IgG1 memory B cells keep the memory of IgE responses

Single-cell RNA sequencing reveals the landscape of biomarker in allergic rhinitis patient undergoing intracervical lymphatic immunotherapy and related pan-cancer analysis

INTRODUCTION

Allergic rhinitis (AR) is one of the leading allergic diseases worldwide. Allergen immunotherapy (AIT) induces persistent specific allergen tolerance to achieve remission of the symptoms in AR patients. We creatively conducted the intra-cervical lymphatic immunotherapy (ICLIT) for AR patients. However, the underlying molecular mechanism of immune cell response of AIT in AR remains elusive.

METHOD

To investigate the transcriptome profile in AR patients who underwent ICLIT, we comprehensively investigated the transcriptional changes in B cells from peripheral blood mononuclear cells of AR patient by single-cell RNA sequencing. Immunoglobulins and relative key gene, which influences the B cell differentiation, was demonstrated. The biomarkers' association with different types of tumors was investigated.

RESULTS

Naive B cells, germinal center B cells, activated memory B cells, and memory B cells constituted the B cells subsets. The expression of IGHE, IGHGs, IGHA, IGHD, and IGHM from memory B cells was validated. Pseudotime analysis further indicated the dynamic change from the expression of the immunoglobulins in the memory B cells, suggesting that ITGB1 may contribute to the differentiation procedure of memory B cells. The cell-cell communication among these immune cells demonstrated the significantly enhanced CD23, BTLA signaling after ICLIT in AR patient. ITGB1 was upregulated in 13 tumors and downregulated in six others. High ITGB1 expression was linked to poor prognosis in eight types of tumors. ITGB1 expression showed correlations with tumor mutation burden, tissue purity, and microsatellite instability in different types of tumors.

DISCUSSION

ITGB1 was demonstrated as a potential biomarker for AR patients after ICLIT and is significant in identifying immune infiltration in tumor tissue and predicting tumor prognosis.

Poly(I:C) and R848 ligands show better adjuvanticity to induce B and T cell responses against the antigen(s)

Poly(I:C) and R848, synthetic ligands that activate Toll-like receptor 3 (TLR3) and TLR7/8 respectively, have been well-established for their ability to stimulate the immune system and induce antigen-specific immune responses. These ligands are capable of inducing the production of cytokines and chemokines, and hence support the activation and differentiation of B and T cells. We saw the long-lasting and perdurable immune responses by these adjuvants essentially required for an efficacious subunit vaccine. In this study, we investigated the potential of poly(I:C) and R848 to elicit B and T cell responses to the OVA antigen. We assessed the stimulatory effects of these ligands on the immune system, their impact on B and T cell activation, and their ability to enhanced generation of B and T cells. Collectively, our findings contribute to the understanding how poly(I:C) and R848 can be utilized as an adjuvant system to enhance immune responses to protein-based subunit vaccines. In the end, this work provides insights for the development of novel vaccination strategies and improving the vaccine efficacy. Present work shall help formulate newer strategies for subunit vaccines to address the infectious diseases.

The trajectory of human B-cell function, immune deficiency, and allergy revealed by inborn errors of immunity

The essential role of B cells is to produce protective immunoglobulins (Ig) that recognize, neutralize, and clear invading pathogens. This results from the integration of signals provided by pathogens or vaccines and the stimulatory microenvironment within sites of immune activation, such as secondary lymphoid tissues, that drive mature B cells to differentiate into memory B cells and antibody (Ab)-secreting plasma cells. In this context, B cells undergo several molecular events including Ig class switching and somatic hypermutation that results in the production of high-affinity Ag-specific Abs of different classes, enabling effective pathogen neutralization and long-lived humoral immunity. However, perturbations to these key signaling pathways underpin immune dyscrasias including immune deficiency and autoimmunity or allergy. Inborn errors of immunity that disrupt critical immune pathways have identified non-redundant requirements for eliciting and maintaining humoral immune memory but concomitantly prevent immune dysregulation. Here, we will discuss our studies on human B cells, and how our investigation of cytokine signaling in B cells have identified fundamental requirements for memory B-cell formation, Ab production as well as regulating Ig class switching in the context of protective versus allergic immune responses.

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.

Type 2-polarized memory B cells hold allergen-specific IgE memory

Allergen-specific immunoglobulin E (IgE) antibodies mediate pathology in diseases such as allergic rhinitis and food allergy. Memory B cells (MBCs) contribute to circulating IgE by regenerating IgE-producing plasma cells upon allergen encounter. Here, we report a population of type 2-polarized MBCs defined as CD23hi, IL-4Rαhi, and CD32low at both the transcriptional and surface protein levels. These MBC2s are enriched in IgG1- and IgG4-expressing cells while constitutively expressing germline transcripts for IgE. Allergen-specific B cells from patients with allergic rhinitis and food allergy were enriched in MBC2s. Furthermore, MBC2s generated allergen-specific IgE during sublingual immunotherapy, thereby identifying these cells as a major reservoir for IgE. The identification of MBC2s provides insights into the maintenance of IgE memory, which is detrimental in allergic diseases but could be beneficial in protection against venoms and helminths.

CD23+IgG1+ memory B cells are poised to switch to pathogenic IgE production in food allergy

Food allergy is caused by allergen-specific immunoglobulin E (IgE) antibodies, but little is known about the B cell memory of persistent IgE responses. Here, we describe, in human pediatric peanut allergy, a population of CD23+IgG1+ memory B cells arising in type 2 immune responses that contain high-affinity peanut-specific clones and generate IgE-producing cells upon activation. The frequency of CD23+IgG1+ memory B cells correlated with circulating concentrations of IgE in children with peanut allergy. A corresponding population of "type 2-marked" IgG1+ memory B cells was identified in single-cell RNA sequencing experiments. These cells differentially expressed interleukin-4 (IL-4)- and IL-13-regulated genes, such as FCER2/CD23+, IL4R, and germline IGHE, and carried highly mutated B cell receptors (BCRs). In children with high concentrations of serum peanut-specific IgE, high-affinity B cells that bind the main peanut allergen Ara h 2 mapped to the population of "type 2-marked" IgG1+ memory B cells and included clones with convergent BCRs across different individuals. Our findings indicate that CD23+IgG1+ memory B cells transcribing germline IGHE are a unique memory population containing precursors of high-affinity pathogenic IgE-producing cells that are likely to be involved in the long-term persistence of peanut allergy.

A therapeutic strategy to target distinct sources of IgE and durably reverse allergy

Immunoglobulin E (IgE) is a key driver of type 1 hypersensitivity reactions and allergic disorders, which are globally increasing in number and severity. Although eliminating pathogenic IgE may be a powerful way to treat allergy, no therapeutic strategy reported to date can fully ablate IgE production. Interleukin-4 receptor α (IL-4Rα) signaling is required for IgE class switching, and IL-4Rα blockade gradually reduces, but does not eliminate, IgE. The persistence of IgE after IL-4Rα blockade may be due to long-lived IgE+ plasma cells that maintain serological memory to allergens and thus may be susceptible to plasma cell-targeted therapeutics. We demonstrate that transient administration of a B cell maturation antigen x CD3 (BCMAxCD3) bispecific antibody markedly depletes IgE, as well as other immunoglobulins, by ablating long-lived plasma cells, although IgE and other immunoglobulins rapidly rebound after treatment. Concomitant IL-4Rα blockade specifically and durably prevents the reemergence of IgE by blocking IgE class switching while allowing the restoration of other immunoglobulins. Moreover, this combination treatment prevented anaphylaxis in mice. Together with additional cynomolgus monkey and human data, our studies demonstrate that allergic memory is primarily maintained by both non-IgE+ memory B cells that require class switching and long-lived IgE+ plasma cells. Our combination approach to durably eliminate pathogenic IgE has potential to benefit allergy in humans while preserving antibody-mediated immunity.

