Digested Ara h 1 has sensitizing capacity in Brown Norway rats

Prophylactic Peanut Allergen Ara h 6 Sublingual Immunotherapy Drives Expansion of FoxP3 +Helios- Regulatory T Cells in the Absence of Allergen-Specific IgA

Insights into the underlying immunological mechanisms of prophylactic sublingual immunotherapy (SLIT) may support the development of new strategies for improved prevention and treatment of food allergy. Here, we investigated the humoral, regulatory and sublingual tissue immune response to prophylactic SLIT administration of a single purified peanut allergen in Brown Norway (BN) rats. BN rats received daily sublingual administration of peanut allergen Ara h 6 for three weeks. Suppression of sensitisation was evaluated by subsequent intraperitoneal administration of Ara h 6. Ara h 6-specific IgE, IgA, IgG1 and IgG2a-c levels were measured in serum. The frequency of regulatory T (Treg) cells was analysed using flow cytometry. The sublingual tissue response to Ara h 6 was analysed by transcriptional profiling using mRNA-sequencing. Ara h 6 SLIT protected rats from subsequent sensitisation without inducing a detectable humoral immune response (Ara h 6-specific IgE, IgA, IgG1 and IgG2a-c) in serum. SLIT furthermore promoted the relative expansion of induced Helios- Treg cells within the conventional CD4+CD25+FoxP3+ Treg population in sublingual draining lymph nodes and blood. In conclusion, prophylactic Ara h 6 SLIT drives the relative expansion of induced Helios- Treg cells in the absence of Ara h 6-specific IgA highlighting a potential novel IgA-independent Treg-related immune response at the sublingual mucosal site.

Exploration of digestion-resistant immunodominant epitopes in shrimp (Penaeus vannamei) allergens

The digestion products of Penaeus vannamei still had sensitizing and eliciting capacity; however, the underlying mechanism has not been identified. This study analyzed the structural changes of shrimp proteins during digestion, predicted the linearmimotopepeptides and first validated the allergenicity of immunodominantepitopes with binding ability. The results showed that the shrimp proteins were gradually degraded into small peptides during digestion, which might lead to the destruction of linear epitopes. However, these peptides carried IgE epitopes that still trigger allergic reactions. Eighteen digestion-resistant epitopes were predicted by multiple immunoinformatics tools and digestomics. Five epitopes contained more critical amino acids and had strong molecular docking (P1: DSGVGIYAPDAEA, P2: EGELKGTYYPLTGM, P3: GRQGDPHGKFDLPPGV, P4: IFAWPHKDNNGIE, P5: KSTESSVTVPDVPSIHD), and these epitopes were identified as novel IgE binding immunodominantepitopes in Penaeus vannamei. These findings provide novel insight into allergenic epitopes, which might serve as key targets for reducing the allergenicity in shrimp.

Allergenicity evaluation of quinoa proteins - A study in Brown Norway rats

The popularity of quinoa seeds has increased in the last decade due to their high nutritional value and natural gluten-free composition. Consumption of new proteins may pose a risk of introducing new allergies. In the present study the immunogenicity and sensitising capacity of quinoa proteins were assessed in a dose-response experiment in Brown Norway rats in comparison to proteins from spinach and peanut. Cross-reactivity between quinoa proteins and known allergens was evaluated by in silico analyses followed by analyses with 11 selected protein extracts and their anti-sera by means of ELISAs and immunoblotting. Further, an in vitro simulated gastro-duodenal digestion was performed. Quinoa proteins were found to have an inherent medium to high immunogenicity and sensitising capacity, being able to induce specific IgG1 and IgE levels higher than spinach but lower than peanut and elicit reactions of clinical relevance similar to peanut. Quinoa proteins were generally shown to resist digestion and retain capacity to bind quinoa-specific antibodies. Quinoa proteins were shown to be cross-reactive with peanut and tree nut allergens as high sequence homology and antibody cross-binding were demonstrated. Present study suggests that quinoa pose a medium to high level of allergenicity that should be further investigated in human studies.

Integrating Widely Targeted Lipidomics and Transcriptomics Unravels Aberrant Lipid Metabolism and Identifies Potential Biomarkers of Food Allergies in Rats

SCOPE

Oral food challenges (OFCs) are currently the gold standard for determining the clinical reactivity of food allergy (FA) but are time-consuming, expensive, and risky. To screen novel peripheral biomarkers of FA and characterize the aberrant lipid metabolism in serum, 24 rats are divided into four groups: peanut, milk, and shrimp allergy (PA, MA, and SA, respectively) and control groups, with six rats in each group, and used for widely targeted lipidomics and transcriptomics analysis.

METHODS AND RESULTS

Widely targeted lipidomics reveal 144, 162, and 206 differentially accumulated lipids in PA, MA, and SA groups, respectively. The study integrates widely targeted lipidomics and transcriptomics and identifies abnormal lipid metabolism correlated with widespread differential accumulation of diverse lipids (including triacylglycerol, diacylglycerol, sphingolipid, and glycerophospholipid) in PA, MA, and SA. Simplified random forest classifier is constructed through five repetitions of 10-fold cross-validation to distinguish allergy from control. A subset of 15 lipids as potential biomarkers allows for more reliable and more accurate prediction of FA. Independent replication validates the reproducibility of potential biomarkers.

CONCLUSION

The results reveal the major abnormalities in lipid metabolism and suggest the potential role of lipids as novel molecular signatures for FA.

Contribution of five major apple polyphenols in reducing peanut protein sensitization and alleviating allergencitiy of peanut by changing allergen structure

Peanuts are prone to trigger allergic reactions with high mortality rate. There is currently no effective way to prevent peanut allergy. In order to reduce the allergy risk of peanuts, it's significant to reduce sensitization of peanut prior to ingestion. In this study, the effects of five major apple polyphenols (epicatechin, phlorizin, rutin, chlorogenic acid, and catechin) -peanut protein on the sensitization of peanut allergens were studied by BALB/c peanut allergy model to access the contribution of each polyphenol in apple to peanut allergen sensitization reduction. Then, the mechanism was explored in terms of the effect of polyphenols on the simulated gastric digestion of peanut protein and the changes in structure of Ara h 1. The results showed that polyphenol binding could alleviate allergencitiy of peanut and regulate MAPK related signaling pathway. Among the five major apple polyphenols, epicatechin had the strongest inhibitory effect. The binding of epicatechin to the constitutive epitopes arginine led to changes in the spatial structure of Ara h 1, which resulted in the effective linear epitopes reduction. Modification of peanut allergens with polyphenols could effectively reduce the sensitization of peanut protein.

