Animal models of allergen-specific immunotherapy in food allergy: Overview and opportunities

Marine-Derived Alternariol Monomethyl Ether Alleviates Ovalbumin-Induced Food Allergy by Suppressing MAPK and NF-κB Signaling Pathways of Mast Cells

The prevalence of food allergies has grown dramatically over the past decade. Recently, studies have shown the potential of marine substances to alleviate food allergies. We utilized a rat basophilic leukemia (RBL)-2H3 model to evaluate the antiallergic effects of alternariol monomethyl ether (AME) extracted from marine fungi Alternaria sp. Our results showed that AME attenuated food allergy symptoms in mice and reduced histamine release in serum. The population of mast cells in the spleen and mesenteric lymph nodes was considerably reduced. Moreover, in vitro assays also revealed that AME inhibited the release of β-hexosaminidase and histamine. Transcriptomic analysis uncovered that AME regulated gene expression associated with mast cells. Additionally, Western blotting demonstrated that AME suppressed mast cell activation by modulating MAPK and NF-κB signaling pathways. Taken together, these findings provide a theoretical basis for the potential antiallergic use of marine-derived compounds in the development of functional foods.

A Murine Model of Food Allergy by Epicutaneous Adjuvant-Free Allergen Sensitization Followed by Oral Allergen Challenge Combined with Aspirin for Enhanced Detection of Hypersensitivity Manifestations and Immunotherapy Monitoring

Food allergy is one of the major existing health problems, but no effective treatment is available. In the current work, a murine model that closely mimics pathogenesis of human food allergy and its quantifiable diagnostic parameter design, even for mild hypersensitivity reactions, were established. BALB/c mice were epicutaneously sensitized with 1 mg chicken egg ovomucoid (OVM) or cow's milk casein, free of adjuvants, five times a week for two consecutive weeks. Eleven days later, allergen-specific IgG1 and IgE in serum were measured by ELISA. On day 25, 20 mg OVM or 12 mg α-casein was administered orally, and allergic reactions such as the fall in rectal temperature, symptom scores during 90-120 min, serum mast cell protease-1 and cytokine levels were monitored. The detection of mild allergic reactions due to adjuvant-free allergen sensitization and oral allergen challenge routes was amplified by the combination of oral allergen and aspirin administration simultaneously or aspirin administration within 15-30 min before an allergen challenge. Quantification of the maximum symptom score and the frequency of symptoms during the monitoring period improved evaluation accuracy of food allergy signals. Based on these results, efficacy of casein oral immunotherapy for cow's milk allergies, which are generally difficult to detect, was monitored adequately.

Preparation, Identification and Application of β-Lactoglobulin Hydrolysates with Oral Immune Tolerance

To reveal, for the first time, the mechanism of T cell epitope release from β-lactoglobulin that induces oral immune tolerance, a strategy for the prediction, preparation, identification and application of β-lactoglobulin hydrolysate with oral immune tolerance was established using the bioinformatics method, hydrolysis, mass spectrometry, T cell proliferation assays and animal experiments. Some T cell epitope peptides of β-lactoglobulin were identified for the first time. The hydrolysates of trypsin, protamex and papain showed oral tolerance, among which the hydrolysates of protamex and papain have been reported for the first time. Although the neutral protease hydrolysate contained T cell epitopes, it still had allergenicity. The mechanism behind oral immune tolerance induction by T cell epitopes needs to be further revealed. In addition, the trypsin hydrolysate with abundant T cell epitopes was added to whey protein to prepare the product for oral immune tolerance. Overall, this study provides insights into the development of new anti-allergic milk-based products and their application in the clinical treatment of milk allergies.

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.

A2 adenosine receptor contributes to the development of cow's milk protein allergy via regulating regulatory T cells

Objective(s):

A2 adenosine receptor (A2AR) is a novel promising target for the treatment of inflammatory and allergic diseases. However, its role in the development of cow’s milk protein allergy (CMPA) has not been elucidated. The present study was designed to investigate the function of A2AR in CMPA development.

Materials and Methods:

BALB/c mice were sensitized and challenged with ovalbumin (OVA) to induce allergic responses. The model was assessed by detecting allergic responses and plasma-specific IgE levels. The levels of A2AR were measured by PCR and flow cytometry. The subpopulation of Treg cells was analysed.

