minutes. The concentrations of NRL aeroallergen were measured by a competitive IgE immunoassay. Ocular and respiratory symptoms and pulmonary function were monitored.

RESULTS

Twenty-six patients (87%) had rhinoconjunctivitis, 19 (63%) had an asthmatic response (responders), and 1 patient developed eosinophilic bronchitis on QEC. The asthmatic responses were of the early type in 15 patients, dual in 3, and isolated late in 1 patient. The duration of exposures sufficient to elicit asthmatic responses varied from 3 to 114 cumulative minutes. Time-weighted average NRL aeroallergen concentrations during QEC with responders ranged between 199 and 1107 ng/m(3). NRL concentrations measured at various time points during exposure were reproducible. Measured concentrations of NRL aeroallergen between responders (677 +/- 281 ng/m(3)) and nonresponders (611 +/- 351 ng/m(3)) were not statistically different. The cumulative inhaled NRL aeroallergen dose required for an asthmatic response ranged between 25 to 515 ng.

CONCLUSION

The total dose of latex aeroallergen eliciting an asthmatic response during QEC was mostly affected by the duration of exposure and varied widely from person to person.

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.

Glucoamylase: another fungal enzyme associated with baker's asthma

BACKGROUND

Aspergillus-derived enzymes are widely used as dough additives in the baking industry. These enzymes may give rise to immunoglobulin (Ig)E-mediated sensitization and occupational asthma. Glucoamylase (or amyloglucosidase) is an important industrial enzyme obtained from Aspergillus niger and used to provide fermentable sugars for yeast to improve loaf volume and texture.

OBJECTIVE

The aim of our study was to investigate the potential allergenic role of glucoamylase in baker's asthma.

METHODS

We report four subjects with work-related allergic respiratory symptoms who were exposed to glucoamylase and other starch-cleaving enzymes used as baking additives. The causative role of glucoamylase in work-related asthma was investigated by immunologic tests and specific inhalation challenges (SIC). Glucoamylase allergenic components were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting.

RESULTS

Skin prick tests to glucoamylase (10 mg/mL) gave a positive response in all patients. Further, a positive skin prick test to alpha-amylase was obtained in the four patients and to hemicellulase in two of them. SIC to glucoamylase elicited isolated early asthmatic responses in the three patients tested, and SIC to alpha-amylase elicited early asthmatic responses in two patients and a dual asthmatic response in another patient. Immunoblotting with glucoamylase showed several IgE-binding bands with molecular masses between 33 and 96 kD. IgE-inhibition assays showed scarce to moderate allergenic cross-reactivity between glucoamylase and alpha-amylase.

CONCLUSIONS

These bakers had developed IgE-mediated occupational asthma to glucoamylase and alpha-amylase. Fungal glucoamylase is widely used as a baking additive and this enzyme may give rise to allergic respiratory reactions among exposed workers.