The immunology of food allergy

Spontaneous food allergy in Was-/- mice occurs independent of FcεRI-mediated mast cell activation

BACKGROUND

Food allergies are a growing health problem, and the development of therapies that prevent disease onset is limited by the lack of adjuvant-free experimental animal models. We compared allergic sensitization in patients with food allergy or Wiskott-Aldrich syndrome (WAS) and defined whether spontaneous disease in Was^-/- mice recapitulates the pathology of a conventional disease model and/or human food allergy.

METHODS

Comparative ImmunoCAP ISAC microarray was performed in patients with food allergy or WAS. Spontaneous food allergy in Was^-/- mice was compared to an adjuvant-based model in wild-type mice (WT-OVA/alum). Intestinal and systemic anaphylaxis was assessed, and the role of the high-affinity IgE Fc receptor (FcεRI) in allergic sensitization was evaluated using Was^-/- Fcer1a^-/- mice.

RESULTS

Polysensitization to food was detected in both WAS and food-allergic patients which was recapitulated in the Was^-/- model. Oral administration of ovalbumin (OVA) in Was^-/- mice induced low titers of OVA-specific IgE compared to the WT-OVA/alum model. Irrespectively, 79% of Was^-/- mice developed allergic diarrhea following oral OVA challenge. Systemic anaphylaxis occurred in Was^-/- mice (95%) with a mortality rate >50%. Spontaneous sensitization and intestinal allergy occurred independent of FcεRI expression on mast cells (MCs) and basophils.

CONCLUSIONS

Was^-/- mice provide a model of food allergy with the advantage of mimicking polysensitization and low food-antigen IgE titers as observed in humans with clinical food allergy. This model will facilitate studies on aberrant immune responses during spontaneous disease development. Our results imply that therapeutic targeting of the IgE/FcεRI activation cascade will not affect sensitization to food.

Transplant-acquired food allergy: current perspectives

Mechanisms that regulate the tolerance to dietary proteins or the loss of this and subsequent development of disease are poorly understood. In food allergy, there is growing awareness of the urgency in understanding these events to aid in the development of next-generation therapies and interventions. This review focuses on the accumulating evidence related to food allergy that develops after transplantation. This intriguing immunological phenomenon has been described in several different types of transplant settings and to variety of different foods. We outline these studies and the evidence from them that support transplant-acquired food allergy being a process regulated by both the donor allergic status and the recipient genetics and treatments. A number of key risk factors seem prevalent throughout transplant-acquired food allergy and include type of transplant, age and general health of the recipient, modality of immunosuppression and potentially the genetics of both donor and recipient. Importantly, these studies provide a window into better general understanding of food allergy, and facilitate clearer understanding of the critical immunological and epidemiological factors needed to allow the adoptive transfer of a food-specific allergic disease from one individual to another.

A biotinylated peptide, BP21, as a novel potent anti-anaphylactic agent targeting platelet-activating factor

Platelet-activating factor (PAF) is an important mediator of anaphylaxis and is therefore an anti-anaphylactic drug target. We recently reported that synthetic N-terminally biotinylated peptides (BP4-BP29) inhibit PAF by directly interacting with PAF and its metabolite/precursor lyso-PAF. In this study, we investigated whether the biotinylated peptides can inhibit anaphylactic reactions in vivo. In mouse models of anaphylaxis, one of the peptides, BP21, markedly and dose-dependently inhibited hypothermia with a maximum dose-response within 30 min after administration, even at doses 20 times lesser than doses of the known PAF antagonist CV-3988. In contrast, the anti-hypothermic effect of BGP21, in which the Tyr-Lys-Asp-Gly sequence in BP21 was modified to a Gly-Gly-Gly-Gly sequence, was less than that of BP21. The alanine scanning and shuffling the amino acid residues of BP4 (Tyr-Lys-Asp-Gly) demonstrated that the Tyr-Lys-Asp-Gly consensus sequence is important for the inhibitory effect of the peptide on hypothermia. BP21 also suppressed vascular permeability during anaphylaxis with a maximum dose-response within 30 min of administration. In a rat model of hind paw oedema, BP21 significantly inhibited the oedema induced by PAF but not that induced by the other pro-inflammatory mediators, such as histamine, serotonin, and bradykinin. Tryptophan fluorescence measurements showed that BP21 interacted with PAF, but not with histamine, serotonin, or bradykinin. In contrast, BGP21 did not interact with PAF. These results suggest that biotinylated peptides, especially BP21, can specifically and markedly inhibit anaphylactic reactions in vivo and that this involves direct interaction of its Tyr-Lys-Asp-Gly region with PAF. Therefore, a biotinylated peptide, BP21, can be used as novel potential anti-anaphylactic drugs targeting PAF. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Allergic diseases in children with attention deficit hyperactivity disorder: a systematic review and meta-analysis

