The distribution of individual threshold doses eliciting allergic reactions in a population with peanut allergy

Novel post-translationally cleaved Ara h 2 proteoforms: Purification, characterization and IgE-binding properties

The 2S albumins Ara h 2 and Ara h 6 have been shown to be the most important source of allergenicity in peanut. Several isoforms of these allergens have been described. Using extraction and liquid chromatography we isolated proteins with homology to Ara h 2 and characterized hitherto unknown Ara h 2 proteoforms with additional post-translational cleavage. High-resolution mass spectrometry located the cleavage site on the non-structured loop of Ara h 2 while far UV CD spectroscopy showed a comparable structure to Ara h 2. The cleaved forms of Ara h 2 were present in genotypes of peanut commonly consumed. Importantly, we revealed that newly identified Ara h 2 cleaved proteoforms showed comparable IgE-binding using sera from 28 peanut-sensitized individuals, possessed almost the same IgE binding potency and are likely similarly allergenic as intact Ara h 2. This makes these newly identified forms relevant proteoforms of peanut allergen Ara h 2.

Utility of food allergy thresholds

Food allergy is a prevalent disease worldwide that is a significant quality-of-life burden, and accidental exposures to food allergens may elicit severe, life-threatening reactions such as anaphylaxis. The threshold level, or the dose that triggers an allergic reaction determined by oral food challenges, varies considerably among individuals suffering from food allergies. Moreover, IgE concentration, diversity, or function can only partially explain this variation in threshold; pathogenic effector TH2 cells have also been found to contribute to the eliciting dose. Though very sensitive to cofactors such as physical activity/stress, the threshold is a stable and reproducible feature of an individual's allergy over periods of many months, made clear in the past several years from treatment studies in which repeated threshold determination has been used as a treatment outcome; however, there also seem to be age-related changes at a population level. More routine determination of food allergy thresholds may help patients stratify risk to improve the management of their food allergy. Precautionary allergen labeling, such as "may contain" labels, often causes confusion since they are inconsistent and regularly contain little to trace allergen residues; thus, food products with such labeling may be unnecessarily avoided. Population-based eliciting dose levels have been determined in the literature; patients at lower risk with higher thresholds may be more confident with introducing foods with precautionary allergen labels. Understanding a patient's threshold level could aid in shared decision-making to determine the most suitable treatment options for patients, including the starting dose for oral immunotherapy and/or the use of biologics.

Oral immunotherapy for children with a high-threshold peanut allergy

BACKGROUND

Between 25% and 30% of children with peanut allergy (PA) have a relatively high-threshold peanut allergy (HTPA), with a single maximal tolerated dose (SMTD) higher than 100 mg of peanut protein (PP). However, this threshold may decrease with time, age, exercise, illness, sleep deprivation, and other covariates.

OBJECTIVE

To explore the feasibility of a simplified oral immunotherapy (OIT) protocol in a group of children with HTPA.

METHODS

Children with PA with an SMTD higher than 100 mg were placed on a 40-week OIT protocol of either 300 mg/d of PP or 100 mg/d for 20 weeks followed by 300 mg/d for 20 weeks. A repeat open peanut food challenge was performed after 40 weeks of treatment and at a 6-month follow-up visit. After the 40-week challenge, all children received a maintenance dosage of 2 gPP 3 times a week.

RESULTS

A total of 28 children with HTPA were enrolled, with 56% boys, 89% younger than 6 years old, and a mean SMTD of 304 mg (95% confidence interval 229-378). All were placed on the described OIT protocol. Overall, 2 children were not compliant and 3 had allergic reactions at home on the dose previously tolerated in clinic, 23 completed the 40-week protocol, and all were able to consume 2 g of PP. The mean tolerated dosage at the 6-month follow-up was 8 g. This enabled most children age-appropriate dietary inclusion of peanut-containing products.

CONCLUSION

In children with HTPA, a simple, fixed-dose OIT can be both safe and efficacious.

Organ-specific symptom patterns during oral food challenge in children with peanut and tree nut allergy

BACKGROUND

Peanut and tree nut allergies are common in childhood and often severe in nature. The clinical picture shows a wide variety of symptoms.

OBJECTIVE

To analyze the distribution of clinical symptoms and severity during oral food challenges (OFC) in children.

METHODS

Analysis of 1.013 prospectively recorded, positive OFCs with peanut (n = 607), hazelnut (n = 266), walnut (n = 97), and cashew (n = 43). Symptoms were categorized as immediate-type skin, gastrointestinal, upper and lower respiratory, cardiovascular symptoms, and eczema exacerbation. Symptom severity and treatment were recorded.

