Pathogenesis of food allergy in the pediatric patient

Natural immunomodulating substances used for alleviating food allergy

Food allergy is a serious health problem affecting more than 10% of the human population worldwide. Medical treatments for food allergy remain limited because immune therapy is risky and costly, and anti-allergic drugs have many harmful side effects and can cause drug dependence. In this paper, we review natural bioactive substances capable of alleviating food allergy. The sources of the anti-allergic substances reviewed include plants, animals, and microbes, and the types of substances include polysaccharides, oligosaccharides, polyphenols, phycocyanin, polyunsaturated fatty acids, flavonoids, terpenoids, quinones, alkaloids, phenylpropanoids, and probiotics. We describe five mechanisms involved in anti-allergic activities, including binding with epitopes located in allergens, affecting the gut microbiota, influencing intestinal epithelial cells, altering antigen presentation and T cell differentiation, and inhibiting the degranulation of effector cells. In the discussion, we present the limitations of existing researches as well as promising advances in the development of anti-allergic foods and/or immunomodulating food ingredients that can effectively prevent or alleviate food allergy. This review provides a reference for further research on anti-allergic materials and their hyposensitizing mechanisms.

The Diagnosis and Management of Allergic Reactions Caused by Chinese Materia Medica

Traditional Chinese medicines (TCM) have been used in China for thousands of years. Although TCM has been generally perceived to be safe, adverse reactions to Chinese materia medica (CMM) have been reported. Most of the adverse reactions are allergic in nature, but other mechanisms may play a role. This review focuses on the mechanism and clinical presentation of these allergic reactions. Allergic reactions can occur as a result of the active and inactive ingredients of CMM. Impurities and chemicals generated during the production process can also lead to allergic or adverse reactions. Environmental factors such as temperature, humidity, and light can cause changes in the allergenicity of drugs. Human error in formulating CMM drugs also contributes to adverse drug reactions. The management of allergic reactions to CMM includes taking a good history, avoidance of medications in the same class as those which caused prior reactions, the proper training of staff, adherence to manufacturer guidelines and expiration dates, evaluation of benefit and risk balance, and the formulation of a risk management strategy for the use of CMM. A small test dose of a considered drug before using, improvements in drug purification technology, and proper storage and clinical administration help reduce allergic reactions due to CMM.

Short-chain fatty acids as a target for prevention against food allergy by regulatory T cells

Objective

Food allergy (FA) has become a public health issue of global concern. Short-chain fatty acids (SCFAs) are one of the most important biomarkers of intestinal metabolites. SCFAs may affect the occurrence and development of FA. Currently, no studies have been reported on the mechanism of FA in response to SCFAs. In this study, the common food allergen ovalbumin (OVA) was used for intestinal sensitization in Balb/c mice to study the effect of FA on intestinal barrier function and regulatory T cells in mice, thus providing a new target for the prevention and treatment of FA.

Methods

Twenty BALB/c mice were randomly divided into the experimental group and control group. The experimental group was given OVA, and the control group was given an equal amount of physiological saline. On the 31st day of modeling, the levels of secretory immunoglobulin A (sIgA) and serum total IgE and diamine oxidase (DAO) were determined using enzyme linked immunosorbent assay (ELISA). At the same time, after in vitro stimulation with different concentrations of SCFAs and histone acetylase inhibitor trichostatin A (TSA), the frequency and function of Treg in OVA-sensitized mice were detected by flow cytometry.

Results

Different concentrations of SCFAs and TSA selectively proliferate Treg cells in a dose-dependent manner. SCFAs and TSA-pretreated PBMCs that were injected intravenously into the OVA-sensitized mice through the tail vein can significantly reduce the expression of IgE, DAO, and sIgA.

Conclusion

SCFAs and TSA can selectively proliferate Tregs and upregulate the expression of anti-inflammatory cytokines, thereby suppressing allergic reactions.

Peanut gastrointestinal delivery oral immunotherapy in adolescents: Results of the build-up phase of a randomized, double-blind, placebo-controlled trial (PITA study)

BACKGROUND

Oral immunotherapy to peanut is effective in desensitizing patients but has significant side effects including anaphylaxis and gastrointestinal symptoms. In most protocols, peanut is administered in a vehicle food.

OBJECTIVE

In an exclusively adolescent population, we tested a new approach using sealed capsules of peanut (gastrointestinal delivery oral immunotherapy or GIDOIT) to bypass the upper gastrointestinal tract. The primary aim was to assess the efficacy of the oral build-up phase of GIDOIT and the secondary aim to analyse its safety.