BACKGROUND

Reports of frequent manifestation of allergic diseases in children with attention deficit hyperactivity disorder (ADHD) have been the subject of mounting clinical interest. However, evidence supporting the association between ADHD and allergies is inconsistent and has yet to be systematically reviewed. The objective of this study was to compile and assess available studies on the association between ADHD and allergic diseases in children.

METHODS

A comprehensive search using MEDLINE, EMBASE, the Cochrane library, and CINAHL databases was completed in 23 November 2015. The inclusion criteria for studies were that the research assessed allergic diseases in children, 18 years of age and younger, with a diagnosis of ADHD and that a distinct comparison group was incorporated. Any comparative studies, encompassing both randomized controlled trials and observational studies, were considered for inclusion. Two review authors independently assessed the quality of the selected studies by the use of validated assessment tools, performed data extraction and conducted meta-analysis according to Cochrane Collaboration guidelines.

RESULTS

Five eligible studies were included in this systematic review. Of these studies, three were case-control and two were cross sectional studies. A majority of information from the five studies was classified as having low or unclear risk of bias. The meta-analysis showed an association between children with ADHD and asthma compared with the control groups (OR: 1.80, 95% CI: 1.57 - 2.07; five studies, low quality of evidence), but did not indicate an association between food allergy and ADHD (OR: 1.13, 95% CI: 0.88 - 1.47; three studies very low quality of evidence). The odds of experiencing allergic rhinitis, atopic dermatitis, and allergic conjunctivitis were slightly higher in children with ADHD compared with control groups, though a substantial statistical heterogeneity was notable in the overall effect estimates.

CONCLUSIONS

The findings from this review and meta-analysis show that children with ADHD are more likely to have asthma, allergic rhinitis, atopic dermatitis, and allergic conjunctivitis than their counterparts. Interventions including strategies for managing allergies in children with ADHD would be beneficial.

[Immunological background and pathomechanisms of food allergies]

Recent advances in immunology have greatly improved our understanding of the pathomechanisms of food allergies. Food allergies are caused and maintained by complex interactions of the innate and adaptive immune system involving antigen-presenting cells (APC), T cells, group 2 innate lymphoid cells (ILC2), epithelial cells (EC) and effectors cells. Additionally, epigenetic factors, the intestinal microbiome and nutritional factors modulating the gastrointestinal lymphatic tissue probably have a significant impact on allergy development. However, why certain individuals develop tolerance while others mount allergic responses, the factors defining the allergenicity of food proteins, as well as the immunological mechanisms triggering allergy development have yet to be analyzed in detail.

Oral administration of Clostridium butyricum CGMCC0313-1 inhibits β-lactoglobulin-induced intestinal anaphylaxis in a mouse model of food allergy

Background

Probiotic bacteria can induce immune regulation or immune tolerance in patients with allergic diseases, but the underlying mechanisms are still unclear. There has been a growing interest in the use of beneficial bacteria for allergic diseases recently. This study aimed at exploring whether Clostridium butyricum CGMCC0313-1 (C. butyricum) can reduce β-lactoglobulin(BLG)-induced intestinal anaphylaxis in a murine model of food allergy.

