R. Merget

Multiple wheat flour allergens and cross-reactive carbohydrate determinants bind IgE in baker’s asthma

To cite this article: Sander I, Rozynek P, Rihs H‐P, van Kampen V, Chew FT, Lee WS, Kotschy‐Lang N, Merget R, Brüning T, Raulf‐Heimsoth M. Multiple wheat flour allergens and cross‐reactive carbohydrate determinants bind IgE in baker’s asthma. Allergy 2011; 66: 1208–1215.

A New Method to Bind Allergens for the Measurement of Specific IgE Antibodies

Background: Detection of allergen-specific IgE antibodies in patients’ sera plays a key role for the diagnosis of IgE-mediated allergy. If no validated test system is available, diagnostic tools must be developed, usually by coupling or binding the allergens to a solid phase. Streptavidin ImmunoCAP™ is a new solid phase for binding of allergens which can be used in the Pharmacia CAP® system. Objective: It was the aim of this study to assess the diagnostic validity of Streptavidin ImmunoCAP. Methods: Biotinylation and allergen concentration for binding to Streptavidin ImmunoCAP were optimized and IgE obtained with natural rubber latex, obeche wood, wheat and rye flour Streptavidin ImmunoCAP were compared with the results of ImmunoCAP™ and Enzyme Allergo-Sorbent Test (EAST) using sera from patients complaining of workplace-related respiratory symptoms. Results: While the relation of biotin-label and protein was critical (best results were obtained with a 5- fold molar excess), labelled protein for coupling to streptavidin ImmunoCAP was applicable in a wide concentration range. On average, IgE values with streptavidin ImmunoCAP were as high as with ImmunoCAP but considerably higher than values obtained by EAST. Conclusion: Streptavidin ImmunoCAP is a valuable tool for sensitive and specific measurement of IgE binding to new allergens superior to cellulose disk-based methods.

Prediction of challenge test results by flour-specific IgE and skin prick test in symptomatic bakers.

Background:  Wheat and rye flours are among the most important allergens causing occupational asthma. Usually, the diagnosis of baker’s asthma is based on inhalation challenge tests with flours.

Discontinuous IgE-binding epitopes contain multiple continuous epitope regions: results of an epitope mapping on recombinant Hol l 5, a major allergen from velvet grass pollen

The knowledge of IgE‐binding epitopes on allergen molecules is important for better understanding allergen–antibody interactions and, thus, for developing new strategies for immunotherapy.

Comparison of wheat and rye flour skin prick test solutions for diagnosis of baker's asthma

Background:  Skin prick tests (SPTs) play an important role in the diagnosis of bakers asthma and in the investigation of sensitization frequencies in field studies. It was the aim of our study to compare different SPT solutions for wheat and rye flour sensitization and to assess the validity of test results.

Evaluation of commercial skin prick test solutions for selected occupational allergens

Skin prick testing (SPT) is an important step in the diagnosis of IgE‐mediated occupational allergic diseases. The outcome of SPT is related to the quality of allergen extracts. Thus, the aim of the study was to assess different commercially available SPT solutions for selected occupational allergens.

Development of a 1-concentration-4-step dosimeter protocol for methacholine testing

Methacholine testing is an important diagnostic tool for asthma. Newly available dosimeter and software technology allows for simplification of the test. This study aimed to evaluate a single-concentration dosimeter protocol for methacholine testing by comparison with a multi-concentration dosimeter protocol similar to that recommended by the American Thoracic Society (ATS) (standard protocol). Fifty young subjects with high pretest probability for bronchial hyperresponsiveness underwent two challenges in randomized order within one week. The novel protocol used a Medic-Aid Sidestream nebulizer and a fixed methacholine concentration of 16mg/mL. Number and duration of nebulizations were matched to the last four doses of the standard protocol, and results were expressed cumulatively. The rank correlation between log slopes (n=50) was 0.86; that between log provocative doses (n=18), which differed at low values, was 0.58. When requiring a 20% fall in FEV(1) at any methacholine dose, 18 subjects were hyperresponsive and 28 normoresponsive in both tests (46/50 concordant). One subject was positive only with the standard, and 3 only with the novel protocol (Cohens kappa 83%). The novel protocol for methacholine testing yielded qualitative results similar to those of the ATS multi-concentration protocol, although there were quantitative differences at low doses. However, its design and handling may offer advantages for clinical practice.

