IFN-β treatment requires B cells for efficacy in neuroautoimmunity

Human regulatory memory B cells defined by expression of TIM-1 and TIGIT are dysfunctional in multiple sclerosis

Background

Regulatory B cells (Bregs) play a pivotal role in suppressing immune responses, yet there is still a lack of cell surface markers that can rigorously identify them. In mouse models for multiple sclerosis (MS), TIM-1 or TIGIT expression on B cells is required for maintaining self-tolerance and regulating autoimmunity to the central nervous system. Here we investigated the activities of human memory B cells that differentially express TIM-1 and TIGIT to determine their potential regulatory function in healthy donors and patients with relapsing-remitting (RR) MS.

Methods

FACS-sorted TIM-1+/-TIGIT+/- memory B (memB) cells co-cultured with allogenic CD4+ T cells were analyzed for proliferation and induction of inflammatory markers using flow cytometry and cytokine quantification, to determine Th1/Th17 cell differentiation. Transcriptional differences were assessed by SMARTSeq2 RNA sequencing analysis.

Results

TIM-1-TIGIT- double negative (DN) memB cells strongly induce T cell proliferation and pro-inflammatory cytokine expression. The TIM-1+ memB cells enabled low levels of CD4+ T cell activation and gave rise to T cells that co-express IL-10 with IFNγ and IL-17A or FoxP3. T cells cultured with the TIM-1+TIGIT+ double positive (DP) memB cells exhibited reduced proliferation and IFNγ, IL-17A, TNFα, and GM-CSF expression, and exhibited strong regulation in Breg suppression assays. The functional activity suggests the DP memB cells are a bonafide Breg population. However, MS DP memB cells were less inhibitory than HC DP memB cells. A retrospective longitudinal study of anti-CD20 treated patients found that post-treatment DP memB cell frequency and absolute number were associated with response to therapy. Transcriptomic analyses indicated that the dysfunctional MS-derived DP memB/Breg population exhibited increased expression of genes associated with T cell activation and survival (CD80, ZNF10, PIK3CA), and had distinct gene expression compared to the TIGIT+ or TIM-1+ memB cells.

Conclusion

These findings demonstrate that TIM-1/TIGIT expressing memory B cell subsets have distinct functionalities. Co-expression of TIM-1 and TIGIT defines a regulatory memory B cell subset that is functionally impaired in MS.

Therapeutic targeting of gut-originating regulatory B cells in neuroinflammatory diseases

Regulatory B cells (Bregs) are immunosuppressive cells that support immunological tolerance by the production of IL-10, IL-35, and TGF-β. Bregs arise from different developmental stages in response to inflammatory stimuli. In that regard, mounting evidence points towards a direct influence of gut microbiota on mucosal B cell development, activation, and regulation in health and disease. While an increasing number of diseases are associated with alterations in gut microbiome (dysbiosis), little is known about the role of microbiota on Breg development and induction in neuroinflammatory disorders. Notably, gut-originating, IL-10- and IgA-producing regulatory plasma cells have recently been demonstrated to egress from the gut to suppress inflammation in the CNS raising fundamental questions about the triggers and functions of mucosal-originating Bregs in systemic inflammation. Advancing our understanding of Bregs in neuroinflammatory diseases could lead to novel therapeutic approaches. Here, we summarize the main aspects of Breg differentiation and functions and evidence about their involvement in neuroinflammatory diseases. Further, we highlight current data of gut-originating Bregs and their microbial interactions and discuss future microbiota-regulatory B cell-targeted therapies in immune-mediated diseases.

Under the influence: environmental factors as modulators of neuroinflammation through the IL-10/IL-10R axis

The IL-10/IL-10 receptor (IL-10R) axis plays an important role in attenuating neuroinflammation in animal models of Multiple Sclerosis (MS) and increased IL-10 has been associated with a positive response to MS disease modifying therapy. Because environmental factors play an important role in MS susceptibility and disease course, identification of environmental factors that impact the IL-10/IL-10R axis has therapeutic potential. In this review, we provide historical and updated perspectives of how IL-10R signaling impacts neuroinflammation, discuss environmental factors and intestinal microbes with known impacts on the IL-10/IL-10R axis, and provide a hypothetical model for how B cells, via their production of IL-10, may be important in conveying environmental "information" to the inflamed central nervous system.

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.

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.

The emerging role of regulatory cell-based therapy in autoimmune disease

Autoimmune disease, caused by unwanted immune responses to self-antigens, affects millions of people each year and poses a great social and economic burden to individuals and communities. In the course of autoimmune disorders, including rheumatoid arthritis, systemic lupus erythematosus, type 1 diabetes mellitus, and multiple sclerosis, disturbances in the balance between the immune response against harmful agents and tolerance towards self-antigens lead to an immune response against self-tissues. In recent years, various regulatory immune cells have been identified. Disruptions in the quality, quantity, and function of these cells have been implicated in autoimmune disease development. Therefore, targeting or engineering these cells is a promising therapeutic for different autoimmune diseases. Regulatory T cells, regulatory B cells, regulatory dendritic cells, myeloid suppressor cells, and some subsets of innate lymphoid cells are arising as important players among this class of cells. Here, we review the roles of each suppressive cell type in the immune system during homeostasis and in the development of autoimmunity. Moreover, we discuss the current and future therapeutic potential of each one of these cell types for autoimmune diseases.

Targeting CD38 in Neoplasms and Non-Cancer Diseases

Simple Summary

CD38 remains an interesting target for anticancer therapy. Its relatively high abundance in neoplasms and crucial impact on NAD+/cADPR metabolism and the activity of T cells allows for changing the immune response in autoimmune diseases, neoplasms, and finally the induction of cell death. Antibody-dependent cell cytotoxicity is responsible for cell death induced by targeting the tumor with anti-CD38 antibodies, such as daratumumab. A wide range of laboratory experiments and clinical trials show an especially promising role of anti-CD38 therapy against multiple myeloma, NK cell lymphomas, and CD19- B-cell malignancies. More studies are required to include more diseases in the therapeutic protocols involving the modulation of CD38 activity.

