Role of the CD19 and CD21/35 receptor complex in innate immunity, host defense and autoimmunity

Primary bone diffuse large B-cell lymphoma (PB-DLBCL): a distinct extranodal lymphoma of germinal centre origin, with a common EZB-like mutational profile and good prognosis

AIMS

Primary bone diffuse large B-cell lymphoma (PB-DLBCL) is not recognized as a separate entity by the current classification systems. Here we define and highlight its distinctive clinical presentation, morphology, phenotype, gene expression profile (GEP), and molecular genetics.

METHODS

We collected 27 respective cases and investigated their phenotype, performed gDNA panel sequencing covering 172 genes, and carried out fluorescence in situ hybridization to evaluate MYC, BCL2, and BCL6 translocations. We attempted to genetically subclassify cases using the Two-step classifier and performed GEP for cell-of-origin subtyping and in silico comparison to uncover up- and downregulated genes as opposed to other DLBCL.

RESULTS

Most cases (n = 22) were germinal centre B-cell-like (GCB) by immunohistochemistry and all by GEP. Additionally, PB-DLBCL had a mutational profile similar to follicular lymphoma and nodal GCB-DLBCL, with the exception of more frequent TP53 and B2M mutations. The GEP of PB-DLBCL was unique, and the frequency of BCL2 rearrangements was lower compared to nodal GCB-DLBCL. The Two-step classifier categorized eight of the cases as EZB, three as ST2, and one as MCD.

CONCLUSION

This study comprehensively characterizes PB-DLBCL as a separate entity with distinct clinical and morpho-molecular features. These insights may aid in developing tailored therapeutic strategies and shed light on its pathogenesis.

Unveiling the autoreactome: Proteome-wide immunological fingerprints reveal the promise of plasma cell depleting therapy

The prevalence and burden of autoimmune and autoantibody mediated disease is increasing worldwide, yet most disease etiologies remain unclear. Despite numerous new targeted immunomodulatory therapies, comprehensive approaches to apply and evaluate the effects of these treatments longitudinally are lacking. Here, we leverage advances in programmable-phage immunoprecipitation (PhIP-Seq) methodology to explore the modulation, or lack thereof, of proteome-wide autoantibody profiles in both health and disease. We demonstrate that each individual, regardless of disease state, possesses a distinct set of autoreactivities constituting a unique immunological fingerprint, or "autoreactome", that is remarkably stable over years. In addition to uncovering important new biology, the autoreactome can be used to better evaluate the relative effectiveness of various therapies in altering autoantibody repertoires. We find that therapies targeting B-Cell Maturation Antigen (BCMA) profoundly alter an individual's autoreactome, while anti-CD19 and CD-20 therapies have minimal effects, strongly suggesting a rationale for BCMA or other plasma cell targeted therapies in autoantibody mediated diseases.

Understanding the Bioactivity and Prognostic Implication of Commonly Used Surface Antigens in Multiple Myeloma

Multiple myeloma (MM) progression is dependent on its interaction with the bone marrow microenvironment and the immune system and is mediated by key surface antigens. Some antigens promote adhesion to the bone marrow matrix and stromal cells, while others are involved in intercellular interactions that result in differentiation of B-cells to plasma cells (PC). These interactions are also involved in malignant transformation of the normal PC to MM PC as well as disease progression. Here, we review selected surface antigens that are commonly used in the flow cytometry analysis of MM for identification of plasma cells (PC) and the discrimination between normal and malignant PC as well as prognostication. These include the markers: CD38, CD138, CD45, CD19, CD117, CD56, CD81, CD27, and CD28. Furthermore, we will discuss the novel marker CD24 and its involvement in MM. The bioactivity of each antigen is reviewed, as well as its expression on normal vs. malignant PC, prognostic implications, and therapeutic utility. Understanding the role of these specific surface antigens, as well as complex co-expressions of combinations of antigens, may allow for a more personalized prognostic monitoring and treatment of MM patients.

