Interaction of the TNF homologues BLyS and APRIL with the TNF receptor homologues BCMA and TACI

Myeloid Cells Induce Infiltration and Activation of B Cells and CD4+ T Follicular Helper Cells to Sensitize Brain Metastases to Combination Immunotherapy

Brain metastasis is a poor prognostic factor in patients with cancer. Despite showing efficacy in many extracranial tumors, immunotherapy with anti-PD-1 mAb or anti-CTLA4 mAb seems to be less effective against intracranial tumors. Promisingly, recent clinical studies have reported that combination therapy with anti-PD-1 and anti-CTLA4 mAbs has a potent antitumor effect on brain metastasis, highlighting the need to elucidate the detailed mechanisms controlling the intracranial tumor microenvironment (TME) to develop effective immunotherapeutic strategies. In this study, we analyzed the tumor-infiltrating lymphocytes in murine models of brain metastasis that responded to anti-CTLA4 and anti-PD-1 mAbs. Activated CD4+ T follicular helper (TFH) cells with high CTLA4 expression characteristically infiltrated the intracranial TME, which were activated by combination anti-CTLA4 and anti-PD-1 treatment. The loss of TFH cells suppressed the additive effect of CTLA4 blockade on anti-PD-1 mAb. B-cell-activating factor belonging to the TNF family (BAFF) and a proliferation-inducing ligand (APRIL) produced by abundant myeloid cells, particularly CD80hiCD206lo proinflammatory M1-like macrophages, in the intracranial TME induced B-cell and TFH-cell infiltration and activation. Furthermore, the intracranial TME of patients with non-small cell lung cancer featured TFH- and B-cell infiltration as tertiary lymphoid structures. Together, these findings provide insights into the immune cell cross-talk in the intracranial TME that facilitates an additive antitumor effect of CTLA4 blockade with anti-PD-1 treatment, supporting the potential of a combination immunotherapeutic strategy for brain metastases. Significance: B-cell and CD4+ T follicular helper cell activation via BAFF/APRIL from abundant myeloid cells in the intracranial tumor microenvironment enables a combinatorial effect of CTLA4 and PD-1 blockade in brain metastases.

Mechanisms for resistance to BCMA-targeted immunotherapies in multiple myeloma

Multiple myeloma (MM) remains incurable and patients eventually face the relapse/refractory dilemma. B cell maturation antigen (BCMA)-targeted immunotherapeutic approaches have shown great effectiveness in patients with relapsed/refractory MM, mainly including chimeric antigen receptor T cells (CAR-T), bispecific T cell engagers (TCEs), and antibody-drug conjugates (ADCs). However, their impact on long-term survival remains to be determined. Nonetheless, resistance to these novel therapies is still inevitable, raising a challenge that we have never met in both laboratory research and clinical practice. In this scenario, the investigation aiming to enhance and prolong the anti-MM activity of BCMA-targeted therapies has been expanding rapidly. Despite considerable uncertainty in our understanding of the mechanisms for their resistance, they have mainly been attributed to antigen-dependency, T cell-driven factors, and (immune) tumor microenvironment. In this review, we summarize the current understanding of the mechanisms for resistance to BCMA-targeted immunotherapies and discuss potential strategies for overcoming it.

Update on B-cell maturation antigen-directed therapies in AL amyloidosis

Systemic light chain (AL) amyloidosis is a rare clonal plasma cell disorder characterized by the production of amyloidogenic immunoglobulin light chains, which causes the formation and deposition of amyloid fibrils, leading to multi-organ dysfunction. Current treatment is directed at the underlying plasma cell clone to achieve a profound reduction in the monoclonal free light chain production. The standard-of-care first-line therapy is a combination of daratumumab, cyclophosphamide, bortezomib and dexamethasone (D-VCd regimen), resulting in high rates of haematological and organ responses. However, AL amyloidosis remains incurable, and all patients inevitably relapse. Hence, novel treatment options are needed for patients with an inadequate response or relapsed/refractory disease. B-cell maturation antigen (BCMA) is a tumour necrosis factor (TNF receptor superfamily receptor overexpressed on plasma cells in multiple myeloma (MM) and AL amyloidosis. Recently, several novel anti-BCMA immunotherapies have been approved for the treatment of relapsed/refractory MM, including antibody-drug conjugate belantamab mafodotin, bispecific antibodies teclistamab and elranatamab and chimeric antigen receptor T-cell therapies idecabtagene vicleucel and ciltacabtagene autoleucel. Despite lower expression than in MM, BCMA is also a promising target in AL amyloidosis. This review aims to provide up-to-date information on the efficacy and toxicity of anti-BCMA therapy in AL amyloidosis.

The Antibody Drug Conjugate, Belantamab-Mafodotin, in the Treatment of Multiple Myeloma: A Comprehensive Review

Despite recent advancements in treatments, including proteasome inhibitors, immunomodulators, and anti-CD38 monoclonal antibodies, multiple myeloma (MM) remains mostly incurable with patients frequently experiencing disease relapses due to therapy resistance. Hence there is an urgent need for innovative treatments for patients with relapsed and/or refractory MM (RRMM). This review examines Belantamab mafodotin, the first antibody-drug conjugate (ADC) targeting B-cell maturation antigen (BCMA), which has shown efficacy in pre-clinical and clinical settings for RRMM. BCMA, a type III transmembrane glycoprotein critical for B cell functions, is predominantly expressed in malignant plasma cells making it a promising therapeutic target. ADCs, comprising a monoclonal antibody, a cytotoxic payload, and a linker, offer a targeted and potent therapeutic approach to cancer treatment. Belantamab mafodotin integrates an afucosylated monoclonal antibody and monomethyl auristatin F (MMAF) as its cytotoxic agent. It induces apoptosis in MM cells by disrupting microtubule formation and interfering with important signaling pathways. The series of DREAMM (Driving Excellence in Approaches to MM) studies have extensively evaluated Belantamab mafodotin in various clinical settings. This review provides a comprehensive overview of pre-clinical and clinical data supporting Belantamab mafodotin as a future therapeutic option for RRMM.

Contributions of each of the BAFF receptors to the lymphocyte profiles in C57BL/6 mice

BAFF, a vital B cell survival and differentiation factor, has three receptors: B-cell maturation antigen (BCMA), transmembrane activator and CAML interactor (TACI) and BR3. Although B cells are greatly reduced in B6.Baff-/- (which harbour no BAFF) and B6.Br3-/- mice (which harbour supra-normal levels of BAFF), the distributions of B cell subsets and relationships between Foxp3+ and CD4+ cells in these mice differ. Using a large panel of B6 congenic knockout and/or transgenic mice, we demonstrate that (1) supra-normal levels of BAFF per se do not explain the phenotypic differences between B6.Baff-/- and B6.Br3-/- mice; (2) B cells are expanded in B6.Taci-/- mice, with preferential expansion of follicular (FO) B cells at the expense of CD19+CD21-/loCD23-/lo B cells but without the preferential expansion of Foxp3+ cells observed in B6 mice bearing a Baff transgene; (3) despite no expansion in total B cells, percentages of FO B cells and marginal zone B cells are higher and percentages of CD19+CD21-/loCD23-/lo B cells are lower in young B6.Bcma-/- mice, consistent with the inability of B6.Br3-/-.Taci-/- mice to recapitulate the B cell profile of B6.Baff-/- mice; and (4) percentages of Foxp3+ cells in B6.Br3-/-.Taci-/- mice are intermediate between those in B6.Br3-/- and B6.Taci-/- mice despite the B cell profile of B6.Br3-/-.Taci-/- mice strongly resembling that of B6.Br3-/- mice. Collectively, our findings point to a non-redundant role for each of the BAFF receptors in determining the ultimate lymphocyte profile of the host. This may have clinically relevant ramifications in that the degree that a candidate therapeutic agent blocks engagement of any given individual BAFF receptor may affect its clinical utility.