METHODS

Adolescents with a history of a clinical allergic reaction after peanut ingestion were included in a 2-armed, parallel-design, individually randomized, double-blind, placebo-controlled, multicentre trial after a positive double-blind placebo-controlled oral food challenge (DBPCFC1). A central randomization centre used computer-generated tables to allocate treatments. Peanut (or placebo) capsules were ingested daily over a period of 24 weeks with increments every 2 weeks from 2 to 400 mg of peanut protein (pp). Primary outcome was tolerance of 400 mg of pp at DBPCFC2.

RESULTS

Thirty patients were included between September 2013 and May 2014. At DBPCFC2, unresponsiveness to 400 mg of pp was achieved in 17/21 peanut group patients (2 withdrawn patients) and 1/9 in the placebo group (Intention-to-treat analysis, P < .001, absolute difference = 0.7, 95%IC 0.43 0.96). Oropharyngeal symptoms were equally frequent in both groups. No dysphagia or other signs of eosinophilic oesophagitis occurred. Digestive adverse events (AE) were more frequent in the treated group (P = .02), but mild and without compliance issues. Only one severe advent event led to withdrawal in a patient who ingested twice the investigated treatment. Peanut-specific humoral immune responses were modulated.

CONCLUSION

The GIDOIT protocol demonstrated clinical and immunological efficacy and had an acceptable level of safety with weak oropharyngeal symptoms, no dysphagia, mild digestive events and few severe systemic AE.

Patterns of allergen sensitization and self-reported allergic disease in parents of food allergic children

BACKGROUND

Sensitization in adults has not been extensively studied.

OBJECTIVE

To investigate patterns of allergen sensitization in parents of food allergic children and to compare self-report of allergic disease with specific IgE (sIgE) measurements.

METHODS

A total of 1,252 mothers and 1,225 fathers of food allergic children answered standardized questionnaires about demographics, home environment, history of atopic diseases, and food allergy. Skin prick testing and sIgE serum tests were performed to 9 foods and 5 aeroallergens.

RESULTS

A total of 66.1% of parents were sensitized to either a food or aeroallergen. Mean sIgE levels were low for all foods tested. A total of 14.5% of mothers and 12.7% of fathers reported current food allergy. Only 28.4% had sensitization to their reported allergen. Fathers had significantly higher rates of sensitization to both foods and aeroallergens (P < .01) than mothers. Logistic regression evaluating predictors of self-reported food allergy revealed statistically significant positive associations in fathers with self-reported asthma, environmental allergy, and eczema. For mothers, significant positive associations were found with environmental allergy and having more than 1 food allergic child.

CONCLUSION

This cohort of parents of food allergic children found higher rates of sensitization to foods and aeroallergens compared with the general population. However, food sIgE levels were low and correlated poorly with self-reported food allergy. Sex differences in sensitization to foods and aeroallergens were seen.

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.

Food allergy diagnosis and therapy: where are we now?

Food allergy is a growing worldwide epidemic that adversely effects up to 10% of the population. Causes and risk factors remain unclear and diagnostic methods are imprecise. There is currently no accepted treatment for food allergy. Therefore, there is an imminent need for greater understanding of food allergies, revised diagnostics and development of safe, effective therapies. Oral immunotherapy provides a particularly promising avenue, but is still highly experimental and not ready for clinical use.

Food components and the immune system: from tonic agents to allergens

The intestinal mucosa is the major site of contact with antigens, and it houses the largest lymphoid tissue in the body. In physiological conditions, microbiota and dietary antigens are the natural sources of stimulation for the gut-associated lymphoid tissues (GALT) and for the immune system as a whole. Germ-free models have provided some insights on the immunological role of gut antigens. However, most of the GALT is not located in the large intestine, where gut microbiota is prominent. It is concentrated in the small intestine where protein absorption takes place. In this review, we will address the involvement of food components in the development and the function of the immune system. Studies in mice have already shown that dietary proteins are critical elements for the developmental shift of the immature neonatal immune profile into a fully developed immune system. The immunological effects of other food components (such as vitamins and lipids) will also be addressed. Most of the cells in the GALT are activated and local pro-inflammatory mediators are abundant. Regulatory elements are known to provide a delicate yet robust balance that maintains gut homeostasis. Usually antigenic contact in the gut induces two major immune responses, oral tolerance and production of secretory IgA. However, under pathological conditions mucosal homeostasis is disturbed resulting in inflammatory reactions such as food hypersensitivity. Food allergy development depends on many factors such as genetic predisposition, biochemical features of allergens, and a growing array of environmental elements. Neuroimmune interactions are also implicated in food allergy and they are examples of the high complexity of the phenomenon. Recent findings on the gut circuits triggered by food components will be reviewed to show that, far beyond their role as nutrients, they are critical players in the operation of the immune system in health and disease.