Association of allergen-specific regulatory T cells with the onset of clinical tolerance to milk protein

The role of allergen-specific regulatory T cells in the control of allergic disease

Allergies result from an antigen-specific loss of tolerance against innocuous foreign substances. Allergen immunotherapy (AIT) aims to reverse the pathogenic response and to re-establish physiological tolerance. However, the tolerogenic mechanisms that prevent allergy in healthy and act during AIT are still obscure. Foxp3 expressing 'regulatory' CD4 T cells (Tregs) are essential mediators of tolerance against allergens. It remains controversial which antigen specificity of Tregs is required to prevent allergy and the role of allergen-specific Tregs during AIT. Recent work provided precise insight into physiological T cell responses against environmental and food compounds. This identified Treg responses mainly against peptides and proteins not involved in immune pathology, revealing an unexpected role of Treg antigen specificity for tolerance. This review will focus on antigen-specific Treg responses against food and airborne allergens, and the impact of the technological approach utilized for antigen-specific Treg characterization is discussed, with critical points to be addressed in future research.

Maternal influences on offspring food allergy

The prevalence of allergies has been globally escalating. While allergies could appear at any age, they often develop in early life. However, the significant knowledge gap in the field is the mechanisms by which allergies affect certain people but not others. Investigating early factors and events in neonatal life that have a lasting impact on determining the susceptibilities of children to develop allergies is a significant area of the investigation as it promotes the understanding of neonatal immune system that mediates tolerance versus allergies. This review focuses on the research over the recent 10 years regarding the potential maternal factors that influence offspring allergies with a view to food allergy, a potentially life-threatening cause of anaphylaxis. The role of breast milk, maternal diet, maternal antibodies, and microbiota that have been suggested as key maternal factors regulating offspring allergies are discussed here. We also suggest future research area to expand our knowledge of maternal-offspring interactions on the pathogenesis of food allergy.

Contribution of T cell subsets to different food allergic diseases

Food allergies occur due to a lack of tolerance to the proteins found in foods. While IgE- and non-IgE-mediated food allergies have different clinical manifestations, epidemiology, pathophysiology, and management, they share dysregulated T cell responses. Recent studies have shed light on the contributions of different T cell subsets to the development and persistence of different food allergic diseases. This review discusses the role of T cells in both IgE- and non-IgE-mediated food allergies and considers the potential future investigations in this context.

Atopic dermatitis and IgE-mediated food allergy: Common biologic targets for therapy and prevention

OBJECTIVE

To highlight common mechanistic targets for the treatment of atopic dermatitis (AD) and IgE-mediated food allergy (IgE-FA) with potential to be effective for both diseases and prevent atopic progression.

DATA SOURCES

Data sources were PubMed searches or National Clinical Trials (NCT)-registered clinical trials related to AD, IgE-FA, and other atopic conditions, especially focused on the pediatric population.

STUDY SELECTIONS

Human seminal studies and/or articles published in the past decade were emphasized with reference to preclinical models when relevant. NCT-registered clinical trials were filtered by inclusion of pediatric subjects younger than 18 years with special focus on children younger than 12 years as a critical period when AD and IgE-FA diseases may often be concurrent.

RESULTS

AD and IgE-FA share several pathophysiologic features, including epithelial barrier dysfunction, innate and adaptive immune abnormalities, and microbial dysbiosis, which may be critical for the clinical progression between these diseases. Revolutionary advances in targeted biologic therapies have shown the benefit of inhibiting type 2 immune responses, using dupilumab (anti-interleukin-4Rα) or omalizumab (anti-IgE), to potentially reduce symptom burden for both diseases in pediatric populations. Although the potential for biologics to promote disease remission (AD) or sustained unresponsiveness (IgE-FA) remains unclear, the refinement of biomarkers to predict infants at risk for atopic disorders provides promise for prevention through timely intervention.

CONCLUSION

AD and IgE-FA exhibit common features that may be leveraged to develop biologic therapeutic strategies to treat both conditions and even prevent atopic progression. Future studies should be designed with consistent age stratification in the pediatric population and standardized regimens of adjuvant oral immunotherapy or dose escalation (IgE-FA) to improve cross-study interpretation.

The Role of Regulatory T Cells in Allergic Diseases: Collegium Internationale Allergologicum (CIA) Update 2024

BACKGROUND

Allergy represents a major health problem of increasing prevalence worldwide with a high socioeconomic impact. Our knowledge on the molecular mechanisms underlying allergic diseases and their treatments has significantly improved over the last years. The generation of allergen-specific regulatory T cells (Tregs) is crucial in the induction of healthy immune responses to allergens, preventing the development and worsening of allergic diseases.

SUMMARY

In the last decades, intensive research has focused on the study of the molecular mechanisms involved in Treg development and Treg-mediated suppression. These mechanisms are essential for the induction of sustained tolerance by allergen-specific immunotherapy (AIT) after treatment discontinuation. Compelling experimental evidence demonstrated altered suppressive capacity of Tregs in patients suffering from allergic rhinitis, allergic asthma, food allergy, or atopic dermatitis, as well as the restoration of their numbers and functionality after successful AIT.

KEY MESSAGE

The better understanding of the molecular mechanisms involved in Treg generation during allergen tolerance induction might well contribute to the development of novel strategies for the prevention and treatment of allergic diseases.

Phosphorylation of hnRNP A1-Serine 199 Is Not Required for T Cell Differentiation and Function

hnRNP A1 is an important RNA-binding protein that influences many stages of RNA processing, including transcription, alternative splicing, mRNA nuclear export, and RNA stability. However, the role of hnRNP A1 in immune cells, specifically CD4+ T cells, remains unclear. We previously showed that Akt phosphorylation of hnRNP A1 was dependent on TCR signal strength and was associated with Treg differentiation. To explore the impact of hnRNP A1 phosphorylation by Akt on CD4+ T cell differentiation, our laboratory generated a mutant mouse model, hnRNP A1-S199A (A1-MUT) in which the major Akt phosphorylation site on hnRNP A1 was mutated to alanine using CRISPR Cas9 technology. Immune profiling of A1-MUT mice revealed changes in the numbers of Tregs in the mesenteric lymph node. We found no significant differences in naive CD4+ T cell differentiation into Th1, Th2, Th17, or T regulatory cells (Tregs) in vitro. In vivo, Treg differentiation assays using OTII-A1-Mut CD4+ T cells exposed to OVA food revealed migration and homing defects in the A1-MUT but no change in Treg induction. A1-MUT mice were immunized with NP- keyhole limpet hemocyanin, and normal germinal center development, normal numbers of NP-specific B cells, and no change in Tfh numbers were observed. In conclusion, Akt phosphorylation of hnRNP A1 S199 does not play a role in CD4+ T cell fate or function in the models tested. This hnRNP A1-S199A mouse model should be a valuable tool to study the role of Akt phosphorylation of hnRNP A1-S199 in different cell types or other mouse models of human disease.

Natural course of IgE-mediated food allergy in children

The prevalence of food allergy and food-induced anaphylaxis in children is increasing worldwide. Cow's milk, hen's eggs, and wheat allergies in young children have a more favorable prognosis with a relatively early outgrow, while allergies to peanuts, tree nuts, and seafood are more likely to be persistent. Although our understanding of the mechanism underlying the resolution of food allergy is incomplete, the roles of dendritic cells, regulatory T cells, and regulatory B cells are important. Many past studies on the natural course of food allergy were retrospective analyses of specific study groups, but large-scale population-based prospective studies are now being published. This review summarizes recent studies of the natural course of cow's milk, hen's eggs, wheat, peanuts, tree nuts, soy, sesame, and seafood allergies. The potential factors affecting the natural course of food allergy include symptom severity on ingestion, age at diagnosis, allergic comorbidities, skin prick test reaction size or serum food-specific immunoglobulin (Ig) E levels, changes in sensitization degree, IgE epitope specificity, ratio of food-specific IgE to IgG4, food-specific IgA levels, component-resolved diagnostic profile, diet, gut microbiome, and interventions such as immunotherapy. Since food allergy places a significant burden on patients and their caregivers in daily life, clinicians should be able to provide relevant knowledge on the natural course of food allergy, appropriately evaluate its resolution, and offer therapeutic options whenever possible.

