The immune responses in CD40-deficient mice: impaired immunoglobulin class switching and germinal center formation

Molecular cloning of duck CD40 and its immune function research

Cosignal molecules are cell surface molecules that transduce signals to other cells to modulate immune response positively (costimulate) or negatively (cosuppress). Costimulatory signals are key factors in determining whether T/B cells are capable of responding to specific antigens and ultimately mediating an appropriate immune response. In this study, the cDNA sequence containing the complete coding frame of the costimulatory molecule duck CD40 gene was cloned and reported for the first time, and its mediated antiviral innate immune was verified in vitro. Results suggested duck CD40 molecule plays an important role in the innate immune responsiveness against some viruses. These data will be beneficial for the further understand of the avian immune system.

Glycolipid-peptide vaccination induces liver-resident memory CD8+ T cells that protect against rodent malaria

Liver resident-memory CD8⁺ T cells (T_RM cells) can kill liver-stage Plasmodium-infected cells and prevent malaria, but simple vaccines for generating this important immune population are lacking. Here, we report the development of a fully synthetic self-adjuvanting glycolipid-peptide conjugate vaccine designed to efficiently induce liver T_RM cells. Upon cleavage in vivo, the glycolipid-peptide conjugate vaccine releases an MHC I-restricted peptide epitope (to stimulate Plasmodium-specific CD8⁺ T cells) and an adjuvant component, the NKT cell agonist α-galactosylceramide (α-GalCer). A single dose of this vaccine in mice induced substantial numbers of intrahepatic malaria-specific CD8⁺ T cells expressing canonical markers of liver T_RM cells (CD69, CXCR6, and CD101), and these cells could be further increased in number upon vaccine boosting. We show that modifications to the peptide, such as addition of proteasomal-cleavage sequences or epitope-flanking sequences, or the use of alternative conjugation methods to link the peptide to the glycolipid improved liver T_RM cell generation and led to the development of a vaccine able to induce sterile protection in C57BL/6 mice against Plasmodium berghei sporozoite challenge after a single dose. Furthermore, this vaccine induced endogenous liver T_RM cells that were long-lived (half-life of ~425 days) and were able to maintain >90% sterile protection to day 200. Our findings describe an ideal synthetic vaccine platform for generating large numbers of liver T_RM cells for effective control of liver-stage malaria and, potentially, a variety of other hepatotropic infections.

Frontline Science: CD40 signaling restricts RNA virus replication in Mϕs, leading to rapid innate immune control of acute virus infection

Many acute viral infections target tissue Mϕs, yet the mechanisms of Mϕ-mediated control of viruses are poorly understood. Here, we report that CD40 expressed by peritoneal Mϕs restricts early infection of a broad range of RNA viruses. Loss of CD40 expression enhanced virus replication as early as 12-24 h of infection and, conversely, stimulation of CD40 signaling with an agonistic Ab blocked infection. With peritoneal cell populations infected with the filovirus, wild-type (WT) Ebola virus (EBOV), or a BSL2 model virus, recombinant vesicular stomatitis virus encoding Ebola virus glycoprotein (rVSV/EBOV GP), we examined the mechanism conferring protection. Here, we demonstrate that restricted virus replication in Mϕs required CD154/CD40 interactions that stimulated IL-12 production through TRAF6-dependent signaling. In turn, IL-12 production resulted in IFN-γ production, which induced proinflammatory polarization of Mϕs, protecting the cells from infection. These CD40-dependent events protected mice against virus challenge. CD40-/- mice were exquisitely sensitive to intraperitoneal challenge with a dose of rVSV/EBOV GP that was sublethal to CD40+/+ mice, exhibiting viremia within 12 h of infection and rapidly succumbing to infection. This study identifies a previously unappreciated role for Mϕ-intrinsic CD40 signaling in controlling acute virus infection.

Functional Role of B Cells in Atherosclerosis

Atherosclerosis is a lipid-driven inflammatory disease of blood vessels, and both innate and adaptive immune responses are involved in its development. The impact of B cells on atherosclerosis has been demonstrated in numerous studies and B cells have been found in close proximity to atherosclerotic plaques in humans and mice. B cells exert both atheroprotective and pro-atherogenic functions, which have been associated with their B cell subset attribution. While B1 cells and marginal zone B cells are considered to protect against atherosclerosis, follicular B cells and innate response activator B cells have been shown to promote atherosclerosis. In this review, we shed light on the role of B cells from a different, functional perspective and focus on the three major B cell functions: antibody production, antigen presentation/T cell interaction, and the release of cytokines. All of these functions have the potential to affect atherosclerosis by multiple ways and are dependent on the cellular milieu and the activation status of the B cell. Moreover, we discuss B cell receptor signaling and the mechanism of B cell activation under atherosclerosis-prone conditions. By summarizing current knowledge of B cells in and beyond atherosclerosis, we are pointing out open questions and enabling new perspectives.

An Overview of Advances in Cell-Based Cancer Immunotherapies Based on the Multiple Immune-Cancer Cell Interactions

Tumors have a complex ecosystem in which behavior and fate are determined by the interaction of diverse cancerous and noncancerous cells at local and systemic levels. A number of studies indicate that various immune cells participate in tumor development (Fig. 1). In this review, we will discuss interactions among T lymphocytes (T cells), B cells, natural killer (NK) cells, dendritic cells (DCs), tumor-associated macrophages (TAMs), neutrophils, and myeloid-derived suppressor cells (MDSCs). In addition, we will touch upon attempts to either use or block subsets of immune cells to target cancer.

Comprehensive analysis of immune infiltration and gene expression for predicting survival in patients with sarcomas

Tumor microenvironments are strongly related to tumor development, and immune-infiltrating cells and immune-related molecules are potential prognostic markers. However, the shortcomings of traditional measurement methods limit the accurate evaluation of various components in tumor microenvironments. With the rapid advancement of Next-Generation RNA Sequencing technology, dedicated and in-depth analyses of immune filtration within the tumor microenvironment has been achieved. In this study, we combined the bioinformatics analysis methods ESTIMATE, CIBERSORT, and ssGSEA to characterize the immune infiltration of sarcomas and to identify specific immunomodulators of different pathological subtypes. We further extracted a functional enrichment of significant immune-related genes related to improved prognosis, including NR1H3, VAMP5, GIMAP2, GBP2, HLA-E and CRIP1. Overall, the immune microenvironment is an important prognostic determinant of sarcomas and may be a potential resource for developing effective immunotherapy.

Skin-Associated B Cells in the Pathogenesis of Cutaneous Autoimmune Diseases-Implications for Therapeutic Approaches

B lymphocytes are crucial mediators of systemic immune responses and are known to be substantial in the pathogenesis of autoimmune diseases with cutaneous manifestations. Amongst them are lupus erythematosus, dermatomyositis, systemic sclerosis and psoriasis, and particularly those driven by autoantibodies such as pemphigus and pemphigoid. However, the concept of autoreactive skin-associated B cells, which may reside in the skin and locally contribute to chronic inflammation, is gradually evolving. These cells are believed to differ from B cells of primary and secondary lymphoid organs and may provide additional features besides autoantibody production, including cytokine expression and crosstalk to autoreactive T cells in an antigen-presenting manner. In chronically inflamed skin, B cells may appear in tertiary lymphoid structures. Those abnormal lymph node-like structures comprise a network of immune and stromal cells possibly enriched by vascular structures and thus constitute an ideal niche for local autoimmune responses. In this review, we describe current considerations of different B cell subsets and their assumed role in skin autoimmunity. Moreover, we discuss traditional and B cell-associated approaches for the treatment of autoimmune skin diseases, including drugs targeting B cells (e.g., CD19- and CD20-antibodies), plasma cells (e.g., proteasome inhibitors, CXCR4 antagonists), activated pathways (such as BTK- and PI3K-inhibitors) and associated activator molecules (BLyS, APRIL).