Abstract

CD38 is a myeloid antigen present both on the cell membrane and in the intracellular compartment of the cell. Its occurrence is often enhanced in cancer cells, thus making it a potential target in anticancer therapy. Daratumumab and isatuximab already received FDA approval, and novel agents such as MOR202, TAK079 and TNB-738 undergo clinical trials. Also, novel therapeutics such as SAR442085 aim to outrank the older antibodies against CD38. Multiple myeloma and immunoglobulin light-chain amyloidosis may be effectively treated with anti-CD38 immunotherapy. Its role in other hematological malignancies is also important concerning both diagnostic process and potential treatment in the future. Aside from the hematological malignancies, CD38 remains a potential target in gastrointestinal, neurological and pulmonary system disorders. Due to the strong interaction of CD38 with TCR and CD16 on T cells, it may also serve as the biomarker in transplant rejection in renal transplant patients. Besides, CD38 finds its role outside oncology in systemic lupus erythematosus and collagen-induced arthritis. CD38 plays an important role in viral infections, including AIDS and COVID-19. Most of the undergoing clinical trials focus on the use of anti-CD38 antibodies in the therapy of multiple myeloma, CD19- B-cell malignancies, and NK cell lymphomas. This review focuses on targeting CD38 in cancer and non-cancerous diseases using antibodies, cell-based therapies and CD38 inhibitors. We also provide a summary of current clinical trials targeting CD38.

Longitudinal analysis of anti-drug antibody development in multiple sclerosis patients treated with interferon beta-1a (Rebif™) using B cell receptor repertoire analysis

A significant proportion of multiple sclerosis (MS) patients treated with interferon beta-1a (Rebif™) develop anti-drug antibodies (ADA) with a negative impact on treatment efficacy. We hypothesized that high-throughput B-cell receptor (BCR) repertoire analysis could be used to predict and monitor ADA development. To study this we analyzed 228 peripheral blood samples from 68 longitudinally followed patients starting on interferon beta-1a. Our results show that whole blood BCR analysis does not reflect, and does not predict ADA development in MS patients treated with interferon beta-1a. We propose that BCR analysis of phenotypically selected cell subsets or tissues might be more informative.

Intrahepatic transcriptomics reveals gene signatures in chronic hepatitis B patients responded to interferon therapy

Chronic hepatitis B virus (HBV) infection remains a substantial public health burden worldwide. Alpha-interferon (IFNα) is one of the two currently approved therapies for chronic hepatitis B (CHB), to explore the mechanisms underlying IFNα treatment response, we investigated baseline and 24-week on-treatment intrahepatic gene expression profiles in 21 CHB patients by mRNA-seq. The data analyses demonstrated that PegIFNα treatment significantly induced antiviral responses. Responders who achieved HBV DNA loss and HBeAg or HBsAg seroconversion displayed higher fold change and larger number of up-regulated interferon-stimulated genes (ISGs). Interestingly, lower expression levels of certain ISGs were observed in responders in their baseline biopsy samples. In HBeAg+ patients, non-responders had relative higher baseline HBeAg levels than responders. More importantly, HBeAg− patients showed higher HBsAg loss rate than HBeAg+ patients. Although a greater fold change of ISGs was observed in HBeAg− patients than HBeAg+ patients, upregulation of ISGs in HBeAg+ responders exceeded HBeAg− responders. Notably, PegIFNα treatment increased monocyte and mast cell infiltration, but decreased CD8 T cell and M1 macrophage infiltration in both responders and non-responders, while B cell infiltration was increased only in responders. Moreover, co-expression analysis identified ribosomal proteins as critical players in antiviral response. The data also indicate that IFNα may influence the production of viral antigens associated with endoplasmic reticulum. Collectively, the intrahepatic transcriptome analyses in this study enriched our understanding of IFN-mediated antiviral effects in CHB patients and provided novel insights into the development of potential strategies to improve IFNα therapy.

Activation pathways that drive CD4+ T cells to break tolerance in autoimmune diseases. Immunol Rev 2022;307:161-190. [PMID: 35142369 PMCID: PMC9255211 DOI: 10.1111/imr.13071]

Autoimmune diseases are characterized by dysfunctional immune systems that misrecognize self as non-self and cause tissue destruction. Several cell types have been implicated in triggering and sustaining disease. Due to a strong association of major histocompatibility complex II (MHC-II) proteins with various autoimmune diseases, CD4+ T lymphocytes have been thoroughly investigated for their roles in dictating disease course. CD4+ T cell activation is a coordinated process that requires three distinct signals: Signal 1, which is mediated by antigen recognition on MHC-II molecules; Signal 2, which boosts signal 1 in a costimulatory manner; and Signal 3, which helps to differentiate the activated cells into functionally relevant subsets. These signals are disrupted during autoimmunity and prompt CD4+ T cells to break tolerance. Herein, we review our current understanding of how each of the three signals plays a role in three different autoimmune diseases and highlight the genetic polymorphisms that predispose individuals to autoimmunity. We also discuss the drawbacks of existing therapies and how they can be addressed to achieve lasting tolerance in patients.

