Past, present, and future of anti-IgE biologics

Comparison of clinical traits for seasonal and perennial allergic rhinitis during allergen exposure

Background: Allergic rhinitis (AR) is traditionally subdivided into seasonal AR (SAR) and perennial AR (PAR) according to the type of allergen and the occurrence of symptoms during the year. There are currently no reports on the comparison of trait profiles for SAR and PAR during the allergen exposure. Purpose: The purpose of this study was to analyze the clinical characteristics of SAR and PAR during respective allergen exposure periods to provide valuable information for the development of treatment strategies. Methods: This study was performed between August 1, 2021, and January 31, 2022, in the Department of Allergy, Beijing Tongren Hospital. We continuously included diagnosed SAR and PAR outpatients who volunteered to participate in the survey. A questionnaire with regard to medical history, severity of symptoms, and diagnosis and treatment status was collected. Results: A total of 296 patients with SAR and 448 with PAR were finally recruited. Patients with SAR had more severe rhinorrhea compared with patients with PAR (p < 0.001), whereas there was no statistically significant difference in the severity of itching, sneezing, and congestion between the two entities (p ≥ 0.05). Both the gritty and watery eyes of patients with SAR were noticeably more severe than those of patients with PAR (PTotal Ocular Symptom Score [PTOSS] < 0.001). AR symptom severity is mainly associated with the comorbid allergic conjunctivitis (odds ratio 1.94 [95% confidence interval, 1.21-3.09]). SAR patients and PAR patients show no statistically significant differences in terms of their frequency of visits, annual expenditure, and choice of medication treatment for AR (p > 0.05). The overall control under standard medication of both patients with PAR and those with SAR is not ideal, especially in SAR. Conclusion: The current cross-sectional study demonstrated that the patients with SAR exhibited more severe overall clinical symptoms than those with PAR, especially nasal rhinorrhea and gritty and watery eyes. Both of the two disease entities have poor control under standardized medication treatment, especially in SAR. Further multicenter longitudinal studies that involve larger and more diverse populations should be conducted to provide a more accurate and comprehensive understanding of the condition.

Real-World Effectiveness of Omalizumab in Chronic Urticaria: A Clinical Observational Study

INTRODUCTION

The purpose of this study was to assess the clinical effectiveness and safety profile of omalizumab as a therapeutic intervention for chronic urticaria (CU).

METHODS

From March 1, 2023, to September 30, 2023, data on a cohort comprising 96 patients with CU, who underwent treatment with omalizumab at our medical institution's allergy clinic, were systematically compiled. Subsequent to the administration of omalizumab, the therapeutic efficacy was assessed utilizing the 7-day urticaria activity score and the urticaria control test.

RESULTS

Based on the statistical analysis, the mean duration of therapeutic intervention was 2.4 ± 1.3 months, with a corresponding mean cumulative dosage of 765 ± 450 mg. Of the subset of 42 patients with CU who were subjected to a follow-up period exceeding 3 months, it was observed that the treatment led to complete symptom remission, and no instances of recurrence were documented. Notably, there were statistically significant differences in the treatment duration and the cumulative dosage between patients who experienced co-morbid conditions and those who did not (p < 0.01, 95% CI: 0.280-1.326; p < 0.01, 95% CI: 0.597-2.997). Furthermore, there were significant differences in the treatment duration and cumulative dosage between patients in the combined allergic rhinitis group and those in the non-combined allergic rhinitis group (p < 0.01, 95% CI: 0.204-1.305; p = 0.01, 95% CI: 0.326-2.860).

CONCLUSION

Omalizumab demonstrates efficacy in the management of CU among Chinese patients by exerting effective symptom control and facilitating the regression of skin lesions. The assessment of its therapeutic efficacy typically requires a 12-week treatment period. Moreover, the co-occurrence of CU with other allergic disorders serves as a pertinent consideration for the adjustment of omalizumab dosing regimens.

Generation of a virus-like particles based vaccine against IgE

BACKGROUND

Anti-IgE immunotherapy with monoclonal antibodies represents a breakthrough in treatment of severe allergic diseases. However, drawbacks such as short half-life and high price are not negligible. Our objective is to develop an anti-IgE vaccine based on virus-like particles (VLPs) which can induce long-lasting neutralizing IgG anti-IgE antibodies reducing allergic responses without causing intrinsic mast cell activation due to IgE cross-linking.

METHODS

The vaccines were made by chemically coupling three synthetic mouse IgE-Fc fragments to plant-derived immunologically optimized CuMVTT VLPs. The immunogenicity of the vaccines was tested by immunizing naive or allergic mice either with the coupled vaccines or the VLP control followed by systemic or local allergen challenge.

RESULTS

Mice immunized with the vaccines exhibited high titers of anti-IgE antibodies in the sera and high levels of anti-IgE secreting plasma cells in lymphoid organs. Moreover, free IgE in serum were reduced by the induced anti-IgE antibodies; therefore, less IgE was bound to FcεRI on the surface of basophils. In line with these reduced IgE levels on effector cells after vaccination, immunized mice were protected from challenge with allergens. Importantly, despite presence of anti-IgE antibodies, no signs of acute or chronic allergic response were seen in immunized allergic mice.

CONCLUSION

The generated vaccines can effectively induce anti-IgE antibodies that did not cause allergic responses in sensitized mice but were able to decrease the level of free and cell bound IgE and protected sensitized animals from allergic responses upon allergen challenge.

Association between energy-adjusted dietary inflammatory index and total immunoglobulin E: A cross-sectional study

The relationship between a pro-inflammatory diet, assessed by the dietary inflammatory index (DII), and allergic diseases has attracted attention. However, the association between DII and immunoglobulin E (IgE) remains uncertain. We aim to investigate the association between energy-adjusted DII (E-DII) and total IgE. We analyzed data from the 2005 to 2006 National Health and Nutrition Examination Survey. The relationship between E-DII and total IgE was assessed using linear regression and logistic regression analysis. Meanwhile, we conducted a subgroup analysis stratified by body mass index (BMI) and analyzed the mediating role of BMI. We included 3614 adult participants. After controlling for confounding factors, there was no statistical association between E-DII and total IgE (β 0.023, 95% CI -0.01 to 0.057, p = .173) and the risk of high total IgE (OR 1.036, 95% CI 0.977 to 1.099, p = .233). We conducted subgroup analysis stratified by BMI. After controlling for confounding factors, only in overweight groups, E-DII was statistically associated with total IgE (β 0.076, 95% CI 0.017 to 0.135, p = .012) and the risk of high total IgE (OR 1.124, 95% CI 1.015 to 1.246, p = .025). Generalized additive models and smooth curve fittings showed a positive linear relationship between E-DII and total IgE in overweight participants. No statistical association was noted for the mediation effect of BMI on the association between E-DII and total IgE in the overweight group (p = .23). Overweight participants with higher E-DII were potentially at risk of elevated total IgE.

Mast Cell-Targeting Therapies in Mast Cell Activation Syndromes

PURPOSE OF REVIEW

Provide an overview of the expanding landscape of mast cell (MC)-targeting treatments in mast cell activation syndromes (MCAS).