RESULTS

Skin symptoms presented in 78%, followed by gastrointestinal (47%), upper (42%), and lower respiratory symptoms (32%). Cardiovascular symptoms presented in 6%. In three-quarter of the reactions, more than one organ was involved. Importantly, severe reactions occurred at every dose level. Peanut- and cashew-allergic patients had a higher relative risk of gastrointestinal symptoms compared with hazelnut- and walnut-allergic patients. Patients without vomiting had a 1.7 times higher risk developing immediate-type skin and/or lower respiratory symptoms. Three-quarter of the patients ever had eczema but worsening presented in only 10.5% of the OFCs. In patients with multiple food allergies, organs involved, eliciting dose and severity differed between allergens.

CONCLUSION

Although comparisons between allergen groups with different clinical history, severity, comorbidities and laboratory data are difficult and might contain bias, our data confirm the high allergenic potential of peanut and tree nuts. The rare occurrence of eczema worsening emphasizes that avoidance diets of peanuts and tree nuts to cure eczema seem to be unnecessary and may hamper tolerance maintenance.

Diagnostic utility of the basophil activation test in natto-induced hypersensitivity

BACKGROUND

Natto (fermented soybeans)-induced hypersensitivity is characterized by delayed symptom onset that hampers diagnosis. We aimed to clarify the clinical utility of the basophil activation test (BAT) in the diagnosis of natto-induced hypersensitivity.

METHODS

Five patients with a history of anaphylaxis and chronic urticaria suspected of natto-induced hypersensitivity and seven with chronic spontaneous urticaria clinically unrelated to natto were enrolled in the patient and control groups, respectively. The BAT was performed with two incubation times, 15 min and 1 h, in combination with various concentrations of natto-mucilage extract.

RESULTS

In controls, CD203c levels in basophils remained low in the 15-min incubation but were significantly increased in the 1-h incubation. In the patient group, in the 15-min condition, basophil CD203c was significantly upregulated by natto mucilage but not by soybean vs controls (P = 0.001). Low concentrations of natto mucilage were sufficient to upregulate basophil CD203c in the anaphylaxis cases, but high concentrations were required to induce the same effect in the urticaria cases. Finally, the dose-dependent pattern of the BAT results differed significantly between the anaphylaxis and urticaria cases (P = 0.006). Thus, a strong background reaction was observed in the BAT with 1 h incubation; 15 min of incubation was sufficient to identify patients with natto-induced hypersensitivity and may distinguish the clinical phenotype of natto-induced hypersensitivity, i.e., anaphylaxis or urticaria.

CONCLUSIONS

The BAT with a 15-min incubation period is useful in diagnosing natto-induced hypersensitivity.

White paper on peanut allergy - part 1: Epidemiology, burden of disease, health economic aspects

Peanuts are Leguminosae, commonly known as the legume or pea family, and peanut allergy is among the most common food allergies and the most common cause of fatal food reactions and anaphylaxis.

The prevalence of peanut allergy increased 3.5-fold over the past two decades reaching 1.4–2% in Europe and the United States. The reasons for this increase in prevalence are likely multifaceted. Sensitization via the skin appears to be associated with the development of peanut allergy and atopic eczema in infancy is associated with a high risk of developing peanut allergy.

Until recently, the only possible management strategy for peanut allergy was strict allergen avoidance and emergency treatment including adrenaline auto-injector in cases of accidental exposure and reaction.

This paper discusses the various factors that impact the risks of peanut allergy and the burden of self-management on peanut-allergic children and their caregivers.

Bayesian hierarchical evaluation of dose-response for peanut allergy in clinical trial screening

Risk-based labeling based on the minimal eliciting doses (EDs) in sensitized populations is a potential replacement for precautionary allergen labeling of food allergens. We estimated the dose-response distribution for peanut allergen using data from double-blind placebo-controlled food challenges (DBPCFCs) conducted in the US at multiple sites, testing a population believed to be similar to the general U.S. food allergic population. Our final (placebo-adjusted) dataset included 548 challenges of 481 subjects. Bayesian hierarchical analysis facilitated model fitting, and accounted for variability associated with various levels of data organization. The data are best described using a complex hierarchical structure that accounts for inter-individual variability and variability across study locations or substudies. Bayesian model averaging could simultaneously consider the fit of multiple models, but the Weibull model dominated so strongly that model averaging was not needed. The ED01 and ED05 (and 95% credible intervals) are 0.052 (0.021, 0.13) and 0.49 (0.22, 0.97) mg peanut protein, respectively. Accounting for challenges with severe reactions at the LOAEL, by using the dose prior to the LOAEL as the new LOAEL, the ED01 drops to 0.029 (0.014, 0.074) mg peanut protein. Our results could aid in establishing improved food labeling guidelines in the management of food allergies.

