Allergen-specific T cells and clinical features of food allergy: Lessons from CoFAR immunotherapy cohorts

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.

Allergenicity Modulation of Casein with the Modifications of Linearization, Cross-Linking, and Glycation via the Regulation of Th1/Th2 Homeostasis

Casein (CN) is the primary allergenic protein in cow's milk, contributing to the worldwide escalating prevalence of food allergies. However, there remains limited knowledge regarding the effect of structural modifications on CN allergenicity. Herein, we prepared three modified CNs (mCN), including sodium dodecyl sulfate and dithiothreitol-induced linear CN (LCN), transglutaminase-cross-linked CN (TCN), and glucose-glycated CN (GCN). The electrophoresis results indicated widespread protein aggregation among mCN, causing variations in their molecular weights. The unique internal and external structural characteristics of mCN were substantiated by disparities in surface microstructure, alterations in the secondary structure, variations in free amino acid contents, and modifications in functional molecular groups. Despite the lower digestibility of TCN and GCN compared to LCN, they significantly suppressed IL-8 production in Caco-2 cells without significantly promoting their proliferation. Moreover, GCN showed the weakest capacity to induce LAD2 cell degranulation. Despite the therapeutic effect of TCN, GCN-treated mice displayed the most prominent attenuation of allergic reactions and a remarkably restored Th1/Th2 imbalance, while LCN administration resulted in severe allergic phenotypes and endotypes in both cellular and murine models. This study highlighted the detrimental effect of linear modifications and underscored the significance of glycation in relation to CN allergenicity.

A systematic review of allergen cross-reactivity: Translating basic concepts into clinical relevance

Access to the molecular culprits of allergic reactions allows for the leveraging of molecular allergology as a new precision medicine approach-one built on interdisciplinary, basic, and clinical knowledge. Molecular allergology relies on the use of allergen molecules as in vitro tools for the diagnosis and management of allergic patients. It complements the conventional approach based on skin and in vitro allergen extract testing. Major applications of molecular allergology comprise accurate identification of the offending allergen thanks to discrimination between genuine sensitization and allergen cross-reactivity, evaluation of potential severity, patient-tailored choice of the adequate allergen immunotherapy, and prediction of its expected efficacy and safety. Allergen cross-reactivity, defined as the recognition of 2 or more allergen molecules by antibodies or T cells of the same specificity, frequently interferes with allergen extract testing. At the mechanistic level, allergen cross-reactivity depends on the allergen, the host's immune response, and the context of their interaction. The multiplicity of allergen molecules and families adds further difficulty. Understanding allergen cross-reactivity at the immunologic level and translating it into a daily tool for the management of allergic patients is further complicated by the ever-increasing number of characterized allergenic molecules, the lack of dedicated resources, and the need for a personalized, patient-centered approach. Conversely, knowledge sharing paves the way for improved clinical use, innovative diagnostic tools, and further interdisciplinary research. Here, we aimed to provide a comprehensive and unbiased state-of-the art systematic review on allergen cross-reactivity. To optimize learning, we enhanced the review with basic, translational, and clinical definitions, clinical vignettes, and an overview of online allergen databases.

Studying antigen-specific T cells through a streamlined, whole blood-based extracellular approach

Techniques currently used for the study of antigen-specific T-cell responses are either poorly informative or require a heavy workload. Consequently, many perspectives associated with the broader study of such approaches remain mostly unexplored in translational research. However, these could benefit many fields including but not limited to infectious diseases, oncology, and vaccination. Herein, the main objective of this work was to develop a standardized flow cytometry-based approach that would combine ease of use together with a relevant study of antigen-specific T-cell responses so that they could be more often included in clinical research. To this extent, a streamlined approach relying on 1/ the use of whole blood instead of peripheral blood mononuclear cells and 2/ solely based on the expression of extracellular activation-induced markers (AIMs), called whole blood AIM (WAIM), was developed and further compared to more conventional techniques such as enzyme-linked immunospot (ELISpot) and flow cytometry-based intracellular cytokine staining (ICS). Based on a cohort of 20 individuals receiving the COVID-19 mRNA vaccine and focusing on SARS-CoV-2 and cytomegalovirus (CMV)-derived antigen T-cell-specific responses, a significant level of correlation between the three techniques was found. Based on the use of whole blood and on the expression of extracellular activation-induced markers (CD154, CD137, and CD107a), the WAIM technique appears to be very simple to implement and yet allows interesting patient stratification capabilities as the chosen combination of extracellular markers exhibited higher orthogonality than cytokines that are commonly considered in ICS (IFN-γ, TNF-α, and IL-2).