BAFF promotes follicular helper T cell development and germinal center formation through BR3 signal

T follicular helper (Tfh) cells represent an important subset of CD4+ T cells that is crucial to the maturation and differentiation of B cells and the production of high-affinity antibodies. Because B cell activating-factor (BAFF), a vital B cell survival factor, is also crucial to B cell maturation and differentiation, we assessed the effects of BAFF on Tfh cell development and function. We demonstrated that deficiency of BAFF, but not of APRIL, markedly inhibited Tfh cell development, germinal center (GC) formation, and antigen-specific antibody production. The promoting effect of BAFF on Tfh cell development was dependent on expression of BR3 on T cells, and its promoting effect on GC formation was dependent on expression of BR3 on both T cells and B cells. BAFF directly promoted expression of the Tfh cell-characteristic genes via NF-κB signaling. This effect did need BR3 expression. Thus, BAFF not only has direct effects on B cells, but it also has direct effects on Tfh cell differentiation via engagement of BR3, which collectively promoted GC formation and production of high-affinity antibodies. This dual effect of BAFF on B cells and Tfh cells may help explain the clinical utility of BAFF antagonists in the management of certain autoimmune diseases.

T cell Dissimilarities in B Cell Activating Factor-Deficient Versus B Cell Activating Factor Receptor 3-Deficient Systemic Lupus Erythematosus-Prone NZM 2328 Mice as Contributors to Their Divergent Clinical Outcomes

OBJECTIVE

We assessed the contributions of B cell and T cell subsets to the disparate clinical outcomes in NZM.Baff-/- and NZM.Br3-/- mice.

METHODS

We assessed in NZM wild-type, NZM.Baff-/-, and NZM.Br3-/- mice numbers and percentages of B cells and subsets, T cells and subsets, and in vivo proliferation and survival of forkhead box P3 (Foxp3)+ cells by fluorescence-activated cell sorting. Relationships between percentages of Foxp3+ cells and numbers of CD19+ and CD4+ cells were assessed by linear regressions.

RESULTS

In each age and sex cohort, percentages and numbers of CD19+ cells were similar in NZM.Baff-/- and NZM.Br3-/- mice. Percentages of CD3+ and CD4+ cells were greater in NZM.Br3-/- than in NZM.Baff-/- mice, with the CD4 to CD3 cell ratios being greater in NZM.Br3-/- than in NZM.Baff-/- mice and percentages of Foxp3+ cells in NZM.Br3-/- mice being lower than in NZM.Baff-/- mice. Percentages of Foxp3+ cells correlated positively with CD19+ cells in NZM.Baff-/- mice but negatively in NZM.Br3-/- mice. In vivo proliferation and survival of Foxp3+ cells were lower in NZM.Baff-/- mice than in NZM.Br3-/- mice.

CONCLUSION

Differences between NZM.Baff-/- and NZM.Br3-/- mice in Foxp3+ cells and their relationships with CD19+ cells may have more to do with their divergent clinical outcomes than do differences in numbers of B cells. These unexpected findings suggest that B cell activating factor (BAFF)-B cell maturation antigen (BCMA) or BAFF-Transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI) interactions may help drive development of clinical systemic lupus erythematosus (SLE) even under conditions of considerable B cell depletion. Insufficient blocking of BAFF-BCMA and BAFF-TACI interactions may lie at the heart of incomplete clinical response to BAFF-targeting agents in human SLE.

Targeting APRIL in the treatment of glomerular diseases

A proliferation-inducing ligand (APRIL) is a key member of the tumor necrosis factor superfamily of cytokines and plays a central role in B-cell survival, proliferation, and Ig class switching. Recently, there has been increasing interest in the role of APRIL and the related cytokine B-cell activating factor in several glomerular diseases, because of their importance in the above processes. The therapeutic inhibition of APRIL represents a potentially attractive immunomodulatory approach that may abrogate deleterious host immune responses in autoimmune diseases while leaving other important functions of humoral immunity intact, such as memory B-cell function and responses to vaccination, in contrast to B-cell-depleting strategies. In this review, we describe the physiological roles of APRIL in B-cell development and their relevance to glomerular diseases, and outline emerging clinical trial data studying APRIL inhibition, with a focus on IgA nephropathy where the clinical development of APRIL inhibitors is in its most advanced stage.

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.

BCMA CAR-T cells in multiple myeloma-ready for take-off?

Although the approval of new drugs has improved the clinical outcome of multiple myeloma (MM), it was widely regarded as incurable over the past decades. However, recent advancements in groundbreaking immunotherapies, such as chimeric antigen receptor T cells (CAR-T), have yielded remarkable results in heavily pretreated relapse/refractory patients, instilling hope for a potential cure. CAR-T are genetically modified cells armed with a novel receptor to specifically recognize and kill tumor cells. Among the potential targets for MM, the B-cell maturation antigen (BCMA) stands out since it is highly and almost exclusively expressed on plasma cells. Here, we review the currently approved BCMA-directed CAR-T products and ongoing clinical trials in MM. Furthermore, we explore innovative approaches to enhance BCMA-directed CAR-T and overcome potential reasons for treatment failure. Additionally, we explore the side effects associated with these novel therapies and shed light on accessibility of CAR-T therapy around the world.

Polymorphonuclear myeloid-derived suppressor cells play a proinflammatory role via TNF-α+ B cells through BAFF/BTK/NF-κB signalling pathway in the pathogenesis of collagen-induced arthritis mice

Although various studies have been performed on the function of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) in RA, the results were conflicting. Here we were trying to clarify the role of PMN-MDSCs in the pathogenesis of RA and its specific mechanisms. We detected the frequencies and counts of PMN-MDSCs, TNF-α+ B cells and Ki67+ B cells in spleen and inflamed joints of collagen-induced arthritis (CIA) mice using flow cytometry. The pathological role of PMN-MDSCs was examined by anti-Ly6G neutralizing antibodies against PMN-MDSCs or adoptive transfer of PMN-MDSCs. And the modulation of PMN-MDSCs on B cells was conducted by coculture assays, RNA-Seq, RT-qPCR, and so on. The mechanism of BAFF regulating B cells was verified through western blot and flow cytometry. PMN-MDSCs accumulated in the spleen and joints of CIA mice. PMN-MDSCs depletion could alleviate the arthritis severity, which was accompanied by decreased TNF-α secretion and proliferation of B cells. And its adoptive transfer also facilitated disease progress. Furthermore, PMN-MDSCs from CIA mice had higher expression level of BAFF, which regulated TNF-α expression, proliferation and apoptosis of B cells in vitro. What's more, BAFF promoted phosphorylation of BTK/NF-κB signalling pathway. And Ibrutinib (BTK inhibitor) could reverse the effect of BAFF on TNF-α expression of B cells. Our study suggested that PMN-MDSCs enhanced disease severity of CIA and manipulated TNF-α expression, proliferation and apoptosis of B cells via BAFF, furthermore, BAFF promoted TNF-α expression through BTK/NF-κB signalling pathway, which demonstrated a novel pathogenesis of PMN-MDSCs in CIA.

