Oral immunotherapy for the treatment of food allergy

Food Allergen Immunotherapy in the Treatment of Patients with IgE-Mediated Food Allergy

The prevalence of allergic diseases, including food allergy, is increasing, especially in developed countries. Implementation of an elimination diet is not a sufficient therapeutic strategy in patients with food allergy, whose quality of life is significantly impaired. In recent years, new effective therapeutic strategies have been developed, such as the application of oral, sublingual, and epicutaneous immunotherapy. Oral immunotherapy is the most often applied strategy because of its effectiveness and ease of application, with an acceptable safety profile. The effectiveness of oral immunotherapy in patients with egg, cow's milk, and peanut allergy has been proven both in terms of raising of the threshold and the development of tolerance, and in some patients, the development of sustainable unresponsiveness. Although oral immunotherapy is an effective treatment for food allergy, several limitations, including a long duration and a significant rate of reported adverse events, reduces its success. Therefore, new therapeutic options, such as treatment with biologicals, either as combinations with food allergen immunotherapy or as monotherapy with the aim of improving the efficacy and safety of treatment, are being investigated.

Food oral immunotherapy: Any distinguishing factors predicting the need of anti-IgE?

Oral immunotherapy (OIT) has gained popularity recently for IgE-mediated food allergy. Omalizumab (OMZ) has been used in patients (10-20%) who have too severe/frequent allergic reactions (AR) to continue OIT, to reduce these reactions. In this study, it was aimed to compare two groups of patients who completed OIT with and without OMZ and to seek determinants predicting the need of this treatment. It was also aimed to share the clinical findings regarding the long-term use of OMZ and the withdrawal process. Forty-one patients were started OIT and 93% could be desensitized. Two groups were similar in means of demographic characteristics, and clinical and laboratory findings. The patients who needed OMZ during OIT had also lower reaction doses during oral challenge (p = 0.037). Higher AR rate in this group declined after starting OMZ (p < 0.001). The injection intervals of OMZ were gradually extended. Most patients were able to discontinue OMZ (81%). There were no severe reactions during drug withdrawal attempts. The low reaction thresholds during oral food challenge may give a clue about OMZ requirement during OIT. It may be an option to start the treatment before OIT if reaction was seen in the first few steps of the oral food challenge. For the sake of safety, extension of injection intervals should be preferred instead of abruptly stopping OMZ.

The Combination of Binding Avidity of Ovomucoid-Specific IgE Antibody and Specific IgG4 Antibody Can Predict Positive Outcomes of Oral Food Challenges during Stepwise Slow Oral Immunotherapy in Children with Hen's Egg Allergy

To increase the prediction accuracy of positive oral food challenge (OFC) outcomes during stepwise slow oral immunotherapy (SS-OIT) in children with a hen's egg (HE) allergy, we evaluated the predictive value of the combination of antigen-specific IgE (sIgE) with antigen binding avidity and sIgG4 values. Sixty-three children with HE allergy undergoing SS-OIT were subjected to repeated OFCs with HE. We measured the ovomucoid (OVM)-sIgE by ImmunoCAP or densely carboxylated protein (DCP) microarray, sIgG4 by DCP microarray, and the binding avidity of OVM-sIgE defined as the level of 1/IC₅₀ (nM) measured by competitive binding inhibition assays. The OFC was positive in 37 (59%) patients undergoing SS-OIT. Significant differences in DCP-OVM-sIgE, CAP-OVM-sIgE, I/IC₅₀, DCP-OVM-sIgG4, the multiplication products of DCP-OVM-sIgE, and the binding avidity of DCP-OVM-sIgE (DCP-OVM-sIgE/IC₅₀) and DCP-OVM-sIgE/sIgG4 were compared between the negative and positive groups (p < 0.01). Among them, the variable with the greatest area under the receiver operating characteristic curve was DCP-OVM-sIgE/IC₅₀ (0.84), followed by DCP-OVM-sIgE/sIgG4 (0.81). DCP-OVM-sIgE/IC₅₀ and DCP-OVM-sIgE/sIgG4 are potentially useful markers for the prediction of positive OFCs during HE-SS-OIT and may allow proper evaluation of the current allergic status in the healing process during HE-SS-OIT.

