Food allergy: mechanisms and therapeutics

A mouse model of food allergy permitting skin and nasal symptoms

PURPOSE

Developing experimental animal models that show clinical symptoms and methods for quantitative and objective evaluation are important for understanding food allergies. Therefore, this study aimed to develop an ovalbumin (OVA)-induced mouse model of food allergy and a useful method to evaluate the symptoms of food allergy.

MATERIAL/METHODS

Mice were sensitized via intraperitoneal injection of OVA. Subsequently, local sensitization was performed once weekly by oral administration of OVA. Itching and nasal symptoms were observed after oral administration of the antigen. First, we examined the dose-dependency of the antigen. Symptoms were checked weekly. In order to confirm food allergy symptoms, the effect of histamine H1 receptor antagonist was examined. Finally, we measured antigen-specific IgE antibody levels in the serum.

RESULTS

Scratching behavior, sneezing and nasal rubbing were increased. Both itching and rhinitis symptoms increased steadily, after which, the number of symptoms remained almost constant. No difference was observed between the results of 3- and 5-week-old mice. Cetirizine inhibited these symptoms in a dose-dependent manner. In addition, antigen-specific IgE antibodies were produced in both 3- and 5-week-old mice.

CONCLUSIONS

This method may be useful for evaluating the symptoms of skin and rhinitis that could not be assessed in the conventional food allergy model and could be induced with a low dose of antigen. In particular, the developed method, which measures the number of itching and nasal symptoms, may enable quantitative, objective, and noninvasive evaluation of food allergy severity.

Immune monitoring for precision medicine in allergy and asthma

'Precision Medicine' embodies the analyses of extensive data collected from patients and their environments to identify and apply patient-specific prophylactic strategies and medical treatments to improve clinical outcomes and healthcare cost-effectiveness. Many new methods have been developed for evaluating the activity of the human immune system. Such 'immune monitoring' approaches are now being used in studies of allergy and asthma in the hope of identifying better correlates of disease status, predictors of therapeutic outcomes, and potential side-effects of treatment. Together with analyses of family histories, genetic and other biometric data, and measurements of exposures to environmental and other risk factors for developing or exacerbating disease, immune monitoring approaches promise to enable 'Precision Medicine' for allergic diseases and asthma.

Oral immunotherapy for food allergy: A Spanish guideline. Immunotherapy egg and milk Spanish guide (items guide). Part I: Cow milk and egg oral immunotherapy: Introduction, methodology, rationale, current state, indications contraindications and oral immunotherapy build-up phase

INTRODUCTION

Cow's milk and egg are the most frequent causes of food allergy in the first years of life. Treatments such as oral immunotherapy (OIT) have been investigated as an alternative to avoidance diets. No clinical practice guides on the management of OIT with milk and egg are currently available.

OBJECTIVES

To develop a clinical guide on OIT based on the available scientific evidence and the opinions of experts.

METHODS

A review was made of studies published in the period between 1984 and June 2016, Doctoral Theses published in Spain, and summaries of communications at congresses (SEAIC, SEICAP, EAACI, AAAAI), with evaluation of the opinion consensus established by a group of experts pertaining to the scientific societies SEICAP and SEAIC.

RESULTS

Recommendations have been established regarding the indications, requirements and practical aspects of the different phases of OIT, as well as special protocols for patients at high risk of suffering adverse reactions.

CONCLUSIONS

A clinical practice guide is presented for the management of OIT with milk and egg, based on the opinion consensus of Spanish experts.

New Trends in Food Allergens Detection: Toward Biosensing Strategies

Food allergens are a real threat to sensitized individuals. Although food labeling is crucial to provide information to consumers with food allergies, accidental exposure to allergenic proteins may result from undeclared allergenic substances by means of food adulteration, fraud or uncontrolled cross-contamination. Allergens detection in foodstuffs can be a very hard task, due to their presence usually in trace amounts, together with the natural interference of the matrix. Methods for allergens analysis can be mainly divided in two large groups: the immunological assays and the DNA-based ones. Mass spectrometry has also been used as a confirmatory tool. Recently, biosensors appeared as innovative, sensitive, selective, environmentally friendly, cheaper and fast techniques (especially when automated and/or miniaturized), able to effectively replace the classical methodologies. In this review, we present the advances in the field of food allergens detection toward the biosensing strategies and discuss the challenges and future perspectives of this technology.