Dose and route of administration determine the efficacy of prophylactic immunotherapy for peanut allergy in a Brown Norway rat model

Introduction

Allergen-specific immunotherapy (IT) is emerging as a viable option for treatment of peanut allergy. Yet, prophylactic IT remains unexplored despite early introduction of peanut in infancy was shown to prevent allergy. There is a need to understand how allergens interact with the immune system depending on the route of administration, and how different dosages of allergen may protect from sensitisation and a clinical active allergy. Here we compared peanut allergen delivery via the oral, sublingual (SL), intragastric (IG) and subcutaneous (SC) routes for the prevention of peanut allergy in Brown Norway (BN) rats.

Methods

BN rats were administered PBS or three different doses of peanut protein extract (PPE) via either oral IT (OIT), SLIT, IGIT or SCIT followed by intraperitoneal (IP) injections of PPE to assess the protection from peanut sensitisation. The development of IgE and IgG1 responses to PPE and the major peanut allergens were evaluated by ELISAs. The clinical response to PPE was assessed by an ear swelling test (EST) and proliferation was assessed by stimulating splenocytes with PPE.

Results

Low and medium dose OIT (1 and 10 mg) and all doses of SCIT (1, 10, 100 µg) induced sensitisation to PPE, whereas high dose OIT (100 mg), SLIT (10, 100 or 1000 µg) or IGIT (1, 10 and 100 mg) did not. High dose OIT and SLIT as well as high and medium dose IGIT prevented sensitisation from the following IP injections of PPE and suppressed PPE-specific IgE levels in a dose-dependent manner. Hence, administration of peanut protein via different routes confers different risks for sensitisation and protection from peanut allergy development. Overall, the IgE levels toward the individual major peanut allergens followed the PPE-specific IgE levels.

Discussion

Collectively, this study showed that the preventive effect of allergen-specific IT is determined by the interplay between the specific site of PPE delivery for presentation to the immune system, and the allergen quantity, and that targeting and modulating tolerance mechanisms at specific mucosal sites may be a prophylactic strategy for prevention of peanut allergy.

Amoxicillin does not affect the development of cow’s milk allergy in a Brown Norway rat model

The use of antibiotics as well as changes in the gut microbiota have been linked to development of food allergy in childhood. It remains unknown whether administration of a single clinically relevant antibiotic directly promotes food allergy development when administrated during the sensitisation phase in an experimental animal model. We investigated whether the antibiotic amoxicillin affected gut microbiota composition, development of cow's milk allergy (CMA) and frequencies of allergic effector cells and regulatory T cells in the intestine. Brown Norway rats were given daily oral gavages of amoxicillin for six weeks and whey protein concentrate (WPC) with or without cholera toxin three times per week for the last five weeks. Microbiota composition in faeces and small intestine was analysed by 16S rRNA sequencing. The development of CMA was assessed by WPC‐specific IgE in serum, ear swelling response to WPC and body hypothermia following oral gavage of WPC. Allergic effector cells were analysed by histology, and frequencies of regulatory and activated T cells were analysed by flow cytometry. Amoxicillin administration reduced faecal microbiota diversity, reduced the relative abundance of Firmicutes and increased the abundance of Bacteroidetes and Proteobacteria. Despite these effects, amoxicillin did not affect the development of CMA, nor the frequencies of allergic effector cells or regulatory T cells. Thus, amoxicillin does not carry a direct risk for food allergy development when administrated in an experimental model of allergic sensitisation to WPC via the gut. This finding suggests that confounding factors may better explain the epidemiological link between antibiotic use and food allergy.

EFSA Panel on Genetically Modified Organisms (GMO), Mullins E, Bresson J, Dalmay T, Dewhurst IC, Epstein MM, George Firbank L, Guerche P, Hejatko J, Naegeli H, Nogué F, Rostoks N, Sánchez Serrano JJ, Savoini G, Veromann E, Veronesi F, Fernandez Dumont A, Moreno FJ. Scientific Opinion on development needs for the allergenicity and protein safety assessment of food and feed products derived from biotechnology

This Scientific Opinion addresses the formulation of specific development needs, including research requirements for allergenicity assessment and protein safety, in general, which is urgently needed in a world that demands more sustainable food systems. Current allergenicity risk assessment strategies are based on the principles and guidelines of the Codex Alimentarius for the safety assessment of foods derived from 'modern' biotechnology initially published in 2003. The core approach for the safety assessment is based on a 'weight-of-evidence' approach because no single piece of information or experimental method provides sufficient evidence to predict allergenicity. Although the Codex Alimentarius and EFSA guidance documents successfully addressed allergenicity assessments of single/stacked event GM applications, experience gained and new developments in the field call for a modernisation of some key elements of the risk assessment. These should include the consideration of clinical relevance, route of exposure and potential threshold values of food allergens, the update of in silico tools used with more targeted databases and better integration and standardisation of test materials and in vitro/in vivo protocols. Furthermore, more complex future products will likely challenge the overall practical implementation of current guidelines, which were mainly targeted to assess a few newly expressed proteins. Therefore, it is timely to review and clarify the main purpose of the allergenicity risk assessment and the vital role it plays in protecting consumers' health. A roadmap to (re)define the allergenicity safety objectives and risk assessment needs will be required to inform a series of key questions for risk assessors and risk managers such as 'what is the purpose of the allergenicity risk assessment?' or 'what level of confidence is necessary for the predictions?'.