Methods

The preventive and therapeutic effects of oral C. butyricum on anaphylactic symptoms induced via BLG in food allergy mice were investigated. Intestinal anaphylaxis, T helper (Th)-specific cytokines and transcription factors, secretory IgA (sIgA), CD4+ CD25+ Foxp3Treg cell and histopathological alterations were examined.

Results

Clostridium butyricum significantly ameliorated intestinal anaphylaxis symptoms in the food allergy mice. sIgA and CD4+ CD25+ Foxp3Treg cell were increased by oral C. butyricum. It also reversed the imbalance of Th1/Th2 andTh17/Treg.

Conclusions

Clostridium butyricum reduces BLG-induced intestinal anaphylaxis in mice and might be an additional or supplementary therapy for food allergy.

Effect of a cocoa diet on the small intestine and gut-associated lymphoid tissue composition in an oral sensitization model in rats

Previous studies have attributed to the cocoa powder the capacity to attenuate the immune response in a rat oral sensitization model. To gain a better understanding of cocoa-induced mechanisms at small intestinal level, 3-week-old female Lewis rats were fed either a standard diet or a diet containing 10% cocoa for 4 weeks with or without concomitant oral sensitization with ovalbumin (OVA). Thereafter, we evaluated the lymphocyte composition of the Peyer's patches (PPL), small intestine epithelium (IEL) and lamina propria (LPL). Likewise, gene expression of several immune molecules was quantified in the small intestine. Moreover, histological samples were used to evaluate the proportion of goblet cells, IgA+ cells and granzyme+cells as well. In cocoa-fed animals, we identified a five-time reduction in the percentage of IgA+ cells in intestinal tissue together with a decreased proportion of TLR4+ IEL. Analyzing the lymphocyte composition, almost a double proportion of TCRγδ+cells and an increase of NK cell percentage in PPL and IEL were found. In addition, a rise in CD25+, CD103+ and CD62L- cell proportions was observed in CD4+ PPL from cocoa-fed animals, along with a decrease in gene expression of CD11b, CD11c and IL-10. These results suggest that changes in PPL and IEL composition and in the gene expression induced by the cocoa diet could be involved, among other mechanisms, on its tolerogenic effect.

Influence of microbiome and diet on immune responses in food allergy models

The intestinal immune system is intimately connected with the vast array of microbes present within the gut and the diversity of food components that are consumed daily. The discovery of novel molecular mechanisms, which mediate host-microbe-nutrient communication, have highlighted the important roles played by microbes and dietary factors in influencing mucosal inflammatory and allergic responses. In this review, we summarize the recent important findings in this field, which are important for food allergy and particularly relevant to animal models of food allergy.

Balancing Tolerance or Allergy to Food Proteins

Dietary proteins usually induce immune tolerance, but may trigger life-threatening immune responses in the case of food allergy. The associated type 2 immunity, linked with specific IgE production and the activation of mast cells and basophils, is well understood but the mechanisms related to preventing food allergy are still being deciphered. Recent insights into the mechanisms that regulate oral tolerance and dietary antigen sampling have revealed unique regulatory events that occur during early life and into adulthood. Drawing from both recent clinical and experimental discoveries, this article focuses on current evidence for how several key stages of life present mechanistic points that might participate in tipping the balance between food protein tolerance and allergy.

[Establishment of a rat model of oral food allergy]

OBJECTIVE

To establish a food allergy model in Brown Norway (BN) rats by gavage of ovalbumin (OVA) without any adjuvant, and to evaluate this model.

METHODS

A total of 20 male BN rats aged 3 weeks were randomly divided into allergy group and control group (n=10 each). BN rats in the allergy group were given OVA 1 mg per day by gavage, and all the rats were treated for 41 days continuously. On day 42, the rats in the allergy group were given OVA 100 mg by gavage for challenge. The rats in the control group were given normal saline of the same volume by gavage. Differences in body length, body weight, and food intake were compared between the two groups on days 7, 14, 21, 28, 35, and 42. ELISA was used to measure the serum OVA-IgE level and plasma histamine level after challenge on day 42, and the changes in rats' appearance and fecal properties were observed. The model of food allergy was considered successful when the serum OVA-IgE level in the allergy group was no less than the mean serum OVA-IgE level + 3 standard deviation in the control group.