CD40/CD40L and Related Signaling Pathways in Cardiovascular Health and Disease-The Pros and Cons for Cardioprotection

The CD40-CD40 ligand (CD40L) dyad represents a scientific and clinical field that has raised many controversies in the past and cannot be clearly defined as being an either beneficial or harmful pathway. Being crucially involved in physiological immunological processes as well as pathological inflammatory reactions, the signaling pathway has been recognized as a key player in the development of both autoimmune and cardiovascular disease. Even though the possibilities of a therapeutic approach to the dyad were recognized decades ago, due to unfortunate events, detailed in this review, pharmacological treatment targeting the dyad, especially in patients suffering from atherosclerosis, is not available. Despite the recent advances in the treatment of classical cardiovascular risk factors, such as arterial hypertension and diabetes mellitus, the treatment of the associated low-grade inflammation that accounts for the progression of atherosclerosis is still challenging. Low-grade inflammation can be detected in a significant portion of patients that suffer from cardiovascular disease and it is therefore imperative to develop new therapeutic strategies in order to combat this driver of atherosclerosis. Of note, established cardiovascular drugs such as angiotensin-converting enzyme inhibitors or statins have proven beneficial cardiovascular effects that are also related to their pleiotropic immunomodulatory properties. In this review, we will discuss the setbacks encountered as well as new avenues discovered on the path to a different, inflammation-centered approach for the treatment of cardiovascular disease with the CD40-CD40L axis as a central therapeutic target.

Follicular Dendritic Cells Modulate Germinal Center B Cell Diversity through FcγRIIB

Follicular dendritic cells (FDCs), a rare and enigmatic stromal cell type in the B cell follicles of secondary lymphoid organs, store and present antigen to B cells. While essential for germinal center (GC) responses, their exact role during GC B cell selection remains unknown. FDCs upregulate the inhibitory IgG Fc receptor FcγRIIB during GC formation. We show that the stromal deficiency of FcγRIIB does not affect GC B cell frequencies compared to wild-type mice. However, in the absence of FcγRIIB on FDCs, GCs show aberrant B cell selection during autoreactive and selective foreign antigen responses. These GCs are more diverse as measured by the AidCre^ERT2 -confetti system and show the persistence of IgM⁺ clones with decreased numbers of IgH mutations. Our results show that FDCs can modulate GC B cell diversity by the upregulation of FcγRIIB. Permissive clonal selection and subsequent increased GC diversity may affect epitope spreading during autoimmunity and foreign responses.

van der Poel et al. show that follicular dendritic cells (FDCs) can regulate germinal center diversity through FcγRIIB. In the absence of this receptor, germinal centers appear more diverse. In addition, the loss of FcγRIIB on FDCs leads to the persistence of IgM clones with decreased levels of somatic hypermutation.

Mutual inhibition between Prkd2 and Bcl6 controls T follicular helper cell differentiation

T follicular helper cells (T_FH) participate in germinal center (GC) development and are necessary for B cell production of high-affinity, isotype-switched antibodies. In a forward genetic screen, we identified a missense mutation in Prkd2, encoding the serine/threonine kinase protein kinase D2, which caused elevated titers of immunoglobulin E (IgE) in the serum. Subsequent analysis of serum antibodies in mice with a targeted null mutation of Prkd2 demonstrated polyclonal hypergammaglobulinemia of IgE, IgG1, and IgA isotypes, which was exacerbated by the T cell-dependent humoral response to immunization. GC formation and GC B cells were increased in Prkd2^-/- spleens. These effects were the result of excessive cell-autonomous T_FH development caused by unrestricted Bcl6 nuclear translocation in Prkd2^-/- CD4⁺ T cells. Prkd2 directly binds to Bcl6, and Prkd2-dependent phosphorylation of Bcl6 is necessary to constrain Bcl6 to the cytoplasm, thereby limiting T_FH development. In response to immunization, Bcl6 repressed Prkd2 expression in CD4⁺ T cells, thereby committing them to T_FH development. Thus, Prkd2 and Bcl6 form a mutually inhibitory positive feedback loop that controls the stable transition from naïve CD4⁺ T cells to T_FH during the adaptive immune response.

Targeting co-stimulatory molecules in autoimmune disease

Therapeutic targeting of immune checkpoints has garnered significant attention in the area of cancer immunotherapy, in which efforts have focused in particular on cytotoxic T lymphocyte antigen 4 (CTLA4) and PD1, both of which are members of the CD28 family. In autoimmunity, these same pathways can be targeted to opposite effect: to curb the over-exuberant immune response. The CTLA4 checkpoint serves as an exemplar, whereby CTLA4 activity is blocked by antibodies in cancer immunotherapy and augmented by the provision of soluble CTLA4 in autoimmunity. Here, we review the targeting of co-stimulatory molecules in autoimmune diseases, focusing in particular on agents directed at members of the CD28 or tumour necrosis factor receptor families. We present the state of the art in co-stimulatory blockade approaches, including rational combinations of immune inhibitory agents, and discuss the future opportunities and challenges in this field.

PI3Kδ inhibition reshapes follicular lymphoma-immune microenvironment cross talk and unleashes the activity of venetoclax

Despite idelalisib approval in relapsed follicular lymphoma (FL), a complete characterization of the immunomodulatory consequences of phosphatidylinositol 3-kinase δ (PI3Kδ) inhibition, biomarkers of response, and potential combinatorial therapies in FL remain to be established. Using ex vivo cocultures of FL patient biopsies and follicular dendritic cells (FDCs) to mimic the germinal center (n = 42), we uncovered that PI3Kδ inhibition interferes with FDC-induced genes related to angiogenesis, extracellular matrix formation, and transendothelial migration in a subset of FL samples, defining an 18-gene signature fingerprint of idelalisib sensitivity. A common hallmark of idelalisib found in all FL cases was its interference with the CD40/CD40L pathway and induced proliferation, together with the downregulation of proteins crucial for B-T-cell synapses, leading to an inefficient cross talk between FL cells and the supportive T-follicular helper cells (TFH). Moreover, idelalisib downmodulates the chemokine CCL22, hampering the recruitment of TFH and immunosupressive T-regulatory cells to the FL niche, leading to a less supportive and tolerogenic immune microenvironment. Finally, using BH3 profiling, we uncovered that FL-FDC and FL-macrophage cocultures augment tumor addiction to BCL-XL and MCL-1 or BFL-1, respectively, limiting the cytotoxic activity of the BCL-2 inhibitor venetoclax. Idelalisib restored FL dependence on BCL-2 and venetoclax activity. In summary, idelalisib exhibits a patient-dependent activity toward angiogenesis and lymphoma dissemination. In all FL cases, idelalisib exerts a general reshaping of the FL immune microenvironment and restores dependence on BCL-2, predisposing FL to cell death, providing a mechanistic rationale for investigating the combination of PI3Kδ inhibitors and venetoclax in clinical trials.

Fibroblasts as a source of self-antigens for central immune tolerance

Fibroblasts are one of the most common but also neglected types of stromal cells, the heterogeneity of which underlies the specific function of tissue microenvironments in development and regeneration. In the thymus, autoreactive T cells are thought to be negatively selected by reference to the self-antigens expressed in medullary epithelial cells, but the contribution of other stromal cells to tolerance induction has been poorly examined. In the present study, we report a PDGFR⁺ gp38⁺ DPP4^- thymic fibroblast subset that is required for T cell tolerance induction. The deletion of the lymphotoxin β-receptor in thymic fibroblasts caused an autoimmune phenotype with decreased expression of tissue-restricted and fibroblast-specific antigens, offering insight into the long-sought target of lymphotoxin signaling in the context of the regulation of autoimmunity. Thus, thymic medullary fibroblasts play an essential role in the establishment of central tolerance by producing a diverse array of self-antigens.

