IgE repertoire and immunological memory: compartmental regulation and antibody function

Interleukin 21 promotes IgG1+ plasma cell differentiation instead of class switching to IgE via Blimp1 expression

IgE is induced by the presence of IL-4 by class switching from IgM through IgG1 to IgE. IL-21 inhibits the IgE class switch by induction of Blimp1 leading to Stat6 and AID downregulation, and plasmablast/plasma cell differentiation.

Engineering therapeutic monoclonal antibodies

The use of human antibodies as biologic therapeutics has revolutionized patient care throughout fields of medicine. As our understanding of the many roles antibodies play within our natural immune responses continues to advance, so will the number of therapeutic indications for which an mAb will be developed. The great breadth of function, long half-life, and modular structure allow for nearly limitless therapeutic possibilities. Human antibodies can be rationally engineered to enhance their desired immune functions and eliminate those that may result in unwanted effects. Antibody therapeutics now often start with fully human variable regions, either acquired from genetically engineered humanized mice or from the actual human B cells. These variable genes can be further engineered by widely used methods for optimization of their specificity through affinity maturation, random mutagenesis, targeted mutagenesis, and use of in silico approaches. Antibody isotype selection and deliberate mutations are also used to improve efficacy and tolerability by purposeful fine-tuning of their immune effector functions. Finally, improvements directed at binding to the neonatal Fc receptor can endow therapeutic antibodies with unbelievable extensions in their circulating half-life. The future of engineered antibody therapeutics is bright, with the global mAb market projected to exhibit compound annual growth, forecasted to reach a revenue of nearly half a trillion dollars in 2030.

Widespread monoclonal IgE antibody convergence to an immunodominant, proanaphylactic Ara h 2 epitope in peanut allergy

BACKGROUND

Despite their central role in peanut allergy, human monoclonal IgE antibodies have eluded characterization.

OBJECTIVE

We sought to define the sequences, affinities, clonality, and functional properties of human monoclonal IgE antibodies in peanut allergy.

METHODS

We applied our single-cell RNA sequencing-based SEQ SIFTER discovery platform to samples from allergic individuals who varied by age, sex, ethnicity, and geographic location in order to understand commonalities in the human IgE response to peanut allergens. Select antibodies were then recombinantly expressed and characterized for their allergen and epitope specificity, affinity, and functional properties.

RESULTS

We found striking convergent evolution of IgE monoclonal antibodies (mAbs) from several clonal families comprising both memory B cells and plasmablasts. These antibodies bound with subnanomolar affinity to the immunodominant peanut allergen Ara h 2, specifically a linear, repetitive motif. Further characterization of these mAbs revealed their ability to single-handedly cause affinity-dependent degranulation of human mast cells and systemic anaphylaxis on peanut allergen challenge in humanized mice. Finally, we demonstrated that these mAbs, reengineered as IgGs, inhibit significant, but variable, amounts of Ara h 2- and peanut-mediated degranulation of mast cells sensitized with allergic plasma.

CONCLUSIONS

Convergent evolution of IgE mAbs in peanut allergy is a common phenomenon that can reveal immunodominant epitopes on major allergenic proteins. Understanding the functional properties of these molecules is key to developing therapeutics, such as competitive IgG inhibitors, that are able to stoichiometrically outcompete endogenous IgE for allergen and thereby prevent allergic cascade in cases of accidental allergen exposure.

Production of monoclonal antibodies for therapeutic purposes: A review

Monoclonal antibodies (mAbs) have been used in the development of immunotherapies that target a variety of diseases, such as cancer, autoimmune diseases, and even viral infections; they play a key role in immunization and are expected after vaccination. However, some conditions do not promote the development of neutralizing antibodies. Production and use of mAbs, generated in biofactories, represent vast potential as aids in immunological responses when the organism cannot produce them on their own, these convey unique specificity by recognizing and targeting specific antigen. Antibodies can be defined as heterotetrametric glycoproteins of symmetric nature, and they participate as effector proteins in humoral responses. Additionally, there are different types of mAbs (murine, chimeric, humanized, human, mAbs as Antibody-drug conjugates and bispecific mAbs) discussed in the present work. When these molecules are produced in vitro as mAbs, several common techniques, such as hybridomas or phage display are used. There are several preferred cell lines that function as biofactories, for the production of mAbs, the selection of which rely on the variation of adaptability, productivity and both phenotypic and genotypic shifts. After the cell expression systems and culture techniques are used, there are diverse specialized downstream processes to achieve desired yield and isolation as well as product quality and characterization. Novel perspectives regarding these protocols represent a potential improvement for mAbs high-scale production.