Obesity-induced hyperglycemia impairs oral tolerance induction and aggravates food allergy

Obesity and type 2 diabetes (T2D) have been found to be associated with abnormalities in several organs, including the intestine. These conditions can lead to changes in gut homeostasis, compromising tolerance to luminal antigens and increasing susceptibility to food allergies. The underlying mechanisms for this phenomenon are not yet fully understood. In this study, we investigated changes in the intestinal mucosa of diet-induced obese mice and found that they exhibited increased gut permeability and reduced Treg cells frequency. Upon oral treatment with ovalbumin (OVA), obese mice failed to develop oral tolerance. However, hyperglycemia treatment improved intestinal permeability and oral tolerance induction in mice. Furthermore, we observed that obese mice exhibited a more severe food allergy to OVA, and this allergy was alleviated after treatment with a hypoglycemic drug. Importantly, our findings were translated to obese humans. Individuals with T2D had higher serum IgE levels and downregulated genes related to gut homeostasis. Taken together, our results suggest that obesity-induced hyperglycemia can lead to a failure in oral tolerance and to exacerbation of food allergy. These findings shed light on the mechanisms underlying the relationship among obesity, T2D, and gut mucosal immunity, which could inform the development of new therapeutic approaches.

‘Early Introduction’ of Cow’s Milk for Children with IgE-Mediated Cow’s Milk Protein Allergy: A Review of Current and Emerging Approaches for CMPA Management

IgE-mediated cow’s milk protein allergy (CMPA) is one of the most prevalent food allergies in early childhood. Though the cornerstone of management involves the strict avoidance of milk products while awaiting natural tolerance, research increasingly shows that the rates of resolution are slowing down. Therefore, there is a need to explore alternative pathways to promote tolerance to cow’s milk in pediatric populations. This review aims to combine and appraise the scientific literature regarding the three CMPA management methods: avoidance, the milk ladder, and oral immunotherapy (OIT) and their outcomes in terms of efficacy, safety, and immunological effects. Cow’s milk (CM) avoidance virtually protects against allergic reaction until natural tolerance occurs, with hypoallergenic substitutes available in the market, but accidental ingestion represents the main issue for this strategy. Introduction to baked milk using the milk ladder was designed, with most CMPA patients successfully completing the ladder. Similar to baked milk treatment, many OIT protocols also demonstrated decreased IgE and increased IgG4 levels post protocol, as well as a reduction in wheal size diameter. Though these strategies are shown to be safe and effective in CMPA, future clinical trials should compare the safety and effectiveness of these three management strategies.

Current Practice in Pediatric Cow's Milk Protein Allergy-Immunological Features and Beyond

Cow's milk protein allergy is one of the most common pediatric food allergies. It poses a significant socioeconomic burden in industrialized countries and has a profound effect on the quality of life of affected individuals and their families. Diverse immunologic pathways can lead to the clinical symptoms of cow's milk protein allergy; some of the pathomechanisms are known in detail, but others need further elucidation. A comprehensive understanding of the development of food allergies and the features of oral tolerance could have the potential to unlock more precise diagnostic tools and novel therapeutic approaches for patients with cow's milk protein allergy.

Food antigen consumption and disease activity affect food-specific IgG4 levels in patients with eosinophilic esophagitis (EoE)

INTRODUCTION

High levels of serum food-specific IgG4 (sIgG4) have been reported in patients with EoE. The objective of this study was to examine whether serum sIgG4 levels to foods and aeroallergens are higher in EoE patients than allergic controls and to investigate the association between sIgG4 and EoE clinical characteristics.

METHODS

This was a case-control study nested in a prospective EoE Cohort. EoE cases were defined per consensus guidelines, and controls were individuals with symptoms who were confirmed to be EoE-negative on upper endoscopy. Demographic and clinical information was prospectively collected. Serum IgE and sIgG4 were measured to foods and aeroallergens by ImmunoCAP. Mean levels of sIgG4 were compared between cases and controls, and logistic regression models were used to examine predictors of elevated milk sIgG4 levels.

RESULTS

The analysis included 123 individuals (EoE n = 93, control n = 30) with a similar distribution of allergic disease between EoE patients and controls (86% vs. 93%; p = .30). EoE patients had significantly higher sIgG4 levels to all allergens evaluated, with the exception of birch (p = .24). Milk sIgG4 levels were independently associated with milk consumption (OR 4.95; p = .01) and the presence of sIgE to milk (OR 4.23; p = .008).

CONCLUSION

Serum sIgG4 levels to food and aeroallergen proteins were higher in patients with EoE than non-EoE controls, and higher levels of milk sIgG4 were independently associated with milk consumption and the presence of sIgE to milk proteins. Whether sIgG4 plays a pathogenic role in EoE or could be used as an EoE biomarker remains unknown and warrants further study.

CD4+CD25+CD127loFOXP3+ cell in food allergy: Does it predict anaphylaxis?

BACKGROUND

Food allergy (FA), hence the incidence of food anaphylaxis, is a public health problem that has increased in recent years. There are still no biomarkers for patients with FA to predict severe allergic reactions such as anaphylaxis.

OBJECTIVE

There is limited information on whether regulatory T (Treg) cell levels are a biomarker that predicts clinical severity in cases presenting with FA, and which patients are at a greater risk for anaphylaxis.

METHODS

A total of 70 children were included in the study: 25 who had IgE-mediated cow's milk protein allergy (CMPA) and presented with non-anaphylactic symptoms (FA/A-), 16 who had IgE-mediated CMPA and presented with anaphylaxis (FA/A+) (a total of 41 FA cases), and a control group consisting of 29 children without FA. The study was conducted by performing CD4+CD25+CD127^loFOXP3+ cell flow cytometric analysis during resting at least 2 weeks after the elimination diet to FA subjects.

RESULTS

When the FA group was compared with healthy control subjects, CD4+CD25+CD127_loFOXP3+ cell rates were found to be significantly lower in the FA group (p < 0.001). When the FA/A- and FA/A+ groups and the control group were compared in terms of CD4+CD25+CD127^loFOXP3+ cell ratios, they were significantly lower in the FA/A- and FA/A+ groups compared to the control group (p < 0.001).

CONCLUSIONS

Although there was no significant difference between the FA/A+ group and the FA/A- group in terms of CD4+CD25+CD127^loFOXP3+ cells, our study is important, as it is the first pediatric study we know to investigate whether CD4+CD25+CD127^loFOXP3+ cells in FA predict anaphylaxis.

Biomarkers in oral immunotherapy

Food allergy (FA) is a global health problem that affects a large population, and thus effective treatment is highly desirable. Oral immunotherapy (OIT) has been showing reasonable efficacy and favorable safety in most FA subjects. Dependable biomarkers are needed for treatment assessment and outcome prediction during OIT. Several immunological indicators have been used as biomarkers in OIT, such as skin prick tests, basophil and mast cell reactivity, T cell and B cell responses, allergen-specific antibody levels, and cytokines. Other novel indicators also could be potential biomarkers. In this review, we discuss and assess the application of various immunological indicators as biomarkers for OIT.