State of the CAR-T: Risk of Infections with Chimeric Antigen Receptor T-Cell Therapy and Determinants of SARS-CoV-2 Vaccine Responses

Chimeric antigen receptor T cell (CAR-T) therapy has shown unprecedented response rates in patients with relapsed/refractory (R/R) hematologic malignancies. Although CAR-T therapy gives hope to heavily pretreated patients, the rapid commercialization and cumulative immunosuppression of this therapy predispose patients to infections for a prolonged period. CAR-T therapy poses distinctive short- and long-term toxicities and infection risks among patients who receive CAR T-cells after multiple prior treatments, often including hematopoietic cell transplantation. The acute toxicities include cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. The long-term B cell depletion, hypogammaglobulinemia, and cytopenia further predispose patients to severe infections and abrogate the remission success achieved by the living drug. These on-target-off-tumor toxicities deplete B-cells across the entire lineage and further diminish immune responses to vaccines. Early observational data suggest that patients with hematologic malignancies may not mount adequate humoral and cellular responses to SARS-CoV-2 vaccines. In this review, we summarize the immune compromising factors indigenous to CAR-T recipients. We discuss the immunogenic potential of different SARS-CoV-2 vaccines for CAR-T recipients based on the differences in vaccine manufacturing platforms. Given the lack of data related to the safety and efficacy of SARS-CoV-2 vaccines in this distinctively immunosuppressed cohort, we summarize the infection risks associated with Food and Drug Administration-approved CAR-T constructs and the potential determinants of vaccine responses. The review further highlights the potential need for booster vaccine dosing and the promise for heterologous prime-boosting and other novel vaccine strategies in CAR-T recipients. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Immunotherapy of Multiple Myeloma: Promise and Challenges

Whereas the treatment of MM was dependent solely on alkylating agents and corticosteroids during the prior three decades, the landscape of therapeutic measures to treat the disease began to expand enormously early in the current century. The introduction of new classes of small-molecule drugs, such as proteasome blockers (bortezomib and carfilzomib), immunomodulators (lenalidomide and pomalidomide), nuclear export inhibitors (selinexor), and histone deacetylase blockers (panobinostat), as well as the application of autologous stem cell transplantation (ASCT), resulted in a seismic shift in how the disease is treated. The picture changed dramatically once again starting with the 2015 FDA approval of two monoclonal antibodies (mAbs) - the anti-CD38 daratumumab and the anti-SLAMF7 elotuzumab. Daratumumab, in particular, has had a great impact on MM therapy and today is often included in various regimens to treat the disease, both in newly diagnosed cases and in the relapse/refractory setting. Recently, other immunotherapies have been added to the arsenal of drugs available to fight this malignancy. These include isatuximab (also anti-CD38) and, in the past year, the antibody-drug conjugate (ADC) belantamab mafodotin and the chimeric antigen receptor (CAR) T-cell product idecabtagene vicleucel (ide-cel). While the accumulated benefits of these newer agents have resulted in a doubling of the disease's five-year survival rate to more than 5 years and improved quality of life, the disease remains incurable. Almost without exception patients experience relapse and/or become refractory to the drugs used, making the search for innovative therapies all the more essential. This review covers the current scope of anti-myeloma immunotherapeutic agents, both those in clinical use and on the horizon, including naked mAbs, ADCs, bi- and multi-targeted mAbs, and CAR T-cells. Emphasis is placed on the benefits of each along with the challenges that need to be overcome if MM is to be considered curable in the future.

EMA Review of Axicabtagene Ciloleucel (Yescarta) for the Treatment of Diffuse Large B-Cell Lymphoma