Associations between vitamin D, immunoglobulin E concentrations, and obesity

The prevalence of allergies and obesity has been increased in parallel. Low vitamin D [25(OH)D] levels have been linked to both higher body mass index (BMI) and allergies. Since the activation of the 25(OH)D receptor inhibits IgE production and 25(OH)D influences the IgE response specifically, we tested the hypothesis that circulating 25(OH)D concentrations are negatively related to circulating allergen-specific IgE concentrations distinctly in a large adult population-based study cohort. Moreover, we studied VDR gene expression in paired biopsies of abdominal subcutaneous (SAT) and visceral adipose tissue (VAT). We investigated whether magnetic resonance imaging-estimated visceral (VFM) and subcutaneous fat mass (SFM) are related to 25(OH)D levels. We found gender differences in circulating 25(OH)D and IgE concentrations. Participants with obesity showed lower 25(OH)D concentrations and higher IgE concentrations were detected in women only. Interestingly, participants with high levels of 25(OH)D are leaner and have improved glucose metabolism. In women, 25(OH)D correlate significant with VFM and SFM. VDR expression is significantly higher expressed in VAT and is positive associated with circulating 25(OH)D concentration. There was no association between serum IgE and 25(OH)D in the entire cohort. Based on these data, we could confirm that low levels of 25(OH)D are linked to higher BMI but could not prove our hypothesis because there is no relationship between 25(OH)D and IgE in adults. Women with higher BMI tend to have higher IgE levels what may have clinical relevance. The association between obesity and circulating 25(OH)D/IgE is not straightforward, and further knowledge is needed.

Peripheral CD23hi/IgE+ Plasmablasts Secrete IgE and Correlate with Allergic Disease Severity

Production and secretion of IgE by B cells, plasmablasts, and plasma cells is a central step in the development and maintenance of allergic diseases. IgE can bind to one of its receptors, the low-affinity IgE receptor CD23, which is expressed on activated B cells. As a result, most B cells bind IgE through CD23 on their surface. This makes the identification of IgE producing cells challenging. In this study, we report an approach to clearly identify live IgE+ plasmablasts in peripheral blood for application by both flow cytometry analysis and in vitro assay. These IgE+ plasmablasts readily secrete IgE, upregulate specific mRNA transcripts (BLIMP-1 IRF4, XBP1, CD138, and TACI), and exhibit highly differentiated morphology all consistent with plasmablast differentiation. Most notably, we compared the presence of IgE+ plasmablasts in peripheral blood of allergic and healthy individuals using a horse model of naturally occurring seasonal allergy, Culicoides hypersensitivity. The model allows the comparison of immune cells both during periods of clinical allergy and when in remission and clinically healthy. Allergic horses had significantly higher percentages of IgE+ plasmablasts and IgE secretion while experiencing clinical allergy compared with healthy horses. Allergy severity and IgE secretion were both positively correlated to the frequency of IgE+ plasmablasts in peripheral blood. These results provide strong evidence for the identification and quantification of peripheral IgE-secreting plasmablasts and provide a missing cellular link in the mechanism of IgE secretion and upregulation during allergy.

Longitudinal antibody responses to peanut following probiotic and peanut oral immunotherapy (PPOIT) in children with peanut allergy

INTRODUCTION

Probiotic and Peanut Oral Immunotherapy (PPOIT) is effective at inducing sustained unresponsiveness (SU) at end-of-treatment and this effect persists up to four years post-treatment, referred to as persistent SU. We sought to evaluate (i) how PPOIT altered peanut-specific humoral immune indices, and (ii) how such longitudinal indices relate to persistent SU.

METHODS

Longitudinal serum/plasma levels of whole peanut- and peanut component- (Ara-h1, -h2, -h3, -h8, -h9) specific-IgE (sIgE) and specific-IgG4 (sIgG4) antibodies were measured by ImmunoCAP and salivary peanut-specific-IgA (sIgA) by ELISA in children (n=62) enrolled in the PPOIT-001 randomised trial from baseline (T0) to 4-years post-treatment (T5). Multivariate regression analyses of log-transformed values were used for point-in-time between group comparisons. Generalised estimating equations (GEE) were used for longitudinal comparisons between groups.