Special Diets in Infants and Children and Impact on Gut Microbioma

Gut microbiota is a complex system that starts to take shape early in life. Several factors influence the rise of microbial gut colonization, such as term and mode of delivery, exposure to antibiotics, maternal diet, presence of siblings and family members, pets, genetics, local environment, and geographical location. Breastfeeding, complementary feeding, and later dietary patterns during infancy and toddlerhood are major players in the proper development of microbial communities. Nonetheless, if dysbiosis occurs, gut microbiota may remain impaired throughout life, leading to deleterious consequences, such as greater predisposition to non-communicable diseases, more susceptible immune system and altered gut-brain axis. Children with specific diseases (i.e., food allergies, inborn errors of metabolism, celiac disease) need a special formula and later a special diet, excluding certain foods or nutrients. We searched on PubMed/Medline, Scopus and Embase for relevant pediatric studies published over the last twenty years on gut microbiota dietary patterns and excluded case reports or series and letters. The aim of this review is to highlight the changes in the gut microbiota in infants and children fed with special formula or diets for therapeutic requirements and, its potential health implications, with respect to gut microbiota under standard diets.

Immunological changes during desensitization with cow's milk: how differ from natural tolerance or nonallergic state?

BACKGROUND

Oral immunotherapy(OIT) is a novel allergen-specific treatment for food allergies.

OBJECTIVE

To investigate the effect of OIT on blocking antibodies, T cell regulation, and cytokine response during IgE-mediated cow's milk allergy(CMA) treatment.

METHODS

Fifty-seven children with Ig-E-mediated CMA who were followed in pediatric allergy outpatient clinic and 18 healthy children were included.The children were evaluated in four groups: OIT group, elimination group (patients receiving dairy elimination diet), tolerance group(patients who developed tolerance), healthy control group. Milk-specific IgE, IgG4, and IgA levels, cow's milk induration diameters in skin prick test, CD4+CD25+FoxP3+Treg cell percentages, mRNA expressions, and IL-10,TGF-β,IL-2,IL-4,IL-13 cytokine levels were compared between the groups.

RESULTS

The mean age of the patients was 42.6±39(6-201) months, 63.6%(n=49) of patients were girls. We observed an increase in total IgE levels(p=0.02) and a decrease in cow's-milk sIgE (p=0.08,NS), specific-IgA(p<0.01), and IgG4(p<0.01) levels at 2 months after the maintenance phase of OIT. In addition, the immune response after OIT treatment, which had a 100% clinical success rate, was notable for similar CD4+CD25+FoxP3+cell percentages(p=0.6), and increased IL-10(p=0.04) levels and increased but statistically nonsignificant TGF-β levels(p=0.17) compared with those before treatment.FoxP3 mRNA expression was similar to that of patients who developed natural tolerance. Pre-treatment and post-treatment FoxP3 mRNA-FoxP3 flow cytometric expressions were positively correlated with TGF-β concentrations in the OIT group.

CONCLUSION

A successful immune response to OIT was shown, possibly through the blockage of IgE-mediated allergen presentation by blocking antibodies, marked IL-10 cytokine response, and TGF-β response.FoxP3 mRNA expression was similar to the natural tolerance mechanism, but more studies are needed.

Pre- and Postnatal Vitamin D Status and Allergy Outcomes in Early Childhood

The dramatic increase in the prevalence of allergic disease in recent decades reflects environmental and behavioural changes that have altered patterns of early immune development. The very early onset of allergic diseases points to the specific vulnerability of the developing immune system to environmental changes and the development of primary intervention strategies is crucial to address this unparalleled burden. Vitamin D is known to have immunomodulatory functions. While allergic disease is multifactorial, associations with reduced sunlight exposure have led to the hypothesis that suboptimal vitamin D levels during critical early periods may be one possible explanation. Interventions to improve vitamin D status, especially in early life, may be the key to allergic disease prevention.

Engineering a safe monoclonal anti-human IL-2 that is effective in a murine model of food allergy and asthma

BACKGROUND

Regulatory T cells (Tregs) are known to protect against allergies. Moreover, the decrease in the frequency and efficiency of Tregs amplifies allergic symptoms.

AIM

This study investigated whether expanding Tregs in vivo with an IL-2/IL-2 antibody complex could be safe, well tolerated and efficient in a therapeutic setting in allergies.

METHODS

We produced an anti-IL-2 antibody (1C6) and demonstrated that when it is complexed to human IL-2, it increases IL-2 efficiency to induce Tregs in vivo without any detectable side effects. Furthermore, the IL-2/1C6 complex induces an increase in Helios expression by Tregs, suggesting that it not only elevated Treg numbers but also boosted their functions. Using mouse models of house-dust-mite-induced airway inflammation and wheat-gliadin-induced food allergies, we investigated the therapeutic potential of the IL-2/1C6 complex in allergies.

RESULTS

IL-2/1C6 treatment significantly reduced allergic symptoms, specific IgE production, the adaptive immune response and tissue damage. Interestingly, IL-2/1C6 treatment modulated innate lymphoid cells by increasing ILC2s in asthma and decreasing ILC3s in food allergies.

CONCLUSION

In conclusion,complexed IL-2/anti-IL-2 may restore Treg numbers and function in respiratory and food allergies, thereby improving allergic markers and symptoms. Our IL-2/anti-IL-2 complex offers new hope for reestablishing immune tolerance in patients with allergies.

Lycopene intake induces colonic regulatory T cells in mice and suppresses food allergy symptoms

BACKGROUND

Food allergy (FA) is a common disease in children; thus, a high level of safety is required for its prevention and treatment. Colonic regulatory T cells (Tregs) have been suggested to attenuate FA. We investigated the Treg-inducing ability and anti-FA effects of carotenoids, a pigment contained in vegetables and fruits.

METHODS

C57BL/6N mice were fed a diet containing 0.01% (w/w) of lycopene, β-carotene, astaxanthin or lutein for 4 weeks, and the population of colonic Tregs was assessed. Subsequently, to evaluate the Treg-inducing ability of lycopene, splenic naïve CD4⁺ T cells from BALB/c mice were cultured with anti-CD3/CD28 antibody, TGF-β and lycopene, and the frequencies of Tregs were examined. The effect of 0.1% (w/w) lycopene containing diet on FA was investigated in OVA-induced FA model BALB/c mice.

RESULTS

In screening, only lycopene significantly increased the frequency and number of colonic Tregs. Lycopene also increased Treg differentiation in splenic naïve CD4⁺ T cells. In FA mice, lycopene feeding significantly increased the number of colonic Tregs and attenuated allergic symptoms. The expression levels of IL-4, IL-9 and IL-13 mRNA in colonic mucosa were also significantly reduced by lycopene. IL-9 is known to induce proliferation of mast cells, and we found that lycopene feeding significantly reduced the number of mast cells in the colonic mucosa of FA mice.

CONCLUSION

Our results suggest that lycopene, a carotenoid present in many common foods on the market, may have the potential to induce colonic Tregs and suppress FA symptoms.

New Therapeutic Approaches for Allergy: A Review of Cell Therapy and Bio- or Nano-Material-Based Strategies

Allergy constitutes a major health issue due to its large prevalence. The established therapeutic approaches (allergen avoidance, antihistamines, and corticosteroids) do not address the underlying causes of the pathology, highlighting the need for other long-term treatment options. Antigen-specific immunotherapy enables the long-term control of allergic diseases by promoting immunological tolerance to the allergen. However, efficacious immunotherapies are not available for all possible allergens, and the risk of undesired reactions during therapy remains a concern, especially in patients with severe allergic reactions. In this context, two types of therapeutic strategies appear especially promising for the future in the context of allergy: cell therapy and bio- or nano-material-based therapy. In this review, the main strategies developed this far in these two types of strategies are discussed, with several examples illustrating the different approaches.