Preparation and in vitro bioactive evaluation of cashew-nut proteins hydrolysate as a potential source of anti-allergy peptides

This work proposes a novel potential source of antiallergens based on bioactive peptides. Cashew-nut protein hydrolysate with antiallergic activity was prepared from cashew nuts through protease treatment. The change in the antiallergic activity of cashew-nut protein hydrolysate during in vitro simulated digestion was investigated. Cashew-nut protein hydrolysates were prepared through treatment using five different enzymes, namely, Alcalase, Protamex, Neutrase, papain, and bromelin. According to the results of molecular weight distribution, more small molecular weight peptides could be obtained by selecting Alcalase protease than other proteases, and the degree of hydrolysis, trichloroacetic acid-soluble peptide yield and hyaluronidase inhibitory rate of the hydrolysate were 17.0 ± 61.52%, 26.28 ± 0.13% and 62.06% ± 5.07%, which were significantly higher than those of other proteases. Therefore, Alcalase is the most suitable protease for the preparation of cashew-nut hydrolysates. Cashew-nut protein hydrolysates prepared with Alcalase under optimum conditions were fractionated through ultrafiltration. Fractions with low molecular weight exhibited the highest hyaluronidase inhibitory rate (90.57%) among all fractions. The inhibition of hyaluronidase activity during digestion showed that cashew-nut protein hydrolysate III (CPH III) has persistent antiallergic activity. Therefore, CPH III could serve as a potential source of functional peptides with health-promoting effects.

Partially Hydrolysed Whey Has Superior Allergy Preventive Capacity Compared to Intact Whey Regardless of Amoxicillin Administration in Brown Norway Rats

Background

It remains largely unknown how physicochemical properties of hydrolysed infant formulas influence their allergy preventive capacity, and results from clinical and animal studies comparing the preventive capacity of hydrolysed infant formula with conventional infant formula are inconclusive. Thus, the use of hydrolysed infant formula for allergy prevention in atopy-prone infants is highly debated. Furthermore, knowledge on how gut microbiota influences allergy prevention remains scarce.

Objective

To gain knowledge on (1) how physicochemical properties of hydrolysed whey products influence the allergy preventive capacity, (2) whether host microbiota disturbance influences allergy prevention, and (3) to what extent hydrolysed whey products influence gut microbiota composition.

Methods

The preventive capacity of four different ad libitum administered whey products was investigated in Brown Norway rats with either a conventional or an amoxicillin-disturbed gut microbiota. The preventive capacity of products was evaluated as the capacity to reduce whey-specific sensitisation and allergic reactions to intact whey after intraperitoneal post-immunisations with intact whey. Additionally, the direct effect of the whey products on the growth of gut bacteria derived from healthy human infant donors was evaluated by in vitro incubation.

Results

Two partially hydrolysed whey products with different physicochemical characteristics were found to be superior in preventing whey-specific sensitisation compared to intact and extensively hydrolysed whey products. Daily oral amoxicillin administration, initiated one week prior to intervention with whey products, disturbed the gut microbiota but did not impair the prevention of whey-specific sensitisation. The in vitro incubation of infant faecal samples with whey products indicated that partially hydrolysed whey products might confer a selective advantage to enterococci.

Conclusions

Our results support the use of partially hydrolysed whey products for prevention of cow’s milk allergy in atopy-predisposed infants regardless of their microbiota status. However, possible direct effects of partially hydrolysed whey products on gut microbiota composition warrants further investigation.

Quinoa (Chenopodium quinoa Willd.) Seeds Increase Intestinal Protein Uptake

SCOPE

Within the last decade, quinoa seeds have gained much popularity as a new food and have recently been proposed as an appropriate food for early introduction in infants. Quinoa contains high levels of saponins, which are known for their adjuvant activity and effect on the intestinal barrier function. The aim of this study is to investigate the impact of quinoa on intestinal permeability and inflammation in comparison with the positive controls; cholera toxin (CT), and capsaicin.

METHODS AND RESULTS

The effect of quinoa on intestinal barrier function and inflammation is investigated in vitro using a Caco-2 cell line and in vivo using a Brown Norway rat model. Effects in vivo are analyzed by protein uptake, histology, gene expression, antibody levels, and flow cytometry. Quinoa and the positive controls all increased the intestinal permeability, but distinct patterns of absorbed protein are observed in the epithelium, Peyer's patches, lamina propria, and serum. The quinoa-mediated effect on intestinal barrier function is found to be distinct from the effect of the two positive controls.

CONCLUSION

The findings demonstrate the ability of quinoa to increase intestinal permeability and to promote compartment-specific protein uptake via mechanisms that may differ from CT and capsaicin.

Digestion and Transport across the Intestinal Epithelium Affects the Allergenicity of Ara h 1 and 3 but Not of Ara h 2 and 6

Scope

No accepted and validated methods are currently available which can accurately predict protein allergenicity. In this study, the role of digestion and transport on protein allergenicity is investigated.

Methods and results

Peanut allergens (Ara h 1, 2, 3, and 6) and a milk allergen (β‐lactoglobulin) are transported across pig intestinal epithelium using the InTESTine model and afterward basophil activation is measured to assess the (remaining) functional properties. Additionally, allergens are digested by pepsin prior to epithelial transport and their allergenicity is assessed in a human mast cell activation assay. Remarkably, transported Ara h 1 and 3 are not able to activate basophils, in contrast to Ara h 2 and 6. Digestion prior to transport results in a significant increase in mast cell activation of Ara h 1 and 3 dependent on the length of digestion time. Activation of mast cells by Ara h 2 and 6 is unaffected by digestion prior to transport.

Conclusions

Digestion and transport influences the allergenicity of Ara h 1 and 3, but not of Ara h 2 and 6. The influence of digestion and transport on protein allergenicity may explain why current in vitro assays are not predictive for allergenicity.

