Alexandra Baar

Early childhood IgE reactivity to pathogenesis-related class 10 proteins predicts allergic rhinitis in adolescence

BACKGROUND Component-resolved diagnosis might improve the prediction of future allergy in young children. OBJECTIVE We sought to investigate the association between IgE reactivity to the pathogenesis-related class 10 (PR-10) protein family and allergic rhinitis to birch pollen (ARbp) from early childhood up to age 16 years. METHOD Questionnaire data and sera obtained at 4, 8, and 16 years of age from the Barn/Children Allergi/Allergy Milieu Stockholm Epidemiologic (BAMSE) study birth cohort were used. Sera from 764 children were analyzed for IgE reactivity to 9 PR-10 allergen proteins at the 3 time points by using an allergen chip based on ISAC technology. ARbp was defined as upper airway symptoms during birch pollen exposure. RESULTS IgE reactivity to Bet v 1 was found in 12%, 17%, and 25% of children at 4, 8, and 16 years of age. IgE reactivity of PR-10 proteins showed a hierarchic intrarelationship: Bet v 1 > Mal d 1 > Cor a 1.04 > Ara h 8 > Pru p 1 > Aln g 1 > Api g 1 > Act d 8 > Gly m 4. There was an increased risk of incidence and persistence of ARbp up to age 16 years with increasing levels of Bet v 1-specific IgE or increasing numbers of IgE-reactive PR-10 proteins at 4 years. Children with severe ARbp at age 16 years had higher levels of Bet v 1-specific IgE at age 4 years compared with children with mild symptoms. CONCLUSION ARbp at age 16 years can be predicted by analysis of IgE reactivity to PR-10 proteins in early childhood.

Molecular and Immunological Characterization of Tri a 36, a Low Molecular Weight Glutenin, as a Novel Major Wheat Food Allergen

Wheat is an essential element in our nutrition but one of the most important food allergen sources. Wheat allergic patients often suffer from severe gastrointestinal and systemic allergic reactions after wheat ingestion. In this study, we report the molecular and immunological characterization of a new major wheat food allergen, Tri a 36. The cDNA coding for a C-terminal fragment of Tri a 36 was isolated by screening a wheat seed cDNA expression library with serum IgE from wheat food-allergic patients. Tri a 36 is a 369-aa protein with a hydrophobic 25-aa N-terminal leader peptide. According to sequence comparison it belongs to the low m.w. glutenin subunits, which can be found in a variety of cereals. The mature allergen contains an N-terminal domain, a repetitive domain that is rich in glutamine and proline residues, and three C-terminal domains with eight cysteine residues contributing to intra- and intermolecular disulfide bonds. Recombinant Tri a 36 was expressed in Escherichia coli and purified as soluble protein. It reacted with IgE Abs of ∼80% of wheat food-allergic patients, showed IgE cross-reactivity with related allergens in rye, barley, oat, spelt, and rice, and induced specific and dose-dependent basophil activation. Even after extensive in vitro gastric and duodenal digestion, Tri a 36 released distinct IgE-reactive fragments and was highly resistant against boiling. Thus, recombinant Tri a 36 is a major wheat food allergen that can be used for the molecular diagnosis of, and for the development of specific immunotherapy strategies against, wheat food allergy.

The use of the MeDALL-chip to assess IgE sensitization: a new diagnostic tool for allergic disease?

Allergic sensitization is frequently present in asthma and rhinitis, but the role of specific immunoglobulin E (s‐IgE) is not always clear. Multiple s‐IgE analyses may provide insight into this relationship, thus a microarray chip was developed within the EU‐funded MeDALL project. The main objective was to evaluate the performance of the MeDALL‐chip compared to ImmunoCAP and skin prick test (SPT) in detecting allergic sensitization in children and secondarily to investigate the association to asthma and allergic rhinitis.

Wheat allergy in children evaluated with challenge and IgE antibodies to wheat components

Wheat sensitization is common but IgE antibodies (IgE‐abs) to wheat are not predictive of clinical symptoms in children with suspected wheat allergy. Wheat allergen components other than ω‐5 gliadin have not been well studied. Our aim was to characterize the clinical profile and investigate the value of adding measurements of IgE‐abs to wheat components in a group of children with a doctors diagnosed wheat allergy.

