Past and present discovery of the BAFF/APRIL system - A bibliometric study from 1999 to 2023

Cytokines from the Tumour Necrosis Factor (TNF) family are important regulators of both physiological and pathological processes. The discovery of novel TNF ligands and receptors, BAFF and APRIL, have opened up new possibilities for scientists to explore the effect of these cytokines on the human immune system. The role of BAFF/APRIL system in B lymphocytes is particularly important for survival and maintenance of homeostasis. Aberrant expression of the system is associated with various immunological disorders. Hence, this study provides a comprehensive overview of the past and present BAFF/APRIL system research development in a bibliometric perspective. To our best knowledge, this is the first ever bibliometric analysis conducted focusing on the BAFF/APRIL system. A total of 1055 relevant documents were retrieved from WoSCC. Microsoft Excel, VOSviewer, and Biblioshiny of R studio were bibliometric tools used to analyse the scientific literature. From 1999, the annual publications showed an upward trend, with Journal of Immunology being the most productive journal. USA leads the race for BAFF/APRIL system research developments. Pascal Schneider, a senior researcher affiliated with University of Lausanne, Switzerland was recognised as the most productive author and institution in the BAFF/APRIL system research field. The research focus transitioned from focusing on the role of the system in B cell biology, to immunological disorders and finally to development of BAFF/APRIL targeting drugs. Despite several studies elucidating briefly the pathway mechanism of BAFF/APRIL system in B-cell selection, substantial research on the mechanism of action in disease models and T cell activation and development of immunomodulating drugs from natural origins remains largely unexplored. Therefore, future research focusing on these areas are crucial for the deeper understanding of the system in disease manifestations and progression allowing a better treatment management for various immunological disorders.

[Research advances on B-cell activating factor and its targeted agents in inflammatory bowel disease]

B-cell activating factor (BAFF), a critical regulator of B cells, is involved in various autoimmune diseases. Inflammatory bowel disease (IBD) is a group of chronic and recurrent intestinal inflammatory disorders with unclear etiology, and its global incidence has been increasing in recent years. Abnormal immune responses triggered by multiple factors are closely related to the pathogenesis of IBD. Previous studies have confirmed the association of B-cell abnormal activation and increased production of autoantibodies with the development of ulcerative colitis. However, the involvement of BAFF in the mechanisms of IBD remains unclear. This review summarizes the potential role of BAFF in the pathogenesis of IBD and provides an overview of targeted therapies on BAFF in IBD, aiming to contribute insights for targeted treatments of IBD.

Safety and clinical activity of autologous RNA chimeric antigen receptor T-cell therapy in myasthenia gravis (MG-001): a prospective, multicentre, open-label, non-randomised phase 1b/2a study

BACKGROUND

Chimeric antigen receptor (CAR) T cells are highly effective in treating haematological malignancies, but associated toxicities and the need for lymphodepletion limit their use in people with autoimmune disease. To explore the use of CAR T cells for the treatment of people with autoimmune disease, and to improve their safety, we engineered them with RNA (rCAR-T)-rather than the conventional DNA approach-to target B-cell maturation antigen (BCMA) expressed on plasma cells. To test the suitability of our approach, we used rCAR-T to treat individuals with myasthenia gravis, a prototypical autoantibody disease mediated partly by pathogenic plasma cells.

METHODS

MG-001 was a prospective, multicentre, open-label, phase 1b/2a study of Descartes-08, an autologous anti-BCMA rCAR-T therapy, in adults (ie, aged ≥18 years) with generalised myasthenia gravis and a Myasthenia Gravis Activities of Daily Living (MG-ADL) score of 6 or higher. The study was done at eight sites (ie, academic medical centres or community neurology clinics) in the USA. Lymphodepletion chemotherapy was not used. In part 1 (phase 1b), participants with Myasthenia Gravis Foundation of America (MGFA) disease class III-IV generalised myasthenia gravis received three ascending doses of Descartes-08 to determine a maximum tolerated dose. In part 2 (phase 2a), participants with generalised myasthenia gravis with MGFA disease class II-IV received six doses at the maximum tolerated dose in an outpatient setting. The primary objective was to establish safety and tolerability of Descartes-08; secondary objectives were to assess myasthenia gravis disease severity and biomarkers in participants who received Descartes-08. This trial is registered with clinicaltrials.gov, NCT04146051.

FINDINGS

We recruited 16 individuals for screening between Jan 7, 2020 and Aug 3, 2022. 14 participants were enrolled (n=3 in part 1, n=11 in part 2). Ten participants were women and four were men. Two individuals did not qualify due to low baseline MG-ADL score (n=1) or lack of generalised disease (n=1). Median follow-up in part 2 was 5 months (range 3-9 months). There was no dose-limiting toxicity, cytokine release syndrome, or neurotoxicity. Common adverse events were headache (six of 14 participants), nausea (five of 14), vomiting (three of 14), and fever (four of 14), which resolved within 24 h of infusion. Fevers were not associated with increased markers of cytokine release syndrome (IL-6, IL-2, and TNF). Mean improvements from baseline to week 12 were -6 (95% CI -9 to -3) for MG-ADL score, -7 (-11 to -3) for Quantitative Myasthenia Gravis score, -14 (-19 to -9) for Myasthenia Gravis Composite score, and -9 (-15 to -3) for Myasthenia Gravis Quality of Life 15-revised score.

INTERPRETATION

In this first study of an rCAR-T therapy in individuals with an autoimmune disease, Descartes-08 appeared to be safe and was well tolerated. Descartes-08 infusions were followed by clinically meaningful decreases on myasthenia gravis severity scales at up to 9 months of follow-up. rCAR-T therapy warrants further investigation as a potential new treatment approach for individuals with myasthenia gravis and other autoimmune diseases.

FUNDING

Cartesian Therapeutics and National Institute of Neurological Disorders and Stroke of the National Institutes of Health.