Mechanisms of desensitization with oral immunotherapy and epicutaneous immunotherapy

Background

Oral immunotherapy (OIT) and epicutaneous immunotherapy (EPIT) are emerging therapies for food allergy. With several recently published exploratory trials and randomized controlled clinical trials that support these procedures, there is a clear progress and interest toward making these treatment options available for allergist/immunologists and patients with food allergies entrusted to their care. However, there still remain many questions and concerns to be addressed before these procedures can be fully understood.

Objective

The purpose of the present report is to trace some of the important historical milestones in the development of OIT and EPIT that have contributed to their evolving clinical application to the treatment of food allergy, to describe some of the current understandings of the immunologic mechanisms by which these procedures elicit desensitization, and to provide some areas for future inquiry and research.

Methods

An extensive research was conducted in the medical literature data bases by applying terms such as food allergy, desensitization, tolerance, unresponsiveness, Treg cells, allergen immunotherapy (AIT), oral immunotherapy (OIT), and epicutaneous immunotherapy (EPIT).

Results

OIT and EPIT take their origins from AIT (also called desensitization), a procedure first reported for the treatment of hay fever over a 100 years ago in which slowly increasing doses of a specifically relevant allergen were administered until a maintenance dosage was achieved when the patient was free of symptoms. OIT and EPIT differ from AIT in certain aspects including the route of administration of the allergen as well as their relative shorter period of sustained unresponsiveness.

Conclusion

The origins and important historical landmarks that have been made in the field of food allergy immunotherapy are presented in the context of the immunologic mechanisms that contribute to the pathogenesis of these disorders. Although considerable progress has been made in recent years toward making these treatment options available for allergist/immunologists and patients with food allergies, there still remain many questions and concerns to be addressed before these procedures can be fully understood, which can be illuminated by future research.

Could Age and Oral Challenge Outcomes Identify High-Risk Patients During Cow's Milk Oral Immunotherapy?

Objective: Severe immunglobuline E (IgE)-mediated reactions during oral immunotherapy (OIT) are major obstacles to treatment. The present study aimed to evaluate and identify clinical and laboratory biomarkers of adverse events during OIT among children with cow's milk (CM) allergy. Study Design: Eighty-six children older than 36 months who had undergone OIT with milk were enrolled. Clinical data, oral food challenge (OFC) test results, and laboratory data were recorded retrospectively. Results: The median duration of the build-up phase of OIT was 19 weeks (min 10-max 40) and the duration of the maintenance phase was 86.5 (min 1-max 132) months. A total of 11,767 CM doses were administered during the build-up phase and adverse reactions were seen in 62 (73.8%) patients with reactions registered for 157 doses among 11,767 (1/75 doses). The number of reactions during the maintenance phase was 41 (47.6%) in 24 (27.9%) patients. There was a significant reduction in the number of reactions (P = 0.000) between the build-up phase and maintenance phase. Adverse reactions and anaphylaxis were higher for patients who had cough during OFC (P = 0.003, P = 0.002, respectively) during the build-up phase and also during the maintenance phase too (P = 0.000). Evaluation for all reactions and anaphylaxis (during build-up and maintenance) with Kaplan-Meier and Cox regression analysis showed class IV-VI of CM-specific immunoglobulin E (sIgE), casein-sIgE and cough during OFC were significantly associated with increased probability of reaction and anaphylaxis. Younger age at onset of OIT was associated with risk reduction (0.017). Conclusion: Laboratory data and reactions during the OFC (especially cough) can help to identify high-risk patients during OIT.

Eight tips for the implementation of the first licenced peanut allergy oral immunotherapy into clinical practice

BACKGROUND

Shared learnings from the early use of novel therapies can aid in their optimization. The recent introduction of peanut oral immunotherapy (peanut OIT; Palforzia [Peanut (Arachis hypogaea) Allergen Powder-dnfp]) for peanut allergy addresses a significant unmet need but also highlights the requirement for consideration of several factors by both prescribers and patients.

OBJECTIVE

To provide guidance for prescribers of licenced peanut OIT to facilitate treatment delivery and improve outcomes.

