New light on an old syndrome: Role of Api g 7 in mugwort pollen-related celery allergy.

BACKGROUND: Celery root is known to cause severe allergic reactions in patients sensitized to mugwort pollen. OBJECTIVE: We studied clinically well-characterized patients with celery allergy by IgE testing with a comprehensive panel of celery allergens to disentangle the molecular basis of what is known as the celery-mugwort syndrome. METHODS: Patients with suspected food allergy to celery underwent a standardized interview. Main inclusion criteria were a positive food challenge with celery or an unambiguous case history of severe anaphylaxis. IgE to celery allergens (rApi g 1.01, rApi g 1.02, rApi g 2, rApi g 4, nApi g 5, rApi g 6, rApi g 7) and to mugwort allergens (rArt v 1, rArt v 3, rArt v 4) were determined. IgE levels ≥0.35 kUA/L were regarded positive. RESULTS: Seventy-nine patients with allergy to celery were included. Thirty patients had mild oral or rhinoconjunctival symptoms, and 49 had systemic reactions. Sixty-eight percent had IgE to celery extract, 80% to birch pollen, and 77% to mugwort pollen. A combination of Api g 1.01, 1.02, 4, 5, and 7 increased the diagnostic sensitivity for celery allergy to 92%. The lipid transfer proteins Api g 2 and Api g 6 were not relevant in our celery-allergic population. IgE to Api g 7, detected in 52% of patients, correlated closely (r = 0.86) to Art v 1 from mugwort pollen. Eleven of 12 patients with monosensitization to Api g 7 were IgE negative to celery extract. The odds ratio for developing a severe anaphylactic reaction rather than only mild oral symptoms was about 6 times greater (odds ratio, 5.87; 95% confidence interval, 1.08-32.0; P = .0410) for Api g 7-sensitized versus -nonsensitized subjects. CONCLUSION: There is an urgent need for routine diagnostic tests to assess sensitization to Api g 7, not only to increase test sensitivity but also to identify patients at risk of a severe allergic reaction to celery.

Single-dose oral challenges to validate eliciting doses in children with cow's milk allergy.

BACKGROUND: There is increasing interest in the use of eliciting doses (EDs) to inform allergen risk management. The ED can be estimated from the distribution of threshold doses for allergic subjects undergoing food challenges within a specified population. Estimated ED05 values for cow's milk (the dose expected to cause objective allergic symptoms in 5% of the milk-allergic population) range from 0.5 mg to 13.9 mg cow's milk protein. We undertook a single-dose challenge study to validate a predicted ED05 for cow's milk of 0.5 mg protein. METHODS: Participants were recruited from 4 clinical centres. Predetermined criteria were used to identify patients reacting to 0.5 mg cow's milk protein (approximately 0.015 mL of fresh cow's milk). Children over 1 year underwent formal challenge to cow's milk to confirm clinical reactivity. RESULTS: 172 children (median age 6.0 (IQR 0.7-11) years, 57% male) were included in this analysis. Twelve (7.0%, 95% CI 3.7%-11.9%) children experienced objective symptoms that met the predetermined criteria. One participant had mild anaphylaxis that responded to a single dose of adrenaline, the remainder experienced only mild symptoms with no treatment required. We did not identify any baseline predictors of sensitization that were associated with objective reactivity to the single-dose challenge using 0.5 mg cow's milk protein. CONCLUSIONS: These data support an estimated ED05 for cow's milk of 0.5 mg protein. Values for ED05 above 0.5 mg for cow's milk protein proposed for allergen risk management need to be reviewed.

Cross-linking of sodium caseinate-structured emulsion with transglutaminase alters postprandial metabolic and appetite responses in healthy young individuals.

The physico-chemical and interfacial properties of fat emulsions influence lipid digestion and may affect postprandial responses. The aim of the present study was to determine the effects of the modification of the interfacial layer of a fat emulsion by cross-linking on postprandial metabolic and appetite responses. A total of fifteen healthy individuals (26.5 (sem 6.9) years and BMI 21.9 (sem 2.0) kg/m2) participated in a cross-over design experiment in which they consumed two isoenergetic (1924 kJ (460 kcal)) and isovolumic (250 g) emulsions stabilised with either sodium caseinate (Cas) or transglutaminase-cross-linked sodium caseinate (Cas-TG) in a randomised order. Blood samples were collected from the individuals at baseline and for 6 h postprandially for the determination of serum TAG and plasma NEFA, cholecystokinin (CCK), glucagon-like peptide 1 (GLP-1), glucose and insulin responses. Appetite was assessed using visual analogue scales. Postprandial TAG and NEFA responses and gastric emptying (GE) rates were comparable between the emulsions. CCK increased more after the ingestion of Cas-TG than after the ingestion of Cas (P< 0.05), while GLP-1 responses did not differ between the two test emulsions. Glucose and insulin profiles were lower after consuming Cas-TG than after consuming Cas (P< 0.05). The overall insulin, glucose and CCK responses, expressed as areas above/under the curve, did not differ significantly between the Cas and Cas-TG meal conditions. Satiety ratings were reduced and hunger, desire to eat and thirst ratings increased more after the ingestion of Cas-TG than after the ingestion of Cas (P< 0.05). The present results suggest that even a subtle structural modification of the interfacial layer of a fat emulsion can alter the early postprandial profiles of glucose, insulin, CCK, appetite and satiety through decreased protein digestion without affecting significantly on GE or overall lipid digestion.