Human IgM-expressing memory B cells

A hallmark of T cell dependent (TD) humoral immune responses is the generation of long-lived memory B cells. The generation of these cells occurs primarily in the germinal center (GC) reaction, where antigen-activated B cells undergo affinity maturation as a major consequence of the combined processes of proliferation, somatic hypermutation of their immunoglobulin V (IgV) region genes, and selection for improved affinity of their B-cell antigen receptors. As many B cells also undergo class-switching to IgG or IgA in these TD responses, there was traditionally a focus on class-switched memory B cells in both murine and human studies on memory B cells. However, it has become clear that there is also a large subset of IgM-expressing memory B cells, which have important phenotypic and functional similarities but also differences to class-switched memory B cells. There is an ongoing discussion about the origin of distinct subsets of human IgM+ B cells with somatically mutated IgV genes. We argue here that the vast majority of human IgM-expressing B cells with somatically mutated IgV genes in adults is indeed derived from GC reactions, even though a generation of some mostly lowly mutated IgM+ B cells from other differentiation pathways, mainly in early life, may exist.

The B Cell Response and Formation of Allergenic and Anti-Allergenic Antibodies in Food Allergy

Food allergies are a growing public health concern worldwide, especially in children and young adults. Allergen-specific IgE plays a central role in the pathogenesis of food allergies, but their titers poorly correlate with allergy development. Host immune systems yield allergen-specific immunoglobulin (Ig)A, IgE and IgG subclasses with low or high affinities and differential Fc N-glycosylation patterns that can affect the allergic reaction to food in multiple ways. High-affinity IgE is required to induce strong mast cell activation eventually leading to allergic anaphylaxis, while low-affinity IgE can even inhibit the development of clinically relevant allergic symptoms. IgA and IgG antibodies can inhibit IgE-mediated mast cell activation through various mechanisms, thereby protecting IgE-positive individuals from allergy development. The production of IgE and IgG with differential allergenic potential seems to be affected by the signaling strength of individual B cell receptors, and by cytokines from T cells. This review provides an overview of the diversity of the B cell response and the diverse roles of antibodies in food allergy.

The origins and longevity of IgE responses as indicated by serological and cellular studies in mice and humans

The existence of long-lived IgE antibody-secreting cells (ASC) is contentious, with the maintenance of sensitization by the continuous differentiation of short-lived IgE+ ASC a possibility. Here, we review the epidemiological profile of IgE production, and give an overview of recent discoveries made on the mechanisms regulating IgE production from mouse models. Together, these data suggest that for most individuals, in most IgE-associated diseases, IgE+ ASC are largely short-lived cells. A subpopulation of IgE+ ASC in humans is likely to survive for tens of months, although due to autonomous IgE B cell receptor (BCR) signaling and antigen-driven IgE+ ASC apoptosis, in general IgE+ ASC probably do not persist for the decades that other ASC are inferred to do. We also report on recently identified memory B cell transcriptional subtypes that are the likely source of IgE in ongoing responses, highlighting the probable importance of IL-4Rα in their regulation. We suggest the field should look at dupilumab and other drugs that prohibit IgE+ ASC production as being effective treatments for IgE-mediated aspects of disease in most individuals.

The mechanism underlying the inverse proportion between serum IgE concentration and Stat3 transcriptional activity depends on Stat3 mutation type

Abnormalities in the IL-6/STAT3 signaling pathway can sometimes result in extremely high levels of IgE concentration in serum, however, the regulatory role of STAT3 in IgE production is elusive. We used several genetically modified mice with distinctive germline Stat3 transcriptional activity to assess the influence of Stat3 on the biochemical characteristics of IgE and found that the IgE concentration in serum is inversely proportional to Stat3 transcriptional activity. Intriguingly, the serum IgE concentration is directly proportional to IgE-producing B cells in Stat3-GOF mice but inversely proportional in mice carrying Stat3 mutations with reduced transcriptional activity. For reduced Stat3 transcriptional activity induced high levels of IgE in the mice, IL-4/Stat6 signaling is indispensable for IgE production, but it was observed that an increased IgE concentration was accompanied by reduced IL-4/Stat6 signaling and lessened IgE-producing B cells, which implies that an increase in IgE concentration may result from an extended half-life of IgE but not an increasing number of IgE-producing cells.

B cells: The many facets of B cells in allergic diseases

B cells play a key role in our immune system through their ability to produce antibodies, suppress a proinflammatory state, and contribute to central immune tolerance. We aim to provide an in-depth knowledge of the molecular biology of B cells, including their origin, developmental process, types and subsets, and functions. In allergic diseases, B cells are well known to induce and maintain immune tolerance through the production of suppressor cytokines such as IL-10. Similarly, B cells protect against viral infections such as severe acute respiratory syndrome coronavirus 2 that caused the recent coronavirus disease 2019 pandemic. Considering the unique and multifaceted functions of B cells, we hereby provide a comprehensive overview of the current knowledge of B-cell biology and its clinical applications in allergic diseases, organ transplantation, and cancer.

We are memory: B-cell responses in allergy and tolerance

The significance of B-cell memory in sustaining IgE-mediated allergies but also ensuring the development of long-term allergen tolerance has remained enigmatic. However, well-thought murine and human studies have begun to shed more light on this highly disputed subject. The present mini review highlights important aspects, like the involvement of IgG1 memory B cells, the meaning of low- or high-affinity IgE antibody production, the impact of allergen immunotherapy, or the relevance of local memory established by ectopic lymphoid structures. Based on recent findings, future investigations should lead to deeper knowledge and the development of improved therapies treating allergic individuals.

Clonal evolution and stereotyped sequences of human IgE lineages in aeroallergen-specific immunotherapy

BACKGROUND

Allergic disease reflects specific inflammatory processes initiated by interaction between allergen and allergen-specific IgE. Specific immunotherapy (SIT) is an effective long-term treatment option, but the mechanisms by which SIT provides desensitization are not well understood.

OBJECTIVE

Our aim was to characterize IgE sequences expressed by allergen-specific B cells over a 3-year longitudinal study of patients with aeroallergies who were undergoing SIT.

METHODS

Allergen-specific IgE-expressing clones were identified by using combinatorial single-chain variable fragment libraries and tracked in PBMCs and nasal biopsy samples over a 3-year period with antibody gene repertoire sequencing. The characteristics of private IgE-expressing clones were compared with those of stereotyped or "public" IgE responses to the grass pollen allergen Phleum pratense (Phl p) 2.

RESULT

Members of the same allergen-specific IgE lineages were observed in nasal biopsy samples and blood, and lineages detected at baseline persisted in blood and nasal biopsy samples after 3 years of SIT, including B cells that express IgE. Evidence of progressive class switch recombination to IgG subclasses was observed after 3 years of SIT. A common stereotyped Phl p 2-specific antibody heavy chain sequence was detected in multiple donors. The amino acid residues enriched in IgE-stereotyped sequences from seropositive donors were analyzed with machine learning and k-mer motif discovery. Stereotyped IgE sequences had lower overall rates of somatic hypermutation and antigen selection than did single-chain variable fragment-derived allergen-specific sequences or IgE sequences of unknown specificity.