CD40 and CD72 expression and prognostic values among children with systemic lupus erythematosus: a case-control study

Systemic lupus erythematosus (SLE) is a chronic disease with proven interactions between immune system components, including both humoral- and cell-mediated immunity, as well as co-stimulatory and inhibitory molecules such as CD40 and CD72. Here, we investigated CD40 and CD72 expression on B cells of SLE children and assessed their prognostic values. We conducted a preliminary case-control study in Mansoura University Children's Hospital, Egypt from September 2018 to January 2020 including 27 SLE children and 27 healthy controls. We assessed cases during initial flare and after remission. Flow cytometry analysis was carried out for all participants for CD40 and CD72 expression of B cells. During flare, SLE cases had statistically significant higher CD40 and lower CD72 expression in comparison with controls (p < 0.001). After remission, the number of CD40⁺ B cells significantly decreased (p < 0.001), while the number of CD72⁺ B cells significantly increased (p < 0.001) in comparison with flare. We reported non-significant positive correlations between CD40 expression and SLE Disease Activity Index (SLEDAI; p = 0.347 during flare and p = 0.653 after remission) and negative correlations between CD72 expression and SLEDAI (p = 0.34 during flare and p = 0.044 after remission). No significant differences were detected between renal histopathology classes with regard to CDs expression on B cells (p = 0.45 for CD40 and p = 0.63 for CD72). In conclusion, CD40⁺ B cells and CD72⁺ B cells could be considered as markers of paediatric SLE flare and remission, respectively.

Advanced Foot-And-Mouth Disease Vaccine Platform for Stimulation of Simultaneous Cellular and Humoral Immune Responses

Currently available commercial foot-and-mouth disease (FMD) vaccines have various limitations, such as the slow induction and short-term maintenance of antibody titers. Therefore, a novel FMD vaccine that can rapidly induce high neutralizing antibody titers to protect the host in early stages of an FMD virus infection, maintain high antibody titers for long periods after one vaccination dose, and confer full protection against clinical symptoms by simultaneously stimulating cellular and humoral immunity is needed. Here, we developed immunopotent FMD vaccine strains A-3A and A-HSP70, which elicit strong initial cellular immune response and induce humoral immune response, including long-lasting memory response. We purified the antigen (inactivated virus) derived from these immunopotent vaccine strains, and evaluated the immunogenicity and efficacy of the vaccines containing these antigens in mice and pigs. The immunopotent vaccine strains A-3A and A-HSP70 demonstrated superior immunogenicity compared with the A strain (backbone strain) in mice. The oil emulsion-free vaccine containing A-3A and A-HSP70 antigens effectively induced early, mid-term, and long-term immunity in mice and pigs by eliciting robust cellular and humoral immune responses through the activation of co-stimulatory molecules and the secretion of proinflammatory cytokines. We successfully derived an innovative FMD vaccine formulation to create more effective FMD vaccines.

A CD40L-targeting protein reduces autoantibodies and improves disease activity in patients with autoimmunity

The CD40/CD40L axis plays a central role in the generation of humoral immune responses and is an attractive target for treating autoimmune diseases in the clinic. Here, we report the generation and clinical results of a CD40L binding protein, VIB4920, which lacks an Fc domain, therefore avoiding platelet-related safety issues observed with earlier monoclonal antibody therapeutics that targeted CD40L. VIB4920 blocked downstream CD40 signaling events, resulting in inhibition of human B cell activation and plasma cell differentiation, and did not induce platelet aggregation in preclinical studies. In a phase 1 study in healthy volunteers, VIB4920 suppressed antigen-specific IgG in a dose-dependent fashion after priming and boosting with the T-dependent antigen, KLH. Furthermore, VIB4920 significantly reduced circulating Ki67⁺ dividing B cells, class-switched memory B cells, and a plasma cell gene signature after immunization. In a phase 1b proof-of-concept study in patients with rheumatoid arthritis, VIB4920 significantly decreased disease activity, achieving low disease activity or clinical remission in more than 50% of patients in the two higher-dose groups. Dose-dependent decreases in rheumatoid factor autoantibodies and Vectra DA biomarker score provide additional evidence that VIB4920 effectively blocked the CD40/CD40L pathway. VIB4920 demonstrated a good overall safety profile in both clinical studies. Together, these data demonstrate the potential of VIB4920 to significantly affect autoimmune disease and humoral immune activation and to support further evaluation of this molecule in inflammatory conditions.

Dysregulation of humoral immunity in chronic infection

Chronic viral infections disrupt the ability of the humoral immune response to produce neutralizing antibody or form effective immune memory, preventing viral clearance and making vaccine design difficult. Multiple components of the B-cell response are affected by pathogens that are not cleared from the host. Changes in the microenvironment shift production of B cells to short-lived plasma cells early in the response. Polyclonal B cells are recruited into both the plasma cell and germinal center compartments, inhibiting the formation of a targeted, high-affinity response. Finally, memory B cells shift toward an "atypical" phenotype, which may in turn result in changes to the functional properties of this population. While similar properties of B-cell dysregulation have been described across different types of persistent infections, key questions about the underlying mechanisms remain. This review will discuss the recent advances in this field, as well as highlight the critical questions about the interplay between viral load, microenvironment, the polyclonal response and atypical memory B cells that are yet to be answered. Design of new preventative treatments will rely on identifying the extrinsic and intrinsic modulators that push B cells toward an ineffective response, and thus identify new ways to guide them back onto the best path for clearance of virus and formation of effective immune memory.

Rationale for CD40 pathway blockade in autoimmune rheumatic disorders

CD40 and its ligand CD40L (CD154) belong to the tumor necrosis factor receptor superfamily and are expressed by a variety of immune and non-immune cells. CD40L plays a central role in co-stimulation and regulation of the immune response via activation of cells expressing CD40. Imbalance of the CD40-CD40L co-stimulatory pathway has been reported in many autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, and Sjögren's syndrome, thus supporting its role in the breach of immune tolerance that is typical of these diseases. Targeting CD40-CD40L signalling might represent a novel therapeutic option for several autoimmune disorders.

Membrane IgM+ plasma cells in grass carp (Ctenopharyngodon idella): Insights into the conserved evolution of IgM+ plasma cells in vertebrates

Teleost fish are the most primitive bony vertebrates that contain B cells; thus, comparative analysis of teleost naïve/mature B cells and plasma cells can provide helpful evidence for understanding the evolution paradigms of these two B-cell subpopulations in vertebrates. In this study, we developed monoclonal antibody against grass carp IgM and identified two different IgM⁺ cell subsets: IgM⁺ lymphocytes (Lym), resembling naïve/mature B cells, and IgM⁺ myeloid cells (Mye), resembling plasma cells. Like plasma cells in mammals, the size of IgM⁺ Mye is significantly larger than that of IgM⁺ Lym, as revealed by flow cytometric analysis and transmission electron microscopy. The IgM⁺ Mye were further verified as plasma cells because they showed gene expression patterns similar with those of human plasma cells and a great capacity to secrete IgM. Like mammalian IgM⁺ and IgA⁺ plasma cells, not IgG⁺ plasma cells, grass carp IgM⁺ Mye also expressed membrane immunoglobulins, a feature conserved in IgM⁺ plasma cells in vertebrates. Furthermore, recombinant CD40L or IL-21 alone could induce the plasma cell generation and IgM secretion, while the combination of CD40L and IL-21 had greater effect on IgM secretion, but not on plasma cell generation. This study fills an important gap in the knowledge of plasma cells in teleost fish and provides critical insights into the conserved evolution of IgM⁺ plasma cells in vertebrates.

Sufficiency of CD40 activation and immune checkpoint blockade for T cell priming and tumor immunity

Innate immune receptors such as toll-like receptors (TLRs) provide critical molecular links between innate cells and adaptive immune responses. Here, we studied the CD40 pathway as an alternative bridge between dendritic cells (DCs) and adaptive immunity in cancer. Using an experimental design free of chemo- or radiotherapy, we found CD40 activation with agonistic antibodies (⍺CD40) produced complete tumor regressions in a therapy-resistant pancreas cancer model, but only when combined with immune checkpoint blockade (ICB). This effect, unachievable with ICB alone, was independent of TLR, STING, or IFNAR pathways. Mechanistically, αCD40/ICB primed durable T cell responses, and efficacy required DCs and host expression of CD40. Moreover, ICB drove optimal generation of polyfunctional T cells in this "cold" tumor model, instead of rescuing T cell exhaustion. Thus, immunostimulation via αCD40 is sufficient to synergize with ICB for priming. Clinically, combination αCD40/ICB may extend efficacy in patients with "cold" and checkpoint-refractory tumors.

