Germinal Centers

The role of fatty acid metabolism on B cells and B cell-related autoimmune diseases

Fatty acid metabolism plays a critical role in regulating immune cell function, including B cells, which are central to humoral immunity and the pathogenesis of autoimmune diseases. Emerging evidence suggests that fatty acid metabolism influences B cell development, activation, differentiation, and antibody production, thereby impacting B cell-related autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and multiple sclerosis (MS). In this review, we discuss the mechanisms by which fatty acid metabolism modulates B cell biology, including energy provision, membrane composition, and signaling pathways. We highlight how alterations in fatty acid synthesis, oxidation, and uptake affect B cell function and contribute to autoimmune pathogenesis. Additionally, we explore the therapeutic potential of targeting fatty acid metabolism in B cells to treat autoimmune diseases. Understanding the interplay between fatty acid metabolism and B cell immunity may provide novel insights into the development of precision therapies for B cell-mediated autoimmune disorders.

Disease-specific B cell clones are shared between patients with Crohn's disease

B cells have important functions in gut homeostasis, and dysregulated B cell populations are frequently observed in patients with inflammatory bowel diseases, including both ulcerative colitis (UC) and Crohn's disease (CD). How these B cell perturbations contribute to disease remains largely unknown. Here, we perform deep sequencing of the B cell receptor (BCR) repertoire in four cohorts of patients with CD, together with healthy controls and patients with UC. We identify BCR clones that are shared between patients with CD but not found in healthy individuals nor in patients with UC, indicating CD-associated B cell immune responses. Shared clones are present in the inflamed gut mucosa, draining intestinal lymph nodes and blood, suggesting the presence of common CD-associated antigens that drive B cell responses in CD patients.

Rapid and efficient immune response induced by a designed modular cholera toxin B subunit (CTB)-based self-assembling nanoparticle

Modular self-assembling nanoparticle vaccines, represent a cutting-edge approach in immunology with the potential to revolutionize vaccine design and efficacy. Although many innovative efficient modular self-assembling nanoparticles have been designed for vaccination, the immune activation characteristics underlying such strong protection remain poorly understood, limiting the further expansion of such nanocarrier. Here, we prepared a novel modular nanovaccine, which self-assembled via a pentamer cholera toxin B subunit (CTB) domain and an unnatural trimer domain, presenting S. Paratyphi A O-polysaccharide antigen, and investigated its rapid immune activation mechanism. The nanovaccine efficiently targets draining lymph nodes and antigen-presenting cells, facilitating co-localization with Golgi and endoplasmic reticulum. In addition, dendritic cells, macrophages, B cells, and neutrophils potentially participate in antigen presentation, unveiling a dynamic change of the vaccines in lymph nodes. Single-cell RNA sequencing at early stage and iN vivo/iN vitro experiments reveal its potent humoral immune response capabilities and protection effects. This nanoparticle outperforms traditional CTB carriers in eliciting robust prophylactic effects in various infection models. This work not only provides a promising and efficient candidate vaccine, but also promotes the design and application of the new type of self-assembled nanoparticle, offering a safe and promising vaccination strategy for infection diseases.

Rational design of next-generation filovirus vaccines with glycoprotein stabilization, nanoparticle display, and glycan modification

Filoviruses pose a significant threat to human health with frequent outbreaks and high mortality. Although two vector-based vaccines are available for Ebola virus, a broadly protective filovirus vaccine remains elusive. In this study, we evaluate a general strategy for stabilizing glycoprotein (GP) structures of Ebola, Sudan, and Bundibugyo ebolaviruses and Ravn marburgvirus. A 3.2 Å-resolution crystal structure provides atomic details for the redesigned Ebola virus GP, and cryo-electron microscopy reveals how a pan-ebolavirus neutralizing antibody targets a conserved site on the Sudan virus GP (3.13 Å-resolution), in addition to a low-resolution model of antibody-bound Ravn virus GP. A self-assembling protein nanoparticle (SApNP), I3-01v9, is redesigned at the N-terminus to allow the optimal surface display of filovirus GP trimers. Following detailed in vitro characterization, the lymph node dynamics of Sudan virus GP and GP-presenting SApNPs are investigated in a mouse model. Compared with soluble GP trimer, SApNPs show ~112 times longer retention in lymph node follicles, up-to-28 times greater presentation on follicular dendritic cell dendrites, and up-to-3 times stronger germinal center reactions. Functional antibody responses induced by filovirus GP trimers and SApNPs bearing wildtype and modified glycans are assessed in mice. Our study provides a foundation for next-generation filovirus vaccine development.

Impact of Extended Dosing Intervals and Ipsilateral Versus Contralateral Boosting on mRNA Vaccine Immunogenicity in Mice

BACKGROUND

Although mRNA vaccines have the potential to be developed and deployed rapidly to combat infectious diseases, the ideal method of administration and boosting schedule strategy for generating optimal immunogenicity is an area of active research. We compared the immune responses resulting from different schedules for prime-boost and boosting either ipsilaterally or contralaterally in relation to the initial vaccine dose.

METHODS

Influenza hemagglutinin (HA) was used as a model antigen for different vaccination regimens in mice using both mRNA lipid nanoparticles (mRNA-LNP) and AF03-adjuvanted recombinant protein (rHA-AF03) vaccines.

RESULTS

Increasing the prime-boost interval resulted in higher levels of serum anti-HA IgG and functional antibody hemagglutination inhibition (HAI) responses in mRNA-LNP-vaccinated animals, which correlated with an induction of germinal center (GC) B cells and follicular helper T (Tfh) cells in lymph nodes. In addition, longer prime-boost intervals resulted in higher levels of IL-2 and TNF-α producing CD4+ T cells two weeks after boosting. The number of Ig-secreting long-lived plasma cells increased with the length of prime-boost intervals. Contralateral boosting resulted in an increase in HAI titers and GC B cells compared to an ipsilateral boost. However, significantly higher numbers of GC B cells were induced in the draining lymph nodes following ipsilateral boosting than in the non-draining lymph nodes.

CONCLUSIONS

Overall, our data provides insights into the immune mechanisms of action of mRNA-LNP to develop the optimal vaccine regimen for mRNA vaccine platforms.

Novel Meningoencephalomyelitis Associated With Vimentin IgG Autoantibodies

Importance

Autoantibodies targeting astrocytes, such as those against glial fibrillary acidic protein (GFAP) or aquaporin protein 4, are crucial diagnostic markers for autoimmune astrocytopathy among central nervous system (CNS) autoimmune disorders. However, diagnosis remains challenging for patients lacking specific autoantibodies.

Objective

To characterize a syndrome of unknown meningoencephalomyelitis associated with an astrocytic autoantibody.

Design, Setting, and Participants

This retrospective case series study included samples collected from April 2021 to May 2024 at a tertiary referral hospital among patients with uncharacterized CNS autoimmune disorders and similar clinical and radiological features. Single-cell RNA sequencing (scRNA-seq) was performed on cerebrospinal fluid (CSF) cells of 2 index patients to identify the putative target antigen of the clonally expanded B cells. A comprehensive screening for additional patients was conducted using blinded cell-based and tissue-based assay. Candidate patients were followed up for a median (range) duration of 23 (5-31) months.

Exposures

scRNA-seq, autoantibody characterization, and testing.

Main Outcomes and Measures

Detection of the autoantibody and characterization of the associated autoimmune meningoencephalomyelitis.

Results

Fourteen candidate patients (10 [71%] female; median [IQR] age, 33 [23-41] years) were identified. Initially, CSF from 2 female patients with unknown encephalomyelitis showed astrocytic reactivity on rat tissue but was negative for GFAP IgG. A total of 17 of 37 clonally expanded B cell clonotypes (46%) in their CSF expressed IgG autoantibodies targeting the astrocytic intermediate filament protein vimentin. Subsequent screening identified 12 additional patients. These 14 patients shared a unique clinical profile characterized by relapsing courses and symptoms prominently involving the cerebellum, brainstem, and corticospinal tract (CST). All patients also exhibited elevated CSF protein and cells, intrathecal immunoglobulin synthesis, and magnetic resonance imaging (MRI) showing bilateral lesions on CST. Notably, 8 of 12 patients (67%) who received first-line immunotherapy at their first episode responded well. At the last follow-up, 11 patients (79%) experienced significant disability (modified Rankin Scale ≥3).

Conclusions and Relevance

In this case series, autoantibodies targeting the astrocytic intermediate filament protein vimentin were identified in patients with previously undifferentiated meningoencephalomyelitis and common radiographic features.