CONCLUSION

Longitudinal tracking of rare circulating and tissue-resident allergen-specific IgE+ clones demonstrates persistence of allergen-specific IgE+ clones, progressive class switch recombination to IgG subtypes, and distinct maturation of a stereotyped Phl p 2 clonotype.

Requirements of IL-4 during the Generation of B Cell Memory

IL-4 has long been established as a key regulator of Th cells and for promoting effective B cell survival and isotype class switching. Yet, despite having been extensively studied, the specific role of IL-4 in generating humoral memory in vivo is unclear. In this review, we explore the recent studies that unravel the cellular sources and spatiotemporal production of IL-4, the relationship between IL-4 and IL-21 during germinal center responses and the formation of Ab-secreting cells, and the current understanding of whether IL-4 promotes or suppresses memory B cell generation in vitro and in vivo.

Proteasome inhibition reduces plasma cell and antibody secretion, but not angiotensin II-induced hypertension

Introduction

Depletion of mature B cells affords protection against experimental hypertension. However, whether B cell-mediated hypertension is dependent on differentiation into antibody-secreting cells (ASCs) remains unclear. Using the proteasome inhibitor, bortezomib, the present study tested the effect of ASC reduction on angiotensin II-induced hypertension.

Methods

Male C57BL6/J mice were infused with angiotensin II (0.7 mg/kg/day; s.c.) for 28 days via osmotic minipump to induce hypertension. Normotensive control mice received saline infusion. Bortezomib (750 μg/kg) or vehicle (0.1% DMSO) was administered (i.v.) 3 days prior to minipump implantation, and twice weekly thereafter. Systolic blood pressure was measured weekly using tail-cuff plethysmography. Spleen and bone marrow B1 (CD19⁺B220^-), B2 (B220⁺CD19⁺) and ASCs (CD138^hiSca-1⁺Blimp-1⁺) were enumerated by flow cytometry. Serum immunoglobulins were quantified using a bead-based immunoassay.

Results

Bortezomib treatment reduced splenic ASCs by ∼68% and ∼64% compared to vehicle treatment in normotensive (2.00 ± 0.30 vs. 0.64 ± 0.15 × 10⁵ cells; n = 10-11) and hypertensive mice (0.52 ± 0.11 vs. 0.14 ± 0.02 × 10⁵ cells; n = 9-11), respectively. Bone marrow ASCs were also reduced by bortezomib in both normotensive (4.75 ± 1.53 vs. 1.71 ± 0.41 × 10³ cells; n = 9-11) and hypertensive mice (4.12 ± 0.82 vs. 0.89 ± 0.18 × 10³ cells; n = 9-11). Consistent with ASC reductions, bortezomib reduced serum IgM and IgG2a in all mice. Despite these reductions in ASCs and antibody levels, bortezomib did not affect angiotensin II-induced hypertension over 28 days (vehicle: 182 ± 4 mmHg vs. bortezomib: 177 ± 7 mmHg; n = 9-11).

Conclusion

Reductions in ASCs and circulating IgG2a and IgM did not ameliorate experimental hypertension, suggesting other immunoglobulin isotypes or B cell effector functions may promote angiotensin II-induced hypertension.

Upregulated Expression of the IL-9 Receptor on TRAF3-Deficient B Lymphocytes Confers Ig Isotype Switching Responsiveness to IL-9 in the Presence of Antigen Receptor Engagement and IL-4

The pleiotropic cytokine IL-9 signals to target cells by binding to a heterodimeric receptor consisting of the unique subunit IL-9R and the common subunit γ-chain shared by multiple cytokines of the γ-chain family. In the current study, we found that the expression of IL-9R was strikingly upregulated in mouse naive follicular B cells genetically deficient in TNFR-associated factor 3 (TRAF3), a critical regulator of B cell survival and function. The highly upregulated IL-9R on Traf3-/- follicular B cells conferred responsiveness to IL-9, including IgM production and STAT3 phosphorylation. Interestingly, IL-9 significantly enhanced class switch recombination to IgG1 induced by BCR crosslinking plus IL-4 in Traf3-/- B cells, which was not observed in littermate control B cells. We further demonstrated that blocking the JAK-STAT3 signaling pathway abrogated the enhancing effect of IL-9 on class switch recombination to IgG1 induced by BCR crosslinking plus IL-4 in Traf3-/- B cells. Our study thus revealed, to our knowledge, a novel pathway that TRAF3 suppresses B cell activation and Ig isotype switching by inhibiting IL-9R-JAK-STAT3 signaling. Taken together, our findings provide (to our knowledge) new insights into the TRAF3-IL-9R axis in B cell function and have significant implications for the understanding and treatment of a variety of human diseases involving aberrant B cell activation such as autoimmune disorders.

Targeting type 2 immunity and the future of food allergy treatment

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

Evidence that High-Affinity IgE Can Develop in the Germinal Center in the Absence of an IgG1-Switched Intermediate

High-affinity allergen-specific IgE is essential for the severe allergic anaphylaxis response. High-affinity Abs are formed by successive rounds of selection of Ag-specific B cells in the germinal center (GC); however, several studies have shown that IgE+ GC B cells are impaired in their ability to undergo selection in the GC. A pathway, known as the "indirect switching pathway" for IgE, has been described whereby Ag-specific B cells initially switch to the IgG1 isotype and undergo affinity selection in the GC, with a secondary switch to the IgE isotype after affinity selection. In previous work, using a food allergy model in mice, we investigated how high-affinity IgE develops in the GC, but we did not test the indirect switching model. In this study, we analyzed the importance of the indirect switching pathway by constructing IgG1-cre Bcl6-fl/fl mice. In these mice, once B cells switch to IgG1, they delete Bcl6 and thus cannot enter or persist in the GC. When we tested IgG1-cre Bcl6-fl/fl mice with our food allergy model, we found that, as expected, IgG1 Abs had decreased affinity, but unexpectedly, the affinity of IgE for allergen was unchanged. IgG1-cre Bcl6-fl/fl mice underwent anaphylaxis in response to allergen, consistent with the formation of high-affinity IgE. Thus, in a food allergy response, high-affinity IgE can be efficiently formed in the absence of indirect switching to IgG1, either by direct selection of IgE+ GC B cells or indirect selection of IgM+ GC B cells that later switch to IgE.

IgG memory B cells expressing IL4R and FCER2 are associated with atopic diseases

BACKGROUND

Atopic diseases are characterized by IgE antibody responses that are dependent on cognate CD4 T cell help and T cell-produced IL-4 and IL-13. Current models of IgE cell differentiation point to the role of IgG memory B cells as precursors of pathogenic IgE plasma cells. The goal of this work was to identify intrinsic features of memory B cells that are associated with IgE production in atopic diseases.

METHODS

Peripheral blood B lymphocytes were collected from individuals with physician diagnosed asthma or atopic dermatitis (AD) and from non-atopic individuals. These samples were analyzed by spectral flow cytometry, single cell RNA sequencing (scRNAseq), and in vitro activation assays.