RESULTS

There were no significant differences in body length, body weight or food intake between the allergy and control groups at all time points (P>0.05). On day 21, the control group had a significantly higher food intake than the allergy group (P<0.05). On day 42 after challenge, the allergy group showed significantly higher serum OVA-IgE and plasma histamine levels than the control group (P<0.05). The sensitization rate (rate of successful modeling) was 90%. The fecal properties showed no significant differences between the two groups.

CONCLUSIONS

OVA by gavage without any adjuvant can successfully establish the model of food allergy in BN rats and has a high success rate. Food allergy induced by OVA may reduce food intake within a short period of time, but no influence on rats' body length or body weight has been observed.

IL-10 Enhances IgE-Mediated Mast Cell Responses and Is Essential for the Development of Experimental Food Allergy in IL-10-Deficient Mice

IL-10 is a key pleiotropic cytokine that can both promote and curb Th2-dependent allergic responses. In this study, we demonstrate a novel role for IL-10 in promoting mast cell expansion and the development of IgE-mediated food allergy. Oral OVA challenge in sensitized BALB/c mice resulted in a robust intestinal mast cell response accompanied by allergic diarrhea, mast cell activation, and a predominance of Th2 cytokines, including enhanced IL-10 expression. In contrast, the development of intestinal anaphylaxis, including diarrhea, mast cell activation, and Th2 cytokine production, was significantly attenuated in IL-10(-/-) mice compared with wild-type (WT) controls. IL-10 also directly promoted the expansion, survival, and activation of mast cells; increased FcεRI expression on mast cells; and enhanced the production of mast cell cytokines. IL-10(-/-) mast cells had reduced functional capacity, which could be restored by exogenous IL-10. Similarly, attenuated passive anaphylaxis in IL-10(-/-) mice could be restored by IL-10 administration. The adoptive transfer of WT mast cells restored allergic symptoms in IL-10(-/-) mice, suggesting that the attenuated phenotype observed in these animals is due to a deficiency in IL-10-responding mast cells. Lastly, transfer of WT CD4 T cells also restored allergic diarrhea and intestinal mast cell numbers in IL-10(-/-) mice, suggesting that the regulation of IL-10-mediated intestinal mast cell expansion is T cell dependent. Our observations demonstrate a critical role for IL-10 in driving mucosal mast cell expansion and activation, suggesting that, in its absence, mast cell function is impaired, leading to attenuated food allergy symptoms.

Emergency and Hospital Care for Food-Related Anaphylaxis in Children

OBJECTIVES

Among patients with food-related anaphylaxis, to describe trends in emergency and hospital care and determine the revisit rate.

METHODS

This retrospective cohort study included children 6 months to 18 years of age with food-related anaphylaxis from 37 children's hospitals between 2007 and 2012. Summary statistics and trends for patient characteristics were evaluated. Multivariable regression was used to identify predictors for hospital admission. Revisit rates to either the emergency department (ED) and/or inpatient unit were calculated.

RESULTS

7303 patients were evaluated in the ED; 3652 (50%) were admitted to the hospital. Hospital admission rates varied widely (range, 20%-98%). Food-related anaphylaxis increased from 41 per 100 000 ED visits to 72 per 100 000 while hospital admission rates did not change. Males (odds ratio [OR], 1.2 [95% confidence interval (CI), 1.0-1.4]), patients < 1 year old (OR, 1.8 [95% CI, 1.3-2.5]), those with anaphylaxis to either peanut (OR, 1.2 [95% CI, 1.0-1.5]) or tree nut (OR, 1.7 [95% CI, 1.3-2.1]), and patients with asthma (OR, 7.4 [95% CI, 5.8-9.3]) or a chronic complex condition (OR, 5.2 [95% CI, 3.0-9.0]) were more likely to be admitted to the hospital. The 3-day revisit rate was 3% for patients discharged from the ED and 0.6% for those admitted on the index visit.