The BAFF-APRIL System in Cancer

B cell-activating factor (BAFF; also known as CD257, TNFSF13B, BLyS) and a proliferation-inducing ligand (APRIL; also known as CD256, TNFSF13) belong to the tumor necrosis factor (TNF) family. BAFF was initially discovered as a B-cell survival factor, whereas APRIL was first identified as a protein highly expressed in various cancers. These discoveries were followed by over two decades of extensive research effort, which identified overlapping signaling cascades between BAFF and APRIL, controlling immune homeostasis in health and driving pathogenesis in autoimmunity and cancer, the latter being the focus of this review. High levels of BAFF, APRIL, and their receptors have been detected in different cancers and found to be associated with disease severity and treatment response. Here, we have summarized the role of the BAFF-APRIL system in immune cell differentiation and immune tolerance and detailed its pathogenic functions in hematological and solid cancers. We also highlight the emerging therapeutics targeting the BAFF-APRIL system in different cancer types.

Serum levels and significance of soluble B-cell maturation antigen in childhood-onset systemic lupus erythematosus with renal involvement

OBJECTIVE

The aim of this study was to investigate serum levels of soluble B-cell maturation antigen (sBCMA) in childhood-onset systemic lupus erythematous (cSLE) patients with renal involvement, and to elucidate their association with clinical characteristics.

METHODS

116 cases of cSLE patients with renal involvement (84 females and 32 males; median age 11.6 (10.1, 12.9) years) hospitalized in Department of Pediatric Nephrology and Rheumatology, the First Affiliated Hospital, Sun Yat-sen University and 31 healthy controls (HCs) were enrolled. Serum concentrations of sBCMA were determined using enzyme-linked immunosorbent assay (ELISA). Clinical and laboratory information of cSLE patients were retrospectively analyzed.

RESULTS

Serum sBCMA levels were significantly increased in primary cSLE when compared with treated cSLE patients and HCs, whereas there was no significant difference between treated cSLE patients and HCs. Patients with high disease activity displayed higher serum sBCMA levels compared with those with no or mild to moderate disease activity. Positive correlation was observed between serum sBCMA levels and systemic lupus erythematosus disease activity index-2K (SLEDAI-2K), antinuclear antibody titers, anti-double-stranded DNA titers, erythrocyte sedimentation rate, and immunoglobulin G levels, while sBCMA levels were negatively correlated with blood white blood cell count, hemoglobin, platelet count, complement C3 and C4 levels. Serum sBCMA levels decreased as disease ameliorated after treatments among 11 cases with follow-up examinations.

CONCLUSIONS

In cSLE patients with renal involvement, serum sBCMA levels correlated significantly with disease activity, immunological, and hematological parameters, but not with renal parameters. Our results suggest the potential and significance of serum sBCMA as a biomarker in cSLE patients.

The role of soluble B cell maturation antigen as a biomarker in multiple myeloma

Currently used stratification models in myeloma precursor disease as well as staging systems and response criteria in myeloma have limitations including failure to identify functionally high-risk myeloma patients. B-cell maturation antigen, a transmembrane glycoprotein required for long-lived plasma cells, is specific and expressed by myeloma cells. When it sheds from the surface of myeloma cells it can be measured in the blood as serum (sBCMA) and correlated with clinical outcomes in myeloma precursor disease as well as in active myeloma. We performed a literature review using PubMed and found 825 articles since 1992 of which any articles related to sBCMA were reviewed. These studies show the potential of sBCMA to become an important biomarker in myeloma. Here, we describe the potential advantages of sBCMA in the biology, diagnosis, prognosis, and surveillance of myeloma, while also reviewing the challenges that lie ahead before it can be implemented as a clinical tool.

The Role of TRL7/8 Agonists in Cancer Therapy, with Special Emphasis on Hematologic Malignancies

Toll-like receptors (TLR) belong to the pattern recognition receptors (PRR). TLR7 and the closely correlated TLR8 affiliate with toll-like receptors family, are located in endosomes. They recognize single-stranded ribonucleic acid (RNA) molecules and synthetic deoxyribonucleic acid (DNA)/RNA analogs-oligoribonucleotides. TLRs are primarily expressed in hematopoietic cells. There is compiling evidence implying that TLRs also direct the formation of blood cellular components and make a contribution to the pathogenesis of certain hematopoietic malignancies. The latest research shows a positive effect of therapy with TRL agonists on the course of hemato-oncological diseases. Ligands impact activation of antigen-presenting cells which results in production of cytokines, transfer of mentioned cells to the lymphoid tissue and co-stimulatory surface molecules expression required for T-cell activation. Toll-like receptor agonists have already been used in oncology especially in the treatment of dermatological neoplastic lesions. The usage of these substances in the treatment of solid tumors is being investigated. The present review discusses the direct and indirect influence that TLR7/8 agonists, such as imiquimod, imidazoquinolines and resiquimod have on neoplastic cells and their promising role as adjuvants in anticancer vaccines.

γ-secretase inhibitors augment efficacy of BCMA-targeting bispecific antibodies against multiple myeloma cells without impairing T-cell activation and differentiation

We here defined the impacts of γ-secretase inhibitors (GSIs) on T-cell-dependent BCMA-specific multiple myeloma (MM) cell lysis and immunomodulatory effects induced by bispecific antibodies (BisAbs). GSIs-induced membrane BCMA (mBCMA) accumulation reached near maximum within 4 h and sustained over 42h-study period on MM cell lines and patient MM cells. GSIs, i.e., 2 nM LY-411575 or 1 μM DAPT, robustly increased mBCMA densities on CD138⁺ but not CD3⁺ patient cells, concomitantly with minimum soluble/shed BCMA (sBCMA) in 1 day-culture supernatants. In ex vivo MM-T-cell co-cultures, GSIs overcame sBCMA-inhibited MM cell lysis and further enhanced autologous patient MM cell lysis induced by BCMAxCD3 BisAbs, accompanied by significantly enhanced cytolytic markers (CD107a, IFNγ, IL2, and TNFα) in patient T cells. In longer 7 day-co-cultures, LY-411575 minimally affected BCMAxCD3 BisAb (PL33)-induced transient expression of checkpoint (PD1, TIGIT, TIM3, LAG3) and co-stimulatory (41BB, CD28) proteins, as well as time-dependent increases in % effector memory/central memory subsets and CD8/CD4 ratios in patient T cells. Importantly, LY41157 rapidly cleared sBCMA from circulation of MM-bearing NSG mice reconstituted with human T cells and significantly enhanced anti-MM efficacy of PL33 with prolonged host survival. Taken together, these results further support ongoing combination BCMA-targeting immunotherapies with GSI clinical studies to improve patient outcome.

