TACI and BCMA are receptors for a TNF homologue implicated in B-cell autoimmune disease

Association of BAFF with PI3K/Akt/mTOR signaling in lupus nephritis

Systemic lupus erythematosus is a connective tissue disease characterized by autoimmune inflammation, which leads to specific and nonspecific immune disorders with the formation of various autoantibodies by activated B cells. B-cell-activating factor (BAFF) is secreted by macrophages and activated T cells, and is responsible for the proliferation, maturation and differentiation of B cells. However, the mechanism of BAFF involvement in lupus nephritis (LN) remains unclear. The aim of the present study was to investigate the association between BAFF and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling in order to elucidate the pathogenesis of LN. In the present study, 18 patients with LN and 20 controls were included. The clinical data were analyzed and plasma levels of BAFF were measured using an ELISA. The mRNA and protein levels of BAFF, phosphorylated (p)-PI3K, p-Akt and p-mTOR in kidney tissues were measured using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. Plasma BAFF levels were significantly increased in patients with LN compared with the controls (P<0.001). mRNA and protein levels of BAFF, p-PI3K, p-Akt and p-mTOR in kidney tissue were significantly increased in patients with LN compared with the controls (all P<0.001). mRNA and protein levels of BAFF in the kidney tissues of patients with LN were positively correlated with the levels of p-PI3K, p-Akt and p-mTOR. The results of the present study revealed a correlation between BAFF and the PI3K/Akt/mTOR signaling pathway, and it is hypothesized that they are involved in the pathogenesis of LN.

From mechanism to therapies in systemic lupus erythematosus

PURPOSE OF REVIEW

Systemic lupus erythematosus (SLE) is a disabling and deadly disease. Development of novel therapies for SLE has historically been limited by incomplete understanding of immune dysregulation. Recent advances in lupus pathogenesis, however, have led to the adoption or development of new therapeutics, including the first Food and Drug Administration-approved drug in 50 years.

RECENT FINDINGS

Multiple cytokines (interferon, B lymphocyte stimulator, IL-6, and IL-17), signaling pathways (Bruton's Tyrosine Kinase, Janus kinase/signal transducer and activator of transcription), and immune cells are dysregulated in SLE. In this review, we cover seminal discoveries that demonstrate how this dysregulation is integral to SLE pathogenesis and the novel therapeutics currently under development or in clinical trials. In addition, early work suggests metabolic derangements are another target for disease modification. Finally, molecular profiling has led to improved patient stratification in the heterogeneous SLE population, which may improve clinical trial outcomes and therapeutic selection.

SUMMARY

Recent advances in the treatment of SLE have directly resulted from improved understanding of this complicated disease. Rheumatologists may have a variety of novel agents and more precise targeting of select lupus populations in the coming years.

Modelling clinical systemic lupus erythematosus: similarities, differences and success stories

Mouse models of SLE have been indispensable tools to study disease pathogenesis, to identify genetic susceptibility loci and targets for drug development, and for preclinical testing of novel therapeutics. Recent insights into immunological mechanisms of disease progression have boosted a revival in SLE drug development. Despite promising results in mouse studies, many novel drugs have failed to meet clinical end points. This is probably because of the complexity of the disease, which is driven by polygenic predisposition and diverse environmental factors, resulting in a heterogeneous clinical presentation. Each mouse model recapitulates limited aspects of lupus, especially in terms of the mechanism underlying disease progression. The main mouse models have been fairly successful for the evaluation of broad-acting immunosuppressants. However, the advent of targeted therapeutics calls for a selection of the most appropriate model(s) for testing and, ultimately, identification of patients who will be most likely to respond.

The BAFF / APRIL axis plays an important role in virus-induced peritoneal responses in rainbow trout

IgM⁺ B cells have been recently demonstrated to be key regulators of peritoneal inflammation in teleost, as a large number of them occupy the peritoneal cavity after 48 h of antigenic stimulation. Despite this, the number of studies addressing the mechanism through which this cell population expands and differentiates in response to stimuli has been scarcely addressed. Because the BAFF/APRIL axis is known to play a major role in B cell survival and differentiation in mammals, we hypothesized that it could be affected in the peritoneal cavity in response to an inflammatory stimulus. To verify this hypothesis, we studied how BAFF, APRIL and the fish-specific related cytokine BALM as well as their putative receptors are regulated in rainbow trout after intraperitoneal (i.p.) injection of viral hemorrhagic septicemia virus (VHSV). When the transcriptional analysis was performed in total cells from the peritoneum, we observed that VHSV provoked an up-regulation of both BAFF and BAFF receptor (BAFF-R) mRNA levels. However, when we examined how isolated peritoneal IgM⁺ B cells were transcriptionally affected by VHSV i.p. injection, we found that APRIL, BALM and the transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) were also up-regulated in response to the virus. IgM^- cells, on the other hand, only up-regulated BALM transcription in response to VHSV. Finally, to gain further insight on the role that these cytokines play in the peritoneum, we have studied their effect on the survival of peritoneal IgM⁺ B cells. This work demonstrates a key role for the BAFF/APRIL axis in the peritoneal inflammatory response and contributes to further understanding how IgM⁺ B cells are regulated at this specific peripheral site.