RESULTS

We identified a novel population of IgG memory B cells characterized by the expression of IL-4/IL-13 regulated genes FCER2/CD23, IL4R, IL13RA1, and IGHE, denoting a history of differentiation during type 2 immune responses. CD23+ IL4R+ IgG+ memory B cells had increased occurrence in individuals with atopic disease. Importantly, the frequency of CD23+ IL4R+ IgG+ memory B cells correlated with levels of circulating IgE. Consistently, in vitro stimulated B cells from atopic individuals generated more IgE+ cells than B cells from non-atopic subjects.

CONCLUSIONS

These findings suggest that CD23+ IL4R+ IgG+ memory B cells transcribing IGHE are potential precursors of IgE plasma cells and are linked to pathogenic IgE production.

The memory of pathogenic IgE is contained within CD23 + IgG1 + memory B cells poised to switch to IgE in food allergy

Food allergy is caused by allergen-specific IgE antibodies but little is known about the B cell memory of persistent IgE responses. Here we describe in human pediatric peanut allergy CD23 + IgG1 + memory B cells arising in type 2 responses that contain peanut specific clones and generate IgE cells on activation. These 'type2-marked' IgG1 + memory B cells differentially express IL-4/IL-13 regulated genes FCER2 / CD23, IL4R , and germline IGHE and carry highly mutated B cell receptors (BCRs). Further, high affinity memory B cells specific for the main peanut allergen Ara h 2 mapped to the population of 'type2-marked' IgG1 + memory B cells and included convergent BCRs across different individuals. Our findings indicate that CD23 + IgG1 + memory B cells transcribing germline IGHE are a unique memory population containing precursors of pathogenic IgE.

One-Sentence Summary

We describe a unique population of IgG + memory B cells poised to switch to IgE that contains high affinity allergen-specific clones in peanut allergy.

Treatment with Helicobacter pylori-derived VacA attenuates allergic airway disease

Background

Asthma is an incurable heterogeneous disease with variations in clinical and underlying immunological phenotype. New approaches could help to support existing therapy concepts. Neonatal infection of mice with Helicobacter pylori or administration of H. pylori-derived extracts or molecules after birth have been shown to prevent the development of allergic airway disease later in life. This study evaluated the potential therapeutic efficacy of H. pylori vacuolating cytotoxin A (VacA) in allergic airway inflammation and investigated the underlying immunological mechanisms for its actions.

Methods

Murine models of allergic airway diseases, and murine and human in vitro models were used.

Results

In both an acute model and a therapeutic house dust mite model of allergic airway disease, treatment with H. pylori-derived VacA reduced several asthma hallmarks, including airway hyperresponsiveness, inflammation and goblet cell metaplasia. Flow cytometry and ELISA analyses revealed induction of tolerogenic dendritic cells (DC) and FoxP3 positive regulatory T cells (Tregs), and a shift in the composition of allergen-specific immunoglobulins. Depletion of Tregs during treatment with VacA reversed treatment-mediated suppression of allergic airway disease. Human monocyte derived DCs (moDC) that were exposed to VacA induced Tregs in co-cultured naïve autologous T cells, replicating key observations made in vivo.

Conclusion

H. pylori-derived VacA suppressed allergic airway inflammation via induction of Tregs in both allergic airway disease models. These data suggest that the immunomodulatory activity of VacA could potentially be exploited for the prevention and treatment of allergic airway disease.

Allergenic food protein consumption is associated with systemic IgG antibody responses in non-allergic individuals

Although food-directed immunoglobulin E (IgE) has been studied in the context of allergies, the prevalence and magnitude of IgG responses against dietary antigens are incompletely characterized in the general population. Here, we measured IgG binding against food and environmental antigens obtained from allergen databases and the immune epitope database (IEDB), represented in a phage displayed library of 58,233 peptides. By profiling blood samples of a large cohort representing the average adult Israeli population (n = 1,003), we showed that many food antigens elicited systemic IgG in up to 50% of individuals. Dietary intake of specific food protein correlated with antibody binding, suggesting that diet can shape the IgG epitope repertoire. Our work documents abundant systemic IgG responses against food antigens and provides a reference map of the exact immunogenic epitopes on a population scale, laying the foundation to unravel the role of food- and environmental antigen-directed antibody binding in disease contexts.

Increased B Cell Understanding Puts Improved Vaccine Platforms Just Over the Horizon

In the face of an endlessly expanding repertoire of Ags, vaccines are constantly being tested, each more effective than the last. As viruses and other pathogens evolve to become more infectious, the need for efficient and effective vaccines grows daily, which is especially obvious in an era that is still attempting to remove itself from the clutches of the severe acute respiratory syndrome coronavirus 2, the cause of coronavirus pandemic. To continue evolving alongside these pathogens, it is proving increasingly essential to consider one of the main effector cells of the immune system. As one of the chief orchestrators of the humoral immune response, the B cell and other lymphocytes are essential to not only achieving immunity, but also maintaining it, which is the vital objective of every vaccine.

Targeting CD22 on memory B cells to induce tolerance to peanut allergens

BACKGROUND

Circulating IgE and subsequent severe allergic reactions to peanut are sustained and propagated by recall of peanut allergen-specific memory B cells.

OBJECTIVES

This study aimed to determine whether targeting mouse and human CD22 on peanut-specific memory B cells induces tolerance to peanut allergens.

METHODS

Siglec-engaging tolerance-inducing antigenic liposomes (STALs) codisplaying peanut allergens (Ara h 1, Ara h 2, or Ara h 3) and high-affinity CD22 ligand (CD22L-STALs) were employed in various mouse models (BALB/cJ, C57BL/6, human CD22 transgenic, and NSG) of peanut allergy. To investigate memory B cells, a conferred memory model was used in which splenocytes from peanut-sensitized mice were transferred into naive animals. Reconstituted mice received either CD22L-STALs or an immunogenic liposome control, followed by a peanut allergen boost and later a challenge with individual peanut allergens. To assess the effects of CD22L-STALs on human B cells, PBMCs were injected into NSG mice, followed by administration of human CD22L-STALs (hCD22L-STALs) and later a whole peanut extract boost. Blood was collected to quantify WPE- and Ara h 1-, 2-, and 3-specific immunoglobulins.

RESULTS

Mouse CD22L-STALs (mCD22L-STALs) significantly suppressed systemic memory to Ara h 1, Ara h 2, and Ara h 3 in BALB/cJ and C57BL/6 mice, as demonstrated by reduced allergen-specific IgE, IgG₁, and anaphylaxis on challenge. Importantly, 2 doses of mCD22L-STALs led to prolonged tolerance for at least 3 months. hCD22L-STALs displayed similar suppression in mice expressing human CD22 on B cells. Finally, human B cells were tolerized in vivo in NSG mice by hCD22L-STALs.

CONCLUSIONS

Antigen-specific exploitation of CD22 on memory B cells can induce systemic immune tolerance.

B cell fate mapping reveals their contribution to the memory immune response against helminths

An estimated quarter of the human world population is infected with gastrointestinal helminths causing major socioeconomic problems in endemic countries. A better understanding of humoral immune responses against helminths is urgently needed to develop effective vaccination strategies. Here, we used a fate mapping (FM) approach to mark germinal center (GC) B cells and their developmental fates by induced expression of a fluorescent protein during infection of mice with the helminth Nippostrongylus brasiliensis. We could show that FM⁺ cells persist weeks after clearance of the primary infection mainly as CD80⁺CD73⁺PD-L2⁺ memory B cells. A secondary infection elicited expansion of helminth-specific memory B cells and plasma cells (PCs). Adoptive transfers and analysis of somatic mutations in immunoglobulin genes further revealed that FM⁺ B cells rapidly convert to PCs rather than participating again in a GC reaction. These results provide new insights in the population dynamics of the humoral immune response against helminths.

