Thresholds of clinical reactivity to milk, egg, peanut and sesame in immunoglobulin E-dependent allergies: evaluation by double-blind or single-blind placebo-controlled oral challenges

Electrochemically assisted DNA and thioaromatic assembly as sensing and antifouling interface for food allergens

Food allergies have become a global issue and are estimated to affect approximately 220 million people worldwide. Allergy to peanuts can easily become life-threatening and induce anaphylactic reactions. Mislabeling and cross-contamination during food processing can occur in the frame of world population growth and pose a serious health issue. As the mandatory allergen list is not uniform worldwide, the development of routine analytical strategies with high specificity and sensitivity is a demanding task to aid in the rapid identification of allergenic foods. In this work, an electrochemical aptasensor for Ara h1 peanut allergen was developed by immobilizing the specific aptamer by the inserting method. First, a layer of p-aminothiophenol (p-ATP) was immobilized on the gold surface of screen-printed electrodes (GSPE) to improve the aptamer insertion and reduce the fouling effects at the electrode surface. The grafting of the p-ATP and Ara h1 aptamer on the GSPE surface was monitored by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The resulting disposable aptasensor allowed for indirect electrochemical detection of Ara h1 protein in the presence of 5 mM ferro/ferricyanide as a redox probe. The electrochemical response upon aptamer-target interaction was monitored in the concentration range 1-250 nM, and two limits of detection in the nanomolar range were estimated based on DPV (2.78 nM Ara h1) and EIS (0.82 nM Ara h1) measurements. The aptasensor was successfully applied to real sample analysis.

Generation of an Ovomucoid-Immune scFv Library for the Development of Novel Immunoassays in Hen's Egg Detection

Hen's egg allergy is the second most common food allergy among infants and young children. The possible presence of undeclared eggs in foods poses a significant risk to sensitized individuals. Therefore, reliable egg allergen detection methods are needed to ensure compliance with food labeling and improve consumer protection. This work describes for the first time the application of phage display technology for the generation of a recombinant antibody aimed at the specific detection of hen's ovomucoid. First, a single-chain variable fragment (scFv) library was constructed from mRNA isolated from the spleen of a rabbit immunized with ovomucoid. After rounds of biopanning, four binding clones were isolated and characterized. Based on the best ovomucoid-binding candidate SR-G1, an indirect phage enzyme-linked immunosorbent assay (phage-ELISA) was developed, reaching limits of detection and quantitation of 43 and 79 ng/mL of ovomucoid, respectively. The developed ELISA was applied to the analysis of a wide variety of food products, obtaining a good correlation with a commercial egg detection assay used as a reference. Finally, in silico modeling of the antigen-antibody complex revealed that the main interactions most likely occur between the scFv heavy chain and the ovomucoid domain-III, the most immunogenic region of this allergen.

Cow's milk and egg protein threshold dose distributions in children tolerant to beef, baked milk, and baked egg

BACKGROUND

The use of eliciting doses (EDs) for food allergens is necessary to inform individual dietary advice and food allergen risk-management. The Eliciting Dose 01 (ED01) for milk and egg, calculated from populations of allergic subjects undergoing oral food challenges (OFCs), are 0.2 mg total protein. The respective Eliciting Dose 05 (ED05) is 2.4 mg for milk and 2.3 mg for egg. As about 70% children allergic to such foods may tolerate them when baked, we sought to verify the EDs of that subpopulation of milk and egg-allergic children.

METHODS

We retrospectively assessed consecutive OFC for fresh milk and egg between January 2018 and December 2020 in a population of baked food-tolerant children.

RESULTS

Among 288 children (median age 56 - IQR 36-92.5 months, 67.1% male) included, 87 (30.2%) returned positive OFC results, 38 with milk and 49 with egg. The most conservative ED01 was 0.3 mg total protein (IQR 0.03-2.9) for milk and 14.4 mg total protein (IQR 3.6-56.9) for egg. The respective ED05 was 4.2 (IQR 0.9-19.6) mg for milk and 87.7 (IQR 43-179) mg for egg. Such thresholds are, respectively, 1.5 (milk ED01), 1.75 (milk ED05), 72 (egg ED01), and 38.35 (egg ED05) times higher than the currently used thresholds.

CONCLUSIONS

The subpopulation of children allergic to milk and egg, but tolerant to baked proteins, displays higher reactivity thresholds than the general population of children allergic to milk and egg. Their risk stratification, in both individual and population terms, should consider this difference. In baked milk-tolerant children, milk causes reactions at lower doses than egg in our group of egg-tolerant children. This could be associated with the relative harmlessness of egg compared with milk in the determinism of fatal anaphylactic reactions in children.

Proposal of 0.5 mg of protein/100 g of processed food as threshold for voluntary declaration of food allergen traces in processed food-A first step in an initiative to better inform patients and avoid fatal allergic reactions: A GA²LEN position paper

BACKGROUND

Food anaphylaxis is commonly elicited by unintentional ingestion of foods containing the allergen above the tolerance threshold level of the individual. While labeling the 14 main allergens used as ingredients in food products is mandatory in the EU, there is no legal definition of declaring potential contaminants. Precautionary allergen labeling such as "may contain traces of" is often used. However, this is unsatisfactory for consumers as they get no information if the contamination is below their personal threshold. In discussions with the food industry and technologists, it was suggested to use a voluntary declaration indicating that all declared contaminants are below a threshold of 0.5 mg protein per 100 g of food. This concentration is known to be below the threshold of most patients, and it can be technically guaranteed in most food production. However, it was also important to assess that in case of accidental ingestion of contaminants below this threshold by highly allergic patients, no fatal anaphylactic reaction could occur. Therefore, we performed a systematic review to assess whether a fatal reaction to 5mg of protein or less has been reported, assuming that a maximum portion size of 1kg of a processed food exceeds any meal and thus gives a sufficient safety margin.