Results:

The mice sensitized and challenged with OVA showed classic allergic symptoms, such as acute allergic skin responses, increased anaphylactic shock symptom scores, and higher levels of total IgE, OVA-specific IgE, IgG1 and IgG2a. OVA-sensitized mice and CMPA patients showed decreased levels of A2AR and Treg cells. Interestingly, we observed a positive correlation between A2AR expression and Treg levels in CMPA patients. Further study showed that the A2AR agonist CGS21680 blocked OVA-induced allergic reactions, and the A2AR antagonist KW-6002 amplified allergic responses. Interestingly, CGS21680 not only activated the A2AR-mediated signalling pathway but also caused an increase in the population of Treg cells. In contrast, KW-6002 therapy decreased the levels of Tregs in allergic mice.

Conclusion:

A2AR expression is downregulated in CMPA. The A2AR-mediated pathway negatively regulates the development of CMPA, at least in part, by amplifying the differentiation of Tregs.

Induction of food tolerance is dependent on intestinal inflammatory state

Food allergies are usually managed by food avoidance. Hidden allergens in food, due to cross-contamination and/or allergenic additives added during production, place an important concern in today's increasing food allergy cases worldwide. Previous studies showed that the introduction of unacquainted food components, in an inflamed intestine, results in sensitization to this food. Thus, our aim was to evaluate the kinetics of multiple food allergy induction. Adult male C57BL/6 mice were divided into five groups, four of which were submitted to an intestinal inflammation induction protocol to peanuts. Egg white (OVA) diluted 1:5 v/v in distilled water was instilled by gavage 6h-before (PRIOR), concomitant (AT) and 6h-after (DURING) the onset of the peanut challenge diet. Positive control (POS CONT) and NEG CONT received saline per gavage. Finally, animals were challenged with subcutaneous injections of OVA. Results showed no changes in diet intake were observed. Anti-OVA polyisotypic IgG antibody titers significantly increased in AT. Flow cytometry revealed significant decrease in CD4⁺CD25⁺Foxp3⁺ and significant increase in TCD8⁺ in AT. Histomorphometrically, AT and DURING were classified as Infiltrative and Partial Destruction stages. PRIOR was classified as Infiltrative, while POS CONT was classified as Partial Destruction. NEG CONT was classified as Normal. Together, our results confirm that the introduction of unfamiliar food only a few hours before the initiation of a gut inflammation process is able to induce oral tolerance, however the introduction of a dietary protein concomitant to the onset or during an ongoing gut inflammation may induce multiple allergies.

Recombination Lactococcus lactis expressing Helicobacter pylori neutrophil-activating protein A attenuates food allergy symptoms in mice

BACKGROUND

Food allergy has been a significant public health issue with growing severity, prevalence and limited treatments. The neutrophil-activating protein A subunit (NapA) of Helicobacter pylori has been shown to have therapeutic potential in allergic diseases.

METHODS

The NapA expression efficiency of recombinant Lactococcus lactis(L.lactis) were determined. The effects of recombinant bacterium on food allergy in Balb/c mice were also investigated.

RESULTS

NapA were delivered and expressed efficiently via L. lactis. The engineered bacterium ameliorated food allergy symptoms (acute diarrhea and intestinal inflammation) and decreased serum histamine levels. In addition, the secretion of OVA-specific IgG2a, IFN-γ was promoted and the level of IL-4, OVA-specific IgE was restrained.

CONCLUSIONS

The recombinant strain may attenuate food allergy in mice through immune regulatory effect, which may be a promising approach for preventing or treating food allergy.

Applications of Mouse Models to the Study of Food Allergy

Mouse models of allergic disease offer numerous advantages when compared to the models of other animals. However, selection of appropriate mouse models is critical to advance the field of food allergy by revealing mechanisms of allergy and for testing novel therapeutic approaches. All current mouse models for food allergy have weaknesses that may limit their applicability to human disease. Aspects such as the genetic predisposition to allergy or tolerance from the strain of mouse used, allergen dose, route of exposure (oral, intranasal, intraperitoneal, or epicutaneous), damage of the epithelial barrier, use of adjuvants, food matrix effects, or composition of the microbiota should be considered prior to the selection of a specific murine model and contemplated according to the intended purpose of the study. This chapter reviews our current knowledge on the application of mouse models to food allergy research and the variables that may influence the successful development of each type of model.