TACI and endogenous APRIL in B cell maturation

While many of the genes and molecular pathways in the germinal center B cell response which initiate protective antibody production are known, the contributions of individual molecular players in terminal B cell differentiation remain unclear. We have previously investigated how mutations in TACI gene, noted in about 10% of patients with common variable immunodeficiency, impair B cell differentiation and often, lead to lymphoid hyperplasia and autoimmunity. Unlike mouse B cells, human B cells express TACI-L (Long) and TACI-S (Short) isoforms, but only TACI-S promotes terminal B cell differentiation into plasma cells. Here we show that the expression of intracellular TACI-S increases with B cell activation, and colocalizes with BCMA and their ligand, APRIL. We show that the loss of APRIL impairs isotype class switch and leads to distinct metabolic and transcriptional changes. Our studies suggest that intracellular TACI-S and APRIL along with BCMA direct long-term PC differentiation and survival.

Targeting BCMA in Multiple Myeloma: Advances in Antibody-Drug Conjugate Therapy

Multiple myeloma (MM) is an incurable cancer of the plasma cells. In the last twenty years, treatment strategies have evolved toward targeting MM cells-from the shotgun chemotherapy approach to the slightly more targeted approach of disrupting important MM molecular pathways to the immunotherapy approach that specifically targets MM cells based on protein expression. Antibody-drug conjugates (ADCs) are introduced as immunotherapeutic drugs which utilize an antibody to deliver cytotoxic agents to cancer cells distinctively. Recent investigations of ADCs for MM treatment focus on targeting B cell maturation antigen (BCMA), which regulates B cell proliferation, survival, maturation, and differentiation into plasma cells (PCs). Given its selective expression in malignant PCs, BCMA is one of the most promising targets in MM immunotherapy. Compared to other BCMA-targeting immunotherapies, ADCs have several benefits, such as lower price, shorter production period, fewer infusions, less dependence on the patient's immune system, and they are less likely to over-activate the immune system. In clinical trials, anti-BCMA ADCs have shown safety and remarkable response rates in patients with relapsed and refractory MM. Here, we review the properties and clinical applications of anti-BCMA ADC therapies and discuss the potential mechanisms of resistance and ways to overcome them.

Maternal and cord blood BAFF and APRIL levels during pregnancy

PROBLEM

Dysregulation of factors vital to the survival B cells and/or plasma cells, such as BAFF and APRIL, could be detrimental to a pregnancy.

METHOD OF STUDY

Serially collected first-, second-, and third-trimester serum samples were measured for BAFF and APRIL by ELISA from 150 pregnant women (71 healthy + 79 with a chronic medical disease) at a single medical center. Postpartum serum samples were also collected from the majority of these women. Matched third-trimester and cord blood samples were collected from 168 women (86 healthy + 82 with a chronic medical disease). Data were analyzed by chi-square statistic, unpaired t-test, paired t-test, Mann-Whitney rank sum test, Wilcoxon signed rank test, Spearman rank order correlation, and receiver operator characteristic (ROC) curve analyses as appropriate.

RESULTS

Maternal serum BAFF levels declined as the pregnancies progressed and rebounded postpartum, whereas serum APRIL levels remained relatively flat throughout pregnancy and postpartum. Cord BAFF and APRIL levels correlated positively with gestation age and were considerably greater than the corresponding maternal third-trimester serum BAFF and APRIL levels, respectively. In women who developed preeclampsia, third-trimester BAFF levels were greater, rather than lower, than their corresponding second-trimester BAFF levels. ROC curve analysis suggested a potential role for third-trimester serum BAFF level as a biomarker of preeclampsia.

CONCLUSIONS

BAFF and APRIL are differentially regulated in the mother during and following pregnancy, whereas each is upregulated in the developing fetus. An increase in third-trimester serum BAFF level may portend development of preeclampsia.

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.

BCMA-targeting chimeric antigen receptor T-cell therapy for multiple myeloma

Multiple myeloma (MM) remains an incurable hematologic malignancy, despite the development of numerous innovative therapies during the past two decades. Immunotherapies are changing the treatment paradigm of MM and have improved the overall response and survival of patients with relapsed/refractory (RR) MM. B cell maturation antigen (BCMA), selectively expressed in normal and malignant plasma cells, has been targeted by several immunotherapeutic modalities. Chimeric antigen receptor (CAR) T cells, the breakthrough in cancer immunotherapy, have revolutionized the treatment of B cell malignancies and remarkably improved the prognosis of RRMM. BCMA-targeting CAR T cell therapy is the most developed CAR T cell therapy for MM, and the US Food and Drug Administration has already approved idecabtagene vicleucel (Ide-cel) and ciltacabtagene autoleucel (Cilta-cel) for MM. However, the development of novel BCMA-targeting CAR T cell therapies remains in progress. This review focuses on BCMA-targeting CAR T cell therapy, covering all stages of investigational progress, including the innovative preclinical studies, the initial phase I clinical trials, and the more developed phase II clinical trials. It also discusses possible measures to improve the efficacy and safety of this therapy.

Dual Role of B Cells in Multiple Sclerosis

B cells have emerged as an important immune cell type that can be targeted for therapy in multiple sclerosis (MS). Depleting B cells with anti-CD20 antibodies is effective in treating MS. Yet, atacicept treatment, which blocks B-cell Activating Factor (BAFF) and A Proliferation-Inducing Ligand (APRIL), two cytokines important for B cell development and function, paradoxically increases disease activity in MS patients. The reason behind the failure of atacicept is not well understood. The stark differences in clinical outcomes with these therapies demonstrate that B cells have both inflammatory and anti-inflammatory functions in MS. In this review, we summarize the importance of B cells in MS and discuss the different B cell subsets that perform inflammatory and anti-inflammatory functions and how therapies modulate B cell functions in MS patients. Additionally, we discuss the potential anti-inflammatory functions of BAFF and APRIL on MS disease.

Advancing Biologic Therapy for Refractory Autoimmune Hepatitis

Biologic agents may satisfy an unmet clinical need for treatment of refractory autoimmune hepatitis. The goals of this review are to present the types and results of biologic therapy for refractory autoimmune hepatitis, indicate opportunities to improve and expand biologic treatment, and encourage comparative clinical trials. English abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed. Rituximab (monoclonal antibodies against CD20 on B cells), infliximab (monoclonal antibodies against tumor necrosis factor-alpha), low-dose recombinant interleukin 2 (regulatory T cell promoter), and belimumab (monoclonal antibodies against B cell activating factor) have induced laboratory improvement in small cohorts with refractory autoimmune hepatitis. Ianalumab (monoclonal antibodies against the receptor for B cell activating factor) is in clinical trial. These agents target critical pathogenic pathways, but they may also have serious side effects. Blockade of the B cell activating factor or its receptors may disrupt pivotal B and T cell responses, and recombinant interleukin 2 complexed with certain interleukin 2 antibodies may selectively expand the regulatory T cell population. A proliferation-inducing ligand that enhances T cell proliferation and survival is an unevaluated, potentially pivotal, therapeutic target. Fully human antibodies, expanded target options, improved targeting precision, more effective delivery systems, and biosimilar agents promise to improve efficacy, safety, and accessibility. In conclusion, biologic agents target key pathogenic pathways in autoimmune hepatitis, and early experiences in refractory disease encourage clarification of the preferred target, rigorous clinical trial, and comparative evaluations.