EFSA Panel on Genetically Modified Organisms (GMO), Naegeli H, Bresson J, Dalmay T, Dewhurst IC, Epstein MM, Firbank LG, Guerche P, Hejatko J, Moreno FJ, Mullins E, Nogué F, Rostoks N, Sánchez Serrano JJ, Savoini G, Veromann E, Veronesi F, Dumont AF. Statement on in vitro protein digestibility tests in allergenicity and protein safety assessment of genetically modified plants

This statement supplements and updates the GMO Panel guidance document on allergenicity of genetically modified (GM) plants published in 2017. In that guidance document, the GMO Panel considered that additional investigations on in vitro protein digestibility were needed before providing any additional recommendations in the form of guidance to applicants. Thus, an interim phase was proposed to assess the utility of an enhanced in vitro digestion test, as compared to the classical pepsin resistance test. Historically, resistance to degradation by pepsin using the classical pepsin resistance test has been considered as additional information, in a weight-of-evidence approach, for the assessment of allergenicity and toxicity of newly expressed proteins in GM plants. However, more recent evidence does not support this test as a good predictor of allergenic potential for hazard. Furthermore, there is a need for more reliable systems to predict the fate of the proteins in the gastrointestinal tract and how they interact with the relevant human cells. Nevertheless, the classical pepsin resistance test can still provide some information on the physicochemical properties of novel proteins relating to their stability under acidic conditions. But other methods can be used to obtain data on protein's structural and/or functional integrity. It is acknowledged that the classical pepsin resistance test is embedded into international guidelines, e.g. Codex Alimentarius and Regulation (EU) No 503/2013. For future development, a deeper understanding of protein digestion in the gastrointestinal tract could enable the framing of more robust strategies for the safety assessment of proteins. Given the high complexity of the digestion and absorption process of dietary proteins, it is needed to clarify and identify the aspects that could be relevant to assess potential risks of allergenicity and toxicity of proteins. To this end, a series of research questions to be addressed are also formulated in this statement.

Digestomics of Cow's Milk: Short Digestion-Resistant Peptides of Casein Form Functional Complexes by Aggregation

The aim of this study was to identify short digestion-resistant peptides (SDRPs) released by pepsin digestion of the whole cow’s milk and examine their IgE reactivity and allergenicity. Raw milk was subjected to simulated gastric digestion. SDRPs were fractionated from the digests and identified by MS. Milk SDRPs were evaluated for aggregability, propensity to compete for IgE binding with individual milk allergens, and ability to bind IgG4 from allergic and milk-tolerant individuals. The majority of milk SDRPs originated from caseins (97% of peptides) and overlapped with the known IgE epitopes of cow’s milk allergens. SDRPs competed with milk proteins for binding to human IgE and readily formed aggregates. The average peptide length was 10.6 ± 3.5 amino acids. The ability to provoke allergenic in vivo responses was confirmed by skin-prick testing (SPT) in five milk-allergic subjects. This was attributed to the peptide ability to aggregate into non-covalent complexes. SDRPs are able to induce response in SPT, but only in 50% of the sera SDRPs were able to inhibit IgG4 binding to caseins. Hence, SDRPs corresponding to the mainly continuous epitopes of milk proteins induce allergenic in vivo responses in milk-allergic subjects due to aggregation.

Gluten tolerance prevents oral sensitization with enzymatic or acid hydrolyzed gluten: A study in Brown Norway rats

Background

There are several reports describing allergy to hydrolyzed wheat products. After a large outbreak in Japan it was established that sensitization was caused by skin contact with acid hydrolyzed gluten in soap. It is still not clear if other forms of hydrolyzed gluten may sensitize, and if the skin is the only relevant route of sensitization in humans and to what extent oral tolerance to wheat play a role.

Objectives

The aim of the present study was to examine if wheat-tolerant rats may be sensitized via the oral or i.p. route when exposed to gluten, enzymatic or acid hydrolyzed gluten.

Methods

Brown Norway rats, tolerant to wheat, were dosed by three i.p. injections without adjuvant or by oral gavage daily for 35 days with the three gluten products, respectively. Sera were analyzed by ELISA for specific IgG1 and IgE. In addition inhibition and avidity ELISAs were performed. Results were compared to a similar study in rats naïve to wheat.

Results

More than half the animals had measurable IgG1 at the start of the dosing period. I.p. immunization resulted in significant specific IgG1 and IgE to the antigen used for immunization but significantly lower than in naïve rats. The results of inhibition and avidity ELISA’s indicate that the underlying tolerance to epitopes common to the three products influences the immune response. Oral dosing did not induce significant changes in response to either gluten or the hydrolyzed gluten product used for dosing.

Conclusions

The study shows that i.p. immunization with the three products can break the underlying tolerance to wheat. Exposure by the oral route to enzymatic or acid hydrolyzed gluten is very unlikely to break an already established tolerance to gluten and induce sensitization.

Short-Term Amoxicillin-Induced Perturbation of the Gut Microbiota Promotes Acute Intestinal Immune Regulation in Brown Norway Rats

The intestinal gut microbiota is essential for maintaining host health. Concerns have been raised about the possible connection between antibiotic use, causing microbiota disturbances, and the increase in allergic and autoimmune diseases observed during the last decades. To elucidate the putative connection between antibiotic use and immune regulation, we have assessed the effects of the antibiotic amoxicillin on immune regulation, protein uptake, and bacterial community structure in a Brown Norway rat model. Daily intra-gastric administration of amoxicillin resulted in an immediate and dramatic shift in fecal microbiota, characterized by a reduction of within sample (α) diversity, reduced variation between animals (β diversity), increased relative abundance of Bacteroidetes and Gammaproteobacteria, with concurrent reduction of Firmicutes, compared to a water control group. In the small intestine, amoxicillin also affected microbiota composition significantly, but in a different way than observed in feces. The small intestine of control animals was vastly dominated by Lactobacillus, but this genus was much less abundant in the amoxicillin group. Instead, multiple different genera expanded after amoxicillin administration, with high variation between individual animals, thus the small intestinal α and β diversity were higher in the amoxicillin group compared to controls. After 1 week of daily amoxicillin administration, total fecal IgA level, relative abundance of small intestinal regulatory T cells and goblet cell numbers were higher in the amoxicillin group compared to controls. Several bacterial genera, including Escherichia/Shigella, Klebsiella (Gammaproteobacteria), and Bifidobacterium, for which the relative abundance was higher in the small intestine in the amoxicillin group than in controls, were positively correlated with the fraction of small intestinal regulatory T cells. Despite of epidemiologic studies showing an association between early life antibiotic consumption and later prevalence of inflammatory bowel diseases and food allergies, our findings surprisingly indicated that amoxicillin-induced perturbation of the gut microbiota promotes acute immune regulation. We speculate that the observed increase in relative abundance of small intestinal regulatory T cells is partly mediated by immunomodulatory lipopolysaccharides derived from outgrowth of Gammaproteobacteria.

