Rye flour induces a stronger early bronchial response than wheat flour in occupational asthma

Structural Basis of IgE Binding to α- and γ-Gliadins: Contribution of Disulfide Bonds and Repetitive and Nonrepetitive Domains

Wheat products cause IgE-mediated allergies. The present study aimed to decipher the molecular basis of α- and γ-gliadin allergenicity. Gliadins and their domains, the repetitive N-terminal and the nonrepetitive C-terminal domains, were cloned and expressed in Escherichia coli. Their secondary structures and their IgE binding capacity were compared with those of natural proteins before and after reduction/alkylation. Allergenicity was evaluated with sera from patients who had a wheat food allergy or baker's asthma. The secondary structures of natural and recombinant proteins were slightly different. Compared with natural gliadins, recombinant proteins retained IgE binding but with reduced reactivity. Reduction/alkylation decreased IgE binding for both natural and recombinant gliadins. Although more continuous epitopes were identified in the N-terminal domains of α- and γ-gliadins, both the N-terminal and C-terminal domains contributed to IgE binding. As for other members of the prolamin superfamily, disulfide bonds appear to be of high importance for IgE binding.

Molecular and immunological characterization of wheat Serpin (Tri a 33)

SCOPE

Several wheat proteins are responsible for food and respiratory allergies. Due to their large polymorphism, the allergenic potential of a number of them has not yet been precisely established. The aim of this work was to perform a thorough assessment of serpin (Tri a 33) allergenicity.

METHODS AND RESULTS

Recombinant wheat Serpin-Z2B isoform (rSerpin-Z2B) was expressed in Escherichia coli. Synchrotron radiation circular dichroism data indicated that the recombinant serpin contains slightly more β-strands than α-helix structures. IgE reactivity of sera from 103 patients with food allergy and 29 patients with Baker's asthma was evaluated using ELISA, a model of basophil activation and linear epitope mapping (Pepscan). Twenty percent of patients with food allergy to wheat and 31% of those with Baker's asthma displayed rSerpin-Z2B-specific IgE in ELISA. The protein was able to induce IgE-dependent basophil degranulation. The Pepscan experiment identified four regions involved in IgE binding to serpin. Heating the protein induced its irreversible denaturation and impaired IgE binding, revealing the predominance of conformational epitopes.

CONCLUSION

This study confirms wheat serpin allergenicity and shows that recombinant serpin may be a marker of a broad spectrum of sensitization to wheat proteins.

Exposure to flour dust in South African supermarket bakeries: modeling of baseline measurements of an intervention study

INTRODUCTION

Exposure to flour dust has been reported as an important risk factor for allergic respiratory disease among bakery workers. A high prevalence of allergic sensitization and asthma was recently reported in South African supermarket bakeries. The aim of this study was to conduct a detailed exposure assessment of these bakeries so as to provide the baseline for a broader intervention study.

METHODS

A total of 211 full-shift personal samples were collected on randomly selected individuals within five different job categories in 18 bakeries. The samples were analyzed for particulate mass and specific flour dust allergens (wheat, rye, and fungal alpha-amylase). Exposure models were developed using job, bakery size, tasks, and specific ingredients used. Bakery and worker were regarded as random effect components.

RESULTS

Bread bakers had the highest average (geometric mean) exposures (1.33 mg m(-3) flour dust particulate, 13.66 microg m(-3) wheat allergens, and 5.14 microg m(-3) rye allergens). For alpha-amylase allergens, most samples were below the limit of detection for several occupational titles. In the mixed effect models, the significant predictors of elevated exposure to inhalable dust particulate as well as wheat and rye allergen concentrations were large bakery size, bread baking, and use of cereal flours, while tasks such as confectionery work were negatively correlated with these exposure metrics. Weighing tasks and use of premix products were associated with increased exposure to fungal alpha-amylase. A high correlation between particulate dust and wheat (r = 0.84) as well as rye (r = 0.86) was observed, with a much lower correlation between particulate dust and fungal alpha-amylase (r = 0.33). Overall, a low proportion (39%) of bakery stores implemented various control measures to reduce dust exposures in the bakeries.

CONCLUSIONS

This study confirms that current exposure control strategies in supermarket bakery stores are inadequate in reducing dust exposures to protect the health of bakery workers.

Physical and biochemical properties of airborne flour particles involved in occupational asthma

Aerosol particles which deeply penetrate the human airways and which trigger baker's asthma manifestations are known to represent only a part of flour and of airborne particles found in bakeries. They were a major focus of this study. To this end, aerosols were produced from different wheat and rye flours, using an automatic generator designed for bronchial challenge. Particles were characterized for their size distribution, their ability to be deposited in the airways, their protein content, their histological composition and their reactivity with immunoglobulin E (IgE) present in sera from asthmatic bakers. Like dust particles collected in the bakery, the aerosols produced showed increased protein content but decreased IgE reactive protein content when compared to the corresponding bulk flours. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of these particles showed a predominance of endosperm gluten proteins. Under scanning electron microscopy, flour particles displayed various tissue fragments with entrapped large A-starch and small B- or C-starch granules, whereas aerosol particles appeared primarily as a mixture of the endosperm intracellular interstitial protein matrix and small B- or C-starch granules free or still associated. These observations showed that aerosols supposed to penetrate deeply the airways, mainly correspond to intracellular fragments of endosperm cells enriched in gluten proteins but with lower amount of allergens belonging to albumins or globulins.

Rye flour allergens: an emerging role in baker's asthma

BACKGROUND

Exposure to wheat flour is usually considered the most important cause of baker's asthma. However, other flours frequently used in bakeries may play an emerging role as relevant allergens causing occupational asthma.

AIMS OF STUDY

We report on two cases of baker's asthma mainly caused by exposure to rye flour. The profile of allergen sensitization to cereal flour was investigated.

METHODS

Two bakery workers suffering from rhinoconjunctivitis and asthma symptoms at work underwent an in vivo study (skin prick tests and bronchial allergen challenge) and in vitro study (total serum IgE, specific serum IgE and immunoblotting).

RESULTS

Specific inhalation challenge with wheat flour did not elicit an asthmatic reaction, however both patients showed an early asthmatic reaction with the rye flour challenge. Rye flour-immunoblotting showed IgE-binding bands around 12-15 kDa, that correspond to rye flour enzymatic inhibitors which were not present in the wheat flour immunoblot.

CONCLUSIONS

Both bakers had developed occupational asthma to rye flour (confirmed by specific inhalation challenge test). Rye flour allergens (enzymatic inhibitors) are important allergens that should be considered in the diagnosis of baker's asthma.

Baker's asthma with a predominant clinical response to rye flour

BACKGROUND

Relatively little attention has been paid to rye flour as opposed to wheat flour in clinical and epidemiological research into Baker's asthma.

METHODS

This report describes the investigation of a baker with asthma who reported a workplace response to rye flour and none to wheat flour, despite co-reactivity to both wheat and rye antigen.

RESULTS

Skin prick tests, RASTs and basophil stimulation tests were positive for both wheat and rye antigen, but quantitatively greater for rye than wheat. Bronchial challenge elicited a much greater response to the rye-wheat flour mix used in the bakery than to 100% wheat flour.

CONCLUSIONS

The greater clinical response to rye than to wheat may be immunologically mediated, but could also be due to physical characteristics of rye flour such as greater dose of inhaled airborne particles or an irritative effect. This information may be useful for medical management and occupational hygiene control, and should stimulate further research into rye flour in Baker's asthma.