Peanut allergy diagnosis: A 2020 practice parameter update, systematic review, and GRADE analysis

Given the burden of disease and the consequences of a diagnosis of peanut allergy, it is important that peanut allergy be accurately diagnosed so that an appropriate treatment plan can be developed. However, a test that indicates there is peanut sensitization present (eg, a "positive" test) is not always associated with clinical reactivity. This practice parameter addresses the diagnosis of IgE-mediated peanut allergy, both in children and adults, as pertaining to 3 fundamental questions, and based on the systematic reviews and meta-analyses, makes recommendations for the clinician who is evaluating a patient for peanut allergy. These questions relate to when diagnostic tests should be completed, which diagnostic tests to utilize, and the utility (or lack thereof) of diagnostic testing to predict the severity of a future allergic reaction to peanut.

Novel insights regarding anaphylaxis in children - With a focus on prevalence, diagnosis, and treatment

Anaphylaxis is a serious allergic reaction that occurs rapidly and causes a life-threatening response involving the whole body. This reaction often leads to difficulty in breathing and can result in death. The estimated prevalence of anaphylaxis is 0.05%-2%, which is reported to be increasing in children. Although drugs and venom are the most common causes of anaphylaxis in adults, food is the most common cause of anaphylaxis in children. An interesting association between food-dependent exercise-induced anaphylaxis (FDEIA) and oral immunotherapy (OIT) has recently been reported. A provocation test to determine the diagnostic and augmenting factors of FDEIA has been reported in recent years. Remarkably, several articles showed allergic symptoms without exercise in children with FDEIA and in those with FDEIA development after OIT. Regarding OIT, full-dose OIT poses a risk of adverse reactions, including anaphylaxis. Recent trials have shown the efficacy and safety of low-dose OIT in patients with food-induced anaphylaxis. In this review, we summarized the novel insights regarding anaphylaxis in the pediatric population.

Subpixel detection of peanut in wheat flour using a matched subspace detector algorithm and near-infrared hyperspectral imaging

The detection of adulterations in food powder products represents a high interest especially when it concerns the health of the consumers. The food industry is concerned by peanut adulteration since it is a major food allergen often used in transformed food products. Near-infrared hyperspectral imaging is an emerging technology for food inspection. It was used in this work to detect peanut flour adulteration in wheat flour. The detection of peanut particles was challenging for two reasons: the particle size is smaller than the pixel size leading to impure spectral profiles; peanut and wheat flour exhibit similar spectral signatures and variability. A Matched Subspace Detector (MSD) algorithm was designed to take these difficulties into account and detect peanut adulteration at the pixel scale using the associated spectrum. A set of simulated data was generated to overcome the lack of reference values at the pixel scale and to design appropriate MSD algorithms. The best designs were compared by estimating the detection sensitivity. Defatted peanut flour and wheat flour were mixed in eight different proportions (from 0.02% to 20%) to test the detection performances of the algorithm on real hyperspectral measurements. The number and positions of the detected pixels were investigated to show the relevancy of the results and validate the design of the MSD algorithm. The presented work proved that the use of hyperspectral imaging and a fine-tuned MSD algorithm enables to detect a global adulteration of 0.2% of peanut in wheat flour.

Quantitative allergenicity risk assessment of food products containing yellow mealworm (Tenebrio molitor)

Insect-based foods are starting to enter the EU market, raising concerns about their safety. Allergic consumers might be exposed to even a greater risk, since insects have proven to trigger allergic symptoms, particularly in patients sensitised to crustaceans. Current legislation does not enforce producers to include insects in the list of allergenic ingredients. Food allergenicity risk assessment (FARA) is still at its infancy, and the debate on the need to define allergen thresholds is open. In this paper, we aimed at applying the concepts of stochastic quantitative FARA to describe present and future scenarios of exposure to foods containing Tenebrio molitor, the yellow mealworm. According to our risk characterisation, mealworm-based food products represent a major risk for individuals allergic to crustaceans to develop symptoms after the consumption of a dose lower than a serving size. Moreover, other allergic consumers might be at risk. A correct labelling of insect containing foods would help safeguarding the health of EU allergic consumers. Quantitatively assessing the risk of allergenicity provides a clear description of the problem, facilitating the decisional process of the risk manager, supporting the implementation of effective allergen management procedures and limiting the phenomenon of uninformative precautionary labelling.

How to manage food allergy in nursery or school

PURPOSE OF REVIEW

The aim of this review is to describe effective management strategies in nursery or school based upon research findings.

RECENT FINDINGS

The prevalence of food allergy and number of emergency department visits for food-related anaphylaxis are increasing in children and adolescents. As there is currently no cure, the most effective strategy to decrease allergic reactions is food allergen avoidance. However, allergic reactions are inevitable in both food allergic children as well as in first-time reactors. Misconceptions exist on the safety of products with advisory labels and questions remain on whether school-wide bans decrease the risk of allergic reactions in school. Recent legislation has prompted schools to consider requiring unassigned epinephrine autoinjectors to better manage those who have allergic reactions in nursery or school.