RECENT FINDINGS

Tyrosine-kinase inhibitors (TKIs) targeting wild-type and mutated KIT can efficiently induce MC depletion. Avapritinib and midostaurin can also temper IgE-mediated degranulation. Avapritinib has been recently approved by the FDA for the treatment of indolent systemic mastocytosis (ISM). Targeting activation pathways and inhibitory receptors is a promising therapeutic frontier. Recently, the anti Siglec-8 antibody lirentelimab showed promising results in ISM. MCAS is a heterogeneous disorder demanding a personalized therapeutic approach and, especially when presenting as anaphylaxis, has not been formally captured as outcome in prospective clinical trials with TKI. Long-term safety of TKI needs to be addressed. New drugs under investigation in diseases in which non-neoplastic MCs play a pivotal role can provide important inputs to identify new efficient and safe treatments for MCAS.

Effects of biological therapies on patients with Type-2 high asthma and comorbid obesity

Over 20 million adults and 6 million children in the United States (US) have asthma, a chronic respiratory disease characterized by airway inflammation, bronchoconstriction, and mucus hypersecretion. Obesity, another highly prevalent disease in the US, is a major risk factor for asthma and a significant cause of diminished asthma control, increased submucosal eosinophilia, and reduced quality of life. A large subgroup of these patients experiences severe symptoms and recurrent exacerbations despite maximal dosage of standard asthma therapies. In the past two decades, the development of biological therapies has revolutionized the field and advanced our understanding of type 2 inflammatory biomarkers. However, patients with obesity and comorbid asthma are not principally considered in clinical trials of biologics. Large landmark cluster analyses of patients with asthma have consistently identified specific asthma phenotypes that associate with obesity but may be differentiated by age of asthma onset and inflammatory cell profiles in sputum. These patterns suggest that biologic processes driving asthma pathology are heterogenous among patients with obesity. The biological mechanisms driving pathology in patients with asthma and comorbid obesity are not well understood and likely multifactorial. Future research needs to be done to elicit the cellular and metabolic functions in the relationship of obesity and asthma to yield the best treatment options for this multiplex condition. In this review, we explore the key features of type 2 inflammation in asthma and discuss the effectiveness, safety profile, and research gaps regarding the currently approved biological therapies in asthma patients with obesity.

Autoreactive IgE: Pathogenic role and therapeutic target in autoimmune diseases

Autoimmunity is the break of tolerance to self-antigens that leads to organ-specific or systemic diseases often characterized by the presence of pathogenic autoreactive antibodies (AAb) produced by plasmablast and/or plasma cells. AAb are prevalent in the general population and not systematically associated with clinical symptoms. In contrast, in some individuals, these AAb are pathogenic and drive the development of signs and symptoms of antibody-mediated autoimmune diseases (AbAID). AAb production, isotype profiles, and glycosylations are promoted by pro-inflammatory triggers linked to genetic, environmental, and hormonal parameters. Recent evidence supports a role for pathogenic AAb of the IgE isotype in a number of AbAID. Autoreactive IgE can drive the activation of mast cells, basophils, and other types of FcεRI-bearing cells and may play a role in promoting autoantibody production and other pro-inflammatory pathways. In this review, we discuss the current knowledge on the pathogenicity of autoreactive IgE in AbAID and their status as therapeutic targets. We also highlight unresolved issues including the need for assays that reproducibly quantify IgE AAbs, to validate their diagnostic and prognostic value, and to further study their pathophysiological contributions to AbAID.

Development of a Cytotoxic Antibody-Drug Conjugate Targeting Membrane Immunoglobulin E-Positive Cells

High numbers of membrane immunoglobulin E (IgE)-positive cells are characteristic of allergic conditions, atopic dermatitis, or IgE myeloma. Antibodies targeting the extracellular membrane-proximal domain of the membranous IgE-B-cell receptor (BCR) fragment can be used for specific depletion of IgE-BCR-positive cells. In this study, we derivatized such an antibody with a toxin and developed an antibody-drug conjugate (ADC) that showed strong cytotoxicity for an IgE-positive target cell line. Site-specific conjugation with maleimidocaproyl-valine-citrulline-p-aminobenzoyloxycarbonyl-monomethyl-auristatin E via a newly introduced single cysteine residue was used to prepare a compound with a drug-antibody ratio of 2 and favorable biophysical properties. The antibody was rapidly taken up by the target cells, showing almost complete internalization after 4 h of treatment. Its cytotoxic effect was potentiated upon cross-linking mediated by an anti-human IgG F(ab')2 fragment. Because of its fast internalization and strict target specificity, this antibody-drug conjugate presents a valuable starting point for the further development of an anti-IgE cell-depleting agent, operating by the combined action of receptor cross-linking and toxin-mediated cytotoxicity.

Fc-Engineered Therapeutic Antibodies: Recent Advances and Future Directions

Monoclonal therapeutic antibodies have revolutionized the treatment of cancer and other diseases. Fc engineering aims to enhance the effector functions or half-life of therapeutic antibodies by modifying their Fc regions. Recent advances in the Fc engineering of modern therapeutic antibodies can be considered the next generation of antibody therapy. Various strategies are employed, including altering glycosylation patterns via glycoengineering and introducing mutations to the Fc region, thereby enhancing Fc receptor or complement interactions. Further, Fc engineering strategies enable the generation of bispecific IgG-based heterodimeric antibodies. As Fc engineering techniques continue to evolve, an expanding portfolio of Fc-engineered antibodies is advancing through clinical development, with several already approved for medical use. Despite the plethora of Fc-based mutations that have been analyzed in in vitro and in vivo models, we focus here in this review on the relevant Fc engineering strategies of approved therapeutic antibodies to finetune effector functions, to modify half-life and to stabilize asymmetric bispecific IgGs.

Research Advances in Mast Cell Biology and Their Translation Into Novel Therapies for Anaphylaxis

Anaphylaxis is an acute, potentially life-threatening systemic allergic reaction for which there are no known reliable preventative therapies. Its primary cell mediator, the mast cell, has several pathophysiologic roles and functions in IgE-mediated reactions that continue to be poorly understood. Recent advances in the understanding of allergic mechanisms have identified novel targets for inhibiting mast cell function and activation. The prevention of anaphylaxis is within reach with new drugs that could modulate immune tolerance, mast cell proliferation and differentiation, and IgE regulation and production. Several US Food and Drug Administration-approved drugs for chronic urticaria, mastocytosis, and cancer are also being repurposed to prevent anaphylaxis. New therapeutics have not only shown promise in potential efficacy for preventing IgE-mediated reactions, but in some cases, they are able to inform us about mast cell mechanisms in vivo. This review summarizes the most recent advances in the treatment of anaphylaxis that have arisen from new pharmacologic tools and our current understanding of mast cell biology.

Antibody-mediated regulation of basophils: emerging views and clinical implications

An increasing number of human diseases, including allergies, infections, inflammation, and cancer, involve roles for basophils. Traditionally viewed as the rarest leukocytes that are present only in the circulation, basophils have recently emerged as important players in systemic as well as tissue-specific immune responses. Their functions are regulated by immunoglobulins (Igs), and this enables basophils to integrate diverse adaptive and innate immunity signals. IgE is well known to regulate basophil responses in the context of type 2 immunity and allergic inflammation; however, growing evidence shows that IgG, IgA, and IgD also shape specific aspects of basophil functions relevant to many human diseases. We discuss recent mechanistic advances underpinning antibody-mediated basophil responses and propose strategies for the treatment of basophil-associated disorders.