Metabolic determinants of germinal center B cell formation and responses

Germinal center (GC) B cells are crucial for the generation of GCs and long-lived humoral immunity. Here we report that one-carbon metabolism determines the formation and responses of GC B cells. Upon CD40 stimulation, GC B cells selectively upregulate methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) expression to generate purines and the antioxidant glutathione. MTHFD2 depletion reduces GC B cell frequency and antigen-specific antibody production. Moreover, supplementation with nucleotides and antioxidants suffices to promote GC B cell formation and function in vitro and in vivo through activation of the mammalian target of rapamycin complex 1 signaling pathway. Moreover, we found that antigen stimulation enhances YY1 binding to the Mthfd2 promoter and promotes MTHFD2 transcription. Interestingly, these findings can be generalized to the pentose phosphate pathway, which is another major source of reducing power and nucleotides. Therefore, these results suggest that an increased capacity for nucleotide synthesis and redox balance is required for GC B cell formation and responses, revealing a key aspect of GC B cell fate determination.

Mucosal immunity elicited by a human-Fcγ receptor-I targeted intranasal vaccine platform enhances resistance against nasopharyngeal colonization of Streptococcus pneumoniae and induces broadly protective immunity against respiratory pathogens

The development of safe and effective mucosal vaccines are hampered by safety concerns associated with adjuvants or live attenuated microbes. We previously demonstrated that targeting antigens to the human-Fc-gamma-receptor-I (hFcγRI) eliminates the need for adjuvants, thereby mitigating safety concerns associated with the mucosal delivery of adjuvant formulated vaccines. Here we evaluated the role of the route of immunization in the mucosal immunity elicited by the hFcγRI-targeted vaccine approach. To enable Ag targeting, PspA from Streptococcus pneumoniae (Sp) was genetically fused with the hFcγRI-targeting antibody (α-hFcγRI) to generate PspA-FP. Intranasal (IN) immunization with the PspA-FP induced significantly higher IgA, IgG, and memory T cell response in the lung mucosa compared to that of the intramuscular (IM) route, while both routes exhibited similar increase in the systemic IgG response. The IN immunization elicited better resistance against nasal colonization (NC) of Sp compared to the IM immunization. Additionally, the resistance to NC with the IN administered PspA-FP was higher than the PspA-Alum formulation administered by the IM route. While the protection form lethal pulmonary Sp infection correlated with the systemic Ab response, the resistance from NC (of Sp) correlated with the mucosal immune response. Similar to the pneumococcal pneumoniae model, the hFcγRI-targeted vaccine (based on HA as Ag) was equally protective against pulmonary Influenza virus infection via both routes. However, the IN route promoted better protection compared to the IM route against a lethal pulmonary infection with Francisella tularensis (Ft). The enhanced protection against Ft correlated with the superior mucosal immune response elicited by the IN route compared to the IM route. These observations showed a differential requirement for mucosal delivery for protection depending on the type of pathogen. Moreover, this study revealed that the hFcγRI-targeted vaccine platform is broadly-effective as an adjuvant-free mucosal vaccine platform against respiratory pathogens.

Deep profiling of B cells responding to various pathogens uncovers compartments in IgG memory B cell and antibody-secreting lineages

Improving our understanding of B cell transition to memory B cells (MBCs) and antibody-secreting cells (ASCs) is crucial for clinical monitoring and vaccine strategies. To explore these dynamics, we compared prepandemic antigen responses (influenza hemagglutinin, respiratory syncytial virus fusion glycoprotein, and tetanus toxoid) with recently encountered severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen responses in convalescent COVID-19 patients using spectral flow cytometry. Our analysis revealed the CD43+CD71+IgG+ activated B cell subset, highly enriched for SARS-CoV-2 specificities, as a juncture for ASC and MBC differentiation, with CD86+ phenotypically similar to ASCs and CD86- to IgG+ MBCs. Moreover, subpopulations within IgG+ MBCs were further identified based on CD73 and CD24 expression. Activated MBCs (CD73-/CD24lo) were predominantly SARS-CoV-2-specific, while resting MBCs (CD73+/CD24hi) recognized prepandemic antigens. A CD95- subcluster within resting MBCs accounted for over 40% of prepandemic-specific cells, indicating long-lasting memory. These findings advance our understanding of IgG+ MBC and ASC development stages, shedding light on the decision-making process guiding their differentiation.

Thymic stromal lymphopoietin signaling in B cells from progenitors to plasma cells

Thymic stromal lymphopoietin is an established pleotropic alarmin cytokine that is generated at barrier tissues to induce type 2 immune responses, but its role in regulating the diversity of B cells is poorly understood. Here, we will highlight the key findings that underpin our limited understanding of the role thymic stromal lymphopoietin in modulating different stages of B cell development. We will also provide an overview of how thymic stromal lymphopoietin drives B cell-mediated immune disease and how novel thymic stromal lymphopoietin-blocking biologics could be used to modulate B cell responses. Thymic stromal lymphopoietin is critical for the regulation, diversity, and longevity of humoral immunity.

Enhancing protective immunity against SARS-CoV-2 with a self-amplifying RNA lipid nanoparticle vaccine

RNA-based vaccines against SARS-CoV-2 have demonstrated promising protective immunity against the global COVID-19 epidemic. Enhancing the intensity and duration of mRNA antigen expression is anticipated to markedly boost antiviral immune responses. Self-amplifying RNA (saRNA) represents a next-generation platform for RNA-based vaccines, amplifying transcripts in situ to augment the expression of encoded immunogens. Here, we develop a saRNA nanovaccine, formulated with a mutated saRNA encoding the receptor-binding domain (RBD) of the SARS-CoV-2 spike glycoprotein, encapsulated within a lipid nanoparticle (LNP-saRNA-RBD). This LNP-saRNA vaccine platform enables efficient delivery of saRNA-RBD, inducing enhanced and prolonged expression of the RBD antigen. LNP-saRNA-RBD vaccination stimulated the generation of antigen-specific T cells, promoting their differentiation into a long-lived effector memory phenotype. Immunization with LNP-saRNA-RBD induced a germinal center response in draining lymph nodes, leading to the production of anti-RBD IgG antibodies with the ability to neutralize SARS-CoV-2 pseudovirus. Furthermore, prime-boost immunizations with LNP-saRNA-RBD conferred protection to mice against SARS-CoV-2 challenge by suppressing viral infection and replication, as well as pulmonary inflammatory responses and associated damage. Taken together, these findings provide strong support for advancing the development of LNP-saRNA-RBD as a safe and efficacious vaccine candidate against SARS-CoV-2 infection.

The autoimmune architecture of childhood idiopathic nephrotic syndrome

Idiopathic nephrotic syndrome, the most common glomerular disorder in children, has long been considered an immune-mediated disease based on the efficacy of glucocorticoids at inducing remission. Nevertheless, the immune processes leading to podocytopathy have largely remained elusive. The success of B-cell depletion with rituximab, descriptions of B-cell dysregulation during active disease, and the most recent discovery of autoantibodies targeting the major podocyte antigen nephrin point to an autoimmune humoral etiology for idiopathic nephrotic syndrome. Investigations of the immune factors involved in idiopathic nephrotic syndrome pathogenesis have uncovered common features with other autoimmune disorders that will aid in prognostication and in guiding the expansion of our glucocorticoid-sparing therapeutic arsenal. In this review, we discuss the emerging autoimmune architecture of idiopathic nephrotic syndrome, with a specific focus on pediatric steroid-sensitive disease, including the podocyte-reactive B-cell response that causes anti-podocyte antibodies, the predisposing genetic factors that shape the podocyte-reactive immune landscape, and the immune triggers driving active disease.

Molecular features of the serological IgG repertoire elicited by egg-based, cell-based, or recombinant haemagglutinin-based seasonal influenza vaccines: a comparative, prospective, observational cohort study

BACKGROUND

Egg-based inactivated quadrivalent seasonal influenza vaccine (eIIV4), cell culture-based inactivated quadrivalent seasonal influenza vaccine (ccIIV4), and recombinant haemagglutinin (HA)-based quadrivalent seasonal influenza vaccine (RIV4) have been licensed for use in the USA. In this study, we used antigen-specific serum proteomics analysis to assess how the molecular composition and qualities of the serological antibody repertoires differ after seasonal influenza immunisation by each of the three vaccines and how different vaccination platforms affect the HA binding affinity and breadth of the serum antibodies that comprise the polyclonal response.