Determination of the clinical egg allergy phenotypes using component-resolved diagnostics.

IgE-mediated egg allergy presents as one of the most common food allergies in children and is a food which is widely consumed all over the world. Measurement of egg white-specific IgE levels has been shown to be a poor predictor of clinical phenotypes of egg allergy, including to raw egg white, but particularly to baked or cooked egg. Egg white and yolk contain more than 20 different glycoproteins, including ovomucoid, ovalbumin, ovotransferrin, alpha-livetin, and the newly identified Gal d 6. Recent developments in component-resolved diagnostic technology, including microarrays, have enabled us to improve the way in which we diagnose food allergy. This technology allows us to measure specific IgE antibodies to individual egg allergens which have been highly purified. Characterization of the major egg allergens could help profile the relevant binding epitopes to each region and may also help diagnose the different clinical phenotypes of egg allergy.

Health sector costs of self-reported food allergy in Europe: a patient-based cost of illness study.

INTRODUCTION: Food allergy is a recognized health problem, but little has been reported on its cost for health services. The EuroPrevall project was a European study investigating the patterns, prevalence and socio-economic cost of food allergy. AIMS: To investigate the health service cost for food-allergic Europeans and the relationship between severity and cost of illness. METHODS: Participants recruited through EuroPrevall studies in a case-control study in four countries, and cases only in five countries, completed a validated economics questionnaire. Individuals with possible food allergy were identified by clinical history, and those with food-specific immunoglobulin E were defined as having probable allergy. Data on resource use were used to estimate total health care costs of illness. Mean costs were compared in the case-control cohorts. Regression analysis was conducted on cases from all 9 countries to assess impact of country, severity and age group. RESULTS: Food-allergic individuals had higher health care costs than controls. The mean annual cost of health care was international dollars (I$)2016 for food-allergic adults and I$1089 for controls, a difference of I$927 (95% confidence interval I$324-I$1530). A similar result was found for adults in each country, and for children, and was not sensitive to baseline demographic differences. Cost was significantly related to severity of illness in cases in nine countries. CONCLUSIONS: Food allergy is associated with higher health care costs. Severity of allergic symptoms is a key explanatory factor.

Kiwifruit allergy across Europe: clinical manifestation and IgE recognition patterns to kiwifruit allergens.

BACKGROUND: Kiwifruit is a common cause of food allergy. Symptoms range from mild to anaphylactic reactions. OBJECTIVE: We sought to elucidate geographic differences across Europe regarding clinical patterns and sensitization to kiwifruit allergens. Factors associated with the severity of kiwifruit allergy were identified, and the diagnostic performance of specific kiwifruit allergens was investigated. METHODS: This study was part of EuroPrevall, a multicenter European study investigating several aspects of food allergy. Three hundred eleven patients with kiwifruit allergy from 12 countries representing 4 climatic regions were included. Specific IgE to 6 allergens (Act d 1, Act d 2, Act d 5, Act d 8, Act d 9, and Act d 10) and kiwifruit extract were tested by using ImmunoCAP. RESULTS: Patients from Iceland were mainly sensitized to Act d 1 (32%), those from western/central and eastern Europe were mainly sensitized to Act d 8 (pathogenesis-related class 10 protein, 58% and 44%, respectively), and those from southern Europe were mainly sensitized to Act d 9 (profilin, 31%) and Act d 10 (nonspecific lipid transfer protein, 22%). Sensitization to Act d 1 and living in Iceland were independently and significantly associated with severe kiwifruit allergy (odds ratio, 3.98 [P = .003] and 5.60 [P < .001], respectively). Using a panel of 6 kiwifruit allergens in ImmunoCAP increased the diagnostic sensitivity to 65% compared with 20% for skin prick tests and 46% ImmunoCAP using kiwi extract. CONCLUSION: Kiwifruit allergen sensitization patterns differ across Europe. The use of specific kiwifruit allergens improved the diagnostic performance compared with kiwifruit extract. Sensitization to Act d 1 and living in Iceland are strong risk factors for severe kiwifruit allergy.

