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Background Skin prick testing (SPT) is the basic method for diagnosing IgE-mediated allergies. However, skin reactivity is related to the quality of allergen extracts, which are often poorly defined for occupational allergens. Objective To compare wheat and rye flour SPT solutions from different producers. Materials and methods Standardized SPTs were performed in seven allergy centres with wheat and rye flour solutions from four producers in 125 symptomatic bakers. Optimal cut-off levels for weal sizes were assessed with the Youden Index. Comparisons between SPT results of different solutions were made with flour-specific IgE (sIgE) as the gold standard. Sensitivities, specificities, positive and negative predictive values, and test efficiencies were calculated and compared with McNemar and χ2-tests. The influence of the choice of the gold standard (sIgE or challenge) test was examined for 95 subjects. Additionally, SPT solutions were analysed for protein and antigen content. Results The optimal cut-off level for all SPT solutions was a weal size of ⩾1.5 mm. While differences between wheat and rye flours were small, differences between producers were important. Variability of sensitivities (0.31–0.96), negative predictive values (0.42–0.91), and test efficiencies (0.54–0.90) were higher than variations of specificities (0.74–1.00) and positive predictive values (0.88–1.00). Similar results were obtained when using challenge test results as the gold standard. Variability could be explained by the different antigen contents of the SPT solutions. Conclusion There is a wide variability of SPT solutions for wheat and rye flour from different producers, mainly with respect to sensitivities, negative predictive values, and test efficiencies. Improvement and standardization of SPT solutions used for the diagnosis of baker's asthma are highly recommended. [ABSTRACT FROM AUTHOR]

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. Aims of the study: To evaluate the relevance of flour-specific serum immunoglobulin E (IgE) and skin prick test (SPT) in the diagnosis of baker’s asthma and to define flour-specific IgE concentrations and wheal sizes that allow a prediction of the outcome of challenge testing. Methods: Bronchial and nasal challenge tests with wheat (rye) flour were performed in 71 (95) symptomatic bakers. Determinations of flour-specific IgE as well as SPTs were performed in all subjects. Analyses included the calculation of sensitivity, specificity, positive (PPV) and negative predictive values (NPV) at different IgE concentrations and different wheal sizes, and receiver-operating characteristics (ROC) plots with the challenge result as gold standard. Results: Thirty-seven bakers were positive in the challenge with wheat flour, while 63 were positive with rye flour. Depending on the flour-specific IgE concentrations (wheal size), PPV was 74–100% (74–100%) for wheat and 82–100% (91–100%) for rye flour, respectively. The minimal cut-off values with a PPV of 100% were 2.32 kU/l (5.0 mm) for wheat flour and 9.64 kU/l (4.5 mm) for rye flour. The shapes of the ROC plots were similar for wheat and rye flour. Conclusion: High concentrations of flour-specific IgE and clear SPT results in symptomatic bakers are good predictors for a positive challenge test. Challenge tests with flours may be avoided in strongly sensitized bakers. [ABSTRACT FROM AUTHOR]

Background: Chi t 1.01, a hemoglobin of the midge Chironomus thummi thummi, is a widespread environmental and occupational allergen. The aim of the present investigation was to identify and compare peptides involved in B-cell epitopes of Chi t 1.01 recognized by 15 human IgE sera, six murine monoclonal antibodies (mAbs), and a polyclonal rabbit antiserum. Methods: Synthetic peptides 19-21 amino acids long covering the whole Chi t 1.01-sequence were covalently coupled to activated paper disks as well as adsorbed to wells of immunoplates and used for enzyme-linked immunosorbent assay. For one epitope mapping, we used overlapping synthetic octapeptides with one amino-acid offset. Results: Peptides containing the amino acids 13-17, 23-29, and 40-50 were recognized by three of the mAbs, while three other mAbs reacting with none of the peptides obviously recognized conformational epitopes. Binding sites for rabbit antibodies and for human IgE antibodies were scattered over the whole molecule. The peptide 80-100 seemed to comprise at least one important IgE epitope. Depending on the method of antigen binding to the solid phase, differing results were obtained. Conclusions: Several linear epitopes in Chi t 1.01 are recognized by human IgE antibodies, by mAbs, and by polyclonal rabbit antibodies. In addition, the results indicate the presence of conformational epitopes. [ABSTRACT FROM AUTHOR]