[Spontaneous remission of urticaria: does it exist and if so, when?]

BACKGROUND

Urticaria mostly occurs acutely with a very high probability of spontaneous remission. When it persists for more than 6 weeks a chronic urticaria is manifest, which occurs either spontaneously or inducible by specific triggers. The underlying mechanisms are not fully understood but recent research points to defined pathogenetic factors.

QUESTION AND AIM

Whether spontaneous remission is possible in urticaria is summarized descriptively in this review, and suggestions are given for the "step down" of urticaria treatment after remission. The mechanisms including autoallergic, immunoglobulin E (IgE)-dependent type I reactions and autoimmune, activating IgG-dependent type IIb reactions are presented. These are discussed in the context of spontaneous remission and the possibilities of induced remission.

Hot topics in allergen immunotherapy, 2023: Current status and future perspective

The importance of allergen immunotherapy (AIT) is multifaceted, encompassing both clinical and quality-of-life improvements and cost-effectiveness in the long term. Key mechanisms of allergen tolerance induced by AIT include changes in memory type allergen-specific T- and B-cell responses towards a regulatory phenotype with decreased Type 2 responses, suppression of allergen-specific IgE and increased IgG1 and IgG4, decreased mast cell and eosinophil numbers in allergic tissues and increased activation thresholds. The potential of novel patient enrolment strategies for AIT is taking into account recent advances in biomarkers discoveries, molecular allergy diagnostics and mobile health applications contributing to a personalized approach enhancement that can increase AIT efficacy and compliance. Artificial intelligence can help manage and interpret complex and heterogeneous data, including big data from omics and non-omics research, potentially predict disease subtypes, identify biomarkers and monitor patient responses to AIT. Novel AIT preparations, such as synthetic compounds, innovative carrier systems and adjuvants, are also of great promise. Advances in clinical trial models, including adaptive, complex and hybrid designs as well as real-world evidence, allow more flexibility and cost reduction. The analyses of AIT cost-effectiveness show a clear long-term advantage compared to pharmacotherapy. Important research questions, such as defining clinical endpoints, biomarkers of patient selection and efficacy, mechanisms and the modulation of the placebo effect and alternatives to conventional field trials, including allergen exposure chamber studies are still to be elucidated. This review demonstrates that AIT is still in its growth phase and shows immense development prospects.

Feast for thought: A comprehensive review of food allergy 2021-2023

A review of the latest publications in food allergy over the past couple of years confirmed that food allergy is a major public health concern, affecting about 8% of children and 10% of adults in developed countries. The prevalence of food allergy varies around the world, with the increase being driven mainly by environmental factors, possibly together with genetic susceptibility to environmental changes. A precise diagnosis of food allergy is extremely important. Both new tests (eg, the basophil activation test) and improved optimization of information provided by existing tests (eg, the skin prick test and measurement of specific IgE level) can contribute to improving the accuracy and patients' comfort of food allergy diagnosis. Understanding the underlying immune mechanisms is fundamental to designing allergen-specific treatments that can be safe and effective in the long term. New discoveries of the immune response to food allergens, including T-cell and B-cell responses, have emerged. Novel therapeutic approaches are being trialed at various stages of development as attempts to allow for more active intervention to treat food allergy. Prevention is key to reducing the increase in prevalence. Early introduction of allergenic foods seems to be the most effective intervention, but others are being studied, and will, it is hoped, lead to modification of the epidemiologic trajectory of food allergy over time.