Targeting IFN activity to both B cells and plasmacytoid dendritic cells induces a robust tolerogenic response and protection against EAE

Type I Interferon (IFN) was the very first drug approved for the treatment of Multiple Sclerosis (MS), and is still frequently used as a first line therapy. However, systemic IFN also causes considerable side effects, affecting therapy adherence and dose escalation. In addition, the mechanism of action of IFN in MS is multifactorial and still not completely understood. Using AcTaferons (Activity-on-Target IFNs, AFNs), optimized IFN-based immunocytokines that allow cell-specific targeting, we have previously demonstrated that specific targeting of IFN activity to dendritic cells (DCs) can protect against experimental autoimmune encephalitis (EAE), inducing in vivo tolerogenic protective effects, evidenced by increased indoleamine-2,3-dioxygenase (IDO) and transforming growth factor β (TGFβ) release by plasmacytoid (p) DCs and improved immunosuppressive capacity of regulatory T and B cells. We here report that targeting type I IFN activity specifically towards B cells also provides strong protection against EAE, and that targeting pDCs using SiglecH-AFN can significantly add to this protective effect. The superior protection achieved by simultaneous targeting of both B lymphocytes and pDCs correlated with improved IL-10 responses in B cells and conventional cDCs, and with a previously unseen very robust IDO response in several cells, including all B and T lymphocytes, cDC1 and cDC2.

Headache in multiple sclerosis - pharmacological aspects

For decades, headache was not considered a typical symptom of multiple sclerosis (MS) and was construed as a "red flag" for important differential diagnoses such as cerebral vasculitis. Meanwhile, several studies have demonstrated an increased prevalence of headache in MS compared to the general population. This is due to the heterogeneity of headache genesis with frequent occurrence of both primary and secondary headaches in MS. On the one hand, MS and migraine are often comorbid. On the other hand, secondary headaches occur frequently, especially in the course of MS relapses. These are often migraine-like headaches caused by inflammation, which can improve as a result of MS-specific therapy. Headaches are particularly common in the early stages of chronic inflammatory CNS disease, where inflammatory activity is greatest. In addition, headache can also occur as a side effect of disease-modifying drugs (DMDs). Headache can occur with most DMDs and is most frequently described with interferon-beta therapy. The aim of this work is to present the prevalence of headache and describe the heterogeneity of possible causes of headache in MS. In addition, important therapeutic aspects in the treatment of MS patients in general will be presented as well as different approaches to the treatment of headache in MS depending on the etiological classification.

B-cell depletion therapy for multiple sclerosis

Since the initial observation of increased immunoglobulin concentrations in the cerebrospinal fluid of multiple sclerosis (MS) patients in the 1940s, B cells have been considered to participate in the pathology of MS through the production of autoantibodies reactive against central nervous system antigens. However, it is now recognized that B cells contribute to MS relapses via antibody-independent activities, including the presentation of antigens to T cells and the release of pro-inflammatory cytokines. In addition, the recent identification of B cell-rich follicle-like structures in the meninges of progressive MS patients suggests that the pathogenic roles of B cells also exist at the progressive phase of this disease. Recently, large-scale clinical trials have demonstrated the efficacy of B-cell depletion therapy using anti-CD20 antibodies in relapsing as well as primary progressive MS. B-cell depletion therapy has become an essential treatment option for MS based on its unique benefit to risk balance in relapsing MS, and because it is the only drug that has been shown to be effective in primary progressive MS to date.

Current and Future Immunotherapies for Multiple Sclerosis

Despite substantial progress in developing new immunotherapies against multiple sclerosis (MS), currently available immunotherapies are only partially effective for this debilitating neurological disease, thus necessitating new therapeutic approaches. Here, we review the immunotherapies already approved for MS as well as relevant clinical trials. Further, we present some experimental approaches that are currently being developed and are focused on modulating the functions of dendritic cells and regulatory T cells.

Memory B Cells in Multiple Sclerosis: Emerging Players in Disease Pathogenesis

Multiple Sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. Once thought to be primarily driven by T cells, B cells are emerging as central players in MS immunopathogenesis. Interest in multiple B cell phenotypes in MS expanded following the efficacy of B cell-depleting agents targeting CD20 in relapsing-remitting MS and inflammatory primary progressive MS patients. Interestingly, these therapies primarily target non-antibody secreting cells. Emerging studies seek to explore B cell functions beyond antibody-mediated roles, including cytokine production, antigen presentation, and ectopic follicle-like aggregate formation. Importantly, memory B cells (Bmem) are rising as a key B cell phenotype to investigate in MS due to their antigen-experience, increased lifespan, and rapid response to stimulation. Bmem display diverse effector functions including cytokine production, antigen presentation, and serving as antigen-experienced precursors to antibody-secreting cells. In this review, we explore the cellular and molecular processes involved in Bmem development, Bmem phenotypes, and effector functions. We then examine how these concepts may be applied to the potential role(s) of Bmem in MS pathogenesis. We investigate Bmem both within the periphery and inside the CNS compartment, focusing on Bmem phenotypes and proposed functions in MS and its animal models. Finally, we review how current immunomodulatory therapies, including B cell-directed therapies and other immunomodulatory therapies, modify Bmem and how this knowledge may be harnessed to direct therapeutic strategies in MS.

The Role of B Cells in Primary Progressive Multiple Sclerosis

The success of ocrelizumab in reducing confirmed disability accumulation in primary progressive multiple sclerosis (PPMS) via CD20-targeted depletion implicates B cells as causal agents in the pathogenesis of PPMS. This review explores the possible mechanisms by which B cells contribute to disease progression in PPMS, specifically exploring cytokine production, antigen presentation, and antibody synthesis. B cells may contribute to disease progression in PPMS through cytokine production, specifically GM-CSF and IL-6, which can drive naïve T-cell differentiation into pro-inflammatory Th1/Th17 cells. B cell production of the cytokine LT-α may induce follicular dendritic cell production of CXCL13 and lead indirectly to T and B cell infiltration into the CNS. In contrast, production of IL-10 by B cells likely induces an anti-inflammatory effect that may play a role in reducing neuroinflammation in PPMS. Therefore, reduced production of IL-10 may contribute to disease worsening. B cells are also capable of potent antigen presentation and may induce pro-inflammatory T-cell differentiation via cognate interactions. B cells may also contribute to disease activity via antibody synthesis, although it's unlikely the benefit of ocrelizumab in PPMS occurs via antibody decrement. Finally, various B cell subsets likely promulgate pro- or anti-inflammatory effects in MS.