A mouse model of systemic lupus erythematosus responds better to soluble TACI than to soluble BAFFR, correlating with depletion of plasma cells

The TNF family cytokines B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) support plasma cell survival. It is known that inhibitors of BAFF only (BAFFR-Fc) or BAFF and APRIL (TACI-Fc) administered early enough in an NZB/NZW F1 mouse model of systemic lupus erythematosus (SLE) ameliorate clinical outcomes, pointing to a pathogenic role of BAFF. In the present study, TACI-Fc administrated at a later stage of disease, after onset of autoimmunity, decreased the number of bone marrow plasma cells and slowed down further formation of autoantibodies. TACI-Fc prevented renal damage during a 12-week treatment period regardless of autoantibody levels, while BAFFR-Fc did not despite a similar BAFF-blocking activity in vivo. TACI-Fc also decreased established plasma cells in a T-dependent hapten/carrier immunization system better than single inhibitors of BAFF or APRIL, and sometimes better than combined single inhibitors with at least equivalent BAFF and APRIL inhibitory activities. These results indicate that TACI-Fc can prevent symptoms of renal damage in a mouse model of SLE when BAFFR-Fc cannot, and point to a plasticity of plasma cells for survival factors. Targeting plasma cells with TACI-Fc might be beneficial to prevent autoantibody-mediated damages in SLE.

Efficacy and Safety of Subcutaneous Belimumab in Systemic Lupus Erythematosus: A Fifty-Two-Week Randomized, Double-Blind, Placebo-Controlled Study

Objective

To assess the efficacy and safety of subcutaneous (SC) belimumab in patients with systemic lupus erythematosus (SLE).

Methods

Patients with moderate‐to‐severe SLE (score of ≥8 on the Safety of Estrogens in Lupus Erythematosus National Assessment [SELENA] version of the SLE Disease Activity Index [SLEDAI]) were randomized 2:1 to receive weekly SC belimumab 200 mg or placebo by prefilled syringe in addition to standard SLE therapy for 52 weeks. The primary end point was the SLE Responder Index (SRI4) at week 52. Secondary end points were reduction in the corticosteroid dosage and time to severe flare. Safety was assessed according to the adverse events (AEs) reported and the laboratory test results.

Results

Of 839 patients randomized, 836 (556 in the belimumab group and 280 in the placebo group) received treatment. A total of 159 patients withdrew before the end of the study. At entry, mean SELENA–SLEDAI scores were 10.5 in the belimumab group and 10.3 in the placebo group. More patients who received belimumab were SRI4 responders than those who received placebo (61.4% versus 48.4%; odds ratio [OR] 1.68 [95% confidence interval (95% CI) 1.25–2.25]; P = 0.0006). In the belimumab group, both time to and risk of severe flare were improved (median 171.0 days versus 118.0 days; hazard ratio 0.51 [95% CI 0.35–0.74]; P = 0.0004), and more patients were able to reduce their corticosteroid dosage by ≥25% (to ≤7.5 mg/day) during weeks 40–52 (18.2% versus 11.9%; OR 1.65 [95% CI 0.95–2.84]; P = 0.0732), compared with placebo. AE incidence was comparable between treatment groups; serious AEs were reported by 10.8% of patients taking belimumab and 15.7% of those taking placebo. A worsening of IgG hypoglobulinemia by ≥2 grades occurred in 0.9% of patients taking belimumab and 1.4% of those taking placebo.

Conclusion

In patients with moderate‐to‐severe SLE, weekly SC doses of belimumab 200 mg plus standard SLE therapy significantly improved their SRI4 response, decreased severe disease flares as compared with placebo, and had a safety profile similar to placebo plus standard SLE therapy.

B Cell-Activating Factor Regulates Different Aspects of B Cell Functionality and Is Produced by a Subset of Splenic B Cells in Teleost Fish

In mammals, B cell functionality is greatly influenced by cytokines released by innate cells, such as macrophages or dendritic cells, upon the early recognition of common pathogen patterns through invariant receptors. B cell-activating factor (BAFF) is one of these innate B cell-helper signals and plays a key role in the survival and differentiation of B cells. Although, evolutionarily, teleost fish constitute the first animal group in which adaptive immunity based on Ig receptors is present, fish still rely greatly on innate responses. In this context, we hypothesized that BAFF would play a key role in the control of B cell responses in fish. Supporting this, our results show that teleost BAFF recapitulates mammalian BAFF stimulating actions on B cells, upregulating the expression of membrane MHC II, improving the survival of fish naïve B cells and antibody-secreting cells, and increasing the secretion of IgM. Surprisingly, we also demonstrate that BAFF is not only produced in fish by myeloid cells but is also produced by a subset of splenic B cells. Thus, if this B cell-produced BAFF proves to be actively regulating this same B cell subset, our findings point to an ancient mechanism to control B cell differentiation and survival in lower vertebrates, which has been silenced in mammals in physiological conditions, but reemerges under pathological conditions, such as B cell lymphomas and autoimmune diseases.

