Oral tolerance and allergy.

Food allergy prevalence is increasing in the developed world. It's estimated that each year in the US, anaphylaxis to food results in 30,000 emergency room visits and 150 deaths. Over the past few decades, there has been a tremendous effort to better understand the pathogenesis of food allergy and mechanisms of food tolerance. In this article we review the structural of the gastrointestinal immune system and mechanisms of natural tolerance to food. We then review the factors that may result in the IgE mediated hypersensitivity reaction to food allergens resulting in clinical food allergy. Lastly, we provide a brief review of the efforts to induce immune tolerance to patients with food allergy.

Emerging Approaches to Food Desensitization in Children.

PURPOSE OF REVIEW: The purpose of this review is to highlight the recent advances in food desensitization in children with food allergy. RECENT FINDINGS: Recent advancements in epicutaneous, sublingual, and oral immunotherapy for food allergy in the future may offer children with food allergy and their families a viable option to reduce risk or severity of anaphylaxis with phase III trials ongoing for two of these treatment modalities. Food allergy prevalence in children is estimated to be up to 8%. These children are at risk of significant allergic reactions and anaphylaxis. Food avoidance and use of antihistamines or epinephrine has been the standard of care for these patients. This approach also has a significant socioeconomic effects on patients and their families. Recent advancements in understanding food allergy have allowed for exploring new methods of treatment. There is an increasing interest in oral immunotherapy, epicutaneous immunotherapy, or sublingual immunotherapy for food allergy. There have been also innovative approaches to immunotherapy by modification of food allergens (to make them less allergenic while maintain their immunogenicity) or adding adjunctive treatments (probiotics, anti-IgE, etc.) to increase efficacy or safety.

Early-life gut microbiome composition and milk allergy resolution.

BACKGROUND: Gut microbiota may play a role in the natural history of cow's milk allergy. OBJECTIVE: We sought to examine the association between early-life gut microbiota and the resolution of cow's milk allergy. METHODS: We studied 226 children with milk allergy who were enrolled at infancy in the Consortium of Food Allergy observational study of food allergy. Fecal samples were collected at age 3 to 16 months, and the children were followed longitudinally with clinical evaluation, milk-specific IgE levels, and milk skin prick test performed at enrollment, 6 months, 12 months, and yearly thereafter up until age 8 years. Gut microbiome was profiled by 16s rRNA sequencing and microbiome analyses performed using Quantitative Insights into Microbial Ecology (QIIME), Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt), and Statistical Analysis of Metagenomic Profiles (STAMP). RESULTS: Milk allergy resolved by age 8 years in 128 (56.6%) of the 226 children. Gut microbiome composition at age 3 to 6 months was associated with milk allergy resolution by age 8 years (PERMANOVA P = .047), with enrichment of Clostridia and Firmicutes in the infant gut microbiome of subjects whose milk allergy resolved. Metagenome functional prediction supported decreased fatty acid metabolism in the gut microbiome of subjects whose milk allergy resolved (η2 = 0.43; ANOVA P = .034). CONCLUSIONS: Early infancy is a window during which gut microbiota may shape food allergy outcomes in childhood. Bacterial taxa within Clostridia and Firmicutes could be studied as probiotic candidates for milk allergy therapy.

Administration of a probiotic with peanut oral immunotherapy: A randomized trial.