Comprehensive BCMA Expression Profiling in Adult Normal Human Brain Suggests a Low Risk of On-target Neurotoxicity in BCMA-targeting Multiple Myeloma Therapy

B-cell maturation antigen (BCMA) is a target for the treatment of multiple myeloma with cytolytic therapies, such as chimeric antigen receptor T-cells or T-cell redirecting antibodies. To better understand the potential for "on-target/off-tumor" toxicity caused by BCMA-targeting cytolytic therapies in the brain, we investigated normal brain BCMA expression. An immunohistochemistry (IHC) assay using the E6D7B commercial monoclonal antibody was applied to 107 formalin-fixed, paraffin-embedded brain samples (cerebrum, basal ganglia, cerebellum, brainstem; 63 unique donors). Although immunoreactivity was observed in a small number of neurons in brain regions including the striatum, thalamus, midbrain, and medulla, this immunoreactivity was considered nonspecific and not reflective of BCMA expression because it was distinct from the membranous and Golgi-like pattern seen in positive control samples, was not replicated when a different IHC antibody (D6 clone) was used, and was not corroborated by in situ hybridization data. Analysis of RNA-sequencing data from 478 donors in the GTEx and Allen BrainSpan databases demonstrated low levels of BCMA RNA expression in the striatum of young donors with levels becoming negligible beyond 30 years of age. We concluded that BCMA protein is not present in normal adult human brain, and therefore on-target toxicity in the brain is unlikely.

Endogenous soluble receptors sBCMA and sTACI: biomarker, immunoregulator and hurdle for therapy in multiple myeloma

BAFF and APRIL regulate B cell homeostasis by binding to their three receptors BAFFR, BCMA and TACI. The complexity of this system is further increased by shedding of these three receptors; this reduces signaling due to the display of less surface receptors. Further, soluble forms, sBCMA and sTACI, were detected in body fluids and serve as biomarker in malignancies, autoimmune diseases and immunodeficiencies. sBCMA and sTACI function as decoys blocking BAFF and APRIL. BCMA is a promising therapeutic target in multiple myeloma, but sBCMA may reduce therapeutic activity of CAR T cells, bispecific antibodies, and antibody-drug conjugates. Insights into the biochemical mechanism of shedding of BCMA can be harnessed to improve BCMA-directed therapy by blocking its shedding with a γ-secretase inhibitor.

Keeping up with the stress of antibody production: BAFF and APRIL maintain memory plasma cells

Memory plasma cells, also called long-lived plasma cells, provide 'humoral immunity' by continued secretion of protective antibodies against pathogens, which the immune system has once encountered. They are maintained mainly in the bone marrow, docking on to stromal cells individually. In those niches they can apparently persist for decades (Chang et al., 2018 [1]). Integrin-mediated contact to the stromal cell provides an essential survival signal to the plasma cell, activating the PI3K signalling pathway, downregulating FoxO1/3a and repressing the activation of caspases 3 and 7. In a redundant form, the cytokines BAFF and APRIL, ligands of the plasma cell receptors TACI and BCMA, provide a second essential survival signal, preventing activation of caspase 12, as triggered by endoplasmic reticulum stress.

Bispecific T Cell Engagers for the Treatment of Multiple Myeloma: Achievements and Challenges

MM is the second most common hematological malignancy and represents approximately 20% of deaths from hematopoietic cancers. The advent of novel agents has changed the therapeutic landscape of MM treatment; however, MM remains incurable. T cell-based immunotherapy such as BTCEs is a promising modality for the treatment of MM. This review article discusses the advancements and future directions of BTCE treatments for MM.

An update on B-cell maturation antigen-targeted therapies in Multiple Myeloma

Introduction: B-cell maturation antigen (BCMA) targeted therapy (BCMA-TT) has emerged as a promising treatment for Multiple Myeloma (MM). the three most common treatment modalities for targeting BCMA are antibody-drug conjugates (ADCs), bispecific antibody constructs, including BiTE (bispecific T-cell engager) immuno-oncology therapies, and chimeric antigen receptor (CAR)-modified T-cell therapy.Areas covered: The review provides an overview of the main published studies on clinical and pre-clinical data from trials using BCMA-TT.Expert opinion: Despite progresses in survival outcomes and the availability of new drugs, MM remains an incurable disease. ADC is a promising antibody-based treatment and Belantamab mafodotin showed an anti-myeloma effect alone or in combination with other drugs. The major issue of ADC is the occurrence of events interfering with the efficacy and the off-target cytotoxicity. Bispecific antibody constructs are off-the-shelf therapies characterized by a potential rapid availability. The most critical limitation of bispecific antibody constructs is their short half-life necessitating prolonged intravenous infusion. CAR-T cells produced unprecedented results in heavily pretreated RRMM. The most common toxicities include neurologic toxicity and cytokine release syndrome, B-cell aplasia, cytopenias, and hypogammaglobulinemia. Further studies are needed to detect which are the eligible patients who could benefit from one treatment more than another.

Anti-body building: The exercise of advancing immune based myeloma therapies

The last decade has seen a marked improvement in the outcomes of patients with multiple myeloma. Much of this has been due to not only the advent of new therapies, but their inherent ability to be combined into 3 and 4 drug regimens without resulting in unacceptable toxicity. The general gestalt has been to combine agents of varied mechanisms of action. With the primary classes of agents such as proteasome inhibitors and immunomodulatory drugs as bases, the advent of antibody-based therapy in myeloma has allowed us to easily augment these therapies; much in the same way rituximab impacted the lymphoma world. With the approvals of daratumumab, elotuzumab and isatuximab; the myeloma world was ushered into the next wave of targeted agents. Here, we take a look at the current landscape of "off-the-shelf" antibody-based therapies in myeloma and peer into the next wave of multi-functional targeted agents.