Spotlight on blisibimod and its potential in the treatment of systemic lupus erythematosus: evidence to date

B cells in general and BAFF (B cell activating factor of the tumor necrosis factor [TNF] family) in particular have been primary targets of recent clinical trials in systemic lupus erythematosus (SLE). In 2011, belimumab, a monoclonal antibody against BAFF, became the first biologic agent approved for the treatment of SLE. Follow-up studies have shown excellent long-term safety and tolerability of belimumab. In this review, we critically analyze blisibimod, a novel BAFF-neutralizing agent. In contrast to belimumab that only blocks soluble BAFF trimer but not soluble 60-mer or membrane BAFF, blisibimod blocks with high affinity all three forms of BAFF. Furthermore, blisibimod has a unique structure built on four high-affinity BAFF-binding peptides fused to the IgG1-Fc carrier. It was tested in phase I and II trials in SLE where it showed safety and tolerability. While it failed to reach the primary endpoint in a recent phase II trial, post hoc analysis demonstrated its efficacy in SLE patients with higher disease activity. Based on these results, blisibimod is currently undergoing phase III trials targeting this responder subpopulation of SLE patients. The advantage of blisibimod, compared to its competitors, lies in its higher avidity for BAFF, but a possible drawback may come from its immunogenic potential and the anticipated loss of efficacy over time.

Association Study of a Proliferation-inducing Ligand, Spermatogenesis Associated 8, Platelet-derived Growth Factor Receptor-alpha, and POLB Polymorphisms with Systemic Lupus Erythematosus in Chinese Han Population

Background:

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease with complex genetic inheritance. This study was conducted to examine whether the association of a proliferation-inducing ligand (APRIL), spermatogenesis associated 8 (SPATA8), platelet-derived growth factor receptor-alpha (PDGFRA), and DNA polymerase beta (POLB) with SLE can be replicated in a Chinese Han population.

Methods:

Chinese SLE patients (n = 1247) and ethnically and geographically matched healthy controls (n = 1440) were genotyped for the APRIL, SPATA8, PDGFRA, and POLB single-nucleotide polymorphisms (SNPs), rs3803800, rs8023715, rs1364989, and rs12678588 using the Sequenom MassARRAY System.

Results:

The Chinese Han SLE patients and controls had statistically similar frequencies of alleles and genotypes of four gene polymorphisms. Moreover, no association signal was detected on different genetic models (additive, dominant, and recessive, all, P > 0.05) or in SLE subgroups stratified by various clinical manifestations (all, P > 0.05).

Conclusions:

Different genetic backgrounds from different ancestries and various populations may result in different genetic risk factors for SLE. We did not detect any significant association with SNPs of APRIL, SPATA8, PDGFRA, and POLB.

Smoking and pre-existing organ damage reduce the efficacy of belimumab in systemic lupus erythematosus

OBJECTIVES

Belimumab is the first biologic drug approved for Systemic Lupus Erythematosus (SLE). Here, we aimed to investigate the effects of belimumab on clinical and serologic outcomes, and sought to identify predictors of treatment response in three Swedish real-life settings.

METHODS

Fifty-eight patients were enrolled at initiation of belimumab and followed longitudinally for up to 53months. Surveillance outcomes included the SLE Disease Activity Index 2000 (SLEDAI-2K), 100mm Visual Analogue Scales for Physician's Global Assessment (PGA), fatigue, pain and general health, and the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI). Assessment of treatment response included the SLE responder index (SRI). B lymphocyte stimulator (BLyS) levels were determined using ELISA.

RESULTS

SLEDAI-2K (median baseline score: 8.0; IQR: 4.0-13.8), PGA and corticosteroid use decreased during therapy, and patients reported improvements on fatigue, pain, and general health (p<0.0001 for all). SDI scores remained stable (p=0.08). Patients with baseline SDI scores >1 showed decreased probability and prolonged time to attain SRI response (HR: 0.449; 95% CI: 0.208-0.967), as did current smokers compared with non-smokers (HR: 0.103; 95% CI: 0.025-0.427). In contrast, baseline BLyS levels ≥1.2ng/mL predicted increased probability and shorter time to attain SRI response (HR: 2.566; 95% CI: 1.222-5.387).

CONCLUSIONS

Disease activity and corticosteroid usage decreased, patient-reported outcomes improved, and no significant organ damage was accrued during follow-up. Smoking and organ damage predicted reduced treatment efficacy. These findings might contribute to a better selection of patients who are likely to benefit from belimumab.

B Cell-Activating Factor (BAFF)-Targeted B Cell Therapies in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) involve dysregulated immune responses to gut antigens in genetically predisposed individuals. While a better elucidation of IBD pathophysiology has considerably increased the number of treatment options, the need for more effective therapeutic strategies remains a pressing priority. Defects of both non-hematopoietic (epithelial and stromal) and hematopoietic (lymphoid and myeloid) cells have been described in patients with IBD. Within the lymphoid system, alterations of the T cell compartment are viewed as essential in the pathogenesis of IBD. However, growing evidence points to the additional perturbations of the B cell compartment. Indeed, the intestinal lamina propria from IBD patients shows an increased presence of antibody-secreting plasma cells, which correlates with enhanced pro-inflammatory immunoglobulin G production and changes in the quality of non-inflammatory IgA responses. These B cell abnormalities are compounded by the emergence of systemic antibody responses to various autologous and microbial antigens, which predates the clinical diagnosis of IBD and identifies patients with complicated disease. It is presently unclear whether such antibody responses play a pathogenetic role, as B cell depletion with the CD20-targeting monoclonal antibody rituximab did not ameliorate ulcerative colitis in a clinical trial. However, it must be noted that unresponsiveness to rituximab is also observed also in some patients with autoimmune disorders usually responsive to B cell-depleting therapies. In this review, we discussed mechanistic aspects of B cell-based therapies and their potential role in IBD with a special interest on BAFF and BAFF-targeting therapies buoyed by the success of anti-BAFF treatments in rheumatologic disorders.