CONCLUSIONS

The incidence of food-related anaphylaxis in pediatric EDs is increasing, but rates of hospital admission are stable. Hospital admission is common but widely variable. Further research is needed to identify optimal management practices for this potentially life-threatening problem.

Allergenicity assessment strategy for novel food proteins and protein sources

To solve the future food insecurity problem, alternative and sustainable protein sources (e.g. insects, rapeseed, fava bean and algae) are now being explored for the production of food and feed. To approve these novel protein sources for future food a comprehensive risk assessment is needed according to the European food legislation. Allergenicity risk assessment might pose some major difficulties, since detailed guidance on how to assess the allergenic potential of novel foods is not available. At present, the approach relies mostly on the guidance of allergenicity assessment for genetically modified (GM) plant foods. The most recent one was proposed by EFSA (2010 and 2011); "weight-of-evidence approach". However this guidance is difficult to interpret, not completely applicable or validated for novel foods and therefore needs some adjustments. In this paper we propose a conceptual strategy which is based on the "weight-of-evidence approach" for food derived from GM plants and other strategies that were previously published in the literature. This strategy will give more guidance on how to assess the allergenicity of novel food proteins and protein sources.

An update on hypoallergenicity of peanut and soybean: where are we now?

Legumes are one of the major sources of proteins and positively correlate with the development of modern society. At the same time, unfortunately, they significantly contribute to the rising prevalence of food allergy.

Pathophysiology of Food Allergy

Food allergy is a growing public health problem that is estimated to affect 4% to 8% of children and 5% of adults. In this review, we discuss our current understanding of the pathophysiology of food allergy, from oral tolerance, to sensitization, and lastly the elicitation of an allergic response. As much of the existing evidence for the mechanisms of food allergy is derived from animal models, we include these studies where relevant. In addition, whenever possible, we review similar evidence involved in human disease and provide applications for consideration in clinical practice.

Allergic mechanisms of Eosinophilic oesophagitis

Eosinophilic oesophagitis (EoE) is characterized by oesophageal dysfunction and oesophageal eosinophilia refractory to proton-pump-inhibitor treatment. EoE is a food allergy, as elimination of food trigger(s) abrogates the disease, while trigger reintroduction causes recurrence. The allergic mechanism of EoE involves both IgE and non-IgE processes. There is a break in oral tolerance, the immune mechanism allowing enteric exposure to food and micro-organisms without causing deleterious immune responses. Changes in life-style, alterations in gut flora and use of antibiotics may be increasing disease prevalence. Mouse models of EoE and human studies revealed the role of regulatory T-cells and iNKT-cells in the pathogenesis. Th2-cytokines like IL-4, IL-5 and IL-13, and other cytokines like TGFβ and TSLP are involved, but perhaps no one cytokine is critically important for driving the disease. Control of EoE may require a pharmaceutical approach that blocks more than one target in the Th2-inflammatory pathway.

Curcumin Ingestion Inhibits Mastocytosis and Suppresses Intestinal Anaphylaxis in a Murine Model of Food Allergy

IgE antibodies and mast cells play critical roles in the establishment of allergic responses to food antigens. Curcumin, the active ingredient of the curry spice turmeric, has anti-inflammatory properties, and thus may have the capacity to regulate Th2 cells and mucosal mast cell function during allergic responses. We assessed whether curcumin ingestion during oral allergen exposure can modulate the development of food allergy using a murine model of ovalbumin (OVA)-induced intestinal anaphylaxis. Herein, we demonstrate that frequent ingestion of curcumin during oral OVA exposure inhibits the development of mastocytosis and intestinal anaphylaxis in OVA-challenged allergic mice. Intragastric (i.g.) exposure to OVA in sensitized BALB/c mice induced a robust IgE-mediated response accompanied by enhanced OVA-IgE levels, intestinal mastocytosis, elevated serum mMCP-1, and acute diarrhea. In contrast, mice exposed to oral curcumin throughout the experimental regimen appeared to be normal and did not exhibit intense allergic diarrhea or a significant enhancement of OVA-IgE and intestinal mast cell expansion and activation. Furthermore, allergic diarrhea, mast cell activation and expansion, and Th2 responses were also suppressed in mice exposed to curcumin during the OVA-challenge phase alone, despite the presence of elevated levels of OVA-IgE, suggesting that curcumin may have a direct suppressive effect on intestinal mast cell activation and reverse food allergy symptoms in allergen-sensitized individuals. This was confirmed by observations that curcumin attenuated the expansion of both adoptively transferred bone marrow-derived mast cells (BMMCs), and inhibited their survival and activation during cell culture. Finally, the suppression of intestinal anaphylaxis by curcumin was directly linked with the inhibition of NF-κB activation in curcumin-treated allergic mice, and curcumin inhibited the phosphorylation of the p65 subunit of NF-κB in BMMCs. In summary, our data demonstrates a protective role for curcumin during allergic responses to food antigens, suggesting that frequent ingestion of this spice may modulate the outcome of disease in susceptible individuals.