Developing high-affinity decoy receptors to treat multiple myeloma and diffuse large B cell lymphoma

Disease relapse and treatment-induced immunotoxicity pose significant clinical challenges for patients with hematological cancers. Here, we reveal distinctive requirements for neutralizing TNF receptor ligands APRIL and BAFF and their receptor activity in MM and DLBCL, impacting protein translation and production in MM cells and modulating the translation efficiency of the ATM interactor (ATMIN/ACSIZ). Therapeutically, we investigated the use of BCMA decoy receptor (sBCMA-Fc) as an inhibitor of APRIL and BAFF. While wild-type sBCMA-Fc effectively blocked APRIL signaling in MM, it lacked activity in DLBCL due to its weak BAFF binding. To expand the therapeutic utility of sBCMA-Fc, we engineered an affinity-enhanced mutant sBCMA-Fc fusion molecule (sBCMA-Fc V3) 4- and 500-fold stronger in binding to APRIL and BAFF, respectively. The mutant sBCMA-Fc V3 clone significantly enhanced antitumor activity against both MM and DLBCL. Importantly, we also demonstrated an adequate toxicity profile and on-target mechanism of action in nonhuman primate studies.

Distinct binding mode of BAFF antagonist antibodies belimumab and tabalumab, analyzed by computer simulation

B cell-activating factor (BAFF) can bind with specific receptors to activate signalling pathways associated with the B cell activation. Belimumab and tabalumab are anti-BAFF (B cell depleting) monoclonal antibodies, with therapeutic efficacy demonstrated for the treatment of autoimmune disorders, while belimumab was approved by FDA in 2011 as a targeted therapy for systemic lupus erythematosus (SLE) and exhibited better clinical outcome than tabalumab. In this investigation, the combination modes of BAFF-belimumab and BAFF-tabalumab complexes were simulated in silico to better understand the reason for the comparative inhibitory difference between belimumab and tabalumab. The structures of belimumab and tabalumab were constructed through homology modelling. The combination mode of BAFF-belimumab complex was analyzed by molecular dynamics simulation, while that of BAFF-tabalumab complex was analyzed by protein-protein docking following the molecular dynamics simulation. Both belimumab and tabalumab were bound with BAFF at the same hydrophobic center to which the natural receptors of BAFF bind as well. Belimumab heavy chain components I51, F54, K58, D100, D101, L102, L103, and P105 and R27, Y30, K49, and S65 of belimumab light chain contribute to the BAFF-belimumab interaction mainly via hydrogen bonds, salt bridges, and hydrophobic interactions. More importantly, belimumab could bind to L83 of BAFF and produce steric hindrance with the adjacent BAFF trimers, while tabalumab could not. Therefore, our results indicated that belimumab has a better clinical outcome compared with tabalumab mainly because belimumab could bind to L83 of BAFF and interfere the formation of a BAFF 60-mer, besides mediating inhibition of the interaction of BAFF with its receptors.

Multi-omics analysis of naïve B cells of patients harboring the C104R mutation in TACI

Common variable immunodeficiency (CVID) is the most prevalent form of symptomatic primary immunodeficiency in humans. The genetic cause of CVID is still unknown in about 70% of cases. Ten percent of CVID patients carry heterozygous mutations in the tumor necrosis factor receptor superfamily member 13B gene (TNFRSF13B), encoding TACI. Mutations in TNFRSF13B alone may not be sufficient for the development of CVID, as 1% of the healthy population carry these mutations. The common hypothesis is that TACI mutations are not fully penetrant and additional factors contribute to the development of CVID. To determine these additional factors, we investigated the perturbations of transcription factor (TF) binding and the transcriptome profiles in unstimulated and CD40L/IL21-stimulated naïve B cells from CVID patients harboring the C104R mutation in TNFRSF13B and compared them to their healthy relatives with the same mutation. In addition, the proteome of stimulated naïve B cells was investigated. For functional validation, intracellular protein concentrations were measured by flow cytometry. Our analysis revealed 8% less accessible chromatin in unstimulated naïve B cells and 25% less accessible chromatin in class-switched memory B cells from affected and unaffected TACI mutation carriers compared to healthy donors. The most enriched TF binding motifs in TACI mutation carriers involved members from the ETS, IRF, and NF-κB TF families. Validation experiments supported dysregulation of the NF-κB and MAPK pathways. In steady state, naïve B cells had increased cell death pathways and reduced cell metabolism pathways, while after stimulation, enhanced immune responses and decreased cell survival were detected. Using a multi-omics approach, our findings provide valuable insights into the impaired biology of naïve B cells from TACI mutation carriers.

An Overview of CAR T Cell Mediated B Cell Maturation Antigen Therapy

Multiple Myeloma (MM) is one of the incurable types of cancer in plasma cells. While immense progress has been made in the treatment of this malignancy, a large percentage of patients were unable to adapt to such therapy. Additionally, these therapies might be associated with significant diseases and are not always tolerated well in all patients. Since cancer in plasma cells has no cure, patients develop resistance to treatments, resulting in R/R MM (Refractory/Relapsed Multiple Myeloma). BCMA (B cell maturation antigen) is primarily produced on mature B cells. It's up-regulation and activation are associated with multiple myeloma in both murine and human models, indicating that this might be an effective therapeutic target for this type of malignancy. Additionally, BCMA's predictive value, association with effective clinical trials, and capacity to be utilized in previously difficult to observe patient populations, imply that it might be used as a biomarker for multiple myeloma. Numerous kinds of BCMA-targeting medicines have demonstrated antimyeloma efficacy in individuals with refractory/relapsed MM, including CAR T-cell (Chimeric antigen receptor T cell) treatments, ADCs (Antibody-drug conjugate s), bispecific antibody constructs. Among these medications, CART cell-mediated BCMA therapy has shown significant outcomes in multiple myeloma clinical trials. This review article outlines CAR T cell mediated BCMA medicines have the efficiency to change the therapeutic pattern for multiple myeloma significantly.

The potential use of serum interleukin-21 as biomarker for lupus nephritis activity compared to cytokines of the tumor necrosis factor (TNF) family

OBJECTIVE

Lupus nephritis (LN) is a significant consequence of systemic lupus erythematosus (SLE). To the best of our knowledge, this is the first work that focuses on evaluation of serum interleukin (IL-) 21 as a diagnostic biomarker of LN activity, compared to B lymphocyte stimulator (BlyS), tumor necrosis factor ligand superfamily member 13 (TNF-SF13), and traditional techniques of active LN attempting to compare their diagnostic usefulness.

METHODS

Serum levels of IL-21, BlyS, and TNF-SF13 during LN were investigated. Twenty-five biopsy-proven, active LN female patients and 15 SLE patients without active LN and 20 healthy controls (HCs) joined this work.

RESULTS

Serum IL-21 level was significantly higher in active LN group than in inactive LN group. Correlation analysis showed that serum IL-21 levels were significantly correlated with total SLEDAI (r = 0.41, p = 0.03), renal-SLEDAI (r = 0.48, p = 0.04), renal activity index (AI) (r = 0.93; p < 0.001), and 24-h proteinuria (r = 0.51; p > 0.008). Receiver operating characteristic curve (ROC) revealed the ability of serum IL-21 to discriminate between active and inactive LN with 70% sensitivity at >240 pg/ml cutoff point (AUC 0.809).

CONCLUSION

For Egyptian SLE patients, serum levels of IL-21 were superior to TNF-SF13 and BlyS and correlated significantly with the activity indexes of LN, indicating a promising role as a potential biomarker of active LN.