Serum BAFF and thyroid autoantibodies in autoimmune thyroid disease

BACKGROUND

This study investigated the association of serum B-lymphocyte activating factor (BAFF) levels with autoimmune thyroid disease (AITD) in a Chinese population.

MATERIALS AND METHODS

We enrolled 221 patients with AITD [170 patients with Graves' disease (GD), 51 patients with Hashimoto's thyroiditis (HT)], and 124 healthy controls. Serum BAFF levels, thyroid function and thyroid autoantibody (TAb) levels, including of thyroid-stimulating hormone receptor antibody (TSHRAb), anti-thyroid peroxidase antibody (Anti-TPO Ab), and antithyroglobulin antibody (ATA), were measured at baseline.

RESULTS

Serum BAFF levels were higher in the GD, HT, and AITD groups than in the control group. Significant correlations were observed between BAFF and TSHRAb levels (r=0.238, p=0.018), between BAFF and Anti-TPO Ab levels (p=0.038), and between BAFF and ATA titers (p=0.025) in women but not in men. In addition, serum BAFF levels were significantly associated with free thyroxine (r=0.430, p=0.004) and TSHRAb (r=0.495, p=0.001) levels in women with active GD but not in those with inactive GD.

CONCLUSIONS

Serum BAFF levels are increased in GD, HT, and AITD. The correlation between serum BAFF and TAb levels exhibits a dimorphic pattern, particularly in active GD.

Modeling the chronic lymphocytic leukemia microenvironment in vitro

Microenvironments within the lymph node and bone marrow promote proliferation and drug resistance in chronic lymphocytic leukemia (CLL). Successful treatment of CLL must therefore target the leukemic cells within these compartments. A better understanding of the interaction between CLL cells and the tumor microenvironment has led to the development of in vitro models that mimic the mechanisms that support leukemic cell survival and proliferation in vivo. Employing these models as part of the pre-clinical evaluation of novel therapeutic agents enables a better approximation of their potential clinical efficacy. In this review we summarize the current literature describing how different aspects of the tumor microenvironment have been modeled in vitro and detail how these models have been employed to study the biology of the disease and potential efficacy of novel therapeutic agents.

Unexpected Potency Differences between B-Cell-Activating Factor (BAFF) Antagonist Antibodies against Various Forms of BAFF: Trimer, 60-Mer, and Membrane-Bound

Therapeutic agents antagonizing B-cell-activating factor/B-lymphocyte stimulator (BAFF/BLyS) are currently in clinical development for autoimmune diseases; belimumab is the first Food and Drug Administration-approved drug in more than 50 years for the treatment of lupus. As a member of the tumor necrosis factor superfamily, BAFF promotes B-cell survival and homeostasis and is overexpressed in patients with systemic lupus erythematosus and other autoimmune diseases. BAFF exists in three recognized forms: membrane-bound and two secreted, soluble forms of either trimeric or 60-mer oligomeric states. To date, most in vitro pharmacology studies of BAFF neglect one or more of these forms. Here, we report a comprehensive in vitro cell-based analysis of BAFF in assay systems that measure all forms of BAFF-mediated activation. We demonstrate the effects of these BAFF forms in both a primary human B-cell proliferation assay and in nuclear factor κB reporter assay systems in Chinese hamster ovary cells expressing BAFF receptors and transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI). In contrast to the mouse system, we find that BAFF trimer activates the human TACI receptor. Further, we profiled the activities of two clinically advanced BAFF antagonist antibodies, belimumab and tabalumab. Unexpectedly, we revealed differences in inhibitory potencies against the various BAFF forms, in particular that belimumab does not potently inhibit BAFF 60-mer. Through this increased understanding of the activity of BAFF antagonists against different forms of BAFF, we hope to influence the discovery of BAFF antagonist antibodies with distinct therapeutic mechanisms for improvement in the treatment of lupus or other related autoimmune pathologies.

Overview of pathophysiology and treatment of human lupus nephritis

PURPOSE OF REVIEW

Despite recent developments and treatment successes, the outcome, and prognosis of patients with lupus nephritis (LuN) have not greatly changed since the 1980s. This review covers the application of new concepts to the understanding of renal inflammation and the study of new pharmacologic agents to improve patient outcomes.

RECENT FINDINGS

Studies have shown that the presence of anti-vimentin antibodies and T follicular helper cells in patient biopsies is associated with more severe interstitial inflammation, which has been tied to faster disease progression and onset of end-stage renal disease. Additionally, data regarding the role of serum IgE antidouble-stranded DNA antibodies in LuN by means of mediating IFN1 production by plasmacytoid dendritic cells are highlighted. Finally, a thorough review of completed and currently open clinical trials of therapeutic agents is provided.

SUMMARY

Current management of LuN is guided almost exclusively by glomerular involvement. Based on the data provided in this review, we argue that renal tubulointerstitial inflammation is no less important and represents an overlooked feature in the current clinical approach to patients. Tubulointerstitial inflammation is driven by both adaptive and innate immune mechanisms that are still poorly understood. Studying these pathogenic processes promises to reveal new therapeutic opportunities for those LuN patients with the worst prognosis.

VIDEO ABSTRACT

Alternate video abstract introduction (see Video, Supplemental Digital Content 1, with introduction by two of the authors - VL and KT). Abstract Video: http://links.lww.com/COR/A35.