DEPs Induce Local Ige Class Switching Independent of Their Ability to Stimulate iBALT de Novo Formation

BACKGROUND

Diesel exhaust particles (DEPs) are leading to a general increase in atopic diseases worldwide. However, it is still unknown whether DEPs induce systemic B-cell IgE class switching in secondary lymphoid organs or locally in the lungs in inducible bronchus-associated lymphoid tissue (iBALT). The aim of this work was to identify the exact site of DEP-mediated B-cell IgE class switching and pro-allergic antibody production.

METHODS

We immunized BALB/c mice with different OVA doses (0.3 and 30 µg) intranasally in the presence and absence of two types of DEPs, SRM1650B and SRM2786. We used low (30 µg) and high (150 µg) DEP doses.

RESULTS

Only a high DEP dose induced IgE production, regardless of the particle type. Local IgE class switching was stimulated upon treatment with both types of particles with both low and high OVA doses. Despite the similar ability of the two standard DEPs to stimulate IgE production, their ability to induce iBALT formation and growth was markedly different upon co-administration with low OVA doses.

CONCLUSIONS

DEP-induced local IgE class switching takes place in preexisting iBALTs independent of de novo iBALT formation, at least in the case of SRM1650B co-administered with low OVA doses.

Single-dose AAV vector gene immunotherapy to treat food allergy

Immunotherapies for patients with food allergy have shown some success in limiting allergic responses. However, these approaches require lengthy protocols with repeated allergen dosing and patients can relapse following discontinuation of treatment. The purpose of this study was to test if a single dose of an adeno-associated virus (AAV) vector can safely prevent and treat egg allergy in a mouse model. AAV vectors expressing ovalbumin (OVA) under an ubiquitous or liver-specific promoter were injected prior to or after epicutaneous sensitization with OVA. Mice treated with either AAV8-OVA vector were completely protected from allergy sensitization. These animals had a significant reduction in anaphylaxis mediated by a reduction in OVA-specific IgE titers. In mice with established OVA allergy, allergic responses were mitigated only in mice treated with an AAV8-OVA vector expressing OVA from an ubiquitous promoter. In conclusion, an AAV vector with a liver-specific promoter was more effective for allergy prevention, but higher OVA levels were necessary for reducing symptoms in preexisting allergy. Overall, our AAV gene immunotherapy resulted in an expansion of OVA-specific FoxP3⁺ CD4⁺ T cells, an increase in the regulatory cytokine IL-10, and a reduction in the IgE promoting cytokine IL-13.

Suitability of potyviral recombinant virus-like particles bearing a complete food allergen for immunotherapy vaccines

Virus-like particles (VLPs) have been gaining attention as potential platforms for delivery of cargos in nanomedicine. Although animal viruses are largely selected due to their immunostimulatory capacities, VLPs from plant viruses constitute a promising alternative to be considered. VLPs derived from Turnip mosaic virus (TuMV) have proven to present a tridimensional structure suited to display molecules of interest on their surface, making them interesting tools to be studied in theragnostic strategies. Here, we study their potential in the treatment of food allergy by genetically coupling TuMV-derived VLPs to Pru p 3, one of the most dominant allergens in Mediterranean climates. VLPs-Pru p 3 were generated by cloning a synthetic gene encoding the TuMV coat protein and Pru p 3, separated by a linker, into a transient high-expression vector, followed by agroinfiltration in Nicotiana benthamiana plants. The generated fusion protein self-assembled in planta to form the VLPs, which were purified by exclusion chromatography. Their elongated morphology was confirmed by electron microscopy and their size (~400 nm), and monodispersity was confirmed by dynamic light scattering. Initial in vitro characterization confirmed that they were able to induce proliferation of human immune cells. This proliferative capability was enhanced when coupled with the natural lipid ligand of Pru p 3. The resultant formulation, called VLP-Complex, was also able to be transported by intestinal epithelial cells, without affecting the monolayer integrity. In light of all these results, VLP-Complex was furtherly tested in a mouse model of food allergy. Sublingual administration of VLP-Complex could effectively reduce some serological markers associated with allergic responses in mice, such as anti-Pru p 3 sIgE and sIgG2a. Noteworthy, no associated macroscopic, nephritic, or hepatic toxicity was detected, as assessed by weight, blood urea nitrogen (BUN) and galectin-3 analyses, respectively. Our results highlight the standardized production of allergen-coated TuMV-VLPs in N. benthamiana plants. The resulting formula exerts notable immunomodulatory properties without the need for potentially hazardous adjuvants. Accordingly, no detectable toxicity associated to their administration was detected. As a result, we propose them as good candidates to be furtherly studied in the treatment of immune-based pathologies.

The role of B cells in COVID-19 infection and vaccination

B cells secrete antibodies and mediate the humoral immune response, making them extremely important in protective immunity against SARS-CoV-2, which caused the coronavirus disease 2019 (COVID-19) pandemic. In this review, we summarize the positive function and pathological response of B cells in SARS-CoV-2 infection and re-infection. Then, we structure the immunity responses that B cells mediated in peripheral tissues. Furthermore, we discuss the role of B cells during vaccination including the effectiveness of antibodies and memory B cells, viral evolution mechanisms, and future vaccine development. This review might help medical workers and researchers to have a better understanding of the interaction between B cells and SARS-CoV-2 and broaden their vision for future investigations.

Development of allergen-specific IgE in a food-allergy model requires precisely timed B cell stimulation and is inhibited by Fgl2

Immunoglobulin E (IgE) responses are a central feature of allergic disease. Using a well-established food-allergy model in mice, we show that two sensitizations with cognate B cell antigen (Ag) and adjuvant 7 days apart promotes optimal development of IgE+ germinal center (GC) B cells and high-affinity IgE production. Intervals of 3 or 14 days between Ag sensitizations lead to loss of IgE+ GC B cells and an undetectable IgE response. The immunosuppressive factors Fgl2 and CD39 are down-regulated in T follicular helper (TFH) cells under optimal IgE-sensitization conditions. Deletion of Fgl2 in TFH and T follicular regulatory (TFR) cells, but not from TFR cells alone, increase Ag-specific IgE levels and IgE-mediated anaphylactic responses. Overall, we find that Ag-specific IgE responses require precisely timed stimulation of IgE+ GC B cells by Ag. Furthermore, we show that Fgl2 is expressed by TFH cells and represses IgE. This work has implications for the development and treatment of food allergies.

Using a mouse food-allergy model, Chen et al. find that allergen-specific IgE responses require precisely timed stimulation of IgE+ germinal center B cells. The authors further show that Fgl2 expressed by T follicular helper cells represses IgE. This work has implications for the development and treatment of food allergy.