Gene cascade analysis in human granulosa tumor cells (KGN) following exposure to high levels of free fatty acids and insulin

Maternal metabolic disorders such as obesity and diabetes are detrimental factors that compromise fertility and the success rates of medically assisted procreation procedures. During metabolic stress, adipose tissue is more likely to release free fatty acids (FFA) in the serum resulting in an increase of FFA levels not only in blood, but also in follicular fluid (FF). In humans, high concentrations of palmitic acid and stearic acid reduced granulosa cell survival and were associated with poor cumulus-oocyte complex (COC) morphology. Obesity and high levels of circulating FFA were also causatively linked to hampered insulin sensitivity in cells and compensatory hyperinsulinemia. To provide a global picture of the principal upstream signaling pathways and genomic mechanisms involved in this metabolic context, human granulosa-like tumor cells (KGN) were treated with a combination of palmitic acid, oleic acid, and stearic acid at the higher physiological concentrations found in the follicular fluid of women with a higher body mass index (BMI) (≥ 30.0 kg/m2). We also tested a high concentration of insulin alone and in combination with high concentrations of fatty acids. Transcription analysis by RNA-seq with a cut off for fold change of 1.5 and p-value 0.05 resulted in thousands of differentially expressed genes for each treatment. Using analysis software such as Ingenuity Pathway Analysis (IPA), we were able to establish that high concentrations of FFA affected the expression of genes mainly related to glucose and insulin homoeostasis, fatty acid metabolism, as well as steroidogenesis and granulosa cell differentiation processes. The combination of insulin and high concentrations of FFA affected signaling pathways related to apoptosis, inflammation, and oxidative stress. Taken together, our results provided new information on the mechanisms that might be involved in human granulosa cells exposed to high concentrations of FFA and insulin in the contexts of metabolism disorders.

Patient similarity network of newly diagnosed multiple myeloma identifies patient subgroups with distinct genetic features and clinical implications

The remarkable genetic heterogeneity of multiple myeloma poses a substantial challenge for proper prognostication and clinical management of patients. Here, we introduce MM-PSN, the first multiomics patient similarity network of myeloma. MM-PSN enabled accurate dissection of the genetic and molecular landscape of the disease and determined 12 distinct subgroups defined by five data types generated from genomic and transcriptomic profiling of 655 patients. MM-PSN identified patient subgroups not previously described defined by specific patterns of alterations, enriched for specific gene vulnerabilities, and associated with potential therapeutic options. Our analysis revealed that co-occurrence of t(4;14) and 1q gain identified patients at significantly higher risk of relapse and shorter survival as compared to t(4;14) as a single lesion. Furthermore, our results show that 1q gain is the most important single lesion conferring high risk of relapse and that it can improve on the current International Staging Systems (ISS and R-ISS).

Review article: targeting the B cell activation system in autoimmune hepatitis

BACKGROUND

The B cell activation system, consisting of B cell activating factor and a proliferation-inducing ligand, may have pathogenic effects in autoimmune hepatitis.

AIMS

To describe the biological actions of the B cell activation system, indicate its possible role in autoimmune diseases, and evaluate its prospects as a therapeutic target in autoimmune hepatitis METHODS: English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed.

RESULTS

The B cell activating factor is crucial for the maturation and survival of B cells, and it can co-stimulate T cell activation, proliferation, and survival. It can also modulate the immune response by inducing interleukin 10 production by regulatory B cells. A proliferation-inducing ligand modulates and diversifies the antibody response by inducing class-switch recombination in B cells. It can also increase the proliferation, survival, and antigen activation of T cells. These immune stimulatory actions can be modulated by inducing proliferation of regulatory T cells. The B cell activation system has been implicated in diverse autoimmune diseases, and therapeutic blockade is a management strategy now being evaluated in autoimmune hepatitis.

CONCLUSIONS

The B cell activation system has profound effects on B and T cell function in autoimmune diseases. Blockade therapy is being actively evaluated in autoimmune hepatitis. Clarification of the critical pathogenic components of the B cell activation system will improve the targeting, efficacy, and safety of blockade therapy in this disease.

Plasma cell survival: The intrinsic drivers, migratory signals, and extrinsic regulators

Antibody-secreting cells (ASC) are the effectors of protective humoral immunity and the only cell type that produces antibodies or immunoglobulins in mammals. In addition to their formidable capacity to secrete massive quantities of proteins, ASC are terminally differentiated and have unique features to become long-lived plasma cells (LLPC). Upon antigen encounter, B cells are activated through a complex multistep process to undergo fundamental morphological, subcellular, and molecular transformation to become an efficient protein factory with lifelong potential. The ASC survival potential is determined by factors at the time of induction, capacity to migration from induction to survival sites, and ability to mature in the specialized bone marrow microenvironments. In the past decade, considerable progress has been made in identifying factors regulating ASC longevity. Here, we review the intrinsic drivers, trafficking signals, and extrinsic regulators with particular focus on how they impact the survival potential to become a LLPC.

Role of the APRIL molecule in solid tumors

The APRIL molecule, produced by immune cells, their precursors, and cancer cells, is one of the important factors that influences the process of survival and proliferation of cancer cells. In the present review, we summarize the current knowledge on the effects of APRIL on human cancer development and develop a scheme demonstrating the mechanism of the action of APRIL on solid tumors. Understanding the effects of APRIL, including the intracellular signal transduction pathway, may be key for the use of this protein as a biomarker of the cancer process. The correlations observed between APRIL levels and cancer parameters (e.g., disease stage and presence of malignant phenotypes) indicate that APRIL may play an important role, not only in the diagnostic process, but also as a therapeutic target in various cancers.

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.

Teclistamab is an active T cell-redirecting bispecific antibody against B-cell maturation antigen for multiple myeloma

B-cell maturation antigen (BCMA), a member of the tumor necrosis factor family of receptors, is predominantly expressed on the surface of terminally differentiated B cells. BCMA is highly expressed on plasmablasts and plasma cells from multiple myeloma (MM) patient samples. We developed a BCMAxCD3 bispecific antibody (teclistamab [JNJ-64007957]) to recruit and activate T cells to kill BCMA-expressing MM cells. Teclistamab induced cytotoxicity of BCMA+ MM cell lines in vitro (H929 cells, 50% effective concentration [EC50] = 0.15 nM; MM.1R cells, EC50 = 0.06 nM; RPMI 8226 cells, EC50 = 0.45 nM) with concomitant T-cell activation (H929 cells, EC50 = 0.21 nM; MM.1R cells, EC50 = 0.1 nM; RPMI 8226 cells, EC50 = 0.28 nM) and cytokine release. This activity was further increased in the presence of a γ-secretase inhibitor (LY-411575). Teclistamab also depleted BCMA+ cells in bone marrow samples from MM patients in an ex vivo assay with an average EC50 value of 1.7 nM. Under more physiological conditions using healthy human whole blood, teclistamab mediated dose-dependent lysis of H929 cells and activation of T cells. Antitumor activity of teclistamab was also observed in 2 BCMA+ MM murine xenograft models inoculated with human T cells (tumor inhibition with H929 model and tumor regression with the RPMI 8226 model) compared with vehicle and antibody controls. The specific and potent activity of teclistamab against BCMA-expressing cells from MM cell lines, patient samples, and MM xenograft models warrant further evaluation of this bispecific antibody for the treatment of MM. Phase 1 clinical trials (monotherapy, #NCT03145181; combination therapy, #NCT04108195) are ongoing for patients with relapsed/refractory MM.

