Oral tolerance: lessons on treatment of food allergy

Food Allergy

PURPOSE OF REVIEW

The goal of this review is to present an updated summary of the natural history of major childhood and adult food allergies and report recent advances in potential treatments for food allergy.

RECENT FINDINGS

The most common childhood food allergies are typically outgrown by adolescence or adulthood. However, peanut/tree nut allergies appear to more commonly persist into adulthood. Adults can develop new IgE-mediated food allergies; the most common is oral allergy syndrome. There are multiple different approaches being tried as possible treatments for food allergy. The prevalence of food allergy appears to be increasing but the varied approaches to treatment are being actively pursued such that an approved modality may not be too far in the future.

Food Allergy

PURPOSE OF REVIEW

The goal of this review is to present an updated summary of the natural history of major childhood and adult food allergies and report recent advances in potential treatments for food allergy.

RECENT FINDINGS

The most common childhood food allergies are typically outgrown by adolescence or adulthood. However, peanut/tree nut allergies appear to more commonly persist into adulthood. Adults can develop new IgE-mediated food allergies; the most common is oral allergy syndrome. There are multiple different approaches being tried as possible treatments for food allergy. The prevalence of food allergy appears to be increasing but the varied approaches to treatment are being actively pursued such that an approved modality may not be too far in the future.

Peanut allergy

PURPOSE OF REVIEW

To highlight recent advances in management of peanut allergy.

RECENT FINDINGS

Peanut allergy presents during early childhood. The prevalence of peanut allergy in children in developed countries appears to be increasing. Several factors, such as peanut-specific or environmental, are hypothesized as contributing to increased prevalence. However, there is no consensus on this matter. Component-related diagnostic tests are being explored to characterize clinical sensitivity. Currently, the primary treatment includes avoidance of peanut and immediate treatment of anaphylaxis. Recent peanut oral immunotherapy (OIT) trials achieved successful desensitization to peanuts in study participants, which may benefit many patients. Newer prospective studies are exploring effects of early high-dose peanut protein introduction versus avoidance in high-risk infants and development of peanut tolerance [Learning Early About Peanut Allergy (LEAP) study]. Several other immunotherapeutic approaches are being investigated in animal models.

SUMMARY

There is no cure for peanut allergy. Peanut oral immunotherapy offers a potential treatment for desensitization.

Oral immunotherapy for food allergy in children

PURPOSE OF REVIEW

Food allergy is a common disease in childhood. Natural tolerance development is frequent, but some children with cow's milk or hen's egg allergy and the majority of children with peanut allergy will remain allergic until adulthood. Within the last several years, the usefulness of oral immunotherapy has been investigated in food allergic patients. This review covers the most recent findings.

RECENT FINDINGS

In cow's milk and hen's egg allergy, controlled trials have been conducted in children, showing that oral immunotherapy, in general, has been successful and safe. Moreover, rush protocols have been developed allowing desensitization in a short period of time. Although side effects are frequent, allergic reactions seem to be controllable by antihistamines, steroids, or epinephrine. For peanut allergy, the first results look promising and detailed data will be available shortly.

SUMMARY

Several studies have shown that oral immunotherapy is a promising approach, especially in patients with severe and persistent food allergy. Side effects are frequent but seem controllable. So far, treatment protocols have been performed in highly supervised research settings. Until more experience is gained from larger long-term studies, oral immunotherapy should not be tried in clinical practice settings.

Health, probiotics, and inflammation

Probiotic bacteria are normal inhabitants of microflora and may confer several benefits, including prevention against intestinal inflammation. However, the exact mode of action of probiotics is still largely unknown. The first line of defense against the entry of pathogens is represented by the gut membrane barrier and probiotics may prevent pathogen-induced membrane damage by inhibiting pathogen adhesion and maintaining the correct organization of the tight junction and cytoskeleton proteins. The gut immune system should not only protect the mucosa against pathogens, but also avoid hypersensitivity reactions to food proteins and normal microflora. Failure of induction or maintenance of oral tolerance has been postulated to be a cause of food allergy. Feeding probiotic bacteria may prevent or ameliorate the onset of allergic disease and the associated inflammatory reactions through mechanisms involving modulation of T regulatory cells. Breakdown in tolerance toward intestinal bacteria is a primary cause of inflammatory bowel disease. Recent studies have shown that probiotics may ameliorate experimental colitis in mice by inducing interleukin 10 and interleukin 10-dependent T regulatory cells. In this article, an update of the anti-inflammatory activity of different probiotics and of the more accredited mechanisms underlying such activities are reported.

New perspectives for use of native and engineered recombinant food proteins in treatment of food allergy

Food allergy has emerged as an important target for research on curative treatment and prevention, with most efforts focusing on peanut, cow's milk, and egg allergy. This article reviews the recent developments in the potential treatments for IgE-mediated food allergy using native and engineered recombinant food proteins.

Specific oral tolerance induction in food allergy

Specific oral tolerance in food allergy can be induced by oral administration of the offending food, starting with very low dosages, gradually increasing the daily dosage up to an amount equivalent to a usually relevant dose for daily intake, followed up by a daily maintenance dose. Unfortunately, the body of scientific evidence concerning specific oral tolerance induction (SOTI) is still rather poor. Following a couple of case reports, only a few studies on a limited number of patients including different allergens are available. So far, no placebo-controlled, long-term study has been published. Concerning the underlying immunological mechanism, a limited number of studies have reported on changes in antibody production, and more recently on the role of different T-cell populations. The individual pattern of clinical reaction during SOTI seems to vary considerably between patients and from allergen to allergen. Arguments in favour of SOTI are the safety for an inadvertent intake of the offending food and the increased quality of life. Arguments against SOTI are the necessity for a regular intake and possible long-term compliance problems. Indications to consider SOTI in the future might be (i) importance of the incriminated food for the individual nutritional regimen, (ii) avoidance of the corresponding food cannot be assured and (iii) persistent severe food allergy. However, before SOTI can be recommended for the daily praxis, more studies are warranted to clarify whether certain patients may profit from SOTI and to understand the underlying mechanism.