Assessment of the anti-CD40 antibody iscalimab in patients with primary Sjögren's syndrome: a multicentre, randomised, double-blind, placebo-controlled, proof-of-concept study

BACKGROUND

Primary Sjögren's syndrome is an autoimmune disease that presents as dryness of the mouth and eyes due to impairment of the exocrine glands. To our knowledge, no systemic therapies for primary Sjögren's syndrome have shown efficacy. CD40-CD154-mediated T cell-B cell interactions in primary Sjögren's syndrome contribute to aberrant lymphocyte activation in inflamed tissue, leading to sialadenitis and other tissue injury. Therefore, we investigated the safety and preliminary efficacy of iscalimab (CFZ533), a novel anti-CD40 monoclonal antibody, in patients with primary Sjögren's syndrome.

METHODS

This multicentre, randomised, double-blind, placebo-controlled, proof-of-concept study took place at ten investigational sites across Europe (UK, n=4; Germany, Switzerland, and Hungary, n=1 each) and the USA (n=3). Eligible patients were aged 18-75 years and fulfilled the 2002 American European consensus group diagnostic classification criteria for primary Sjögren's syndrome. In the double-blind phase of the trial, patients were randomly assigned (2:1) via computer-generated unique randomisation numbers to receive subcutaneous iscalimab (3 mg/kg) or placebo at weeks 0, 2, 4, and 8 (cohort 1) or intravenous iscalimab (10 mg/kg) or placebo at weeks 0, 2, 4, and 8 (cohort 2). Randomisation was stratified according to baseline intake of oral corticosteroids. At week 12, patients in both cohorts received open-label iscalimab (same dose and route) for 12 weeks. The primary objectives of the study were to assess the safety, tolerability, and efficacy of multiple doses of iscalimab in the two sequential dose cohorts. Safety and tolerability were assessed by adverse events and efficacy of iscalimab versus placebo was assessed by clinical disease activity, as measured by the change in European League Against Rheumatism Sjögren's syndrome disease activity index (ESSDAI) score after 12 weeks of treatment. Analyses were done on a per-protocol basis. The trial was registered with ClinicalTrials.gov, NCT02291029.

FINDINGS

Between Oct 22, 2014, and June 28, 2016, we assessed 82 patients for eligibility (25 for cohort 1 and 57 for cohort 2). 38 patients were excluded because of ineligibility. In cohort 1, 12 patients were randomly assigned to receive either 3 mg/kg doses of iscalimab (n=8) or placebo (n=4), and in cohort 2, 32 patients were randomly assigned to receive either intravenous 10 mg/kg doses of iscalimab (n=21) or placebo (n=11). Adverse events were similar between iscalimab treatment groups and placebo groups, with adverse events occurring in all patients in cohort 1, and in 52% and 64% of the iscalimab and placebo groups, respectively, in cohort 2. Two serious adverse events were reported (one case of bacterial conjunctivitis in cohort 1 and one case of atrial fibrillation in cohort 2), which were unrelated to treatment with iscalimab. Intravenous treatment with iscalimab resulted in a mean reduction of 5·21 points (95% CI 0·96-9·46; one-sided p=0·0090) in ESSDAI score compared with placebo. There was no signficiant difference in ESSDAI score between subcutaneous iscalimab and placebo.

INTERPRETATION

To our knowledge, this is the first randomised, placebo-controlled proof-of-concept study of a new investigational drug for primary Sjögren's syndrome that indicates preliminary efficacy. Our data suggest a role of CD40-CD154 interactions in primary Sjögren's syndrome pathology and the therapeutic potential for CD40 blockade in this disease should be investigated further.

FUNDING

Novartis Pharma.

Expression of CD40L by the ALVAC-Simian Immunodeficiency Virus Vector Abrogates T Cell Responses in Macaques

Immunization with recombinant ALVAC/gp120 alum vaccine provided modest protection from human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) acquisition in humans and macaques. Vaccine-mediated protection was associated with the elicitation of IgG against the envelope V2 loop and of envelope-specific CD4⁺ T cell responses. We hypothesized that the simultaneous expression of the costimulatory molecule CD40L (CD154) by the ALVAC-HIV vector could increase both protective humoral and cellular responses. We engineered an ALVAC-SIV coexpressing CD40L with SIV_mac251 (ALVAC-SIV/CD40L) gag, pol, and env genes. We compared its immunogenicity in macaques with that of a canonical ALVAC-SIV, with both given as a vector-prime/gp120 in alum boost strategy. The ALVAC-SIV/CD40L was superior to the ALVAC-SIV regimen in inducing binding and tier 1 neutralizing antibodies against the gp120. The increase in humoral responses was associated with the expression of the membrane-bound form of the CD40L by CD4⁺ T cells in lymph nodes. Unexpectedly, the ALVAC-SIV/CD40L vector had a blunting effect on CD4⁺ Th1 helper responses and instead favored the induction of myeloid-derived suppressor cells, the immune-suppressive interleukin-10 (IL-10) cytokine, and the down-modulatory tryptophan catabolism. Ultimately, this strategy failed to protect macaques from SIV acquisition. Taken together, these results underlie the importance of balanced vaccine-induced activating versus suppressive immune responses in affording protection from HIV.IMPORTANCE CD40-CD40 ligand (CD40L) interaction is crucial for inducing effective cytotoxic and humoral responses against pathogens. Because of its immunomodulatory function, CD40L has been used to enhance immune responses to vaccines, including candidate vaccines for HIV. The only successful vaccine ever tested in humans utilized a strategy combining canarypox virus-based vector (ALVAC) together with an envelope protein (gp120) adjuvanted in alum. This strategy showed limited efficacy in preventing HIV-1/SIV acquisition in humans and macaques. In both species, protection was associated with vaccine-induced antibodies against the HIV envelope and CD4⁺ T cell responses, including type 1 antiviral responses. In this study, we tested whether augmenting CD40L expression by coexpressing it with the ALVAC vector could increase the protective immune responses. Although coexpression of CD40L did increase humoral responses, it blunted type 1 CD4⁺ T cell responses against the SIV envelope protein and failed to protect macaques from viral infection.

Longitudinal relationships between rheumatoid factor and cytokine expression by immunostimulated peripheral blood lymphocytes from patients with rheumatoid arthritis: New insights into B-cell activation

To identify associations between immunostimulated cytokine production and disease characteristics, peripheral blood lymphocytes were collected from 155 adult patients with rheumatoid arthritis (RA) before and after a 5-year interval. The lymphocytes were activated in vitro with T-cell stimulants, cytosine-phosphate-guanine (CpG) oligonucleotide, and medium alone (negative control). Expression of 17 cytokines was evaluated with immunoassays, and factor analysis was used to reduce data complexity and identify cytokine combinations indicative of cell types preferentially activated by each immunostimulant. The findings showed that the highest numbers of correlations were between cytokine levels and rheumatoid factor (RF) positivity and between cytokine levels and disease duration. Scores for cytokines driven by CpG and medium alone were negatively associated with RF positivity and disease duration at baseline but positively associated with both at 5 years. Our findings suggest that RF expression sustained over time increases activation of B cells and monocytes without requirements for T-cell functions.