First-trimester serum BAFF:sFlt-1 ratio as a candidate early biomarker of spontaneous abortion

PROBLEM

Immunologic, angiogenic, and anti-angiogenic factors are associated with spontaneous abortion (SAB). B cell-activating factor (BAFF), a proliferation-inducing ligand (APRIL), placental growth factor (PlGF), and soluble fms-like tyrosine kinase-1 (sFlt-1) may play a role in SAB and may serve singly or in combination as an early biomarker of SAB.

METHOD OF STUDY

In this prospective observational study, serum sFlt-1, PIGF, BAFF, and APRIL levels were measured in the first trimester of pregnancy in a medically diverse group of women and in non-pregnant controls. Associations and discriminative values of first-trimester sFlt-1, PIGF, BAFF, and APRIL levels and the corresponding APRIL:BAFF, BAFF:sFlt-1, and sFlt-1:PlGF ratios with development of SAB were tested.

RESULTS

Median serum BAFF level was lower (p = .007) and median serum sFlt-1 level was higher (p < .001), in the first trimester of pregnancy than in non-pregnant controls. SAB developed in 27 of the pregnant women (11.3%), and first-trimester levels of BAFF (but not APRIL) and sFlt-1 (but not PIGF) were associated with SAB. Using optimal cutoffs determined through receiver operating characteristics curves, the best discriminator of SAB was the serum BAFF:sFlt-1 ratio, specifically among non-nulliparous women and women with prior SAB.

CONCLUSION

First-trimester serum BAFF:sFlt-1 ratio is a candidate indicator/predictor of SAB among non-nulliparous women and women with prior SAB. If validated through additional studies, then early identification of pregnant women at high risk for SAB through this simple blood test would assist in counseling and facilitate clinical trials of therapeutic interventions.

Telitacicept Following Plasma Exchange in the Treatment of Subjects With Recurrent NMOSD: Study Protocol for a Single-Center, Single-Arm, Open-Label Study

Background: Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune demyelinating disease that recurrently relapses and leads to severe disability. The available choices for disease prevention are few or intolerable. Previous studies suggested that telitacicept may provide a promising therapeutic strategy for autoimmune diseases involving B cells. Therefore, this study aims to assess the effectiveness and safety of telitacicept for recurrent NMOSD.

Methods: We will perform a single-arm, single-center, open-label, specialist study with a total enrollment of eight participants. The treatment regimen includes plasma exchange three times and subcutaneous injection of telitacicept for 46 cycles, with a total period of 48 weeks. The primary endpoint is the time to first recurrence after enrollment. Secondary endpoints are Expanded Disability Status Scale (EDSS) score, Opticospinal Impairment Scale (OSIS) score, Hauser Ambulation Index, number of lesions on MRI, and changes in visual evoked potential (VEP), optical coherence tomography (OCT) and immunologic status. All adverse events after medication will be documented and investigated.

Discussion: This study will explore the safety and effectiveness of telitacicept following plasma exchange regarding the time to recurrence in neuromyelitis optica spectrum disorder (NMOSD) for the first time.

Clinical Trial Registration:Chictr.org.cn, identifier ChiCTR1800019427

CNS Autoimmune Responses in BCMA-Deficient Mice Provide Insight for the Failure of Atacicept in MS

OBJECTIVE

B cells have emerged as a therapeutic target for MS. Anti-CD20 antibodies, which deplete B cells, are effective therapies for MS. However, atacicept (TACI-Fc), which blocks BAFF and APRIL and reduces B cells, unexpectedly exacerbates MS. We tested the hypothesis that B cell maturation antigen (BCMA), a receptor for BAFF and APRIL, plays a role in the paradoxical effects of anti-CD20 antibody and TACI-Fc using experimental autoimmune encephalomyelitis (EAE).

METHODS

EAE was induced in wild-type (BCMA^+/+) and BCMA-deficient (BCMA^-/-) mice with an immunization of rodent myelin oligodendrocyte glycoprotein (MOG)_35-55 peptide. Treatment with anti-CD20 antibody, TACI-Fc, and isotype controls was administered by intraperitoneal injections. CNS infiltration was evaluated by histology; immune cell phenotypes were evaluated by flow cytometry; MOG-specific antibodies were determined by ELISA. Mixed bone marrow chimeras and cell culture assays were used to identify the specific subsets of immune cells affected by BCMA deficiency.

RESULTS

First, we found that BCMA^-/- mice had more severe EAE compared with BCMA^+/+ mice and the increased disease was associated with elevated anti-MOG B-cell responses. Second, we found that anti-CD20 therapy attenuated EAE in BCMA^-/- mice but not in BCMA^+/+ mice. Third, TACI-Fc attenuated EAE in BCMA^+/+ mice but not in BCMA^-/- mice. Mixed bone marrow chimeric and cell culture experiments demonstrated that BCMA deficiency elevates inflammatory B-cell responses but inhibits inflammatory responses in macrophages.

CONCLUSIONS

BCMA has multifaceted roles during inflammation that affects therapeutic efficacies of anti-CD20 and TACI-Fc in EAE. Our results from BCMA-deficient mice provide insights into the failure of atacicept in MS.

Aberrant Expression of a Proliferation-Inducing Ligand Underlies Autoimmune Mechanisms in Immune Thrombocytopenia

Purpose

To study the relationship between surface membrane-bound APRIL and ITP.

Methods

The peripheral blood of all subjects, 50 patients diagnosed with ITP and 25 healthy controls, was collected. Flow cytometry was used to detect the expression of membrane-bound APRIL on immune cells and platelets. ELISA was used to detect the content of soluble APRIL in plasma.

Results

Membrane-bound APRIL was only expressed on the surface of platelets in both ITP patients and controls. APRIL expression on the platelet surface was significantly lower in newly diagnosed (P < 0.001) and chronic (P < 0.001) ITP patients than in controls. Platelet surface APRIL level was significantly enhanced in patients with complete remission after treatment (P = 0.02) but not in those with no response after treatment. Platelet surface APRIL level in ITP patients was negatively correlated with serum APRIL level (r = −0.09765, P = 0.0424).

Conclusions

Platelet surface APRIL may play a key immunoregulative role. Platelet surface APRIL is likely to be one source of the excessive serum APRIL in ITP patients. The effectiveness of treatment may be measured by determining the platelet surface APRIL levels in ITP patients.

B Cell-Activating Factor Promotes B Cell Survival in Ectopic Lymphoid Tissues in Nasal Polyps

Ectopic lymphoid tissues (eLTs) characterized by B cell aggregation contribute to the local immunoglobulin production in nasal polyps (NPs). B cell-activating factor (BAFF) is vital for B cell survival, proliferation, and maturation. The purpose of this study is to investigate whether BAFF is involved in the B cell survival and eLT formation in NPs. The mRNA and protein levels of BAFF in NP tissues with and without eLTs were detected by PCR and ELISA assay, respectively. The cellular sources of BAFF and active caspase-3-positive B cells in NPs were studied by immunofluorescence staining. B cells purified from NP tissues were stimulated with BAFF and were analyzed by flow cytometry. Stromal cells purified from NP tissues were stimulated with lymphotoxin (LT) α₁β_2, and BAFF levels in culture supernatants were analyzed by ELISA. Compared with those in control tissues and NPs without eLTs, the BAFF levels were elevated in NPs with eLTs. Abundant BAFF-positive cells and few active caspase-3-positive apoptotic B cells were found in NPs with eLTs, in contrast to those in NPs without eLTs. There was a negative correlation between the numbers of BAFF-positive cells and frequencies of apoptotic B cells in total B cells in NP tissues. BAFF protected nasal polyp B cells from apoptosis in vitro. Stromal cells were an important cellular source of BAFF in NPs with eLTs. LTα₁β₂ induced BAFF production from nasal stromal cells in vitro. We propose that BAFF contribute to eLT formation in NPs by promoting B cell survival.