SUMMARY

A collective effort is required to keep children with food allergies safe at school. Families, healthcare providers, and school personnel should be informed on food allergen avoidance strategies, symptoms consistent with allergic reactions and anaphylaxis, how to respond to allergic reactions, and the impact the diagnosis of food allergy may have on quality of life for affected children and their families.

Analysis of a Large Standardized Food Challenge Data Set to Determine Predictors of Positive Outcome Across Multiple Allergens

Background: Double-blind placebo-controlled food challenges (DBPCFCs) remain the gold standard for the diagnosis of food allergy; however, challenges require significant time and resources and place the patient at an increased risk for severe allergic adverse events. There have been continued efforts to identify alternative diagnostic methods to replace or minimize the need for oral food challenges (OFCs) in the diagnosis of food allergy.

Methods: Data was extracted for all IRB-approved, Stanford-initiated clinical protocols involving standardized screening OFCs to a cumulative dose of 500 mg protein to any of 11 food allergens in participants with elevated skin prick test (SPT) and/or specific IgE (sIgE) values to the challenged food across 7 sites. Baseline population characteristics, biomarkers, and challenge outcomes were analyzed to develop diagnostic criteria predictive of positive OFCs across multiple allergens in our multi-allergic cohorts.

Results: A total of 1247 OFCs completed by 427 participants were analyzed in this cohort. Eighty-five percent of all OFCs had positive challenges. A history of atopic dermatitis and multiple food allergies were significantly associated with a higher risk of positive OFCs. The majority of food-specific SPT, sIgE, and sIgE/total IgE (tIgE) thresholds calculated from cumulative tolerated dose (CTD)-dependent receiver operator curves (ROC) had high discrimination of OFC outcome (area under the curves > 0.75). Participants with values above the thresholds were more likely to have positive challenges.

Conclusions: This is the first study, to our knowledge, to not only adjust for tolerated allergen dose in predicting OFC outcome, but to also use this method to establish biomarker thresholds. The presented findings suggest that readily obtainable biomarker values and patient demographics may be of use in the prediction of OFC outcome and food allergy. In the subset of patients with SPT or sIgE values above the thresholds, values appear highly predictive of a positive OFC and true food allergy. While these values are relatively high, they may serve as an appropriate substitute for food challenges in clinical and research settings.

Low-dose oral immunotherapy for children with anaphylactic peanut allergy in Japan

BACKGROUND

Oral immunotherapy (OIT) is a promising treatment for persons with allergy; however, it can also cause adverse allergic reactions. In this study, we investigated the efficacy of low-dose OIT for anaphylactic peanut allergy.

METHODS

Twenty-four children (median age, 9.6 years) with anaphylaxis to peanuts were hospitalized for 5 days and then gradually fed increasing amounts of peanut powder up to 133 mg/day. One year later, they underwent an oral food challenge after 2 weeks of peanut avoidance. Those who were asymptomatic after ingesting 795 mg of peanut protein were defined as having achieved sustained unresponsiveness. We measured peanut- and Ara h2-specific immunoglobulin (Ig) E, IgG, and IgG4 levels at 0, 1, 3, 6, and 12 months in the OIT group and at 0 and 12 months in the control group.

RESULTS

At baseline, all children in the OIT group and 8 in the control group had a history of anaphylaxis. The median peanut-/Ara h2-specific IgE levels in the OIT and control groups were 55.4/48.6 and 58.2/38.1 kUa/L, respectively. One year later, 8 (33.3%) children in the OIT group exhibited sustained unresponsiveness, while none in the control group did. In the OIT group, the median peanut-specific IgE levels significantly increased to 194.0 kUa/L, after 1 month and then significantly decreased to 57.5 kUa/L at 12 months. Meanwhile, the median peanut- and Ara h2-specific IgG and IgG4 levels increased significantly after 1 month.

CONCLUSION

Low-dose OIT induces immunological changes and has the capability of achieving sustained unresponsiveness in children with peanut anaphylaxis.

Peanut gastrointestinal delivery oral immunotherapy in adolescents: Results of the build-up phase of a randomized, double-blind, placebo-controlled trial (PITA study)

BACKGROUND

Oral immunotherapy to peanut is effective in desensitizing patients but has significant side effects including anaphylaxis and gastrointestinal symptoms. In most protocols, peanut is administered in a vehicle food.

OBJECTIVE

In an exclusively adolescent population, we tested a new approach using sealed capsules of peanut (gastrointestinal delivery oral immunotherapy or GIDOIT) to bypass the upper gastrointestinal tract. The primary aim was to assess the efficacy of the oral build-up phase of GIDOIT and the secondary aim to analyse its safety.