BACKGROUND: Coadministration of a bacterial adjuvant with oral immunotherapy (OIT) has been suggested as a potential treatment for food allergy. OBJECTIVE: To evaluate a combined therapy comprising a probiotic together with peanut OIT. METHODS: We performed a double-blind, placebo-controlled randomized trial of the probiotic Lactobacillus rhamnosus CGMCC 1.3724 and peanut OIT (probiotic and peanut oral immunotherapy [PPOIT]) in children (1-10 years) with peanut allergy. The primary outcome was induction of sustained unresponsiveness 2 to 5 weeks after discontinuation of treatment (referred to as possible sustained unresponsiveness). Secondary outcomes were desensitization, peanut skin prick test, and specific IgE and specific IgG4 measurements. RESULTS: Sixty-two children were randomized and stratified by age (≤5 and >5 years) and peanut skin test wheal size (≤10 and >10 mm); 56 reached the trial's end. Baseline demographics were similar across groups. Possible sustained unresponsiveness was achieved in 82.1% receiving PPOIT and 3.6% receiving placebo (P < .001). Nine children need to be treated for 7 to achieve sustained unresponsiveness (number needed to treat, 1.27; 95% CI, 1.06-1.59). Of the subjects, 89.7% receiving PPOIT and 7.1% receiving placebo were desensitized (P < .001). PPOIT was associated with reduced peanut skin prick test responses and peanut-specific IgE levels and increased peanut-specific IgG4 levels (all P < .001). PPOIT-treated participants reported a greater number of adverse events, mostly with maintenance home dosing. CONCLUSION: This is the first randomized placebo-controlled trial evaluating the novel coadministration of a probiotic and peanut OIT and assessing sustained unresponsiveness in children with peanut allergy. PPOIT was effective in inducing possible sustained unresponsiveness and immune changes that suggest modulation of the peanut-specific immune response. Further work is required to confirm sustained unresponsiveness after a longer period of secondary peanut elimination and to clarify the relative contributions of probiotics versus OIT.

Atopic dermatitis increases the effect of exposure to peanut antigen in dust on peanut sensitization and likely peanut allergy.

BACKGROUND: History and severity of atopic dermatitis (AD) are risk factors for peanut allergy. Recent evidence suggests that children can become sensitized to food allergens through an impaired skin barrier. Household peanut consumption, which correlates strongly with peanut protein levels in household dust, is a risk factor for peanut allergy. OBJECTIVE: We sought to assess whether environmental peanut exposure (EPE) is a risk for peanut sensitization and allergy and whether markers of an impaired skin barrier modify this risk. METHODS: Peanut protein in household dust (in micrograms per gram) was assessed in highly atopic children (age, 3-15 months) recruited to the Consortium of Food Allergy Research Observational Study. History and severity of AD, peanut sensitization, and likely allergy (peanut-specific IgE, ≥5 kUA/mL) were assessed at recruitment into the Consortium of Food Allergy Research study. RESULTS: There was an exposure-response relationship between peanut protein levels in household dust and peanut skin prick test (SPT) sensitization and likely allergy. In the final multivariate model an increase in 4 log2 EPE units increased the odds of peanut SPT sensitization (1.71-fold; 95% CI, 1.13- to 2.59-fold; P = .01) and likely peanut allergy (PA; 2.10-fold; 95% CI, 1.20- to 3.67-fold; P < .01). The effect of EPE on peanut SPT sensitization was augmented in children with a history of AD (OR, 1.97; 95% CI, 1.26-3.09; P < .01) and augmented even further in children with a history of severe AD (OR, 2.41; 95% CI, 1.30-4.47; P < .01); the effect of EPE on PA was also augmented in children with a history of AD (OR, 2.34; 95% CI, 1.31-4.18; P < .01). CONCLUSION: Exposure to peanut antigen in dust through an impaired skin barrier in atopically inflamed skin is a plausible route for peanut SPT sensitization and PA.

Peanut allergens alter intestinal barrier permeability and tight junction localisation in Caco-2 cell cultures.

BACKGROUND/AIMS: Allergen absorption by epithelia may play an important role in downstream immune responses. Transport mechanisms that can bypass Peyer's patches include transcellular and paracellular transport. The capacity of an allergen to cross via these means can modulate downstream processing of the allergen by the immune system. The aim of this study was to investigate allergen-epithelial interactions of peanut allergens with the human intestinal epithelium. METHODS: We achieved this using the human Caco-2 cell culture model, exposed to crude peanut extract. Western and immunofluorescence analysis were used to identify the cellular and molecular changes of peanut extract on the intestinal epithelium. RESULTS: Following exposure of Caco-2 cells to peanut extract, binding of the peanut allergens Ara h 1 and Ara h 2 to the apical cellular membrane and transcytosis across the monolayers were observed. Additionally, the co-localisation of the transmembrane tight junction proteins occludin, JAM-A and claudin-1, with the intracellular adhesion protein ZO-1 was modified. CONCLUSION: Disruption of Caco-2 barrier integrity through tight junction disruption may enable movement of peanut proteins across the intestinal epithelium. This accounts for peanut's increased allergenicity, compared to other food allergens, and provides an explanation for the potency of peanut allergens in immune response elicitation.

