Doerthe A. Andreae

Development of a novel peptide microarray for large-scale epitope mapping of food allergens

BACKGROUND The peptide microarray is a novel assay that facilitates high-throughput screening of peptides with a small quantity of sample. OBJECTIVE We sought to use overlapping peptides of milk allergenic proteins as a model system to establish a reliable and sensitive peptide microarray-based immunoassay for large-scale epitope mapping of food allergens. METHODS A milk peptide microarray was developed by using commercially synthesized peptides (20-mers, 3 offset) covering the primary sequences of alpha(s1)-casein, alpha(s2)-casein, beta-casein, kappa-casein, and beta-lactoglobulin. Conditions for printing and immunolabeling were optimized using a serum pool of 5 patients with milk allergy. Reproducibility of the milk peptide microarray was evaluated using replicate arrays immunolabeled with the serum pool, whereas specificity and sensitivity were assessed by using serial dilution of the serum pool and a peptide inhibition assay. RESULTS Our results show that epitopes identified by the peptide microarray were mostly consistent with those identified previously by SPOT membrane technology, but with specific binding to a few newly identified epitopes of milk allergens. Data from replicate arrays were reproducible (r > or = 0.92) regardless of printing lots, immunolabeling, and serum pool batches. Using the serially diluted serum pool, we confirmed that IgE antibody binding detected in the array was specific. Peptide inhibition of IgE binding to the same peptide and overlapping peptides further confirmed the specificity of the array. CONCLUSION A reliable peptide microarray was established for large-scale IgE epitope mapping of milk allergens, and this robust technology could be applied for epitope mapping of other food allergens.

Identification of IgE sequential epitopes of lentil (Len c 1) by means of peptide microarray immunoassay.

BACKGROUND Lentils are often responsible for allergic reactions to legumes in Mediterranean children. Although the primary sequence of the major allergen Len c 1 is known, the location of the IgE-binding epitopes remains undefined. OBJECTIVE We sought to identify IgE-binding epitopes of Len c 1 and relate epitope binding to clinical characteristics. METHODS One hundred thirty-five peptides corresponding to the primary sequence of Len c 1 were probed with sera from 33 patients with lentil allergy and 15 nonatopic control subjects by means of microarray immunoassay. Lentil-specific IgE levels, skin prick test responses, and clinical reactions to lentil were determined. Epitopes were defined as overlapping signal above interslide and intraslide cutoffs and confirmed by using inhibition assays with a peptide from the respective region. Hierarchic clustering of microarray data was used to correlate binding patterns with clinical findings. RESULTS The patients with lentil allergy specifically recognized IgE-binding epitopes located in the C-terminal region between peptides 107 and 135. Inhibition experiments confirmed the specificity of IgE binding in this region, identifying different epitopes. Linkage of cluster results with clinical data and lentil-specific IgE levels displayed a positive correlation between lentil-specific IgE levels, epitope recognition, and respiratory symptoms. Modeling based on the 3-dimensional structure of a homologous soy vicilin suggests that the Len c 1 epitopes identified are exposed on the surface of the molecule. CONCLUSION Several IgE-binding sequential epitopes of Len c 1 have been identified. Epitopes are located in the C-terminal region and are predicted to be exposed on the surface of the protein. Epitope diversity is positively correlated with IgE levels, pointing to a more polyclonal IgE response.

Swallowed Fluticasone Propionate Is an Effective Long-Term Maintenance Therapy for Children With Eosinophilic Esophagitis

OBJECTIVES:Although effective in the treatment of eosinophilic esophagitis (EoE) in children, limited data exist on long-term safety and efficacy of swallowed topical corticosteroids. We investigated whether long-term use of swallowed fluticasone in children with EoE leads to sustained reduction in esophageal eosinophils, and endoscopic and clinical improvement.METHODS:In an open-label, prospective, single-center study, we offered pediatric patients with active EoE fluticasone 2 puffs to swallow twice a day (strengths in μg/puff: 2–4 years: 44, 5–11 years: 110, ≥12 years: 220). Clinical, endoscopic, and histological assessments were performed at baseline and shortly after therapy. If histological remission was seen, fluticasone was continued with clinical follow-ups every 4 months and endoscopic and histological follow-ups yearly. Clinical scores were derived from eight symptoms (abdominal pain, nausea, vomiting, regurgitation, chest pain, dysphagia, food impaction, and early satiety). Endoscopic scores were derived from six features (rings, exudates, furrows, edema, stricture, and shearing). Scores were expressed as ratio (features present/total). In addition to peak eosinophils/high power field (HPF) (primary outcome), histological features (eosinophilic microabscesses, degranulation, superficial layering, basal zone hyperplasia, dilated intercellular spaces, and lamina propria fibrosis) were assessed. Median clinical and endoscopic scores and individual histologic features were compared over 4 time intervals: <4 months, 4–12 months, 13–24 months, and >24 months. Growth and adverse effects were monitored.RESULTS:We enrolled 54 patients, 80% male, median age 6.5 years (range 2–17 years), 85% atopic (57% asthma, 68% allergic rhinitis, and 31% atopic dermatitis), and 74% with food allergy. Mean follow-up was 20.4 months, the longest being 68 months (5.7 years). Esophageal eosinophil counts significantly decreased (median peak eosinophils/HPF at baseline 72, <4 months: 0.5, 4–12 months: 1.75, 13–24 months: 10, and >24 months: 12, all P<0.01). All histological features significantly decreased from baseline to all follow-up time points (all P<0.01). Lamina propria fibrosis significantly decreased (% patients with fibrosis at baseline 92, <4 months: 41, 4–12 months: 50, 13–24 months: 45, and >24 months: 39, all P<0.01). Endoscopic features improved (score at baseline 0.37, <4 months: 0.17, 4–12 months: 0.17, 13–24 months: 0, and >24 months: 0.1, all P<0.01, except at >24 months: P<0.05). Symptoms improved (score at baseline 0.22, <4 months: 0, 4–12 months: 0.11, 13–24 months: 0.11, and >24 months: 0.11, all P<0.05 except at >24 months: P=0.05). In a mixed linear regression model that accounts for correlation of repeated observations in the patient in a per-patient analysis, we found that treatment with swallowed fluticasone led to a statistically significant and sustained decrease in peak esophageal eosinophil counts. Asymptomatic esophageal candidiasis was seen in three children but resolved with anti-fungal therapy. Height and weight z-scores followed expected growth curves.CONCLUSIONS:We demonstrate that swallowed fluticasone is effective as a long-term maintenance therapy for children with EoE, without growth impediment or serious side effects.