CD4+ T cell responses in Balb/c mice with food allergy induced by trinitrobenzene sulfonic acid and ovalbumin

The rapid increase in atopic diseases is potentially linked to increased hapten exposure, however, the role of haptens in the pathogenesis of food allergy remains unknown. Further studies are required to elucidate the cluster of differentiation 4 positive (CD4+) T cell response to food allergy induced by haptens. Dendritic cells were primed by trinitrobenzene sulfonic acid (TNBS) as a hapten or ovalbumin (OVA) as a model antigen, in a cell culture model. BALB/c mice were sensitized using TNBS and/or OVA. Intestinal Th1/Th2 cell and ovalbumin specific CD4+ T cells proliferation, intestinal cytokines (interleukin‑4 and interferon‑γ) in CD4+ T cells were evaluated. TNBS increased the expression of T cell immunoglobulin and mucin domain‑4 and tumor necrosis factor ligand superfamily member 4 in dendritic cells. Skewed Th2 cell polarization, extensive expression of interleukin‑4, reduced expression of interferon‑γ and forkhead box protein P3 were elicited following concomitant exposure to TNBS and OVA, with reduced regulatory T cells in the mouse intestinal mucosa, whereas a Th1 response was detected when challenged by TNBS or OVA alone. This data suggests that TNBS, as a hapten, combined with food antigens may lead to a Th2 cell response in the intestinal mucosa.

The connection between seasonal allergies, food allergies, and rhinosinusitis: what is the evidence?

PURPOSE OF REVIEW

Rhinosinusitis affects an estimated one in seven adults in the United States. Otolaryngologists are intimately involved in the care of patients with rhinosinusitis and other upper airway inflammatory conditions through procedures such as endoscopic sinus surgery and, therefore, would benefit from a deeper understanding of the associated comorbidities and their management. Recent evidence has suggested several connections between the underlying disease of rhinosinusitis, seasonal allergies, and food allergies. The authors of the present review seek to provide a focused analysis of the recent literature with respect to epidemiology, pathophysiology, and treatment options concerning these conditions.

RECENT FINDINGS

Evidence has connected the function of filaggrin, a skin barrier protein, with the pathogenesis of allergic rhinosinusitis and food allergy. Additionally, decreased levels of regulatory B cells and T cells are associated with and play a role in atopic disease. Overlapping treatment modalities between these conditions suggest similar conclusions.

SUMMARY

Future research into the role of the skin barrier, regulatory immune cell functioning, transforming growth factor-β, and other cytokine signaling, and treatment options such as omalizumab and azelastine is likely to have profound impact on clinicians' management of patients with these disorders and their comorbidities.

Immune Modulation by Vitamin D and Its Relevance to Food Allergy

Apart from its classical function in bone and calcium metabolism, vitamin D is also involved in immune regulation and has been linked to various cancers, immune disorders and allergic diseases. Within the innate and adaptive immune systems, the vitamin D receptor and enzymes in monocytes, dendritic cells, epithelial cells, T lymphocytes and B lymphocytes mediate the immune modulatory actions of vitamin D. Vitamin D insufficiency/deficiency early in life has been identified as one of the risk factors for food allergy. Several studies have observed an association between increasing latitude and food allergy prevalence, plausibly linked to lower ultraviolet radiation (UVR) exposure and vitamin D synthesis in the skin. Along with mounting epidemiological evidence of a link between vitamin D status and food allergy, mice and human studies have shed light on the modulatory properties of vitamin D on the innate and adaptive immune systems. This review will summarize the literature on the metabolism and immune modulatory properties of vitamin D, with particular reference to food allergy.

Detection of the peanut allergen Ara h 6 in foodstuffs using a voltammetric biosensing approach

A voltammetric biosensor for Ara h 6 (a peanut allergen) detection in food samples was developed. Gold nanoparticle-modified screen-printed carbon electrodes were used to develop a sandwich-type immunoassay using two-monoclonal antibodies. The antibody-antigen interaction was detected through the electrochemical detection of enzymatically deposited silver. The immunosensor presented a linear range between 1 and 100 ng/ml, as well as high precision (inter-day RSD ≤9.8%) and accuracy (recoveries ≥96.7%). The detection and quantification limits were 0.27 and 0.88 ng/ml, respectively. It was possible to detect small levels of Ara h 6 in complex food matrices.