High-throughput NMR assessment of the tertiary structure of food allergens.

BACKGROUND: In vitro component-resolved diagnosis of food allergy requires purified allergens that have to meet high standards of quality. These include the authentication of their conformation, which is relevant for the recognition by specific IgE antibodies from allergic patients. Therefore, highly sensitive and reliable screening methods for the analysis of proteins/allergens are required to assess their structural integrity. In the present study one-dimensional 1H Nuclear Magnetic Resonance (1D 1H-NMR) analysis was adopted for the assessment of overall structural and dynamic properties and authentication of a set of relevant food allergens, including non-specific lipid transfer proteins from apple, peach and hazelnut, 7/8S seed storage globulins from hazelnut and peanut, 11S seed storage globulins from hazelnut and peanut, caseins from cows' and goats' milk and tropomyosin from shrimp. METHODOLOGY/PRINCIPAL FINDINGS: Two sets of 1D 1H-NMR experiments, using 700 MHz and 600 MHz instruments at 298 K were carried out to determine the presence and the extent of tertiary structure. Structural similarity among members of the individual allergen families was also assessed and changes under thermal stress investigated. The nuclear magnetic resonance (NMR) results were compared with structural information available either from the literature, Protein Data Bank entries, or derived from molecular models. CONCLUSIONS/SIGNIFICANCE: 1D (1)H-NMR analysis of food allergens allowed their classification into molecules with rigid, extended and ordered tertiary structures, molecules without a rigid tertiary structure and molecules which displayed both features. Differences in thermal stability were also detected. In summary, 1D (1)H-NMR gives insights into molecular fold of proteins and offers an independent method for assessing structural properties of proteins.

Effect of heating and glycation on the allergenicity of 2S albumins (Ara h 2/6) from peanut.

BACKGROUND: Peanut allergy is one of the most common and severe food allergies, and processing is known to influence the allergenicity of peanut proteins. We aimed to establish the effect of heating and glycation on the IgE-binding properties and biological activity of 2S albumins (Ara h 2/6) from peanut. METHODOLOGY/PRINCIPAL FINDINGS: Native Ara h 2/6 was purified from raw peanuts and heated in solution (15 min, 110°C) in the presence or absence of glucose. Ara h 2 and 6 were also purified from roasted peanut. Using PBMC and sera from peanut-allergic patients, the cellular proliferative potency and IgE reactivity (reverse EAST inhibition) and functionality (basophil degranulation capacity) of allergens were assessed. Heating Ara h 2/6 at 110°C resulted in extensive denaturation, hydrolysis and aggregation of the protein, whilst Ara h 2 and 6 isolated from roasted peanut retained its native conformation. Allergen stimulation of PBMC induced proliferation and Th2 cytokine secretion which was unaffected by thermal processing. Conversely, IgE reactivity and functionality of Ara h 2/6 was decreased by heating. Whilst heating-glycation further reduced the IgE binding capacity of the proteins, it moderated their loss of histamine releasing capacity. Ara h 2 and 6 purified from roasted peanut demonstrated the same IgE reactivity as unheated, native Ara h 2/6. CONCLUSIONS/SIGNIFICANCE: Although no effect of processing on T-cell reactivity was observed, heat induced denaturation reduced the IgE reactivity and subsequent functionality of Ara h 2/6. Conversely, Ara h 2 and 6 purified from roasted peanut retained the structure and IgE reactivity/functionality of the native protein which may explain the allergenic potency of this protein. Through detailed molecular study and allergenicity assessment approaches, this work then gives new insights into the effect of thermal processing on structure/allergenicity of peanut proteins.

Food processing increases casein resistance to simulated infant digestion.

The objective of this study was to determine whether processing could modify the resistance of casein (CN) to digestion in infants. A range of different dairy matrices was manufactured from raw milk in a pilot plant and subjected to in vitro digestion using an infant gut model. Digestion products were identified using MS and immunochemical techniques. Results obtained showed that CNs were able to resist digestion, particularly κ- and αs(2)-CN. Resistant areas were identified and corresponded to fragments hydrophobic at pH 3.0 (gastric conditions) and/or carrying post-translational modifications (phosphorylation and glycosylation). Milk processing led to differences in peptide patterns and heat treatment of milk tended to increase the number of peptides found in digested samples. This highlights the likely impact of milk processing on the allergenic potential of CNs.