Successful Milk Oral Immunotherapy Promotes Generation of Casein-Specific CD137+ FOXP3+ Regulatory T Cells Detectable in Peripheral Blood

Background

Oral immunotherapy (OIT) is an emerging treatment for cow's milk protein (CMP) allergy in children. The mechanisms driving tolerance following OIT are not well understood. Regulatory T cells (T_REG) cells are key inhibitors of allergic responses and promoters of allergen-specific tolerance. In an exploratory study, we sought to detect induction of allergen-specific T_REG in a cohort of subjects undergoing OIT.

Methods

Pediatric patients with a history of allergic reaction to cow's milk and a positive Skin Pick Test (SPT) and/or CMP-specific IgE >0.35 kU, as well as a positive oral challenge to CMP underwent OIT with escalating doses of milk and were followed for up to 6 months. At specific milestones during the dose escalation and maintenance phases, casein-specific CD4⁺ T cells were expanded from patient blood by culturing unfractionated PBMCs with casein in vitro. The CD4⁺ T cell phenotypes were quantified by flow cytometry.

Results

Our culture system induced activated casein-specific FOXP3⁺Helios⁺ T_REG cells and FOXP3^- T_EFF cells, discriminated by expression of CD137 (4-1BB) and CD154 (CD40L) respectively. The frequency of casein-specific T_REG cells increased significantly with escalating doses of milk during OIT while casein-specific T_EFF cell frequencies remained constant. Moreover, expanded casein-specific T_REG cells expressed higher levels of FOXP3 compared to polyclonal T_REG cells, suggesting a more robust T_REG phenotype. The induction of casein-specific T_REG cells increased with successful CMP desensitization and correlated with increased frequencies of casein-specific Th1 cells among OIT subjects. The level of casein-specific T_REG cells negatively correlated with the time required to reach the maintenance phase of desensitization.

Conclusions

Overall, effective CMP-OIT successfully promoted the expansion of casein-specific, functionally-stable FOXP3⁺ T_REG cells while mitigating Th2 responses in children receiving OIT. Our exploratory study proposes that an in vitro T_REG response to casein may correlate with the time to reach maintenance in CMP-OIT.

Oral Immunotherapy for Children with Cow's Milk Allergy

Cow's milk allergy (CMA) is one of the most common IgE-dependent food allergies in children. Some children develop severe and persistent CMA, with near-fatal reactions after exposure to trace amounts of cow's milk (CM). Because milk and dairy products are included in various processed food products, it is difficult to completely remove milk, which negatively affects the quality of life of children with CMA. Oral immunotherapy (OIT) can alleviate food allergen-induced anaphylaxis under continuous ingestion of a little of the causative food. Children with severe CMA may benefit from OIT, but the treatment requires a long time and poses a risk of anaphylaxis. Moreover, in recent years, new therapies, including omalizumab, sublingual immunotherapy, and epicutaneous immunotherapy, have played the role of optional OIT. In this review, we present the current methods of and other attempts at OIT, and discuss OIT for safely treating CMA.

Altered immune cell profiles and impaired CD4 T-cell activation in single and multi-food allergic adolescents

BACKGROUND

Approximately 5% of adolescents have a food allergy, with peanut and tree nut allergies the most common. Having two or more food allergies in adolescence also doubles the risk of any adverse food reaction, and is associated with increased dietary and social burden. Investigations of immune function in persistently food allergic children are rare.

OBJECTIVE

In the present study, we aimed to investigate the immune mechanisms that underlie food allergy in adolescence.

METHODS

We used high-dimensional flow cytometry, unsupervised computational analysis and functional studies to comprehensively phenotype a range of non-antigen-specific immune parameters in a group of well-characterized adolescents with clinically defined single peanut allergy, multi-food allergy and aged-matched non-food allergic controls.

RESULTS

We show that food allergic adolescents have higher circulating proportions of dendritic cells (p = .0084, FDR-adjusted p = .087, median in no FA: 0.63% live cells, in FA: 0.93%), and higher frequency of activated, memory-like Tregs relative to non-food allergic adolescents (p = .011, FDR-adjusted p = .087, median in no FA: 0.49% live cells, in FA: 0.65%). Cytokine profiling revealed that CD3/CD28 stimulated naïve CD4 T cells from food allergic adolescents produced less IL-6 (p = .0020, FDR-adjusted p = .018, median log2 fold change [stimulated/unstimulated] in no FA: 3.03, in FA: 1.92) and TNFα (p = .0044, FDR-adjusted p = .020, median in no FA: 9.16, in FA: 8.64) and may secrete less IFNγ (p = .035, FDR-adjusted p = .11, median in no FA: 6.29, in FA: 5.67) than naïve CD4 T cells from non-food allergic controls. No differences between clinical groups were observed for LPS-stimulated monocyte secretion of cytokines.

CONCLUSIONS

These results have important implications for understanding the evolution of the immune response in food allergy throughout childhood, revealing that dendritic cell and T-cell signatures previously identified in early life may persist through to adolescence.

Preventing Atopic Diseases During Childhood - Early Exposure Matters

Atopic diseases in childhood are a major burden worldwide and there is still a lack of knowledge about treatable causes. In industrialized countries such as Germany, almost every second child is sensitized to at least one common allergen. Recent studies show that although the predisposition to allergies is inherited, the adaptive immune system of neonates and infants follows a developmental trajectory and whether an allergy actually occurs depends also on timing of allergen exposure including diet as well as environmental factors. New recommendations are far from being rigid of allergen avoidance; it is rather moving toward conditions that stand for more biodiversity. The observation that introduction of peanuts or eggs early in life significantly reduced the development of a later allergy will change our recommendations for the introduction of complementary foods. This is consistent with the hygiene hypothesis that early provocation shapes the developing immune system so that it reacts appropriately. Therefore, promoting the development of tolerance is at the heart of sensible allergy prevention - and this begins with the last trimester of pregnancy. In light of this concept, actual recommendations are discussed.

Biomarkers of diagnosis and resolution of food allergy

Food allergy is increasing in prevalence, affecting up to 10% of children in developed countries. Food allergy can significantly affect the quality of life and well-being of patients and their families; therefore, an accurate diagnosis is of extreme importance. Some food allergies can spontaneously resolve in 50%-60% of cow's milk and egg-allergic, 20% of peanut-allergic and 9% of tree nut-allergic children by school age. For that reason, food-allergic status should be monitored over time to determine when to reintroduce the food back into the child's diet. The gold-standard to confirm the diagnosis and the resolution of food allergy is an oral food challenge; however, this involves the risk of causing an acute-allergic reaction and requires clinical experience and resources to treat allergic reactions of any degree of severity. In the clinical setting, biomarkers have been used and validated to enable an accurate diagnosis when combined with the clinical history, deferring the oral food challenge, whenever possible. In this review, we cover the tools available to support the diagnosis of food allergies and to predict food allergy resolution over time. We review the latest evidence on different testing modalities and how effective they are in guiding clinical decision making in practice. We also evaluate predictive test cut-offs for the more common food allergens to try and provide guidance on when challenges might be most successful in determining oral tolerance in children.