Exploring BAFF: its expression, receptors and contribution to the immunopathogenesis of Sjögren's syndrome

SS is an autoimmune condition characterized by exocrine gland destruction, autoantibody production, immune complex deposition and systemic complications associated with lymphocytic infiltration of many organs. Genetic, environmental and viral factors play a role in disease aetiology, however, the exact mechanisms driving the immunopathogenesis of SS remain uncertain. Here we discuss a role for B cell activating factor (BAFF), whereby B cell hyperactivity and increased BAFF secretion observed in patients and animal models of the disease can be explained by the altered expression of cell-specific BAFF/BAFF receptor (BAFF-R) variants in several immune cell types. Understanding the role of BAFF/BAFF-R heterogeneity in SS pathogenesis could help to facilitate new treatment strategies for patients.

Engineered T cells: the promise and challenges of cancer immunotherapy

The immune system evolved to distinguish non-self from self to protect the organism. As cancer is derived from our own cells, immune responses to dysregulated cell growth present a unique challenge. This is compounded by mechanisms of immune evasion and immunosuppression that develop in the tumour microenvironment. The modern genetic toolbox enables the adoptive transfer of engineered T cells to create enhanced anticancer immune functions where natural cancer-specific immune responses have failed. Genetically engineered T cells, so-called 'living drugs', represent a new paradigm in anticancer therapy. Recent clinical trials using T cells engineered to express chimeric antigen receptors (CARs) or engineered T cell receptors (TCRs) have produced stunning results in patients with relapsed or refractory haematological malignancies. In this Review we describe some of the most recent and promising advances in engineered T cell therapy with a particular emphasis on what the next generation of T cell therapy is likely to entail.

Follicular Helper T Cells in Systemic Lupus Erythematosus: Why Should They Be Considered as Interesting Therapeutic Targets?

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by B cell hyperactivity leading to the production of autoantibodies, some of which having a deleterious effect. Reducing autoantibody production thus represents a way of controlling lupus pathogenesis, and a better understanding of the molecular and cellular factors involved in the differentiation of B cells into plasma cells could allow identifying new therapeutic targets. Follicular helper T cells (T_FH) represent a distinct subset of CD4⁺ T cells specialized in providing help to B cells. They are required for the formation of germinal centers and the generation of long-lived serological memory and, as such, are suspected to play a central role in SLE. Recent advances in the field of T_FH biology have allowed the identification of important molecular factors involved in T_FH differentiation, regulation, and function. Interestingly, some of these T_FH-related molecules have been described to be dysregulated in lupus patients. In the present review, we give an overview of the aberrant expression and/or function of such key players in lupus, and we highlight their potential as therapeutic targets.

Aptamers in hematological malignancies and their potential therapeutic implications

Aptamers are short DNA/RNA oligonucleotides selected by the process called Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Due to their functional similarity to monoclonal antibodies with some superior characters, such as high specificity and affinity, flexible modification and stability, and lack of toxicity and immunogenicity, they are promising alternative and complementary targeted therapy for hematologic malignancies. The trends in aptamer technology including production, selection, modifications are briefly discussed in this review. The key aspect is to illustrate aptamers against cancer cells in hematologic malignancies especially those that have entered clinical trials. We also discuss some challenges remain in the application of aptamers.

Interleukin (IL)-39 [IL-23p19/Epstein-Barr virus-induced 3 (Ebi3)] induces differentiation/expansion of neutrophils in lupus-prone mice

Interleukin (IL)-12 family cytokines play critical roles in autoimmune diseases. Our previous study has shown that IL-23p19 and Epstein-Barr virus-induced 3 (Ebi3) form a new IL-12 family heterodimer, IL-23p19/Ebi3, termed IL-39, and knock-down of p19 or Ebi3 reduced diseases by transferred GL7⁺ B cells in lupus-prone mice. In the present study, we explore further the possible effect of IL-39 on murine lupus. We found that IL-39 in vitro and in vivo induces differentiation and/or expansion of neutrophils. GL7⁺ B cells up-regulated neutrophils by secreting IL-39, whereas IL-39-deficient GL7⁺ B cells lost the capacity to up-regulate neutrophils in lupus-prone mice and homozygous CD19^cre (CD19-deficient) mice. Finally, we found that IL-39-induced neutrophils had a positive feedback on IL-39 expression in activated B cells by secreting B cell activation factor (BAFF). Taken together, our results suggest that IL-39 induces differentiation and/or expansion of neutrophils in lupus-prone mice.

Generation and characterization of human B lymphocyte stimulator blocking monoclonal antibody

The cytokine, B lymphocyte stimulator (Blys) is essential for activation and proliferation of B cells and is involved in the pathogenesis of B-cell mediated autoimmune diseases. Based on its essential activity, Blys may be a potential therapeutic target for human autoimmune diseases. In this article, we have described the development of a novel humanized anti-Blys antibody, NMB04, that binds with high affinity and specificity to both soluble and membrane bound Blys. This monoclonal antibody has the potential to block Blys binding to all its three receptors, TACI, BCMA and BR-3. Further in vivo studies revealed that NMB04 possessed more potent inhibitory activity against human Blys as compared to an existing antibody, Belimumab. Therefore, NMB04 may have potential as a therapeutic candidate targeting autoimmune diseases.