Phase 1 trial supports safety and mechanism of action of peptide immunotherapy for peanut allergy

BACKGROUND

Food allergy is a leading cause of anaphylaxis worldwide. Allergen-specific immunotherapy is the only treatment shown to modify the natural history of allergic disease, but application to food allergy has been hindered by risk of severe allergic reactions and short-lived efficacy. Allergen-derived peptides could provide a solution. PVX108 comprises seven short peptides representing immunodominant T-cell epitopes of major peanut allergens for treatment of peanut allergy.

METHODS

Pre-clinical safety of PVX108 was assessed using ex vivo basophil activation tests (n = 185). Clinical safety and tolerability of single and repeat PVX108 doses were evaluated in a first-in-human, randomized, double-blind, placebo-controlled trial in peanut-allergic adults (46 active, 21 placebo). The repeat-dose cohort received six doses over 16 weeks with safety monitored to 21 weeks. Exploratory immunological analyses were performed at pre-dose, Week 21 and Month 18 after treatment.

RESULTS

PVX108 induced negligible activation of peanut-sensitised basophils. PVX108 was safe and well tolerated in peanut-allergic adults. There were no treatment-related hypersensitivity events or AEs of clinical concern. The only events occurring more frequently in active than placebo were mild injection site reactions. Exploratory immunological analyses revealed a decrease in the ratio of ST2+ Th2A:CCR6+ Th17-like cells within the peanut-reactive Th pool which strengthened following treatment.

CONCLUSION

This study supports the concept that PVX108 could provide a safe alternative to whole peanut immunotherapies and provides evidence of durable peanut-specific T-cell modulation. Translation of these findings to clinical efficacy in ongoing Phase 2 trials would provide important proof-of-concept for using peptides to treat 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.

A novel peanut allergy immunotherapy: Plant-based enveloped Ara h 2 Bioparticles activate dendritic cells and polarize T cell responses to Th1

Introduction

As the only market-authorized allergen immunotherapy (AIT) for peanut allergy is accompanied by a high risk of side effects and mainly induces robust desensitization without sustained efficacy, novel treatment options are required. Peanut-specific plant-derived eBioparticles (eBPs) surface expressing Ara h 2 at high density have been shown to be very hypoallergenic. Here, we assessed the dendritic cell (DC)-activating and T cell polarization capacity of these peanut-specific eBPs.

Methods

Route and kinetics of eBP uptake were studied by (imaging) flow cytometry using monocyte-derived DCs incubated with fluorescently-labelled Ara h 2 eBPs or natural Ara h 2 (nAra h 2) in the presence or absence of inhibitors that block pathways involved in macropinocytosis, phagocytosis, and/or receptor-mediated uptake. DC activation was monitored by flow cytometry (maturation marker expression) and ELISA (cytokine production). T cell polarization was assessed by co-culturing DCs exposed to Ara h 2 eBPs or nAra h 2 with naïve CD4+ T cells, followed by flow cytometry assessment of intracellular IFNγ+ (Th1) and IL-13+ (Th2), and CD25+CD127-Foxp3+ regulatory T cells (Tregs). The suppressive activity of Tregs was tested using a suppressor assay.

Results

Ara h 2 eBPs were taken up by DCs through actin-dependent pathways. They activated DCs demonstrated by an induced expression of CD83 and CD86, and production of TNFα, IL-6, and IL-10. eBP-treated DCs polarized naïve CD4+ T cells towards Th1 cells, while reducing Th2 cell development. Furthermore, eBP-treated DCs induced reduced the frequency of Foxp3+ Tregs but did not significantly affect T cell IL-10 production or T cells with suppressive capacity. In contrast, DC activation and Th1 cell polarization were not observed for nAra h 2.

Conclusion

Ara h 2 eBPs activate DCs that subsequently promote Th1 cell polarization and reduce Th2 cell polarization. These characteristics mark Ara h 2 eBPs as a promising novel candidate for peanut AIT.