Stool microbiome, pH and short/branched chain fatty acids in infants receiving extensively hydrolyzed formula, amino acid formula, or human milk through two months of age

BACKGROUND

Early infant feeding with intact or extensively hydrolyzed (EH) proteins or free amino acids (AA) may differentially affect intestinal microbiota composition and immune reactivity. This multicenter, double-blind, controlled, parallel-group, pilot study compared stool microbiota from Baseline (1-7 days of age) up to 60 days of age in healthy term infants who received mother's own milk (assigned to human milk [HM] reference group) (n = 25) or were randomized to receive one of two infant formulas: AA-based (AAF; n = 25) or EH cow's milk protein (EHF; n = 28). Stool samples were collected (Baseline, Day 30, Day 60) and 16S rRNA genes were sequenced. Alpha (Shannon, Simpson, Chao1) and beta diversity (Bray Curtis) were analyzed. Relative taxonomic enrichment and fold changes were analyzed (Wilcoxon, DESEq2). Short/branched chain fatty acids (S/BCFA) were quantified by gas chromatography. Mean S/BCFA and pH were analyzed (repeated measures ANOVA).

RESULTS

At baseline, alpha diversity measures were similar among all groups; however, both study formula groups were significantly higher versus the HM group by Day 60. Significant group differences in beta diversity at Day 60 were also detected, and study formula groups were compositionally more similar compared to HM. The relative abundance of Bifidobacterium increased over time and was significantly enriched at Day 60 in the HM group. In contrast, a significant increase in members of Firmicutes for study formula groups were detected at Day 60 along with butyrate-producing species in the EHF group. Stool pH was significantly higher in the AAF group at Days 30 and 60. Butyrate increased significantly from Baseline to Day 60 in the EHF group and was significantly higher in study formula groups vs HM at Day 60. Propionate was also significantly higher for EHF and AAF at Day 30 and AAF at Day 60 vs HM. Total and individual BCFA were higher for AAF and EHF groups vs HM through Day 60.

CONCLUSIONS

Distinct patterns of early neonatal microbiome, pH, and microbial metabolites were demonstrated for infants receiving mother's own milk compared to AA-based or extensively hydrolyzed protein formula. Providing different sources of dietary protein early in life may influence gut microbiota and metabolites.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02500563 . Registered July 28, 2015.

IgE and mast cells: The endogenous adjuvant

Mast cells and IgE are most familiar as the effectors of type I hypersensitivity reactions including anaphylaxis. It is becoming clear however that this pair has important immunomodulatory effects on innate and adaptive cells of the immune system. In this purview, they act as endogenous adjuvants to ignite evolving immune responses, promote the transition of allergic disease into chronic illness and disrupt the development of active mechanisms of tolerance to ingested foods. Suppression of IgE-mediated mast cell activation can be exerted by molecules targeting IgE, FcɛRI or signaling kinases including Syk, or by IgG antibodies acting via inhibitory Fcγ receptors. In 2015 we reviewed the evidence for the adjuvant functions of mast cells. This update includes the original text, incorporates some important developments in the field over the past five years and discusses how interventions targeting these pathways might have promise in the development of strategies to treat allergic disease.

Hyper-Inflammatory Monocyte Activation Following Endotoxin Exposure in Food Allergic Infants

Several recent studies have reported a key role for innate cell hyper-responsiveness in food allergy. This has predominantly been observed in early life, with evidence that innate immune function may return to baseline if food allergy resolves in later childhood. Hallmarks of hyper-responsiveness include increased circulating frequency of monocytes and altered innate cell cytokine responses to in vitro exposure with bacterial endotoxin. These features mirror the defining signatures of trained innate immunity, seen in other complex diseases. In this study, detailed immune cell and cytokine profiling was performed on peripheral blood mononuclear cells at baseline from 27 1 year old infants in the HealthNuts cohort (n = 16 egg allergic and n = 11 non-allergic healthy controls) and following monocyte stimulation. We show that egg allergic infants have increased frequency of circulating monocytes, reduced numbers of regulatory CD4 T cells and increased monocyte: CD4 T cell ratios relative to healthy controls. Monocytes from both egg allergic and non-allergic infants responded to endotoxin stimulation with rapid cytokine production and downregulation of the surface receptor CD16, however monocytes from egg allergic infants were hyper-responsive, producing significantly more inflammatory cytokines (TNFα, IL-6, IL-1β, IL-8) and innate cell recruiting factors (MIP-1α) than healthy controls. This work indicates that monocytes of food allergic infants are programmed to a hyper-inflammatory phenotype and that the development of food allergy may be associated with trained immunity in early life.

Reduced polyfunctional T cells and increased cellular activation markers in adult allergy patients reporting adverse reactions to food

Background

The underlying cellular mechanisms causing adverse reactions to food are complex and still not fully understood. Therefore, in this study we aimed to identify functional and/or phenotypical immune cell signatures characteristic for adult patients reporting adverse reactions to food.

By mass cytometry, we performed high-dimensional profiling of peripheral blood mononuclear cells (PBMC) from adult patients reporting adverse reactions to food and healthy controls. The patients were grouped according to sIgE-positive or sIgE-negative serology to common food and inhalant allergens. Two broad antibody panels were used, allowing determination of major immune cell populations in PBMC, as well as activation status, proliferation status, and cytokine expression patterns after PMA/ionomycin-stimulation on a single cell level.

Results

By use of data-driven algorithms, several cell populations were identified showing significantly different marker expression between the groups.

Most striking was an impaired frequency and function of polyfunctional CD4+ and CD8+ T cells in patients reporting adverse reactions to food compared to the controls. Further, subpopulations of monocytes, T cells, and B cells had increased expression of functional markers such as CD371, CD69, CD25, CD28, and/or HLA-DR as well as decreased expression of CD23 in the patients. Most of the differing cell subpopulations were similarly altered in the two subgroups of patients.

Conclusion

Our results suggest common immune cell features for both patient subgroups reporting adverse reactions to food, and provide a basis for further studies on mechanistic and diagnostic biomarker studies in food allergy.

A Potential Role for Epigenetically Mediated Trained Immunity in Food Allergy

The prevalence of IgE-mediated food allergy is increasing at a rapid pace in many countries. The association of high food allergy rates with Westernized lifestyles suggests the role of gene-environment interactions, potentially underpinned by epigenetic variation, in mediating this process. Recent studies have implicated innate immune system dysfunction in the development and persistence of food allergy. These responses are characterized by increased circulating frequency of innate immune cells and heightened inflammatory responses to bacterial stimulation in food allergic patients. These signatures mirror those described in trained immunity, whereby innate immune cells retain a “memory” of earlier microbial encounters, thus influencing subsequent immune responses. Here, we propose that a robust multi-omics approach that integrates immunological, transcriptomic, and epigenomic datasets, combined with well-phenotyped and longitudinal food allergy cohorts, can inform the potential role of trained immunity in food allergy.

Naïve regulatory T cells in infancy: Associations with perinatal factors and development of food allergy

BACKGROUND

In previous studies, deficits in regulatory T-cell (Treg) number and function at birth have been linked with subsequent allergic disease. However, longitudinal studies that account for relevant perinatal factors are required. The aim of this study was to investigate the relationship between perinatal factors, naïve Treg (nTreg) over the first postnatal year and development of food allergy.

METHODS

In a birth cohort (n = 1074), the proportion of nTreg in the CD4⁺ T-cell compartment was measured by flow cytometry at birth (n = 463), 6 (n = 600) and 12 (n = 675) months. IgE-mediated food allergy was determined by food challenge at 1 year. Associations between perinatal factors (gestation, labour, sex, birth size), nTreg at each time point and food allergy at 1 year were examined by linear regression.

RESULTS

A higher proportion of nTreg at birth, larger birth size and male sex was each associated with higher nTreg in infancy. Exposure to labour, as compared to delivery by prelabour Caesarean section, was associated with a transient decrease nTreg. Infants that developed food allergy had decreased nTreg at birth, and the labour-associated decrease in nTreg at birth was more evident among infants with subsequent food allergy. Mode of birth was not associated with risk of food allergy, and there was no evidence that nTreg at either 6 or 12 months were related to food allergy.