METHODS

In this comparative, prospective, observational cohort study, we included female US health-care personnel (mean age 47·6 years [SD 8]) who received a single dose of RIV4, eIIV4, or ccIIV4 during the 2018-19 influenza season at Baylor Scott & White Health (Temple, TX, USA). Eligible individuals were selected based on comparable day 28 serum microneutralisation titres and similar vaccination history. Laboratory investigators were blinded to assignment until testing was completed. The preplanned exploratory endpoints were assessed by deconvoluting the serological repertoire specific to A/Singapore/INFIMH-16-0019/2016 (H3N2) HA before (day 0) and after (day 28) immunisation using bottom-up liquid chromatography-mass spectrometry proteomics (referred to as Ig-Seq) and natively paired variable heavy chain-variable light chain high-throughput B-cell receptor sequencing (referred to as BCR-Seq). Features of the antigen-specific serological repertoire at day 0 and day 28 for the three vaccine groups were compared. Antibodies identified with high confidence in sera were recombinantly expressed and characterised in depth to determine the binding affinity and breadth to time-ordered H3 HA proteins.

FINDINGS

During September and October of the 2018-19 influenza season, 15 individuals were recruited and assigned to receive RIV4 (n=5), eIIV4 (n=5), or ccIIV4 (n=5). For all three cohorts, the serum antibody repertoire was dominated by back-boosted antibody lineages (median 98% [95% CI 88-99]) that were present in the serum before vaccination. Although vaccine platform-dependent differences were not evident in the repertoire diversity, somatic hypermutation, or heavy chain complementarity determining region 3 biochemical features, antibodies boosted by RIV4 showed substantially higher binding affinity to the vaccine H3/HA (median half-maximal effective concentration [EC50] to A/Singapore/INFIMH-16-0019/2016 HA: 0·037 μg/mL [95% CI 0·012-0·12] for RIV4; 4·43 μg/mL [0·030-100·0] for eIIV4; and 18·50 μg/mL [0·99-100·0] μg/mL for ccIIV4) and also the HAs from contemporary H3N2 strains than did those elicited by eIIV4 or ccIIV4 (median EC50 to A/Texas/50/2012 HA: 0·037 μg/mL [0·017-0·32] for RIV4; 1·10 μg/mL [0·045-100] for eIIV4; and 12·6 μg/mL [1·8-100] for ccIIV4). Comparison of B-cell receptor sequencing repertoires on day 7 showed that eIIV4 increased the median frequency of canonical egg glycan-targeting B cells (0·20% [95% CI 0·067-0·37] for eIIV4; 0·058% [0·050-0·11] for RIV4; and 0·035% [0-0·062] for ccIIV4), whereas RIV4 vaccination decreased the median frequency of B-cell receptors displaying stereotypical features associated with membrane proximal anchor-targeting antibodies (0·062% [95% CI 0-0·084] for RIV4; 0·12% [0·066-0·16] for eIIV4; and 0·18% [0·016-0·20] for ccIIV4). In exploratory analysis, we characterised the structure of a highly abundant monoclonal antibody that binds to both group 1 and 2 HAs and recognises the HA trimer interface, despite its sequence resembling the stereotypical sequence motif found in membrane-proximal anchor binding antibodies.

INTERPRETATION

Although all three licensed seasonal influenza vaccines elicit serological antibody repertoires with indistinguishable features shaped by heavy imprinting, the RIV4 vaccine selectively boosts higher affinity monoclonal antibodies to contemporary strains and elicits greater serum binding potency and breadth, possibly as a consequence of the multivalent structural features of the HA immunogen in this vaccine formulation. Collectively, our findings show advantages of RIV4 vaccines and more generally highlight the benefits of multivalent HA immunogens in promoting higher affinity serum antibody responses.

FUNDING

Centers for Disease Control and Prevention, National Institutes of Health, and Bill & Melinda Gates Foundation.

Dynamic roles of tumor-infiltrating B lymphocytes in cancer immunotherapy

The amazing diversity of B cells within the tumor microenvironment is the basis for the diverse development of B cell-based immunotherapies. Here, we focus on elucidating the mechanisms of tumor intervention mediated by four tumor-infiltrating B lymphocytes. Naive B cells present the initial antigen, germinal center B cell subsets enhance antibody affinity, and immunoglobulin subtypes exert multiple immune effects, while regulatory B cells establish immune tolerance. Together they reflect the complexity of the changing dynamics of cancer immunity. Additionally, we have investigated the dynamic effects of tumor-infiltrating B lymphocytes in immunotherapy and their relationship to prognosis, providing new insights into potential treatment strategies for patients.

Dynamic Activation of NADPH Oxidases in Immune Responses Modulates Differentiation, Function, and Lifespan of Plasma Cells

NADPH-oxidase (NOX)-derived reactive oxygen species (ROS) have been described to play essential roles in B-cell activation processes. However, several key questions concerning NOX activity and subsequent ROS production remain unaddressed, including fundamental processes such as differentiation, functional competence, cellular metabolism, and viability. This study investigated these questions in a murine B-cell response after secondary immunization. We combined single-cell transcriptomics and single-cell detection of NOX activity and observed that various subsets of B cells dynamically express NOX1 and NOX2. The NOX+ cellular phenotype correlated with increased activity of metabolic pathways, augmented lactate production, lower IgG secretion rates, and markers for longevity. The NOX+ cellular phenotype was also associated with increased cellular stress and apoptosis, underscoring the intricate relationship between ROS and cellular survival. Consequently, these insights advance our understanding of how long-lived humoral immunity is formed.

Based on the immune system: the role of the IL-2 family in pancreatic disease

The IL-2 family, consisting of IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21, is a key regulator of the immune response. As an important endocrine and digestive organ, the function of the pancreas is regulated by the immune system. Studies have shown that each cytokine of the IL-2 family influences the occurrence and development of pancreatic diseases by participating in the regulation of the immune system. In this paper, we review the structural and functional characteristics of IL-2 family members, focus on their molecular mechanisms in pancreatic diseases including acute pancreatitis, chronic pancreatitis and pancreatic cancer, and highlight the importance of the related proteins in the regulation of immune response and disease progression, which will provide valuable insights for new biomarkers in pancreatic diseases, early diagnosis of the diseases, assessment of the disease severity, and development of new therapeutic regimens. The insights of the study are summarized in the following sections.

Characterization of TCRβ and IGH Repertoires in the Spleen of Two Chicken Lines with Differential ALV-J Susceptibility Under Normal and Infection Conditions

This study investigates the immunological factors underlying the differential susceptibility of two chicken strains, E- and M-lines, to avian leukosis virus subgroup J (ALV-J). During the eradication of avian leukosis at a chicken breeder farm in Guangdong, we observed strain-specific differences in susceptibility to ALV-J. Moreover, E-line chickens exhibited a slower antibody response to ALV-J compared to M-line chickens. As the T cell receptor (TCR) and B cell receptor (BCR) are critical for antigen recognition, their activation triggers specific immune responses, including antibody production. Using high-throughput sequencing, we characterized the T cell receptor beta (TCRβ) and immunoglobulin heavy chain (IGH) repertoires in spleen tissues from both chicken strains. The M-line demonstrated higher clonal diversity in both TCRβ and IGH repertoires under normal conditions compared to the E-line, suggesting a broader baseline antigen recognition capacity. Following ALV-J infection, the TCRβ repertoire diversity remained unchanged, while the IGH repertoire displayed distinct clonal expansion patterns and complementarity-determining region 3 (CDR3) length distributions between the two lines, potentially affecting their ability to recognize ALV-J antigens. Our study provides the first comprehensive comparison of TCRβ and IGH repertoire dynamics in chickens with different ALV-J susceptibilities, offering new insights into the molecular and immunological mechanisms underlying resistance to ALV-J.