On June 28, 2018, the Committee for Advanced Therapies and the Committee for Medicinal Products for Human Use adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Yescarta for the treatment of adult patients with relapsed or refractory diffuse large B-cell lymphoma and primary mediastinal large B-cell lymphoma, after two or more lines of systemic therapy. Yescarta, which was designated as an orphan medicinal product and included in the European Medicines Agency's Priority Medicines scheme, was granted an accelerated review timetable. The active substance of Yescarta is axicabtagene ciloleucel, an engineered autologous T-cell immunotherapy product whereby a patient's own T cells are harvested and genetically modified ex vivo by retroviral transduction using a retroviral vector to express a chimeric antigen receptor (CAR) comprising an anti-CD19 single chain variable fragment linked to CD28 costimulatory domain and CD3-zeta signaling domain. The transduced anti-CD19 CAR T cells are expanded ex vivo and infused back into the patient, where they can recognize and eliminate CD19-expressing cells. The benefits of Yescarta as studied in ZUMA-1 phase II (NCT02348216) were an overall response rate per central review of 66% (95% confidence interval, 56%-75%) at a median follow-up of 15.1 months in the intention to treat population and a complete response rate of 47% with a significant duration. The most common adverse events were cytokine release syndrome, neurological adverse events, infections, pyrexia, diarrhea, nausea, hypotension, and fatigue. IMPLICATIONS FOR PRACTICE: Yescarta (axicabtagene ciloleucel) was the first chimeric antigen receptor T-cell therapy to be submitted for evaluation to the European Medicines Agency and admitted into the "priority medicine" scheme; it was granted accelerated assessment on the basis of anticipated clinical benefit in relapsed/refractory diffuse large B-cell lymphoma, a condition of unmet medical need. Indeed, Yescarta showed an overall response rate of 66% and a complete response rate of 47% with a significant duration and a manageable toxicity that compared very favorably with historical controls. Here the analysis of benefits and risks is presented, and specific challenges with this important novel product are highlighted, providing further insights and reflections for future medical research.

Bispecific Antibodies for Multiple Myeloma: A Review of Targets, Drugs, Clinical Trials, and Future Directions

Multiple myeloma (MM) is a plasma cell malignancy and the second most common hematological neoplasm in adults, comprising 1.8% of all cancers. With an annual incidence of ~30,770 cases in the United States, MM has a high mortality rate, leading to 12,770 deaths per year. MM is a genetically complex, highly heterogeneous malignancy, with significant inter- and intra-patient clonal variability. Recent years have witnessed dramatic improvements in the diagnostics, classification, and treatment of MM. However, patients with high-risk disease have not yet benefited from therapeutic advances. High-risk patients are often primary refractory to treatment or relapse early, ultimately resulting in progression toward aggressive end-stage MM, with associated extramedullary disease or plasma cell leukemia. Therefore, novel treatment modalities are needed to improve the outcomes of these patients. Bispecific antibodies (BsAbs) are immunotherapeutics that simultaneously target and thereby redirect effector immune cells to tumor cells. BsAbs have shown high efficacy in B cell malignancies, including refractory/relapsed acute lymphoblastic leukemia. Various BsAbs targeting MM-specific antigens such as B cell maturation antigen (BCMA), CD38, and CD138 are currently in pre-clinical and clinical development, with promising results. In this review, we outline these advances, focusing on BsAb drugs, their targets, and their potential to improve survival, especially for high-risk MM patients. In combination with current treatment strategies, BsAbs may pave the way toward a cure for MM.

B cells targeting therapy in the management of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease which affects the majority of organs and systems. Traditional therapies do not lead to complete remission of disease but only relieve symptoms and inflammation. B cells are the most important effector cell types in the pathogenesis of SLE. Therefore, therapies targeting B cells and their related cytokines are a very important milestone for SLE treatment. Several biologics that modulate B cells, either depleting B cells or blocking B cell functions, have been developed and evaluated in clinical trials. Belimumab, a fully humanized monoclonal antibody that specifically binds B cells activating factor (BAFF), was the first of these agents approved for SLE treatment. In this review, we explore the currently available evidence in B cell targeted therapies in SLE including agents that target B cell surface antigens (CD19, CD20, CD22), B cell survival factors (BAFF and a proliferation-inducing ligand, APRIL), cytokines (interleukin-1 and type 1 interferons) and co-stimulatory molecules (CD40 ligand). We highlighted the mechanisms of action and the individual characteristics of these biologics, and present an update on the clinical trials that have evaluated their efficacy and safety. Finally, we describe some of the emerging and promising therapies for SLE treatment.