Inflammation in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) that is characterised pathologically by demyelination, gliosis, neuro-axonal damage and inflammation. Despite intense research, the underlying pathomechanisms driving inflammatory demyelination in MS still remain incompletely understood. It is thought to be caused by an autoimmune response towards CNS self-antigens in genetically susceptible individuals, assuming autoreactive T cells as disease-initiating immune cells. Yet, B cells were recognized as crucial immune cells in disease pathology, including antibody-dependent and independent effects. Moreover, myeloid cells are important contributors to MS pathology, and it is becoming increasingly evident that different cell types act in concert during MS immunopathology. This is supported by the finding that the beneficial effects of actual existing disease-modifying therapies cannot be attributed to one single immune cell-type, but rather involve immunological cooperation. The current strategy of MS therapies thus aims to shift the immune cell repertoire from a pro-inflammatory towards an anti-inflammatory phenotype, involving regulatory T and B cells and anti-inflammatory macrophages. Although no existing therapy actually exists that directly induces an enhanced regulatory immune cell pool, numerous studies identified potential net effects on these cell types. This review gives a conceptual overview on T cells, B cells and myeloid cells in the immunopathology of relapsing-remitting MS and discusses potential contributions of actual disease-modifying therapies on these immune cell phenotypes.

Regulatory B cells in respiratory health and diseases

B cells are critical mediators of humoral immune responses in the airways through antibody production, antigen presentation, and cytokine secretion. In addition, a subset of B cells, known as regulatory B cells (Bregs), exhibit immunosuppressive functions via diverse regulatory mechanisms. Bregs modulate immune responses via the secretion of IL‐10, IL‐35, and tumor growth factor‐β (TGF‐β), and by direct cell contact. The balance between effector and regulatory B cell functions is critical in the maintenance of immune homeostasis. The importance of Bregs in airway immune responses is emphasized by the different respiratory disorders associated with abnormalities in Breg numbers and function. In this review, we summarize the role of immunosuppressive Bregs in airway inflammatory diseases and highlight the importance of this subset in the maintenance of respiratory health. We propose that improved understanding of signals in the lung microenvironment that drive Breg differentiation can provide novel therapeutic avenues for improved management of respiratory diseases.

Fingolimod Profoundly Reduces Frequencies and Alters Subset Composition of Circulating T Follicular Helper Cells in Multiple Sclerosis Patients

Fingolimod is an effective treatment for relapsing-remitting multiple sclerosis. It is well established that fingolimod, a modulator of the sphingosine-1-phosphate pathway, restrains the egress of CCR7⁺ lymphocytes from lymphatic tissues into the blood, thus resulting in reduced lymphocyte counts in peripheral blood. CXCR5⁺ T follicular helper (Tfh) cells provide help to B cells, are essential for the generation of potent Ab responses, and have been shown to be critically involved in the pathogenesis of several autoimmune diseases. Besides lymphoid tissue-resident Tfh cells, CXCR5⁺ circulating Tfh (cTfh) cells have been described in the blood, their numbers correlating with the magnitude of Tfh cells in lymphoid tissues. Although the effect of fingolimod on circulating lymphocyte subsets has been established, its effect on cTfh cells remains poorly understood. In this study, we found that although fingolimod strongly and disproportionally reduced cTfh cell frequencies, frequencies of activated cTfh cells were increased, and the composition of the cTfh cell pool was skewed toward a cTfh1 cell phenotype. The circulating T follicular regulatory cell subset and CXCR5⁺ CD8⁺ T cell frequencies were also strongly and disproportionally decreased after fingolimod treatment. In contrast, relative frequencies of CXCR5^- memory Th cells as well as regulatory T and B cells were increased. In summary, these data provide new insights into fingolimod-induced compositional changes of lymphocyte populations in the blood, in particular cTfh cells, and thus contribute to a better understanding of the mechanism of action of fingolimod in multiple sclerosis patients.

Regulatory B Cells and Its Role in Central Nervous System Inflammatory Demyelinating Diseases

Regulatory B (Breg) cells represent a population of suppressor B cells that participate in immunomodulatory processes and inhibition of excessive inflammation. The regulatory function of Breg cells have been demonstrated in mice and human with inflammatory diseases, cancer, after transplantation, and particularly in autoinflammatory disorders. In order to suppress inflammation, Breg cells produce anti-inflammatory mediators, induce death ligand-mediated apoptosis, and regulate many kinds of immune cells such as suppressing the proliferation and differentiation of effector T cell and increasing the number of regulatory T cells. Central nervous system Inflammatory demyelinating diseases (CNS IDDs) are a heterogeneous group of disorders, which occur against the background of an acute or chronic inflammatory process. With the advent of monoclonal antibodies directed against B cells, breakthroughs have been made in the treatment of CNS IDDs. Therefore, the number and function of B cells in IDDs have attracted attention. Meanwhile, increasing number of studies have confirmed that Breg cells play a role in alleviating autoimmune diseases, and treatment with Breg cells has also been proposed as a new therapeutic direction. In this review, we focus on the understanding of the development and function of Breg cells and on the diversification of Breg cells in CNS IDDs.

Differential Effects of MS Therapeutics on B Cells-Implications for Their Use and Failure in AQP4-Positive NMOSD Patients

B cells are considered major contributors to multiple sclerosis (MS) pathophysiology. While lately approved disease-modifying drugs like ocrelizumab deplete B cells directly, most MS medications were not primarily designed to target B cells. Here, we review the current understanding how approved MS medications affect peripheral B lymphocytes in humans. These highly contrasting effects are of substantial importance when considering these drugs as therapy for neuromyelitis optica spectrum disorders (NMOSD), a frequent differential diagnosis to MS, which is considered being a primarily B cell- and antibody-driven diseases. Data indicates that MS medications, which deplete B cells or induce an anti-inflammatory phenotype of the remaining ones, were effective and safe in aquaporin-4 antibody positive NMOSD. In contrast, drugs such as natalizumab and interferon-β, which lead to activation and accumulation of B cells in the peripheral blood, lack efficacy or even induce catastrophic disease activity in NMOSD. Hence, we conclude that the differential effect of MS drugs on B cells is one potential parameter determining the therapeutic efficacy or failure in antibody-dependent diseases like seropositive NMOSD.