Background The rubber elongation factor in Hevea rubber (Hey b 1) is one of the most important latex allergen and is leading cause of latex type I hypersensitivity in children with spina bifida. Objective The aim of this study was to define the allergenic and antigenic epitopes of Hey b 1. Methods The immunoglobulin- (Ig)E and IgG antibody binding rites on Hey b I allergen were delineated by enzyme linked immunosorbent assay (ELISA) using synthetic overlapping peptides covering the whole Hey b 1 sequence. In order to improve the binding capacity and specificity all peptides were biotinylated at the N-terminal end via a 6-aminohexanoic acid as spacer and then adsorbed to streptavidin pre-coated microtitre plates. Fine mapping to define the essential amino acid residues for the antibody binding was achieved by using overlapping peptides with one amino acid offset. Results It was demonstrated that the IgE epitopes were located in different regions of Hey b I including the C-terminal segment (121–137) and the segments with amino acid residues of 30–49 and 46–64. Two monoclonal antibodies (MoAbs) II2F3 and II4G9 raised against purified Hey b 1 recognized the C-terminal segment only. The results of epitope mapping with three rabbit antisera revealed that five positive peptides, including the epitope peptides 31–49, 46–64 and 121–137, were involved in the antibody-binding sites. Fine mapping on the scgments 46–64 and 121–137 showed that the two MoAbs reacted with the peptide 125–134 in the C-terminal region, whereas the peptide with amino acids 124–134 was essential for recognition by human IgE antibodies. Epitopes to rabbit polyclonal IgG and human IgE were also found to be involved in the amino acid residues of 47–59. Conclusion Our results indicate that the most allergenic/antigenic portions of Hey b 1 allergen are the C-terminal region and the region with amino acid residues of 31–64. In both regions, the minimal IgE-binding epitope is almost identical with the IgG-binding epitope. [ABSTRACT FROM AUTHOR]

Summarizes the important aspects of allergy research work on purified allergens. Denominations of allergens; Relation of everyday life with exposure to an enormous number of potential allergens in the environment; Identification and characterization of allergens.

Background: Several wheat flour allergens relevant to baker's asthma have been identified in the last 25 years. The aim of this study was to determine the frequency of sensitization to these allergens in German bakers. Methods: Using recombinant DNA technology, the following wheat flour allergens were cloned, expressed in Escherichia coli and purified: five subunits of the wheat α-amylase inhibitors (WTAI-CM1, WTAI-CM2, WTAI-CM3, WDAI-0.19 and WMAI-0.28), thioredoxin, thiol reductase or 1-cys-peroxiredoxin homologues, triosephosphate-isomerase, αβ-gliadin, serpin, glyceraldehyde-3-phosphate-dehydrogenase, a nonspecific lipid transfer protein (nsLTP), dehydrin, profilin and peroxidase. In addition, ImmunoCAPs with the recombinant allergen ω-5-gliadin and two cross-reactive carbohydrate determinants (CCDs), horse radish peroxidase (HRP) and the N-glycan of bromelain (MUXF), were used. Specific IgE was measured in wheat flour-positive sera from 40 German bakers with work-related asthma/rhinitis and 10 controls with pollinosis. Results: Thirty bakers (75%) had IgE to at least one of the 19 single allergens. Most frequent was IgE to WDAI-0.19, HRP and MUXF (25% each), followed by WTAI-CM1 (20%), thiol reductase (16%), WTAI-CM3 (15%), WTAI-CM2 and thioredoxin (12.5%), WMAI-28, triosephosphate-isomerase, αβ-gliadin (10%), 1-cys-peroxiredoxin (7.5%), dehydrin, serpin, glyceraldehyde-3-phosphate-dehydrogenase (5%), ω-5-gliadin, nsLTP and profilin (2.5%). Fifteen bakers (38%) had IgE to any α-amylase inhibitor and 12 (30%) to at least one CCD. The controls reacted exclusively to CCDs (80%), profilin (60%), thioredoxin (30%), triosephosphate isomerase and nsLTP (10%). Conclusions: The single allergen sensitization profiles obtained with 17 recombinant wheat flour allergens and two CCDs revealed no major allergen for German bakers. The highest frequencies were found for α-amylase inhibitors and CCDs. [ABSTRACT FROM AUTHOR]