Degranulation of Mast Cells as a Target for Drug Development

Mast cells act as key effector cells of inflammatory responses through degranulation. Mast cell degranulation is induced by the activation of cell surface receptors, such as FcεRI, MRGPRX2/B2, and P2RX7. Each receptor, except FcεRI, varies in its expression pattern depending on the tissue, which contributes to their differing involvement in inflammatory responses depending on the site of occurrence. Focusing on the mechanism of allergic inflammatory responses by mast cells, this review will describe newly identified mast cell receptors in terms of their involvement in degranulation induction and patterns of tissue-specific expression. In addition, new drugs targeting mast cell degranulation for the treatment of allergy-related diseases will be introduced.

Clorfl86/RHEX Is a Negative Regulator of SCF/KIT Signaling in Human Skin Mast Cells

Mast cells (MCs) are key effector cells in allergic and inflammatory diseases, and the SCF/KIT axis regulates most aspects of the cells' biology. Using terminally differentiated skin MCs, we recently reported on proteome-wide phosphorylation changes initiated by KIT dimerization. C1orf186/RHEX was revealed as one of the proteins to become heavily phosphorylated. Its function in MCs is undefined and only some information is available for erythroblasts. Using public databases and our own data, we now report that RHEX exhibits highly restricted expression with a clear dominance in MCs. While expression is most pronounced in mature MCs, RHEX is also abundant in immature/transformed MC cell lines (HMC-1, LAD2), suggesting early expression with further increase during differentiation. Using RHEX-selective RNA interference, we reveal that RHEX unexpectedly acts as a negative regulator of SCF-supported skin MC survival. This finding is substantiated by RHEX's interference with KIT signal transduction, whereby ERK1/2 and p38 both were more strongly activated when RHEX was attenuated. Comparing RHEX and capicua (a recently identified repressor) revealed that each protein preferentially suppresses other signaling modules elicited by KIT. Induction of immediate-early genes strictly requires ERK1/2 in SCF-triggered MCs; we now demonstrate that RHEX diminution translates to this downstream event, and thereby enhances NR4A2, JUNB, and EGR1 induction. Collectively, our study reveals RHEX as a repressor of KIT signaling and function in MCs. As an abundant and selective lineage marker, RHEX may have various roles in the lineage, and the provided framework will enable future work on its involvement in other crucial processes.

IgE, IgE Receptors and Anti-IgE Biologics: Protein Structures and Mechanisms of Action

The evolution of IgE in mammals added an extra layer of immune protection at body surfaces to provide a rapid and local response against antigens from the environment. The IgE immune response employs potent expulsive and inflammatory forces against local antigen provocation, at the risk of damaging host tissues and causing allergic disease. Two well-known IgE receptors, the high-affinity FcεRI and low-affinity CD23, mediate the activities of IgE. Unlike other known antibody receptors, CD23 also regulates IgE expression, maintaining IgE homeostasis. This mechanism evolved by adapting the function of the complement receptor CD21. Recent insights into the dynamic character of IgE structure, its resultant capacity for allosteric modulation, and the potential for ligand-induced dissociation have revealed previously unappreciated mechanisms for regulation of IgE and IgE complexes. We describe recent research, highlighting structural studies of the IgE network of proteins to analyze the uniquely versatile activities of IgE and anti-IgE biologics.

Drug delivery targets and strategies to address mast cell diseases

INTRODUCTION

Current and developing mast cell therapeutics are reliant on small molecule drugs and biologics, but few are truly selective for mast cells. Most have cellular and disease-specific limitations that require innovation to overcome longstanding challenges to selectively targeting and modulating mast cell behavior. This review is designed to serve as a frame of reference for new approaches that utilize nanotechnology or combine different drugs to increase mast cell selectivity and therapeutic efficacy.

AREAS COVERED

Mast cell diseases include allergy and related conditions as well as malignancies. Here, we discuss the targets of existing and developing therapies used to treat these disease pathologies, classifying them into cell surface, intracellular, and extracellular categories. For each target discussed, we discuss drugs that are either the current standard of care, under development, or have indications for potential use. Finally, we discuss how novel technologies and tools can be used to take existing therapeutics to a new level of selectivity and potency against mast cells.

EXPERT OPINION

There are many broadly and very few selectively targeted therapeutics for mast cells in allergy and malignant disease. Combining existing targeting strategies with technology like nanoparticles will provide novel platforms to treat mast cell disease more selectively.

Chronic spontaneous urticaria: Focus on pathophysiology to unlock treatment advances

Chronic spontaneous urticaria (CSU) is a debilitating skin disease characterized by intensely itchy wheals, angioedema, or both. Symptoms recur spontaneously, on a near-daily basis, over >6 weeks; many patients experience flare-ups over several years and, consequently, reduced quality of life. Differences between the inflammatory profiles of the skin of CSU patients (wheals and nonlesional sites) and healthy controls indicate that key drivers such as mast cells, eosinophils, and basophils interact, release vasoactive mediators, and prime the skin, leaving patients predisposed to symptoms. Many cytokines and chemokines involved in these inflammatory networks and their corresponding intracellular signaling cascades have been identified. These insights informed the development of therapies such as omalizumab, dupilumab, and Bruton's tyrosine kinase (BTK) inhibitors, marking a renewed focus on pathogenesis in CSU clinical research. Despite progress, current therapies provide symptomatic control but do not appear to redress the inflammatory balance in the skin permanently. A deeper understanding of CSU pathogenesis will permit a more targeted approach to developing novel treatments with curative intent. Here, we review what is known about the pathogenesis of CSU and consider how this can be used to identify rational targets to improve patient care further.

A Decade of Clinical Advances in Chronic Rhinosinusitis: 2012-2022

The field of chronic rhinosinusitis (CRS) is constantly evolving. In the past 10 years, key advancements in basic and translational research as well as clinical studies have improved our understanding and management of CRS. Notably, treatment options have expanded to include novel therapeutic drugs, devices, and surgical techniques. Assessments of patient symptoms and their impact on quality of life have become more standardized. Progress has also been made in both determining the true prevalence of CRS and recognizing comorbidities that can impact CRS severity. Practice guidelines have also shifted from expert opinion to more data-driven analyses. This review highlights major clinical advancements made in the field of CRS over the past 10 years as well as identifies current gaps in knowledge that can form the basis for new areas of study over the next decade.

Current evaluation and management of patients with chronic rhinosinusitis and nasal polyps

INTRODUCTION

A clear understanding of the pathophysiology of chronic rhinosinusitis with nasal polyps (CRSwNP) and its close association with other airway pathologies, especially asthma, helps to comprehend the concept of the united airway and the importance of a multidisciplinary approach and the actual roll of biologic therapy.

AREAS COVERED

This expert review is the synthesis of a working group on the current state of the art of the evaluation and management of CRSwNP. A thorough analysis of the literature has been conducted for the latest studies and results, specially the European (EPOS 2020) and American (ICAR-RS 2021) guidelines.