Immunoglobulin E response in health and disease beyond allergic disorders

Immunoglobulin E is the latest discovered of immunoglobulin family and has been long associated with anaphylaxis and worm expulsion. Immunoglobulin E, along with mast cells, basophils, and eosinophils, is also a hallmark of type 2 immunity which is dysregulated in numerous diseases such as asthma, rhinitis, atopic dermatitis, and eosinophilic esophagitis in addition to anaphylaxis as aforementioned. However, recent advances have shed light on IgE regulation and memory explaining the low level of free IgE, the scarcity of IgE plasma cells that are mainly short live and the absence of IgE memory B cells in homeostatic conditions. Furthermore, IgE was implicated in inflammatory conditions beyond allergic disorders where IgE-mediated facilitated antigen presentation can enhance cellular and humoral response against autoantigens in systemic lupus or chronic urticaria leading to more severe disease and even against neoantigen facilitating tumor cell lysis. At last, IgE was unexpectedly associated with allograft rejection or atheromatous cardiovascular diseases where precise mechanisms remain to be deciphered. The purpose of this review is to summarize these recent advances in IgE regulation, biology, and physiopathology beyond allergic diseases opening whole new fields of IgE biology to explore.

Distinct disease-specific Tfh cell populations in two different fibrotic diseases: IgG4-related disease and Kimura's disease

BACKGROUND

How T follicular (Tfh) cells contribute to many different B-cell class-switching events during T cell-dependent immune responses has been unclear. Diseases with polarized isotype switching offer a unique opportunity for the exploration of Tfh subsets. Secondary and tertiary lymphoid organs (SLOs and TLOs) in patients with elevated tissue expression levels of IgE (Kimura's disease, KD) and those of IgG4 (IgG4-related disease, IgG4-RD) can provide important insights regarding cytokine expression by Tfh cells.

OBJECTIVE

To identify disease-specific Tfh cell subsets in SLOs and TLOs expressing IL-10 or IL-13 and thus identify different cellular drivers of class switching in two distinct types of fibrotic disorders: allergic fibrosis (driven by type 2 immune cells) and inflammatory fibrosis (driven by cytotoxic T lymphocytes).

METHODS

Single-cell RNA-sequencing, in situ sequencing, and multi-color immunofluorescence analysis was used to investigate B cells, Tfh cells and infiltrating type 2 cells in lesion tissues from patients with KD or IgG4-RD.

RESULTS

Infiltrating Tfh cells in TLOs from IgG4-RD were divided into six main clusters. We encountered abundant infiltrating IL-10-expressing LAG3⁺ Tfh cells in patients with IgG4-RD. Furthermore, we found that infiltrating AID⁺CD19⁺B cells expressing IL-4, IL-10, and IL-21 receptors correlated with IgG4 expression. In contrast, we found that infiltrating IL-13-expressing Tfh cells were abundant in affected tissues from patients with KD. Moreover, we observed few infiltrating IL-13-expressing Tfh cells in tissues from patients with IgG4-RD, despite high serum levels of IgE (but low IgE in the disease lesions). Cytotoxic T cells were abundant in IgG4-RD, and in contrast Type 2 immune cells were abundant in KD.

CONCLUSIONS

This single-cell dataset revealed a novel subset of IL10⁺LAG3⁺Tfh cells infiltrating the affected organs of IgG4-RD patients. In contrast, IL13⁺Tfh cells and type 2 immune cells infiltrated those of KD patients.

Phylogenetic analysis of migration, differentiation, and class switching in B cells

B cells undergo rapid mutation and selection for antibody binding affinity when producing antibodies capable of neutralizing pathogens. This evolutionary process can be intermixed with migration between tissues, differentiation between cellular subsets, and switching between functional isotypes. B cell receptor (BCR) sequence data has the potential to elucidate important information about these processes. However, there is currently no robust, generalizable framework for making such inferences from BCR sequence data. To address this, we develop three parsimony-based summary statistics to characterize migration, differentiation, and isotype switching along B cell phylogenetic trees. We use simulations to demonstrate the effectiveness of this approach. We then use this framework to infer patterns of cellular differentiation and isotype switching from high throughput BCR sequence datasets obtained from patients in a study of HIV infection and a study of food allergy. These methods are implemented in the R package dowser, available at https://dowser.readthedocs.io.

B cells produce high affinity antibodies through an evolutionary process of mutation and selection during adaptive immune responses. Migration between tissues, differentiation to cellular subtypes, and switching between different antibody isotypes can be important factors in shaping the role B cells play in response to infection, autoimmune disease, and allergies. B cell receptor (BCR) sequence data has the potential to elucidate important information about these processes. However, there is currently no robust, generalizable framework for making such inferences from BCR sequence data. Here, we develop three parsimony-based summary statistics to characterize migration, differentiation, and isotype switching along B cell phylogenetic trees. We confirm the effectiveness of our approach using simulations and further apply our method to data from patients with HIV and allergy. Our methods are released in the R package dowser: https://dowser.readthedocs.io.

Two allergens from Scylla paramamosain share common epitopes showed different allergenic potential in Balb/c mice

Filamin C (FLN c) and triosephosphate isomerase (TIM) are novel allergens of crab (Scylla paramamosain) which are sharing common epitopes. This work aimed to assess their contributions to the induction and elicitation of allergenic responses. Balb/c mice were sensitized by intraperitoneal injections and challenged by intragastric gavage with purified proteins. Upon oral challenge, FLN c triggered more severe anaphylactic symptoms, higher levels of specific antibodies and histamine in serum than TIM, while TIM was a more active promotor of early specific antibody production and stimulated stronger Th2-biased responses. Combined with the results of in vitro assays, the data demonstrated that though with common epitopes, the two allergens showed a different allergenicity, TIM favored Th2 polarization in sensitization stage, while FLN c had a better ability to stimulate B cells and is highly immunogenic in oral challenge stage. The findings can help with the better understanding of allergenicity of crab allergens.

The Road Toward Transformative Treatments for Food Allergy

A series of landmark studies have provided conclusive evidence that the early administration of food allergens dramatically prevents the emergence of food allergy. One of the greatest remaining challenges is whether patients with established food allergy can return to health. This challenge is particularly pressing in the case of allergies against peanut, tree nuts, fish, and shellfish which are lifelong in most patients and may elicit severe reactions. The standard of care for food allergy is allergen avoidance and the timely administration of epinephrine upon accidental exposure. Epinephrine, and other therapeutic options like antihistamines provide acute symptom relief but do not target the underlying pathology of the disease. In principle, any transformative treatment for established food allergy would require the restoration of a homeostatic immunological state. This may be attained through either an active, non-harmful immune response (immunological tolerance) or a lack of a harmful immune response (e.g., anergy), such that subsequent exposures to the allergen do not elicit a clinical reaction. Importantly, such a state must persist beyond the course of the treatment and exert its protective effects permanently. In this review, we will discuss the immunological mechanisms that maintain lifelong food allergies and are, consequently, those which must be dismantled or reprogrammed to instate a clinically non-reactive state. Arguably, the restoration of such a state in the context of an established food allergy would require a reprogramming of the immune response against a given food allergen. We will discuss existing and experimental therapeutic strategies to eliminate IgE reactivity and, lastly, will propose outstanding questions to pave the road to the development of novel, transformative therapeutics in food allergy.