Antibodies That Block or Activate Mouse B Cell Activating Factor of the Tumor Necrosis Factor (TNF) Family (BAFF), Respectively, Induce B Cell Depletion or B Cell Hyperplasia

B cell activating factor of the TNF family (BAFF), also known as B lymphocyte stimulator, is a ligand required for the generation and maintenance of B lymphocytes. In this study, the ability of different monoclonal antibodies to recognize, inhibit, or activate mouse BAFF was investigated. One of them, a mouse IgG1 named Sandy-2, prevented the binding of BAFF to all of its receptors, BAFF receptor, transmembrane activator and calcium modulating ligand interactor, and B cell maturation antigen, at a stoichiometric ratio; blocked the activity of mouse BAFF on a variety of cell-based reporter assays; and antagonized the prosurvival action of BAFF on primary mouse B cells in vitro A single administration of Sandy-2 in mice induced B cell depletion within 2 weeks, down to levels close to those observed in BAFF-deficient mice. This depletion could then be maintained with a chronic treatment. Sandy-2 and a previously described rat IgG1 antibody, 5A8, also formed a pair suitable for the sensitive detection of endogenous circulating BAFF by ELISA or using a homogenous assay. Interestingly, 5A8 and Sandy-5 displayed activities opposite to that of Sandy-2 by stimulating recombinant BAFF in vitro and endogenous BAFF in vivo These tools will prove useful for the detection and functional manipulation of endogenous mouse BAFF and provide an alternative to the widely used BAFF receptor-Fc decoy receptor for the specific depletion of BAFF in mice.

Characterization and high-yield production of non-N-glycosylated recombinant human BCMA-Fc in Pichia pastoris

B-cell maturation antigen (BCMA) fused at the C-terminus to the Fc portion of human IgG1 (BCMA-Fc) blocks B-cell activating factor (BAFF) and proliferation-inducing ligand (APRIL)-mediated B-cell activation, leading to immune disorders. The fusion protein has been cloned and produced by several engineering cell lines. To reduce cost and enhance production, we attempted to express recombinant human BCMA-Fc (rhBCMA-Fc) in Pichia pastoris under the control of the AOX1 methanol-inducible promoter. To produce the target protein with uniform molecular weight and reduced immunogenicity, we mutated two predicted N-linked glycosylation sites. The secretory yield was improved by codon optimization of the target gene sequence. After fed-batch fermentation under optimized conditions, the highest yield (207 mg/L) of rhBCMA-Fc was obtained with high productivity (3.45 mg/L/h). The purified functional rhBCMA-Fc possessed high-binding affinity to APRIL and dose-dependent inhibition of APRIL-induced proliferative activity in vitro through three-step purification. Thus, this yeast-derived expression method could be a low-cost and effective alternative to the production of rhBCMA-Fc in mammalian cell lines.

A therapeutic role for BLyS antagonists

B lymphocytestimulator (BLyS) is a vital B cell survivalfactor. Overexpressionof BLyS in mice may lead to systemic lupus erythematosus (SLE)-like disease, and treatment of bona fide SLE mice with BLyS antagonists ameliorates disease progression and enhances survival. BLyS overexpression is common in human SLE, and results from a phase I clinical trial with a BLyS antagonistin human SLE have shown the antagonist to be biologicallyactive and safe. These features collectivelypoint to BLyS as an attractive therapeutic target in human disease.

B lymphocytes in systemic lupus erythematosus: lessons from therapy targeting B cells

Systemic lupus erythematosus (SLE) is a complex disease characterizedby numerous autoantibodies and clinical involvement in multiple organ systems. Autoantibodies are usually present in serum for years before the onset of clinical disease. Autoimmunity begins with a limited number of autoantibodiesand evolves to become progressivelymore diverse. Eventually clinical disease ensues. The immunological events triggering the onset of clinical manifestations have not yet been defined. While undoubtedly T cells and dendritic cells appear to play major roles in SLE, a central role for B cells in the pathogenesis of this disease has been brought to the fore in the last few years by work performed both in mice and humans by multiple laboratories.As a result, there is little doubt about the importance of B cells in the development of SLE. Yet much remains to be learned about their role in the ongoing disease process and the merit of targeting B cells for the treatment of SLE. This article will review the role of B cells in human SLE as well as the currently available data on the treatment of SLE by depleting B cells with anti-CD20 (rituximab).

Theory, targets and therapy in systemic lupus erythematosus

The treatment of systemic lupus erythematosus (SLE) has been refined over the years, with the recognition that a fine balance lies between aggressive and prompt therapy and attendant complications brought upon by immunosuppressive therapy itself. However, there has been limited change to the repertoire of drugs available to treat this challenging disease. The current standard therapy for severe manifestations of SLE includes the use of high-dose corticosteroids and cytotoxic agents such as cyclophosphamide (CYC), which have been associated with an increased risk of serious and opportunistic infections. The need for safer, more targeted therapies has been recognized and now, with the exponential increase in the understanding of immunopathogenic mechanisms in SLE, the way has been paved for the development of biologic or targeted therapies in SLE. Although the potential immunosuppression, long-term safety issues and cost-effectiveness remain unclear. These targeted therapies may range from small molecules that specifically inhibit inflammatory processes at an intracellular, cell-cell or cell-matrix level to monoclonal antibodies, soluble receptors or natural antagonists that interfere with cytokine function, cellular activation and inflammatory gene transcription.