RESULTS

PPOIT was associated with changes in sIgE and sIgG4 over time. sIgE levels were significantly reduced post-treatment [T5, PPOIT v.s. Placebo ratio of geometric mean (GM): Ara-h1 0.07, p=0.008; Ara-h2 0.08, p=0.007; Ara-h3 0.15, p=0.021]. sIgG4 levels were significantly increased by end-of-treatment (T1, PPOIT v.s. Placebo ratio of GM: Ara-h1 3.77, p=0.011; Ara-h2 17.97, p<0.001; Ara-h3 10.42, p<0.001) but levels in PPOIT group decreased once treatment was stopped and returned to levels comparable with Placebo group by T5. Similarly, salivary peanut sIgA increased during treatment, as early as 4 months of treatment (PPOIT v.s. Placebo, ratio of GM: 2.04, p=0.014), then reduced post-treatment.

CONCLUSION

PPOIT was associated with broad reduction in peanut specific humoral responses which may mediate the clinical effects of SU that persists to 4-years post-treatment.

Scientific Opinion on development needs for the allergenicity and protein safety assessment of food and feed products derived from biotechnology

This Scientific Opinion addresses the formulation of specific development needs, including research requirements for allergenicity assessment and protein safety, in general, which is urgently needed in a world that demands more sustainable food systems. Current allergenicity risk assessment strategies are based on the principles and guidelines of the Codex Alimentarius for the safety assessment of foods derived from 'modern' biotechnology initially published in 2003. The core approach for the safety assessment is based on a 'weight-of-evidence' approach because no single piece of information or experimental method provides sufficient evidence to predict allergenicity. Although the Codex Alimentarius and EFSA guidance documents successfully addressed allergenicity assessments of single/stacked event GM applications, experience gained and new developments in the field call for a modernisation of some key elements of the risk assessment. These should include the consideration of clinical relevance, route of exposure and potential threshold values of food allergens, the update of in silico tools used with more targeted databases and better integration and standardisation of test materials and in vitro/in vivo protocols. Furthermore, more complex future products will likely challenge the overall practical implementation of current guidelines, which were mainly targeted to assess a few newly expressed proteins. Therefore, it is timely to review and clarify the main purpose of the allergenicity risk assessment and the vital role it plays in protecting consumers' health. A roadmap to (re)define the allergenicity safety objectives and risk assessment needs will be required to inform a series of key questions for risk assessors and risk managers such as 'what is the purpose of the allergenicity risk assessment?' or 'what level of confidence is necessary for the predictions?'.

B Cell Functions in the Development of Type I Allergy and Induction of Immune Tolerance

B cells are key players in the mechanisms underlying allergic sensitization, allergic reactions, and tolerance to allergens. Allergen-specific immune responses are initiated when peptide:MHCII complexes on dendritic cells are recognized by antigen-specific receptors on T cells followed by interactions between costimulatory molecules on the surfaces of B and T cells. In the presence of IL-4, such T-B cell interactions result in clonal expansion and isotype class-switching to IgE in B cells, which will further differentiate into either memory B cells or PCs. Allergic reactions are then triggered upon cross-linking of IgE-FcɛRI complexes on basophils and mast cells, leading to cell degranulation and the release of pro-inflammatory mediators.Mechanisms underlying effective allergen-specific immunotherapy (AIT) involve the induction of Tregs and the secretion of blocking IgG4 antibodies, which together mediate the onset and maintenance of immune tolerance towards non-hazardous environmental antigens. However, the importance of regulatory B cells (Breg) for tolerance induction during AIT has gained more attention lately. Studies in grass pollen- and house dust mite-allergic patients undergoing SCIT reported increased frequencies of IL-10+ Breg cells and a positive correlation between their number and the improvement of clinical symptoms. Thus, Breg are emerging as biomarkers for monitoring tolerance to allergens under natural exposure conditions and during AIT. Further research on the role of other anti-inflammatory cytokines secreted by Breg will help to understand their role in disease development and tolerance induction.

Dupilumab suppresses type 2 inflammatory biomarkers across multiple atopic, allergic diseases

BACKGROUND

Type 2 inflammation is common in numerous atopic/allergic diseases and can be identified by elevated biomarker levels. Dupilumab, a fully human monoclonal antibody, blocks the shared receptor component for interleukin-4 and interleukin-13, key and central drivers of type 2 inflammation.

OBJECTIVE

Assessment of dupilumab effect on type 2 inflammatory biomarkers in atopic dermatitis (AD), asthma, chronic rhinosinusitis with nasal polyps (CRSwNP) and eosinophilic esophagitis (EoE).