Toll-like receptor 4, Toll-like receptor 7 and Toll-like receptor 9 agonists enhance immune responses against blood-stage Plasmodium chabaudi infection in BALB/c mice

BACKGROUND

Toll-like receptor (TLR) signals play vital roles during the blood-stage of malaria infections. However, the roles of TLR agonists in the regulation of immune responses and the development of protective immunity to malaria remain poorly understood.

METHOD

BALB/c mice were pre-treated with TLR4, TLR7 and TLR9 agonists, followed by infection with Plasmodium chabaudi. After infection, splenic dendritic cells (DCs), Th1 cells and programmed death-1 (PD-1) expressed on Th1 cells, as well as regulatory T cells (Tregs) were analyzed by flow cytometry. The levels of IFN-γ, TNF-α, TGF-β and IL-10 in splenocytes and IgG1 and IgG2a in serum were measured by ELISA.

RESULT

Administration of TLR4, TLR7 and TLR9 agonists prior to infection improved disease outcomes. All TLR agonists promoted DC activation, and the proportions of Th1 cells increased. In TLR4, TLR7 and TLR9 agonist treated groups the levels of pro-inflammatory cytokines IFN-γ and TNF-α were elevated, and IgG1 and IgG2a serum levels were also significantly increased. TLR4, TLR7 and TLR9 agonists diminished the activation of Tregs and down-regulated the anti-inflammatory cytokines TGF-β and IL-10. Finally, PD-1 expressed on Th1 cells were decreased in TLR4, TLR7 and TLR9 agonist treated groups compared with control groups.

CONCLUSION

TLR4, TLR7 and TLR9 agonists activated DC-mediated innate immune responses and adaptive immune response, which against the blood-stage of Plasmodium and might be applied to malaria protection and treatment.

Type I IFN-dependent antibody response at the basis of sex dimorphism in the outcome of COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the ongoing coronavirus disease 2019 (COVID-19) pandemic, induces severe pneumonia mainly in elderly males. Epidemiological data clearly indicate sex-based differences in disease outcomes, with men accounting for about 70 % of deaths, despite similar susceptibility to infection. It is well known that females are endowed with higher capacity to produce antibodies, which correlates with viral clearance and disease resolution in the context of SARS-Cov-2 infection. Many X-linked immune genes escape X inactivation showing biallelic expression in female immune cells, particularly in plasmacytoid dendritic cells (pDCs). PDCs are more active in females and endowed with high capability to induce IFN-α-mediated B cell activation and differentiation into antibody-producing plasma cells throughout epigenetic mechanisms linked to trained immunity. Thus, we hypothesize that following SARS-CoV-2 infection, epigenetic modifications of X-linked genes involved in pDC-mediated type I IFN (IFN-I) signaling occurs more effectively in females, for inducing neutralizing antibody response as an immune correlate driving sex-biased disease outcome.

The BAFF / APRIL system as therapeutic target in multiple sclerosis

INTRODUCTION

The complex system of BAFF (B-cell-activating factor of the TNF family) and APRIL (A proliferation-inducing ligand) has been studied in animal models of autoimmune diseases such as those resembling human systemic lupus erythematosus and Sjogren's syndrome and multiple sclerosis (MS). Accumulating evidence suggests that BAFF and APRIL have a physiological role in B cell immunity regulation, however inappropriate production of these factors may represent a key event which disrupts immune tolerance which is associated with systemic autoimmune diseases.

AREAS COVERED

We provide an update on the latest studies of the BAFF/APRIL system in multiple sclerosis, as well as on related clinical trials.

EXPERT OPINION

Experimental and clinical evidence suggests that increased BAFF levels may interfere directly and indirectly with B cell immunity; this can lead to breakdown of immune tolerance, the production of autoantibodies and continuous local intracerebral inflammation and brain tissue destruction. A more comprehensive understanding of the cell/molecular mechanism immune reactions specifically regulated by BAFF/APRIL in MS would better elucidate the specific cell phenotype targeted by actual anti-BAFF/APRIL therapies; this may enable the identification of either specific biomarkers of MS subgroups that would benefit of anti-BAFF/APRIL treatments or new targets of MS-specific anti-BAFF/APRIL therapies.

The TNFSF Members APRIL and BAFF and Their Receptors TACI, BCMA, and BAFFR in Oncology, With a Special Focus in Breast Cancer

Tumor necrosis factor (TNF) superfamily consists of 19 ligands and 29 receptors and is related to multiple cellular events from proliferation and differentiation to apoptosis and tumor reduction. In this review, we overview the whole system, and we focus on A proliferation-inducing ligand (APRIL, TNFSF13) and B cell-activating factor (BAFF, TNFSF13B) and their receptors transmembrane activator and Ca²⁺ modulator (CAML) interactor (TACI, TNFRSF13B), B cell maturation antigen (BCMA, TNFRSF17), and BAFF receptor (BAFFR, TNFRSF13C). We explore their role in cancer and novel biological therapies introduced for multiple myeloma and further focus on breast cancer, in which the modulation of this system seems to be of potential interest, as a novel therapeutic target. Finally, we discuss some precautions which should be taken into consideration, while targeting the APRIL–BAFF system.