The future of biologics: applications for food allergy

Allergic diseases affect millions worldwide, with growing evidence of an increase in allergy occurrence over the past few decades. Current treatments for allergy include corticosteroids to reduce inflammation and allergen immunotherapy; however, some subjects experience treatment-resistant inflammation or adverse reactions to these treatments, and there are currently no approved therapeutics for the treatment of food allergy. There is a dire need for new therapeutic approaches for patients with poorly controlled atopic diseases and a need to improve the safety and effectiveness of allergen immunotherapy. Improved understanding of allergy through animal models and clinical trials has unveiled potential targets for new therapies, leading to the development of several biologics to treat allergic diseases. This review focuses on the mechanisms that contribute to allergy, with an emphasis on future targets for biologics for the treatment of food allergy. These biologics include immunotherapy with novel anti-IgE antibodies and analogs, small-molecule inhibitors of cell signaling, anti-type 2 cytokine mAbs, and TH1-promoting adjuvants.

Food processing and allergenicity

Food processing can have many beneficial effects. However, processing may also alter the allergenic properties of food proteins. A wide variety of processing methods is available and their use depends largely on the food to be processed. In this review the impact of processing (heat and non-heat treatment) on the allergenic potential of proteins, and on the antigenic (IgG-binding) and allergenic (IgE-binding) properties of proteins has been considered. A variety of allergenic foods (peanuts, tree nuts, cows' milk, hens' eggs, soy, wheat and mustard) have been reviewed. The overall conclusion drawn is that processing does not completely abolish the allergenic potential of allergens. Currently, only fermentation and hydrolysis may have potential to reduce allergenicity to such an extent that symptoms will not be elicited, while other methods might be promising but need more data. Literature on the effect of processing on allergenic potential and the ability to induce sensitisation is scarce. This is an important issue since processing may impact on the ability of proteins to cause the acquisition of allergic sensitisation, and the subject should be a focus of future research. Also, there remains a need to develop robust and integrated methods for the risk assessment of food allergenicity.

Effect of a protein-free diet in the development of food allergy and oral tolerance in BALB/c mice

The aim of the present study was to investigate the effect of a protein-free diet in the induction of food allergy and oral tolerance in BALB/c mice. The experimental model used was mice that were fed, since weaning up to adulthood, a balanced diet in which all dietary proteins were replaced by amino acid diet (Aa). The absence of dietary proteins did not prevent the development of food allergy to ovalbumin (OVA) in these mice. However, Aa-fed mice produced lower levels of IgE, secretory IgA and cytokines. In addition, when compared with mice from control group, Aa-fed mice had a milder aversive reaction to the allergen measured by consumption of OVA-containing solution and weight loss during food allergy development. In addition, mice that did not have dietary proteins in their diets were less susceptible to induction of oral tolerance. One single oral administration was not enough to suppress specific serum Ig and IgG1 levels in the Aa-fed group, although it was efficient to induce suppression in the control group. The present results indicate that the stimulation by dietary proteins alters both inflammatory reactivity and regulatory immune reactivity in mice probably due to their effect in the maturation of the immune system.