Recent advances in epicutaneous immunotherapy and potential applications in food allergy

Given the potent immunological properties of the skin, epicutaneous immunotherapy (EPIT) emerges as a promising treatment approach for inducing immune tolerance, particularly for food allergies. Targeting the highly immunocompetent, non-vascularized epidermis allows for the application of microgram amounts of allergen while significantly reducing the risk of allergen passage into the bloodstream, thus limiting systemic allergen exposure and distribution. This makes EPIT highly suitable for the treatment of potentially life-threatening allergies such as food allergies. Multiple approaches to EPIT are currently under investigation for the treatment of food allergy, and these include the use of allergen-coated microneedles, application of allergen on the skin pretreated by tape stripping, abrasion or laser-mediated microperforation, or the application of allergen on the intact skin using an occlusive epicutaneous system. To date, the most clinically advanced approach to EPIT is the Viaskin technology platform. Viaskin is an occlusive epicutaneous system (patch) containing dried native allergen extracts, without adjuvants, which relies on frequent application for the progressive passage of small amounts of allergen to the epidermis through occlusion of the intact skin. Numerous preclinical studies of Viaskin have demonstrated that this particular approach to EPIT can induce potent and long-lasting T-regulatory cells with broad homing capabilities, which can exert their suppressive effects in multiple organs and ameliorate immune responses from different routes of allergen exposure. Clinical trials of the Viaskin patch have studied the efficacy and safety for the treatment of life-threatening allergies in younger patients, at an age when allergic diseases start to occur. Moreover, this treatment approach is designed to provide a non-invasive therapy with no restrictions on daily activities. Taken together, the preclinical and clinical data on the use of EPIT support the continued investigation of this therapeutic approach to provide improved treatment options for patients with allergic disorders in the near future.

Immune signatures predicting the clinical outcome of peanut oral immunotherapy: where we stand

Peanut allergy is a growing health concern that can cause mild to severe anaphylaxis as well as reduced quality of life in patients and their families. Oral immunotherapy is an important therapeutic intervention that aims to reshape the immune system toward a higher threshold dose reactivity and sustained unresponsiveness in some patients. From an immunological point of view, young patients, especially those under 3 years old, seem to have the best chance for therapy success. To date, surrogate markers for therapy duration and response are evasive. We provide a comprehensive overview of the current literature state regarding immune signatures evolving over the course of oral immunotherapy as well as baseline immune conditions prior to the initiation of treatment. Although research comparing clinical and immune traits in the first years of life vs. later stages across different age groups is limited, promising insights are available on immunological endotypes among peanut-allergic patients. The available data call for continued research to fill in gaps in knowledge, possibly in an integrated manner, to design novel precision health approaches for advanced therapeutic interventions in peanut allergy.

T-cell subsets in allergy and tolerance induction

Antigen-specific T lymphocytes are the central regulators of tolerance versus immune pathology against otherwise innocuous antigens and key targets of antigen-specific immune therapy. Recent advances in the understanding of T cells in tolerance and allergy resulted from improved technologies to directly characterize allergen-specific T cells by multiparameter flow cytometry or single-cell sequencing. This unravelled phenotypically and functionally distinct populations, such as Type 2a T helper cells (Th2a), follicular Th cells (Tfh), regulatory T cells (Treg), Type 1 regulatory T cells (Tr1), and follicular T regulatory cells. Here we will discuss the role of the different Th-cell subsets in the healthy state, during sensitization and development of allergy, and in tolerance induction by allergen immunotherapy (AIT). To date, the mechanisms of AIT as the only causal treatment of allergy are not completely understood. The analyses of allergen-specific T cells directly ex vivo during AIT support the concept of specific-Th2(a) cell deletion rather than an expansion of allergen-specific Tr1 or Treg cells as underlying mechanism.

Immune response evolution in peanut epicutaneous immunotherapy for peanut-allergic children

BACKGROUND

Epicutaneous immunotherapy with investigational Viaskin™ Peanut 250 μg (DBV712) has demonstrated statistically superior desensitization versus placebo in peanut-allergic children in clinical trials. It is unclear whether serologic biomarkers predict response.

METHODS

Serum-specific IgG4 and IgE (whole peanut and components) from subjects enrolled in the phase 3 Efficacy and Safety of Viaskin Peanut in Children With IgE-Mediated Peanut Allergy study were examined by exploratory univariate and multivariate analyses to determine trajectories and predictors of treatment response, based upon peanut protein eliciting dose (ED) at Month (M) 12 double-blind placebo-controlled food challenge.