Managing food allergy in childhood.

PURPOSE OF REVIEW: This study reviews the newest developments on experimental therapies for the treatment of food allergy. RECENT FINDINGS: Epitope studies and microarray technology promise to improve the accuracy of diagnostic testing and may allow the prediction of reaction severity and the likelihood of allergy resolution. The regular ingestion of small amounts of food in oral immunotherapy (OIT) has been shown to dramatically increase reaction thresholds. However, a subset of patients have developed significant gastrointestinal symptoms requiring discontinuation of the treatment. A similar treatment given sublingually has appeared safer than OIT, but has also shown a less robust effect. Ingestion of extensively heated foods seems to accelerate the natural resolution of milk and egg allergy. The injectable anti-IgE therapy omalizumab has been shown to benefit in conjunction with OIT and preliminary data has suggested that it may also be effective as monotherapy. The Chinese herbal formula FAHF-2 has been shown to suppress anaphylaxis from single and multiple food allergies in mice, and early human studies have shown that it is well tolerated. SUMMARY: Improved testing should allow more accurate diagnosis of food allergy. For these patients, treatments are on the horizon, but further studies are needed to determine long-term safety and efficacy.

Single-tree nut immunotherapy attenuates allergic reactions in mice with hypersensitivity to multiple tree nuts.

BACKGROUND: Allergic reactions to tree nuts are often severe and are outgrown in less than 10% of diagnosed patients. OBJECTIVES: To determine whether treatment of underlying tree nut sensitization will prevent allergic reactions to cross-reacting tree nuts and to determine the effects of single-tree nut immunotherapy on true multi-tree nut sensitization. METHODS: Cross-reactivity model: Cashew-sensitized mice underwent immunotherapy with cashew and were subsequently challenged with cashew and pistachio. Multisensitization model: Cashew plus walnut-sensitized mice were treated with cashew alone, walnut alone, or both cashew and walnut and then underwent challenges to cashew and walnut. Challenges were assessed on the basis of symptoms, changes in body temperature, and mouse mast cell protease-1 release. RESULTS: In the cross-reactivity model, cashew immunotherapy completely prevented allergic reactions on challenges with cashew or the cross-reactive pistachio. In the multisensitization model, mice with cashew plus walnut allergy were significantly protected from anaphylactic reactions on cashew challenge in both the cashew-alone and walnut-alone immunotherapy groups. Results from the walnut challenge demonstrated significantly decreased allergic responses in the walnut immunotherapy group, whereas mice in the cashew immunotherapy group experienced significantly lower symptoms. In the cross-reactivity model, immunotherapy effectively decreased IL-4 and IL-5 production and increased IL-12 relative to placebo while also inducing a 5-fold increase in specific IgG(1). CONCLUSION: Single-tree nut immunotherapy can effectively decrease allergic responses in both the cross-reactivity and multisensitization mouse models. Further studies are needed to determine which single-tree nut immunotherapies will be most effective for specific multi-tree nut allergy profiles.

Immunomodulatory gene therapy prevents antibody formation and lethal hypersensitivity reactions in murine pompe disease.

Infantile Pompe disease progresses to a lethal cardiomyopathy in absence of effective treatment. Enzyme-replacement therapy (ERT) with recombinant human acid alpha-glucosidase (rhGAA) has been effective in most patients with Pompe disease, but efficacy was reduced by high-titer antibody responses. Immunomodulatory gene therapy with a low dose adeno-associated virus (AAV) vector (2 x 10(10) particles) containing a liver-specific regulatory cassette significantly lowered immunoglobin G (IgG), IgG1, and IgE antibodies to GAA in Pompe disease mice, when compared with mock-treated mice (P < 0.05). AAV-LSPhGAApA had the same effect on GAA-antibody production whether it was given prior to, following, or simultaneously with the initial GAA injection. Mice given AAV-LSPhGAApA had significantly less decrease in body temperature (P < 0.001) and lower anaphylactic scores (P < 0.01) following the GAA challenge. Mouse mast cell protease-1 (MMCP-1) followed the pattern associated with hypersensitivity reactions (P < 0.05). Regulatory T cells (Treg) were demonstrated to play a role in the tolerance induced by gene therapy as depletion of Treg led to an increase in GAA-specific IgG (P < 0.001). Treg depleted mice were challenged with GAA and had significantly stronger allergic reactions than mice given gene therapy without subsequent Treg depletion (temperature: P < 0.01; symptoms: P < 0.05). Ubiquitous GAA expression failed to prevent antibody formation. Thus, immunomodulatory gene therapy could provide adjunctive therapy in lysosomal storage disorders treated by enzyme replacement.