METHODS

Clinicians with experience of licenced peanut OIT (United States n = 6, United Kingdom n = 1) participated in a series of interviews and group discussions designed to elicit tips for successful implementation.

RESULTS

Clinicians identified 8 tips that were considered the most relevant, practical, and impactful for prescribers of Peanut (Arachis hypogaea) Allergen Powder-dnfp: (1) preparing to provide treatment, (2) assessing the medical indication for treatment and (3) shared decision making, (4) staff education, (5) establishing office processes, (6) managing patient expectations and using anticipatory guidance, (7) optimising adherence and (8) maintaining flexibility throughout the treatment process. In addition, a range of supporting materials (e.g., checklists and action plans) are provided.

CONCLUSION

The introduction of a novel therapy often requires healthcare providers to modify or adopt practices to effectively employ the treatment. The provision of guidance based upon early real-world experiences of licenced peanut OIT may help inform clinical practice and improve treatment outcomes.

Home-Based Peanut Oral Immunotherapy for Low-Risk Peanut-Allergic Preschoolers During the COVID-19 Pandemic and Beyond

The coronavirus disease 2019 (COVID-19) pandemic has led to the deprioritization of non-emergency services, such as oral food challenges and the initiation of oral immunotherapy (OIT) for food-allergic children. Recent studies have suggested that home-based peanut OIT could be a safe and effective option for low-risk peanut-allergic children. In the period between September 1, 2020, and January 31, 2021, nine preschoolers with a history of mild allergic reactions to peanut underwent home-based peanut OIT. Eight of them (88.9%) completed the build-up phase at home in 11–28 weeks, tolerating a daily maintenance dose of 320 mg peanut protein. During the build-up, six patients (75.0%) reported urticaria, three (33.3%) reported gastrointestinal tract symptoms, and one (14.3%) reported oral pruritis. None of the patients developed anaphylaxis, required epinephrine, or attended emergency services related to OIT. One or two virtual follow-up visits were completed per patient during the build-up phase. Our case series shows that home-based OIT could be offered to the low-risk preschoolers during the COVID-19 pandemic when non-emergency services are limited and could be considered beyond the pandemic, especially for the families living in the rural or remote areas that may otherwise be unable to access OIT.

Peanut allergy: Beyond the oral immunotherapy plateau

BACKGROUND

There are a lack of disease-modifying treatments for peanut allergy, which is lifelong in most instances. Oral immunotherapy has remained at the forefront of prospective treatments, though its efficacy is consistently undermined by the risk of adverse reactions and meager sustained effects.

AIM

This review discusses the current state of oral immunotherapy, its strengths and limitations, and the future of therapeutics for the treatment of peanut allergy.

CONCLUSION

The persistence of peanut allergy is currently attributed to reservoirs of peanut-specific memory B cells and Th2 cells, though the cellular and molecular interplay that facilitates the replenishment of peanut-specific IgE remains elusive. Uncovering these events will prove critical for identification of novel targets as we forge ahead to a new age of peanut allergy treatment with biotherapeutics.

Advancing Food Allergy Through Epidemiology: Understanding and Addressing Disparities in Food Allergy Management and Outcomes

Epidemiological studies have been pivotal in advancing understanding of the etiology of food allergy and in guiding the development of evidence-based guidelines for food allergy prevention and clinical management. In recent years, as research into the population-level distribution and determinants of food allergy has accumulated, data indicate that substantial differences in food allergy outcomes and management exist across racial/ethnic and other socioeconomic strata. This clinical commentary aims to provide a review of existing epidemiological studies and shed valuable light on the disparate burden of food allergy. Emerging methods to quantify environmental exposure and food allergy outcomes are detailed, as are specific areas in which future research is warranted. We also highlight the role that epidemiology plays in advancing health equity and provide a framework as to how it can effectively inform health policy at all phases of the policy cycle-from initial population health assessment to the evaluation and refinement of specific health policies (ie, national guidelines to promote earlier introduction of peanut-containing foods for allergy prevention).