BAFF overexpression increases lymphocytic infiltration in Sjögren's target tissue, but only inefficiently promotes ectopic B-cell differentiation

B-cell activating factor (BAFF) levels are increased in rheumatoid arthritis, lupus and primary Sjögren's syndrome (pSS). However, BAFF contribution to pathogenesis is not completely understood. In pSS, immune infiltration of the salivary and lacrimal glands leads to xerostomia and xerophtalmia. Glandular B cell hyperactivation, differentiation into germinal center (GC)-like structures and plasma cell accumulation are histopathological hallmarks that were attributed to increased BAFF. Here, we experimentally tested this hypothesis by overexpressing BAFF in a mouse model of pSS. BAFF overexpression enhanced lymphocytic infiltration and MHCII expression on B cells. Increased BAFF also induced B cell differentiation into GC B cells within the autoimmune target tissue. However, even in these conditions, GC B cells only accounted for <1% of glandular B cells, demonstrating that BAFF is not efficiently promoting ectopic GC formation in pSS and warranting further investigation of therapeutics targeting both BAFF and the related TNF-family member APRIL.

Molecular structure, distribution, and immunology function of TNFSF13B (BAFF) in Nile tilapia (Oreochromis niloticus)

B cell-activating factor (BAFF)is a member of the tumor necrosis factor (TNF) family and plays roles in B cell survival and maturation. In this study, the full-length cDNA of Nile tilapia (Oreochromis niloticus) BAFF (tBAFF) was amplified from the spleen by reverse transcription PCR (RT-PCR). The open reading frame of this cDNA encodes a protein of 261 amino acids containing a predicted transmembrane domain and a furin protease cleavage site, similar to mammalian, avian, and reptile BAFF. Real-time quantitative PCR (qPCR) analysis revealed that tBAFF is present in various tissues and is predominantly expressed in the spleen. The predicted three-dimensional (3D) structure of the Nile tilapia (Oreochromis niloticus) soluble BAFF (tsBAFF) monomer was determined by (3D) structure modeling monomeranalyzed by (3D) structure mouse counterpart. Both tsBAFF and EGFP/tsBAFF were efficiently expressed in Escherichia coli BL21 (DE3), as confirmed by SDS-PAGE and Western blot analysis. After purification, the EGFP/tsBAFF fusion protein showed a fluorescence spectrum similar to that of EGFP. Laser scanning confocal microscopy showed that EGFP/tsBAFF bound to its receptor. In vitro, tsBAFF promoted the proliferation of Nile tilapia and mouse splenic B cells together with/without a priming agent (Staphylococcus aureus Cowan 1, SAC) or anti-mouse IgM. Furthermore, tsBAFF showed a similar proliferation-stimulating effect on mouse B cells compared to msBAFF. These findings indicate that tsBAFF plays an important role in the proliferation of Nile tilapia B cells and has functional cross-reactivity among Nile tilapia and mammals. Therefore, BAFF may represent a useful factor for enhancing immunological efficacy in animals.

Interfering with baffled B cells at the lupus tollway: Promises, successes, and failed expectations

B cells play an important role in systemic lupus erythematosus by acting not only as precursors of autoantibody-producing cells but also as antigen-presenting, cytokine-secreting, and regulatory cells. Unopposed activation of B cells through their B-cell receptor for antigen, as seen in B cells lacking Lyn kinase, results in systemic autoimmunity. The B-cell activating factor of the TNF family (BAFF), nucleic acid-sensing Toll-like receptors (TLRs), and type I interferon can affect B-cell survival and decrease their threshold for activation. Herein we discuss both direct and indirect strategies aimed at targeting B cells in patients with lupus by blocking BAFF, type I interferon, or TLR7 to TLR9. Although BAFF-depleting therapy with belimumab achieved approval for lupus, other BAFF inhibitors were much less beneficial in clinical trials. Inhibitors of the B-cell receptor for antigen signaling and antibodies against type I interferon are in the pipeline. The TLR7 to TLR9 blocker hydroxychloroquine has been in use in patients with lupus for more than 50 years, but oligonucleotide-based inhibitors of TLR7 to TLR9, despite showing promise in animal models of lupus, have not reached the primary end point in a recent phase 1 trial. These data point toward possible redundancies in B-cell signaling/survival pathways, which must be better understood before future clinical trials are executed.

Current and emerging treatment options in the management of lupus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease with variable clinical manifestations. While the clearest guidelines for the treatment of SLE exist in the context of lupus nephritis, patients with other lupus manifestations such as neuropsychiatric, hematologic, musculoskeletal, and severe cutaneous lupus frequently require immunosuppression and/or biologic therapy. Conventional immunosuppressive agents such as mycophenolate mofetil, azathioprine, and cyclophosphamide are widely used in the management of SLE with current more rationalized treatment regimens optimizing the use of these agents while minimizing potential toxicity. The advent of biologic therapies has advanced the treatment of SLE particularly in patients with refractory disease. The CD20 monoclonal antibody rituximab and the anti-BLyS agent belimumab are now widely in use in clinical practice. Several other biologic agents are in ongoing clinical trials. While immunosuppressive and biologic agents are the foundation of inflammatory disease control in SLE, the importance of managing comorbidities such as cardiovascular risk factors, bone health, and minimizing susceptibility to infection should not be neglected.

Participation of B-cell-activating factor receptors in the pathogenesis of immune thrombocytopenia

ESSENTIALS: Dysfunctional B-cell-activating factor (BAFF) system is related to many autoimmune diseases. The regulatory functions of BAFF/BAFF receptors were investigated in an in vitro coculture system. Different regulatory roles of BAFF were investigated via different receptors in immune thrombocytopenia. The upregulated BAFF receptors on autoreactive lymphocytes lead to their hypersensitivity to BAFF.