B regulatory cells in allergy

B cells have classically been recognized for their unique and indispensable role in the production of antibodies. Their potential as immunoregulatory cells with anti-inflammatory functions has received increasing attention during the last two decades. Herein, we highlight pioneering studies in the field of regulatory B cell (Breg) research. We will review the literature on Bregs with a particular focus on their role in the regulation of allergic inflammation.

Production of allergen-specific immunotherapeutic agents for the treatment of food allergy

Allergen-specific immunotherapy (IT) is emerging as a viable avenue for the treatment of food allergies. Clinical trials currently investigate raw or slightly processed foods as therapeutic agents, as trials using food-grade agents can be performed without the strict regulations to which conventional drugs are subjected. However, this limits the ability of standardization and may affect clinical trial outcomes and reproducibility. Herein, we provide an overview of methods used in the production of immunotherapeutic agents for the treatment of food allergies, including processed foods, allergen extracts, recombinant allergens, and synthetic peptides, as well as the physical and chemical processes for the reduction of protein allergenicity. Commercial interests currently favor producing standardized drug-grade allergen extracts for therapeutic use, and clinical trials are ongoing. In the near future, recombinant production could replace purification strategies since it allows the manufacturing of pure, native allergens or sequence-modified allergens with reduced allergenicity. A recurring issue within this field is the inadequate reporting of production procedures, quality control, product physicochemical characteristics, allergenicity, and immunological properties. This information is of vital importance in assessing therapeutic standardization and clinical safety profile, which are central parameters for the development of future therapeutic agents.

Therapeutic DNA vaccine attenuates itching and allergic inflammation in mice with established biting midge allergy

Forcipomyia taiwana is a tiny hematophagous midge that attacks en masse. It is responsible for the most prevalent biting insect allergy in Taiwan. For t 2 is its major allergen. The intense itchy reactions can prevent allergic individuals from performing their regular daily outdoor activities. This study aimed to investigate whether the For t 2 DNA vaccine was effective in treating mice with established biting midge allergy. Mice were sensitized with recombinant For t 2 proteins or whole midge extracts. Two to four consecutive shots of various concentrations of For t 2 DNA vaccine, with or without CpG adjuvants, were then administered to midge-sensitized mice. Mice that received two shots of 50–100 μg For t 2 DNA vaccine showed a significant reduction in allergen-induced bouts of scratching, For t 2-specific IgE, specific IgG1/IgG2a ratio in sera, skin eosinophil infiltration, and IL-31 production, as well as IL-4 and IL-13 production by splenocytes. Two doses of For t 2 DNA vaccine one week apart was sufficient to treat mice with established biting midge allergy. The treatment resulted in clinical, immunological, and histopathological improvements. We recommend that this low-cost, convenient treatment strategy be developed for use in humans who are allergic to biting midges.

Assessment of the potential allergenicity of genetically-engineered food crops

An extensive safety assessment process exists for genetically-engineered (GE) crops. The assessment includes an evaluation of the introduced protein as well as the crop containing the protein with the goal of demonstrating the GE crop is "as-safe-as" non-GE crops in the food supply. One of the evaluations for GE crops is to assess the expressed protein for allergenic potential. Currently, no single factor is recognized as a predictor for protein allergenicity. Therefore, a weight-of-the-evidence approach, which accounts for a variety of factors and approaches for an overall assessment of allergenic potential, is conducted. This assessment includes an evaluation of the history of exposure and safety of the gene(s) source; protein structure (e.g. amino acid sequence identity to human allergens); stability of the protein to pepsin digestion in vitro; heat stability of the protein; glycosylation status; and when appropriate, specific IgE binding studies with sera from relevant clinically allergic subjects. Since GE crops were first commercialized over 20 years ago, there is no proof that the introduced novel protein(s) in any commercialized GE food crop has caused food allergy.