Analysis of the receptor BCMA as a biomarker in systemic lupus erythematosus patients

B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) play central roles in B cell development and maturation. Soluble forms of their receptors can be generated by proteolytic cleavage; however, their physiological and clinical roles are unknown. This study aimed to assess the relationships between the receptor soluble B cell maturation antigen (sBCMA) and clinical variables in systemic lupus erythematosus (SLE) patients. Serum cytokine concentrations were measured by ELISA for 129 SLE patients and 34 healthy controls (HCs), and the expression of the receptor BCMA was evaluated on B and plasma cells from 40 subjects. SLE patients showed aberrant expression of the receptor BCMA on B and plasma cells. Soluble levels of the receptor sBCMA and its ligands sAPRIL and sBAFF were increased in SLE patients compared with HCs. Additionally, sBCMA (rs = 0.6177) and sAPRIL (rs = 0.4952) correlated strongly with disease activity. Active SLE patients who achieved low disease activity showed decreased sBCMA (53.30 vs 35.30 ng/mL; p < 0.05) and sBAFF (4.48 vs 2.27 ng/mL; p < 0.05) serum levels after treatment, while sAPRIL expression remained unchanged. At a cutoff value of 22.40 ng/mL, sAPRIL showed high sensitivity (96.12%) and specificity (94.12%) for discrimination between HCs and SLE patients, while sBAFF showed lower sensitivity (82.2%) but higher specificity (94.1%) at a cutoff of 1.195 ng/mL. Relatively high levels of sAPRIL and sBCMA clustered active SLE patients. The receptor sBCMA could be a potential biomarker of disease activity in SLE.

Abnormal expression of BAFF and its receptors in peripheral blood and skin lesions from systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is an autoimmune disease that is characterized by abnormal T and B cells. B-cell activating factor (BAFF) has been suggested to play a crucial role in lupus by promoting the proliferation, differentiation, and survival of B cells. Increased serum levels of BAFF have been found in patients with lupus. However, the expression of BAFF and its receptors on immune cells and in skin has not been systematically reported before. Here, we report that SLE patients showed increased levels of BAFF on circulating CD3⁺ T cells and B-cell maturation antigen (BCMA) on CD14⁺ monocytes and dramatically increased expression of BAFF in lupus skin lesions compared with those of healthy controls. TACI was undetectable on circulating immune cells. An increased serum level of BAFF was also confirmed in lupus patients in this study. Our findings may provide a better understanding of the pathogenesis and predictors of BAFF antibody treatment response, as well as potential targets for skin therapies.

Impact of BAFF Blockade on Inflammation, Germinal Center Reaction and Effector B-Cells During Acute SIV Infection

Memory B-cell dysfunctions and inefficient antibody response suggest germinal center (GC) impairments during HIV/SIV infection with possible contribution of overproduced B-cell activating factor (BAFF). To address this question, we compared proportions and functions of various B-cell subsets and follicular helper T-cells (T_FH) in untreated (Placebo) and BR3-Fc treated (Treated) SIV-infected macaques. From day 2 post-infection (dpi), Treated macaques received one weekly injection of BR3-Fc molecule, a soluble BAFF antagonist, for 4 weeks. Whereas, the kinetics of CD4⁺ T-cell loss and plasma viral loads were comparable in both groups, BAFF blockade delayed the peak of inflammatory cytokines (CXCL10, IFNα), impaired the renewal of plasmacytoid dendritic cells and fostered the decline of plasma CXCL13 titers after 14 dpi. In Treated macaques, proportions of total and naïve B-cells were reduced in blood and spleen whereas SIV-induced loss of marginal zone (MZ) B-cells was only accentuated in blood and terminal ileum. Proportions of spleen GC B-cells and T_FH were similar in both groups, with CD8⁺ T-cells and rare Foxp3⁺ being present in spleen GC. Regardless of treatment, sorted T_FH produced similar levels of IL21, CXCL13, and IFNγ but no IL2, IL4, or BAFF and exhibited similar capacities to support IgG production by autologous or heterologous B-cells. Consistently, most T_FH were negative for BAFF-R and TACI. Higher proportions of resting and atypical (CD21^lo) memory B-cells were present in Treated macaques compared to Placebo. In both groups, we found higher levels of BAFF-R expression on MZ and resting memory B-cells but low levels on atypical memory B-cells. TACI was present on 20-30% of MZ, resting and atypical memory B-cells in Placebo macaques. BAFF blockade decreased TACI expression on these B-cell subsets as well as titers of SIV-specific and vaccine-specific antibodies arguing for BAFF being mandatory for plasma cell survival. Irrespective of treatment, GC B-cells expressed BAFF-R at low level and were negative for TACI. In addition to key information on spleen BAFF-R and TACI expression, our data argue for BAFF contributing to the GC reaction in terminal ileum but being dispensable for the generation of atypical memory B-cells and GC reaction in spleen during T-dependent response against SIV.

B-cell maturation antigen (BCMA) in multiple myeloma: rationale for targeting and current therapeutic approaches

Despite considerable advances in the treatment of multiple myeloma (MM) in the last decade, a substantial proportion of patients do not respond to current therapies or have a short duration of response. Furthermore, these treatments can have notable morbidity and are not uniformly tolerated in all patients. As there is no cure for MM, patients eventually become resistant to therapies, leading to development of relapsed/refractory MM. Therefore, an unmet need exists for MM treatments with novel mechanisms of action that can provide durable responses, evade resistance to prior therapies, and/or are better tolerated. B-cell maturation antigen (BCMA) is preferentially expressed by mature B lymphocytes, and its overexpression and activation are associated with MM in preclinical models and humans, supporting its potential utility as a therapeutic target for MM. Moreover, the use of BCMA as a biomarker for MM is supported by its prognostic value, correlation with clinical status, and its ability to be used in traditionally difficult-to-monitor patient populations. Here, we review three common treatment modalities used to target BCMA in the treatment of MM: bispecific antibody constructs, antibody–drug conjugates, and chimeric antigen receptor (CAR)-modified T-cell therapy. We provide an overview of preliminary clinical data from trials using these therapies, including the BiTE® (bispecific T-cell engager) immuno-oncology therapy AMG 420, the antibody–drug conjugate GSK2857916, and several CAR T-cell therapeutic agents including bb2121, NIH CAR-BCMA, and LCAR-B38M. Notable antimyeloma activity and high minimal residual disease negativity rates have been observed with several of these treatments. These clinical data outline the potential for BCMA-targeted therapies to improve the treatment landscape for MM. Importantly, clinical results to date suggest that these therapies may hold promise for deep and durable responses and support further investigation in earlier lines of treatment, including newly diagnosed MM.