SUMMARY

BACKGROUND

The pathogenesis of immune thrombocytopenia (ITP) remains enigmatic. B-cell-activating factor (BAFF) and its receptors (BAFF receptor [BAFF-R], transmembrane activator and calcium modulator and cyclophilin ligand interactor [TACI], and B-cell maturation antigen) play central roles in the integrated homeostatic regulation of lymphocytes.

OBJECTIVES

To investigate the pathologic roles of BAFF receptors in regulating the bioactivities of lymphocytes in ITP.

METHODS

An in vitro culture system was established by stimulating CD14(-) peripheral lymphocytes with platelet-preloaded dendritic cells in the presence of recombinant human BAFF (rhBAFF; 20 ng mL(-1)). The functions of BAFF receptors were specifically blocked with blocking antibodies.

RESULTS

BAFF-R, besides prolonging the survival of B cells in both patients and healthy controls, prominently promoted the survival of CD8(+) T cells and the proliferation of B cells in patients with ITP. TACI, as a positive regulator, not only promoted the proliferation of CD4(+) and CD8(+) T cells, but also significantly enhanced the secretion of interleukin-4 in patients with ITP, but not in controls. Besides revealing the pathologic roles of BAFF receptors, these results also indicate that lymphocytes of patients with ITP have enhanced antiapoptotic or proliferative capacity as compared with those from healthy controls when exposed under similar stimulation of rhBAFF. Further study demonstrated that activated autoreactive B cells and CD4(+) T cells from patients with ITP showed significantly higher expression of BAFF-R or TACI than those from healthy controls.

CONCLUSIONS

Both BAFF-R and TACI are pathogenic participants in ITP. Their dysregulated expression in patients with ITP may lead to hyperreactivity of activated autoreactive lymphocytes in response to rhBAFF, and thus is highly significant in the pathogenesis of ITP.

The BAFFling effects of rituximab in lupus: danger ahead?

Suboptimal trial design and concurrent therapies are thought to account for the unexpected failure of two clinical trials of rituximab in patients with systemic lupus erythematosus (SLE). However, in this Opinion article we propose an alternative explanation: that rituximab can trigger a sequence of events that exacerbates disease in some patients with SLE. Post-rituximab SLE flares that are characterized by high levels of antibodies to double-stranded DNA are associated with elevated circulating BAFF (B-cell-activating factor, also known as TNF ligand superfamily member 13B or BLyS) levels, and a high proportion of plasmablasts within the B-cell pool. BAFF not only perpetuates autoreactive B cells (including plasmablasts), particularly when B-cell numbers are low, but also stimulates T follicular helper (TFH) cells. Moreover, plasmablasts and TFH cells promote each others' formation. Thus, repeated rituximab infusions can result in a feedback loop characterized by ever-rising BAFF levels, surges in autoantibody production and worsening of disease. We argue that B-cell depletion should be swiftly followed by BAFF inhibition in patients with SLE.

Molecular characterization and expression analysis of B cell activating factor from rock bream (Oplegnathus fasciatus)

B cell activating factor (BAFF) is a member of the tumor necrosis factor (TNF) ligand family. BAFF has been shown to induce survival and proliferation of lymphocytes. We characterized the gene encoding BAFF (RbBAFF) in rock bream (Oplegnathus fasciatus), and attempted to determine its biological functions upon immune responses. In silico analysis of RbBAFF demonstrated the presence of common TNF ligand family features, including a TNF domain, a D-E loop, and three cysteine residues that are crucial for trimer formation. Amino acid sequence alignment confirmed that RbBAFF and its homologs were conserved at secondary and tertiary levels. Transcriptional analysis indicated that RbBAFF mRNAs were ubiquitously expressed in wide array of tissues. The higher levels of constitutive expression were observed in the kidney, head kidney and spleen, suggesting an important physiological relationship with lymphocytes. Under pathological conditions, RbBAFF mRNA levels were significantly elevated. The role of RbBAFF in lymphocyte survival and proliferation was confirmed by MTT assays and flow cytometry. Recombinant RbBAFF protein (10 μg/mL) was able to prolong the survival and/or enhance the proliferation of rock bream lymphocytes by approximately 30%. Transcription of IL-10 and NFκB-1 was significantly stimulated by RbBAFF. Our findings provide further information regarding fish BAFF gene and its role in adaptive immunity.

Key issues in the management of patients with systemic lupus erythematosus: latest developments and clinical implications

Systemic lupus erythematous (SLE) is a chronic multisystem disease with significant associated morbidity and mortality. A deeper understanding of the pathogenesis of SLE has led to the development of biologic agents, primarily targeting B cells and others inhibiting costimulatory molecules, type I interferons and cytokines such as interleukin-6. Several of these agents have been studied in clinical trials; some have shown promise while others have yielded disappointing results. Economic and regulatory issues continue to hamper the availability of such therapies for SLE patients. With increasing recognition that recurrent flares of disease activity lead to long-term damage accrual, one of the most important recent developments in patient management has been the concept of treat-to-target in SLE while minimizing patient exposure to excessive corticosteroid and other immunosuppressive therapy. This article reviews these key issues in SLE management, outlining recent developments and clinical implications for patients.