RESULTS

Among Viaskin Peanut-treated subjects, peanut sIgG4 significantly increased from baseline through M12 and peanut sIgE peaked at M3 and fell below baseline by M12, with sIgG4 and sIgE peanut components mirroring these trajectories. Placebo subjects had no significant changes. By univariate analysis, M12 peanut sIgG4/sIgE was higher in treatment responders (p < 0.001) and had highest area under the curve (AUC) for predicting ED ≥300 mg and ≥1000 mg (AUC 69.5% and 69.9%, respectively). M12 peanut sIgG4/sIgE >20.1 predicted M12 ED ≥300 mg (80% positive predictive value). The best performing component was Ara h 1 sIgE <15.7 kUA /L (AUC 66.5%). A multivariate model combining Ara h 1 and peanut sIgG4/sIgE had an AUC of 68.2% (ED ≥300 mg) and 67.8% (ED ≥1000 mg).

CONCLUSIONS

Peanut sIgG4 rise most clearly differentiated Viaskin Peanut versus placebo subjects. sIgG4/sIgE ratios >20.1 and the combination of Ara h 1 and peanut sIgG4/sIgE had moderate ability to predict treatment response and could potentially be useful for clinical monitoring. Additional data are needed to confirm these relationships.

Jak out of the box: Targeting Bruton's tyrosine kinase, sialic acid-binding immunoglobulin-like lectin-8, and Janus kinase 1 in food allergy

There has been rapid growth in the field of immunoglobulin E-mediated food allergy therapeutics, with 1 US Food and Drug Administration-approved therapy in 2020 and several others in various stages of investigation. Oral immunotherapy is the approach with the longest track record of study and provides desensitization for most individuals undertaking the therapy. However, the therapy must be maintained for continued clinical protection, and adverse effects of the therapy are frequent. There is a need to improve allergen immunotherapy safety and durability and to provide a treatment that can target multiple food allergies. In this review, we discuss novel adjunct therapies that may improve safety, such as omalizumab, Bruton's tyrosine kinase inhibitors, and agonists of sialic acid-binding immunoglobulin-like lectin-8, which suppress hypersensitivity responses. We also discuss approaches that may improve magnitude or durability of the treatment response, such as dupilumab and Janus kinase 1 inhibitors.

Peanut allergy: risk factors, immune mechanisms, and best practices for oral immunotherapy success

INTRODUCTION

Peanut oral immunotherapy (pOIT) is the only FDA-approved treatment for food allergy and its adoption amongst allergist immunologists and their patients is growing. pOIT is the subject of numerous clinical trials, however, the focus is often on treatment efficacy, safety, and tolerability, rather than identifying patients most likely to benefit from pOIT. Here, we review existing data on the clinical and immunological outcomes of pOIT that inform best practices for pOIT candidate selection.

AREAS COVERED

In this review, we describe the natural history of peanut allergy, summarize immunological and clinical outcomes of pOIT at different ages, discuss the optimization of pOIT in key age groups, and finally suggest an ideal age range at which to initiate pOIT for best outcomes.

EXPERT OPINION

pOIT is currently underutilized by patients and allergist-immunologists. Developing guidelines for selecting appropriate patients and optimizing treatment may help to increase access to pOIT. Many aspects of pOIT need additional study to further our understanding of the optimal timing to start pOIT, with careful consideration to clinical, immunological, and quality of life outcomes.

Targeting type 2 immunity and the future of food allergy treatment

IgE-mediated food allergy affects 6-8% of the population in the United States. Type 2 immune responses are central to the pathogenesis of food allergy, but type 2 CD4+ T cell responses have been found to be heterogeneous in food allergy suggesting a division of labor between Tfh13 and peTH2 cells in promotion of IgE class switching, modulation of intestinal barrier function, and regulation of mast cell expansion. Oral immunotherapy for the treatment of food allergy incompletely targets subsets of type 2 immunity in a transient manner, but new therapeutics targeting different levels of type 2 immunity are in current or planned trials for food allergy. These new treatments and the basis for their use are the focus of this review.