First-in-human clinical trial to assess pharmacokinetics, pharmacodynamics, safety, and tolerability of iscalimab, an anti-CD40 monoclonal antibody

Iscalimab is a fully human, CD40 pathway blocking, nondepleting monoclonal antibody being developed as an immunosuppressive agent. We describe a first-in-human, randomized, double-blind, placebo-controlled study investigating the safety, tolerability, pharmacokinetics, and pharmacodynamics of iscalimab in healthy subjects and rheumatoid arthritis patients. Healthy subjects (n = 56) received single doses of intravenous iscalimab (0.03, 0.1, 0.3, 1, or 3 mg/kg), or subcutaneous iscalimab (3 mg/kg), or placebo. Rheumatoid arthritis patients (n = 20) received single doses of intravenous iscalimab (10 or 30 mg/kg) or placebo. Iscalimab exhibited target-mediated drug disposition resulting in dose-dependent and nonlinear pharmacokinetics. Complete (≥90%) CD40 receptor occupancy on whole blood B cells was observed at plasma concentrations >0.3-0.4 µg/mL. In subjects receiving 3 mg/kg iscalimab, antibody responses to keyhole limpet hemocyanin were transiently suppressed. CD40 occupancy by iscalimab prevented ex vivo human rCD154-induced expression of CD69 on B cells in whole blood. All doses were generally safe and well tolerated, with no clinically relevant changes in any safety parameters, including no evidence of thromboembolic events. Iscalimab appears to be a promising blocker of the CD40-CD154 costimulatory pathway with potential use in transplantation and other autoimmune diseases.

Impact of CD40 gene polymorphisms on the risk of immune thrombocytopenic purpura

OBJECTIVES

To evaluate the relationship between two common single nucleotide polymorphisms (SNPs) of CD40 gene (rs1883832 C/T and rs4810485 G/T) and the risk of immune thrombocytopenia (ITP) in the Egyptian population.

METHODS

A case-control study was conducted retrospectively on 101 cases with ITP and 97 healthy subjects. Two SNPs of CD40 gene (rs1883832 C/T and rs4810485 G/T) were genotyped via Taqman allele discrimination real-time PCR. The frequencies of different genetic models of both SNPs were calculated and compared between ITP cases and controls. Linkage analysis was performed between the studied SNPs. Odds ratio (OR) and 95% confidence interval (CI) were assessed using multinomial logistic regression analysis to determine the association of CD40 gene SNPs genotypes, alleles, and haplotypes with the risk of ITP. The odds ratio was further adjusted to the confounders for risk stratification.

RESULTS

CD40 (rs1883832) TT genotype carriers have a significantly higher risk of ITP when compared to CC genotype carriers (adjusted OR: 3.792, 95%CI: 1.252-11.49, P = 0.018). T allele also represents 1.711-fold increased risk of ITP which is more evident in males (P = 0.016). No significant difference was observed in the frequency of CD40 (rs4810485 G/T) genetic models between cases and controls. Linkage disequilibrium was found between the two SNPs and revealed four main haplotypes (C-G; C-T; T-G; T-T) with a significantly higher frequency of T-G haplotype in ITP cases than in healthy controls which confers an increased risk of ITP development (OR: 2.349, 95%CI: 1.271-4.339, P = 0.006).

CONCLUSIONS

CD40 gene SNP rs1883832 is associated with an increased risk of ITP development in the Egyptian population, while the SNP rs4810485 has no association. Moreover, T-G haplotype is a risk genetic model for ITP.

B Cell and CD4 T Cell Interactions Promote Development of Atherosclerosis

Interaction between B and CD4 T cells is crucial for their optimal responses in adaptive immunity. Immune responses augmented by their partnership promote chronic inflammation. Here we report that interaction between B and CD4 T cells augments their atherogenicity to promote lipid-induced atherosclerosis. Genetic deletion of the gene encoding immunoglobulin mu (μ) heavy chain (μMT) in ApoE^−/− mice resulted in global loss of B cells including those in atherosclerotic plaques, undetectable immunoglobulins and impaired germinal center formation. Despite unaffected numbers in the circulation and peripheral lymph nodes, CD4 T cells were also reduced in spleens as were activated and memory CD4 T cells. In hyperlipidemic μMT^−/− ApoE^−/− mice, B cell deficiency decreased atherosclerotic lesions, accompanied by absence of immunoglobulins and reduced CD4 T cell accumulation in lesions. Adoptive transfer of B cells deficient in either MHCII or co-stimulatory molecule CD40, molecules required for B and CD4 T cell interaction, into B cell-deficient μMT^−/− ApoE^−/− mice failed to increase atherosclerosis. In contrast, wildtype B cells transferred into μMT^−/− ApoE^−/− mice increased atherosclerosis and increased CD4 T cells in lesions including activated and memory CD4 T cells. Transferred B cells also increased their expression of atherogenic cytokines IL-1β, TGF-β, MCP-1, M-CSF, and MIF, with partial restoration of germinal centers and plasma immunoglobulins. Our study demonstrates that interaction between B and CD4 T cells utilizing MHCII and CD40 is essential to augment their function to increase atherosclerosis in hyperlipidemic mice. These findings suggest that targeting B cell and CD4 T cell interaction may be a therapeutic strategy to limit atherosclerosis progression.

T cell interactions with B cells during germinal center formation, a three-step model

Establishment of effective immunity against invading microbes depends on continuous generation of antibodies that facilitate pathogen clearance. Long-lived plasma cells with the capacity to produce high affinity antibodies evolve in germinal centers (GCs), where B cells undergo somatic hypermutation and are subjected to affinity-based selection. Here, we focus on the cellular interactions that take place early in the antibody immune response during GC colonization. Clones bearing B-cell receptors with different affinities and specificities compete for entry to the GC, at the boundary between the B-cell and T-cell zones in lymphoid organs. During this process, B cells compete for interactions with T follicular helper cells, which provide selection signals required for differentiation into GC cells and antibody secreting cells. These cellular engagements are long-lasting and depend on activation of adhesion molecules that support persistent interactions and promote transmission of signals between the cells. Here, we discuss how interactions between cognate T and B cells are primarily maintained by three types of molecular interactions: homophilic signaling lymphocytic activation molecule (SLAM) interactions, T-cell receptor: peptide-loaded major histocompatibility class II (pMHCII), and LFA-1:ICAMs. These essential components support a three-step process that controls clonal selection for entry into the antibody affinity maturation response in the GC, and establishment of long-lasting antibody-mediated immunity.

Activation-induced surface proteins in the identification of antigen-responsive CD4 T cells

Identification of antigen specificity of CD4 T cells is instrumental in understanding adaptive immune responses in health and disease. The high diversity of CD4 T cell repertoire combined with the functional heterogeneity of the compartment poses a challenge to the assessment of CD4 T cell responses. In spite of that, multiple technologies allow direct or indirect interrogation of antigen specificity of CD4 T cells. In the last decade, multiple surface proteins have been established as cytokine-independent surrogates of in vitro CD4 T cell activation, and have found applications in the live identification and isolation of antigen-responsive CD4 T cells. Here we review the current knowledge of the surface proteins that permit identification of viable antigen-responsive CD4 T cells with high specificity, including those capable of identifying specialized CD4 T subsets such as germinal center follicular helper T cells and CD4 regulatory T cells.

The AKT isoforms 1 and 2 drive B cell fate decisions during the germinal center response

The PI3K pathway is integral for the germinal center (GC) response. However, the contribution of protein kinase B (AKT) as a PI3K effector in GC B cells remains unknown. Here, we show that mice lacking the AKT1 and AKT2 isoforms in B cells failed to form GCs, which undermined affinity maturation and antibody production in response to immunization. Upon B-cell receptor stimulation, AKT1/2-deficient B cells showed poor survival, reduced proliferation, and impaired mitochondrial and metabolic fitness, which collectively halted GC development. By comparison, Foxo1 T24A mutant, which cannot be inactivated by AKT1/2 phosphorylation and is sequestered in the nucleus, significantly enhanced antibody class switch recombination via induction of activation-induced cytidine deaminase (AID) expression. By contrast, repression of FOXO1 activity by AKT1/2 promoted IRF4-driven plasma cell differentiation. Last, we show that T-cell help via CD40, but not enforced expression of Bcl2, rescued the defective GC response in AKT1/2-deficient animals by restoring proliferative expansion and energy production. Overall, our study provides mechanistic insights into the key role of AKT and downstream pathways on B cell fate decisions during the GC response.