Acid hydrolysis of wheat gluten induces formation of new epitopes but does not enhance sensitizing capacity by the oral route: a study in "gluten free" Brown Norway rats

Background

Acid hydrolyzed wheat proteins (HWPs) are used in the food and cosmetic industry as emulsifiers. Cases of severe food allergic reactions caused by HWPs have been reported. Recent data suggest that these reactions are caused by HWPs produced by acid hydrolysis.

Objectives

To examine the sensitizing capacity of gluten proteins per se when altered by acid or enzymatic hydrolysis relative to unmodified gluten in rats naïve to gluten.

Methods

High IgE-responder Brown Norway (BN) rats bred on a gluten-free diet were sensitized without the use of adjuvant to three different gluten products (unmodified, acid hydrolyzed and enzymatic hydrolyzed). Rats were sensitized by intraperitoneal (i.p.) immunization three times with 200 µg gluten protein/rat or by oral dosing for 35 days with 0.2, 2 or 20 mg gluten protein/rat/day. Sera were analyzed for specific IgG and IgE and IgG-binding capacity by ELISA. IgE functionality was measured by rat basophilic leukemia (RBL) assay.

Results

Regardless of the route of dosing, all products had sensitizing capacity. When sensitized i.p., all three gluten products induced a strong IgG1 response in all animals. Acid hydrolyzed gluten induced the highest level of specific IgE but with a low functionality. Orally all three gluten products induced specific IgG1 and IgE but with different dose-response relations. Sensitizing rats i.p. or orally with unmodified or enzymatic hydrolyzed gluten induced specific IgG1 responses with similar binding capacity which was different from that of acid hydrolyzed gluten indicating that acid hydrolysis of gluten proteins induces formation of ‘new’ epitopes.

Conclusions

In rats not tolerant to gluten acid hydrolysis of gluten enhances the sensitizing capacity by the i.p. but not by the oral route. In addition, acid hydrolysis induces formation of new epitopes. This is in contrast to the enzymatic hydrolyzed gluten having an epitope pattern similar to unmodified gluten.

Detection of Ara h 1 (a major peanut allergen) in food using an electrochemical gold nanoparticle-coated screen-printed immunosensor

A gold nanoparticle-coated screen-printed carbon electrode was used as the transducer in the development of an electrochemical immunosensor for Ara h 1 (a major peanut allergen) detection in food samples. Gold nanoparticles (average diameter = 32 nm) were electrochemically generated on the surface of screen-printed carbon electrodes. Two monoclonal antibodies were used in a sandwich-type immunoassay and the antibody-antigen interaction was electrochemically detected through stripping analysis of enzymatically (using alkaline phosphatase) deposited silver. The total time of the optimized immunoassay was 3h 50 min. The developed immunosensor allowed the quantification of Ara h 1 between 12.6 and 2000 ng/ml, with a limit of detection of 3.8 ng/ml, and provided precise (RSD <8.7%) and accurate (recovery >96.6%) results. The immunosensor was successfully applied to the analysis of complex food matrices (cookies and chocolate), being able to detect Ara h 1 in samples containing 0.1% of peanut.

The impact of structural integrity and route of administration on the antibody specificity against three cow's milk allergens - a study in Brown Norway rats

Background

Characterisation of the specific antibody response, including the epitope binding pattern, is an essential task for understanding the molecular mechanisms of food allergy. Examination of antibody formation in a controlled environment requires animal models. The purpose of this study was to examine the amount and types of antibodies raised against three cow’s milk allergens; β-lactoglobulin (BLG), α-lactalbumin (ALA) and β-casein upon oral or intraperitoneal (i.p.) administration. A special focus was given to the relative amount of antibodies raised against linear versus conformational epitopes.