Serum B-Cell Maturation Antigen (BCMA) Levels Differentiate Primary Antibody Deficiencies

BACKGROUND

Primary antibody deficiencies (PADs) are the most prevalent primary immunodeficiencies. More severe forms of PADs-common variable immunodeficiency (CVID) and X-linked agammaglobulinemia (XLA)-require immunoglobulin replacement therapy (IRT) and may have serious complications. Differentiating severe PAD from milder hypogammaglobulinemia not requiring IRT can involve prolonged evaluations and treatment discontinuation. Severe PAD is defined by plasma cell deficiency, but this requires a biopsy to establish. Serum B-cell maturation antigen (sBCMA) is elevated in multiple myeloma, but levels are reduced among patients with myeloma in remission who have hypogammaglobulinemia.

OBJECTIVE

To measure the sBCMA level in 165 subjects to determine whether it differentiates severe PAD-CVID and XLA-from less severe forms not requiring IRT and those without PAD.

METHODS

sBCMA, B cells, and tissue plasma cells were measured among subjects with and without PAD, and correlated to clinical and laboratory data.

RESULTS

Subjects with an IgG level of less than 600 mg/dL had reduced sBCMA levels compared with subjects with PAD with IgG levels of greater than or equal to 600 mg/dL and controls without PAD. sBCMA level was lower in patients with CVID and XLA compared with patients with IgA or IgG deficiency and controls. sBCMA level correlated with gastrointestinal plasma cells. sBCMA level of less than 15 ng/mL had 97% positive predictive value for CVID or XLA, whereas 25 ng/mL or more had an 88% negative predictive value.

CONCLUSIONS

sBCMA level is profoundly reduced in patients with severe PAD, including those with CVID and XLA and those with IgG levels of less than 600 mg/dL. sBCMA level measurement has potential to augment clinical evaluation of PAD. Prospective studies are needed to evaluate sBCMA for new PAD diagnosis and determine the necessity of IRT.

BAFF inhibition in SLE-Is tolerance restored?

The B cell activating factor (BAFF) inhibitor, belimumab, is the first biologic drug approved for the treatment of SLE, and exhibits modest, but durable, efficacy in decreasing disease flares and organ damage. BAFF and its homolog APRIL are TNF-like cytokines that support the survival and differentiation of B cells at distinct developmental stages. BAFF is a crucial survival factor for transitional and mature B cells that acts as rheostat for the maturation of low-affinity autoreactive cells. In addition, BAFF augments innate B cell responses via complex interactions with the B cell receptor (BCR) and Toll like receptor (TLR) pathways. In this manner, BAFF impacts autoreactive B cell activation via extrafollicular pathways and fine tunes affinity selection within germinal centers (GC). Finally, BAFF and APRIL support plasma cell survival, with differential impacts on IgM- and IgG-producing populations. Therapeutically, BAFF and combined BAFF/APRIL inhibition delays disease onset in diverse murine lupus strains, although responsiveness to BAFF inhibition is model dependent, in keeping with heterogeneity in clinical responses to belimumab treatment in humans. In this review, we discuss the mechanisms whereby BAFF/APRIL signals promote autoreactive B cell activation, discuss whether altered selection accounts for therapeutic benefits of BAFF inhibition, and address whether new insights into BAFF/APRIL family complexity can be exploited to improve human lupus treatments.

Dendritic cells aggregate inflammation in experimental osteoarthritis through a toll-like receptor (TLR)-dependent machinery response to challenges

AIMS

Dendritic cells (DCs) and Toll-like receptor (TLR) participate in mediating inflammation process. However, the functional role of TLR expressed on DCs in osteoarthritis (OA) development has not been defined yet. The purpose of this study was to investigate the role and mechanism of TLR and DCs in the progression of experimental osteoarthritis (OA).

MATERIALS AND METHODS

Experimental OA model was induced by iodoacetate injection. Expressions of toll-like receptors in DCs of OA mice were detected by qRT-PCR and flow cytometry. TLR agonists lipopolysaccharide (LPS) and R848 or TLR antagonist FP7 were used, and the levels of TLRs and inflammatory cytokines were examined by qRT-PCR and ELISA.

KEY FINDINGS

The expression levels of TLR family members were increased in DCs derived from synovial fluid of OA mice compared with the sham mice. In vitro, OA mice-derived DCs had increased production of inflammatory cytokine after TLR agonists LPS and R848 challenge, while TLR challenges did not affect DCs maturation. Inhibition of TLR by TLR antagonist FP7 blocked TLR challenges-induced increased inflammation in DCs. In mice, administration of FP7 attenuated LPS-induced inflammatory response and OA condition.

SIGNIFICANCE

Increased TLR expression in OA-derived DCs contributes to the inflammation condition and potentially acts as a therapeutic target for osteoarthritis.

B cell maturation antigen (BCMA)-based immunotherapy for multiple myeloma

Introduction: B cell maturation antigen (BCMA) contributes to MM pathophysiology and is a target antigen for novel MM immunotherapy. Complete responses have been observed in heavily pretreated MM patients after treatment with BCMA antibody-drug conjugates (ADC), chimeric antigen receptor T, and bi-specific T cell engagers (BiTE®). These and other innovative BCMA-targeted therapies transform the treatment landscape and patient outcome in MM. Areas covered: The immunobiological rationale for targeting BCMA in MM is followed by key preclinical studies and available clinical data on efficacy and safety of therapies targeting BCMA from recent phase I/II studies. Expert opinion: BCMA is the most selective MM target antigen, and BCMA-targeted approaches have achieved high responses even in relapse and refractory MM as a monotherapy. Long-term follow-up and correlative studies using immuno-phenotyping and -sequencing will delineate mechanisms of overcoming the immunosuppressive MM bone marrow microenvironment to mediate additive or synergistic anti-MM cytotoxicity. Moreover, they will delineate cellular and molecular events underlying the development of resistance underlying relapse of disease. Most importantly, targeted BCMA-based immunotherapies used earlier in the disease course and in combination (adoptive T cell therapy, mAbs/ADCs, checkpoint and cytokine blockade, and vaccines) have great promise to achieve long-term disease control and potential cure.