EXPERT OPINION

The roles of optimal medical treatment and indications for surgery are becoming clearer, but much research is still needed regarding the extent and radicality when surgery is indicated. The main objectives of this review were to provide a clear and updated description of treatments, their indication, follow-up, and response criteria. These steps are considering the broad spectrum of inflammation endophenotypes and the biologic therapy available. Understanding the role and limitations of each specialty is key for providing greatest benefit to the patient.

Ligelizumab impairs IgE ‐binding to plasmacytoid dendritic cells more potently than omalizumab and restores IFN ‐α production and FOXP3 + Treg generation

BACKGROUND

Ligelizumab is an anti-IgE monoclonal antibody binding IgE with higher affinity than omalizumab that is under clinical investigation for several IgE-mediated diseases. We previously showed that omalizumab removes IgE bound to FcεRI on plasmacytoid dendritic cells (pDCs) and restores their ability to produce IFN-α and regulatory T cells (Tregs). The aim of this work is to investigate the capacity of ligelizumab to regulate functional properties of pDCs in comparison with omalizumab.

METHODS

pDCs were isolated from atopic donors and IgE was detached from FcεRI on pDCs with designed ankyrin repeat protein (DARPin) bi53-79. pDCs were resensitized with IgE alone or in the presence of ligelizumab or omalizumab prior to IgE-FcεRI crosslinking and Toll-like receptor 9 (TLR9) stimulation. Flow cytometry, ELISA, coculture experiments and intranuclear staining were performed to determine cytokine production and Treg generation. An antigen-specific model of resensitization and IgE-crosslinking was also performed.

RESULTS

The levels of serum total free IgE show a non-linear positive correlation with the frequency of IgE⁺ pDCs displaying IgE bound to FcεRI within the 43 individual donors included in the study. Ligelizumab displays stronger capacity than omalizumab to block the binding of free IgE to FcεRI on human pDCs, resulting in a greater restoration of TLR9-L-induced IFN-α production. Ligelizumab also restores the ability of pDCs to generate FOXP3⁺ Tregs as previously reported for omalizumab.

CONCLUSIONS

The uncovered novel molecular mechanisms of ligelizumab to regulate functional properties of pDCs from atopic donors might have important clinical implications for anti-IgE treatments in different IgE-mediated diseases.

Therapeutical Targets in Allergic Inflammation

From the discovery of IgE to the in-depth characterization of Th2 cells and ILC2, allergic inflammation has been extensively addressed to find potential therapeutical targets. To date, omalizumab, an anti-IgE monoclonal antibody, and dupilumab, an anti-IL-4 receptor α monoclonal antibody, represent two pillars of biologic therapy of allergic inflammation. Their increasing indications and long-term follow-up studies are shaping the many different faces of allergy. At the same time, their limitations are showing the intricate pathogenesis of allergic diseases.

The SCF/KIT axis in human mast cells: Capicua acts as potent KIT repressor and ERK predominates PI3K

BACKGROUND

The SCF/KIT axis regulates nearly all aspects of mast cell (MC) biology. A comprehensive view of SCF-triggered phosphorylation dynamics is lacking. The relationship between signaling modules and SCF-supported functions likewise remains ill-defined.

METHODS

Mast cells were isolated from human skin; upon stimulation by SCF, global phosphoproteomic changes were analyzed by LC-MS/MS and selectively validated by immunoblotting. MC survival was inspected by YoPro; BrdU incorporation served to monitor proliferation. Gene expression was quantified by RT-qPCR and cytokines by ELISA. Pharmacological inhibitors were supplemented by ERK1 and/or ERK2 knockdown. CIC translocation and degradation were studied in nuclear and cytoplasmic fractions. CIC's impact on KIT signaling and function was assessed following RNA interference.

RESULTS

≈5400 out of ≈10,500 phosphosites experienced regulation by SCF. The MEK/ERK cascade was strongly induced surpassing STAT5 > PI3K/Akt > p38 > JNK. Comparison between MEK/ERK's and PI3K's support of basic programs (apoptosis, proliferation) revealed equipotency between modules. In functional outputs (gene expression, cytokines), ERK was the most influential kinase. OSM and LIF production was identified in skin MCs. Strikingly, SCF triggered massive phosphorylation of a protein not associated with KIT previously: CIC. Phosphorylation was followed by CIC's cytoplasmic appearance and degradation, the latter sensitive to protease but not preoteasome inhibition. Both shuttling and degradation were ERK-dependent. Conversely, CIC-siRNA facilitated KIT signaling, functional outputs, and survival.

CONCLUSION

The SCF/KIT axis shows notable strength in MCs, and MEK/ERK as most prominent module. An inhibitory circuit exists between KIT and CIC. CIC stabilization in MCs may turn out as a therapeutic option to interfere with allergic and MC-driven diseases.

Biologics as novel therapeutics for the treatment of allergy: Challenges and opportunities

Over the last 4 decades there has been a significant global increase in the incidence and prevalence of IgE-mediated allergy. Although much progress has been made in the management of allergy via patient education, pharmacotherapy and immunomodulatory treatment regimens, significant unmet need remains. Advancements in our knowledge base surrounding the type 2 immune response, production of IgE and maintenance of immunological memory has led the field to explore targeted intervention of allergic pathways using monoclonal antibodies (mAbs). Intervention at various stages of the allergic cascade offers the opportunity to prevent initiation and/or maintenance of the type 2 immune response and effectively provide therapeutic benefit to patients. Furthermore, a better understanding of the protective mechanisms involved in allergen specific immunotherapy (AIT) has led us to appreciate the interplay of immunoglobulins in the allergic response, specifically the benefit in shifting the IgG:IgE ratio in favor of functionally relevant blocking IgG. Thus, treatments that lower IgE or boost IgG with the ability to outcompete IgE binding to allergen also present a favorable approach in the treatment of allergy. In this short review we discuss and highlight recent advances in the use of biologics to treat severe allergy, highlighting the key challenges but also the significant opportunities and advances to date.

The rationale for development of ligelizumab in food allergy

Food allergy (FA) is a growing healthcare problem worldwide and the rising prevalence in many countries can be attributed to lifestyle, environmental, and nutritional changes. Immunoglobulin E (IgE)-mediated FA is the most common form of FA affecting approximately 3%-10% of adults and 8% of children across the globe. Food allergen-induced immediate hypersensitivity reactions mediated by IgE and high-affinity IgE receptor (FcεRI) complexes on mast cells and basophils are a major hallmark of the disease. FA can affect several aspects of health-related quality of life and impose a substantial financial burden on patients and healthcare systems. Although currently there is one United States Food and Drug Administration (FDA) and European Medicines Agency (EMA)-approved treatment for peanut allergy (Palforzia), the main treatment approaches are based on allergen avoidance and symptom management. Thus, there is an urgent need for more effective and ideally disease-modifying strategies. Given the crucial role of IgE in FA, anti-IgE monoclonal antibodies are considered promising therapeutic agents. Talizumab was the first humanized anti-IgE antibody to demonstrate substantial protection against allergic reactions from accidental peanut exposure by substantially increasing the peanut reactivity threshold on oral food challenge. However, development of talizumab was discontinued and further trials were performed using omalizumab. In double-blind, Phase 2, placebo-controlled trials in patients with multi-FAs, sustained dosing with omalizumab, or omalizumab in combination with oral immunotherapy, enabled rapid desensitization to multiple trigger foods. In this review, we describe the development of ligelizumab (a derivative of talizumab), a next generation, humanized monoclonal anti-IgE antibody, its existing clinical evidence, and its potential in the management of FA. When compared with omalizumab, ligelizumab binds with ∼88-fold higher affinity for human IgE and recognizes a different epitope that substantially overlaps with the binding site of FcεRI. These properties translate into a high potency to block IgE/FcεRI signaling in both in vitro and in vivo studies. Given its efficient suppression of IgE levels, good safety and pharmacokinetic/pharmacodynamic profile, ligelizumab clearly warrants further studies for the potential management of FA.