Recent advances in mechanisms of food allergy and anaphylaxis

Food allergens are innocuous proteins that promote tolerogenic adaptive immune responses in healthy individuals yet in other individuals induce an allergic adaptive immune response characterized by the presence of antigen-specific immunoglobulin E and type-2 immune cells. The cellular and molecular processes that determine a tolerogenic versus non-tolerogenic immune response to dietary antigens are not fully elucidated. Recently, there have been advances in the identification of roles for microbial communities and anatomical sites of dietary antigen exposure and presentation that have provided new insights into the key regulatory steps in the tolerogenic versus non-tolerogenic decision-making processes. Herein, we will review and discuss recent findings in cellular and molecular processes underlying food sensitization and tolerance, immunological processes underlying severity of food-induced anaphylaxis, and insights obtained from immunotherapy trials.

IgE-Mediated Multimorbidities in Allergic Asthma and the Potential for Omalizumab Therapy

Allergic asthma often coexists with different pathological conditions, called multimorbidities, that are mostly of allergic nature and share a common underlying inflammatory pathophysiological mechanism. Multimorbidities of allergic asthma may influence asthma control, its severity, and patients' response to treatment, and contribute to the overall socioeconomic burden of the disease. Immunoglobulin E (IgE) is known to play a central role in the pathogenesis of various allergic diseases, including asthma. Thus, IgE-mediated immunologic pathways present an attractive target for intervention in asthma and multimorbidities. In this review, we discuss the most frequently reported IgE-mediated multimorbidities in allergic asthma, including allergic rhinitis, rhinoconjunctivitis, atopic dermatitis, vernal keratoconjunctivitis, chronic rhinosinusitis with nasal polyps, food allergies, and allergic bronchopulmonary aspergillosis. Omalizumab is a recombinant humanized monoclonal antibody against IgE and has been in use to treat allergic asthma for more than a decade. We comprehensively review the clinical evidence for omalizumab in the treatment of the aforementioned multimorbidities in allergic asthma.

The role of regulatory T cells in the acquisition of tolerance to food allergens in children

Food allergy is a pathological immune reaction that identifies certain harmless food proteins, usually tolerated by the majority of the people, as a threat. The prevalence of these food allergies is increasing worldwide and currently affects 8% of children. Exacerbated reactions to milk, egg and peanut are the most frequent in the pediatric population. It is well known that allergic diseases are a type 2 T-helper (Th2) immune response, characterized by the elevated production of IgE antibodies. However, little is known about the immune mechanisms responsible for the development of clinical tolerance toward food allergens. Recent studies have suggested the key role of regulatory T cells (Tregs) in controlling allergic inflammation. In this review, we discuss the importance of Tregs in the pathogenesis of food allergy and the acquisition of oral tolerance in children. Further investigation in this area will be crucial for the identification of predictive markers and the development of new therapies, which will represent a clinical and social benefit for these allergic diseases.

Dual Factors May Be Necessary for Development of Atopic March in Early Infancy

The incidence of atopic diseases, including atopic dermatitis (AD), food allergies, allergic rhinitis, and asthma, has increased in recent decades, and currently affects approximately 20% of the population. Atopic march is the development of AD in infancy and subsequent food allergies, allergic rhinitis, and asthma in later childhood. Patients with infantile eczema may develop typical symptoms of AD, allergic rhinitis, and asthma at certain ages. Some patients' symptoms persist for several years, whereas others may have resolution with aging. Development of these diseases is strongly influenced by the following two factors: skin dysfunction caused by filaggrin mutations and development of colonization of microflora in early infancy. Filaggrin mutations predisposing to asthma, allergic rhinitis, and allergic sensitization, only in the presence of AD, strongly support the role of filaggrin in the pathogenesis of AD and in subsequent progression of the atopic march. Several studies have shown that development of colonization of microflora in early infancy might affect development of allergic disease or food desensitization. Therefore, massive allergen exposure to genetic skin dysfunction in early infancy and an imbalance of microflora might be necessary for development of atopic march.

Update on oral immunotherapy for egg allergy

Oral immunotherapy (OIT) is an emerging treatment of IgE-mediated egg allergy. In the past decade, a multitude of studies have assessed the potential for egg OIT to induce clinical desensitization. The following review will evaluate the efficacy and safety of this therapy as determined by randomized controlled, non-randomized controlled and uncontrolled trials. Recent studies using reduced allergenic egg products and anti-IgE assisted therapy to improve egg OIT safety will also be discussed. Recent advances in the mechanisms underlying food OIT suggest that certain immune parameters may be helpful in monitoring response to therapy, including egg OIT. Although, egg OIT is consistently shown to be effective with regards to clinical desensitization, fewer studies have looked at persistent tolerance or sustained unresponsiveness. Limited results of long-term follow-up trials suggest that this therapy may have disease-modifying effects. In general, the comparison of studies is complicated by major differences in study designs, OIT protocols and endpoints.