Overview of in vivo and ex vivo endpoints in murine food allergy models: Suitable for evaluation of the sensitizing capacity of novel proteins?

Significant efforts are necessary to introduce new dietary protein sources to feed a growing world population while maintaining food supply chain sustainability. Such a sustainable protein transition includes the use of highly modified proteins from side streams or the introduction of new protein sources that may lead to increased clinically relevant allergic sensitization. With food allergy being a major health problem of increasing concern, understanding the potential allergenicity of new or modified proteins is crucial to ensure public health protection. The best predictive risk assessment methods currently relied on are in vivo models, making the choice of endpoint parameters a key element in evaluating the sensitizing capacity of novel proteins. Here, we provide a comprehensive overview of the most frequently used in vivo and ex vivo endpoints in murine food allergy models, addressing their strengths and limitations for assessing sensitization risks. For optimal laboratory‐to‐laboratory reproducibility and reliable use of predictive tests for protein risk assessment, it is important that researchers maintain and apply the same relevant parameters and procedures. Thus, there is an urgent need for a consensus on key food allergy parameters to be applied in future food allergy research in synergy between both knowledge institutes and clinicians.

The relevance of a digestibility evaluation in the allergenicity risk assessment of novel proteins. Opinion of a joint initiative of COST action ImpARAS and COST action INFOGEST

The current allergenicity assessment of novel proteins is based on the EFSA GMO guidance. Recently, EFSA launched a new guidance document on allergenicity assessment of GM plants (2017). This document describes, amongst other topics, the new scientific and regulatory developments on in vitro protein digestibility tests. The EFSA GMO Panel stated that for in vitro protein digestibility tests, additional investigations are needed before any additional recommendation in the form of guidance can be provided. To this end, an interim phase is considered necessary to evaluate the revisions to the in vitro gastrointestinal digestion test, proposed by EFSA. This prompted the establishment of a joint workshop through two COST Action networks: COST Action ImpARAS and COST Acton INFOGEST. In 2017, a workshop was organised to discuss the relevance of digestion in allergenicity risk assessment and how to potentially improve the current methods and readouts. The outcome of the workshop is that there is no rationale for a clear readout that is predictive for allergenicity and we suggest to omit the digestion test from the allergenicity assessment strategy for now, and put an effort into filling the knowledge gaps as summarized in this paper first.

Analysis of the Allergenic Epitopes of Tropomyosin from Mud Crab Using Phage Display and Site-Directed Mutagenesis

Mud crab ( Scylla serrata), which is widely consumed, can cause severe allergic symptoms. Eight linear epitopes and seven conformational epitopes of tropomyosin (TM) from S. serrata were identified using phage display. The conformational epitopes were formed based on the coiled-coil structure of TM. Most of the epitopes were located in the regions where primary structures were conserved among crustacean TM. Twelve synthetic peptides were designed according to the epitopes and trypsin-cutting sites of TM, among them, three synthetic peptides (including one linear epitope and two conformational epitopes) were recognized by all of the patient sera using inhibitory dot blotting. A triple-variant (R90A-E164A-Y267A) was constructed based on the critical amino acids of the TM epitope. The IgE-binding activity of the triple-variant was significantly reduced compared with that of native TM. The results of phage display and site-directed mutagenesis offered new information regarding conformational epitopes of TM.

Immunomodulating peptides for food allergy prevention and treatment

Among the most promising strategies currently assayed against IgE-mediated allergic diseases stands the possibility of using immunomodulating peptides to induce oral tolerance toward offending food allergens or even to prevent allergic sensitization. This review focuses on the beneficial effects of food derived immunomodulating peptides on food allergy, which can be directly exerted in the intestinal tract or once being absorbed through the intestinal epithelial barrier to interact with immune cells. Food peptides influence intestinal homeostasis by maintaining and reinforcing barrier function or affecting intestinal cell-signalling to nearby immune cells and mucus secretion. In addition, they can stimulate cells of the innate and adaptive immune system while supressing inflammatory responses. Peptides represent an attractive alternative to whole allergens to enhance the safety and efficacy of immunotherapy treatments. The conclusions drawn from curative and preventive experiments in murine models are promising, although there is a need for more pre-clinical studies to further explore the immunomodulating strategy and its mechanisms and for a deeper knowledge of the peptide sequence and structural requirements that determine the immunoregulatory function.

Gastrointestinal digestion of hazelnut allergens on molecular level: Elucidation of degradation kinetics and resistant immunoactive peptides using mass spectrometry

SCOPE

Allergy to hazelnut seeds ranks among the most prevalent food allergies in Europe. The aim of this study was to elucidate the gastrointestinal digestion of hazelnut allergens on molecular level.

METHODS AND RESULTS

Hazelnut flour was digested in vitro following the Infogest consensus model. For six allergenic proteins, the time-dependent course of digestion was monitored by SDS-PAGE and HPLC-MS/MS, and degradation products were characterized by a bottom-up proteomics approach. Depending on the molecular structure, a specific biochemical fate was observed for each allergen, and degradation kinetics were traced back to the peptide level. 1183 peptides were characterized, including 130 peptides that carry known IgE-binding epitopes and may represent sensitizers for hazelnut allergy. The kinetics of peptide formation and degradation were determined by label-free quantification and follow a complex multi-stage mechanism.

CONCLUSION

We present a comprehensive survey on the gastrointestinal digestion of a relevant allergenic food on level of the peptidome, including the first systematic characterization and quantification of degradation products. This provides information on the differential resistance of plant food allergens and their structural elements undergoing digestion and forms the basis for a deeper understanding of the molecular principles responsible for sensitization to food allergy.

Application of phage peptide display technology for the study of food allergen epitopes

Phage peptide display technology has been used to identify IgE-binding mimotopes (mimics of natural epitopes) that mimic conformational epitopes. This approach is effective in the characterization of those epitopes that are important for eliciting IgE-mediated allergic responses by food allergens and those that are responsible for cross-reactivity among allergenic food proteins. Application of this technology will increase our understanding of the mechanisms whereby food allergens elicit allergic reactions, will facilitate the discovery of diagnostic reagents and may lead to mimotope-based immunotherapy.