CD4+ T Cell-Released Extracellular Vesicles Potentiate the Efficacy of the HBsAg Vaccine by Enhancing B Cell Responses

T cells secrete bioactive extracellular vesicles (EVs), but the potential biological effects of CD4+ T cell EVs are not clear. The main purpose of this study is to investigate the effects of CD4+ T cell-derived EVs on B cell responses and examine their role in antigen-mediated humoral immune responses. In this study, CD4+ T cell EVs are purified from activated CD4+ T cells in vitro. After immunization with the Hepatitis B surface antigen (HBsAg) vaccine, CD4+ T cell EVs-treated mice show stronger humoral immune responses, which is indicated by a greater Hepatitis B surface antibody (HBsAb) level in serum and a greater proportion of plasma cells in bone marrow. In addition, it is found that EVs released from activated CD4+ T cells play an important role in B cell responses in vitro, which significantly promote B cell activation, proliferation, and antibody production. Interestingly, antigen-specific CD4+ T cell EVs are found to be more efficient than control EVs in enhancing B cell responses. Furthermore, it is shown that CD40 ligand (CD40L) is involved in CD4+ T cell EVs-mediated B cell responses. Overall, the results have demonstrated that CD4+ T cell EVs enhance B cell responses and serve as a novel immunomodulator to promote antigen-specific humoral immune responses.

IL-10 producing regulatory and helper T-cells in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a highly heterogeneous autoimmune disease characterised by the production of pathogenic autoantibodies against nuclear self-antigens. The anti-inflammatory and tolerogenic cytokine Interleukin-10 appears to play a paradoxical pathogenic role in SLE and is therefore currently therapeutically targeted in clinical trials. It is generally assumed that the pathogenic effect of IL-10 in SLE is due to its growth and differentiation factor activity on autoreactive B-cells, but effects on other cells might also play a role. To date, a unique cellular source of pathogenic IL-10 in SLE has not been identified. In this review, we focus on the contribution of different CD4⁺T-cell subsets to IL-10 and autoantibody production in SLE. In particular, we discuss that IL-10 produced by different subsets of adaptive regulatory T-cells, follicular helper T-cells and extra-follicular B-helper T-cells is likely to have different effects on autoreactive B-cell responses. A better understanding of the role of IL-10 in B-cell responses and lupus would allow to identify the most promising therapies for individual SLE patients in the future.

Transcriptome sequencing of hybrid bester sturgeon: Responses to poly (I:C) in the context of comparative immunogenomics

Sturgeons represent a substantial scientific interest due to their high economic value, endangered status and also as the most primitive group of ray-finned fishes. Rapid progress in knowledge of sturgeon immunity was achieved recently with use of RNA sequencing. We report transcriptome sequencing of gill, head kidney, and spleen of bester sturgeon (a hybrid of beluga Huso huso and sterlet Acipenser ruthenus) injected with synthetic double-stranded RNA (polyI:C). The composition of transcriptome and responses to treatment were examined in the context of comparative genomics with focus on immune genes. Sturgeon transcripts matched to 21.5 k different proteins (blastx). With reference to Atlantic salmon, the functional groups and pathways of the immune system were uniformly represented: at average 36.5 ± 0.8% genes were found. Immune genes comprise a significant fraction of transcriptome. Among twenty genes with highest transcription levels, five are specialized immune genes and two encode heme and iron binding proteins (serotransferrin and hemopexin) also known as acute phase proteins. Challenge induced multiple functional groups including apoptosis, cell cycle and a number of metabolic pathways. Treatment stimulated innate antiviral immunity, which is well conserved between sturgeon and salmon, the most responsive genes were mx, rsad2 (viperin), interferon induced protein 44 and protein with tetratricopeptide repeats 5, cd87 and receptor transporting protein 3. Results added to knowledge of immune phylogeny. Gain and loss of genes was assessed by comparison with genomes from different phylogenetic groups. Among differentially expressed genes, percentage of acquired and lost genes was much lower in comparison with genes present in all vertebrates. Innate antiviral immunity was subject to the greatest changes in evolution of jawed vertebrates. A significant fraction of genes (15%) was lost in mammals and only half of genes is annotated in public databases as involved in antiviral responses. Change of function may have an important role in evolution of immunity together with gain and loss of genes.

Association between CD40 polymorphisms and systemic lupus erythematosus and correlation between soluble CD40 and CD40 ligand levels in the disease: a meta-analysis

Objective

The aim of this study was to systematically review evidence regarding the association between CD40 polymorphisms and systemic lupus erythematosus and between soluble CD40 (sCD40) and CD40 ligand (sCD40L) levels and systemic lupus erythematosus.

Methods

We performed a meta-analysis on the association between CD40 rs4810495, rs1883832, and rs376545 polymorphisms and systemic lupus erythematosus risk and sCD40/sCD40L levels in patients with systemic lupus erythematosus and controls.

Results

Fourteen studies were included. Ethnicity-specific meta-analysis indicated a significant association between the T allele of CD40 rs4810485 polymorphism and systemic lupus erythematosus in Europeans (odds ratio = 0.715, 95% confidence interval = 0.641–0.832, p < 0.001) and a trend toward an association between the T allele and systemic lupus erythematosus in Asians (odds ratio = 1.255, 95% confidence interval = 0.978–1.810, p = 0.074). Furthermore, a significant association was reported between systemic lupus erythematosus and the C allele of CD40 rs1883832 polymorphism (odds ratio = 1.235, 95% confidence interval = 1.087–1.405, p = 0.001) and A allele of CD40 rs3765456 polymorphism and systemic lupus erythematosus in Asians (odds ratio = 1.184, 95% confidence interval = 1.040–1.348, p = 0.011). sCD40 and sCD40L levels were significantly higher in SLE than in controls (standardized mean difference = 1.564, 95% confidence interval = 0.256–2.872, p = 0.019 and standardized mean difference = 1.499, 95% confidence interval = 1.031–1.967, p < 0.001, respectively). Stratification based on ethnicity revealed higher sCD40L levels in the systemic lupus erythematosus group among European, Asian, North American, and Arab populations.

Conclusions

Our meta-analyses found associations between CD40 rs4810495, rs1883832, and rs376545 polymorphisms and systemic lupus erythematosus susceptibility and significantly higher sCD40 and sCD40L levels in patients with systemic lupus erythematosus than in controls.

Targeting the CD40-CD154 Signaling Pathway for Treatment of Autoimmune Arthritis

Full activation of T lymphocytes requires signals from both T cell receptors and costimulatory molecules. In addition to CD28, several T cell molecules could deliver costimulatory signals, including CD154, which primarily interacts with CD40 on B-cells. CD40 is a critical molecule regulating several B-cell functions, such as antibody production, germinal center formation and cellular proliferation. Upregulated expression of CD40 and CD154 occurs in immune effector cells and non-immune cells in different autoimmune diseases. In addition, therapeutic benefits have been observed by blocking the CD40-CD154 interaction in animals with collagen-induced arthritis. Given the therapeutic success of the biologics abatacept, which blocks CD28 costimulation, and rituximab, which deletes B cells in the treatment of autoimmune arthritis, the inhibition of the CD40-CD154 axis has two advantages, namely, attenuating CD154-mediated T cell costimulation and suppressing CD40-mediated B-cell stimulation. Furthermore, blockade of the CD40-CD154 interaction drives the conversion of CD4+ T cells to regulatory T cells that mediate immunosuppression. Currently, several biological products targeting the CD40-CD154 axis have been developed and are undergoing early phase clinical trials with encouraging success in several autoimmune disorders, including autoimmune arthritis. This review addresses the roles of the CD40-CD154 axis in the pathogenesis of autoimmune arthritis and its potential as a therapeutic target.

Class-Switch Recombination Occurs Infrequently in Germinal Centers

Class-switch recombination (CSR) is a DNA recombination process that replaces the immunoglobulin (Ig) constant region for the isotype that can best protect against the pathogen. Dysregulation of CSR can cause self-reactive BCRs and B cell lymphomas; understanding the timing and location of CSR is therefore important. Although CSR commences upon T cell priming, it is generally considered a hallmark of germinal centers (GCs). Here, we have used multiple approaches to show that CSR is triggered prior to differentiation into GC B cells or plasmablasts and is greatly diminished in GCs. Despite finding a small percentage of GC B cells expressing germline transcripts, phylogenetic trees of GC BCRs from secondary lymphoid organs revealed that the vast majority of CSR events occurred prior to the onset of somatic hypermutation. As such, we have demonstrated the existence of IgM-dominated GCs, which are unlikely to occur under the assumption of ongoing switching.