Impact of cytomegalovirus infection on B cell differentiation and cytokine production in multiple sclerosis

Background

Human cytomegalovirus (HCMV) infection has been recently associated with a low risk of multiple sclerosis (MS), yet the basis behind this observation remains uncertain. In this study, we aimed to determine in MS patients whether HCMV induces modifications in the peripheral B cell compartment.

Methods

HCMV serostatus was determined in 73 MS patients (55 relapsing-remitting MS (RRMS); 18 progressive MS (PMS)) and 30 healthy controls, assessing their B cell immunophenotype and cytokine production (GM-CSF, IL-6, IL-10, and TNFα) by flow cytometry.

Results

HCMV seropositivity in untreated MS patients (n = 45) was associated with reduced switched memory B cells, contrasting with an opposite effect in PMS. Expansions of transitional B cells were observed in HCMV(+) IFNβ-treated RRMS patients but not in HCMV(−) cases (p < 0.01), suggesting that HCMV may influence the distribution of B cell subsets modulating the effects of IFNβ. Considering the B cell functional profile, HCMV(−) PMS displayed an increased secretion of proinflammatory cytokines (IL-6, TNFα) as compared to HCMV(+) PMS and RRMS cases (p < 0.001).

Conclusions

Our study reveals an influence of HCMV infection on the phenotype and function of B cells, promoting early differentiation stages in RRMS and reducing the proinflammatory cytokine profile in advanced MS forms, which might be related with the putative protective role of this virus in MS.

The role of B cells in the immunopathogenesis of multiple sclerosis

There is ongoing debate on how B cells contribute to the pathogenesis of multiple sclerosis (MS). The success of B-cell targeting therapies in MS highlighted the role of B cells, particularly the antibody-independent functions of these cells such as antigen presentation to T cells and modulation of the function of T cells and myeloid cells by secreting pathogenic and/or protective cytokines in the central nervous system. Here, we discuss the role of different antibody-dependent and antibody-independent functions of B cells in MS disease activity and progression proposing new therapeutic strategies for the optimization of B-cell targeting treatments.

B cell function impacts the efficacy of IFN-β therapy in EAE

Recent studies identified that interferon beta (IFN-β) treatment skews B-cells towards a regulatory phenotype in multiple sclerosis. To assess B cell involvement during IFN-β therapy, we compared IFN-β treatment in a B cell-independent model and a B cell-dependent model of experimental autoimmune encephalomyelitis (EAE). We show that in B cell-independent EAE, IFN-β ameliorates neuroinflammation. Conversely, in B cell-dependent EAE, IFN-β has no effect on disease. Effective IFN-β therapy in B cell-independent EAE was associated with reduced inflammatory T cells in the CNS and skewed splenic B cells towards an immature population and away from a germinal center population. These immune cell populations were unchanged in B cell-dependent EAE. Finally, we found that IFN-β increased marginal zone B cells in both EAE models. These findings indicate that B cell function impacts IFN-β efficacy during neuroinflammation.

Regulatory B cells and transplantation: almost prime time?

PURPOSE OF REVIEW

Regulatory B cells (Bregs) are potent inhibitors of the immune system with the capacity to suppress autoimmune and alloimmune responses. Murine transplant models showing that Bregs can promote allograft tolerance are now supported by clinical data showing that patients who develop operational tolerance have higher frequency of Bregs. Breg function has been widely studied resulting in improved understanding of their biology and effector mechanisms. However, our overall understanding of Bregs remains poor due the lack of specific marker, limited knowledge of how and where they act in vivo, and whether different Breg subpopulations exhibit different functions.

RECENT FINDINGS

In this review we detail murine and human phenotypic markers used to identify Bregs, their induction, maintenance, and mechanisms of immune suppression. We highlight recent advances in the field including their use as biomarkers to predict allograft rejection, in-vitro expansion of Bregs, and the effects of commonly used immunosuppressive drugs on their induction and frequency.

SUMMARY

Clinical data continue to emerge in support of Bregs playing an important role in preventing transplant rejection. Hence, it is necessary for the transplant field to better comprehend the mechanisms of Breg induction and approaches to preserve or even enhance their activity to improve long-term transplant outcomes.

Long-term use of interferon-β in multiple sclerosis increases Vδ1-Vδ2-Vγ9- γδ T cells that are associated with a better outcome

Background

We previously reported that Vδ2⁺Vγ9⁺ γδ T cells were significantly decreased in multiple sclerosis (MS) patients without disease-modifying therapies (untreated MS) and were negatively correlated with Expanded Disability Status Scale (EDSS) scores, suggesting protective roles of Vδ2⁺Vγ9⁺ γδ T cells. Interferon-β (IFN-β) is one of the first-line disease-modifying drugs for MS. However, no previous studies have reported changes in γδ T cell subsets under IFN-β treatment. Therefore, we aimed to clarify the effects of the long-term usage of IFN-β on γδ T cell subsets in MS patients.

Methods

Comprehensive flow cytometric immunophenotyping was performed in 35 untreated MS and 21 MS patients on IFN-β for more than 2 years (IFN-β-treated MS) including eight super-responders fulfilling no evidence of disease activity criteria, and 44 healthy controls (HCs).