Germinal Centers

Germinal centers (GCs) are microanatomical sites of B cell clonal expansion and antibody affinity maturation. Therein, B cells undergo the Darwinian process of somatic diversification and affinity-driven selection of immunoglobulins that produces the high-affinity antibodies essential for effective humoral immunity. Here, we review recent developments in the field of GC biology, primarily as it pertains to GCs induced by infection or immunization. First, we summarize the phenotype and function of the different cell types that compose the GC, focusing on GC B cells. Then, we review the cellular and molecular bases of affinity-dependent selection within the GC and the export of memory and plasma cells. Finally, we present an overview of the emerging field of GC clonal dynamics, focusing on how GC and post-GC selection shapes the diversity of antibodies secreted into serum. Expected final online publication date for the Annual Review of Immunology, Volume 40 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Features of B Cell Responses Relevant to Allergic Disease

This Brief Review delves into B cell responses in the context of allergy. The primary contribution of B cells to allergy is the production of IgE, the Ab isotype that triggers immediate hypersensitivity reactions through the release of mediators from mast cells and basophils. B cells may also have protective roles in allergy, such as through the production of IgG or as regulatory B cells. In this review, I focus on the basic principles of B cell differentiation and discuss features relevant to allergic immune responses. In particular, I discuss: (1) class-switch recombination; (2) plasma cell differentiation; (3) germinal centers and affinity maturation; and (4) memory B cells and recall responses, with an emphasis on IgE, IgG1, and IgG4. I also consider how B cells may contribute to allergic responses independent of Ab production-for example, by serving as APCs.

The germinal centre B cell response to SARS-CoV-2

The germinal centre (GC) response is critical for the generation of affinity-matured plasma cells and memory B cells capable of mediating long-term protective immunity. Understanding whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or vaccination elicits a GC response has profound implications for the capacity of responding B cells to contribute to protection against infection. However, direct assessment of the GC response in humans remains a major challenge. Here we summarize emerging evidence for the importance of the GC response in the establishment of durable and broad immunity against SARS-CoV-2 and discuss new approaches to modulate the GC response to better protect against newly emerging SARS-CoV-2 variants. We also discuss new findings showing that the GC B cell response persists in the draining lymph nodes for at least 6 months in some individuals following vaccination with SARS-CoV-2 mRNA-based vaccines.

B-cell receptor physical properties affect relative IgG1 and IgE responses in mouse egg allergy

Mutated and unmutated IgE and IgG play different and partly opposing roles in allergy development, but the mechanisms controlling their relative production are incompletely understood. Here, we analyzed the IgE-response in murine food allergy. Deep sequencing of the complementary-determining region (CDR) repertoires indicated that an ongoing unmutated extrafollicular IgE response coexists with a germinal center response, even after long-lasting allergen challenges. Despite overall IgG1-dominance, a significant proportion of clonotypes contained several-fold more IgE than IgG1. Clonotypes with differential bias to either IgE or IgG1 showed distinct hypermutation and clonal expansion. Hypermutation rates were associated with different physiochemical binding properties of individual B-cell receptors (BCR). Increasing BCR signaling strength inhibited class switching from IgG1 to IgE in vitro, preferentially constraining IgE formation. These data indicate that antigen-binding properties of individual BCRs determine differential IgE hypermutation and IgE versus IgG1 production on the level of single B-cell clones.

B cells and food allergy

PURPOSE OF REVIEW

B cells are known in food allergy pathogenesis for their production of IgE but their roles in the development of tolerance to foods are not well understood. Further understanding of B-cell biology in the context of food allergy is essential for the creation of effective prevention strategies and therapies.

RECENT FINDINGS

The majority of allergen-specific IgE in humans appears to arise from antigen-experienced B cells that have already undergone class switch recombination to other antibody isotypes, such as IgG1, and can also be produced by cells class switching to IgE locally in the gastrointestinal tract. Allergen-specific IgG4 can have protective effects in individuals and is associated with tolerance. Regulatory B cells, which can produce allergen-specific IgG4, are reduced in food-allergic individuals and may also be an important component of tolerance. Therapeutic approaches that block the generation and action of IgE and that enhance tolerizing immune responses are being evaluated for the treatment of food allergy.

SUMMARY

B cells play several roles in the development of food allergy versus tolerance. Their functions may translate into the care of food allergy as biomarkers or therapeutic targets and can be employed in other atopic diseases to better understand their pathogenesis and create new avenues for treatment.

Targeting IgE polyadenylation signal with antisense oligonucleotides decreases IgE secretion and plasma cell viability

BACKGROUND

Allergy regroups numerous complex and various diseases classified as IgE-dependent or non-IgE-dependent hypersensitivities. IgEs are expressed as membrane and secreted forms by B cells and plasma cells, respectively. In IgE-mediated hypersensitivity, IgE secretion and binding to the high-affinity IgE receptor FcεRI on effector cells are responsible for the onset of allergic symptoms; in contrast, surface IgE expression as a B-cell receptor is barely detectable.

OBJECTIVE

Our aim was to test an innovative antisense approach to reducing IgE secretion.

METHODS

We designed an antisense oligonucleotide (ASO) targeting the polyadenylation signal of human secreted IgE to redirect IgE transcript polyadenylation from the secreted form to the membrane form. ASO treatments were performed on B cells from transgenic mice expressing humanized IgE (InEps mice), as well as on human primary B cells and myeloma cells. In vivo ASO delivery was tested by using an InEps mouse model.

RESULTS

We demonstrated that treatment with a morpholino ASO targeting the secreted IgE polyadenylation signal drastically decreased IgE secretion and inversely increased membrane IgE mRNA expression. In addition, ASO treatment induced apoptosis of IgE-expressing U266 myeloma cells, and RNA sequencing revealed attenuation of their plasma cell phenotype. Remarkably, systemic administration of an ASO coupled with Pip6a as an arginine-rich cell-penetrating peptide decreased IgE secretion in vivo.

CONCLUSION

Altogether, this ASO strategy could be an effective way to decrease IgE secretion and allergic symptoms in patients with IgE-dependent allergies, and it could also promote allergen tolerance through apoptosis of IgE⁺ antibody-secreting cells.

High-resolution epitope mapping by AllerScan reveals relationships between IgE and IgG repertoires during peanut oral immunotherapy

Peanut allergy can result in life-threatening reactions and is a major public health concern. Oral immunotherapy (OIT) induces desensitization to food allergens through administration of increasing amounts of allergen. To dissect peanut-specific immunoglobulin E (IgE) and IgG responses in subjects undergoing OIT, we have developed AllerScan, a method that leverages phage-display and next-generation sequencing to identify the epitope targets of peanut-specific antibodies. We observe a striking diversification and boosting of the peanut-specific IgG repertoire after OIT and a reduction in pre-existing IgE levels against individual epitopes. High-resolution epitope mapping reveals shared recognition of public epitopes in Ara h 1, 2, 3, and 7. In individual subjects, OIT-induced IgG specificities overlap extensively with IgE and exhibit strikingly similar antibody footprints, suggesting related clonal lineages or convergent evolution of peanut-specific IgE and IgG B cells. Individual differences in epitope recognition identified via AllerScan could inform safer and more effective personalized immunotherapy.

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

BACKGROUND

Allergen-specific IL-4⁺ and IL-13⁺ CD4⁺ cells (type 2 cells) are essential for helping B cells to class-switch to IgE and establishing an allergic milieu in the gastrointestinal tract. The role of T cells in established food allergy is less clear.

OBJECTIVE

We examined the food allergen-specific T-cell response in participants of 2 food allergen immunotherapy trials to assess the relationship of the T-cell response to clinical phenotypes, including response to immunotherapy.