Use of biologics in severe food allergies

PURPOSE OF REVIEW

Severe cases of food allergy account for the majority of the burden in terms of risks, quality of life, and resource expenditure. The traditional approach to these forms has been strict avoidance. More recently, Oral ImmunoTherapy (OIT) has gained a role in their management. However, in severe food allergies OIT is often infeasible.

RECENT FINDINGS

Case reports, observational, and prospective studies have recently proposed different approaches to severe food allergy. The majority of them include the use of biologics. Omalizumab has been the most studied drug for severe food allergies, and its role as adjuvant treatment to OIT is well established. Interest has been raised on other biologics, as dupilumab, reslizumab, and mepolizumab. Toll-like receptor agonists, and gene therapy using adeno-associated virus coding for Omalizumab are promising alternatives.

SUMMARY

The recent studies are deeply influencing the clinical practice. We review the modifications of the clinical approach to severe food allergies so far available. We indicate the possible evolutions of treatment with biologics in severe food allergies.

Antigen-specific Treg cells in immunological tolerance: implications for allergic diseases

Allergic diseases are chronic inflammatory disorders in which there is failure to mount effective tolerogenic immune responses to inciting allergens. The alarming rise in the prevalence of allergic diseases in recent decades has spurred investigations to elucidate the mechanisms of breakdown in tolerance in these disorders and means of restoring it. Tolerance to allergens is critically dependent on the generation of allergen-specific regulatory T (Treg) cells, which mediate a state of sustained non-responsiveness to the offending allergen. In this review, we summarize recent advances in our understanding of mechanisms governing the generation and function of allergen-specific Treg cells and their subversion in allergic diseases. We will also outline approaches to harness allergen-specific Treg cell responses to restore tolerance in these disorders.

Oral immunotherapy combined with omalizumab for high-risk cow's milk allergy: a randomized controlled trial

We evaluated the efficacy and safety of oral immunotherapy (OIT) combined with 24 weeks of omalizumab (OMB) at inducing desensitization in children with cow's milk allergy (CM) compared with an untreated group. The present study was a prospective randomized controlled trial. Sixteen patients (age, 6-14 years) with high IgE levels to CM were enrolled in the present study. Patients were randomized 1:1 to receive OMB-OIT group or untreated group. The primary outcome was the induction of desensitization at 8 weeks after OMB was discontinued in OMB-OIT treated group and at 32 weeks after study entry. None of the 6 children in the untreated group developed desensitization to CM while all of the 10 children in the OIT-OMB treated group achieved desensitization (P < 0.001). A significantly decreased wheal diameter in response to a skin prick test using CM was found in the OMB-OIT treated group (P < 0.05). These data suggest that OIT combined with OMB using microwave heated CM may help to induce desensitization for children with high-risk CM allergy. This prospective randomized controlled trial was intended for 50 participants but was prematurely discontinued due to overwhelming superiority of OMB combined with microwave heated OIT over CM avoidance.

Immunotherapy for cow's milk allergy

Oral immunotherapy (OIT) is used regularly for young children with cow's milk (CM) allergy and has been shown to be effective in several studies. However, adverse events occur frequently during OIT. Furthermore, there are only 5 randomized controlled trial studies of CM-OIT and these are low-powered single center trials. Therefore, evidence levels are also low and sometimes frequent and severe allergic events occur during the OIT. Furthermore, there are no standardized protocols in pediatric allergy guidelines from several countries and studies with long-term follow-up observations and clinical tolerance defined as sustained unresponsiveness are rare. Additionally, clinical tolerance by OIT is generally not well defined and obscure. Thus, several problems remain to be resolved, however we hope OIT in combination with omalizumab and less allergenic heated CM products will resolve these problems in the future.