Heterogeneity of Memory Marginal Zone B Cells

The marginal zone (MZ) is largely composed of a unique subpopulation of B cells, the so-called MZ-B cells. At a molecular level, memory B cells are characterized by the presence of somatically mutated IGV genes. The earliest studies in the rat have documented the presence of hapten-specific MZ-B cells after immunization in the MZ. This work later received experimental support demonstrating that the IGHV-Cµ transcripts expressed by phenotypically defined splenic MZ-B cells (defined as CD90^negIgM^highIgD^low B cells) can carry somatic hypermutation. However, only a minor fraction (< 10%-20%) of these MZ-B cells is mutated and is considered to represent memory B cells. Memory B cells can either be class-switched (IgG, IgA, IgE), or non-class-switched (IgM) B cells. B cells in the MZ are a heterogeneous population of cells and both naïve MZ-B cells; class switched and unswitched memory MZ-B cells are present at this unique site in the spleen. Naïve MZ-B cells carry unmutated Ig genes, produce low-affinity IgM molecules and constitute a first line of defense against invading pathogens. Memory MZ-B cells express high-affinity Ig molecules, directed to (microbial) antigens that have been encountered. In this review, we report on the memory compartment of splenic MZ-B cells in the rat to provide insights into the origin and function of these memory MZ-B cells.

Multiple sclerosis risk variants alter expression of co-stimulatory genes in B cells

The increasing evidence supporting a role for B cells in the pathogenesis of multiple sclerosis prompted us to investigate the influence of known susceptibility variants on the surface expression of co-stimulatory molecules in these cells. Using flow cytometry we measured surface expression of CD40 and CD86 in B cells from 68 patients and 162 healthy controls that were genotyped for the multiple sclerosis associated single nucleotide polymorphisms (SNPs) rs4810485, which maps within the CD40 gene, and rs9282641, which maps within the CD86 gene. We found that carrying the risk allele rs4810485*T lowered the cell-surface expression of CD40 in all tested B cell subtypes (in total B cells P ≤ 5.10 × 10⁻⁵ in patients and ≤4.09 × 10⁻⁶ in controls), while carrying the risk allele rs9282641*G increased the expression of CD86, with this effect primarily seen in the naïve B cell subset (P = 0.048 in patients and 5.38 × 10⁻⁵ in controls). In concordance with these results, analysis of RNA expression demonstrated that the risk allele rs4810485*T resulted in lower total CD40 expression (P = 0.057) but with an increased proportion of alternative splice-forms leading to decoy receptors (P = 4.00 × 10⁻⁷). Finally, we also observed that the risk allele rs4810485*T was associated with decreased levels of interleukin-10 (P = 0.020), which is considered to have an immunoregulatory function downstream of CD40. Given the importance of these co-stimulatory molecules in determining the immune reaction that appears in response to antigen our data suggest that B cells might have an important antigen presentation and immunoregulatory role in the pathogenesis of multiple sclerosis.

The Use of Anti-CD40 mAb in Cancer

Immunomodulatory monoclonal antibody (mAb) therapy is at the forefront of developing cancer therapeutics with numerous targeted agents proving highly effective in selective patients at stimulating protective host immunity, capable of eradicating established tumours and leading to long-term disease-free states. The cell surface marker CD40 is expressed on a range of immune cells and transformed cells in malignant states whose signalling plays a critical role in modulating adaptive immune responses. Anti-CD40 mAb therapy acts via multiple mechanisms to stimulate anti-tumour immunity across a broad range of lymphoid and solid malignancies. A wealth of preclinical research in this field has led to the successful development of multiple anti-CD40 mAb agents that have shown promise in early-phase clinical trials. Significant progress has been made to enhance the engagement of antibodies with immune effectors through their interactions with Fcγ receptors (FcγRs) by the process of Fc engineering. As more is understood about how to best optimise these agents, principally through the fine-tuning of mAb structure and choice of synergistic partnerships, our ability to generate robust, clinically beneficial anti-tumour activity will form the foundation for the next generation of cancer therapeutics.

Aire-expressing ILC3-like cells in the lymph node display potent APC features

The autoimmune regulator (Aire) serves an essential function for T cell tolerance by promoting the "promiscuous" expression of tissue antigens in thymic epithelial cells. Aire is also detected in rare cells in peripheral lymphoid organs, but the identity of these cells is poorly understood. Here, we report that Aire protein-expressing cells in lymph nodes exhibit typical group 3 innate lymphoid cell (ILC3) characteristics such as lymphoid morphology, absence of "classical" hematopoietic lineage markers, and dependence on RORγt. Aire+ cells are more frequent among lineage-negative RORγt+ cells of peripheral lymph nodes as compared with mucosa-draining lymph nodes, display a unique Aire-dependent transcriptional signature, express high surface levels of MHCII and costimulatory molecules, and efficiently present an endogenously expressed model antigen to CD4+ T cells. These findings define a novel type of ILC3-like cells with potent APC features, suggesting that these cells serve a function in the control of T cell responses.

High-affinity anti-glycan antibodies: challenges and strategies

High-affinity binding of antibodies provides for increased specificity and usually higher effector functions in vivo. This goal, well documented in cancer immunotherapy, is very relevant to vaccines as well, and has particularly significant application toward glycan antigens. The inability to elicit high-affinity antibodies has limited potential applications of glycan-based immunogens, giving rise to insufficient population coverage due to low titers and short duration of protection. That such vaccines have achieved widespread use in spite of these shortcomings highlights the surpassing importance of glycans as prophylactic immunological targets. New advances in the combination of synthetic chemistry, bioconjugation, and mechanistic immunology offer the possibility to vastly expand the number of potential molecular targets in cancer and infectious diseases by opening a wider world of carbohydrate structures to immunological recognition and high-affinity response.

Human Germinal Center B Cells Differ from Naïve and Memory B Cells in CD40 Expression and CD40L-Induced Signaling Response

CD40 expression is required for germinal center (GC) formation and function, but the kinetics and magnitude of signaling following CD40 engagement remain poorly characterized in human B cells undergoing GC reactions. Here, differences in CD40 expression and signaling responses were compared across differentiation stages of mature human tonsillar B cells. A combination of mass cytometry and phospho-specific flow cytometry was used to quantify protein expression and CD40L-induced signaling in primary human naïve, GC, and memory B cells. Protein expression signatures of cell subsets were quantified using viSNE and Marker Enrichment Modeling (MEM). This approach revealed enriched expression of CD40 protein in GC B cells, compared to naïve and memory B cells. Despite this, GC B cells responded to CD40L engagement with lower phosphorylation of NFκB p65 during the first 30 min following CD40L activation. Before CD40L stimulation, GC B cells expressed higher levels of suppressor protein IκBα than naïve and memory B cells. Following CD40 activation, IκBα was rapidly degraded and reached equivalently low levels in naïve, GC, and memory B cells at 30 min following CD40L. Quantifying CD40 signaling responses as a function of bound ligand revealed a correlation between bound CD40L and degree of induced NFκB p65 phosphorylation, whereas comparable IκBα degradation occurred at all measured levels of CD40L binding. These results characterize cell-intrinsic signaling differences that exist in mature human B cells undergoing GC reactions. © 2019 International Society for Advancement of Cytometry.

Targeting the CD40-CD40L pathway in autoimmune diseases: Humoral immunity and beyond

CD40 is a TNF receptor superfamily member expressed on both immune and non-immune cells. Interactions between B cell-expressed CD40 and its binding partner, CD40L, predominantly expressed on activated CD4+ T cells, play a critical role in promoting germinal center formation and the production of class-switched antibodies. Non-hematopoietic cells expressing CD40 can also engage CD40L and trigger a pro-inflammatory response. This article will highlight what is known about the biology of the CD40-CD40L axis in humans and describe the potential contribution of CD40 signaling on both hematopoietic and non-hematopoietic cells to autoimmune disease pathogenesis. Additionally, novel therapeutic approaches to target this pathway, currently being evaluated in clinical trials, are discussed.