Oral immunotherapy for food allergy.

PURPOSE OF REVIEW: Food allergy is a difficult clinical problem for which no disease-modifying therapy currently exists. RECENT FINDINGS: The daily administration of graded allergen doses through oral immunotherapy (OIT) is one promising experimental approach to the development of a clinically available treatment. Although the concept of oral immunologic tolerance is not new, OIT as a treatment for food allergy is innovative. Over the last few years, several groups of investigators have begun to demonstrate safety and varying degrees of efficacy and immune modulation in uncontrolled pilot studies of OIT. Rigorously designed trials are currently underway and important unanswered questions remain. SUMMARY: OIT for food allergy holds promise for patients with food allergy but additional research is necessary before this approach is ready for clinical use.

Expert panel report on a study of Splenda in male rats.

A recent study in rats investigated the retail sweetener product, Granulated SPLENDA No Calorie Sweetener (Splenda) (Abou-Donia et al., 2008. Splenda alters gut microflora and increases intestinal P-glycoprotein and cytochrome P-450 in male rats. J. Toxicol. Environ. Health A, 71, 1415-1429), which is composed of (by dry weight) maltodextrin ( approximately 99%) and sucralose ( approximately 1%). The investigators reported that Splenda increased body weight, decreased beneficial intestinal bacteria, and increased the expression of certain cytochrome P450 (CYP450) enzymes and the transporter protein, P-glycoprotein (P-gp), the latter of which was considered evidence that Splenda or sucralose might interfere with the absorption of nutrients and drugs. The investigators indicated that the reported changes were attributable to the sucralose present in the product tested. An Expert Panel conducted a rigorous evaluation of this study. In arriving at its conclusions, the Expert Panel considered the design and conduct of the study, its outcomes and the outcomes reported in other data available publicly. The Expert Panel found that the study was deficient in several critical areas and that its results cannot be interpreted as evidence that either Splenda, or sucralose, produced adverse effects in male rats, including effects on gastrointestinal microflora, body weight, CYP450 and P-gp activity, and nutrient and drug absorption. The study conclusions are not consistent with published literature and not supported by the data presented.

Hypoallergenicity and effects on growth and tolerance of a new amino acid-based formula with docosahexaenoic acid and arachidonic acid.

OBJECTIVE: In study 1, to compare the effect on growth in healthy infants of a new amino acid-based formula (AAF) and a control extensively hydrolyzed formula (EHF), with both docosahexaenoic acid (DHA) and arachidonic acid (ARA) at levels similar to those in human milk worldwide. In study 2, to evaluate the hypoallergenicity of this new AAF in infants and children with confirmed cow's milk allergy (CMA). STUDY DESIGN: In study 1, a total of 165 healthy, full-term, formula-fed infants randomly received the new AAF or control formula. Anthropometric measurements, tolerance, and adverse events were recorded throughout the study. Plasma amino acid profiles were evaluated in a subset of the infants. In study 2, the hypoallergenicity of the new AAF was evaluated in 32 infants and children using a double-blind, placebo-controlled food challenge; an open challenge; and a 7-day feeding. RESULTS: In study 1, overall growth, tolerance, and safety outcomes were similar in both groups. In study 2, 29 of the 32 subjects completed both challenges; no allergic reaction was seen in any of the 32 subjects. CONCLUSIONS: The new AAF with DHA and ARA at levels similar to those in human milk worldwide is hypoallergenic. It also is safe and supports growth in healthy, term infants.