METHODS

Data were extracted from three randomized placebo-controlled trials of dupilumab in AD (NCT02277743, N = 671; NCT02277769, N = 708; NCT02260986, N = 740); and one each in asthma (NCT02414854, N = 1902); CRSwNP (NCT02898454, N = 448); and EoE (NCT02379052, N = 47). Biomarkers assessed were serum thymus and activation-regulated chemokine (TARC), plasma eotaxin-3, serum total immunoglobulin E (IgE), serum periostin and blood eosinophil count.

RESULTS

Dupilumab versus placebo significantly suppressed most type 2 inflammatory biomarker levels across all studies/indications where data were assessed. Reductions in serum TARC, plasma eotaxin-3 and serum periostin occurred rapidly, whereas reductions in serum total IgE were more gradual. Across diseases, at the end of treatment, median percentage change from baseline in TARC levels ranged from -24.8% to -88.6% (placebo +2.6% to -53.6%); -38.2% to -51.5% (placebo +8.3% to -0.16%) in eotaxin-3; -24.8% to -76.7% (placebo +8.3% to -4.4%) in total IgE; and -13.6% to -41.1% (placebo +10.1% to -6.94%) in periostin levels. Blood eosinophil responses to dupilumab varied by disease, with minimal changes in AD in the SOLO studies (median percentage change from baseline to end of treatment: 0% [95% CI: -15.8, 0]); transient increases followed by decreases to below-baseline levels in asthma (-14.6% [-20.0, -7.7]) and CRSwNP (-29.4% [-40.0, -16.3]); and significant decreases in EoE (-50.0% [-50.0, -33.3]).

CONCLUSION AND CLINICAL RELEVANCE

Dupilumab reduced levels of type 2 biomarkers across clinical studies in patients with AD, asthma, CRSwNP and EoE.

Mapping B-Cell Epitopes for Nonspecific Lipid Transfer Proteins of Legumes Consumed in India and Identification of Critical Residues Responsible for IgE Binding

Nonspecific lipid transfer proteins (nsLTPs) have been categorized as panallergens and display widespread occurrence across plant-kingdom. Present study, investigated B-cell epitopes for LTPs from chickpea, mung-bean, cowpea, pigeon-pea, and soybean via in silico methods. In-silico predicted regions were evaluated for epitope-conservancy and property-based peptide similarity search by different allergen databases. Additionally, the in-silico predicted regions were compared with the experimentally validated epitopes of peach-LTP. Sequence-homology studies showed that chickpea and mung-bean LTPs shared significant homology, i.e., >70% and >60%, respectively, with other LTP allergens from lentil, garden-pea, peanut, etc. Phylogenetic-analysis also showed chickpea and mung-bean LTPs to be closely related to allergenic LTPs from lentil and peanut, respectively. Epitope-conservation analysis showed that two of the predicted B-cell epitopic regions in chickpea and mung-bean LTPs were also conserved in other allergenic LTPs from peach, peanut, garden-pea, lentil, and green-bean, and might serve as conserved B-cell epitopes of the LTP protein family. Property-distance index values for chickpea and mung-bean LTPs also showed that most of the epitopes shared similarity with the reported allergens like-lentil, peanut, apple, plum, tomato, etc. Present findings, may be explored for identification of probable allergenicity of novel LTPs, on the basis of the reported conserved B-cell epitopes, responsible for potential cross-reactivity.

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.

Origins and clonal convergence of gastrointestinal IgE+ B cells in human peanut allergy

B cells in human food allergy have been studied predominantly in the blood. Little is known about IgE⁺ B cells or plasma cells in tissues exposed to dietary antigens. We characterized IgE⁺ clones in blood, stomach, duodenum, and esophagus of 19 peanut-allergic patients, using high-throughput DNA sequencing. IgE⁺ cells in allergic patients are enriched in stomach and duodenum, and have a plasma cell phenotype. Clonally related IgE⁺ and non-IgE-expressing cell frequencies in tissues suggest local isotype switching, including transitions between IgA and IgE isotypes. Highly similar antibody sequences specific for peanut allergen Ara h 2 are shared between patients, indicating that common immunoglobulin genetic rearrangements may contribute to pathogenesis. These data define the gastrointestinal tract as a reservoir of IgE⁺ B lineage cells in food allergy.