METHODS

MEDLINE and EMBASE were searched until 24 January 2021 for provocation studies and case reports in which one of the 14 major food allergens was reported to elicit fatal or life-threatening anaphylactic reactions and assessed if these occurred below the ingestion of 5mg of protein. A Delphi process was performed to obtain an expert consensus on the results.

RESULTS

In the 210 studies included, in our search, no reports of fatal anaphylactic reactions reported below 5 mg protein ingested were identified. However, in provocation studies and case reports, severe reactions below 5 mg were reported for the following allergens: eggs, fish, lupin, milk, nuts, peanuts, soy, and sesame seeds.

CONCLUSION

Based on the literature studied for this review, it can be stated that cross-contamination of the 14 major food allergens below 0.5 mg/100 g is likely not to endanger most food allergic patients when a standard portion of food is consumed. We propose to use the statement "this product contains the named allergens in the list of ingredients, it may contain traces of other contaminations (to be named, e.g. nut) at concentrations less than 0.5 mg per 100 g of this product" for a voluntary declaration on processed food packages. This level of avoidance of cross-contaminations can be achieved technically for most processed foods, and the statement would be a clear and helpful message to the consumers. However, it is clearly acknowledged that a voluntary declaration is only a first step to a legally binding solution. For this, further research on threshold levels is encouraged.

Peanut Can Be Used as a Reference Allergen for Hazard Characterization in Food Allergen Risk Management: A Rapid Evidence Assessment and Meta-Analysis

Regional and national legislation mandates the disclosure of “priority” allergens when present as an ingredient in foods, but this does not extend to the unintended presence of allergens due to shared production facilities. This has resulted in a proliferation of precautionary allergen (“may contain”) labels (PAL) that are frequently ignored by food-allergic consumers. Attempts have been made to improve allergen risk management to better inform the use of PAL, but a lack of consensus has led to variety of regulatory approaches and nonuniformity in the use of PAL by food businesses. One potential solution would be to establish internationally agreed “reference doses,” below which no PAL would be needed. However, if reference doses are to be used to inform the need for PAL, then it is essential to characterize the hazard associated with these low-level exposures. For peanut, there are now published data relating to over 3000 double-blind, placebo-controlled challenges in allergic individuals, but a similar level of evidence is lacking for other priority allergens. We present the results of a rapid evidence assessment and meta-analysis for the risk of anaphylaxis to a low-level allergen exposure for priority allergens. On the basis of this analysis, we propose that peanut can and should be considered an exemplar allergen for the hazard characterization at a low-level allergen exposure.

Probabilistic risk assessment for milk in dark chocolate, cookies and other baked goods with PAL sold in Canada

The risk of having an allergic reaction in milk-allergic individuals consuming products with precautionary allergen labelling (PAL) for milk has been rarely studied in products such as dark chocolate, cookies, and other baked goods. A probabilistic risk assessment model was developed to estimate potential risks. Milk occurrence and contamination levels were reported in a previous article from our group. Dose-response curves for milk were constructed using values (n = 1078) from published double-blind placebo-controlled food challenges. Canadian consumption data was extracted from a national survey, and a homemade survey involving food-allergic Canadians. Milk eliciting doses (ED) were 0.23 (ED₀₁), 1.34 (ED₀₅), 3.42 (ED₁₀), and 16.3 (ED₂₅) mg of milk protein (Log-Normal distribution). Average exposures, per eating occasion, were 24 mg (dark chocolate), 3.9 mg (baked goods), and 0.20 mg (cookies) of milk proteins. The estimated risk of having a milk-induced allergic reaction by consuming foods with PAL for milk was higher for dark chocolate (16%; 15,881/100,000) than baked goods (3.8%; 3802/100,000) or cookies (0.6%; 646/100,000) in milk-allergic Canadians. Dark chocolate, cookies, and baked goods with PAL for milk, should be avoided by milk-allergic Canadians (consuming or not products with PAL) to prevent allergic reactions.

Nano-Biosensing Platforms for Detection of Cow's Milk Allergens: An Overview

Among prevalent food allergies, cow milk allergy (CMA) is most common and may persist throughout the life. The allergic individuals are exposed to a constant threat due to milk proteins' presence in uncounted food products like yogurt, cheese, and bakery items. The problem can be more severe due to cross-reactivity of the milk allergens in the food products due to homologous milk proteins of diverse species. This problem can be overcome by proper and reliable food labeling in order to ensure the life quality of allergic persons. Therefore, highly sensitive and accurate analytical techniques should be developed to detect the food allergens. Here, significant research advances in biosensors (specifically immunosensors and aptasensors) are reviewed for detection of the milk allergens. Different allergic proteins of cow milk are described here along with the analytical standard methods for their detection. Additionally, the commercial status of biosensors is also discussed in comparison to conventional techniques like enzyme-linked immunosorbent assay (ELISA). The development of novel biosensing mechanisms/kits for milk allergens detection is imperative from the perspective of enforcement of labeling regulations and directives keeping in view the sensitive individuals.

Detection and Quantification of Milk Ingredients as Hidden Allergens in Meat Products by a Novel Specific Real-Time PCR Method

Milk ingredients are often included in a wide range of meat products, such as cooked hams and sausages, to improve technological characteristics. However, milk proteins are also important food allergens. The aim of this study was the development of a highly sensitive and specific real-time PCR system targeting the 12S rRNA gene of Bos domesticus for the detection and quantification of milk as an allergenic ingredient in processed meat products. The method was able to achieve an absolute limit of detection (LOD) of 6 fg of milk DNA. Using a normalized approach (∆Ct method) for the detection of milk protein concentrate (MPC), it was possible to obtain sensitivities down to 0.01% (w/w) of MPC in model hams (raw and cooked) and autoclaved sausages, and 0.005% in raw sausage mixtures. The developed systems generally presented acceptable PCR performance parameters, being successfully validated with blind samples, applied to commercial samples, and further compared with an immunochemical assay. Trace amounts of milk material were quantified in two out of 13 samples, but the results mostly infer the excessive practice of the precautionary labeling.