Food Allergens: Is There a Correlation between Stability to Digestion and Allergenicity?

Food allergy is a major health problem in the Western countries, affecting 3-8% of the population. It has not yet been established what makes a dietary protein a food allergen. Several characteristics have been proposed to be shared by food allergens. One of these is resistance to digestion. This paper reviews data from digestibility studies on purified food allergens and evaluates the predictive value of digestibility tests on the allergenic potential. We point out that food allergens do not necessarily resist digestion. We discuss how the choice of in vitro digestibility assay condition and the method used for detection of residual intact protein as well as fragments hereof may greatly influence the outcome as well as the interpretation of results. The finding that digests from food allergens may retain allergenicity, stresses the importance of using immunological assays for evaluating the allergenic potential of food allergen digestion products. Studies assessing the allergenicity of digestion products, by either IgE-binding, elicitation or sensitizing capacity, shows that digestion may abolish, decrease, have no effect, or even increase the allergenicity of food allergens. Therefore, the predictive value of the pepsin resistance test for assessing the allergenic potential of novel proteins can be questioned.

Phage display peptide libraries in molecular allergology: from epitope mapping to mimotope-based immunotherapy

Identification of allergen epitopes is a key component in proper understanding of the pathogenesis of type I allergies, for understanding cross-reactivity and for the development of mimotope immunotherapeutics. Phage particles have garnered recognition in the field of molecular allergology due to their value not only in competitive immunoscreening of peptide libraries but also as immunogenic carriers of allergen mimotopes. They integrate epitope discovery technology and immunization functions into a single platform. This article provides an overview of allergen mimotopes identified through the phage display technique. We discuss the contribution of phage display peptide libraries in determining dominant B-cell epitopes of allergens, in developing mimotope immunotherapy, in understanding cross-reactivity, and in determining IgE epitope profiles of individual patients to improve diagnostics and individualize immunotherapy. We also discuss the advantages and pitfalls of the methodology used to identify and validate the mimotopes.

Current challenges facing the assessment of the allergenic capacity of food allergens in animal models

Food allergy is a major health problem of increasing concern. The insufficiency of protein sources for human nutrition in a world with a growing population is also a significant problem. The introduction of new protein sources into the diet, such as newly developed innovative foods or foods produced using new technologies and production processes, insects, algae, duckweed, or agricultural products from third countries, creates the opportunity for development of new food allergies, and this in turn has driven the need to develop test methods capable of characterizing the allergenic potential of novel food proteins. There is no doubt that robust and reliable animal models for the identification and characterization of food allergens would be valuable tools for safety assessment. However, although various animal models have been proposed for this purpose, to date, none have been formally validated as predictive and none are currently suitable to test the allergenic potential of new foods. Here, the design of various animal models are reviewed, including among others considerations of species and strain, diet, route of administration, dose and formulation of the test protein, relevant controls and endpoints measured.

Stability and immunogenicity of hypoallergenic peanut protein-polyphenol complexes during in vitro pepsin digestion

Allergenic peanut proteins are relatively resistant to digestion, and if digested, metabolized peptides tend to remain large and immunoreactive, triggering allergic reactions in sensitive individuals. In this study, the stability of hypoallergenic peanut protein-polyphenol complexes was evaluated during simulated in vitro gastric digestion. When digested with pepsin, the basic subunit of the peanut allergen Ara h 3 was more rapidly hydrolyzed in peanut protein-cranberry or green tea polyphenol complexes compared to uncomplexed peanut flour. Ara h 2 was also hydrolyzed more quickly in the peanut protein-cranberry polyphenol complex than in uncomplexed peanut flour. Peptides from peanut protein-cranberry polyphenol complexes and peanut protein-green tea polyphenol complexes were substantially less immunoreactive (based on their capacity to bind to peanut-specific IgE from patient plasma) compared to peptides from uncomplexed peanut flour. These results suggest that peanut protein-polyphenol complexes may be less immunoreactive passing through the digestive tract in vivo, contributing to their attenuated allergenicity.

Characterization of the Immunogenicity and Allergenicity of Two Cow's Milk Hydrolysates--A Study in Brown Norway Rats

Hypoallergenic infant formulas based on hydrolysed milk proteins are used in the diet for cow's milk allergic infants. For a preclinical evaluation of the immunogenicity and allergenicity of new protein ingredients for such hypoallergenic infant formulas as well as for the investigation of which characteristics of hydrolysates that contribute to allergenicity, in vivo models are valuable tools. In this study, we examine the immunogenicity and allergenicity of two hydrolysates in a Brown Norway (BN) rat model, using i.p. dosing, which allows for the use of small quantities. Intact BLG, hydrolysed BLG and a hydrolysed whey product suitable for use in extensively hydrolysed formulas were thoroughly characterized for protein chemical features and administered to BN rats by i.p. immunization with or without adjuvant. Sera were analysed for specific IgG and IgE for evaluation of sensitizing capacity, immunogenicity and antibody-binding capacity. For evaluation of eliciting capacity a skin test was performed. The study showed that the hydrolysates had no residual allergenicity, lacking the capacity to sensitize and elicit reactions in the BN rats. Dosing with or without adjuvant induced a large difference in immunogenicity. Only antibodies from rats sensitized to intact BLG with adjuvant were able to bind the hydrolysates, and the whey-based hydrolysate only showed immunogenicity when dosed with adjuvant. This study showed that hydrolysates can be evaluated by an i.p. animal model, but that the choice of in vitro tests used for evaluation of antibody responses may greatly influence the result as well as may the use of adjuvant.

Development and characterization of an effective food allergy model in Brown Norway rats

BACKGROUND

Food allergy (FA) is an adverse health effect produced by the exposure to a given food. Currently, there is no optimal animal model of FA for the screening of immunotherapies or for testing the allergenicity of new foods.

OBJECTIVE

The aim of the present study was to develop an effective and rapid model of FA in Brown Norway rats. In order to establish biomarkers of FA in rat, we compared the immune response and the anaphylactic shock obtained in this model with those achieved with only intraperitoneal immunization.