Preliminary Development of the Food Allergy Coping and Emotions Questionnaires for Children, Adolescents, and Young People: Qualitative Analysis of Data on IgE-Mediated Food Allergy from Five Countries.

BACKGROUND: We have previously developed a food allergy-specific developmental model, that explained emotions and coping styles, among children aged 6 to 15years in Ireland. OBJECTIVE: The objective of this study was to investigate the usefulness of the developmental model in a large multicountry data set, including any mediators of coping style, and to use the findings to generate an item pool that will form the basis for 3 age-appropriate self-report questionnaires to measure coping and emotions. METHODS: We conducted deductive thematic analysis on secondary data from interviews with 274 participants aged 6 to 23 years, and 119 parents from Australia, Ireland, Italy, the UK, and the USA. Analysis was undertaken across the entire data set. RESULTS: The Food Allergy Coping and Emotions (FACE) model has 5 major themes: (1) experiences and emotions, (2) search for normality, (3) management and coping, (4) "external mediators," and (5) "internal mediators" (between emotions and coping). These themes were present across countries, but differed according to age. CONCLUSIONS: Early-life experiences provide the foundation for later cognitions and behaviors. The expanded FACE developmental model is useful in explaining emotions and coping styles across different age groups and countries. These data will also be used to generate an age-specific bank of items for the development of 3 (age-specific self-report, and parent proxy) questionnaires to assess emotions and coping in food allergy. Findings provide insight into how particular styles of coping develop and vary from patient to patient and may also guide clinician-patient communication and the development of individualized management strategies.

The skin microbiome: impact of modern environments on skin ecology, barrier integrity, and systemic immune programming.

Skin barrier structure and function is essential to human health. Hitherto unrecognized functions of epidermal keratinocytes show that the skin plays an important role in adapting whole-body physiology to changing environments, including the capacity to produce a wide variety of hormones, neurotransmitters and cytokine that can potentially influence whole-body states, and quite possibly, even emotions. Skin microbiota play an integral role in the maturation and homeostatic regulation of keratinocytes and host immune networks with systemic implications. As our primary interface with the external environment, the biodiversity of skin habitats is heavily influenced by the biodiversity of the ecosystems in which we reside. Thus, factors which alter the establishment and health of the skin microbiome have the potential to predispose to not only cutaneous disease, but also other inflammatory non-communicable diseases (NCDs). Indeed, disturbances of the stratum corneum have been noted in allergic diseases (eczema and food allergy), psoriasis, rosacea, acne vulgaris and with the skin aging process. The built environment, global biodiversity losses and declining nature relatedness are contributing to erosion of diversity at a micro-ecological level, including our own microbial habitats. This emphasises the importance of ecological perspectives in overcoming the factors that drive dysbiosis and the risk of inflammatory diseases across the life course.

Erratum to: Allergen immunotherapy for IgE-mediated food allergy: protocol for a systematic review.

[This corrects the article DOI: 10.1186/s13601-016-0113-z.].

Current developments in peanut allergy.

PURPOSE OF REVIEW: Peanut allergy is among the most serious, life-threatening food sensitivities, and recent studies indicate increasing prevalence, particularly among children. Our objective is to highlight recent advances in the immunology and treatment of peanut allergy. RECENT FINDINGS: Peanut sensitization may be both a Th1- and Th2-driven process, and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) may play a role in regulating the response intensity. Preliminary work shows that the food matrix is important in the immune response to peanut and that purified peanut allergens may have little intrinsic stimulatory capacity. Studies characterizing peanut allergens have revealed Ara h 1 and Ara h 2 as the most potent allergens, but Ara h 3 may be more allergenic than previously thought. There appears to be a relationship between the diversity of IgE-binding patterns and the severity of clinical symptoms. Multiple novel approaches to treatment are being investigated, which include traditional Chinese medicine, various forms of modified immunotherapy and the use of adjuvants in modified immunotherapy. SUMMARY: By understanding the immunologic response to peanut and the roles of the major peanut allergens, it may be possible to predict those at risk for severe reactions, prevent peanut sensitization and effectively treat those already sensitized.

Food allergy.

This article reviews the classification of food allergies, their prevalence, pathophysiology, diagnosis, treatment and prognosis.