ARID1A mutations protect follicular lymphoma from FAS-dependent immune surveillance by reducing RUNX3/ETS1-driven FAS-expression

The cell death receptor FAS and its ligand (FASLG) play crucial roles in the selection of B cells during the germinal center (GC) reaction. Failure to eliminate potentially harmful B cells via FAS can lead to lymphoproliferation and the development of B cell malignancies. The classic form of follicular lymphoma (FL) is a prototypic GC-derived B cell malignancy, characterized by the t(14;18)(q32;q21)IGH::BCL2 translocation and overexpression of antiapoptotic BCL2. Additional alterations were shown to be clinically relevant, including mutations in ARID1A. ARID1A is part of the SWI/SNF nucleosome remodeling complex that regulates DNA accessibility ("openness"). However, the mechanism how ARID1A mutations contribute to FL pathogenesis remains unclear. We analyzed 151 FL biopsies of patients with advanced-stage disease at initial diagnosis and found that ARID1A mutations were recurrent and mainly disruptive, with an overall frequency of 18%. Additionally, we observed that ARID1A mutant FL showed significantly lower FAS protein expression in the FL tumor cell population. Functional experiments in BCL2-translocated lymphoma cells demonstrated that ARID1A is directly involved in the regulation of FAS, and ARID1A loss leads to decreased FAS protein and gene expression. However, ARID1A loss did not affect FAS promotor openness. Instead, we identified and experimentally validated a previously unknown co-transcriptional complex consisting of RUNX3 and ETS1 that regulates FAS expression, and ARID1A loss leads to reduced RUNX3 promotor openness and gene expression. The reduced FAS levels induced by ARID1A loss rendered lymphoma cells resistant to both soluble and T cell membrane-anchored FASLG-induced apoptosis, and significantly diminished CAR T cell killing in functional experiments. In summary, we have identified a functionally and clinically relevant mechanism how FL cells can escape FAS-dependent immune surveillance, which may also impact the efficacy of T cell-based therapies, including CAR T cells.

Epistatic hotspots organize antibody fitness landscape and boost evolvability

The course of evolution is strongly shaped by interaction between mutations. Such epistasis can yield rugged sequence-function maps and constrain the availability of adaptive paths. While theoretical intuition is often built on global statistics of large, homogeneous model landscapes, mutagenesis measurements necessarily probe a limited neighborhood of a reference genotype. It is unclear to what extent local topography of a real epistatic landscape represents its global shape. Here, we demonstrate that epistatic landscapes can be heterogeneously rugged and this heterogeneity may render biomolecules more evolvable. By characterizing a multipeaked fitness landscape of a SARS-CoV-2 antibody mutant library, we show that heterogeneous ruggedness arises from sparse epistatic hotspots, whose mutation impacts the fitness effect of numerous sequence sites. Surprisingly, mutating an epistatic hotspot may enhance, rather than reduce, the accessibility of the fittest genotype, while increasing the overall ruggedness. Further, migratory constraints in real space alleviate mutational constraints in sequence space, which not only diversify direct paths taken but may also turn a road-blocking fitness peak into a stepping stone leading toward the global optimum. Our results suggest that a hierarchy of epistatic hotspots may organize the fitness landscape in such a way that path-orienting ruggedness confers global smoothness.

A machine learning model and identification of immune infiltration for chronic obstructive pulmonary disease based on disulfidptosis-related genes

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a chronic and progressive lung disease. Disulfidptosis-related genes (DRGs) may be involved in the pathogenesis of COPD. From the perspective of predictive, preventive, and personalized medicine (PPPM), clarifying the role of disulfidptosis in the development of COPD could provide a opportunity for primary prediction, targeted prevention, and personalized treatment of the disease.

METHODS

We analyzed the expression profiles of DRGs and immune cell infiltration in COPD patients by using the GSE38974 dataset. According to the DRGs, molecular clusters and related immune cell infiltration levels were explored in individuals with COPD. Next, co-expression modules and cluster-specific differentially expressed genes were identified by the Weighted Gene Co-expression Network Analysis (WGCNA). Comparing the performance of the random forest (RF), support vector machine (SVM), generalized linear model (GLM), and eXtreme Gradient Boosting (XGB), we constructed the ptimal machine learning model.

RESULTS

DE-DRGs, differential immune cells and two clusters were identified. Notable difference in DRGs, immune cell populations, biological processes, and pathway behaviors were noted among the two clusters. Besides, significant differences in DRGs, immune cells, biological functions, and pathway activities were observed between the two clusters.A nomogram was created to aid in the practical application of clinical procedures. The SVM model achieved the best results in differentiating COPD patients across various clusters. Following that, we identified the top five genes as predictor genes via SVM model. These five genes related to the model were strongly linked to traits of the individuals with COPD.

CONCLUSION

Our study demonstrated the relationship between disulfidptosis and COPD and established an optimal machine-learning model to evaluate the subtypes and traits of COPD. DRGs serve as a target for future predictive diagnostics, targeted prevention, and individualized therapy in COPD, facilitating the transition from reactive medical services to PPPM in the management of the disease.

A Small-Molecule BCL6 Inhibitor as an Anti-Proliferative Agent for Diffuse Large B-Cell Lymphoma

The B-cell lymphoma 6 (BCL6) transcription factor plays a key role in the establishment of germinal center (GC) formation. Diffuse large B-cell lymphoma (DLBCL) originates from the GC reaction due to dysregulation of BCL6. Disrupting BCL6 and its corepressors' interaction has become the foundation for rationally designing lymphoma therapies. However, BCL6 inhibitors with good activities in vitro and in vivo are rare, and there are no clinically approved BCL6 inhibitors. In this study, we discovered and developed a novel range of [1,2,4] triazolo[1,5-a] pyrimidine derivatives targeting BCL6/SMRT interaction. The lead compound WK692 directly bound BCL6BTB, disrupted BCL6BTB/SMRT interaction and activated the expression of BCL6 downstream genes inside cells, inhibited DLBCL growth and induced apoptosis in vitro, inhibited GC formation, decreased the proportion of follicular helper T cells, and impaired Ig affinity maturation. Further studies showed that WK692 inhibits DLBCL growth without toxic effects in vivo and synergizes with the EZH2 and PRMT5 inhibitors. Our results demonstrated that WK692 as a BCL6 inhibitor may be developed as a novel potential anticancer agent against DLBCL.

Regulation of the IgE response by T follicular regulatory cells

Allergen-specific IgE is a major mediator of allergic responses and contributes greatly to allergic disease in the human population. Therapies that inhibit the production of IgE would be useful for lessening the burden of allergic disease. A great deal of research has focused on how IgE responses are regulated, and several factors that promote the production of allergic IgE have been characterized. T follicular helper (TFH) cells expressing IL-4 are required for the development of IgE expressing B cells in the germinal center (GC). Ig somatic hypermutation and B cell selection in the GC leads to the development of high affinity allergen-specific IgE that promotes anaphylaxis, a severe form of allergic response. T follicular regulatory (TFR) cells are also found in the GC response and act with TFH cells in the selection of high affinity IgE + B cells. This review examines the current literature on IgE responses and TFR cells. In mouse studies, TFR cells have a suppressive role on IgE responses in allergic airway disease, however TFR cells also play a helper role in the IgE response in food allergy. In human studies, TFR cells correlate with a decreased allergic response but evidence for a direct suppressive role of TFR cells on IgE in vivo is lacking. TFR cells may represent a new target for allergy therapies, but caution must be exercised to promote the suppressor activity of TFR cells and not the helper activity of TFR cells on IgE responses.

Immunogenicity of Therapeutic Antibodies Used for Inflammatory Bowel Disease: Treatment and Clinical Considerations

The introduction of tumor necrosis factor inhibitors has led to a paradigm shift in the management of inflammatory bowel disease (IBD). The subsequent introduction of both anti-integrins and cytokine blockers has since expanded the biologic armamentarium. However, immunogenicity, defined as the production of anti-drug antibodies (ADAs) to the prescribed biopharmaceutical, means a significant fraction of patients exposed to biologic agents will experience a secondary loss of response to one or more of the drugs. In clinical settings, immunogenicity may be caused by several factors, both patient related (e.g., underlying chronic disease, systemic immune burden, including previous biologic therapy failure, and [epi]genetic background) and treatment related (e.g., dose and administration regimens, drug physical structure, photostability, temperature, and agitation). Here, we outline these elements in detail to enhance biopharmaceutical delivery and therapy for patients with IBD. Moreover, concurrent immunomodulator medication may reduce the risks of ADA generation, especially when using the chimeric drug infliximab. Summarizing the latest developments and knowledge in the field, this review aims to provide strategies to prevent ADA production and information on managing non-responsiveness or loss of response to biologics. Better understanding of the molecular mechanisms underlying the formation of ADAs and the critical factors influencing the immunogenicity of biopharmaceuticals may lead to improved health outcomes in the IBD community that may benefit both the individual patient and society through lower healthcare expenses.