CONCLUSION

The proportion of nTreg at birth is a major determinant of the proportion present throughout infancy, highlighting the importance of prenatal immune development. Exposure to the inflammatory stimulus of labour appears to reveal differences in immune function among infants at risk of food allergy.

Mechanisms of food allergy

Although oral tolerance is the normal physiologic response to ingested antigens, a breakdown in this process appears to have occurred in the past 2 decades, leading to an increasing prevalence of sensitization to food allergens. Over the past decade, basic research has intensified in an attempt to better understand the mechanisms leading to sensitization and disease versus desensitization and short- and long-term tolerance. In this review we assess various factors that can influence tissue and immune responses to food antigens, the current understanding of immune tolerance development, the role of the gastrointestinal microbiota, and current knowledge regarding immunologic mechanisms involved in desensitization and sustained unresponsiveness, although perhaps the latter is more appropriately termed remission.

Cow's Milk Allergy: Immunomodulation by Dietary Intervention

Cow's milk proteins cause allergic symptoms in 2% to 3% of all infants. In these individuals, the physiological mechanism of tolerance is broken with subsequent possible sensitization to antigens, which can lead eventually to allergic responses. The present review aims to provide an overview of different aspects of immune modulation by dietary intervention in cow's milk allergy (CMA). It focuses on pathogenetic mechanisms of different CMA related disorders, e.g., gastroesophageal reflux and eosinophilic esophagitis, highlighting the role of dietary management on innate and adaptive immune systems. The traditional dietary management of CMA has greatly changed in the last years, moving from a passive approach, consisting of an elimination diet to relieve symptoms, to a "proactive" one, meaning the possibility to actively modulate the immune system. Thus, new insights into the role of hydrolysates and baked milk in immunomodulation are addressed here. Additionally, nutritional components, such as pre- and probiotics, may target the immune system via microbiota, offering a possible road map for new CMA prevention and treatment strategies.

Hypoallergenic Proteins for the Treatment of Food Allergy

PURPOSE OF REVIEW

Food allergy is a growing health problem worldwide that impacts millions of individuals. Current treatment options are limited and strict dietary avoidance remains the standard of care. Immunotherapy using whole, native allergens is under active clinical investigation but harbors the risk of severe side effects including anaphylaxis. Newer food-specific therapies with hypoallergenic proteins may potentially offer safer treatment alternatives, and this review seeks to investigate the evidence supporting the use of these modalities.

RECENT FINDINGS

The utilization of different methods to alter allergen structure and IgE binding leads to reduced allergenicity and decreases the risk for systemic reactions, making the use of potential therapies including extensively heated egg/milk, peptide immunotherapy, recombinant allergen immunotherapy, and DNA vaccines safe and possibly efficacious forms of treatment in food allergy. However, for the majority of these treatment modalities, limited data currently exists looking at the safety and efficacy in human subjects with food allergy. This review provides a comprehensive overview of the current evidence examining the safety and efficacy of hypoallergenic proteins in the treatment of food allergies.

The Impact of Baked Egg and Baked Milk Diets on IgE- and Non-IgE-Mediated Allergy

Baked milk (BM) and baked egg (BE) diets are increasingly used in the management of milk and egg allergy, rather than avoidance. Children with tolerance versus reactivity to BM and BE may have smaller skin prick test and lower specific IgE, and BM-tolerant children have less basophil reactivity and more peripheral T regulatory cells. However, most milk- and egg-allergic children tolerate BM and BE and an individual's reactivity is unpredictable. Non-reactivity is due to conformational changes in the allergens. Significant differences in the published advice about methods of introduction exist from graded introduction at home to a medically supervised full dose. These approaches carry different risks and may have different immunological effects. Reactivity to BM is a predictor of a severe milk allergy. Therefore, medical supervision for BM and BE introduction is prudent. The baked diet allows dietary liberation. Most, but not all, BM- and BE-tolerant children continue eating the baked foods. The prognosis of children who can eat BM and BE is favorable with likely resolution of their allergy over the next few years. Murine models of BE diets demonstrate that heated egg can impart clinical protection against anaphylaxis and cause immune changes. Most observational human studies of BM and BE diets demonstrate clinical resolution of allergy and favorable immune changes versus regular care controls. However, the one randomized controlled trial for the BE diet in BE-tolerant children did not support an immune-modifying effect of the BE diet. Another study of BE immunotherapy is expected to be completed in 2018. There is currently no evidence for prevention of allergy with the baked diets. There may be a future role for BM and BE in liberating the diets of individuals with non-IgE-mediated allergy given recent studies that a subset of these patients can consume BM without a clinical reaction.

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.

Decreased allergy incidence in children supplemented with E. coli O83:K24:H31 and its possible modes of action

The growing knowledge of the key role of microbiota in the maturation of neonatal immune system suggests that manipulation of microbiota could be exploited in hampering allergy development. In this study, Escherichia coli O83:K24:H31 (EcO83) was administered to newborns that were followed prospectively. Several immunological characteristics (cytokines, specific IgE, total T regulatory cells (Treg) and subpopulation of natural Treg (nTreg) and induced Treg (iTreg)) were tested in peripheral blood of 8-year-old children. Incidence of allergic disease was decreased in EcO83 supplemented children and significantly elevated levels of IL-10 and IFN-ɣ were detected in serum of EcO83 supplemented children. Probiotic supplementation did not influence the numbers of the total Treg population but their functional capacity (intracellular expression of IL-10) was significantly increased in children supplemented with EcO83 in comparison to non-supplemented children. Morover, decreased proportion of iTreg was present in peripheral blood of non-supplemented in comparison to EcO83 supplemented children. Finally, stimulation of cord blood cells with EcO83 promoted both gene expression and secretion of IL-10 and IFN-ɣ suggesting that beneficial effect of EcO83 in prevention of allergy development could be mediated by promotion of regulatory responses (by IL-10) and Th1 immune response (by IFN-ɣ).

Antigen-Specificity in the Thymic Development and Peripheral Activity of CD4+FOXP3+ T Regulatory Cells

CD4⁺Foxp3⁺ T regulatory cells (Treg) are essential for the life of the organism, in particular because they protect the host against its own autoaggressive CD4⁺Foxp3^- T lymphocytes (Tconv). Treg distinctively suppress autoaggressive immunity while permitting efficient defense against infectious diseases. This split effect indicates that Treg activity is controlled in an antigen-specific manner. This specificity is achieved first by the formation of the Treg repertoire during their development, and second by their activation in the periphery. This review presents novel information on the antigen-specificity of Treg development in the thymus, and Treg function in the periphery. These aspects have so far remained imprecisely understood due to the lack of knowledge of the actual antigens recognized by Treg during the different steps of their life, so that most previous studies have been performed using artificial antigens. However, recent studies identified some antigens mediating the positive selection of autoreactive Treg in the thymus, and the function of Treg in the periphery in autoimmune and allergic disorders. These investigations emphasized the remarkable specificity of Treg development and function. Indeed, the development of autoreactive Treg in the thymus was found to be mediated by single autoantigens, so that the absence of one antigen led to a dramatic loss of Treg reacting toward that antigen. The specificity of Treg development is important because the constitution of the Treg repertoire, and especially the presence of holes in this repertoire, was found to crucially influence human immunopathology. Indeed, it was found that the development of human immunopathology was permitted by the lack of Treg against the antigens driving the autoimmune or allergic T cell responses rather than by the impairment of Treg activation or function. The specificity of Treg suppression in the periphery is therefore intimately associated with the mechanisms shaping the formation of the Treg repertoire during their development. This novel information refines significantly our understanding of the antigen-specificity of Treg protective function, which is required to envision how these cells distinctively regulate unwanted immune responses as well as for the development of appropriate approaches to optimally harness them therapeutically in autoimmune, malignant, and infectious diseases.