Propofol use in children with allergies to egg, peanut, soybean or other legumes

Propofol is the most commonly administered intravenous agent for anaesthesia in children. However, there are concerns that the emulsified preparation may not be safe in children with an allergy to egg, peanut, soybean or other legumes. We conducted a retrospective study of children with immunologically confirmed egg, peanut, soybean or legume allergy and who underwent general anaesthesia at Princess Margaret Hospital for Children between 2005 and 2015. We extracted details regarding allergy diagnosis, each anaesthetic administered and any adverse events or signs of an allergic reaction in the peri-operative period. A convenience sample of patients without any known food allergies was identified from our prospective anaesthesia research database and acted as a control group. We identified 304 food-allergic children and 649 procedures where propofol was administered. Of these, 201 (66%) had an egg allergy, 226 (74%) had a peanut allergy, 28 (9%) had a soybean allergy and 12 (4%) had a legume allergy. These were compared with 892 allergy-free patients who were exposed to propofol. In 10 (3%) allergy patients and 124 (14%) allergy-free patients, criteria for a possible allergic reaction were met. In nine of the food-allergic children and in all the controls valid non-allergic explanations for the clinical symptoms were found. One likely mild allergic reaction was experienced by a child with a previous history of intralipid allergy. We conclude that genuine serious allergic reaction to propofol is rare and is not reliably predicted by a history of food allergy.

The role of environmental exposure to peanut in the development of clinical allergy to peanut

The prevalence of peanut allergy has increased over the years and still remains one of the most common causes of food-related anaphylaxis. The way in which peanut sensitization occurs has been explored, such as via maternal consumption in pregnancy, via breastmilk and through a disrupted skin barrier. It has previously been shown that environmental exposure to aeroallergens in household dust can be a risk factor for the development of allergic asthma. There is an increasing body of evidence that the combination of cutaneous sensitization via a disrupted skin barrier (ie children with eczema or with filaggrin mutations) and environmental peanut exposure influences the development of peanut allergy. This review aims to explore routes of peanut sensitization and the current evidence on how environmental exposure to peanut affects the development of peanut allergy.

Degradation and removal of soybean allergen in Japanese soy sauce

Soy sauce is a traditional fermented seasoning of Japan and is available throughout the world. The two main raw ingredients of soy sauce are soybean and wheat, both of which are established food allergens. The present study examined the degradation and removal of soybean allergens in soy sauce by immunoblotting with anti‑soybean protein antibody from rabbit and sera from two children with soybean allergy. It was demonstrated that soybean allergens were gradually degraded during the fermentation process, but were not completely degraded in raw soy sauce. During the processes of heat‑treatment and filtration, the soluble soybean allergens in raw soy sauce were denatured to insoluble allergens by heat‑treatment and subsequently completely removed from soy sauce by filtration. Therefore, to reduce the allergenicity of soy sauce, heat‑treatment and filtration are very important processes in addition to the enzymatic degradation during the fermentation of soy sauce.

Food Allergy and Food Poisoning

Taken into account data from which is considered a product not safe, estimate the safe level of a contaminant on food, for example, always have many unavoidable uncertainties. It cannot be overemphasized enough, that this also happens as in any other human activity. In most cases, we hope, to define as clearly as possible the eventual risk associated with particular conditions of exposure to a given substance in food. There are numerous toxic compounds that reside naturally in certain foods that unable these to be consumed above certain limits or even are fully prohibited in some other countries. Chapter starts with a clear explanation of differences and relationships between food allergy and food poisoning, continued with main allergens in food and main toxics. Finally, authors summarize different origins of toxins and allergens (natural from foods, from additives, pollutants and food processing).

Food Allergy and Food Poisoning

Taken into account data from which is considered a product not safe, estimate the safe level of a contaminant on food, for example, always have many unavoidable uncertainties. It cannot be overemphasized enough, that this also happens as in any other human activity. In most cases, we hope, to define as clearly as possible the eventual risk associated with particular conditions of exposure to a given substance in food. There are numerous toxic compounds that reside naturally in certain foods that unable these to be consumed above certain limits or even are fully prohibited in some other countries. Chapter starts with a clear explanation of differences and relationships between food allergy and food poisoning, continued with main allergens in food and main toxics. Finally, authors summarize different origins of toxins and allergens (natural from foods, from additives, pollutants and food processing).

Extractable low mass proteins <30kDa from peanut display elevated antigenicity (IgG-binding) and allergenicity (IgE-binding) in vitro and are attenuated by thermal reactivity with non-peanut food ingredients

Human allergic reactions to peanut proteins and the associated risk of life-threatening anaphylaxis requires vigilant management of peanuts in food processing. Processed forms of peanuts with attenuated antigenicity and less severe immunogenic responses may lower the risk. Molecular subfractions of raw (UP), blanched (BP) and roasted (RP) peanuts were prepared including water-insoluble (P1), water-soluble high mass (>30kDa, P2) and water-soluble low mass (<30kDa, P3) fractions. Products were screened by measuring binding to IgG (polyclonal antibody against peanut allergen) and IgE (sera from peanut-allergic donors, RAST>3). The results showed that IgE titres were highest for total extracts of RP, particularly for P3 fractions of UP and RP, and were affected by further heating. Antigenicity was also modulated by heating in the presence of either peanut oil or non-peanut food ingredients (lactose, coconut oil). Results support several alternative methods for regulating peanut antigenicity using food processing approaches but require further substantiation in larger numbers of allergic and control donor sera.