IgE-neutralizing UB-221 mAb, distinct from omalizumab and ligelizumab, exhibits CD23-mediated IgE downregulation and relieves urticaria symptoms

Over the last 2 decades, omalizumab is the only anti-IgE antibody that has been approved for asthma and chronic spontaneous urticaria (CSU). Ligelizumab, a higher-affinity anti-IgE mAb and the only rival viable candidate in late-stage clinical trials, showed anti-CSU efficacy superior to that of omalizumab in phase IIb but not in phase III. This report features the antigenic-functional characteristics of UB-221, an anti-IgE mAb of a newer class that is distinct from omalizumab and ligelizumab. UB-221, in free form, bound abundantly to CD23-occupied IgE and, in oligomeric mAb-IgE complex forms, freely engaged CD23, while ligelizumab reacted limitedly and omalizumab stayed inert toward CD23; these observations are consistent with UB-221 outperforming ligelizumab and omalizumab in CD23-mediated downregulation of IgE production. UB-221 bound IgE with a strong affinity to prevent FcԑRI-mediated basophil activation and degranulation, exhibiting superior IgE-neutralizing activity to that of omalizumab. UB-221 and ligelizumab bound cellular IgE and effectively neutralized IgE in sera of patients with atopic dermatitis with equal strength, while omalizumab lagged behind. A single UB-221 dose administered to cynomolgus macaques and human IgE (ε, κ)-knockin mice could induce rapid, pronounced serum-IgE reduction. A single UB-221 dose administered to patients with CSU in a first-in-human trial exhibited durable disease symptom relief in parallel with a rapid reduction in serum free-IgE level.

Suppressing Immune Responses Using Siglec Ligand-Decorated Anti-receptor Antibodies

The sialic acid-binding immunoglobulin-type lectins (Siglecs) are expressed predominantly on white blood cells and participate in immune cell recognition of self. Most Siglecs contain cytoplasmic inhibitory immunoreceptor tyrosine-based inhibitory motifs characteristic of inhibitory checkpoint co-receptors that suppress cell signaling when they are recruited to the immunological synapse of an activating receptor. Antibodies to activatory receptors typically activate immune cells by ligating the receptors on the cell surface. Here, we report that the conjugation of high affinity ligands of Siglecs to antibodies targeting activatory immune receptors can suppress receptor-mediated activation of immune cells. Indeed, B-cell activation by antibodies to the B-cell receptor IgD is dramatically suppressed by conjugation of anti-IgD with high affinity ligands of a B-cell Siglec CD22/Siglec-2. Similarly, degranulation of mast cells induced by antibodies to IgE, which ligate the IgE/FcεR1 receptor complex, is suppressed by conjugation of anti-IgE to high affinity ligands of a mast cell Siglec, CD33/Siglec-3 (CD33L). Moreover, the anti-IgE-CD33L suppresses anti-IgE-mediated systemic anaphylaxis of sensitized humanized mice and prevents anaphylaxis upon subsequent challenge with anti-IgE. The results demonstrate that attachment of ligands of inhibitory Siglecs to anti-receptor antibodies can suppress the activation of immune cells and modulate unwanted immune responses.

Metformin Alleviates Airway Hyperresponsiveness in a Mouse Model of Diet-Induced Obesity

Obese asthma is a unique phenotype of asthma characterized by non-allergic airway hyperresponsiveness (AHR) and inflammation which responds poorly to standard asthma therapy. Metformin is an oral hypoglycemic drug with insulin-sensitizing and anti-inflammatory properties. The objective of the current study was to test the effect of metformin on AHR in a mouse model of diet-induced obesity (DIO). We fed 12-week-old C57BL/6J DIO mice with a high fat diet for 8 weeks and treated them with either placebo (control, n = 10) or metformin (n = 10) added in drinking water (300 mg/kg/day) during the last 2 weeks of the experiment. We assessed AHR, metabolic profiles, and inflammatory markers after treatments. Metformin did not affect body weight or fasting blood glucose, but significantly reduced serum insulin (p = 0.0117). Metformin reduced AHR at 30 mg/ml of methacholine challenge (p = 0.0052) without affecting baseline airway resistance. Metformin did not affect circulating white blood cell counts or lung cytokine mRNA expression, but modestly decreased circulating platelet count. We conclude that metformin alleviated AHR in DIO mice. This finding suggests metformin has the potential to become an adjuvant pharmacological therapy in obese asthma.

Therapeutic Potential for Intractable Asthma by Targeting L-Type Amino Acid Transporter 1

Bronchial asthma is a chronic disease characterized by airway inflammation, obstruction, and hyperresponsiveness. CD4⁺ T cells, particularly T helper (Th) 2 cells, and their specific cytokines are important mediators in asthma pathogenesis. However, it has been established that Th subsets, other than Th2, as well as various cell types, including innate lymphoid cells (ILCs), significantly contribute to the development of allergic inflammation. These cells require facilitated amino acid uptake to ensure their full function upon activation. Emerging studies have suggested the potential of pharmacological inhibition of amino acid transporters to inhibit T cell activation and the application of this strategy for treating immunological and inflammatory disorders. In the present review, we explore the possibility of targeting L-type amino acid transporter (LAT) as a novel therapeutic approach for bronchial asthma, including its steroid-resistant endotypes.

Effects of anti‐IL5 biological treatments on blood IgE levels in severe asthmatic patients: A real‐life multicentre study (BIONIGE)

Background

Mepolizumab and benralizumab are clinically effective biological treatments for severe eosinophilic asthmatic patients by hampering eosinophilic inflammation. The effects of these compound on the immunoglobulin (Ig)E T2 component are virtually unknown.

Objectives

To evaluate the change in total IgE levels at 4 ± 2 months after initiation of the mepolizumab (primary outcome) or benralizumab. When available, the changes of blood inflammatory cell counts, lung function and asthma control test (ACT) were also assessed and correlated with changes in total IgE levels.

Methods

Observational, retrospective, multicentre, cohort study. Severe eosinophilic atopic asthmatic patients treated with mepolizumab or benralizumab were included in the analysis.