The high molecular weight glutenin subunit Bx7 allergen from wheat contains repetitive IgE epitopes

Wheat is one of the most common food allergen sources for children and adults. The aim of this study was to characterize new wheat allergens using an IgE discovery approach and to investigate their IgE epitopes.

Detection of IgE Reactivity to a Handful of Allergen Molecules in Early Childhood Predicts Respiratory Allergy in Adolescence

Background Sensitization in early childhood may precede respiratory allergy in adolescence. Methods IgE reactivity against 132 allergen molecules was evaluated using the MeDALL microarray in sera obtained from a random sample of 786 children at the age of 4, 8 and 16 years in a population based birth cohort (BAMSE). Symptoms were analyzed by questionnaire at ages 4, 8 and 16 years. Clinically and independent relevant allergen molecules accounting for ≥ 90% of IgE reactivities in sensitized individuals and at all time-points were identified as risk molecules and used to predict respiratory allergy. The data was replicated in the Manchester Asthma and Allergy Study (MAAS) birth cohort by studying IgE reactivity with the use of a commercial IgE microarray. Sera were obtained from children at the ages of 3, 5, 8 and 11 years (N = 248) and the outcome was studied at 11 years. Findings In the BAMSE cohort 4 risk molecules could be identified, i.e.: Ara h 1 (peanut), Bet v 1 (birch), Fel d 1 (cat), Phl p 1 (grass). For MAAS the corresponding number of molecules was 5: Der p 1 (dust mite), Der f 2 (dust mite), Phl p 1 (grass), Phl p 5 (grass), Fel d 1 (cat). In BAMSE, early IgE reactivity to ≥ 3 of 4 allergen molecules at four years predicted incident and persistent asthma and/or rhinitis at 16 years (87% and 95%, respectively). The corresponding proportions in the MAAS cohort at 16 years were 100% and 100%, respectively, for IgE reactivity to ≥ 3 of 5 risk molecules. Interpretations IgE reactivity to a few allergen molecules early in life identifies children with a high risk of asthma and/or rhinitis at 16 years. These findings will be of importance for developing preventive strategies for asthma and rhinitis in children.

Usefulness of recombinant γ-gliadin 1 for identifying patients with celiac disease and monitoring adherence to a gluten-free diet

Background Celiac disease (CD) is an inflammatory disease of the small intestine caused by an immunologic hypersensitivity reaction to dietary wheat gluten. Objectives We sought to clone, express, and perform IgA epitope mapping of a CD-specific wheat antigen and to study its usefulness for identifying patients with CD and monitoring adherence to a gluten-free diet. Methods A synthetic gene coding for γ-gliadin 1 (GG1) was expressed in Escherichia coli. Recombinant γ-gliadin 1 (rGG1) was purified and characterized biochemically, structurally, and immunologically by using sera from patients with CD and control subjects. Overlapping GG1 peptides were synthesized for IgA and IgG epitope mapping. GG1 and peptide-specific antibodies were raised for tracing GG1 in cereals and dietary wheat products and to study its resistance to digestion. Results rGG1 was expressed and purified. rGG1-based IgA ELISAs performed in populations of patients with CD and control subjects showed a specificity of 92.9%, which was higher than that of gliadin extract (e). Furthermore, it allowed monitoring of adherence to a gluten-free diet in patients. A 26-amino-acid peptide from the proline-glutamine–rich repetitive N-terminal region was identified as the immunodominant IgA epitope. GG1-related antigens were found in rye, barley, and spelt but not in oat, rice, or maize. GG1 was detected in dietary wheat products after baking, and in particular, the major IgA epitope–containing region was resistant against digestion. Conclusions rGG1 and its epitope might be useful for identifying patients with CD, monitoring treatment, and studying the pathomechanisms of CD and development of preventive and therapeutic strategies.

Evidence for higher sensitivity of recombinant Tri a 36 compared to omega-5-gliadin for diagnosis of wheat food allergy

Background Wheat is one of the most important food allergen sources. Using natural wheat allergen extracts for serological diagnosis of wheat-induced food allergy false positive test results are frequently obtained, in particular in grass pollen allergic patients. Therefore, Tri a 19, an omega-5-gliadin, which is known as a major allergen in wheat dependent exercise induced anaphylaxis (WDEIA) and in wheat food allergy in children, is widely used for the serological diagnosis of wheat-induced food allergy.