Mouse models of food allergy: how well do they simulate the human disorder?

Food allergy is a growing health problem with serious concerns due to high potential for fatality. Rapid advances in the knowledge on causes and mechanisms as well as in developing effective prevention/therapeutic strategies are needed. To meet these goals, mouse models that simulate the human disorder are highly desirable. During the past decade, several mouse models of food allergies have been reported. Here, we briefly reviewed the human disorder and then critically evaluated these models seeking answers to the following important questions: To what extent do they simulate the human disorder? What are the strengths and limitations of these models? What are the challenges facing this scientific area? Our analysis suggest that: (i) the mouse models, with inherent strengths and limitations, are available for many major food allergies; there is scope for additional model development and validation; (ii) models mostly simulate the severe forms of human disorder with similar immune and clinical features; (iii) the approaches used to develop some of the mouse models may be questionable; and (iv) the specific mechanisms of sensitization as wells as oral elicitation of fatal reactions in both humans and mice remains incompletely understood and therefore warrants further research.

Sesame allergy threshold dose distribution

BACKGROUND

Sesame is a relevant food allergen in France. Compared to other allergens there is a lack of food challenge data and more data could help sesame allergy risk management. The aim of this study is to collect more sesame challenge data and investigate the most efficient food challenge method for future studies.

METHOD

Records of patients at University Hospital in Nancy (France) with objective symptoms to sesame challenges were collected and combined with previously published data. An estimation of the sesame allergy population threshold was calculated based on individual NOAELs and LOAELs. Clinical dosing schemes at Nancy were investigated to see if the optimal protocol for sesame is currently used.

RESULTS

Fourteen patients (10 M/4 F, 22 ± 14.85 years old) with objective symptoms were added to previously published data making a total of 35 sesame allergic patients. The most sensitive patient reacted to the first dose at challenge of 1.02 mg sesame protein. The ED05 ranges between 1.2 and 4.0 mg of sesame protein (Log-Normal, Log-Logistic, and Weibull models) and the ED10 between 4.2 and 6.2 mg. The optimal food challenge dosing scheme for sesame follows semi-log dose increases from 0.3 to 3000 mg protein.

CONCLUSION

This article provides a valuable update to the existing clinical literature regarding sesame NOAELs and LOAELs. Establishment of a population threshold for sesame could help in increasing the credibility of precautionary labelling and decrease the costs associated with unexpected allergic reactions. Also, the use of an optimal dosing scheme would decrease time spent on diagnostic and thereafter on the economic burden of sesame allergy diagnosis.

Consensus document on the approach to children with allergic reactions after vaccination or allergy to vaccine components

Vaccinations are one of the main public health tools for the control of vaccine-preventable diseases. If a child is identified as having had an allergic reaction to a vaccine, subsequent immunisations will probably be suspended - with the risks such a decision implies. The incidence of severe allergic reactions is very low, ranging between 0.5 and 1 cases/100,000 doses. Rather than the vaccine antigens as such, the causes of allergic reactions to vaccines are often residual protein components of the manufacturing process such as gelatine or egg, and less commonly yeasts or latex. Most vaccine reactions are mild and circumscribed to the injection site; although in some cases severe anaphylactic reactions can be observed. If an immediate-type allergic reaction is suspected at vaccination, or if a child with allergy to some of the vaccine components is scheduled for vaccination, a correct diagnosis of the possible allergic process must be made. The usual vaccine components must be known in order to determine whether vaccination can be safely performed.

Ovomucoid specific immunoglobulin E as a predictor of tolerance to cooked egg

BACKGROUND

Ovomucoid is the dominant allergen in hen's egg. Although several studies evaluated the utility of ovomucoid specific immunoglobulin E (sIgE) levels in predicting baked (e.g., muffin or cupcake) or raw egg food challenge outcomes, studies that evaluated ovomucoid sIgE as a predictor of cooked egg (e.g., scrambled or hard boiled) challenge outcomes are limited.

OBJECTIVE

To determine the relation of ovomucoid sIgE levels with cooked egg food challenge outcomes.

METHODS

A retrospective review of 44 children who underwent cooked egg food challenge and who had the ovomucoid sIgE level measured.

RESULTS

Thirty-six of 44 children (81.8%) passed cooked egg challenge. The ovomucoid sIgE level predicted cooked egg challenge outcome (passed median, <0.35 kU/L [range, <0.35-0.64 kU/L]; failed median, 0.40 kU/L [range, <0.35-3.13 kU/L]; p = 0.004). Ovomucoid sIgE levels correlated with egg white (EW) sIgE levels (Spearman correlation coefficient, 0.588; p < 0.001). Receiver operating characteristic curve analysis of ovomucoid and EW sIgE demonstrated areas under the curve of 0.711 and 0.766, respectively. No significant difference was observed among those immunologic parameters in their abilities to predict cooked egg challenge outcome (p = 0.559).

CONCLUSION

The ovomucoid sIgE level may be helpful in predicting cooked egg challenge outcomes. However, our study did not support a role for ovomucoid sIgE replacing EW sIgE testing in evaluating egg allergy.