Analysis of Germinal Center Reaction in Competitive Bone Marrow Chimeric Rag2-/-γc-/-Mice

Germinal center (GC) reaction is crucial for the generation of high-affinity antibodies against any infection. To address the role of specific genes in GC, knockout mouse models are generally used. However, since GC is a multicellular event, complete knockout models cannot pinpoint the cell-intrinsic effect of certain genes in GC reaction. Here, we describe a detailed protocol for the analysis of GC in competitive bone marrow (BM) chimeric mice generated by transplanting 1:1 mixture of CD45.1 and CD45.2 positive donor bone marrow (BM) cells in immunodeficient Rag2-/-γc-/- mice as recipient host. We describe the method of immunization using sheep red blood cells (SRBC), detection of successful immunization by the antigen-specific antibody titer in the serum of the immunized mice and finally assessing the GC reaction in the spleen of the immunized mice by flow cytometry 10 days post-immunization. When the competitive chimera is made with wild type (WT) and a knockout (KO) donor BM, this method is suitable to address the cell type-specific (e.g., B-cell specific) role of the KO gene in GC.

Enhancing the Deformability of the Adjuvant: Achieving Lymph Node Targeted Delivery to Elicit a Long-Lasting Immune Protection

A key challenge in vaccine development is to induce an effective and durable immune response. Live virus vaccines induce lifelong antibody responses; however, the immune responses induced by inactivated or subunit vaccines decrease gradually. Activation of the germinal center (GC) reaction, which generates long-lived plasma cells (LLPCs), is a key mediator of long-term antibody responses. To enhance the activation of GC, lymph node-targeted delivery of the vaccine is promoted by enhancing the deformability of the delivery vector. In this study, a double emulsion is designed with strong deformability and containing chitosan nanoparticles (CSNP) in the internal aqueous phase (WNP) for efficient antigen loading, called WNP/O/W. The flexible oil layer and the internally loaded positively charged particles endow the emulsion with strong deformability, continuously enrich model antigen ovalbumin (OVA) in the lymph nodes, activate germinal center B (GC B) cells and T follicular helper (TFH) cells, induce LLPCs, and obtain high-level antibody persistence for more than 5 months, which is significantly better than the traditional oil emulsion adjuvant. Concurrently, it also improves the immune-protective effect in aged mice. Altogether, these results indicate that WNP/O/W achieves lymph node targeted delivery by strengthening deformability, generating high-intensity antibody responses, and long-lasting immune protection.

Adoptive Transfer of B Cells In Vivo for Assessment of Their Immune Function

B lymphocytes are a critical part of the adaptive immune response elicited by the immune system to fight various pathogens. The main effector function of the B lymphocytes is the ability to secrete antibodies, whether nonclass-switched immunoglobulin M (IgM) or class-switched immunoglobulin isotypes. To understand the function of B cells in vivo, mice are subjected to bone marrow depletion (using radiation or chemical radiation) before being adoptively transferred with donor bone marrow. Alternatively, B cells can be isolated from spleens and adoptively transferred to B-cell-deficient recipient mice to demonstrate function. In this chapter, we will outline the protocol used to isolate and transfer B cells to B-cell-deficient (μMT-/-) mice in vivo to study their functions.

Single-cell transcriptomics of pediatric Burkitt lymphoma reveals intra-tumor heterogeneity and markers of therapy resistance

Burkitt lymphoma (BL) is the most frequent B-cell lymphoma in pediatric patients. While most patients are cured, a fraction of them are resistant to therapy. To investigate BL heterogeneity and the features distinguishing therapy responders (R) from non-responders (NR), we analyzed by single-cell (sc)-transcriptomics diagnostic EBV-negative BL specimens. Analysis of the non-tumor component revealed a predominance of immune cells and a small representation of fibroblasts, enriched in NR. Tumors displayed patient-specific features, as well as shared subpopulations that expressed transcripts related to cell cycle, signaling pathways and cell-of-origin signatures. Several transcripts were differentially expressed in R versus NR. The top candidate, Tropomyosin 2 (TPM2), a member of the tropomyosin actin filament binding protein family, was confirmed to be significantly higher in NR both at the transcript and protein level. Stratification of patients based on TPM2 expression at diagnosis significantly correlated with prognosis, independently of TP53 mutations. These results indicate that BL displays transcriptional heterogeneity and identify candidate biomarkers of therapy resistance.

Metabolic rewiring controlled by HIF-1α tunes IgA-producing B-cell differentiation and intestinal inflammation

Germinal centers where B cells undergo clonal expansion and antibody affinity maturation are hypoxic microenvironments. However, the function of hypoxia-inducible factor (HIF)-1α in immunoglobulin production remains incompletely characterized. Here, we demonstrated that B cells lacking HIF-1α exhibited significantly lower glycolytic metabolism and impaired IgA production. Loss of HIF-1α in B cells affects IgA-producing B-cell differentiation and exacerbates dextran sodium sulfate (DSS)-induced colitis. Conversely, promoting HIF-1α stabilization via a PHD inhibitor roxadustat enhances IgA class switching and alleviates intestinal inflammation. Mechanistically, HIF-1α facilitates IgA class switching through acetyl-coenzyme A (acetyl-CoA) accumulation, which is essential for histone H3K27 acetylation at the Sα region. Consequently, supplementation with acetyl-CoA improved defective IgA production in Hif1a-deficient B cells and limited experimental colitis. Collectively, these findings highlight the critical importance of HIF-1α in IgA class switching and the potential for targeting the HIF-1α-dependent metabolic‒epigenetic axis to treat inflammatory bowel diseases and other inflammatory disorders.

FB5P-seq-mAbs: monoclonal antibody production from FB5P-seq libraries for integrative single-cell analysis of B cells

Parallel analysis of phenotype, transcriptome and antigen receptor sequence in single B cells is a useful method for tracking B cell activation and maturation during immune responses. However, in most cases, the specificity and affinity of the B cell antigen receptor cannot be inferred from its sequence. Antibody cloning and expression from single B cells is then required for functional assays. Here we propose a method that integrates FACS-based 5'-end single-cell RNA sequencing (FB5P-seq) and monoclonal antibody cloning for integrative analysis of single B cells. Starting from a cell suspension, single B cells are FACS-sorted into 96-well plates for reverse transcription, cDNA barcoding and amplification. A fraction of the single-cell cDNA is used for preparing 5'-end RNA-seq libraries that are sequenced for retrieving transcriptome-wide gene expression and paired BCR sequences. The archived cDNA of selected cells of interest is used as input for cloning heavy and light chain variable regions into antibody expression plasmid vectors. The corresponding monoclonal antibodies are produced by transient transfection of a eukaryotic producing cell line and purified for functional assays. We provide detailed step-by-step instructions and describe results obtained on ovalbumin-specific murine germinal center B cells after immunization. Our method is robust, flexible, cost-effective, and applicable to different B cell types and species. We anticipate it will be useful for mapping antigen specificity and affinity of rare B cell subsets characterized by defined gene expression and/or antigen receptor sequence.

Maintenance and functional regulation of immune memory to COVID-19 vaccines in tissues

Memory T and B cells in tissues are essential for protective immunity. Here, we performed a comprehensive analysis of the tissue distribution, phenotype, durability, and transcriptional profile of COVID-19 mRNA vaccine-induced immune memory across blood, lymphoid organs, and lungs obtained from 63 vaccinated organ donors aged 23-86, some of whom experienced SARS-CoV-2 infection. Spike (S)-reactive memory T cells were detected in lymphoid organs and lungs and variably expressed tissue-resident markers based on infection history, and S-reactive B cells comprised class-switched memory cells resident in lymphoid organs. Compared with blood, S-reactive tissue memory T cells persisted for longer times post-vaccination and were more prevalent with age. S-reactive T cells displayed site-specific subset compositions and functions: regulatory cell profiles were enriched in tissues, while effector and cytolytic profiles were more abundant in circulation. Our findings reveal functional compartmentalization of vaccine-induced T cell memory where surveilling effectors and in situ regulatory responses confer protection with minimal tissue damage.

Minimal framework for optimizing vaccination protocols targeting highly mutable pathogens

A persistent public health challenge is identifying immunization schemes that are effective against highly mutable pathogens such as HIV and influenza viruses. To address this, we analyze a simplified model of affinity maturation, the Darwinian evolutionary process B cells undergo during immunization. The vaccination protocol determines the selection forces that steer affinity maturation to generate antibodies. We focus on identifying the optimal selection forces exerted by a generic time-dependent vaccination protocol to maximize the production of broadly neutralizing antibodies (bnAbs) that can protect against a broad spectrum of pathogen strains. The model utilizes a path integral representation and operator approximations within a mean-field limit and provides guiding principles for optimizing time-dependent vaccine-induced selection forces to enhance bnAb generation. We compare our analytical mean-field results with the outcomes of stochastic simulations, and we discuss their similarities and differences.