Peanut-specific type 1 regulatory T cells induced in vitro from allergic subjects are functionally impaired

BACKGROUND

Peanut allergy (PA) is a life-threatening condition that lacks regulator-approved treatment. Regulatory T type 1 (T_R1) cells are potent suppressors of immune responses and can be induced in vivo upon repeated antigen exposure or in vitro by using tolerogenic dendritic cells. Whether oral immunotherapy (OIT) leads to antigen-specific T_R1 cell induction has not been established.

OBJECTIVES

We sought to determine whether peanut-specific T_R1 cells can be generated in vitro from peripheral blood of patients with PA at baseline or during OIT and whether they are functional compared with peanut-specific T_R1 cells induced from healthy control (HC) subjects.

METHODS

Tolerogenic dendritic cells were differentiated in the presence of IL-10 from PBMCs of patients with PA and HC subjects pulsed with the main peanut allergens of Arachis hypogaea, Ara h 1 and 2, and used as antigen-presenting cells for autologous CD4⁺ T cells (CD4⁺ T cells coincubated with tolerogenic dendritic cells pulsed with the main peanut allergens [pea-T10 cells]). Pea-T10 cells were characterized by the presence of CD49b⁺ lymphocyte-activation gene 3 (LAG3)⁺ T_R1 cells, antigen-specific proliferative responses, and cytokine production.

RESULTS

CD49b⁺LAG3⁺ T_R1 cells were induced in pea-T10 cells at comparable percentages from HC subjects and patients with PA. Despite their antigen specificity, pea-T10 cells of patients with PA with or without OIT, as compared with those of HC subjects, were not anergic and had high T_H2 cytokine production upon peanut-specific restimulation.

CONCLUSIONS

Peanut-specific T_R1 cells can be induced from HC subjects and patients with PA, but those from patients with PA are functionally defective independent of OIT. The unfavorable T_R1/T_H2 ratio is discussed as a possible cause of PA T_R1 cell impairment.

Critical role of intestinal interleukin-4 modulating regulatory T cells for desensitization, tolerance, and inflammation of food allergy

Background and objective

The mechanism inducing either inflammation or tolerance to orally administered food allergens remains unclear. To investigate this we analyzed mouse models of food allergy (OVA23-3) and tolerance (DO11.10 [D10]), both of which express ovalbumin (OVA)-specific T-cell receptors.

Methods

OVA23-3, recombination activating gene (RAG)-2-deficient OVA23-3 (R23-3), D10, and RAG-2-deficient D10 (RD10) mice consumed a diet containing egg white (EW diet) for 2–28 days. Interleukin (IL)-4 production by CD4⁺ T cells was measured as a causative factor of enteropathy, and anti-IL-4 antibody was used to reveal the role of Foxp3⁺ OVA-specific Tregs (aiTreg) in this process.

Results

Unlike OVA23-3 and R23-3 mice, D10 and RD10 mice did not develop enteropathy and weight loss on the EW diet. On days 7–10, in EW-fed D10 and RD10 mice, splenic CD4⁺ T cells produced significantly more IL-4 than did those in the mesenteric lymph nodes (MLNs); this is in contrast to the excessive IL-4 response in the MLNs of EW-fed OVA23-3 and R23-3 mice. EW-fed R23-3 mice had few aiTregs, whereas EW-fed RD10 mice had them in both tissues. Intravenous injections of anti-IL-4 antibody recovered the percentage of aiTregs in the MLNs of R23-3 mice. On day 28, in EW-fed OVA23-3 and R23-3 mice, expression of Foxp3 on CD4⁺ T cells corresponded with recovery from inflammation, but recurrence of weight loss was observed on restarting the EW diet after receiving the control-diet for 1 month. No recurrence developed in D10 mice.

Conclusions

Excessive IL-4 levels in the MLNs directly inhibited the induction of aiTregs and caused enteropathy. The aiTregs generated in the attenuation of T cell-dependent food allergic enteropathy may function differently than aiTregs induced in a tolerance model. Comparing the two models enables to investigate their aiTreg functions and to clarify differences between inflammation with subsequent desensitization versus tolerance.

