Constance F. den Hartog Jager

Peanut epitopes for IgE and IgG4 in peanut-sensitized children in relation to severity of peanut allergy

BACKGROUND Better understanding of the relationship between antibody response to peanut and clinical sensitivity might lead to more accurate prognostication. OBJECTIVE We sought to investigate peanut-specific IgE and IgG4 epitope diversity in relation to challenge-defined clinical sensitivity to peanut in a group of peanut-sensitized children. METHODS Clinical sensitivity was determined by means of double-blind, placebo-controlled peanut challenges in 24 sensitized children. Six atopic control subjects were included. Specific IgE and IgG4 binding to 419 overlapping 15-amino-acid peptides representing the sequence of recombinant Ara h 1, Ara h 2, and Ara h3 was analyzed by means of microarray immunoassay. RESULTS Peanut-sensitized patient sera bound significantly more IgE and IgG4 epitopes than control sera. This patient group reacted to the same Ara h 1, Ara h 2, and Ara h 3 epitopes as reported previously. There was a positive correlation between IgE epitope diversity (ie, number of epitopes recognized) and clinical sensitivity (r = 0.6), such that patients with the greatest epitope diversity were significantly more sensitive than those with the lowest diversity (P = .021). No specific epitopes were associated with severe reactions to peanut. IgG4 binding was observed to largely similar epitopes but was less pronounced than IgE binding and did not relate to the clinical sensitivity to peanut. IgE and IgG4 epitope-recognition patterns were largely stable over a 20-month period. CONCLUSION Clinical sensitivity, as determined by means of double-blind, placebo-controlled peanut challenge, is positively related to a more polyclonal IgE response, which remains stable over time.

Sensitization to Cor a 9 and Cor a 14 is highly specific for a hazelnut allergy with objective symptoms in Dutch children and adults

BACKGROUND Component-resolved diagnosis has been shown to improve the diagnosis of food allergy. OBJECTIVE We sought to evaluate whether component-resolved diagnosis might help to identify patients at risk of objective allergic reactions to hazelnut. METHOD A total of 161 hazelnut-sensitized patients were included: 40 children and 15 adults with objective symptoms on double-blind, placebo-controlled food challenges (DBPCFCs) and 24 adults with a convincing objective history were compared with 41 children and 41 adults with no or subjective symptoms on DBPCFCs (grouped together). IgE levels to hazelnut extract and single components were analyzed with ImmunoCAP. RESULTS IgE levels to hazelnut extract were significantly higher in children with objective than with no or subjective symptoms. In 13% of children and 49% of adults with hazelnut allergy with objective symptoms, only sensitization to rCor a 1.04 was observed and not to other water-soluble allergens. Sensitization to rCor a 8 was rare, which is in contrast to rCor a 1. Sensitization to nCor a 9, rCor a 14, or both was strongly associated with hazelnut allergy with objective symptoms. By using adapted cutoff levels, a diagnostic discrimination between severity groups was obtained. IgE levels to either nCor a 9 of 1 kUA/L or greater or rCor a 14 of 5 kUA/L or greater (children) and IgE levels to either nCor a 9 of 1 kUA/L or greater or rCor a 14 of 1 kUA/L or greater (adults) had a specificity of greater than 90% and accounted for 83% of children and 44% of adults with hazelnut allergy with objective symptoms. CONCLUSION Sensitization to Cor a 9 and Cor a 14 is highly specific for patients with objective symptoms in DBPCFCs as a marker for a more severe hazelnut allergic phenotype.

Oral treatment with β-lactoglobulin peptides prevents clinical symptoms in a mouse model for cow's milk allergy.

Prior exposure to partial whey hydrolysates has been shown to reduce the allergic response to whey in mice. This effect was more pronounced in combination with a diet containing non‐digestible oligosaccharides (scGOS/lcFOS/pAOS). It is unknown which fractions/epitopes are responsible for this effect. Therefore, the prophylactic ability of synthetic peptides of β‐lactoglobulin with/without a scGOS/lcFOS/pAOS‐containing diet to reduce the allergic response in a mouse model for cows milk allergy was investigated.

Majority of shrimp-allergic patients are allergic to mealworm.

To the Editor: The growing world population motivates the exploration of new sustainable protein sources to ensure food security. Insects such as mealworm (Tenebrio molitor) are promising candidates, with active ongoing marketing efforts within America and Europe. This warrants assessment of the potential risks. Toxicologic and microbiological risks were assessed previously, but not the potentially allergenic risks. Pilot results suggest that shrimp-allergic patients might be at risk for mealworm allergy because IgE binding to tropomyosin and arginine kinase (major shellfish allergens) and sarcoplasmic calcium-binding protein and myosin light chain (minor shell fish allergens) was detected. Our aim was to investigate the allergic potential of mealworm in the shrimp-allergic population. Fifteen from 60 adult patients from the University Medical Center Utrecht with shrimp allergy based on specialist opinion and diagnostic testing were included in this double-blind, placebocontrolled food challenge (DBPCFC) trial, after testing positive in ImmunoCAP, skin prick test, basophil activation test, or immunoblot (see this article’s Online Repository at www.jacionline.org). All subjects gave written informed consent before participation. The study was approved by the local ethics committee (NL43731.041.13). Patients’ median age was 38 years (range, 19-69 years), and 47%were men. Symptoms by history ranged from oral symptoms to anaphylactic shock. Four patients had a positive diagnostic shrimp challenge in the past (Table I). None of the patients knowingly consumed mealworm proteins. Most had inhalant allergies to house dust mite (11 of 15) and pollen (11 of 15), and 9 patients had 1 or more other food allergies. All patients avoided eating shellfish.