Egg-specific IgE and basophil activation but not egg-specific T-cell counts correlate with phenotypes of clinical egg allergy

BACKGROUND

Egg allergy is phenotypically heterogeneous. A subset of patients with egg allergy can tolerate egg in an extensively heated form. Inclusion of baked egg (BE) into the diet accelerates resolution of egg allergy. Conversely, BE reactivity is associated with persistent disease. The immune basis of this clinical heterogeneity is unknown.

OBJECTIVES

We sought to study egg-specific antibody, basophil, and T-cell responses in children with reactivity or tolerance to BE.

METHODS

All participants underwent double-blind, placebo-controlled challenges to BE, and those who tolerated BE were challenged with unheated egg white protein to confirm clinical egg reactivity. Laboratory studies included serum antibody measurements, basophil activation tests, and CD154-based detection of egg-responsive T cells by using flow cytometry.

RESULTS

Of the 129 children studied, BE-reactive participants had significantly greater levels of egg-, ovalbumin-, and ovomucoid-specific IgE; lower ratios of egg-specific IgG4/IgE; and increased basophil activation in response to egg. Among all participants, CD154-based profiling revealed egg-responsive T cells producing IL-4 and IL-13 but little IL-10 or IFN-γ, as well as the presence of egg-responsive Foxp3+CD25+CD127low regulatory T cells. Egg-responsive T cells expressed CCR4, CCR6, and CXCR5, indicating capacity for homing to the skin, mucosa, and B-cell follicles. However, neither the frequency nor phenotype of egg-responsive T cells was different in those with tolerance or reactivity to BE.

CONCLUSIONS

Egg-specific antibody and basophil responses, but not T-cell responses, are greater in those with reactivity versus tolerance to BE. Egg-specific antibody and T-cell responses were highly heterogeneous in this cohort. The clinical implications of this immune heterogeneity will need to be studied longitudinally.

Debates in Allergy Medicine: Does oral immunotherapy shorten the duration of milk and egg allergy? The pro argument

The development of oral tolerance or food allergy is an active process, related to dynamic interactions between host immune cells, microbiome, dietary factors, and food allergens. Oral tolerance is the default immune response in the gut. A food allergy occurs when this process fails and a pathologic Th2 response is activated. Oral food immunotherapy (OIT) aims to restore immune tolerance in food-allergic individuals. The stimulation of Tregs production seems to represent a crucial step in inducing long-term tolerance, but other mechanisms (e.g., the suppression of mast cell and basophil reactivity, changes in allergen-specific cells with regulatory markers) are involved. Several studies reported the efficacy of OIT in terms of "sustained unresponsiveness" (SU), an operational definition of immune tolerance. In successfully treated subjects, the ability to pass an oral food challenge 2 to 8 weeks after stopping the food allergen exposure seems to be conditioned by the treatment starting age, frequency, amount or type of food consumed, and by the duration of the maintenance phase. Based on the available data, the percentage of milk- and egg-allergic subjects achieving sustained unresponsiveness after an OIT ranges from 21% to 58,3%. A comprehensive understanding of mechanisms underlying the induction of oral tolerance with OIT, or natural tolerance to food allergens in healthy individuals, could potentially lead to advances in development of better treatment options for food allergic patients.

Single-cell profiling of peanut-responsive T cells in patients with peanut allergy reveals heterogeneous effector TH2 subsets

BACKGROUND

The contribution of phenotypic variation of peanut-specific T cells to clinical allergy or tolerance to peanut is not well understood.

OBJECTIVES

Our objective was to comprehensively phenotype peanut-specific T cells in the peripheral blood of subjects with and without peanut allergy (PA).

METHODS

We obtained samples from patients with PA, including a cohort undergoing baseline peanut challenges for an immunotherapy trial (Consortium of Food Allergy Research [CoFAR] 6). Subjects were confirmed as having PA, or if they passed a 1-g peanut challenge, they were termed high-threshold subjects. Healthy control (HC) subjects were also recruited. Peanut-responsive T cells were identified based on CD154 expression after 6 to 18 hours of stimulation with peanut extract. Cells were analyzed by using flow cytometry and single-cell RNA sequencing.

RESULTS

Patients with PA had tissue- and follicle-homing peanut-responsive CD4+ T cells with a heterogeneous pattern of TH2 differentiation, whereas control subjects had undetectable T-cell responses to peanut. The PA group had a delayed and IL-2-dependent upregulation of CD154 on cells expressing regulatory T (Treg) cell markers, which was absent in HC or high-threshold subjects. Depletion of Treg cells enhanced cytokine production in HC subjects and patients with PA in vitro, but cytokines associated with highly differentiated TH2 cells were more resistant to Treg cell suppression in patients with PA. Analysis of gene expression by means of single-cell RNA sequencing identified T cells with highly correlated expression of IL4, IL5, IL9, IL13, and the IL-25 receptor IL17RB.

CONCLUSIONS

These results demonstrate the presence of highly differentiated TH2 cells producing TH2-associated cytokines with functions beyond IgE class-switching in patients with PA. A multifunctional TH2 response was more evident than a Treg cell deficit among peanut-responsive T cells.

Oral immunotherapy with omalizumab reverses the Th2 cell-like programme of regulatory T cells and restores their function

BACKGROUND

Oral immunotherapy (OIT) successfully desensitizes patients with food allergies, but the immune mechanisms mediating its efficacy remain obscure.

OBJECTIVES

We tested the hypothesis that allergen-specific regulatory T (Treg) cell function is impaired in food allergy and is restored by anti-IgE antibody (omalizumab)-supplemented OIT.

METHODS

Peanut-specific T effector (Teff) and Treg cell proliferative responses, activation markers and cytokine expression were analysed by flow cytometry in 13 peanut-allergic subjects before the start of omalizumab-supplemented OIT and periodically in some subjects thereafter for up to 2 years. Peripheral blood regulatory T cells (Treg cells) were analysed for their peanut-specific suppressor function before and at 1 year following OIT. This study was registered on ClinicalTrials.gov (NCT01290913).

RESULTS

Proliferation of allergen-specific Teff and Treg cells precipitously declined following the initiation of omalizumab therapy prior to OIT, followed by partial recovery after the initiation of OIT. At baseline, peanut-specific Treg cells exhibited a Th2 cell-like phenotype, characterized by increased IL-4 expression, which progressively reversed upon OIT. Peanut-specific Treg cell suppressor activity was absent at the start of omalizumab/OIT therapy but became robust following OIT. Absent peanut-specific Treg cell function could also be recovered by the acute blockade of IL-4/IL-4R receptor signalling in Treg cells, which inhibited their IL-4 production.

CONCLUSIONS AND CLINICAL RELEVANCE

OIT supplemented by omalizumab promotes allergen desensitization through an initial omalizumab-dependent step that acutely depletes allergen-reactive T cells, followed by an increase in allergen-specific Treg cell activity due to the reversal of their Th2 cell-like programme. Improved Treg cell function may be a key mechanism by which OIT ameliorates food allergy.

Systemic IL-2/anti-IL-2Ab complex combined with sublingual immunotherapy suppresses experimental food allergy in mice through induction of mucosal regulatory T cells

BACKGROUND

Therapeutic tolerance restoration has been proven to modify food allergy in patients and animal models and although sublingual immunotherapy (SLIT) has showed promise, combined therapy may be necessary to achieve a strong and long-term tolerance.