METHODS

Adolescents with a history of a clinical allergic reaction after peanut ingestion were included in a 2-armed, parallel-design, individually randomized, double-blind, placebo-controlled, multicentre trial after a positive double-blind placebo-controlled oral food challenge (DBPCFC1). A central randomization centre used computer-generated tables to allocate treatments. Peanut (or placebo) capsules were ingested daily over a period of 24 weeks with increments every 2 weeks from 2 to 400 mg of peanut protein (pp). Primary outcome was tolerance of 400 mg of pp at DBPCFC2.

RESULTS

Thirty patients were included between September 2013 and May 2014. At DBPCFC2, unresponsiveness to 400 mg of pp was achieved in 17/21 peanut group patients (2 withdrawn patients) and 1/9 in the placebo group (Intention-to-treat analysis, P < .001, absolute difference = 0.7, 95%IC 0.43 0.96). Oropharyngeal symptoms were equally frequent in both groups. No dysphagia or other signs of eosinophilic oesophagitis occurred. Digestive adverse events (AE) were more frequent in the treated group (P = .02), but mild and without compliance issues. Only one severe advent event led to withdrawal in a patient who ingested twice the investigated treatment. Peanut-specific humoral immune responses were modulated.

CONCLUSION

The GIDOIT protocol demonstrated clinical and immunological efficacy and had an acceptable level of safety with weak oropharyngeal symptoms, no dysphagia, mild digestive events and few severe systemic AE.

Follow-up of patients with uncertain symptoms during an oral food challenge is useful for diagnosis

BACKGROUND

Uncertain symptoms often emerge during an oral food challenge (OFC), and Open-OFCs with those uncertain mild symptoms are ordinarily regarded as positive. Double-blind placebo-controlled food challenges should be conducted to determine these associations. Nevertheless, studies regarding the diagnosis of uncertain food allergy symptoms are lacking. We examined the diagnostic decision for a food allergy based on uncertain symptoms during an Open-OFC.

METHODS

We conducted an Open-OFC between August 2005 and April 2012 with 2271 cases who suspected as allergic to hen's eggs, cow's milk, or wheat. For the primary diagnosis, Open-OFCs with obvious symptoms were classified as "positive," no symptoms as "negative," and uncertain, indeterminate symptoms as "uncertain." We encouraged the children in the uncertain group to consume the causative foods at home more than twice; if any definitive symptoms were induced, children were classified as "intolerant," and children without any symptoms were classified as "tolerant," for the final diagnosis.

RESULTS

We analyzed 454 uncertain cases excluding 781 positive cases and 1036 negative cases. The symptoms that occurred for the uncertain cases included slight abdominal pain, localized skin rash, and an isolated cough. Of these cases, 362 (79.7%) were considered tolerant at the final diagnosis. Of the intolerant children at the final diagnosis, the induced symptoms at home were not serious.

CONCLUSIONS

Monitoring of recurring symptoms following consumption of causative foods at home by patients with uncertain symptoms improves the diagnostic accuracy of an Open-OFC.

Novel immunotherapy and treatment modality for severe food allergies

PURPOSE OF REVIEW

In recent years, many studies on oral immunotherapy (OIT) have been conducted; however, few have focused on severe food allergies. The purpose of this review was to assess the efficacy and safety of oral immunotherapies for patients with severe food allergy.

RECENT FINDINGS

We reviewed multiple immunotherapy reports published within a few years or reports focusing on severe food allergies. We also investigated recent studies on OIT and novel food allergy management.

SUMMARY

Immunotherapies targeting low-dose antigen exposure and oral food challenges using low-dose target volumes may be safer than conventional OIT. It is necessary to consider which immunotherapy regimen is appropriate based on allergy severity of the patient.

The Allergist's Role in Anaphylaxis and Food Allergy Management in the School and Childcare Setting

Anaphylaxis and food allergy management in childcare facilities and schools are growing challenges. An increasing number of children experience severe allergic reactions on school grounds as evidenced by reports of epinephrine use. Data also suggest that the prevalence of food allergy may be increasing, with a large percentage of school-aged children at risk for anaphylaxis. Moreover, anaphylaxis may occur for the first time in a previously undiagnosed child at school or childcare setting, suggesting that general preparedness is essential. Management includes strategies for minimizing the risk of reactions and allergen exposures as well as readiness to recognize and treat allergic reactions of any severity. The primary objective of this report is to offer health care providers an overview of relevant evidence, resources, and expert opinion to assist with developing interprofessional collaborative counsel on school food allergy management and anaphylaxis preparedness with families, schools, and childcare settings. We present the current evidence base, suggest resources, and highlight areas of current controversy that warrant further study.