Methods

Specific antibodies were raised in Brown Norway (BN) rats. BN rats were dosed either (1) i.p. with the purified native cow’s milk allergens or (2) orally with skimmed milk powder (SMP) alone or together with gluten, without the use of adjuvants. The allergens were denatured by reduction and alkylation, resulting in unfolding of the primary structure and a consequential loss of conformational epitopes. The specific IgG1 and IgE responses were analysed against both the native and denatured form of the three cow’s milk allergens, thus allowing examination of the relative amount of linear versus conformational epitopes.

Results

The inherent capacity to induce specific IgG1 and IgE antibodies were rather similar upon i.p. administration for the three cow’s milk allergens, with BLG = ALA > β-casein. Larger differences were found between the allergens upon oral administration, with BLG > ALA > β-casein. Co-administration of SMP and gluten had a great impact on the specific antibody response, resulting in a significant reduced amount of antibodies. Together results indicated that most antibodies were raised against conformational epitopes irrespectively of the administration route, though the relative proportions between linear and conformational epitopes differed remarkably between the allergens.

Conclusions

This study showed that the three-dimensional (3D) structure has a significant impact on the antibodies raised for both systemic and orally administered allergens. A remarkable difference in the antibody binding patterns against linear and conformational epitope was seen between the allergens, indicating that the structural characteristics of proteins may heavily affect the induced antibody response.

Exposure to food allergens through inflamed skin promotes intestinal food allergy through the thymic stromal lymphopoietin-basophil axis

BACKGROUND

Exposure to food allergens through a disrupted skin barrier has been recognized as a potential factor in the increasing prevalence of food allergy.

OBJECTIVE

We sought to test the immunologic mechanisms by which epicutaneous sensitization to food allergens predisposes to intestinal food allergy.

METHODS

Mice were epicutaneously sensitized with ovalbumin or peanut on an atopic dermatitis-like skin lesion, followed by intragastric antigen challenge. Antigen-specific serum IgE levels and T(H)2 cytokine responses were measured by ELISA. Expression of type 2 cytokines and mast cell proteases in the intestine were measured by using real-time PCR. Accumulation of basophils in the skin and mast cells in the intestine was examined by using flow cytometry. In vivo basophil depletion was achieved by using diphtheria toxin treatment of Baso-DTR mice. For cell-transfer studies, the basophil population was expanded in vivo by means of hydrodynamic tail vein injection of thymic stromal lymphopoietin (TSLP) cDNA plasmid.

RESULTS

Sensitization to food allergens through an atopic dermatitis-like skin lesion is associated with an expansion of TSLP-elicited basophils in the skin that promote antigen-specific T(H)2 cytokine responses, increased antigen-specific serum IgE levels, and accumulation of mast cells in the intestine, promoting the development of intestinal food allergy. Critically, disruption of TSLP responses or depletion of basophils reduced the susceptibility to intestinal food allergy, whereas transfer of TSLP-elicited basophils into intact skin promoted disease.

CONCLUSION

Epicutaneous sensitization on a disrupted skin barrier is associated with accumulation of TSLP-elicited basophils, which are necessary and sufficient to promote antigen-induced intestinal food allergy.

Fungi: the neglected allergenic sources

Allergic diseases are considered the epidemics of the twentieth century estimated to affect more than 30% of the population in industrialized countries with a still increasing incidence. During the past two decades, the application of molecular biology allowed cloning, production and characterization of hundreds of recombinant allergens. In turn, knowledge about molecular, chemical and biologically relevant allergens contributed to increase our understanding of the mechanisms underlying IgE-mediated type I hypersensitivity reactions. It has been largely demonstrated that fungi are potent sources of allergenic molecules covering a vast variety of molecular structures including enzymes, toxins, cell wall components and phylogenetically highly conserved cross-reactive proteins. Despite the large knowledge accumulated and the compelling evidence for an involvement of fungal allergens in the pathophysiology of allergic diseases, fungi as a prominent source of allergens are still largely neglected in basic research as well as in clinical practice. This review aims to highlight the impact of fungal allergens with focus on asthma and atopic dermatitis.