Results

The percentages of Vδ2⁺Vγ9⁺ cells in γδ T cells were significantly lower in untreated and IFN-β-treated MS patients than in HCs. By contrast, the percentages of Vδ1⁻Vδ2⁻Vγ9⁻ cells in γδ T cells were markedly higher in IFN-β-treated MS patients than in HCs and untreated MS patients (both p < 0.001). A significant negative correlation between the percentages of Vδ2⁺Vγ9⁺ cells in γδ T cells and EDSS scores was confirmed in untreated MS but not evident in IFN-β-treated MS. Moreover, class-switched memory B cells were decreased in IFN-β-treated MS compared with HCs (p < 0.001) and untreated MS patients (p = 0.006). Interestingly, the percentages of Vδ1⁻Vδ2⁻Vγ9⁻ cells in γδ T cells were negatively correlated with class-switched memory B cell percentages in all MS patients (r = − 0.369, p = 0.005), and the percentages of Vδ1⁻Vδ2⁻Vγ9⁻ cells in Vδ1⁻Vδ2⁻ γδ T cells were negatively correlated with EDSS scores only in IFN-β super-responders (r = − 0.976, p < 0.001).

Conclusions

The present study suggests that long-term usage of IFN-β increases Vδ1⁻Vδ2⁻Vγ9⁻ γδ T cells, which are associated with a better outcome, especially in IFN-β super-responders. Thus, increased Vδ1⁻Vδ2⁻Vγ9⁻ cells together with decreased class-switched memory B cells may contribute to the suppression of disease activity in MS patients under IFN-β treatment.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1574-5) contains supplementary material, which is available to authorized users.

Type I interferons provide additive signals for murine regulatory B cell induction by Schistosoma mansoni eggs

The helminth Schistosoma mansoni (S. mansoni) induces a network of regulatory immune cells, including interleukin (IL)-10-producing regulatory B cells (Bregs). However, the signals required for the development and activation of Bregs are not well characterized. Recent reports suggest that helminths induce type I interferons (IFN-I), and that IFN-I drive the development of Bregs in humans. We therefore assessed the role of IFN-I in the induction of Bregs by S. mansoni. Mice chronically infected with S. mansoni or i.v. injected with S. mansoni soluble egg antigen (SEA) developed a systemic IFN-I signature. Recombinant IFN-α enhanced IL-10 production by Bregs stimulated with S. mansoni SEA in vitro, while not activating Bregs by itself. IFN-I signaling also supported ex vivo IL-10 production by SEA-primed Bregs but was dispensable for activation of S. mansoni egg-induced Bregs in vivo. These data indicate that although IFN-I can serve as a coactivator for Breg IL-10 production, they are unlikely to participate in the development of Bregs in response to S. mansoni eggs.

B Cell-based Therapies for Multiple Sclerosis

The traditional view of multiple sclerosis (MS) as a T cell mediated autoimmune disease of the central nervous system (CNS) has evolved into a concept of an immune-mediated disease where complex bi-directional interactions between T cells, B cells and myeloid cells underlie and shape CNS-directed autoimmunity. B cells are now recognized as major contributors to the pathogenesis of MS, largely due to increased understanding of their biology and the profound anti-inflammatory effects demonstrated by B cell depletion in MS. In this chapter we discuss the fundamental roles B cells play in the pathogenesis of MS and review current and future therapeutic strategies targeting B cells in MS, including B cell depletion with various monoclonal antibodies (mAbs) against the B cell surface markers CD20 and CD19, anti-B cell cytokine therapies, blocking Bruton's tyrosine kinase (BTK) in B cells, and various immunomodulatory and immunosuppressive effects exerted on B cells by virtually all other approved therapies for MS.

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

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

B-Cell Therapies in Multiple Sclerosis

B cells play a vital function in multiple sclerosis (MS) pathogenesis through an array of effector functions. All currently approved MS disease-modifying therapies alter the frequency, phenotype, or homing of B cells in one way or another. The importance of this mechanism of action has been reinforced with the successful development and clinical testing of B-cell-depleting monoclonal antibodies that target the CD20 surface antigen. Ocrelizumab, a humanized anti-CD20 monoclonal antibody, was approved by the Food and Drug Administration (FDA) in March 2017 after pivotal trials showed dramatic reductions in inflammatory disease activity in relapsing MS as well as lessening of disability progression in primary progressive MS. These and other clinical studies place B cells at the center of the inflammatory cascade in MS and provide a launching point for development of therapies that target selective pathogenic B-cell populations.

Regulatory and Effector B Cells: A New Path Toward Biomarkers and Therapeutic Targets to Improve Transplant Outcomes?

B cells shape the alloimmune response through polarized subsets. These cells inhibit or promote immune responses by expressing suppressive or proinflammatory cytokines. Their summed activity dictates the influence of B cells on the alloimmune response. We review the evidence for regulatory B cells and effector B cells in mice and humans, discuss current limitations in their phenotypic identification, and discuss regulatory B cells as a signature for clinical renal allograft tolerance and predictive markers for allograft outcomes. We discuss the effects of therapeutic agents on regulatory B cells and potential approaches to augment their numbers as a therapeutic tool.

Regulatory B and T lymphocytes in multiple sclerosis: friends or foes?

Current clinical experience with immunomodulatory agents and monoclonal antibodies in principle has established the benefit of depleting lymphocytic populations in relapsing–remitting multiple sclerosis (RRMS). B and T cells may exert multiple pro-inflammatory actions, but also possess regulatory functions making their role in RRMS pathogenesis much more complex. There is no clear correlation of Tregs and Bregs with clinical features of the disease. Herein, we discuss the emerging data on regulatory T and B cell subset distributions in MS and their roles in the pathophysiology of MS and its murine model, experimental autoimmune encephalomyelitis (EAE). In addition, we summarize the immunomodulatory properties of certain MS therapeutic agents through their effect on such regulatory cell subsets and their relevance to clinical outcomes.