Results

Three‐month treatment (on average) with mepolizumab (n = 104) or benralizumab (n = 82) resulted in significantly higher reduction of blood eosinophil and basophil levels in patients treated with benralizumab compared to mepolizumab. Mepolizumab did not significantly modified the levels of blood total IgE during the study period, whereas benralizumab significantly reduced (−35%, p < 0.001) total blood IgE levels. In patients treated with benralizumab the reduction of blood total Ig‐E levels correlated with the reduction of blood basophils (but not eosinophils) and weakly with the improvement of asthma control.

Conclusion

Benralizumab but not mepolizumab, treatment led to a significant reduction of circulating IgE level. The study provides different and specific mechanisms of action for anti‐IL5‐pathway treatments.

A rational approach to compare and select biologic therapeutics in asthma

OBJECTIVE

To review key literature on asthma biologic therapeutics-currently available and under investigation-to inform a rational approach to select biologics for the management of people with severe asthma by precision medicine.

DATA SOURCES

We used the PubMed database to review literature on biologic therapeutics in asthma.

STUDY SELECTIONS

We included published randomized control trials and real-world studies on biologic therapeutics, available in English, through September 2021.

RESULTS

Increased understanding of asthma endotypes and the roles of various inflammatory mechanisms has led to therapeutic agents that inhibit specific cytokines or immune pathways. Currently available biologic therapeutics target type 2-high asthma. Grouped by mechanisms of action, there are the following 3 types: (1) anti-immunoglobulin E, (2) anti-interleukin (IL)-5 or IL-5 receptor, and (3) anti-IL-4 receptor α. There are also various potential future biologic therapeutics currently under investigation. Although there remains a paucity of data regarding prospective direct head-to-head comparisons of biologic therapeutics in asthma, there are some retrospective and indirect comparison data available.

CONCLUSION

Precision medicine guides selection of biologic therapeutics along with shared decision-making. Biomarkers, although not comprehensive, allow approximations of likely mechanisms. Use of biomarkers, to include historical levels and trends, in addition to consideration of key clinical characteristics and comorbidities can greatly help guide biologic selection. Efficacy, safety, potential adverse effects, indications for other key comorbidities, and logistics should also be considered.

Immunoglobulin E-Dependent Activation of Immune Cells in Rhinovirus-Induced Asthma Exacerbation

Acute exacerbation is the major cause of asthma morbidity, mortality, and health-care costs. Respiratory viral infections, particularly rhinovirus (RV) infections, are associated with the majority of asthma exacerbations. The risk for bronchoconstriction with RV is associated with allergic sensitization and type 2 airway inflammation. The efficacy of the humanized anti-IgE monoclonal antibody omalizumab in treating asthma and reducing the frequency and severity of RV-induced asthma exacerbation is well-known. Despite these clinical data, mechanistic details of omalizumab's effects on RV-induced asthma exacerbation have not been well-defined for years due to the lack of appropriate animal models. In this Perspective, we discuss potential IgE-dependent roles of mast cells and dendritic cells in asthma exacerbations.

Feasibility of plant-expression system for production of recombinant anti-human IgE: An alternative production platform for therapeutic monoclonal antibodies

Omalizumab, the anti-immunoglobulin IgE antibody is the only approved and available monoclonal antibody as an auxiliary medicament for the severe respiratory allergic reactions. It forms small size immune complexes by binding to free IgE, thereby inhibiting the interaction of IgE with its receptors. Additionally, the anti-IgE can also differently shape the airflow by impeding the stimulation of IgE receptors present on structural cells in the respiratory tract. The present study aimed to use plants as an expression system for anti-human IgE antibody production, using Nicotiana benthamiana as hosts. Recombinant Agrobacterium tumefaciens containing heavy chain (HC) and light chain (LC) domains of anti-human IgE were co-transformed in N. benthamiana. The assembling of the antibody and its expression was detected by SDS-PAGE and Western blot analysis. The functional ability of the anti-IgE antibody was determined via its binding capacity with target IgE by ELISA and the inhibition of basophil activation. The anti-human IgE mAb generated in plants was shown to be effective in binding to its target IgE and inhibit the IgE-crosslink in RS-ATL8 reporter cells. Although, antibody yield and purification process have to be further optimized, this study demonstrates the use of plant expression system as a promising platform for the production of Omalizumab which showed a comparable in vitro function to that of commercial Omalizumab (Xolair) in the inhibition of basophil activation.

Severe pediatric asthma therapy: Omalizumab-A systematic review and meta-analysis of efficacy and safety profile

Background

Omalizumab is the first biological therapy used to treat moderate-to-severe asthma and certainly the one with the highest number of publications.

Methods

A systematic review and meta-analysis were performed to examine two critical outcomes of omalizumab therapy, asthma exacerbation rate, the reduction of the use of inhaled corticosteroids (ICS), and the improvement of the lung function as a secondary outcome using the following keywords in the MEDLINE database: "anti-IgE, severe asthma, children, and randomized controlled trial." We specifically selected papers that included moderate-to-severe asthma patients and collected data on children and adolescents.

Results

Four RCT studies (total number of patients = 1,239) were included in the analysis. The reported data on exacerbations showed an overall improvement in the exacerbation rate with a decreased use of inhaled steroids and some other minimal clinically important difference (MCID).

Conclusions

Our systematic review confirms the known findings that omalizumab therapy decreases asthma exacerbation rate and reduces background therapy inhaled steroid dose. Therefore, add-on therapy with omalizumab shows a good efficacy and safety profile, thus proving to be a useful additional therapeutic option.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier: CRD42023396785.

[Possible therapeutic use of L-type amino acid transporter 1 (LAT1)-specific inhibitor for intractable asthma treatment]

Bronchial asthma (asthma) is characterized by chronic airway inflammation, reversible obstruction, and hyperresponsive conditions. Although most asthma patients have been becoming controllable by virtue of inhaled corticosteroid (ICS), substantial number of patients still do not respond to the steroid-based therapy. Mast cells, eosinophils, and helper T (Th) 2 cells have been considered as key players in asthma pathogenesis. However, emerging studies have revealed that Th subsets other than Th2, as well as various other immune cells, significantly contribute to the development of steroid-resistant intractable asthma. T cells and other inflammatory cells require incorporating a large amount of nutrients such as amino acids and glucose to exhibit their full function following activation. Based on this remarkable character, it has recently been suggested that the pharmacological inhibition of amino acid transporters is promising for treating immunological and inflammatory disorders through the suppression of inflammatory cell activation. In this review, we explore the possible management of intractable asthma by developing a selective inhibitor for L-type amino acid transporter (LAT) 1.

L-type amino acid transporter 1 as a target for inflammatory disease and cancer immunotherapy

Ingestion of amino acids is fundamental for cellular activity. Amino acids are important components for protein synthesis but are also crucial for intracellular metabolic reactions and signal transduction. Following activation, immune cells induce metabolic reprogramming to generate adequate energy and constitutive substances. Hence, the delivery of amino acids by transporters is necessary for the progression of metabolic rewiring. In this review, we discuss how amino acids and their transporters regulate immune cell functions, with emphasis on LAT1, a transporter of large neutral amino acids. Furthermore, we explore the possibility of targeting amino acid transporters to improve immune disorders and cancer immune therapies.