Allergen recognition by specific effector Th2 cells enables IL-2-dependent activation of regulatory T-cell responses in humans

Type 2 allergen-specific T cells are essential for the induction and maintenance of allergies to foods, and Tregs specific for these allergens are assumed to be involved in their resolution. However, it has not been convincingly demonstrated whether allergen-specific Treg responses are responsible for the generation of oral tolerance in humans. We observed that sustained food allergen exposure in the form of oral immunotherapy resulted in increased frequency of Tregs only in individuals with lasting clinical tolerance. We sought to identify regulatory components of the CD4+ T-cell response to food allergens by studying their functional activation over time in vitro and in vivo. Two subsets of Tregs expressing CD137 or CD25/OX40 were identified with a delayed kinetics of activation compared with clonally enriched pathogenic effector Th2 cells. Treg activation was dependent on IL-2 derived from effector T cells. In vivo exposure to peanut in the form of an oral food challenge of allergic subjects induced a delayed and persistent activation of Tregs after initiation of the allergen-specific Th2 response. The novel finding of our work is that a sustained wave of Treg activation is induced by the release of IL-2 from Th2 effector cells, with the implication that therapeutic administration of IL-2 could improve current OIT approaches.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

A clinical focus on oral tolerance in the development, prevention, and management of food allergy

Food allergy impacts up to 10 % of the population and can result in life-threatening anaphylactic reactions. The pathogenesis of food allergy is not entirely understood but the disruption in naturally occurring oral tolerance is presumed to be involved. Research has been directed not only toward prevention of food allergy but on the restoration of oral tolerance by various means including immunotherapy (oral, sublingual, and epicutaneous), as well as adjunctive therapies including biologicals and probiotics. This review paper briefly discusses the involvement of oral tolerance in the pathogenesis of food allergy and how food allergy might be prevented; however, the main focus is on the potential for restoration of oral tolerance with various treatment modalities (oral immunotherapy with and without adjunctive therapies).

T-cell epitope discovery and single-cell technologies to advance food allergy research

There is good evidence for a role of T cells in food allergy, but there is a lack of mechanistic understanding and phenotypic markers of the specific T cells contributing to pathology. Recent technologic advancements have allowed for a new experimental paradigm where we can find and pull out rare antigen-specific T cells and characterize them at the single-cell level. However, studies in infectious disease and broader allergy have shown that these techniques benefit greatly from precisely defined T-cell epitopes. Food allergens have fewer epitopes currently available, but it is growing and promises to overcome this gap. With growing use of this experimental design, it will be important to unbiasedly map T-cell phenotypes across food allergy and look for commonalities and contrasts to other allergic and infectious diseases. Once a pathologic phenotype for T cells has been established, the frequencies of these cells can be monitored with simpler techniques that could be applied to the clinic and used in diagnosis, prediction of treatment responsiveness, and discovery of targets for new treatments.

Oral tolerance and oral immunotherapy for food allergy: Evidence for common mechanisms?

Food allergies affect up to 10% of the US population, can be life-threatening, and have a significant negative impact on quality of life. Delayed dietary introduction of foods in childhood can hinder the induction of oral tolerance, an active regulatory response to foods that prevents the development of food allergy. Some children outgrow their food allergies naturally, while many others have persistent, lifelong food allergy for which there are few therapeutic options. Oral immunotherapy (OIT) is a therapeutic approach of giving increasing amounts of food to attempt to desensitize the allergic individual. In this review, we focus on the immune mechanisms common to oral tolerance and response to oral immunotherapy, with the objective of determining whether true tolerance can be achieved after food allergy has been established.

Immunotherapy: State-of-the-art review of therapies and theratypes

Through its disease-modifying potential, immunotherapy is the keystone to curing allergic diseases. Allergen immunotherapy, applied for more than a century, is currently supported by novel modalities such as mAb-based therapies or small molecules targeting the key nodes of the allergic inflammation network. In this review, a summary of the most significant advances in immunotherapy is presented, addressing not only novel approaches to stratifying patients but also major controlled clinical trials and real-world evidence that strengthen the role of immunotherapy in the treatment of allergies.