Absence of relationship between degree of nonspecific and specific bronchial responsiveness in occupational asthma due to platinum salts

There is evidence that bronchial responsiveness to allergen is quantitatively correlated with bronchial responsiveness to nonspecific stimuli in subjects with allergic asthma. This association has been questioned in occupational asthma due to low molecular weight substances. It was the aim of this study to assess the quantitative association of bronchial responsiveness to methacholine (MCh) and platinum salts (Pt), in the form of hexachloroplatinic acid, in workers with occupational asthma due to platinum salts. Fifty seven subjects with exposure to Pt, work-related asthma, and a positive bronchial challenge with Pt, underwent skin prick tests with Pt and bronchial challenge with MCh. Using the provocation concentration causing a > or = 50% fall in specific airway conductance (PC50sGaw(Pt)) as dependent variable, anamnestic data (period from first symptoms to removal, period between removal from exposure and diagnosis, and smoking), season of the investigation, skin prick tests with environmental allergens, total immunoglobulin E (IgE), skin reactivity to Pt (Pt concentration causing a 2 mm wheal), and PC50sGaw(MCh) were included as independent variables for regression analysis. Fifty two subjects (91%) showed a PC50sGaw(MCh) < 8 mg.mL-1 (geometric mean for all subjects 1.6 mg.mL-1). Responsiveness to Pt varied widely between subjects (geometric mean of PC50sGaw 9 x 10-5 mol.L-1, range 2 x 10-7 to 10-2 mol.L-1). There was no univariate correlation between bronchial responsiveness to MCh and Pt, but there was a correlation between skin reactivity to Pt and PC50sGaw(Pt) (r = 0.6). This association could not be improved by considering PC50sGaw(MCh), the period from first symptoms to removal, or the period between removal from exposure and diagnosis. The parameters that showed the highest (negative) associations with PC50sGaw(Pt) were skin reactivity to Pt and the period between removal from exposure and diagnosis (r = 0.65). We conclude that there is a moderate association between bronchial responsiveness to platinum salts and skin reactivity to platinum salts. However, there is no association between methacholine responsiveness and bronchial responsiveness to allergen in occupational asthma due to platinum salts.

When should a substance be designated as sensitizing for the skin (`Sh’) or for the airways (`Sa’)?

In the List of MAK and BAT Values compounds are designated with `Sa’ (`sensitizing for the airways’) or `Sh’ (`sensitizing for the skin’) if, according to scientific evidence, they are allergens. Mainly based on suggestions by a WHO working group and based on our own experience, extended criteria have been elaborated by the working group `skin and allergy’ of the Commission of the Deutsche Forschungsgemeinschaft for the Investigation of Health Hazards of Chemical Compounds in the Work Area, which are presented in this article. They serve as guidelines for deciding which substances have to be labelled `Sa’ and `Sh’, respectively, for the prevention of sensitization and subsequent allergic diseases in workers. Although in some special cases their strict application may not be deemed necessary or possible, the proposed new criteria should be used to make the procedure of classification of substances: 1) more rational, 2) more consistent, 3) more comprehensible, and 4) more transparent. This paper informs readers working scientifically or administratively in this field and invites a critical discussion of the issue.

Baker's asthma due to xylanase and cellulase without sensitization to alpha-amylase and only weak sensitization to flour.

Background: The baking additives xylanase and cellulase were described as baking additives causing baker’s asthma. It is not known whether monosensitization to these enzymes may occur. Methods: We present a case report of a baker with work-related asthma evaluated by skin prick test (SPT), enzyme-linked immunosorbent assay (EAST), immunoblot, EAST and immunoblot inhibition, and specific bronchial challenge. Fungal xylanase and α-amylase were measured by two-site enzyme immunoassays in products used by the patient at work. Results: Allergy to xylanase and cellulase was demonstrated by SPT, EAST, immunoblot and specific bronchial challenge (for xylanase only). No sensitization to α-amylase could be demonstrated, but there was a weak flour allergy as documented by EAST and immunoblot and a positive occupational-type challenge with high concentrations of rye flour. Four baking additives contained measurable amounts of fungal α-amylase and xylanase, without a correlation between these enzymes. Conclusions: We conclude that occupational asthma due to the baking additives xylanase and cellulase may occur without concomitant sensitization to α-amylase and only weak sensitization to flour.