Vascular injury derived apoptotic exosome-like vesicles trigger autoimmunity

According to a central tenet of classical immune theory, a healthy immune system must avoid self-reactive lymphocyte clones but we now know that B cells repertoire exhibit some level of autoreactivity. These autoreactive B cells are thought to rely on self-ligands for their clonal selection and survival. Here, we confirm that healthy mice exhibit self-reactive B cell clones that can be stimulated in vitro by agonists of toll-like receptor (TLR) 1/2, TLR4, TLR7 and TLR9 to secrete anti-LG3/perlecan. LG3/perlecan is an antigen packaged in exosome-like structures released by apoptotic endothelial cells (ApoExos) upon vascular injury. We demonstrate that the injection of ApoExos in healthy animals activates the IL-23/IL-17 pro-inflammatory and autoimmune axis, and produces several autoantibodies, including anti-LG3 autoantibodies and hallmark autoantibodies found in systemic lupus erythematosus. We also identify γδT cells as key mediators of the maturation of ApoExos-induced autoantibodies in healthy mice. Altogether we show that ApoExos released by apoptotic endothelial cells display immune-mediating functions that can stimulate the B cells in the normal repertoire to produce autoantibodies. Our work also identifies TLR activation and γδT cells as important modulators of the humoral autoimmune response induced by ApoExos.

Neonatal immunity associated with heterologous HIV-1 neutralizing antibody induction in SHIV-infected Rhesus Macaques

The details of the pediatric immune system that supports induction of antibodies capable of neutralizing geographically-diverse or heterologous HIV-1 is currently unclear. Here we explore the pediatric immune environment in neonatal macaque undergoing Simian-HIV infection. Simian-HIV infection of 11 pairs of therapy-naive dams and infant rhesus macaques for 24 months results in heterologous HIV-1 neutralizing antibodies in 64% of young macaques compared to 18% of adult macaques. Heterologous HIV-1 neutralizing antibodies emerge by 12 months post-infection in young macaques, in association with lower expression of immunosuppressive genes, fewer germinal center CD4 + T regulatory cells, and a lower ratio of CD4 + T follicular regulatory to helper cells. Antibodies from peripheral blood B cells in two young macaques following SHIV infection neutralize 13% of 119 heterologous HIV-1 strains and map to regions of canonical broadly neutralizing antibody epitopes on the envelope surface protein. Here we show that pediatric immunity to SHIV infection in a macaque model may inform vaccine strategies to induce effective HIV-1 neutralizing antibodies in infants and children prior to viral exposure.

IL-7 promotes mRNA vaccine-induced long-term immunity

Messenger RNA (mRNA) vaccines are a key technology in combating existing and emerging infectious diseases. However, improving the immunogenicity and durability of mRNA vaccines remains a challenge. To elicit optimal immune responses, integrating antigen-encoded mRNA and immunostimulatory adjuvants into a single formulation is a promising approach to enhancing the efficacy of mRNA vaccines. Here, we report an adjuvant strategy to enhance the efficacy of mRNA vaccines by co-loading mRNA encoding the antigen (rabies virus glycoprotein, RABV-G) and mRNA encoding IL-7 into lipid nanoparticles, achieving co-delivery to the same antigen-presenting cells. A single immunization with G&IL-7 mRNA vaccine elicited robust humoral immune responses in mice and conferred complete protection against RABV challenge. Notably, the high levels of neutralizing antibody induced by the G&IL-7 mRNA vaccine were maintained for at least 6 months, providing mice with long-term significant and complete protection against RABV. Additionally, IL-7 also enhanced antibody responses against the SARS-CoV-2. These data demonstrate that IL-7 is a potent mRNA vaccine adjuvant that can provide the required immune stimulation in various mRNA vaccine formulations.

Rack1 regulates B-cell development and function by binding to and stabilizing the transcription factor Pax5

The transcription factor Pax5 activates genes essential for B-cell development and function. However, the regulation of Pax5 expression remains elusive. The adaptor Rack1 can interact with multiple transcription factors and modulate their activation and/or stability. However, its role in the transcriptional control of B-cell fates is largely unknown. Here, we show that CD19-driven Rack1 deficiency leads to pro-B accumulation and a simultaneous reduction in B cells at later developmental stages. The generation of bone marrow chimeras indicates a cell-intrinsic role of Rack1 in B-cell homeostasis. Moreover, Rack1 augments BCR and TLR signaling in mature B cells. On the basis of the aberrant expression of Pax5-regulated genes, including CD19, upon Rack1 deficiency, further exploration revealed that Rack1 maintains the protein level of Pax5 through direct interaction and consequently prevents Pax5 ubiquitination. Accordingly, Mb1-driven Rack1 deficiency almost completely blocks B-cell development at the pro-B-cell stage. Ectopic expression of Pax5 in Rack1-deficient pro-B cells partially rescues B-cell development. Thus, Rack1 regulates B-cell development and function through, at least partially, binding to and stabilizing Pax5.

A guide to adaptive immune memory

Immune memory - comprising T cells, B cells and plasma cells and their secreted antibodies - is crucial for human survival. It enables the rapid and effective clearance of a pathogen after re-exposure, to minimize damage to the host. When antigen-experienced, memory T cells become activated, they proliferate and produce effector molecules at faster rates and in greater magnitudes than antigen-inexperienced, naive cells. Similarly, memory B cells become activated and differentiate into antibody-secreting cells more rapidly than naive B cells, and they undergo processes that increase their affinity for antigen. The ability of T cells and B cells to form memory cells after antigen exposure is the rationale behind vaccination. Understanding immune memory not only is crucial for the design of more-efficacious vaccines but also has important implications for immunotherapies in infectious disease and cancer. This 'guide to' article provides an overview of the current understanding of the phenotype, function, location, and pathways for the generation, maintenance and protective capacity of memory T cells and memory B cells.

B cell αv integrin regulates germinal center derived lung-resident IgA B cell responses following influenza virus infection

Emerging studies have highlighted the importance of tissue-resident B cells in the lungs, for protective immunity against respiratory viruses. However, the mechanisms controlling generation and maintenance of such tissue-resident B cells at respiratory sites remain obscure. We have previously shown that αv integrins limit B cell responses to antigens containing Toll-like receptor ligands, and that deletion of B cell αv integrins, in mice, enhances germinal center (GC)-derived long-lived B cell responses after systemic immunization with viral antigens. Here we investigated whether αv also regulates B cell responses at the respiratory tract during viral infection. Our data show that αv integrin restricts tissue-resident B cell responses in the airway, and that deletion of B cell αv promotes generation of lung-resident IgA B cell responses following influenza A virus (IAV) infection. Investigating the mechanism for this, we found that loss of B cell αv, promotes persistence of GC reactions locally in the lungs, which leads to increases in lung-resident IgA+ memory B cells, cross-reactive to antigenic variants. Thus, these studies reveal how IgA B cells are maintained in the lungs and point to a new strategy to improve the durability of lung-resident IgA B cell responses for IAV vaccine efficacy.

Advancements in mammalian display technology for therapeutic antibody development and beyond: current landscape, challenges, and future prospects

The evolving development landscape of biotherapeutics and their growing complexity from simple antibodies into bi- and multi-specific molecules necessitates sophisticated discovery and engineering platforms. This review focuses on mammalian display technology as a potential solution to the pressing challenges in biotherapeutic development. We provide a comparative analysis with established methodologies, highlighting key aspects of mammalian display technology, including genetic engineering, construction of display libraries, and its pivotal role in hit selection and/or developability engineering. The review delves into the mechanisms underpinning developability-driven selection via mammalian display and their broader implications. Applications beyond antibody discovery are also explored, alongside advancements towards function-first screening technologies, precision genome engineering and AI/ML-enhanced libraries, situating them in the context of mammalian display. Overall, the review provides a comprehensive overview of the current mammalian display technology landscape, underscores the expansive potential of the technology for biotherapeutic development, addresses the critical challenges for the full realisation of this potential, and examines advances in related disciplines that might impact the future application of mammalian display technologies.