β-casomorphin-7 alters μ-opioid receptor and dipeptidyl peptidase IV genes expression in children with atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with heterogeneous clinical phenotypes reflecting genetic predisposition and exposure to environmental factors. Reactions to food may play a significant role especially in young children. Milk proteins are particularly strong allergens and are additional source of bioactive peptides including β-casomorphin-7 (BCM7, Tyr-Pro-Phe-Pro-Gly-Pro-Ile). BCM7 exerts its influence on nervous, digestive, and immune functions via the μ-opioid receptor (MOR). Proline dipeptidyl peptidase IV (DPPIV; EC 3.4.14.5) appears to be the primary degrading enzyme of BCM7. Moreover, DPPIV is known to restrict activity of proinflammatory peptides. BCM7 is considered to modulate an immune response by affecting MOR and DPPIV genes expression. In this study, we determined the MOR and DPPIV genes expression in children diagnosed with a severe form of AD. 40 healthy children and 62 children diagnosed with severe AD (AD score ≥60) were included in the study. Peripheral blood mononuclear cells (PBMCs) from the studied subjects were incubated with the peptide extracts of raw and hydrolysed cow milk with defined β-casein genotypes (A1A1, A2A2 and A1A2) and MOR and DPPIV genes expression was determined with real-time PCR. Incubation PBMCs with peptide extracts from cow milk caused an increase of the MOR gene expression (p<0.05; p<0.001) in AD children with a simultaneous decrease in the DPPIV gene expression (p<0.001). The obtained results supplement the knowledge on the BCM7 participation in AD etiology and provide an important diagnostic tool.

Proteomic identification of allergenic seed proteins, napin and cruciferin, from cold-pressed rapeseed oils

In Finland and France atopic children commonly react to seeds of oilseed rape and turnip rape in skin prick tests (SPT) and open food challenges. These seeds are not as such in dietary use and therefore the routes of sensitization are unknown. Possible allergens were extracted from commercial cold-pressed and refined rapeseed oils and identified by gel-based tandem nanoflow liquid chromatography mass spectrometry (LC-MS/MS). Napin (a 2S albumin), earlier identified as a major allergen in the seeds of oilseed rape and turnip rape, and cruciferin (an 11S globulin), a new potential seed allergen, were detected in cold-pressed oils, but not in refined oils. Pooled sera from five children sensitized or allergic to oilseed rape and turnip rape seeds reacted to these proteins from cold-pressed oil preparations and individual sera from five children reacted to these proteins extracted from the seeds when examined with IgE immunoblotting. Hence cold-pressed rapeseed oil might be one possible route of sensitization for these allergens.

Using a gluten oral food challenge protocol to improve diagnosis of wheat-dependent exercise-induced anaphylaxis

BACKGROUND

Oral wheat plus cofactors challenge tests in patients with wheat-dependent exercise-induced anaphylaxis (WDEIA) produce unreliable results.

OBJECTIVE

We sought to confirm WDEIA diagnosis by using oral gluten flour plus cofactors challenge, to determine the amount of gluten required to elicit symptoms, and to correlate these results with plasma gliadin levels, gastrointestinal permeability, and allergologic parameters.

METHODS

Sixteen of 34 patients with a history of WDEIA and ω5-gliadin IgE underwent prospective oral challenge tests with gluten with or without cofactors until objective symptoms developed. Gluten reaction threshold levels, plasma gliadin concentrations, gastrointestinal permeability, sensitivities and specificities for skin prick tests, and specific IgE levels were ascertained in patients and 38 control subjects.

RESULTS

In 16 of 16 patients (8 female and 8 male patients; age, 23-76 years), WDEIA was confirmed by challenges with gluten alone (n = 4) or gluten plus cofactors (n = 12), including 4 patients with previous negative wheat challenge results. Higher gluten doses or acetylsalicylic acid (ASA) plus alcohol instead of physical exercise were cofactors in 2 retested patients. The cofactors ASA plus alcohol and exercise increased plasma gliadin levels (P < .03). Positive challenge results developed after a variable period of time at peak or when the plateau plasma gliadin level was attained. Positive plasma gliadin threshold levels differed by greater than 100-fold and ranged from 15 to 2111 pg/mL (median, 628 pg/mL). The clinical history, IgE gliadin level, and baseline gastrointestinal level were not predictive of the outcomes of the challenge tests. The challenge-confirmed sensitivity and specificity of gluten skin prick tests was 100% and 96%, respectively.

CONCLUSION

Oral challenge with gluten alone or along with ASA and alcohol is a sensitive and specific test for the diagnosis of WDEIA. Exercise is not an essential trigger for the onset of symptoms in patients with WDEIA.

Development of a genosensor for peanut allergen ARA h 2 detection and its optimization by surface response methodology

A new selective electrochemical genosensor has been developed for the detection of an 86-mer DNA peanut sequence encoding part of the allergen Ara h 2 (conglutin-homolog protein). The method is based on a sandwich format, which presents two advantages: it permits shortening the capture probe and avoids labeling of the target. Screen-printed gold electrodes have been used as platform for the immobilization of oligonucleotides by the well-known S-Au bond. Mixed self-assembled monolayers (SAM), including thiol-modified capture probe and mercaptohexanol, were prepared to achieve an organized, homogeneous and not too compact SAM in which unspecific adsorption of the capture probe would be prevented. The optimization of the sensing phase was carried out using the Design of Experiments (DoE) approach. Traditionally, response optimization is achieved by changing the value of one factor at a time until there is no further improvement. However, DoE involves regulating the important factors so that the result becomes optimal. Optimized conditions were found to be 1.34 µM for capture probe concentration and 3.15 mM for mercaptohexanol (spacer) concentration. When the optimal conditions were employed the analytical performance of the proposed genosensor improved significantly, showing a sensitivity as high as 3 µA/nM, with a linear range from 5×10(-11) to 5×10(-8) M and a detection limit of 10 pM.