Food Challenge and Community-Reported Reaction Profiles in Food-Allergic Children Aged 1 and 4 Years: A Population-Based Study

BACKGROUND

Oral food challenge is the main tool for diagnosing food allergy, but there is little data on the reaction profiles of young children undergoing challenges, nor how these reactions compare to reactions on accidental ingestion in the community.

OBJECTIVES

To compare reaction profiles from food challenges and parent-reported reactions on accidental ingestion, and assess predictors of severe reactions.

METHODS

HealthNuts is a longitudinal population-based cohort study of 5276 1-year-old infants. Infants underwent skin prick tests and those with identifiable wheals were offered food challenges. Food challenges were repeated at age 4 years in those with previous food allergy or reporting new food allergies. Community-reported reactions were ascertained from parent questionnaires.

RESULTS

Food challenges were undertaken in 916 children at age 1 year and 357 children at age 4 years (a total of 2047 peanut, egg, or sesame challenges). Urticaria was the most common sign in positive challenges at both ages (age 1 year, 88.7%, and age 4 years, 71.2%) although angioedema was significantly more common at age 4 years (40.1%) than at age 1 year (12.9%). Anaphylaxis was equally uncommon at both ages (2.1% and 2.8% of positive challenges at ages 1 and 4 years, respectively) but more common for peanut than for egg (4.5% and 1.2% of positive challenges at ages 1 and 4 years, respectively). The patterns of presenting signs reported during community reactions were similar to those observed in formal food challenges. Serum food-specific IgE levels of 15 kU/L or more were associated with moderate to severe reactions but skin prick test was not.

CONCLUSIONS

There was a shift from the most common presenting reaction of urticaria during food challenges toward more angioedema in older children. Serum food-specific IgE levels were associated with reaction severity.

Childcare and School Management Issues in Food Allergy

PURPOSE OF REVIEW

The goal of this review is to characterize food allergy management and anaphylaxis in schools and assess current policies and level of preparedness of schools to recognize and treat anaphylaxis.

RECENT FINDINGS

An increasing number of school-aged children have food allergies, and studies show that a significant number of school children with no known history of allergies will experience their first anaphylactic reaction at school. Stock-unassigned epinephrine auto-injectors are recommended in schools but not mandatory in most states, and therefore, epinephrine is not always available. Non-nursing staff members are sometimes administering epinephrine due to limitations in nurse staffing. Wide variations in staff training and lack of stock epinephrine leave many schools inadequately prepared to manage anaphylactic reactions. Emphasis should be placed not only on ensuring all schools have stock epinephrine but also on training a wider range of school staff members to minimize treatment delay with epinephrine and improve clinical outcomes.

Peanut oleosins associated with severe peanut allergy-importance of lipophilic allergens for comprehensive allergy diagnostics

BACKGROUND

Peanut allergy is one of the most common and most severe food allergies in Western countries and its accurate diagnosis to prevent potential life-threatening allergic reactions is crucial. However, aqueous extracts used for routine diagnostic measurements are devoid of lipophilic allergens such as oleosins. We have recently succeeded in the isolation and purification of these unique proteins, and the present study evaluates their allergenic potential and clinical relevance.

OBJECTIVE

We sought to assess allergenicity and sensitization prevalence of oleosins obtained from both raw and in-shell roasted peanuts. In addition, we tested the utilization of natural and recombinant oleosins for allergy diagnostic purposes.

METHODS

Oleosin sensitization, prevalence, and impact of thermal processing were analyzed by immunoblot with sera from 52 peanut-allergic individuals displaying different clinical phenotypes. The application of natural and recombinant oleosins for allergy diagnostics was investigated by basophil activation test (BAT). IgE-binding epitopes were identified by oligopeptide microarray.

RESULTS

Sensitization to oleosins was observed exclusively in peanut-allergic subjects suffering from severe systemic reactions. IgE-binding capacity of oleosins derived from in-shell roasted peanuts was increased as shown by immunoblot analysis and BAT. Both natural and recombinant molecules can be used to identify oleosin-sensitized patients by BAT. A linear epitope of Ara h 15 was determined that displays high similarity to other seed-derived oleosins.

CONCLUSIONS

Oleosins are clinically relevant peanut allergens and most likely associated with severe allergic symptoms. In-shell roasting increases their allergenicity, which is consistent with the observation that most allergic reactions are in connection with roasted peanuts.