Immunology of allergen immunotherapy

Allergen immunotherapy (AIT) is the only disease-modifying therapy for allergic disease. Through repeated inoculations of low doses of allergen-either as whole proteins or peptides-patients can achieve a homeostatic balance between inflammatory effectors induced and/or associated with allergen contact, and mediators of immunologic non-responsiveness, potentially leading to sustained clinical improvements. AIT for airborne/respiratory tract allergens and insect venoms have traditionally been supplied subcutaneously, but other routes and modalities of administration can also be effective. Despite differences of allergen administration, there are some similarities of immunologic responses across platforms, with a general theme involving the restructuring and polarization of adaptive and innate immune effector cells. Here we review the immunology of AIT across various delivery platforms, including subcutaneous, sublingual, epicutaneous, intradermal, and intralymphatic approaches, emphasizing shared mechanisms associated with achieving immunologic non-responsiveness to allergen.

New Mechanistic Advances in FcεRI-Mast Cell-Mediated Allergic Signaling

Mast cells originate from the CD34⁺/CD117⁺ hematopoietic progenitors in the bone marrow, migrate into circulation, and ultimately mature and reside in peripheral tissues. Microbiota/metabolites and certain immune cells (e.g., Treg cells) play a key role in maintaining immune tolerance. Cross-linking of allergen-specific IgE on mast cells activates the high-affinity membrane-bound receptor FcεRI, thereby initiating an intracellular signal cascade, leading to degranulation and release of pro-inflammatory mediators. The intracellular signal transduction is intricately regulated by various kinases, transcription factors, and cytokines. Importantly, multiple signal components in the FcεRI-mast cell–mediated allergic cascade can be targeted for therapeutic purposes. Pharmacological interventions that include therapeutic antibodies against IgE, FcεRI, and cytokines as well as inhibitors/activators of several key intracellular signaling molecues have been used to inhibit allergic reactions. Other factors that are not part of the signal pathway but can enhance an individual’s susceptibility to allergen stimulation are referred to as cofactors. Herein, we provide a mechanistic overview of the FcεRI-mast cell–mediated allergic signaling. This will broaden our scope and visions on specific preventive and therapeutic strategies for the clinical management of mast cell–associated hypersensitivity reactions.

Biomarkers and mechanisms of tolerance induction in food allergic patients drive new therapeutic approaches

Immunotherapy for food-allergic patients has been effective in inducing desensitization in some populations, but long-term tolerance has remained an elusive target. A challenge facing our field is how to differentiate immune markers that are impacted by immunotherapy from those that are critical biomarkers of tolerance. Data from recent clinical trials have identified several biomarkers and mechanisms for achieving tolerance. These biomarkers include younger age, lower food-specific IgE, lower food component-specific IgE, specific linear epitope profiles, and subsets of food-specific CD4+ T cells. Additional biomarkers under investigation for their relevance in tolerance induction include TCR repertoires, gastrointestinal and skin microbiome, and local tissue immunity. This mini-review highlights recent advances in understanding biomarkers and mechanisms of tolerance induction in food immunotherapy and how these are influencing clinical trial development.

IgE-Mediated food allergy: Current diagnostic modalities and novel biomarkers with robust potential

Food allergy (FA) is a serious public health issue afflicting millions of people globally, with an estimated prevalence ranging from 1-10%. Management of FA is challenging due to overly restrictive diets and the lack of diagnostic approaches with high accuracy and prediction. Although measurement of serum-specific antibodies combined with patient medical history and skin prick test is a useful diagnostic tool, it is still an imprecise predictor of clinical reactivity with a high false-positive rate. The double-blind placebo-controlled food challenge represents the gold standard for FA diagnosis; however, it requires large healthcare and involves the risk of acute onset of allergic reactions. Improvement in our understanding of the molecular mechanism underlying allergic disease pathology, development of omics-based methods, and advances in bioinformatics have boosted the generation of a number of robust diagnostic biomarkers of FA. In this review, we discuss how traditional diagnostic modalities guide appropriate diagnosis and management of FA in clinical practice, as well as uncover the potential of the latest biomarkers for the diagnosis, monitoring, and prediction of FA. We also raise perspectives for precise and targeted medical intervention to fill the gap in the diagnosis of FA.