Omalizumab for the treatment of allergic rhinitis: a systematic review and meta-analysis

BACKGROUND

Allergic rhinitis (AR), an IgE mediated inflammatory disease, significantly impacts quality of life of a considerable proportion of the general population. Omalizumab, a humanized monoclonal antibody against IgE, has been evaluated for both seasonal and perennial AR. We aimed to assess the efficacy and safety of omalizumab in randomized controlled trials (RCTs) in inadequately controlled AR.

METHODS

We conducted a systematic literature search of RCTs evaluating the safety and efficacy of omalizumab in AR. We synthesized evidence for clinical improvement of AR symptoms, quality of life, reduction of the use of rescue medication, and adverse events.

RESULTS

The systematic search returned 289 articles, of which 12 RCTs were eligible for data extraction and meta-analysis. Omalizumab reduced the Daily Nasal Symptom Severity Score (DNSSS) by a summary standardized mean difference of -0.41 points with large heterogeneity; omalizumab significantly reduced the DNSSS both in the 3 cedar pollen-induced AR trials by -0.97 points and to a lower extent in the remaining five non-cedar trials by -0.19 points. Omalizumab also improved the Daily Ocular Symptom Severity Score (DOSSS) by a summary standardized mean difference of -0.30 points with large heterogeneity; the Rhino-conjunctivitis Quality of Life Questionnaire by a summary standardized mean difference of -0.45 points with no heterogeneity and the mean daily consumption of rescue antihistamines by a summary standardized mean difference of -0.21 with large heterogeneity. No statistically significant difference in the occurrence of adverse events was observed between omalizumab and placebo.

CONCLUSION

Our findings further support the efficacy and safety of omalizumab in the management of patients with allergic rhinitis inadequately controlled with a conventional treatment.

Strategies for choosing a biologic for your patient with allergy or asthma

OBJECTIVE

To summarize the therapeutic effects and safety of biologics either approved or in clinical development for asthma, chronic obstructive pulmonary disease, urticaria, nasal polyps, atopic dermatitis, and eosinophilic esophagitis. This review attempts to provide some guidance when choosing among agents.

DATA SOURCES

Recently published articles obtained through PubMed database searches including research articles, review articles, and case reports.

STUDY SELECTIONS

PubMed database searches were conducted using the following keywords: biologics, asthma, COPD, urticaria, atopic dermatitis, food allergy, nasal polyps, and eosinophilic esophagitis.

RESULTS

The approval of omalizumab by the Food and Drug Administration in 2003 for patients with asthma paved the way for the development of multiple biologics for a variety of respiratory and allergic diseases. Agents approved by the Food and Drug Administration include mepolizumab, reslizumab, benralizumab, and dupilumab, and several more are in the late stages of clinical development. Owing to the overlap in the pathogenesis of respiratory and allergic diseases, many of these biologics target multiple respiratory and allergic diseases simultaneously.

CONCLUSION

The numerous biologic options have made the selection of the best biologic for each patient a potential conundrum for clinicians. Adequate point of care biomarkers to facilitate personalized medical therapy are generally lacking. Furthermore, although clinically effective and generally safe, none of the biologics discussed in this review have induced long-standing disease remission. Nevertheless, these agents have given us the opportunity to treat the most severe patients and to better understand the biology of respiratory and allergic diseases. As knowledgeable physicians, we should embrace and be educated on these novel therapies and the pathways they target.

Recent Insights into the Management of Inflammation in Asthma

The present prevailing inflammatory paradigm in asthma is of T2-high inflammation orchestrated by key inflammatory cells like Type 2 helper lymphocytes, innate lymphoid cells group 2 and associated cytokines. Eosinophils are key components of this T2 inflammatory pathway and have become key therapeutic targets. Real-world evidence on the predominant T2-high nature of severe asthma is emerging. Various inflammatory biomarkers have been adopted in clinical practice to aid asthma characterization including airway measures such as bronchoscopic biopsy and lavage, induced sputum analysis, and fractional exhaled nitric oxide. Blood measures like eosinophil counts have also gained widespread usage and multicomponent algorithms combining different parameters are now appearing. There is also growing interest in potential future biomarkers including exhaled volatile organic compounds, micro RNAs and urinary biomarkers. Additionally, there is a growing realisation that asthma is a heterogeneous state with numerous phenotypes and associated treatable traits. These may show particular inflammatory patterns and merit-specific management approaches that could improve asthma patient outcomes. Inhaled corticosteroids (ICS) remain the mainstay of asthma management but their use earlier in the course of disease is being advocated. Recent evidence suggests potential roles for ICS in combination with long-acting beta-agonists (LABA) for as needed use in mild asthma whilst maintenance and reliever therapy regimes have gained widespread acceptance. Other anti-inflammatory strategies including ultra-fine particle ICS, leukotriene receptor antagonists and macrolide antibiotics may show efficacy in particular phenotypes too. Monoclonal antibody biologic therapies have recently entered clinical practice with significant impacts on asthma outcomes. Understanding of the efficacy and use of those agents is becoming clearer with a growing body of real-world evidence as is their potential applicability to other treatable comorbid traits. In conclusion, the evolving understanding of T2 driven inflammation alongside a treatable traits disease model is enhancing therapeutic approaches to address inflammation in asthma.

Cellular and molecular mechanisms of allergic asthma

Asthma is a chronic disease of the airways, which affects more than 350 million people worldwide. It is the most common chronic disease in children, affecting at least 30 million children and young adults in Europe. Asthma is a complex, partially heritable disease with a marked heterogeneity. Its development is influenced both by genetic and environmental factors. The most common, as well as the most well characterized subtype of asthma is allergic eosinophilic asthma, which is characterized by a type 2 airway inflammation. The prevalence of asthma has substantially increased in industrialized countries during the last 60 years. The mechanisms underpinning this phenomenon are incompletely understood, however increased exposure to various environmental pollutants probably plays a role. Disease inception is thought to be enabled by a disadvantageous shift in the balance between protective and harmful lifestyle and environmental factors, including exposure to protective commensal microbes versus infection with pathogens, collectively leading to airway epithelial cell damage and disrupted barrier integrity. Epithelial cell-derived cytokines are one of the main drivers of the type 2 immune response against innocuous allergens, ultimately leading to infiltration of lung tissue with type 2 T helper (T_H2) cells, type 2 innate lymphoid cells (ILC2s), M2 macrophages and eosinophils. This review outlines the mechanisms responsible for the orchestration of type 2 inflammation and summarizes the novel findings, including but not limited to dysregulated epithelial barrier integrity, alarmin release and innate lymphoid cell stimulation.

Anti-IgE: A treatment option in allergic rhinitis?

Background: Allergic rhinitis (AR) is the most common IgE-mediated allergic disease. Multiple clinical trials have demonstrated promising results on the AR treatment with biologics, in particular with the use of omalizumab – an anti-IgE antibody. Omalizumab has also been established in the routine management of allergic asthma and chronic idiopathic urticaria. However, currently there is no approved license for the use of biologics in AR in Germany. Materials and methods: A systematic literature review has been completed including randomized controlled trials, meta-analyses, and reviews on the treatment of AR with omalizumab. Results: The systematic review demonstrates strong evidence supporting the use of omalizumab in the treatment of AR with regard to symptom control, safety profile, and management of comorbidities. Conclusion: Omalizumab is a good and safe option in the treatment of AR in terms of symptom control and the management of pre-existing comorbidities. Further clinical trials with other biologics in the management of AR are needed and are expected to follow soon.