IgG Antibodies in Food Allergy Influence Allergen–Antibody Complex Formation and Binding to B Cells: A Role for Complement Receptors

Allergen–IgE complexes are more efficiently internalized and presented by B cells than allergens alone. It has been suggested that IgG Abs induced by immunotherapy inhibit these processes. Food-allergic patients have high allergen-specific IgG levels. However, the role of these Abs in complex formation and binding to B cells is unknown. To investigate this, we incubated sera of peanut- or cow’s milk–allergic patients with their major allergens to form complexes and added them to EBV-transformed or peripheral blood B cells (PBBCs). Samples of birch pollen-allergic patients were used as control. Complex binding to B cells in presence or absence of blocking Abs to CD23, CD32, complement receptor 1 (CR1, CD35), and/or CR2 (CD21) was determined by flow cytometry. Furthermore, intact and IgG-depleted sera were compared. These experiments showed that allergen–Ab complexes formed in birch pollen, as well as food allergy, contained IgE, IgG1, and IgG4 Abs and bound to B cells. Binding of these complexes to EBV-transformed B cells was completely mediated by CD23, whereas binding to PBBCs was dependent on both CD23 and CR2. This reflected differential receptor expression. Upon IgG depletion, allergen–Ab complexes bound to PBBCs exclusively via CD23. These data indicated that IgG Abs are involved in complex formation. The presence of IgG in allergen–IgE complexes results in binding to B cells via CR2 in addition to CD23. The binding to both CR2 and CD23 may affect Ag processing and presentation, and (may) thereby influence the allergic response.

Characterization of T Cell Epitopes in Bovine α-Lactalbumin

Background: Recent studies have indicated that peptides containing T cell epitopes may be used for immunotherapy. While for several cows milk allergens the T cell epitopes have been described, the T cell epitopes in the major allergen α-lactalbumin (α-LAC) are unknown. Therefore, the aim of this study was to determine the T cell epitopes in α-LAC. Methods: Nineteen synthetic peptides spanning α-LAC were obtained. Cows milk-specific T cell lines (TCLs) of 46 subjects were generated and tested for their specificity for α-LAC. The lines responding to α-LAC were subsequently tested to determine their activation in response to the peptides. Results: More than half of the TCLs generated did not respond to α-LAC or lost their responsiveness during subsequent experiments, which indicates that α-LAC has low immunogenicity. Only 8 TCLs recognized 1 or more peptides. The recognition of the peptides was diverse and no major epitopes could be defined. Conclusion: The immunogenicity of α-LAC is very low compared to other major allergens in cows milk. Moreover, there seems to be no dominant epitope present in the protein. Therefore, it seems unlikely that peptides of this protein can be used for immunotherapy.

Is mealworm or shrimp allergy indicative for food allergy to insects

SCOPE The growing world population is a key driver for the exploration of sustainable protein sources to ensure food security. Mealworm and other insects are promising candidates. Previously we found that shrimp allergic patients are at risk for mealworm allergy, and that mealworm can induce a primary allergy . This study set out to investigate the allergenic potential of edible insects, suggested for human consumption by agencies such as WHO/FAO, in both the shrimp (potentially cross-reactive) and primary mealworm allergic population. The following insects were studied: mealworm, house cricket, giant mealworm, lesser mealworm, African grasshopper, large wax moth, and black soldier fly. METHODS AND RESULTS Fifteen shrimp (mealworm sensitized or allergic) patients and four primary mealworm allergic subjects, who participated in previous studies, were included. All shrimp allergic patients were sensitized to multiple insects with similar response profiles for all insects tested. Primary mealworm allergic patients, showed IgE binding to proteins from only a few insects on immunoblot, although basophil activation test was positive for all tested insects. CONCLUSION Shrimp allergic patients are most likely at risk of food allergy to mealworm and other insects. Primary mealworm allergy does not mean subjects are likely to react to all insects.

Non-digestible oligosaccharides can suppress basophil degranulation in whole blood of peanut-allergic patients

Background Dietary non-digestible oligosaccharides (NDOs) have a protective effect against allergic manifestations in children at risk. Dietary intervention with NDOs promotes the colonization of beneficial bacteria in the gut and enhances serum galectin-9 levels in mice and atopic children. Next to this, NDOs also directly affect immune cells and low amounts may reach the blood. We investigated whether pre-incubation of whole blood from peanut-allergic patients with NDOs or galectin-9 can affect basophil degranulation. Methods Heparinized blood samples from 15 peanut-allergic adult patients were pre-incubated with a mixture of short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides (scGOS/lcFOS), scFOS/lcFOS, or galectin-9 (1 or 5 µg/mL) at 37°C in the presence of IL-3 (0.75 ng/mL). After 2, 6, or 24 h, a basophil activation test was performed. Expression of FcεRI on basophils, plasma cytokine, and chemokine concentrations before degranulation were determined after 24 h. Results Pre-incubation with scGOS/lcFOS, scFOS/lcFOS, or galectin-9 reduced anti-IgE-mediated basophil degranulation. scFOS/lcFOS or 5 µg/mL galectin-9 also decreased peanut-specific basophil degranulation by approximately 20%, mainly in whole blood from female patients. Inhibitory effects were not related to diminished FcεRI expression on basophils. Galectin-9 was increased in plasma after pre-incubation with scGOS/lcFOS, and both NDOs and 5 µg/mL galectin-9 increased MCP-1 production. Conclusion and clinical relevance The prebiotic mixture scFOS/lcFOS and galectin-9 can contribute to decreased degranulation of basophils in vitro in peanut-allergic patients. The exact mechanism needs to be elucidated, but these NDOs might be useful in reducing allergic symptoms.