Position document: IgE-mediated allergy to egg protein

Egg is the food that most often causes allergy in young Spanish children, with an incidence of 2.4-2.6% in the first 2 years of life. The prevalence of sensitisation and allergy to egg is greater in children with allergy to cow's milk and in those suffering atopic dermatitis. The protein component from egg white is the cause of the allergic response in child. The major allergens in egg white are ovomucoid and ovalbumin. Most of the allergic reactions affect the skin, followed by gastrointestinal and respiratory systems. Egg allergy is one of the most common causes of severe anaphylaxis. The diagnosis of egg allergy is based on the existence of a suggestive clinical history, a positive allergy study and the subsequent application of controlled exposure testing, which represents the gold standard for confirming the diagnosis. The treatment of egg allergy is based on the avoidance of egg protein intake. A subgroup of egg-allergic patients are tolerant to cooked egg. In these cases, only uncooked egg must necessarily be avoided. Maintaining a diet with strict egg avoidance is difficult, and transgressions are relatively common. The patient, family, and school environment should receive education and training in the avoidance of egg and in the management of possible allergic reactions. With an avoidance diet, up to 15-20% of children will remain allergic and the severity of the reactions will increase over the years. In these more severe cases of egg-allergy, it becomes more difficult to adhere to the avoidance diet over the years, with a significant decrease in patient quality of life. Oral tolerance induction can be regarded as a therapeutic option for IgE-mediated egg allergy. The anti-IgE, omalizumab, might become another genuine therapeutic option for food allergy, not only to prevent allergic reactions after a contact with egg, but also as a complementary treatment to oral tolerance induction for egg allergy, with the purpose of reducing adverse reactions. The administration of influenza vaccine to children with egg allergy is safe in children that do not manifest severe reactions after egg intake, and in children who tolerate cooked egg. The triple viral vaccine (MMR) can be given to egg-allergic children in their usual vaccination centre, with no added risk. Different medicinal products can be formulated with egg proteins, and therefore should be avoided in children with egg allergy.

New validated recipes for double-blind placebo-controlled low-dose food challenges

Double-blind placebo-controlled food challenges are considered the most reliable method to diagnose or rule out food allergy. Despite this, there are few validated challenge recipes available. The present study aimed to validate new recipes for low-dose double-blind placebo-controlled food challenges in school children, by investigating whether there were any sensory differences between the active materials containing cow's milk, hen's egg, soy, wheat or cod, and the placebo materials. The challenge materials contained the same hypoallergenic amino acid-based product, with or without added food allergens. The test panels consisted of 275 school children, aged 8-10 and 14-15 yr, respectively, from five Swedish schools. Each participant tested at least one recipe. Standardized blinded triangle tests were performed to investigate whether any sensory differences could be detected between the active and placebo materials. In our final recipes, no significant differences could be detected between the active and placebo materials for any challenge food (p > 0.05). These results remained after stratification for age and gender. The taste of challenge materials was acceptable, and no unfavourable side effects related to test materials were observed. In summary, these new validated recipes for low-dose double-blinded food challenges contain common allergenic foods in childhood; cow's milk, hen's egg, soy, wheat and cod. All test materials contain the same liquid vehicle, which facilitates preparation and dosing. Our validated recipes increase the range of available recipes, and as they are easily prepared and dosed, they may facilitate the use of double-blind placebo-controlled food challenges in daily clinical practice.

Analysis of crude protein and allergen abundance in peanuts (Arachis hypogaea cv. Walter) from three growing regions in Australia

The effects of plant growth conditions on concentrations of proteins, including allergens, in peanut ( Arachis hypogaea L.) kernels are largely unknown. Peanuts (cv. Walter) were grown at five sites (Taabinga, Redvale, Childers, Bundaberg, and Kairi) covering three commercial growing regions in Queensland, Australia. Differences in temperature, rainfall, and solar radiation during the growing season were evaluated. Kernel yield varied from 2.3 t/ha (Kairi) to 3.9 t/ha (Childers), probably due to differences in solar radiation. Crude protein appeared to vary only between Kairi and Childers, whereas Ara h 1 and 2 concentrations were similar in all locations. 2D-DIGE revealed significant differences in spot volumes for only two minor protein spots from peanuts grown in the five locations. Western blotting using peanut-allergic serum revealed no qualitative differences in recognition of antigens. It was concluded that peanuts grown in different growing regions in Queensland, Australia, had similar protein compositions and therefore were unlikely to show differences in allergenicity.

Double-blind, placebo-controlled food challenges in Brazilian children: adaptation to clinical practice

BACKGROUND

A double-blind, placebo-controlled food challenge (DBPCFC) is considered the gold standard for diagnosing food allergy, but because of methodological difficulties it is rarely conducted in clinical practice, especially in paediatric patients. The purpose of the study was to propose a DBPCFC protocol that is adapted to our conditions for the diagnosis of an IgE-mediated cow's milk allergy (CMA) in a Brazilian reference centre for paediatric allergies.

METHODS

This study includes the experimental phase (choice of materials, adjustments made to protocols described in the literature) and the test execution phase. DBPCFCs were performed in 58 patients aged 1-15 years who were separated into two groups: Group 1 (n=39), sex 1.6 M:F, 5.3 years median age, suggestive history of IgE-mediated CMA; and Group 2 (n=19), sex 1.4 M:F, 8.3 years median age with symptoms not associated with milk ingestion and laboratory data not compatible with IgE-mediated CMA.

RESULTS

The materials were standardised for testing: containers and disposable products, low-lactose cow's milk (CM) and vehicles, such as natural fruit juice, vegetable soup and soybean-based beverages. Each DBPCFC was performed in a single day with two blind, randomised phases with a 2-h interval between them. The milk doses were gradually increased and offered in regular intervals of 15-30 min. Following negative or inconclusive results, patients underwent an open oral challenge test with 200 mL of low-lactose CM.

CONCLUSIONS

The proposed adaptation for the DBPCFC allowed to implement this important test for the diagnosis of IgE-mediated CMA in a reference centre for paediatric allergies. It was considered feasible and safe if performed in an appropriate setting with physician supervision.