Gene Modified CAR-T Cellular Therapy for Hematologic Malignancies

With advances in the understanding of characteristics of molecules, specific antigens on the surface of hematological malignant cells were identified and multiple therapies targeting these antigens as neoplasm treatments were developed. Among them, chimeric antigen receptor (CAR) T-cell therapy, which got United States Food and Drug Administration (FDA) approval for relapsed/refractory (r/r) diffuse large B-cell lymphoma (DLBCL) as well as for recurrent acute lymphoblastic leukemia (ALL) within the past five years, and for r/r mantle cell lymphoma (MCL) this year, represents one of the most rapidly evolving immunotherapies. Nevertheless, its applicability to other hematological malignancies, as well as its efficacy and persistence are fraught with clinical challenges. Currently, more than one thousand clinical trials in CAR T-cell therapy are ongoing and its development is changing rapidly. This review introduces the current status of CAR T-cell therapy in terms of the basic molecular aspects of CAR T-cell therapy, its application in hematological malignancies, adverse reactions during clinical use, remaining challenges, and future utilization.

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.

BCMA-targeting approaches for treatment of multiple myeloma

Recent advances in treatment modalities have led to improved survival in patients with multiple myeloma (MM). However, despite these, MM remains an incurable disease. Many MM patients relapse through and become refractory to current treatment strategies or are intolerant due to toxicities arising from therapy. As such, novel strategies addressing new targets are crucial in improving care for MM patients. BCMA has emerged as a rationale therapeutic target for treatment of MM as it is preferentially expressed in mature B-lymphocytes and plasma cells with the overexpression and activation of BCMA via its ligands associated with the disease progression in multiple myeloma. Given the high expression of BCMA in malignant Plasma cells compared to those from normal healthy volunteers, targeting BCMA should reduce risks of on-target off-tumor toxicities. The main BCMA-targeting approaches currently used for treatment of MM include: 1) chimeric antigen receptor (CAR) T-cell therapy; 2) bi- and multi- specific antibodies; and 3) monoclonal antibodies and their drug conjugates. This review will outline these therapeutic agents and present their emerging clinical data.

BCMA-targeted immunotherapy for multiple myeloma

B cell maturation antigen (BCMA) is a novel treatment target for multiple myeloma (MM) due to its highly selective expression in malignant plasma cells (PCs). Multiple BCMA-targeted therapeutics, including antibody-drug conjugates (ADC), chimeric antigen receptor (CAR)-T cells, and bispecific T cell engagers (BiTE), have achieved remarkable clinical response in patients with relapsed and refractory MM. Belantamab mafodotin-blmf (GSK2857916), a BCMA-targeted ADC, has just been approved for highly refractory MM. In this article, we summarized the molecular and physiological properties of BCMA as well as BCMA-targeted immunotherapeutic agents in different stages of clinical development.

Characterization of CD19+ CD24hi CD38hi B cells in Chinese adult patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease. Human interleukin-10⁺ B cells (B10 cells) is one of regulatory B cells and is enriched in CD19⁺ CD24^hi CD38^hi B cells. A little is known about these cells in atopic dermatitis.

OBJECTIVE

To study CD19⁺ CD24^hi CD38^hi B cells and their clinical significance in Chinese adult patients with atopic dermatitis.

METHODS

Thirty-two adult patients with AD and nineteen healthy controls were enrolled. Peripheral blood mononuclear cells (PBMCs) were isolated and stained with fluorescein-conjugated monoclonal antibodies for CD19, CD24, CD27, CD38 and Annexin V. The stained PBMCs were analysed by flow cytometry. B10 cells were prepared by stimulating PBMCs with CpG, LPS and CD40L followed by restimulation with phorbol12-myristate 13-acetate (PMA) and ionomycin. Serum IL-10, B-cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) levels were measured by using the ELISA. Apoptosis and proliferation of CD19⁺ CD24^hi CD38^hi B cells were measured by flow cytometry. 4/P-signal transducer and activator of transcription 3 (STAT3) and extracellular signal-regulated kinase 1/2 (Erk) phosphorylation were also studied.

RESULTS

The number of CD19⁺ CD24^hi CD38^hi B cells in patients with AD was similar to that in healthy controls. However, B10 cells were decreased in patients with AD. The proportion of B10 cells was negatively associated with blood basophil counts but not associated with disease activity. CD19⁺ CD24^hi CD38^hi B cells from AD patients were more susceptible to apoptosis upon stimulation with CpG, LPS and CD40L. B cells from AD patients showed lower STAT3 and Erk phosphorylation.

CONCLUSIONS

CD19⁺ CD24^hi CD38^hi B cells were unchanged in atopic dermatitis while B10 cells were decreased. The increased B-cell apoptosis, decreased STAT3 and Erk phosphorylation might contribute to these changes.

BCMA-Targeting Therapy: Driving a New Era of Immunotherapy in Multiple Myeloma

The treatment of multiple myeloma (MM) has entered into a new era of immunotherapy. Novel immunotherapies will significantly improve patient outcome via simultaneously targeting malignant plasma cell (PC) and reversing immunocompromised bone marrow (BM) microenvironment. B-cell maturation antigen (BCMA), selectively expressed in PCs and a key receptor for A proliferation-inducing ligand (APRIL), is highly expressed in MM cells from patients at all stages. The APRIL/BCMA signal cascades promote the survival and drug resistance of MM cells and further modulate immunosuppressive BM milieu. Impressively, anti-BCMA immunotherapeutic reagents, including chimeric antigen receptor (CAR), antibody-drug conjugate (ADC) and bispecific T cell engager (BiTE) have all shown high response rates in their first clinical trials in relapse and refractory patients with very limited treatment options. These results rapidly inspired numerous development of next-generation anti-BCMA biotherapeutics, i.e., bispecific molecule, bispecific or trispecific antibodies, a novel form of CAR T/NK cells and T Cell Antigen Coupler (TAC) receptors, antibody-coupled T cell receptor (ACTR) as well as a cancer vaccine. We here highlight seminal preclinical and clinical studies on novel BCMA-based immunotherapies as effective monotherapy and discuss their potential in combination with current anti-MM and novel checkpoint drugs in earlier disease stages to further achieve durable responses in patients.

Transmembrane Activator and CAML Interactor (TACI): Another Potential Target for Immunotherapy of Multiple Myeloma?

Multiple myeloma (MM) has emerged as the next most likely oncological or hematological disease indication amenable for cellular immunotherapy. Much of the attention has been focused on B cell maturation antigen (BCMA) as a unique cell surface protein on myeloma cells that is available for monoclonal antibodies, antibody drug conjugates (ADCs), T-cell redirecting bispecific molecules, and chimeric antigen receptor (CAR) T cell targeting. BCMA is a member of the tumor necrosis factor receptor (TNFR) superfamily that binds two ligands B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) and mediates the growth and survival of plasma and MM cells. Interestingly, transmembrane activator and CAML interactor (TACI), another TNFR superfamily member, also binds the same ligands and plays largely overlapping roles as BCMA in normal plasma and malignant MM cells. In this article, we review the biology of TACI, focusing on its role in normal B and plasma cells and malignant MM cells, and also discuss various ways to incorporate TACI as a potential target for immunotherapies against MM.