Physical extraction of antigen and information

To respond and adapt, cells use surface receptors to sense environmental cues. While biochemical signal processing inside the cell is studied in depth, less is known about how physical processes during cell-cell contact impact signal acquisition. New experiments found that fast-evolving immune B cells in germinal centers (GCs) apply force to acquire antigen clusters prior to internalization, suggesting adaptive benefits of physical information extraction. We present a theory of stochastic antigen transfer and show that maximizing information gain via physical extraction can explain the dramatic phenotypic transition from naive to GC B cells-attenuated receptor signaling, enhanced force usage, and decentralized contact architecture. Our model suggests that binding-lifetime measurement and physical extraction serve as complementary modes of antigen recognition, greatly extending the dynamic range of affinity discrimination when combined. This physical-information framework further predicts that the optimal size of receptor clusters decreases as affinity improves, rationalizing the use of a multifocal synaptic pattern seen in GC B cells. By linking extraction dynamics to selection fidelity via discriminatory performance, we propose that cells may physically enhance information acquisition to sustain adaptive evolution.

Two-dose priming immunization amplifies humoral immunity by synchronizing vaccine delivery with the germinal center response

Prolonging exposure to subunit vaccines during the primary immune response enhances humoral immunity. Escalating-dose immunization (EDI), administering vaccines every other day in an increasing pattern over 2 weeks, is particularly effective but challenging to implement clinically. Here, using an HIV Env trimer/saponin adjuvant vaccine, we explored simplified EDI regimens and found that a two-shot regimen administering 20% of the vaccine followed by the remaining 80% of the dose 7 days later increased TFH responses 6-fold, antigen-specific germinal center (GC) B cells 10-fold, and serum antibody titers 10-fold compared with bolus immunization. Computational modeling of TFH priming and the GC response suggested that enhanced activation/antigen loading on dendritic cells and increased capture of antigen delivered in the second dose by follicular dendritic cells contribute to these effects, predictions we verified experimentally. These results suggest that a two-shot priming approach can be used to substantially enhance responses to subunit vaccines.

The emergence of circulating activated autoreactive desmoglein 3-specific follicular regulatory T cells is associated with long-term efficacy of rituximab in patients with pemphigus vulgaris

BACKGROUND

Pemphigus vulgaris (PV) is characterized by autoantibodies targeting keratinocyte adhesion proteins desmoglein (Dsg) 1 and 3, and by the human leukocyte antigen (HLA) predisposition allele HLA-DRB1*0402. Treatment using rituximab (RTX) combined with short-term corticosteroids (CS) allows disease control and long-lasting remission.

OBJECTIVES

The principal aim of this study was to evaluate the impact of RTX on the circulating subpopulations of Dsg3-specific T lymphocytes that specifically regulate B-cell responses: follicular helper T (Tfh) and follicular regulatory T (Tfr) lymphocytes.

METHODS

Using the HLA-DRB1*0402 tetramer loaded with the Dsg3 immunodominant peptide, we used flow cytometry to analyse the frequency, polarization and activation status of blood Dsg3-specific follicular T-cell populations at baseline, month (M) 6 and long-term follow-up (M60-90) from patients with PV.

RESULTS

At baseline, we observed a predominance of Tfh1* and Tfh17 subsets and an underrepresentation of the Tfh2 subset among autoreactive Dsg3-specific Tfh cells compared with nonautoreactive Tfh cells. RTX treatment induced a decrease of autoreactive Tfh cells with no effect on their polarization during follow-up. In parallel, we observed the emergence of a Dsg3-specific Tfr subpopulation with a significant overexpression of the surface activation markers PD1, ICOS and CD25 that was not observed at the surface of autoreactive Tfh and nonautoreactive Tfr cells of the same patients with PV. In contrast, very few Dsg3-specific Tfr cells were observed in patients with PV who were treated with CS alone.

CONCLUSIONS

Here we show that the emergence of circulating autoreactive Dsg3-specific Tfr cells is associated with the long-term efficacy of RTX in patients with PV.

GRAPHICAL ABSTRACT

Sputnik V-Induced Antibodies against SARS-CoV-2 Variants during the Dissemination of the Gamma Variant in Venezuela

The COVID-19 pandemic was characterized by the emergence and succession of SARS-CoV-2 variants able to evade the antibody response induced by natural infection and vaccination. To evaluate the IgG reactivity and neutralizing capacity of the serum of individuals vaccinated with Sputnik V (105 volunteers vaccinated) against different viral variants. IgG reactivity to the Spike protein (S) was evaluated by ELISA. A plaque reduction neutralization test was performed using different viral variant isolates. At 42 days post-vaccination, the frequency of recognition and reactivity to the S protein of the Omicron variant was lower compared to that of the other variants. In general, a higher average neutralization titer was seen against the ancestral variant compared to the variants, especially Omicron. However, some sera exhibited a higher neutralization titer to the Gamma variant compared to the ancestral variant, suggesting unapparent exposure during the clinical trial. Antibodies induced by Sputnik V can recognize, persist, and neutralize SARS-CoV-2 variants, with Omicron being the one that best evades this response. These results represent a unique report on the humoral response induced by a globally lesser-studied vaccine in terms of efficacy and immune escape, offering insights into developing vaccines targeting unknown coronaviruses.

Isotype-aware inference of B cell clonal lineage trees from single-cell sequencing data

Single-cell RNA sequencing (scRNA-seq) enables comprehensive characterization of the micro-evolutionary processes of B cells during an adaptive immune response, capturing features of somatic hypermutation (SHM) and class switch recombination (CSR). Existing phylogenetic approaches for reconstructing B cell evolution have primarily focused on the SHM process alone. Here, we present tree inference of B cell clonal lineages (TRIBAL), an algorithm designed to optimally reconstruct the evolutionary history of B cell clonal lineages undergoing both SHM and CSR from scRNA-seq data. Through simulations, we demonstrate that TRIBAL produces more comprehensive and accurate B cell lineage trees compared to existing methods. Using real-world datasets, TRIBAL successfully recapitulates expected biological trends in a model affinity maturation system while reconstructing evolutionary histories with more parsimonious class switching than state-of-the-art methods. Thus, TRIBAL significantly improves B cell lineage tracing, useful for modeling vaccine responses, disease progression, and the identification of therapeutic antibodies.

Harnessing the potential of the NALT and BALT as targets for immunomodulation using engineering strategies to enhance mucosal uptake

Mucosal barrier tissues and their mucosal associated lymphoid tissues (MALT) are attractive targets for vaccines and immunotherapies due to their roles in both priming and regulating adaptive immune responses. The upper and lower respiratory mucosae, in particular, possess unique properties: a vast surface area responsible for frontline protection against inhaled pathogens but also simultaneous tight regulation of homeostasis against a continuous backdrop of non-pathogenic antigen exposure. Within the upper and lower respiratory tract, the nasal and bronchial associated lymphoid tissues (NALT and BALT, respectively) are key sites where antigen-specific immune responses are orchestrated against inhaled antigens, serving as critical training grounds for adaptive immunity. Many infectious diseases are transmitted via respiratory mucosal sites, highlighting the need for vaccines that can activate resident frontline immune protection in these tissues to block infection. While traditional parenteral vaccines that are injected tend to elicit weak immunity in mucosal tissues, mucosal vaccines (i.e., that are administered intranasally) are capable of eliciting both systemic and mucosal immunity in tandem by initiating immune responses in the MALT. In contrast, administering antigen to mucosal tissues in the absence of adjuvant or costimulatory signals can instead induce antigen-specific tolerance by exploiting regulatory mechanisms inherent to MALT, holding potential for mucosal immunotherapies to treat autoimmunity. Yet despite being well motivated by mucosal biology, development of both mucosal subunit vaccines and immunotherapies has historically been plagued by poor drug delivery across mucosal barriers, resulting in weak efficacy, short-lived responses, and to-date a lack of clinical translation. Development of engineering strategies that can overcome barriers to mucosal delivery are thus critical for translation of mucosal subunit vaccines and immunotherapies. This review covers engineering strategies to enhance mucosal uptake via active targeting and passive transport mechanisms, with a parallel focus on mechanisms of immune activation and regulation in the respiratory mucosa. By combining engineering strategies for enhanced mucosal delivery with a better understanding of immune mechanisms in the NALT and BALT, we hope to illustrate the potential of these mucosal sites as targets for immunomodulation.