Double-blind placebo-controlled food challenges in children with alleged cow's milk allergy: prevention of unnecessary elimination diets and determination of eliciting doses

Background

Children with cow’s milk allergy (CMA) need a cow’s milk protein (CMP) free diet to prevent allergic reactions. For this, reliable allergy-information on the label of food products is essential to avoid products containing the allergen. On the other hand, both overzealous labeling and misdiagnosis that result in unnecessary elimination diets, can lead to potentially hazardous health situations. Our objective was to evaluate if excluding CMA by double-blind placebo-controlled food challenge (DBPCFC) prevents unnecessary elimination diets in the long term. Secondly, to determine the minimum eliciting dose (MED) for an acute allergic reaction to CMP in DBPCFC positive children.

Methods

All children with suspected CMA under our care (Oct’05 - Jun’09) were prospectively enrolled in a DBPCFC. Placebo and verum feedings were administered on two randomly assigned separate days. The MED was determined by noting the ‘lowest observed adverse effect level’ (LOAEL) in DBPCFC-positive children. Based on the outcomes of the DBPCFC a dietary advice was given. Parents were contacted by phone several months later about the diet of their child.

Results

116 children were available for analysis. In 76 children CMA was rejected. In 60 of them CMP was successfully reintroduced, in 2 the parents refused introduction, in another 3 the parents stopped reintroduction. In 9 children CMA symptoms reappeared. In 40 children CMA was confirmed. Infants aged ≤ 12 months in our study group have a higher cumulative distribution of MED than older children.

Conclusions

Excluding CMA by DBPCFC successfully stopped unnecessary elimination diets in the long term in most children. The MEDs form potential useful information for offering dietary advice to patients and their caretakers.

Outcome of oral food challenges in children in relation to symptom-eliciting allergen dose and allergen-specific IgE

BACKGROUND

Oral food challenge (FC) protocols are discussed with reference to starting doses, dose increments, safety, and predictability of results. The aim of this study was to evaluate the relation of eliciting allergen doses, specific IgE levels and predictive factors to the outcome of FCs in children.

METHODS

In 869 children (median age 1.2 years), FCs were performed with cow's milk (n = 633), hen's egg (n = 456), wheat (n = 265) and/or soy (n = 317) starting at 3-5 mg of protein. Each of the seven doses was administered every 30 min using semi-log increases. Severity of symptoms was graded from I to V. IgE was determined prior to challenges.

RESULTS

Of the children allergic to egg or milk, 9% and 10%, respectively, experienced reactions already at the first dose. Of these, 14% (egg) and 4% (milk) experienced grade IV reactions. In contrast, few children reacted to the first doses of wheat or soy, and most reactions occurred after the maximum dose. For all allergens, grade V reactions did not occur. However, grade IV reactions were seen at all eliciting doses. Elevated specific IgE level, young age and a history of atopic dermatitis were associated with a positive challenge outcome for milk or egg, and also IgE levels were associated with lower eliciting allergen doses and more severe symptoms.

CONCLUSION

Oral FCs bear a risk of severe reactions at all dose levels. Doses of 3-5 mg protein induced symptoms in up to 10% of children allergic to milk or egg. However, food-specific IgE levels are of limited clinical value for the estimation of FC reactions.

A longitudinal study of resolution of allergy to well-cooked and uncooked egg

BACKGROUND

Egg allergy is common and although resolution to uncooked egg has been demonstrated, there is lack of evidence to guide reintroduction of well-cooked egg.

OBJECTIVES

To examine the rate of resolution to well-cooked, compared with uncooked egg in children, and safety of egg challenges.

METHOD

A longitudinal study of egg-allergic children from 2004 to 2010, who underwent challenge with well-cooked and if negative, uncooked egg. Participants underwent repeat annual challenges and egg-specific IgE measurement.

RESULTS

One hundred and eighty-one open egg challenges were performed in 95 children whose median age of allergy onset was 12 months. Fifty-three of 95 (56%) had at least one annual repeat challenge. Pre-study historical reactions occurred to baked egg in five (5%), lightly cooked in 58 (61%) and uncooked in nine (9%); respiratory reactions occurred in 11 (12%) and seven (7%) had anaphylaxis; adrenaline was used during five reactions. There were 77 well-cooked and 104 uncooked egg challenges. Tolerance was gained twice as rapidly to well-cooked than uncooked egg (median 5.6 vs. 10.3 years; P<0.0001) and continued to 13 years; hazard ratio 2.23 (95% confidence interval 1.6-3.9). Nearly 1/3 had resolved allergy to well-cooked egg at 3 years and 2/3 at 6 years. Of 28/77 (37%) positive well-cooked egg challenges, 65% had cutaneous symptoms, 68% gastrointestinal and 39% rhinitis, with no other respiratory reactions. Adrenaline was not required. CONCLUSIONS AND CLINICAL RELEVANCE RESOLUTION: of egg allergy takes place over many years, with children outgrowing allergy to well-cooked egg approximately twice as quickly as they outgrow allergy to uncooked egg. There were no severe reactions to well-cooked egg challenge, and adrenaline was not required. Our data support initiation of home reintroduction of well-cooked egg from 2 to 3 years of age in children with previous mild reactions and no asthma. Resolution continues to occur in older children, so that despite an earlier positive challenge, attempts at reintroduction should be continued.

Clinical thresholds to egg, hazelnut, milk and peanut: results from a single-center study using standardized challenges

BACKGROUND

Large studies of individual thresholds and risk profiles for foods are sparse. Previous reports indicate that thresholds adjusted for the protein content in foods would be comparable.

OBJECTIVE

To establish and compare clinical threshold values for egg, hazelnut, milk and peanut, and correlating them to severity of symptoms.

METHODS

Seven hundred eighty-one challenges were performed in 487 patients (age range, 0.5-73.5 years). Using interval censoring survival analysis, the dose distribution of thresholds was fitted to a log-normal function. Symptom score was correlated to thresholds.