METHODS

Rats received an intraperitoneal injection of ovalbumin (OVA) with alum and toxin from Bordetella pertussis, and 14 days later, OVA by oral route daily for three weeks (FA group). A group of rats receiving only the i.p. injection (IP group) were also tested. Serum anti-OVA IgE, IgG1, IgG2a, IgG2b and IgA antibodies were quantified throughout the study. After an oral challenge, body temperature, intestinal permeability, motor activity, and mast cell protease II (RMCP-II) levels were determined. At the end of the study, anti-OVA intestinal IgA, spleen cytokine production, lymphocyte composition of Peyer's patches and mesenteric lymph nodes, and gene expression in the small intestine were quantified.

RESULTS

Serum OVA-specific IgG1, IgG2a and IgG2b concentrations rose with the i.p. immunization but were highly augmented after the oral OVA administration. Anti-OVA IgE increased twofold during the first week of oral OVA gavage. The anaphylaxis in both IP and FA groups decreased body temperature and motor activity, whereas intestinal permeability increased. Interestingly, the FA group showed a much higher RMCP II serum protein and intestinal mRNA expression.

CONCLUSIONS

These results show both an effective and relatively rapid model of FA assessed by means of specific antibody titres and the high production of RMCP-II and its intestinal gene expression.

Allergenicity of peanut component Ara h 2: Contribution of conformational versus linear hydroxyproline-containing epitopes

BACKGROUND

The 2S-albumin Ara h 2 is the most potent peanut allergen and a good predictor of clinical reactivity in allergic children. Posttranslational hydroxylation of proline residues occurs in DPYSP(OH)S motifs, which are repeated 2 or 3 times in different isoforms.

OBJECTIVES

We investigated the effect of proline hydroxylation on IgE binding and the relative contributions of linear and conformational epitopes to Ara h 2 allergenicity.

METHODS

Peptides containing DPYSP(OH)S motifs were synthesized. A recombinant variant of Ara h 2 without DPYSP(OH)S motifs was generated by means of deletion mutagenesis. IgE reactivity of 18 French and 5 American patients with peanut allergy toward synthetic peptides and recombinant allergens was assessed by using IgE-binding inhibition assays and degranulation tests of humanized rat basophilic leukemia cells.

RESULTS

Hydroxyproline-containing peptides exhibited an IgE-binding activity equivalent to that of the unfolded Ara h 2. In contrast, corresponding peptides without hydroxyprolines displayed a very weak IgE-binding capacity. Despite removal of the DPYSP(OH)S motifs, the deletion variant still displayed Ara h 2 conformational epitopes. The IgE-binding capacity of Ara h 2 was then recapitulated with an equimolar mixture of a hydroxylated peptide and the deletion variant. Hydroxylated peptides of 15 and 27 amino acid residues were also able to trigger cell degranulation.

CONCLUSIONS

Sensitization toward linear and conformational epitopes of Ara h 2 is variable among patients with peanut allergy. Optimal IgE binding to linear epitopes of Ara h 2 requires posttranslational hydroxylation of proline residues. The absence of hydroxyprolines could then affect the accuracy of component-resolved diagnostics by using rAra h 2.

Assessment of the sensitizing potential of processed peanut proteins in Brown Norway rats: roasting does not enhance allergenicity

Background

IgE-binding of process-modified foods or proteins is the most common method for examination of how food processing affects allergenicity of food allergens. How processing affects sensitization capacity is generally studied by administration of purified food proteins or food extracts and not allergens present in their natural food matrix.

Objectives

The aim was to investigate if thermal processing increases sensitization potential of whole peanuts via the oral route. In parallel, the effect of heating on sensitization potential of the major peanut allergen Ara h 1 was assessed via the intraperitoneal route.

Methods

Sensitization potential of processed peanut products and Ara h 1 was examined in Brown Norway (BN) rats by oral administration of blanched or oil-roasted peanuts or peanut butter or by intraperitoneal immunization of purified native (N-), heated (H-) or heat glycated (G-)Ara h 1. Levels of specific IgG and IgE were determined by ELISA and IgE functionality was examined by rat basophilic leukemia (RBL) cell assay.

Results

In rats dosed orally, roasted peanuts induced significant higher levels of specific IgE to NAra h 1 and 2 than blanched peanuts or peanut butter but with the lowest level of RBL degranulation. However, extract from roasted peanuts was found to be a superior elicitor of RBL degranulation. Process-modified Ara h 1 had similar sensitizing capacity as NAra h 1 but specific IgE reacted more readily with process-modified Ara h 1 than with native.

Conclusions

Peanut products induce functional specific IgE when dosed orally to BN rats. Roasted peanuts do not have a higher sensitizing capacity than blanched peanuts. In spite of this, extract from roasted peanuts is a superior elicitor of RBL cell degranulation irrespectively of the peanut product used for sensitization. The results also suggest that new epitopes are formed or disclosed by heating Ara h 1 without glucose.

Allergic sensitization: screening methods

Experimental in silico, in vitro, and rodent models for screening and predicting protein sensitizing potential are discussed, including whether there is evidence of new sensitizations and allergies since the introduction of genetically modified crops in 1996, the importance of linear versus conformational epitopes, and protein families that become allergens. Some common challenges for predicting protein sensitization are addressed: (a) exposure routes; (b) frequency and dose of exposure; (c) dose-response relationships; (d) role of digestion, food processing, and the food matrix; (e) role of infection; (f) role of the gut microbiota; (g) influence of the structure and physicochemical properties of the protein; and (h) the genetic background and physiology of consumers. The consensus view is that sensitization screening models are not yet validated to definitively predict the de novo sensitizing potential of a novel protein. However, they would be extremely useful in the discovery and research phases of understanding the mechanisms of food allergy development, and may prove fruitful to provide information regarding potential allergenicity risk assessment of future products on a case by case basis. These data and findings were presented at a 2012 international symposium in Prague organized by the Protein Allergenicity Technical Committee of the International Life Sciences Institute's Health and Environmental Sciences Institute.