Immunotherapy - risk/benefit in food allergy

Food allergy is a growing health concern in the westernized world with approx. 6% of children suffering from it. A lack of approved treatment has led to strict avoidance of the culprit food proteins being the only standard of care. Nowadays in-depth research is conducted to evaluate the possible use of allergen-specific immunotherapy (SIT) as an active therapeutic option for food allergy. Various routes of administration for the immunotherapy are investigated, including subcutaneous, oral, sublingual, and epicutaneous, and some appear to be successful in inducing a temporary tolerant state. Most research has been conducted with oral immunotherapy due to its efficacious and relatively safe profile. Increasing interest is dedicated to safer and more convenient approaches, such as sublingual and epicutaneous SIT; however, doubts exist about their possible capacity to induce temporary tolerant state and permanent oral tolerance. The high frequency of allergic adverse reactions of the various approaches and the inability to achieve permanent oral tolerance have highlighted the need of refinements in the strategies. A promising strategy for preventing IgE cross-linking and thus enhancing safety of SIT, while still activating T cells, is the use of tolerogenic peptides. The implementation of such an immunotherapy approach has the potential of not only increasing the chance of achieving a permanent state of tolerance, but also improving the safety and tolerability of the therapy. Immunotherapy for food allergy is still not ready for the clinic, but current and upcoming studies are dedicated to collect enough evidence for the possible implementation of allergen-SIT as a standard treatment for food allergy.

Regulation of intestinal epithelial permeability by tight junctions

The gastrointestinal epithelium forms the boundary between the body and external environment. It effectively provides a selective permeable barrier that limits the permeation of luminal noxious molecules, such as pathogens, toxins, and antigens, while allowing the appropriate absorption of nutrients and water. This selective permeable barrier is achieved by intercellular tight junction (TJ) structures, which regulate paracellular permeability. Disruption of the intestinal TJ barrier, followed by permeation of luminal noxious molecules, induces a perturbation of the mucosal immune system and inflammation, and can act as a trigger for the development of intestinal and systemic diseases. In this context, much effort has been taken to understand the roles of extracellular factors, including cytokines, pathogens, and food factors, for the regulation of the intestinal TJ barrier. Here, I discuss the regulation of the intestinal TJ barrier together with its implications for the pathogenesis of diseases.

Oral immunotherapy for milk allergy

BACKGROUND

The mainstay of treatment of IgE-mediated cow milk allergy (IMCMA) is an avoidance diet, which is especially difficult with a ubiquitous food like milk. Milk oral immunotherapy (MOIT) may be an alternative treatment, through desensitization or induction of tolerance.

OBJECTIVES

We aim to assess the clinical efficacy and safety of MOIT in children and adults with IMCMA as compared to a placebo treatment or avoidance strategy.

SEARCH METHODS

We searched 13 databases for journal articles, conference proceedings, theses and unpublished trials, without language or date restrictions, using a combination of subject headings and text words. The search is up-to-date as of October 1, 2012.

SELECTION CRITERIA

Only randomised controlled trials (RCT) were considered for inclusion. Blinded and open trial designs were included. Children and adults with IMCMA were included. MOIT administered by any protocol were included.

DATA COLLECTION AND ANALYSIS

A total of 2111 unique records were identified and screened for potential inclusion. Studies were selected, data extracted and methodological quality assessed independently by two reviewers. We attempted to contact the study investigators to inquire about data not published that was required for the analysis. Statistical heterogeneity was assessed using the I² test. We estimated a pooled risk ratio (RR) for each outcome using a Mantel-Haenzel fixed-effect model if statistical heterogeneity was low as evaluated by an I² value less than 50%.

MAIN RESULTS

Of 157 records reviewed, 16 were included, representing five trials. In general, the studies were small and had inconsistent methodological rigor. Overall, the quality of evidence was rated as low. Each study used a different MOIT protocol. A total of 196 patients were studied (106 MOIT, 90 control) and all were children. Three studies were blinded and two used an avoidance diet control.  Sixty-six patients (62%) in the MOIT group were able to tolerate a full serving of milk (about 200 mL) compared to seven (8%) of the control group (RR 6.61, 95% CI 3.51 to 12.44). In addition, 27 (25%) in the MOIT group could ingest a partial serving of milk (10 to 184 mL) while none could in the control group (RR 9.34, 95% CI 2.72 to 32.09). None of the studies assessed the patients following a period off immunotherapy. Adverse reactions were common (97 of 106 MOIT patients had at least one symptom), although most were local and mild. Because of variability in reporting methods, adverse effects could not be combined quantitatively. For every 11 patients receiving MOIT, one required intramuscular epinephrine. One patient required it on two occasions.