B-cell maturation antigen directed monoclonal antibody therapies for multiple myeloma

Multiple myeloma affects 30,000 new patients in the USA yearly, with 5-year median overall survival rates of 82, 62 and 40% for patients in groups I, II and III of the revised international staging system. Novel therapeutic and prognostic tools are changing the way we treat patients with this historically difficult to manage condition. B-cell maturation antigen (BCMA) represents an ideal therapeutic target in myeloma because of its high expression rate and high specificity for myeloma cells. Preclinical data indicate that anti-BCMA monoclonal antibody therapies are highly potent, and initial data from Phase I clinical trials indicate that these drugs are well tolerated. Numerous ongoing Phase I and II clinical trials of anti-BCMA monoclonal antibodies are currently under way.

Analysis of serum B cell-activating factor from the tumor necrosis factor family (BAFF) and its soluble receptors in systemic lupus erythematosus

Objectives

To determine the presence and clinical associations of the soluble receptors of B cell-activating factor from the tumor necrosis factor family (BAFF) in serum of patients with systemic lupus erythematosus (SLE).

Methods

Serum BAFF and soluble BAFF receptor (sBAFF-R) were quantified using ELISA, and soluble B cell maturation antigen (sBCMA) and transmembrane activator and cyclophilin ligand interactor (sTACI) by Luminex, in 87 SLE patients and 17 healthy controls (HC). Disease activity and organ damage were assessed using SLE Disease Activity Index 2000 (SLEDAI-2K) and Systemic Lupus International Collaborating Clinics (SLICC) SLE Damage Index (SDI), respectively.

Results

BAFF and all receptors were detectable in all serum samples. Serum sBCMA and sTACI, but not sBAFF-R, were significantly higher in SLE than in HC. Serum BAFF was also increased in SLE, but this association was attenuated after adjusting for age and ethnicity. Increased serum BAFF was associated with flare and organ damage. Increased serum sBCMA was associated with the presence of anti-dsDNA, but not with overall or organ-specific disease activity, flare or organ damage. Neither sTACI nor sBAFF-R was associated with any SLE clinical parameters in multivariable analysis. While serum BAFF correlated negatively with sBAFF-R in HC, no statistically significant correlations were observed between BAFF and its receptors in SLE patients.

Conclusion

Serum BAFF was associated with flare and organ damage independent of the presence of its soluble receptors. While sBCMA was associated with anti-dsDNA positivity, other soluble BAFF receptors were not associated with SLE clinical indicators.

The Dynamics of the Skin's Immune System

The skin is a complex organ that has devised numerous strategies, such as physical, chemical, and microbiological barriers, to protect the host from external insults. In addition, the skin contains an intricate network of immune cells resident to the tissue, crucial for host defense as well as tissue homeostasis. In the event of an insult, the skin-resident immune cells are crucial not only for prevention of infection but also for tissue reconstruction. Deregulation of immune responses often leads to impaired healing and poor tissue restoration and function. In this review, we will discuss the defensive components of the skin and focus on the function of skin-resident immune cells in homeostasis and their role in wound healing.

Profiling of B-Cell Factors and Their Decoy Receptors in Rheumatoid Arthritis: Association With Clinical Features and Treatment Outcomes

Introduction: B-cell activation is pivotal in rheumatoid arthritis (RA) pathogenesis and represents a relevant therapeutic target. The main aim of this study was to characterize the profiles of B-cell factors and their decoy receptors in RA and evaluate their clinical relevance.

Methods: sBLyS, sAPRIL, sBCMA, sTACI, sBLyS-R, and several cytokines' serum levels were measured by immunoassays in 104 RA patients and 33 healthy controls (HC). An additional group of 42 systemic lupus erythematosus (SLE) patients were enrolled as disease controls. Whole blood IFI44, IFI44L, IFI6, and MX1 gene expression was measured and averaged into an IFN-score. BLyS membrane expression (mBLyS) was assessed on blood cell subsets by flow cytometry.

Results: increased sAPRIL and sBCMA levels were found in RA, whereas BLyS was elevated in very early RA (VERA). No differences were observed for sTACI and sBLyS-R. An increased sBLyS/sBLyS-R ratio was associated with poor clinical outcome at 6 and 12 months in VERA, whereas a positive association with disease activity was observed in established disease. Increased mBLyS expression was found on monocytes, mDCs, neutrophils and B-cells in RA, to a similar extent that in SLE patients. Cluster analysis identified a specific B-cell factors profile overrepresented in RA and associated with autoantibodies, elevated proinflammatory cytokines (IFNα, MIP1α, TNFα, IL-37, and GM-CSF) and increased type-I IFN signature. Increasing sBCMA and sBLyS serum levels upon treatment and mBLyS expression at baseline on monocytes and mDCs, but not B-cells, were associated with poor clinical outcome upon TNFα-blockade.

Conclusions: profound and complex alterations of soluble and membrane-bound B-cell factors are observed in RA associated with clinical outcomes, thus supporting its applicability to guide patient stratification along disease course.

Plasmacytoid dendritic cell in immunity and cancer

Plasmacytoid dendritic cells (pDCs) comprise a subset of dendritic cells characterized by their ability to produce large amount of type I interferon (IFN-I/α). Originally recognized for their role in modulating immune responses to viral stimulation, growing interest has been directed toward their contribution to tumorigenesis. Under normal conditions, Toll-like receptor (TLR)-activated pDCs exhibit robust IFN-α production and promote both innate and adaptive immune responses. In cancer, however, pDCs demonstrate an impaired response to TLR7/9 activation, decreased or absent IFN-α production and contribute to the establishment of an immunosuppressive tumor microenvironment. In addition to IFN-α production, pDCs can also act as antigen presenting cells (APCs) and regulate immune responses to various antigens. The significant role played by pDCs in regulating both the innate and adaptive components of the immune system makes them a critical player in cancer immunology. In this review, we discuss the development and function of pDCs as well as their role in innate and adaptive immunity. Finally, we summarize pDC contribution to cancer pathogenesis, with a special focus on primary malignant brain tumor, their significance in the era of immunotherapy and suggest potential strategies for pDC-targeted therapy.