An Essential Role for Perforin-2 in Type I IFN Signaling

Type I IFNs play a complex role in determining the fate of microbial pathogens and may also be deleterious to the host during bacterial and viral infections. Upon ligand binding, a receptor proximal complex consisting of IFN-α and -β receptors 1 and 2 (IFNAR1, IFNAR2, respectively), tyrosine kinase 2 (Tyk2), Jak1, and STAT2 are assembled and promote the phosphorylation of STAT1 and STAT2. However, how the IFNARs proximal complex is assembled upon binding to IFN is poorly understood. In this study, we show that the membrane-associated pore-forming protein Perforin-2 (P2) is critical for LPS-induced endotoxic shock in wild-type mice. Type I IFN-mediated JAK-STAT signaling is severely impaired, and activation of MAPKs and PI3K signaling pathways are delayed in P2-deficient mouse bone marrow-derived macrophages, mouse embryonic fibroblasts (MEFs), and human HeLa cells upon IFN stimulation. The P2 N-glycosylated extracellular membrane attack complex/perforin domain and the P2 domain independently associate with the extracellular regions of IFNAR1 and IFNAR2, respectively, in resting MEFs. In addition, the P2 cytoplasmic tail domain mediated the constitutive interaction between STAT2 and IFNAR2 in resting MEFs, an interaction that is dependent on the association of the extracellular regions of P2 and IFNAR2. Finally, the constitutive association of P2 with both receptors and STAT2 is critical for the receptor proximal complex assembly and reciprocal transphosphorylation of Jak1 and Tyk2 as well as the phosphorylation and activation of STAT1 and STAT2 upon IFN-β stimulation.

Limited treatment options in refractory multiple myeloma: promising therapeutic developments

Introduction: Combinations of proteasome inhibitors, immunomodulators, and monoclonal antibodies are highly active against multiple myeloma. Consequently, several combinations have moved from the relapsed to the front-line setting. In the context of lenalidomide and bortezomib being used upfront, salvage options need to be evaluated.Areas covered: This manuscript reviews available data for the treatment of patients progressing on optimal frontline strategies, with a focus on the role of second-generation proteasome inhibitors and immunomodulators, monoclonal antibodies and immunotherapy.Expert opinion: Remarkable progress has been made in myeloma treatment due to the integration of immunomodulators, proteasome inhibitors and more recently monoclonal antibodies in the front-line setting. However, we work on the assumption that most individuals will eventually relapse. Optimized upfront therapy negatively selects more resistant patients among still relapsing individuals. Bortezomib and lenalidomide-exposed patients are under-represented in trials leading to currently approved combinations. Evidence needs to be reviewed taking into account how the improvement of frontline therapy has modified the characteristics of patients at the time of relapse. Second generation immunomodulatory agents and proteasome inhibitors, monoclonal antibodies and other agents have shown efficacy in this new landscape. Immunotherapeutic agents, including CAR-T cells are promising for patients failing standard combinations, despite current data are still immature.

Ancient BCMA-like Genes Herald B Cell Regulation in Lampreys

The TNF superfamily ligands BAFF and APRIL interact with three receptors, BAFFR, BCMA, and TACI, to play discrete and crucial roles in regulating B cell selection and homeostasis in mammals. The interactions between these ligands and receptors are both specific and redundant: BAFFR binds BAFF, whereas BCMA and TACI bind to either BAFF or APRIL. In a previous phylogenetic inquiry, we identified and characterized a BAFF-like gene in lampreys, which, with hagfish, are the only extant jawless vertebrates, both of which have B-like and T-like lymphocytes. To gain insight into lymphocyte regulation in jawless vertebrates, in this study we identified two BCMA-like genes in lampreys, BCMAL1 and BCMAL2, which were found to be preferentially expressed by B-like lymphocytes. In vitro analyses indicated that the lamprey BAFF-like protein can bind to a BCMA-like receptor Ig fusion protein and to both BCMAL1- and BCMAL2-transfected cells. Discriminating regulatory roles for the two BCMA-like molecules are suggested by their differential expression before and after activation of the B-like lymphocytes in lampreys. Our composite results imply that BAFF-based mechanisms for B cell regulation evolved before the divergence of jawed and jawless vertebrates.

Molecular structure, expression, and bioactivity of B-cell-activating factor of the TNF family (BAFF) and its receptor BAFF-R in cats (Felis catus)

B-cell survival depends on signals induced by binding of B-cell activating factor (BAFF) to its receptor (BAFF-R). In this study, the full-length cDNAs of cat BAFF (cBAFF) and BAFF-R (cBAFF-R) were amplified from the spleen by reverse transcription PCR. The open reading frame of cBAFF cDNA encodes a protein of 285 amino acids containing a predicted transmembrane domain and a furin protease cleavage site, similar to mammalian, avian, and reptile BAFFs. The cBAFF-R gene encodes a 189 amino acid protein. Real-time quantitative PCR analyses revealed that the two genes are predominantly expressed in the spleen. csBAFF, EGFP/csBAFF, and cBAFF-R were efficiently expressed in Escherichia coli BL21 (DE3), as confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting analyses. After purification, the EGFP/csBAFF fusion protein showed a fluorescence spectrum similar to that of EGFP. Confocal laser scanning microscopy showed that EGFP/csBAFF bound to its receptor. In vitro, csBAFF promoted the survival of cat and mouse splenic B cells with/without a priming agent (Staphylococcus aureus Cowan 1, SAC) or anti-mouse IgM. Furthermore, it stimulated the survival of mouse B cells, similar to msBAFF. Recombinant cBAFF-R blocked the function of sBAFF in vitro. These findings indicate that csBAFF plays an important role in the survival of cat B cells and has functional cross reactivity between cats and other mammals, and suggest a role for the BAFF-BAFF-R system in regulating B-cell survival. Therefore, BAFF and BAFF-R show promise for enhancing the immune systems of animals.

The role of BAFF and APRIL in rheumatoid arthritis

Development and activation of B cells quickly became clear after identifying new ligands and receptors in the tumor necrosis factor superfamily. B cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are the members of membrane proteins Type 2 family released by proteolytic cleavage of furin to form active, soluble homotrimers. Except for B cells, ligands are expressed by all such immune cells like T cells, dendritic cells, monocytes, and macrophages. BAFF and APRIL have two common receptors, namely TNFR homolog transmembrane activator and Ca2+ modulator and CAML interactor (TACI) and B cell-maturation antigen. BAFF alone can also be coupled with a third receptor called BAFFR (also called BR3 or BLyS Receptor). These receptors are often expressed by immune cells in the B-cell lineage. The binding of BAFF or APRIL to their receptors supports B cells differentiation and proliferation, immunoglobulin production and the upregulation of B cell-effector molecules expression. It is possible that the overexpression of BAFF and APRIL contributes to the pathogenesis of autoimmune diseases. In BAFF transgenic mice, there is a pseudo-autoimmune manifestation, which is associated with an increase in B-lymphocytes, hyperglobulinemia, anti-single stranded DNA, and anti-double-stranded DNA antibodies, and immune complexes in their peripheral blood. Furthermore, overexpressing BAFF augments the number of peripheral B220+ B cells with a normal proliferation rate, high levels of Bcl2, and prolonged survival and hyperactivity. Therefore, in this review article, we studied BAFF and APRIL as important mediators in B-cell and discussed their role in rheumatoid arthritis.