Signaling control of antibody isotype switching

Class switch recombination (CSR) generates isotype-switched antibodies with distinct effector functions essential for mediating effective humoral immunity. CSR is catalyzed by activation-induced deaminase (AID) that initiates DNA lesions in the evolutionarily conserved switch (S) regions at the immunoglobulin heavy chain (Igh) locus. AID-initiated DNA lesions are subsequently converted into DNA double stranded breaks (DSBs) in the S regions of Igh locus, repaired by non-homologous end-joining to effect CSR in mammalian B lymphocytes. While molecular mechanisms of CSR are well characterized, it remains less well understood how upstream signaling pathways regulate AID expression and CSR. B lymphocytes express multiple receptors including the B cell antigen receptor (BCR) and co-receptors (e.g., CD40). These receptors may share common signaling pathways or may use distinct signaling elements to regulate CSR. Here, we discuss how signals emanating from different receptors positively or negatively regulate AID expression and CSR.

B Cell-Based Cancer Immunotherapy

B cells are not only producers of antibodies, but also contribute to immune regulation or act as potent antigen-presenting cells. The potential of B cells for cellular therapy is still largely underestimated, despite their multiple diverse effector functions. The CD40L/CD40 signaling pathway is the most potent activator of antigen presentation capacity in B lymphocytes. CD40-activated B cells are potent antigen-presenting cells that induce specific T-cell responses in vitro and in vivo. In preclinical cancer models in mice and dogs, CD40-activated B cell-based cancer immunotherapy was able to induce effective antitumor immunity. So far, there have been only few early-stage clinical studies involving B cell-based cancer vaccines. These trials indicate that B cell-based immunotherapy is generally safe and associated with little toxicity. Furthermore, these studies suggest that B-cell immunotherapy can elicit antitumor T-cell responses. Alongside the recent advances in cellular therapies in general, major obstacles for generation of good manufacturing practice-manufactured B-cell immunotherapies have been overcome. Thus, a first clinical trial involving CD40-activated B cells might be in reach.

The TNF Family of Ligands and Receptors: Communication Modules in the Immune System and Beyond

The tumor necrosis factor (TNF) and TNF receptor (TNFR) superfamilies (TNFSF/TNFRSF) include 19 ligands and 29 receptors that play important roles in the modulation of cellular functions. The communication pathways mediated by TNFSF/TNFRSF are essential for numerous developmental, homeostatic, and stimulus-responsive processes in vivo. TNFSF/TNFRSF members regulate cellular differentiation, survival, and programmed death, but their most critical functions pertain to the immune system. Both innate and adaptive immune cells are controlled by TNFSF/TNFRSF members in a manner that is crucial for the coordination of various mechanisms driving either co-stimulation or co-inhibition of the immune response. Dysregulation of these same signaling pathways has been implicated in inflammatory and autoimmune diseases, highlighting the importance of their tight regulation. Investigation of the control of TNFSF/TNFRSF activities has led to the development of therapeutics with the potential to reduce chronic inflammation or promote anti-tumor immunity. The study of TNFSF/TNFRSF proteins has exploded over the last 30 yr, but there remains a need to better understand the fundamental mechanisms underlying the molecular pathways they mediate to design more effective anti-inflammatory and anti-cancer therapies.

Innate and adaptive stimulation of murine diverse NKT cells result in distinct cellular responses

Natural killer T (NKT) cells recognize glycolipids presented on CD1d. They share features of adaptive T lymphocytes and innate NK cells, and mediate immunoregulatory functions via rapid production of cytokines. Invariant (iNKT) and diverse (dNKT) NKT cell subsets are defined by their TCR. The immunological role of dNKT cells, that do not express the invariant TCRα‐chain used by iNKT cells, is less well explored than that of iNKT cells. Here, we investigated signals driving Toll‐like receptor (TLR) ligand activation of TCR‐transgenic murine dNKT cells. IFN‐γ production by dNKT cells required dendritic cells (DC), cell‐to‐cell contact and presence of TLR ligands. TLR‐stimulated DC activated dNKT cells to secrete IFN‐γ in a CD1d‐, CD80/86‐ and type I IFN‐independent manner. In contrast, a requirement for IL‐12p40, and a TLR ligand‐selective dependence on IL‐18 or IL‐15 was observed. TLR ligand/DC stimulation provoked early secretion of pro‐inflammatory cytokines by both CD62L⁺ and CD62L⁻ dNKT cells. However, proliferation was limited. In contrast, TCR/co‐receptor‐mediated activation resulted in proliferation and delayed production of a broader cytokine spectrum preferentially in CD62L⁻ dNKT cells. Thus, innate (TLR ligand/DC) and adaptive (TCR/co‐receptor) stimulation of dNKT cells resulted in distinct cellular responses that may contribute differently to the formation of immune memory.

Characterization of the in vitro and in vivo properties of CFZ533, a blocking and non-depleting anti-CD40 monoclonal antibody

The CD40-CD154 costimulatory pathway is essential for T cell-dependent immune responses, development of humoral memory, and antigen presenting cell function. These immune functions have been implicated in the pathology of multiple autoimmune diseases as well as allograft rejection. We have generated CFZ533, a fully human, pathway blocking anti-CD40 monoclonal antibody that has been modified with a N297A mutation to render it unable to mediate Fcγ-dependent effector functions. CFZ533 inhibited CD154-induced activation of human leukocytes in vitro, but failed to induce human leukocyte activation. Additionally, CFZ533 was unable to mediate depletion of human CD40 expressing B cells. In vivo, CFZ533 blocked primary and recall T cell-dependent antibody responses in nonhuman primates and abrogated germinal formation without depleting peripheral blood B cells. We also established a relationship between plasma concentrations of CFZ533 and CD40 pathway-relevant pharmacodynamic effects in tissue. Collectively these data support the scientific rationale and posology for clinical utility of this antibody in select autoimmune diseases and solid organ transplantation.

Changes in bursal B cells in chicken during embryonic development and early life after hatching

The bursa of Fabricius, the primary lymphoid organ for B cell development found only in birds, offers novel approaches to study B cell differentiation at various developmental stages. Here, we explored the changes and mechanism involved in the developmental stages of bursal B cells. The bursal B cells rapidly increased in the late embryonic stage and around hatching, which coincided with changes in specific cell surface markers. Moreover, the cells in the bursa were divided by size into small (low forward- and side-scatter) or large (high forward- and side-scatter) via flow cytometry. It is intriguing that the proportion of small and large B cells was reversed during this period. Because little is known about this phenomenon, we hypothesized that size-based B cell population could be used as an indicator to distinguish their status and stage during B cell development in chicken. The results demonstrated that large B cells are actively proliferating cells than small B cells. Additionally, large B cells showed higher mRNA expression of both proliferation- and differentiation-associated genes compared to small B cells. Taken together, these data show that large bursal B cells are the main source of proliferation and differentiation during B cell development in chickens.

Complement serves as a switch between CD4+ T cell-independent and -dependent RBC antibody responses

RBC alloimmunization represents a significant immunological challenge for patients requiring lifelong transfusion support. The majority of clinically relevant non-ABO(H) blood group antigens have been thought to drive antibody formation through T cell-dependent immune pathways. Thus, we initially sought to define the role of CD4+ T cells in formation of alloantibodies to KEL, one of the leading causes of hemolytic transfusion reactions. Unexpectedly, our findings demonstrated that KEL RBCs actually possess the ability to induce antibody formation independent of CD4+ T cells or complement component 3 (C3), two common regulators of antibody formation. However, despite the ability of KEL RBCs to induce anti-KEL antibodies in the absence of complement, removal of C3 or complement receptors 1 and 2 (CR1/2) rendered recipients completely reliant on CD4+ T cells for IgG anti-KEL antibody formation. Together, these findings suggest that C3 may serve as a novel molecular switch that regulates the type of immunological pathway engaged following RBC transfusion.