Peanut protein extraction conditions strongly influence yield of allergens Ara h 1 and 2 and sensitivity of immunoassays

The clinical importance of peanut (Arachis hypogaea) allergies demands standardized allergen extraction protocols. We determined the effectiveness of common extraction conditions (20 buffers, defatting reagents, extraction time/temperatures, processing, extraction repeats) on crude protein and Ara h 1 and 2 yields. Despite similar 1D-gel profiles, defatting with n-hexane resulted in significantly higher yields of crude protein, Ara h 1, and Ara h 2 than with diethyl ether. The yields were affected by the composition and pH of the extraction buffers and other conditions, but crude protein yield did not always correlate with Ara h 1 and 2 yields. Denaturants, reducing agents, acidic buffers, and thermal processing of peanuts perturbed allergen quantification in ELISAs, probably via exposure of additional epitopes. Allergen detection in 2D-Western blots with PBS resulted in greater sensitivity than with TBS or Tris. We recommend that allergen extraction conditions be selected based on the research question being investigated.

Late reactions in food-allergic children and adolescents after double-blind, placebo-controlled food challenges

The time during which children are observed following a double-blind, placebo-controlled food challenge (DBPCFC) varies in clinical practice. There are little data on late reactions (LRs) following DBPCFCs. Therefore, we determined the prevalence, severity and clinical characteristics of late reactions in food-allergic children and adolescents after DBPCFC, and ascertained which factors are associated with, and may predict, LRs. Logistic regression analyses were performed to investigate which factors were associated with LRs and to develop the association and prediction models. A total of 1142 children underwent DBPCFCs (child-test combinations). Of these 1142 child-test combinations, 400 reported LRs following the DBPCFC. LRs in food-allergic children after DBPCFC are poorly predictable and are generally not severe. All LRs, including those on the placebo day, are more frequently reported in younger children. Children who do not experience severe immediate reactions may be safely discharged home 2 h after a DBPCFC.

Boiling and Frying Peanuts Decreases Soluble Peanut (Arachis Hypogaea) Allergens Ara h 1 and Ara h 2 But Does Not Generate Hypoallergenic Peanuts

Peanut allergy continues to be a problem in most developed countries of the world. We sought a processing method that would alter allergenic peanut proteins, such that allergen recognition by IgE from allergic individuals would be significantly reduced or eliminated. Such a method would render accidental exposures to trace amounts of peanuts safer. A combination of boiling and frying decreased recovery of Ara h 1 and Ara h 2 at their expected MWs. In contrast, treatment with high pressures under varying temperatures had no effect on protein extraction profiles. Antibodies specific for Ara h 1, Ara h 2, and Ara h 6 bound proteins extracted from raw samples but not in boiled/fried samples. However, pre-incubation of serum with boiled/fried extract removed most raw peanut-reactive IgE from solution, including IgE directed to Ara h 1 and 2. Thus, this method of processing is unlikely to generate a peanut product tolerated by peanut allergic patients. Importantly, variability in individual patients' IgE repertoires may mean that some patients' IgE would bind fewer polypeptides in the sequentially processed seed.

Special endpoint and product specific considerations in pharmaceutical acceptable daily exposure derivation

Recently, a guideline has been published by the European Medicines Agency (EMA) on setting safe limits, permitted daily exposures (PDE) [also called acceptable daily exposures (ADE)], for medicines manufactured in multi-product facilities. The ADE provides a safe exposure limit for inadvertent exposure of a drug due to cross-contamination in manufacturing. The ADE determination encompasses a standard risk assessment, requiring an understanding of the toxicological and pharmacological effects, the mechanism of action, drug compound class, and the dose-response as well as the pharmacokinetic properties of the compound. While the ADE concept has broad application in pharmaceutical safety there are also nuances and specific challenges associated with some toxicological endpoints or drug product categories. In this manuscript we discuss considerations for setting ADEs when the following specific adverse health endpoints may constitute the critical effect: genotoxicity, developmental and reproductive toxicity (DART), and immune system modulation (immunostimulation or immunosuppression), and for specific drug classes, including antibody drug conjugates (ADCs), emerging medicinal therapeutic compounds, and compounds with limited datasets. These are challenging toxicological scenarios that require a careful evaluation of all of the available information in order to establish a health-based safe level.

Risk multipliers for severe food anaphylaxis

Anaphylaxis is a severe, life threatening allergic reaction. In most fatal cases of food anaphylaxis, the fatality is not due merely to a simple, linear relationship between the allergen and exposure in a sensitized individual. Compounding factors such as the allergic disease burden—particularly the presence of asthma; comprehension of the potential severity of an event, training in the appropriate use of epinephrine, and emerging metabolic factors should be considered when assessing risk and establishing management strategies. This paper reviews the factors that contribute to the risk of severe anaphylactic events and provides a framework for the ongoing management of patients at risk of severe food allergy.