RESULTS

Based on the 405 challenges resulting in objective signs, similar distribution of thresholds for hazelnut, milk, and peanut challenges were found, whereas individuals with egg allergy were bimodally distributed with a high or a low threshold. Eliciting dose in 10% (95% confidence interval) was 42.9 (24-76.8) mg whole eggs, 133.8 (95.9-186.6) mg whole hazelnut, 106.5 (59.7-190.6) mg roasted peanut, and 2.9 (1.5-5.4) mL milk. Adults showed more severe symptoms and signs than children, and peanut caused more severe reactions than the 3 other foods.

CONCLUSION

Thresholds for the different foods were not comparable, and eliciting dose for the 4 foods differed, even if adjusted for protein content. Increasing age but not a low threshold dose is associated with severe symptoms on challenge. Peanuts elicit more severe reactions than the other foods.

Almond allergens: molecular characterization, detection, and clinical relevance

Almond ( Prunus dulcis ) has been widely used in all sorts of food products (bakery, pastry, snacks), mostly due to its pleasant flavor and health benefits. However, it is also classified as a potential allergenic seed known to be responsible for triggering several mild to life-threatening immune reactions in sensitized and allergic individuals. Presently, eight groups of allergenic proteins have been identified and characterized in almond, namely, PR-10 (Pru du 1), TLP (Pru du 2), prolamins (Pru du 2S albumin, Pru du 3), profilins (Pru du 4), 60sRP (Pru du 5), and cupin (Pru du 6, Pru du γ-conglutin), although only a few of them have been tested for reactivity with almond-allergic sera. To protect sensitized individuals, labeling regulations have been implemented for foods containing potential allergenic ingredients, impelling the development of adequate analytical methods. This work aims to present an updated and critical overview of the molecular characterization and clinical relevance of almond allergens, as well as review the main methodologies used to detect and quantitate food allergens with special emphasis on almond.

Development of a standardized low-dose double-blind placebo-controlled challenge vehicle for the EuroPrevall project

BACKGROUND

  Double-blind placebo-controlled food challenge (DBPCFC) is the gold standard for diagnosing food allergy. Standardized materials and protocols are essential for comparing DBPCFC results for multicentre studies such as EuroPrevall. This required the development and piloting of a standardized vehicle and low-dose protocol for confirming food allergy and determination of minimum eliciting doses (MEDs).

METHODS

  A low-dose DBPCFC protocol was developed, with eight titrated protein doses from 3 μg to 1 g. This was delivered using a simple, microbiologically stable food base incorporating allergenic food ingredients manufactured at three sites and centrally distributed to clinical centres. Allergen blinding was assessed by a professional sensory testing panel using a triangle test. Homogeneity and allergen content were confirmed by ELISA and clinical efficacy was assessed in a pilot study, using celeriac and hazelnut as exemplars.

RESULTS

  Celeriac and hazelnut ingredients were sufficiently blinded in the dessert. The dessert meals were successfully piloted with hazelnut in allergy clinics in Spain, the Netherlands and Italy and with celeriac and hazelnut in Zurich. The challenges elicited a range of subjective and objective reactions ranging in severity from mild itching of the oral mucosa to bronchospasm.

CONCLUSIONS

  A standardized challenge vehicle proven to sufficiently blind processed, powdered hazelnut and celeriac ingredients and that can be reproducibly manufactured has been developed. This pilot study shows that the vehicle is promising for the confirmation of food allergy and determination of MEDs in adults and children with body weight >28.8 kg (approximately 7-11 years old).

Food production and processing considerations of allergenic food ingredients: a review

Although most consumers show no adverse symptoms to food allergens, health consequences for sensitized individuals can be very serious. As a result, the Codex General Standard for the Labelling of Prepackaged Foods has specified a series of allergenic ingredients/substances requiring mandatory declaration when present in processed prepackaged food products. Countries adhering to international standards are required to observe this minimum of eight substances, but additional priority allergens are included in the list in some countries. Enforcement agencies have traditionally focused their effort on surveillance of prepackaged goods, but there is a growing need to apply a bottom-up approach to allergen risk management in food manufacturing starting from primary food processing operations in order to minimize the possibility of allergen contamination in finished products. The present paper aims to review food production considerations that impact allergen risk management, and it is directed mainly to food manufacturers and policy makers. Furthermore, a series of food ingredients and the allergenic fractions identified from them, as well as the current methodology used for detection of these allergenic foods, is provided.

Walnut allergy in peanut-allergic patients: significance of sequential epitopes of walnut homologous to linear epitopes of Ara h 1, 2 and 3 in relation to clinical reactivity

BACKGROUND

Peanut allergy is a frequent and potentially life-threatening food allergy. Despite the large taxonomic distance between the plants, peanut-allergic patients often react to tree nuts such as walnuts. While the allergens of peanut and walnut have a high degree of homology in their amino-acid sequences, it is unknown whether this similarity is responsible for the observed co-reactivity. Therefore, we analyzed the binding of specific IgE antibodies to sequential epitopes of peanut and walnut in peanut-allergic patients with and without walnut allergy.

METHODS

The IgE binding to previously described sequential epitopes of peanut and the homologous regions of walnut was assessed in 32 peanut-allergic patients using a peptide microarray technology. Twelve patients had a clinically relevant walnut allergy and 20 were tolerant to walnut. Inhibition assays with peanut peptides and corresponding walnut sequences were performed to show specific binding to sequential epitopes.

RESULTS

No differences in the recognition of sequential epitopes could be found between peanut-allergic patients with or without walnut allergy. Only a few patients showed IgE binding to walnut sequences that corresponded to sequential epitopes of peanut. In the inhibition assays, no relevant cross-reacting IgE antibodies could be detected for the peptides analyzed.

CONCLUSION

Our results indicate that although they share a rather high degree of homology with the corresponding regions of walnut allergens, the sequence stretches previously identified as sequential IgE binding epitopes of Ara h 1, Ara h 2 and Ara h 3 have no IgE binding equivalents in walnut allergens.