Evaluating pH-induced gastrointestinal aggregation of Arachis hypogaea 1 fragments as potential components of peanut allergy

The seed storage glycoprotein Arachis hypogaea (Ara h) 1 is a major allergen found in peanuts. The biochemical resistance of food proteins to protease digestion contributes to their allergenicity. The rapid proteolysis of Ara h 1 under gastric conditions challenges this model. Biophysical and in vitro digestion experiments were carried out to identify how Ara h 1 epitopes might survive digestion, despite their facile degradation. The bicupin core of Ara h 1 can be unfolded at low pH and reversibly folded at higher pH. Additionally, peptide fragments from simulated gastric digestion predominantly form noncovalent aggregates when transferred to base. Disulfide cross-links within these aggregates occur as intermediates in relatively low amounts only at early times and play no role in shielding peptides from degradation. It is proposed that peptide fragments which survive gastric conditions form large aggregates in basic environments such as the small intestine, making epitopes available for triggering an allergic response.

The sensitising capacity of intact β-lactoglobulin is reduced by co-administration with digested β-lactoglobulin

BACKGROUND

It is generally believed that protein hydrolysis in the gastrointestinal tract decreases the allergenicity of food allergens. However, it remains unknown if specific properties of digestion products determine whether a sensitisation or tolerogenic immune response will develop. We sought to examine the sensitising capacity of the cow's milk allergen β-lactoglobulin (BLG) and digestion products thereof in a Brown Norway (BN) rat model.

METHODS

Intact BLG was digested in an in vitro model simulating the gastro-duodenal digestion process and subsequently fractionated by gel permeation chromatography. BN rats were dosed with either PBS, 200 µg of intact BLG, 30 µg of intact BLG, 200 µg of partially digested BLG, 200 µg of digested BLG, or with 200 µg of a fraction of large complexes or a fraction of small complexes. Sera from BN rats were analysed for specific antibodies and avidity was measured.

RESULTS

BLG partly resisted the digestion process. However, the BLG molecules that did not survive the digestion process were rapidly broken down to peptides of sizes less than Mr 4,500. Specific antibody responses revealed that both 200 and 30 µg of intact BLG had immunogenic as well as sensitising capacity, while digested BLG could not induce any specific antibodies. Most importantly, while intact BLG showed a significant sensitising capacity when administered alone, this sensitising capacity was significantly reduced when co-administered with digested BLG.

CONCLUSIONS

Co-immunisation of intact BLG with digested BLG reduces the sensitising capacity of intact BLG, which could result from tolerogenic mechanisms induced by the digestion products.

Pepsinized cashew proteins are hypoallergenic and immunogenic and provide effective immunotherapy in mice with cashew allergy

BACKGROUND

IgE-mediated allergic reactions to cashews and other nuts can trigger life-threatening anaphylaxis. Proactive therapies to decrease reaction severity do not exist.

OBJECTIVES

We aimed to determine the efficacy of pepsin-digested cashew proteins used as immunotherapy in a murine model of cashew allergy.

METHODS

Mice were sensitized to cashew and then underwent challenges with digested or native cashew allergens to assess the allergenicity of the protein preparations. Using native or pepsinized cashew proteins, mice underwent oral or intraperitoneal sensitization protocols to determine the immunogenic properties of the protein preparations. Finally, cashew-sensitized mice underwent an immunotherapy protocol with native or pepsinized cashew proteins and subsequent provocation challenges.

RESULTS

Pepsinized cashew proteins elicited weaker allergic reactions than native cashew proteins but importantly retained the ability to stimulate cellular proliferation and cytokine production. Mice sensitized with pepsinized proteins reacted on challenge with native allergens, demonstrating that pepsinized allergens retain immunogenicity in vivo. Immunotherapy with pepsinized cashew allergens significantly decreased allergic symptoms and body temperature decrease relative to placebo after challenge with native and pepsinized proteins. Immunologic changes were comparable after immunotherapy with native or pepsinized allergens: T(H)2-type cytokine secretion from splenocytes was decreased, whereas specific IgG(1) and IgG(2a) levels were increased.

CONCLUSIONS

Pepsinized cashew proteins are effective in treating cashew allergy in mice and appear to work through the same mechanisms as native protein immunotherapy.

IgE epitopes of intact and digested Ara h 1: a comparative study in humans and rats

BACKGROUND

Allergen epitope characterization provides valuable information useful for the understanding of proteins as food allergens. It is believed that IgE epitopes in general are conformational, nevertheless, for food allergens known to sensitize through the gastrointestinal tract linear epitopes have been suggested to be of great importance.

OBJECTIVE

The aim of this study was to identify IgE specific epitopes of intact and digested Ara h 1, and to compare epitope patterns between humans and rats.

METHODS

Sera from five peanut allergic patients and five Brown Norway rats were used to identify intact and digested Ara h 1-specific IgE epitopes by competitive immunoscreening of a phage-displayed random hepta-mer peptide library using polyclonal IgE from the individual sera. The resulting peptide sequences were mapped on the surface of a three-dimensional structure of the Ara h 1 molecule to mimic epitopes using a computer-based algorithm.

RESULTS

Patients as well as rats were shown to have individual IgE epitope patterns. All epitope mimics were conformational and found to cluster into three different areas of the Ara h 1 molecule. Five epitope motifs were identified by patient IgE, which by far accounted for most of the eluted peptide sequences. Epitope patterns were rather similar for both intact and digested Ara h 1 as well as for humans and rats.

CONCLUSIONS

Individual patient specific epitope patterns have been identified for the major allergen Ara h 1. IgE binding epitopes have been suggested as biomarkers for persistency and severity of food allergy, wherefore recognition of particular epitope patterns or motifs could be a valuable tool for prevention, diagnosis, and treatment of food allergy.

Digested Ara h 1 loses sensitizing capacity when separated into fractions

The major peanut allergen Ara h 1 is an easily digestible protein under physiological conditions. The present study revealed that pepsin digestion products of Ara h 1 retained the sensitizing potential in a Brown Norway rat model, while this sensitizing capacity was lost by separating the digest into fractions by gel permeation chromatography. Protein chemical analysis showed that the peptide composition as well as the aggregation profiles of the fractions of Ara h 1 digest differed from that of the whole pool. These results indicate that the sensitizing capacity of digested Ara h 1 is a consequence of the peptides being in an aggregated state resembling the intact molecule or that most peptides of the digests need to be present in the same solution, having a synergistic or adjuvant effect and thereby augmenting the immune response against other peptides.