AUTHORS' CONCLUSIONS

Studies to date have involved small numbers of patients and the quality of evidence is generally low. The current evidence shows that MOIT can lead to desensitization in the majority of individuals with IMCMA although the development of long-term tolerance has not been established. A major drawback of MOIT is the frequency of adverse effects, although most are mild and self-limited. The use of parenteral epinephrine is not infrequent. Because there are no standardized protocols, guidelines would be required prior to incorporating desensitization into clinical practice.

Elevated antigen-driven IL-9 responses are prominent in peanut allergic humans

Food allergies, and peanut allergy in particular, are leading causes of anaphylactic fatalities worldwide. The immune mechanisms that underlie food allergy remain ill-defined and controversial, in part because studies in humans typically focus on analysis of a limited number of prototypical Th1/Th2 cytokines. Here we determine the kinetics and prevalence of a broad panel of peanut-driven cytokine and chemokine responses in humans with current peanut allergy vs those with stable, naturally occurring clinical tolerance to peanut. Our primary focus is identification of novel indicators of immune dysregulation. Antigen-specific cytokine mRNA and protein responses were elicited in primary culture via peanut or irrelevant antigen (Leishmania extract, milk antigens) mediated stimulation of fresh peripheral blood cells from 40 individuals. Peanut extract exposure in vitro induced a broad panel of responses associated with Th2/Th9-like, Th1-like and Th17-like immunity. Peanut-dependent Type 2 cytokine responses were frequently found in both peanut allergic individuals and those who exhibit clinical tolerance to peanut ingestion. Among Th2/Th9-associated cytokines, IL-9 responses discriminated between allergic and clinically tolerant populations better than did commonly used IL-4, IL-5 or IL-13 responses. Comparison with responses evoked by unrelated control antigen-mediated stimulation showed that these differences are antigen-dependent and allergen-specific. Conversely, the intensity of IL-12, IL-17, IL-23 and IFN-γ production was indistinguishable in peanut allergic and peanut tolerant populations. In summary, the ability to generate and maintain cytokine responses to peanut is not inherently distinct between allergic and peanut tolerant humans. Quantitative differences in the intensity of cytokine production better reflects clinical phenotype, with optimally useful indicators being IL-9, IL-5, IL-13 and IL-4. Equivalent, and minimal, Ag-dependent pro-inflammatory cytokine levels in both healthy and peanut allergic volunteers argues against a key role for such cytokines in maintenance of clinical tolerance to food antigens in humans.

In search of a tolerance-induction strategy for cow's milk allergies: significant reduction of beta-lactoglobulin allergenicity via transglutaminase/cysteine polymerization

OBJECTIVE

To explore the use of β-lactoglobulin polymerized using microbial transglutaminase and heating to identify whether protein polymerization could reduce in vivo allergenicity and maintain in vitro and ex vivo immunoreactivity for use in tolerance-induction protocols.

METHODS

Based on previous protocols applied in mice and children, we performed in vivo challenges (using a skin prick test) with native and polymerized β-lactoglobulin in adult patients with an IgE-mediated allergy to plactoglobulin. In vitro humoral immunoreactivity was analyzed using immunoblotting. Cell-mediated immunoreactivity was analyzed using ex vivo challenges with native and polymerized β-lactoglobulin and monitored by leukocyte adherence inhibition tests.

RESULTS

The skin tests demonstrated that there was a significant reduction in immediate cutaneous reactivity after polymerization. Polymerization did not decrease the immunoblotting detection of s-IgE specific to β-lactoglobulin. Cell-mediated immunoreactivity, as assessed by ex vivo challenges and leukocyte adherence inhibition tests, did not exhibit significant differences between leukocytes challenged with native versus polymerized β-lactoglobulin.

CONCLUSIONS

The polymerization of β-lactoglobulin decreased in vivo allergenicity and did not decrease in vitro humoral or ex vivo cell-mediated immunoreactivity. Therefore, we conclude that inducing polymerization using transglutaminase represents a promising technique to produce suitable molecules for the purpose of designing oral/ sublingual tolerance induction protocols for the treatment of allergies.