METHODS

Blood was obtained from 84 participants with peanut allergy and 142 participants with egg allergy who underwent double-blind placebo-controlled food challenges. Peanut- and egg-responsive T cells were identified by CD154 upregulation after stimulation with the respective extract. Intracellular cytokines and chemokine receptors were also detected. The response to peanut epicutaneous immunotherapy (Peanut Epicutaneous Phase II Immunotherapy Clinical Trial [CoFAR6]; 49 participants receiving epicutaneous immunotherapy) and egg oral immunotherapy or a baked egg diet (Baked Egg or Egg Oral Immunotherapy for Children With Egg Allergy [CoFAR7]; 92 participants) was monitored over time.

RESULTS

Peanut-specific type 2 and CCR6⁺ T cells were negatively correlated with each other and differently associated with immune parameters, including specific IgE level and basophil activation test result. At baseline, type 2 cells, but not CCR6⁺ cells, were predictive of clinical parameters, including a successfully consumed dose of peanut and baked egg tolerance. Exposure to peanut or egg immunotherapy was associated with a decrease in type 2 cell frequency. At baseline, high egg-specific type 2 cell frequency was the immune feature most predictive of oral immunotherapy failure.

CONCLUSION

Food-specific type 2 T cells at baseline are informative of threshold of reactivity and response to immunotherapy.

Follicular dendritic cells restrict interleukin-4 availability in germinal centers and foster memory B cell generation

B cells within germinal centers (GCs) enter cycles of antibody affinity maturation or exit the GC as memory cells or plasma cells. Here, we examined the contribution of interleukin (IL)-4 on B cell fate decisions in the GC. Single-cell RNA-sequencing identified a subset of light zone GC B cells expressing high IL-4 receptor-a (IL4Ra) and CD23 and lacking a Myc-associated signature. These cells could differentiate into pre-memory cells. B cell-specific deletion of IL4Ra or STAT6 favored the pre-memory cell trajectory, and provision of exogenous IL-4 in a wild-type context reduced pre-memory cell frequencies. IL-4 acted during antigen-specific interactions but also influenced bystander cells. Deletion of IL4Ra from follicular dendritic cells (FDCs) increased the availability of IL-4 in the GC, impaired the selection of affinity-matured B cells, and reduced memory cell generation. We propose that GC FDCs establish a niche that limits bystander IL-4 activity, focusing IL-4 action on B cells undergoing selection and enhancing memory cell differentiation.

Allergen-specific IgG show distinct patterns in persistent and transient food allergy

BACKGROUND

Immediate food-allergic reactions are IgE-mediated, but many individuals with detectable allergen-specific IgE do not react to the food. Allergen-specific IgG may interfere with allergen-IgE interaction and/or through intracellular inhibitory signalling to suppress mast cell and basophil response to food allergens. We aimed to understand the role of allergen-specific IgG in food allergy and natural tolerance.

METHODS

IgG and IgG isotypes specific to peanut, cow's milk and egg were measured using ImmunoCAP and ELISA respectively in samples of children with suspected food allergies. Expression of IgE and IgG and their receptors and expression of activation markers following allergen stimulation were measured on basophils and mast cells by flow cytometry, with and without blockade of FcγRIIα or FcγRIIβ receptors.

RESULTS

The levels of peanut-specific IgG, IgG1, IgG2, IgG3 and IgG4 in ELISA were higher in peanut-allergic than in non-peanut-allergic children. No difference in allergen-specific IgG isotypes was observed between allergic and non-allergic children to milk or egg, except for milk-specific IgG4 that was higher in non-cow's milk-allergic than in cow's milk-allergic children. Basophils and LAD2 cells expressed IgG receptors, but IgG and IgA were not detected on the surface of either cell type and blocking FcγRIIα or FcγRIIβ did not modify basophil or mast cell activation in response to allergen in allergic or tolerant children.

CONCLUSION

Allergen-specific IgG patterns were distinct in persistent (peanut) versus transient (milk and egg) food allergies. We found no evidence that FcγRIIα or FcγRIIβ receptors affect allergen-induced activation of mast cells and basophils in food allergy or natural tolerance.

Differential induction of allergen-specific IgA responses following timothy grass subcutaneous and sublingual immunotherapy

INTRODUCTION

There is no detailed comparison of allergen-specific immunoglobulin responses following sublingual immunotherapy (SLIT) and subcutaneous immunotherapy (SCIT).

OBJECTIVE

We sought to compare nasal and systemic timothy grass pollen (TGP)-specific antibody responses during 2 years of SCIT and SLIT and 1 year after treatment discontinuation in a double-blind, double-dummy, placebo-controlled trial.

METHODS

Nasal fluid and serum were obtained yearly (per-protocol population, n = 84). TGP-specific IgA₁, IgA₂, IgG₄, IgG, and IgE were measured in nasal fluids by ELISA. TGP-specific IgA₁, IgA₂, and Phleum pratense (Phl p)1, 2, 4, 5b, 6, 7, 11, and 12 IgE and IgG₄ were measured in sera by ELISA and ImmunoCAP, respectively.

RESULTS

At years 2 and 3, TGP-IgA_1/2 levels in nasal fluid were elevated in SLIT compared with SCIT (4.2- and 3.0-fold for IgA₁, 2.0- and 1.8-fold for IgA₂, respectively; all P < .01). TGP-IgA₁ level in serum was elevated in SLIT compared with SCIT at years 1, 2, and 3 (4.6-, 5.1-, and 4.7-fold, respectively; all P < .001). Serum TGP-IgG level was higher in SCIT compared with SLIT (2.8-fold) at year 2. Serum TGP-IgG₄ level was higher in SCIT compared with SLIT at years 1, 2, and 3 (10.4-, 27.4-, and 5.1-fold, respectively; all P < .01). Serum IgG₄ levels to Phl p1, 2, 5b, and 6 were increased at years 1, 2, and 3 in SCIT and SLIT compared with placebo (Phl p1: 11.8- and 3.9-fold; Phl p2: 31.6- and 4.4-fold; Phl p5b: 135.5- and 5.3-fold; Phl p6: 145.4- and 14.7-fold, respectively, all at year 2 when levels peaked; P < .05). IgE to TGP in nasal fluid increased in the SLIT group at year 2 but not at year 3 compared with SCIT (2.8-fold; P = .04) and placebo (3.1-fold; P = .02). IgA to TGP and IgE and IgG₄ to TGP components stratified participants according to treatment group and clinical response.

CONCLUSIONS

The observed induction of IgA_1/2 in SLIT and IgG₄ in SCIT suggest key differences in the mechanisms of action.

Limited access to antigen drives generation of early B cell memory while restraining the plasmablast response

Cell fate decisions during early B cell activation determine the outcome of responses to pathogens and vaccines. We examined the early B cell response to T-dependent antigen in mice by single-cell RNA sequencing. Early after immunization, a homogeneous population of activated precursors (APs) gave rise to a transient wave of plasmablasts (PBs), followed a day later by the emergence of germinal center B cells (GCBCs). Most APs rapidly exited the cell cycle, giving rise to non-GC-derived early memory B cells (eMBCs) that retained an AP-like transcriptional profile. Rapid decline of antigen availability controlled these events; provision of excess antigen precluded cell cycle exit and induced a new wave of PBs. Fate mapping revealed a prominent contribution of eMBCs to the MBC pool. Quiescent cells with an MBC phenotype dominated the early response to immunization in primates. A reservoir of APs/eMBCs may enable rapid readjustment of the immune response when failure to contain a threat is manifested by increased antigen availability.

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.

Peanut allergy: Beyond the oral immunotherapy plateau

BACKGROUND

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

AIM

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

CONCLUSION

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