Role of T follicular helper cells in autoimmune rheumatic Diseases: A systematic review on immunopathogenesis and response to treatment

BACKGROUND

T follicular helper (Tfh) cells are a subdivision of T helper cells involved in antigen-specific B cell immunity. Tfh cells play an essential role in the interaction of T cells/B cells in the germinal centers (GC), and dysregulation of Tfh actions can offer pathogenic autoantibody formation and lead to the development of autoimmune diseases. This study seeks to evaluate changes in Tfh frequency and its related cytokines in autoimmune disease, its association with disease phase, severity, prognosis, and the effect of immunosuppressive treatment on the Tfh population.

METHOD

The study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 Statement. Electronic databases, including PubMed, Scopus, Web of Science, and Embase, were systematically searched for potentially eligible studies up to January 1, 2024.

RESULTS

We identified 4998 articles in the initial search, from which 1686 similar titles were removed. A total of 3312 articles were initially screened, and 3051 articles were excluded by title/abstract screening. A total of 261 studies were considered for full-text assessment, and 205 articles were excluded by reason. Finally, a total of 56 studies were included in our review.

CONCLUSION

The population of Tfh cells is generally higher in autoimmune diseases versus Health control. Moreover, the number of Tfh cells is associated with the disease severity and can be considered for determining the prognosis of studies. Also, peripheral blood circulating Tfh (cTfh) cells are an available sample that can be used as an indicator for diagnosing diseases.

Age-dependent decrease of circulating T follicular helper cells correlates with disease severity in elderly patients with COVID-19

Overwhelming evidence has shown that aging is a significant risk factor for COVID-19-related hospitalizations, death and other adverse health outcomes. Particular T cell subsets that susceptible to aging and associated with COVID-19 disease severity requires further elucidation. Our study recruited 57 elderly patients with acute COVID-19 and 27 convalescent donors. Adaptive immunity was assessed across the COVID-19 severity spectrum. Patients underwent age-dependent CD4+ T lymphopenia, preferential loss of circulating T follicular regulatory cells (cTfh) subsets including cTfh-em, cTfh-cm, cTfh1, cTfh2, cTfh17 and circulating T follicular regulatory cells (cTfr), which regulated antibody production through different pathways and correlated with COVID-19 severity, were observed. Moreover, vaccination improved cTfh-cm, cTfh2, cTfr proportion and promoted NAb production. In conclusion, the elderly had gone through age-dependent cTfh subsets deficiency, which impeded NAb production and enabled aggravation of COVID-19 to critical illness, whereas SARS-CoV-2 vaccine inoculation helped to rejuvenate cTfh, cTfr and intensify NAb responses.

Emerging Biochemical and Immunologic Mechanisms in the Pathogenesis of IgA Nephropathy

IgA nephropathy is a mesangioproliferative glomerular disease with significant morbidity and mortality. Most patients with IgA nephropathy develop kidney failure in their lifetime, reducing their life expectancy by a decade. Since its first description in 1968, it has been established that kidneys of IgA nephropathy patients are injured as "innocent bystanders" by nephritogenic IgA1-containing immune complexes. Results from clinical, biochemical, immunologic, and genetic studies suggest a multistep pathogenetic mechanism. In genetically predisposed individuals, this process results in formation of circulating immune complexes due to the binding of IgG/IgA autoantibodies to the polymeric IgA1 molecules with incomplete O-glycosylation. This event is followed by the addition of other proteins, such as complement C3, resulting in the formation of nephritogenic immune complexes. These complexes are not effectively removed from the circulation, and some of them pass through the fenestration of glomerular endothelial cells to enter the mesangial space and activate mesangial cells. It is thought that the process is initiated by soluble immune complexes and that their accumulation results in the formation of immunodeposits that further amplify glomerular injury. Here we summarize current understanding of the pathogenesis of IgA nephropathy and discuss experimental model systems that can inform development of new therapeutic strategies and targets.

BTB and CNC homology 1 deficiency disrupts intestinal IgA secretion through regulation of polymeric immunoglobulin receptor expression

Immunoglobulin A (IgA)-mediated mucosal immunity is important for the host because it contributes to reducing infection risk and to establishing host-microbe symbiosis. BTB and CNC homology 1 (Bach1) is a transcriptional repressor with physiological and pathophysiological functions that are of particular interest for their relation to gastrointestinal diseases. However, Bach1 effects on IgA-mediated mucosal immunity remain unknown. For this study using Bach1-deficient (Bach1-/-) mice, we investigated the function of Bach1 in IgA-mediated mucosal immunity. Intestinal mucosa, feces, and plasma IgA were examined using immunosorbent assay. After cell suspensions were prepared from Peyer's patches and colonic lamina propria, they were examined using flow cytometry. The expression level of polymeric immunoglobulin receptor (pIgR), which plays an important role in the transepithelial transport of IgA, was evaluated using Western blotting, quantitative real-time PCR, and immunohistochemistry. Although no changes in the proportions of IgA-producing cells were observed, the amounts of IgA in the intestinal mucosa were increased in Bach1-/- mice. Furthermore, plasma IgA was increased in Bach1-/- mice, but fecal IgA was decreased, indicating that Bach1-/- mice have abnormal secretion of IgA into the intestinal lumen. In fact, Bach1 deficiency reduced pIgR expression in colonic mucosa at both the protein and mRNA levels. In the human intestinal epithelial cell line LS174T, suppression of Bach1 reduced pIgR mRNA stability. In contrast, the overexpression of Bach1 increased pIgR mRNA stability. These results demonstrate that Bach1 deficiency causes abnormal secretion of IgA into the intestinal lumen via suppression of pIgR expression.NEW & NOTEWORTHY The transcriptional repressor Bach1 has been implicated in diverse intestinal functions, but the effects of Bach1 on IgA-mediated mucosal immunity remain unclear. We demonstrate here that Bach1 deficiency causes abnormal secretion of IgA into the intestinal lumen, although the proportions of IgA-producing cells were not altered. Furthermore, Bach1 regulates the expression of pIgR, which plays an important role in the transepithelial transport of IgA, at the posttranscriptional level.

Vaccines combining slow delivery and follicle targeting of antigens increase germinal center B cell clonal diversity and clonal expansion

Vaccines incorporating slow delivery, multivalent antigen display, or immunomodulation through adjuvants have an important role to play in shaping the humoral immune response. Here we analyzed mechanisms of action of a clinically relevant combination adjuvant strategy, where phosphoserine (pSer)-tagged immunogens bound to aluminum hydroxide (alum) adjuvant (promoting prolonged antigen delivery to draining lymph nodes) are combined with a potent saponin nanoparticle adjuvant termed SMNP (which alters lymph flow and antigen entry into lymph nodes). When employed with a stabilized HIV Env trimer antigen in mice, this combined adjuvant approach promoted substantial enhancements in germinal center (GC) and antibody responses relative to either adjuvant alone. Using scRNA-seq and scBCR-seq, we found that the alum-pSer/SMNP combination both increased the diversity of GC B cell clones and increased GC B cell clonal expansion, coincident with increases in the expression of Myc and the proportion of S-phase GC B cells. To gain insight into the source of these changes in the GC response, we analyzed antigen biodistribution and structural integrity in draining lymph nodes and found that the combination adjuvant approach, but not alum-pSer delivery or SMNP alone, promoted accumulation of highly intact antigen on follicular dendritic cells, reflecting an integration of the slow antigen delivery and altered lymph node uptake effects of these two adjuvants. These results demonstrate how adjuvants with complementary mechanisms of action impacting vaccine biodistribution and kinetics can synergize to enhance humoral immunity.

Germinal Center Response to mRNA Vaccination and Impact of Immunological Imprinting on Subsequent Vaccination

Vaccines are the most effective intervention currently available, offering protective immunity against targeted pathogens. The emergence of the coronavirus disease 2019 pandemic has prompted rapid development and deployment of lipid nanoparticle encapsulated, mRNA-based vaccines. While these vaccines have demonstrated remarkable immunogenicity, concerns persist regarding their ability to confer durable protective immunity to continuously evolving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. This review focuses on human B cell responses induced by SARS-CoV-2 mRNA vaccination, with particular emphasis on the crucial role of germinal center reactions in shaping enduring protective immunity. Additionally, we explored observations of immunological imprinting and dynamics of recalled pre-existing immunity following variants of concern-based booster vaccination. Insights from this review contribute to comprehensive understanding B cell responses to mRNA vaccination in humans, thereby refining vaccination strategies for optimal and sustained protection against evolving coronavirus variants.