IgE in the pathophysiology and therapy of food allergy

Food allergy is becoming a major public health issue, with no regulatory approved therapy to date. Food allergy symptoms range from skin rash and gastrointestinal symptoms to anaphylaxis, a potentially fatal systemic allergic shock reaction. IgE antibodies are thought to contribute importantly to key features of food allergy and anaphylaxis, and measurement of allergen-specific IgE is fundamental in diagnosing food allergy. This review will discuss recent advances in the regulation of IgE production and IgE repertoires in food allergy. We will describe the current understanding of the role of IgE and its high-affinity receptor FcεRI in food allergy and anaphylaxis, by reviewing insights gained from analyses of mouse models. Finally, we will review data derived from clinical studies of the effect of anti-IgE therapeutic monoclonal antibodies (mAbs) in food allergy, and recent insight on the efficiency and mechanisms through which these mAbs block IgE effector functions.

Roles of follicular helper and regulatory T cells in allergic diseases and allergen immunotherapy

Allergic diseases are characterized by overactive type 2 immune responses to allergens and immunoglobulin E (IgE)-mediated hypersensitivity. Emerging evidence suggests that follicular helper T (T_FH ) cells, rather than type 2 T-helper (T_H 2) cells, play a crucial role in controlling IgE production. However, follicular regulatory T (T_FR ) cells, a specialized subset of regulatory T (T_REG ) cells resident in B-cell follicles, restricts T_FH cell-mediated help in extrafollicular antibody production, germinal center (GC) formation, immunoglobulin affinity maturation, and long-lived, high-affinity plasma and memory B-cell differentiation. In mouse models of allergic asthma and food allergy, CXCR5⁺ T_FH cells, not CXCR5^- conventional T_H 2 cells, are needed to support IgE production, otherwise exacerbated by CXCR5⁺ T_FR cell deletion. Upregulation of T_FH cell activities, including a skewing toward type 2 T_FH (T_FH 2) and IL-13 producing T_FH (T_FH 13) phenotypes, and defects in T_FR cells have been identified in patients with allergic diseases. Allergen immunotherapy (AIT) reinstates the balance between T_FH and T_FR cells in patients with allergic diseases, resulting in clinical benefits. Collectively, further understanding of T_FH and T_FR cells and their role in the immunopathogenesis of allergic diseases creates opportunities to develop novel therapeutic approaches.

Advances and novel developments in molecular allergology

The continuous search for new allergens and the design of allergen derivatives improves the understanding of their allergenicity and aids the design of novel diagnostic and immunotherapy approaches. This article discusses the recent developments in allergen and epitope discovery, allergy diagnostics and immunotherapy. Structural information is crucial for the elucidation of cross-reactivity of marker allergens such as the walnut Jug r 6 or that of nonhomologous allergens, as shown for the peanut allergens Ara h 1 and 2. High-throughput sequencing, liposomal nanoallergen display, bead-based assays, and protein chimeras have been used in epitope discovery. The binding of natural ligands by the birch pollen allergen Bet v 1 or the mold allergen Alt a 1 increased the stability of these allergens, which is directly linked to their allergenicity. We also report recent findings on the use of component-resolved approaches, basophil activation test, and novel technologies for improvement of diagnostics. New strategies in allergen-specific immunotherapy have also emerged, such as the use of virus-like particles, biologics or novel adjuvants. The identification of dectin-1 as a key player in allergy to tropomyosins and the formyl peptide receptor 3 in allergy to lipocalins are outstanding examples of research into the mechanism of allergic sensitization.

An Omalizumab Biobetter Antibody With Improved Stability and Efficacy for the Treatment of Allergic Diseases

The critical role of IgE in allergic diseases is well-documented and clinically proven. Omalizumab, a humanized anti-IgE antibody, was the first approved antibody for the treatment of allergic diseases. Nevertheless, omalizumab still has some limitations, such as product instability and dosage restriction in clinical application. In this study, we attempted to develop an omalizumab biobetter antibody with the potential to overcome its limitations. We removed two aspartic acid isomerization hotspots in CDRs of omalizumab to improve antibody candidate’s stability. Meanwhile, several murine amino acids in the framework region of omalizumab were replaced with human source to reduce the potential immunogenicity. Yeast display technology was then applied to screen antibody candidates with high binding affinity to IgE. Moreover, YTE mutation in Fc fragment was introduced into the candidates for extending their serum half-life. A lead candidate, AB1904Am15, was screened out, which showed desired biophysical properties and improved stability, high binding affinity and elevated potency in vitro, prolonged half-life in human FcRn transgenic mouse, and enhanced in vivo efficacy in cynomolgus monkey asthma model. Overall, our study developed a biobetter antibody of omalizumab, AB1904Am15, which has the potential to show improved clinical benefit in the treatment of allergic diseases.

Gu-Ben-Fang-Xiao attenuates allergic airway inflammation by inhibiting BAFF-mediated B cell activation

Allergic airway inflammation is one of the major pathological events involved in the development of asthma. The B cell-activating factor (BAFF)-mediated abnormal activation of B cells plays a key role in developing allergic airway inflammation. Here, we investigated the effects of Gu-Ben-Fang-Xiao decoction (GBFXD), a TCM decoction used in the prevention and treatment of allergic asthma, on allergic airway inflammation and BAFF-mediated B cell activation. A mouse model of OVA-Severe respiratory syncytial virus (RSV) induced asthma in the remission stage was administrated with GBFXD by gavage for four weeks, after which, the pulmonary function was evaluated. Pathological changes of the lung were observed by hematoxylin and eosin (HE) staining, and serum levels of IgE, BAFF, and inflammatory factors were detected by ELISA. The expression of BAFF, APRIL, and their related receptors in the lung and spleen was detected by Western blotting and RT-qPCR. Flow cytometry detected B cell subsets in the spleen, PBC, and monocyte subsets in bronchoalveolar lavage fluid (BALF). The results showed that GBFXD improved the lung function, alleviated the inflammatory changes of the lung tissue in OVA-RSV sensitized mice, and reduced levels of IL-6, TNF-α, IL1-β, INOS, IL13 as well as IL-15, IgE, BAFF in the serum of OVA-RAV mice. Additionally, GBFXD significantly reduced the proportion of CD19+CD27+ B cell subpopulation and IgE + B cell subpopulation in the PBC and spleen cells of mice. Furthermore, the expression of BAFF, APRIL, BAFFR, TACI, and AID decreased in the lung and spleen of GBFXD-treated mice, as well as the proportion of CD11b + BAFF + cell subsets in BALF. In conclusion, GBFXD has an inhibitory effect on the secretion of BAFF by pulmonary macrophages and the expression of BAFF-related receptors, thereby reducing B cell activation and the release of IgE. This proposed mechanism contributes to the improvement of allergic airway inflammation and respiratory function in an asthmatic mouse model.