The role of B cells in multiple sclerosis: Current and future therapies

While it was long held that T cells were the primary mediators of multiple sclerosis (MS) pathogenesis, the beneficial effects observed in response to treatment with Rituximab (RTX), a monoclonal antibody (mAb) targeting CD20, shed light on a key contributor to MS that had been previously underappreciated: B cells. This has been reaffirmed by results from clinical trials testing the efficacy of subsequently developed B cell-depleting mAbs targeting CD20 as well as studies revisiting the effects of previous disease-modifying therapies (DMTs) on B cell subsets thought to modulate disease severity. In this review, we summarize current knowledge regarding the complex roles of B cells in MS pathogenesis and current and potential future B cell-directed therapies.

Analysis of coding and non-coding transcriptome of peripheral B cells reveals an altered interferon response factor (IRF)-1 pathway in multiple sclerosis patients

Several evidences emphasize B-cell pathogenic roles in multiple sclerosis (MS). We performed transcriptome analyses on peripheral B cells from therapy-free patients and age/sex-matched controls. Down-regulation of two transcripts (interferon response factor 1-IRF1, and C-X-C motif chemokine 10-CXCL10), belonging to the same pathway, was validated by RT-PCR in 26 patients and 21 controls. IRF1 and CXCL10 transcripts share potential seeding sequences for hsa-miR-424, that resulted up-regulated in MS patients. We confirmed this interaction and its functional effect by transfection experiments. Consistent findings indicate down-regulation of IRF1/CXCL10 axis, that may plausibly contribute to a pro-survival status of B cells in MS.

Different clinical response to interferon beta and glatiramer acetate related to the presence of oligoclonal IgM bands in CSF in multiple sclerosis patients

OBJECTIVE

To study the efficacy of interferon beta (IFNβ) and glatiramer acetate (GA) related to the presence of oligoclonal M bands (OCMB) in the cerebrospinal fluid in relapsing-remitting multiple sclerosis (RRMS).

METHOD

This is an observational, multicenter and retrospective study with prospectively collected data of patients that started treatment with IFNβ or GA. Treatment decision was made blinded to the OCMB status. Time to first attack after starting therapy was compared by using Kaplan-Meier curves, and adjustment by Cox regression analysis was performed.

RESULTS

Two hundred and fifty-six patients entered in the study (141-55% received IFNβ; 115-45% received GA). After a mean follow-up of 41 and 65 months, 54.7% of patients remained free from further attacks (RF). The proportion of RF patients was higher in the GA group than in the IFNβ group (72.2 vs. 40.4%, p < 0.001). The IFNβ patients with OCMB+ presented the poorest response, 31.3% RF vs. 48.1% in IFNβ without OCMB, p = 0.03.

CONCLUSION

OCMB in CSF could be a biomarker of treatment response in multiple sclerosis.

Deciphering the Role of B Cells in Multiple Sclerosis-Towards Specific Targeting of Pathogenic Function

B cells, plasma cells and antibodies may play a key role in the pathogenesis of multiple sclerosis (MS). This notion is supported by various immunological changes observed in MS patients, such as activation and pro-inflammatory differentiation of peripheral blood B cells, the persistence of clonally expanded plasma cells producing immunoglobulins in the cerebrospinal fluid, as well as the composition of inflammatory central nervous system lesions frequently containing co-localizing antibody depositions and activated complement. In recent years, the perception of a respective pathophysiological B cell involvement was vividly promoted by the empirical success of anti-CD20-mediated B cell depletion in clinical trials; based on these findings, the first monoclonal anti-CD20 antibody—ocrelizumab—is currently in the process of being approved for treatment of MS. In this review, we summarize the current knowledge on the role of B cells, plasma cells and antibodies in MS and elucidate how approved and future treatments, first and foremost anti-CD20 antibodies, therapeutically modify these B cell components. We will furthermore describe regulatory functions of B cells in MS and discuss how the evolving knowledge of these therapeutically desirable B cell properties can be harnessed to improve future safety and efficacy of B cell-directed therapy in MS.

Effector and regulatory B cells in Multiple Sclerosis

The role of B cells in the pathogenesis of Multiple Sclerosis (MS), an autoimmune neurodegenerative disease, is becoming eminent in recent years, but the specific contribution of the distinct B cell subsets remains to be elucidated. Several B cell subsets have shown regulatory, anti-inflammatory capacities in response to stimuli in vitro, as well as in the animal model of MS: Experimental Autoimmune Encephalomyelitis (EAE). However, the functional role of the B regulatory cells (Bregs) in vivo and specifically in the human disease is yet to be clarified. In the present review, we have summarized the updated information on the roles of effector and regulatory B cells in MS and the immune-modulatory effects of MS therapeutic agents on their phenotype and function.

Human regulatory B cells in health and disease: therapeutic potential

Regulatory B cells (Bregs) modulate immune responses predominantly, although not exclusively, via the release of IL-10. The importance of human Bregs in the maintenance of immune homeostasis comes from a variety of immune-related pathologies, such as autoimmune diseases, cancers, and chronic infections that are often associated with abnormalities in Breg numbers or function. A continuous effort toward understanding Breg biology in healthy individuals will provide new opportunities to develop Breg immunotherapy that could prove beneficial in treating various immune-mediated pathologies. In this Review, we discuss findings regarding human Bregs, including their mechanisms of suppression and role in different disease settings. We also propose several therapeutic strategies targeting Bregs for better management of immune disorders.