IL-21 is a broad negative regulator of IgE class switch recombination in mouse and human B cells

IgE antibodies may elicit potent allergic reactions, and their production is tightly controlled. The tendency to generate IgE has been thought to reflect the balance between type 1 and type 2 cytokines, with the latter promoting IgE. Here, we reevaluated this paradigm by a direct cellular analysis, demonstrating that IgE production was not limited to type 2 immune responses yet was generally constrained in vivo. IL-21 was a critical negative regulator of IgE responses, whereas IFN-γ, IL-6, and IL-10 were dispensable. Follicular helper T cells were the primary source of IL-21 that inhibited IgE responses by directly engaging the IL-21 receptor on B cells and triggering STAT3-dependent signaling. We reconciled previous discordant results between mouse and human B cells and revealed that the inhibition of IgE class switch recombination by IL-21 was attenuated by CD40 signaling, whereas IgG1 class switch recombination was potentiated by IL-21 in the context of limited IL-4. These findings establish key features of the extrinsic regulation of IgE production by cytokines.

A proposed treatment for pathogenic enveloped viruses having high rates of mutation or replication

Several enveloped viruses, particularly some RNA viruses, have high rates of mutation or replication, which can make them virulent pathogens in humans and other mammals. A proposed treatment could use synthesized proteins to mask pathogenic viral surface proteins to quickly induce an immune attack on specific enveloped viruses by using existing immune cells. One treatment could inject dual‐protein ligand masks into patients' bloodstreams to mask pathogenic surface proteins used to infect mammalian cells. The mammalian immune system already uses an analogous, more complex structure called a pentraxin to neutralize some pathogens by connecting their surface proteins to immune cells. And several types of antiviral peptides have already experimentally demonstrated effectiveness in blocking various viral pathogen infections. These treatments offer advantages, especially for currently untreatable viral pathogens. Furthermore, using dual‐protein ligands and the antigenic memory of some sub‐populations of NK cells would also allow the creation of defacto vaccines based on a host's NK cells, instead of vaccines utilizing CD4 and CD8 α:β T cells, which are limited by the requirement of MHC presentation of the target antigens to α:β T cells. Targeted NK cell vaccines could attack host cells latently or actively infected by intracellular pathogens, even host cells having pathogen downregulated MHC antigen presentation. Eight postulates concerning the effects of pathogen mutation, or change in phenotype from genetic recombination or rearrangement, and replication rates on pathogen vs host dominance are also listed, which should be applicable to viral and non‐viral pathogens.

Mucosal IgE immune responses in respiratory diseases

IgE is the less abundant immunoglobulin isotype in serum and displays higher affinity for its cognate Fc receptor (FcεRI) than the rest of antibody isotypes. Moreover, the class switch recombination and the generation of memory responses remarkably differ between IgE and other isotypes. Importantly, class switch recombination to IgE can occur in the mucosae, preferentially through the sequential switching from IgG. Therefore, resident effector cells get rapidly sensitized, and free IgE can be found in mucosal secretions. All these aspects explain the involvement of IgE in respiratory diseases. In allergic rhinitis and allergic asthma, the IgE-sensitization to environmental allergens triggers an eosinophilic inflammation of the airway mucosa of atopic patients. In recent years, growing evidence indicates that some non-atopic patients with nasal reactivity to allergens display nasal eosinophilic inflammation, which could be triggered by the local production of allergen-specific IgE. This phenotype has been termed local allergic rhinitis. Mucosal IgE is also implicated in the pathophysiology of chronic rhinosinusitis with nasal polyps, even though the mechanisms for IgE synthesis might differ in this case. The role of IgE as mediator of airway diseases identify this marker as a therapeutic target. Some biologicals antagonize IgE-mediated inflammation of the airway mucosa, but they have not shown a beneficial long-term effect after discontinuation. In contrast, allergen immunotherapy does not only control the symptoms of airway allergy, but it also induces a long-lasting effect after discontinuation, thus modifying the natural course of the disease.

Asthma and Chronic Rhinosinusitis: Diagnosis and Medical Management

Asthma is a prevalent inflammatory condition of the lower airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchial hyperresponsiveness (BHR). Symptomatically, these patients may demonstrate wheezing, breathlessness, chest tightness, and coughing. This disease is a substantial burden to a growing population worldwide that currently exceeds 300 million individuals. This is a condition that is frequently encountered, but often overlooked in the field of otolaryngology. In asthma, comorbid conditions are routinely present and contribute to respiratory symptoms, decreased quality of life, and poorer asthma control. It is associated with otolaryngic diseases of the upper airways including allergic rhinitis (AR) and chronic rhinosinusitis (CRS). These conditions have been linked epidemiologically and pathophysiologically. Presently, they are considered in the context of the unified airway theory, which describes the upper and lower airways as a single functional unit. Thus, it is important for otolaryngologists to understand asthma and its complex relationships to comorbid diseases, in order to provide comprehensive care to these patients. In this article, we review key elements necessary for understanding the evaluation and management of asthma and its interrelatedness to CRS.