AIMS

In this work, we combined SLIT with systemic administration of IL-2 associated with an anti-IL-2 monoclonal antibody (IL-2/anti-IL-2Ab complex or IL-2C) to reverse the IgE-mediated experimental allergy.

MATERIALS AND METHODS

Balb/c mice were sensitized with cholera toxin and milk proteins and orally challenged with allergen to elicit hypersensitivity reactions. Then, allergic mice were treated with a sublingual administration of very low amounts of milk proteins combined with intraperitoneal injection of low doses of IL-2C. The animals were next re-exposed to allergens and mucosal as well as systemic immunological parameters were assessed in vivo and in vitro.

RESULTS

The treatment reduced serum specific IgE, IL-5 secretion by spleen cells and increased IL-10 and TGF-β in the lamina propria of buccal and duodenal mucosa. We found an augmented frequency of IL-10-secreting CD4⁺ CD25⁺ Foxp3⁺ regulatory T cells (Treg) in the submaxilar lymph nodes and buccal lamina propria. Tregs were sorted, characterized and adoptively transferred to naïve mice, which were subsequently sensitized. No allergy was experienced in these mice and we encouragingly discovered a faster and more efficient tolerance induction with the combined therapy compared with SLIT.

CONCLUSION

The combination of two therapeutic strategies rendered Treg-mediated tolerance more efficient compared to individual treatments and reversed the established IgE-mediated food allergy. This approach highlights the ability of IL-2C to expand Tregs, and it may represent a promising disease-modifying therapy for managing food allergy.

Identification and analysis of peanut-specific effector T and regulatory T cells in children allergic and tolerant to peanut

BACKGROUND

Peanut allergy (PA) is potentially life-threatening and generally persists for life. Recent data suggest the skin might be an important route of initial sensitization to peanut, whereas early oral exposure to peanut is protective. In mice regulatory T (Treg) cells are central to the development of food tolerance, but their contribution to the pathogenesis of food allergy in human subjects is less clear.

OBJECTIVE

We sought to quantify and phenotype CD4⁺ peanut-specific effector T (ps-Teff) cells and peanut-specific regulatory T (ps-Treg) cells in children with and without PA or PS.

METHODS

ps-Teff and ps-Treg cells were identified from peripheral blood of children with PA, children with PS, and nonsensitized/nonallergic (NA) school-aged children and 1-year-old infants based on upregulation of CD154 or CD137, respectively, after stimulation with peanut extract. Expression of cytokines and homing receptors was evaluated by using flow cytometry. Methylation at the forkhead box protein 3 (FOXP3) locus was measured as a marker of Treg cell stability.

RESULTS

Differential upregulation of CD154 and CD137 efficiently distinguished ps-Teff and ps-Treg cells. A greater percentage of ps-Teff cells from infants with PA and infants with PS expressed the skin-homing molecule cutaneous lymphocyte antigen, suggesting activation after exposure through the skin, compared with NA infants. Although ps-Teff cells in both school-aged and infant children with PA produced primarily T_H2 cytokines, a T_H1-skewed antipeanut response was seen only in NA school-aged children. The frequency, homing receptor expression, and stability of ps-Treg cells in infants and school-aged children were similar, regardless of allergic status.

CONCLUSIONS

Exposure to peanut through the skin can prime the development of T_H2 ps-Teff cells, which promote sensitization to peanut, despite the presence of normal numbers of ps-Treg cells.

Retinoic acid prevents immunogenicity of milk lipocalin Bos d 5 through binding to its immunodominant T-cell epitope

The major cow’s milk allergen Bos d 5 belongs to the lipocalin protein family, with an intramolecular pocket for hydrophobic ligands. We investigated whether Bos d 5 when loaded with the active vitamin A metabolite retinoic acid (RA), would elicit differential immune responses compared to the unloaded state. By in silico docking an affinity energy of −7.8 kcal/mol was calculated for RA into Bos d 5. Loading of RA to Bos d 5 could be achieved in vitro, as demonstrated by ANS displacement assay, but had no effect on serum IgE binding in tolerant or challenge-positive milk allergic children. Bioinformatic analysis revealed that RA binds to the immunodominant T-cell epitope region of Bos d 5. In accordance, Bos d 5 significantly suppressed the CD3+ CD4+ cell numbers, proliferative response and IL-10, IL-13 and IFN-γ secretion from stimulated human PBMCs only when complexed with RA. This phenomenon was neither associated with apoptosis of T-cells nor with the activation of Foxp3+ T-cells, but correlated likely with enhanced stability to lysosomal digestion due to a predicted overlap of Cathepsin S cleavage sites with the RA binding site. Taken together, proper loading of Bos d 5 with RA may suppress its immunogenicity and prevent its allergenicity.

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.

Increased Tolerance to Less Extensively Heat-Denatured (Baked) Milk Products in Milk-Allergic Children

BACKGROUND

Most milk-allergic children tolerate baked milk.

OBJECTIVE

To investigate the effect of more frequent versus less frequent introduction of higher doses of more allergenic (less heat-denatured) forms of milk (MAFM) on progression to tolerance.

METHODS

Milk-allergic children were challenged with increasing doses of MAFM; baked foods were incorporated into the diet; challenges were repeated at 6- or 12-month intervals over 36 months.

RESULTS

A total of 136 children (70% males) were enrolled in the active group (median age, 7 years). At baseline, 41 (30%) reacted to muffin, 31 (23%) to pizza, 11 (8%) to rice pudding, 43 (32%) to non-baked milk; and 10 (7%) tolerated non-baked milk. Children who tolerated baked milk but reacted to non-baked liquid milk were randomized to MAFM challenges every 6 months (n = 41) or 12 months (n = 44). At month 36, 61% children in the 6-month and 73% in the 12-month escalation groups tolerated MAFM. Overall, 41 (48%) children who ingested baked-milk diet became tolerant to non-baked milk; no difference was seen between 6- and 12- month escalations. Among children who reacted to muffin at baseline and continued avoidance, 20% developed tolerance to baked milk and 0% tolerated non-baked milk. None of the 34 children who qualified for inclusion but chose not to take part in the active study became tolerant to any form of milk by history.

CONCLUSIONS

Majority of children tolerated baked milk at baseline. Baked-milk diets were associated with progressive immunomodulation. Most children who incorporated baked milk into their diet progressed to tolerating MAFM, but there was no advantage to more frequent attempts to escalate to MAFM, per intention-to-treat analysis.

Maternal IgG immune complexes induce food allergen-specific tolerance in offspring

The role of maternal immune responses in tolerance induction is poorly understood. To study whether maternal allergen sensitization affects offspring susceptibility to food allergy, we epicutaneously sensitized female mice with ovalbumin (OVA) followed by epicutaneous sensitization and oral challenge of their offspring with OVA. Maternal OVA sensitization prevented food anaphylaxis, OVA-specific IgE production, and intestinal mast cell expansion in offspring. This protection was mediated by neonatal crystallizable fragment receptor (FcRn)-dependent transfer of maternal IgG and OVA immune complexes (IgG-IC) via breast milk and induction of allergen-specific regulatory T (T reg) cells in offspring. Breastfeeding by OVA-sensitized mothers or maternal supplementation with IgG-IC was sufficient to induce neonatal tolerance. FcRn-dependent antigen presentation by CD11c⁺ dendritic cells (DCs) in offspring was required for oral tolerance. Human breast milk containing OVA-IgG-IC induced tolerance in humanized FcRn mice. Collectively, we demonstrate that interactions of maternal IgG-IC and offspring FcRn are critical for induction of T reg cell responses and control of food-specific tolerance in neonates.