Memory B Cells are Major Targets for Effective Immunotherapy in Relapsing Multiple Sclerosis

Although multiple sclerosis (MS) is considered to be a CD4, Th17-mediated autoimmune disease, supportive evidence is perhaps circumstantial, often based on animal studies, and is questioned by the perceived failure of CD4-depleting antibodies to control relapsing MS. Therefore, it was interestingly to find that current MS-treatments, believed to act via T cell inhibition, including: beta-interferons, glatiramer acetate, cytostatic agents, dimethyl fumarate, fingolimod, cladribine, daclizumab, rituximab/ocrelizumab physically, or functionally in the case of natalizumab, also depleted CD19+, CD27+ memory B cells. This depletion was substantial and long-term following CD52 and CD20-depletion, and both also induced long-term inhibition of MS with few treatment cycles, indicating induction-therapy activity. Importantly, memory B cells were augmented by B cell activating factor (atacicept) and tumor necrosis factor (infliximab) blockade that are known to worsen MS. This creates a unifying concept centered on memory B cells that is consistent with therapeutic, histopathological and etiological aspects of MS.

B Cell-Directed Therapeutics in Multiple Sclerosis: Rationale and Clinical Evidence

Over the last decade, evidence condensed that B cells, B cell-derived plasma cells and antibodies play a key role in the pathogenesis and progression of multiple sclerosis (MS). In many patients with MS, peripheral B cells show signs of chronic activation; within the cerebrospinal fluid clonally expanded plasma cells produce oligoclonal immunoglobulins, which remain a hallmark diagnostic finding. Confirming the clinical relevance of these immunological alterations, recent trials testing anti-CD20-mediated depletion of peripheral B cells showed an instantaneous halt in development of new central nervous system lesions and occurrence of relapses. Notwithstanding this enormous success, not all B cells or B cell subsets may contribute in a pathogenic manner, and may, in contrast, exert anti-inflammatory and, thus, therapeutically desirable properties in MS. Naïve B cells, in MS patients similar to healthy controls, are a relevant source of regulatory cytokines such as interleukin-10, which dampens the activity of other immune cells and promotes recovery from acute disease flares in experimental MS models. In this review, we describe in detail pathogenic but also regulatory properties of B and plasma cells in the context of MS and its animal model experimental autoimmune encephalomyelitis. In the second part, we review what impact current and future therapies may have on these B cell properties. Within this section, we focus on the highly encouraging data on anti-CD20 antibodies as future therapy for MS. Lastly, we discuss how B cell-directed therapy in MS could be possibly advanced even further in regard to efficacy and safety by integrating the emerging information on B cell regulation in MS into future therapeutic strategies.

B cells of multiple sclerosis patients induce autoreactive proinflammatory T cell responses

Antibody-independent B cell functions play an important role in multiple sclerosis (MS) pathogenesis. In this study, B cell antigen presentation and costimulation in MS were studied. Peripheral blood B cells of MS patients showed increased expression of costimulatory CD86 and CD80 molecules compared with healthy controls (HC). In MS cerebrospinal fluid (CSF), 12-fold and 2-fold increases in CD86⁺ and CD80⁺ B cells, respectively, were evidenced compared with peripheral blood. Further, B cells from MS patients induced proinflammatory T cells in response to myelin basic protein (MBP). Immunomodulatory treatment restored B cell costimulatory molecule expression and caused significantly reduced B cell induced T cell responses. Together, these results demonstrate the potential of B cells from MS patients to induce autoreactive proinflammatory T cell responses. Immunomodulatory therapy abrogated this effect, emphasizing the importance of B cell antigen presentation and costimulation in MS pathology.

Interferon-β therapy specifically reduces pathogenic memory B cells in multiple sclerosis patients by inducing a FAS-mediated apoptosis

Growing evidences put B lymphocytes on a central stage in multiple sclerosis (MS) immunopathology. While investigating the effects of interferon-β (IFN-β) therapy, one of the most used first-line disease-modifying drugs for the treatment of relapsing-remitting MS, in circulating B-cell sub-populations, we found a specific and marked decrease of CD27⁺ memory B cells. Interestingly, memory B cells are considered a population with a great disease-driving relevance in MS and resulted to be also target of B-cell depleting therapies. In addition, Epstein-Barr virus (EBV), associated with MS etiopathogenesis, harbors in this cell type and an IFN-β-induced reduction of the memory B-cell compartment, in turn, resulted in a decreased expression of the EBV gene latent membrane protein 2A in treated patients. We found that in vivo IFN-β therapy specifically and highly induced apoptosis in memory B cells, in accordance with a strong increase of the apoptotic markers Annexin-V and active caspase-3, via a mechanism requiring the FAS-receptor/TACI (transmembrane activator and CAML interactor) signaling. Thus, efficacy of IFN-β therapy in MS may rely not only on its recognized anti-inflammatory activities but also on the specific depletion of memory B cells, considered to be a pathogenic cell subset, reducing their inflammatory impact in target organs.

Immunologic profiles of multiple sclerosis treatments reveal shared early B cell alterations

Objective:

We undertook a systems immunology approach of the adaptive immune system in multiple sclerosis (MS), overcoming tradeoffs between scale and level of detail, in order to identify the immunologic signature of MS and the changes wrought by current immunomodulatory treatments.

Methods:

We developed a comprehensive flow cytometry platform measuring 38 immunologic cell types in the peripheral blood of 245 individuals in a routine clinical setting. These include patients with MS, untreated or receiving any of 4 current immunomodulatory treatments (interferon-β, glatiramer acetate, natalizumab, or fingolimod), patients with autoimmune thyroid disease, and healthy controls.

Results:

An increase in memory CD8⁺ T cells and B cells was observed in untreated patients with MS. Interferon-β and fingolimod induce significant changes upon multiple aspects of the peripheral immune system, with an unexpectedly prominent alteration of B cells. Overall, both treatments push the immune system in different directions, with only 2 significant effects shared across these treatments—an increase in transitional B cells and a decrease in class-switched B cells. We further identified heightened B cell-activating factor (BAFF) levels as regulating this shared B cell pathway.

Conclusions:

A systems immunology approach established different immunologic profiles induced by current immunomodulatory MS treatments, offering perspectives for personalized medicine. Pathways shared between the immunologic architecture of existing efficacious treatments identify targets for future treatment design.