In vitro evaluation of digestive and endolysosomal enzymes to cleave CML-modified Ara h 1 peptides

Ara h 1 is a major peanut allergen. Processing-induced modifications may modulate the allergenic potency of Ara h 1. Carboxymethyl lysine (CML) modifications are a commonly described nonenzymatic modification on food proteins. In the current study, we tested the ability of digestive and endolysosomal proteases to cleave CML-modified and unmodified Ara h 1 peptides. Mass spectrometric analyses of the digested peptides demonstrate that carboxymethylation of lysine residues renders these peptides refractory to trypsin digestion. We did not detect observable differences in the simulated gastric fluid or endolysosomal digestion between the parental and CML-modified peptides. One of the tested peptides contains a lysine residue previously shown to be CML modified laying in a previously mapped linear IgE epitope, but we did not observe a difference in IgE binding between the modified and parental peptides. Our findings suggest a molecular mechanism for the increased resistance of peanut allergens modified by thermal processing, such as Ara h 1, to digestion in intestinal fluid after heating and could help explain how food processing-induced modifications may lead to more potent food allergens by acting to protect intact IgE epitopes from digestion by proteases targeting lysine residues.

Distinct parameters of the basophil activation test reflect the severity and threshold of allergic reactions to peanut

Background

The management of peanut allergy relies on allergen avoidance and epinephrine autoinjector for rescue treatment in patients at risk of anaphylaxis. Biomarkers of severity and threshold of allergic reactions to peanut could significantly improve the care for patients with peanut allergy.

Objective

We sought to assess the utility of the basophil activation test (BAT) to predict the severity and threshold of reactivity to peanut during oral food challenges (OFCs).

Methods

The severity of the allergic reaction and the threshold dose during OFCs to peanut were determined. Skin prick tests, measurements of specific IgE to peanut and its components, and BATs to peanut were performed on the day of the challenge.

Results

Of the 124 children submitted to OFCs to peanut, 52 (median age, 5 years) reacted with clinical symptoms that ranged from mild oral symptoms to anaphylaxis. Severe reactions occurred in 41% of cases, and 57% reacted to 0.1 g or less of peanut protein. The ratio of the percentage of CD63⁺ basophils after stimulation with peanut and after stimulation with anti-IgE (CD63 peanut/anti-IgE) was independently associated with severity (P = .001), whereas the basophil allergen threshold sensitivity CD-sens (1/EC₅₀ × 100, where EC₅₀ is half maximal effective concentration) value was independently associated with the threshold (P = .020) of allergic reactions to peanut during OFCs. Patients with CD63 peanut/anti-IgE levels of 1.3 or greater had an increased risk of severe reactions (relative risk, 3.4; 95% CI, 1.8-6.2). Patients with a CD-sens value of 84 or greater had an increased risk of reacting to 0.1 g or less of peanut protein (relative risk, 1.9; 95% CI, 1.3-2.8).

Conclusions

Basophil reactivity is associated with severity and basophil sensitivity is associated with the threshold of allergic reactions to peanut. CD63 peanut/anti-IgE and CD-sens values can be used to estimate the severity and threshold of allergic reactions during OFCs.

Smartphone instrument for portable enzyme-linked immunosorbent assays

We demonstrate the utilization of a smartphone camera as a spectrometer that is capable of measuring Enzyme Linked Immunosorbent Assays (ELISA) at biologically-relevant concentrations with the aid of a custom cradle that aligns a diffraction grating and a collimating lens between a light source and the imaging sensor. Two example biomarkers are assayed using conventional ELISA protocols: IL-6, a protein used diagnostically for several types of cancer, and Ara h 1, one of the principle peanut allergens. In addition to the demonstration of limits of detection at medically-relevant concentrations, a screening of various cookies was completed to measure levels of peanut cross-contamination in local bakeries. The results demonstrate the utility of the instrument for quantitatively performing broad classes of homogeneous colorimetric assays, in which the endpoint readout is the color change of a liquid sample.

Food allergy population thresholds: an evaluation of the number of oral food challenges and dosing schemes on the accuracy of threshold dose distribution modeling

For most allergenic foods, limited availability of threshold dose information within the population restricts the advice on action levels of unintended allergenic foods which should trigger advisory labeling on packaged foods. The objective of this paper is to provide guidance for selecting an optimal sample size for threshold dosing studies for major allergenic foods and to identify factors influencing the accuracy of estimation. A simulation study was performed to evaluate the effects of sample size and dosing schemes on the accuracy of the threshold distribution curve. The relationships between sample size, dosing scheme and the employed statistical distribution on the one hand and accuracy of estimation on the other hand were obtained. It showed that the largest relative gains in accuracy are obtained when sample size increases from N=20 to N=60. Moreover, it showed that the EuroPrevall dosing scheme is a useful start, but that it may need revision for a specific allergen as more data become available, because a proper allocation of the dosing steps is important. The results may guide risk assessors in minimum sample sizes for new studies and in the allocation of proper dosing schemes for allergens in provocation studies.