Phenotypic and Transcriptomic Analysis of Peripheral Blood Plasmacytoid and Conventional Dendritic Cells in Early Drug Naïve Rheumatoid Arthritis

Objective

Dendritic cells (DCs) are key orchestrators of immune function. To date, rheumatoid arthritis (RA) researchers have predominantly focused on a potential pathogenic role for CD1c+ DCs. In contrast, CD141+ DCs and plasmacytoid DCs (pDCs) have not been systematically examined, at least in early RA. In established RA, the role of pDCs is ambiguous and, since disease duration and treatment both impact RA pathophysiology, we examined pDCs, and CD1c+ and CD141+ conventional DCs (cDCs), in early, drug-naïve RA (eRA) patients.

Methods

We analyzed the frequency and phenotype of pDCs, CD1c+, and CD141+ DCs from eRA patients and compared findings with healthy controls. In parallel, we performed transcriptional analysis of >600 immunology-related genes (Nanostring) from peripheral blood pDCs, CD1c+ DCs, B cells, T cells, and monocytes.

Results

All DC subsets were reduced in eRA (n = 44) compared with healthy controls (n = 30) and, for pDCs, this was most marked in seropositive patients. CD141+ and CD1c+ DCs, but not pDCs, had a comparatively activated phenotype at baseline (increased CD86) and CD1c+ DC frequency inversely associated with disease activity. All DC frequencies remained static 12 months after initiation of immunomodulatory therapy despite a fall in activation markers (e.g., HLA-DR, CD40). There was no association between the whole blood interferon gene signature (IGS) and pDC or CD1c+ DC parameters but an inverse association between CD141+ DC frequency and IGS was noted. Furthermore, IFN-I and IFN-III mRNA transcripts were comparable between eRA pDC and other leukocyte subsets (B cells, CD4+, and CD8+ T cells and monocytes) with no obvious circulating cellular source of IFN-I or IFN-III. Transcriptomic analysis suggested increased pDC and CD1c+ DC proliferation in eRA; pDC differentially expressed genes also suggested enhanced tolerogenic function, whereas for CD1c+ DCs, pro-inflammatory transcripts were upregulated.

Discussion

This is the first detailed examination of DC subsets in eRA peripheral blood. Compared with CD1c+ DCs, pDCs are less activated and may be skewed toward tolerogenic functions. CD141+ DCs may be implicated in RA pathophysiology. Our findings justify further investigation of early RA DC biology.

Alterations in B Cell Compartment Correlate with Poor Neutralization Response and Disease Progression in HIV-1 Infected Children

Several B cell defects are reported in HIV-1 infected individuals including variation in B cell subsets, polyclonal B cell activation and exhaustion, with broadly neutralizing antibodies elicited in less than 10–20% of the infected population. HIV-1 disease progression is faster in children than adults. B Lymphocyte Stimulator (BLyS), expressed on dendritic cells (DCs), is a key regulator of B cell homeostasis. Understanding how DCs influence B cell phenotype and functionality (viral neutralization), thereby HIV-1 disease outcome in infected children, is important to develop interventional strategies for restoration of B cell function. In this study, a total of 38 vertically transmitted HIV-1 infected antiretroviral therapy (ART) naïve children and 25 seronegative controls were recruited. Based on the CD4 counts and years post-infection, infected children were categorized as long-term non-progressors (LTNPs) (n = 20) and progressors (n = 18). Eight of these progressors were followed up at 6–12 months post-ART. Percentages (%) of DCs, B cell subsets, and expression of BLyS on DCs were analyzed by flow-cytometry. Plasma levels of B cell growth factors were measured by ELISA and viral neutralization activity was determined using TZM-bl assay. Lower (%) of myeloid DCs (mDCs), plasmacytoid DCs, and high expression of BLyS on mDCs were observed in HIV-1 infected progressors than seronegative controls. Progressors showed lower % of naive B cells, resting memory B cells and higher % of mature activated, tissue-like memory B cells as compared to seronegative controls. Higher plasma levels of IL-4, IL-6, IL-10, and IgA were observed in progressors vs. seronegative controls. Plasma levels of IgG were high in progressors and in LTNPs than seronegative controls, suggesting persistence of hypergammaglobulinemia at all stages of disease. High plasma levels of BLyS in progressors positively correlated with poor viral neutralizing activity. Interestingly on follow up, treatment naïve progressors, post-ART showed increase in resting memory B cells along with reduction in plasma BLyS levels that correlated with improvement in viral neutralization. This is the first study to demonstrate that reduction in plasma BLyS levels correlates with restoration of B cell function, in terms of viral neutralization in HIV-1-infected children.

Monoclonal Antibody: A New Treatment Strategy against Multiple Myeloma

2015 was a groundbreaking year for the multiple myeloma community partly due to the breakthrough approval of the first two monoclonal antibodies in the treatment for patients with relapsed and refractory disease. Despite early disappointments, monoclonal antibodies targeting CD38 (daratumumab) and signaling lymphocytic activation molecule F7 (SLAMF7) (elotuzumab) have become available for patients with multiple myeloma in the same year. Specifically, phase 3 clinical trials of combination therapies incorporating daratumumab or elotuzumab indicate both efficacy and a very favorable toxicity profile. These therapeutic monoclonal antibodies for multiple myeloma can kill target cells via antibody-dependent cell-mediated cytotoxicity, complement-dependent cytotoxicity, and antibody-dependent phagocytosis, as well as by direct blockade of signaling cascades. In addition, their immunomodulatory effects may simultaneously inhibit the immunosuppressive bone marrow microenvironment and restore the key function of immune effector cells. In this review, we focus on monoclonal antibodies that have shown clinical efficacy or promising preclinical anti-multiple myeloma activities that warrant further clinical development. We summarize mechanisms that account for the in vitro and in vivo anti-myeloma effects of these monoclonal antibodies, as well as relevant preclinical and clinical results. Monoclonal antibody-based immunotherapies have already and will continue to transform the treatment landscape in multiple myeloma.