Primary eosinophilic gastrointestinal disorders in children who have received food oral immunotherapy

BACKGROUND

Food oral immunotherapy (OIT) involves the administration of the food allergen causing the symptoms, in order to induce tolerance. Primary eosinophilic gastrointestinal disorders (PEGDs) are characterised by an eosinophil-rich inflammation affecting different locations of the digestive tract. We present a series of patients with PEGDs in a group of children following OIT with milk and/or egg.

MATERIAL AND METHODS

A prospective study during the period 2006-2014 was performed in paediatric patients subjected to OIT with milk and/or egg. When these children present persistent gastrointestinal symptoms, they are referred to the Paediatric Gastroenterology Unit for evaluation.

RESULTS

Primary eosinophilic gastrointestinal disorders were diagnosed in eight of the 128 cases of OIT (6.25%). The time to PEGDs development was variable: two cases showed symptoms during OIT, and the rest with a median time of 29 months (15-48 months). Food treatment discontinuation was not required in four of the five cases of eosinophilic oesophagitis, although food removal was necessary in patients with eosinophilic gastroenteritis.

CONCLUSIONS

We report the highest prevalence of PEGDs in children subjected to OIT, and the first cases of eosinophilic gastroenteritis following food OIT. The monitoring of new digestive signs and symptoms after OIT is crucial for the diagnosis of these disorders, and prolonged follow-up is required. The management of such patients and the need or not to eliminate the food should be assessed on an individualised basis, according to the severity of the condition, its evolution and response to different treatment alternatives.

Molecular and cellular mechanisms of food allergy and food tolerance

Ingestion of innocuous antigens, including food proteins, normally results in local and systemic immune nonresponsiveness in a process termed oral tolerance. Oral tolerance to food proteins is likely to be intimately linked to mechanisms that are responsible for gastrointestinal tolerance to large numbers of commensal microbes. Here we review our current understanding of the immune mechanisms responsible for oral tolerance and how perturbations in these mechanisms might promote the loss of oral tolerance and development of food allergies. Roles for the commensal microbiome in promoting oral tolerance and the association of intestinal dysbiosis with food allergy are discussed. Growing evidence supports cutaneous sensitization to food antigens as one possible mechanism leading to the failure to develop or loss of oral tolerance. A goal of immunotherapy for food allergies is to induce sustained desensitization or even true long-term oral tolerance to food allergens through mechanisms that might in part overlap with those associated with the development of natural oral tolerance.

New developments in immunotherapies for food allergy

Food allergy affects around 10% of the population. As the prevalence of food allergy continues to increase, disproportionately in children, new therapies for food allergy are being investigated. While there are no approved treatments for food allergy, immunotherapy facilitates significant desensitization and protection from accidental exposure. Nevertheless, current immunotherapies do not entirely nor permanently eliminate sensitivity to the food allergen. Since the rates of sustained unresponsiveness are significantly lower than desensitization, future therapies that enhance the rates of long-term tolerance in patients will catalyze progress in this field over the next 5–10 years.

Immune mechanisms of sublingual immunotherapy

Sublingual immunotherapy (SLIT) is a well-established allergen-specific immunotherapy and a safe and effective strategy to reorient inappropriate immune responses in allergic patients. SLIT takes advantage of the tolerogenic environment of the oral mucosa to promote tolerance to the allergen. Several clinical studies have investigated the complex interplay of innate and adaptive immune responses that SLIT exploits. The oral immune system is composed of tolerogenic dendritic cells that, following uptake of allergen during SLIT, support the differentiation of T helper cell type 1 (Th1) and the induction of IL-10-producing regulatory T cells. Following SLIT, allergic disease-promoting T helper cell type 2 (Th2) responses shift to a Th1 inflammatory response, and IL-10 and transforming growth factor (TGF)-β production by regulatory T cells and tolerogenic dendritic cells suppress allergen-specific T cell responses. These immune changes occur both in the sublingual mucosa and in the periphery of a patient following SLIT. SLIT also promotes the synthesis of allergen-specific IgG and IgA antibodies that block allergen-IgE complex formation and binding to inflammatory cells, thus encouraging an anti-inflammatory environment. Several of these revealing findings have also paved the way for the identification of biomarkers of the clinical efficacy of SLIT. This review presents the emerging elucidation of the immune mechanisms mediated by SLIT.