National Institutes of Health-Defined Chronic Graft-vs.-Host Disease in Pediatric Hematopoietic Stem Cell Transplantation Patients Correlates With Parameters of Long-Term Immune Reconstitution

Recent data revealed the importance of immune reconstitution (IR) for the evaluation of possible biomarkers in National Institutes of Health (NIH)–defined chronic graft-vs.-host disease (cGVHD) and its clinical aspects. In this large pediatric study (n = 146), we have analyzed whether cellular and humoral parameters of IR in the long-term follow-up (FU) with a special emphasis on B-cell reconstitution correlate with NIH-defined cGVHD criteria. HYPOTHESIS: we were especially interested in whether meaningful cGVHD biomarkers could be defined in a large pediatric cohort. We here demonstrate for the first time in a highly homogenous pediatric patient cohort that both cGVHD (n = 38) and its activity were associated with the perturbation of the B-cell compartment, including low frequencies of CD19⁺CD27⁺ memory B-cells and increased frequencies of circulating CD19⁺CD21^low B-cells, a well-known hyperactivated B-cell subset frequently found elevated in chronic infection and autoimmunity. Notably, resolution of cGVHD correlated with expansion of CD19⁺CD27⁺ memory B-cells and normalization of CD19⁺CD21^low B-cell frequencies. Moreover, we found that the severity of cGVHD had an impact on parameters of IR and that severe cGVHD was associated with increased CD19⁺CD21^low B-cell frequencies. When comparing the clinical characteristics of the active and non-active cGVHD patients (in detail at time of analyses), we found a correlation between activity and a higher overall severity of cGVHD, which means that in the active cGVHD patient group were more patients with a higher disease burden of cGVHD—despite similar risk profiles for cGVHD. Our data also provide solid evidence that the time point of analysis regarding both hematopoietic stem cell transplantation (HSCT) FU and cGVHD disease activity may be of critical importance for the detailed investigation of pediatric cohorts. Finally, we have proven that the differences in risk factors and patterns of IR, with cGVHD as its main confounding factor, between malignant and non-malignant diseases, are important to be considered in future studies aiming at identification of novel biomarkers for cGVHD.

Immune Pharmacodynamic Responses of the Novel Cancer Immunotherapeutic Imprime PGG in Healthy Volunteers

Imprime PGG (Imprime) is an i.v. administered, yeast β-1,3/1,6 glucan in clinical development with checkpoint inhibitors. Imprime-mediated innate immune activation requires immune complex formation with naturally occurring IgG anti-β glucan Abs (ABA). We administered Imprime to healthy human volunteers to assess the necessity of ABA for Imprime-mediated immunopharmacodynamic (IPD) changes. Imprime (4 mg/kg) was administered i.v. in single and multiple infusions. Subsets of subjects were premedicated with antihistamine and corticosteroid. Peripheral blood was measured before, during and after Imprime administration for IPD changes (e.g., ABA, circulating immune complexes, complement activation, complete blood counts, cytokine/chemokine, and gene expression changes). IPD changes were analyzed based on pretreatment serum ABA levels: low-ABA (<20 μg/ml), mid-ABA (≥20-50 μg/ml), and high-ABA (≥50 μg/ml). At the end of infusion, free serum ABA levels decreased, circulating immune complex levels increased, and complement activation was observed. At ∼1-4 h after end of infusion, increased expression of cytokines/chemokines, a 1.5-4-fold increase in neutrophil and monocyte counts and a broad activation of innate immune genes were observed. Low-ABA subjects typically showed minimal IPD changes except when ABA levels rose above 20 μg/ml after repeated Imprime dosing. Mild-to-moderate infusion-related reactions occurred in subjects with ABA ≥20 μg/ml. Premedications alleviated some of the infusion-related reactions, but also inhibited cytokine responses. In conclusion, ABA levels, being critical for Imprime-mediated immune activation may provide a plausible, mechanism-based biomarker to identify patients most likely to respond to Imprime-based anticancer immunotherapy.

Immune synergistic oligodeoxynucleotide from Lactobacillus rhamnosus GG enhances the immune response upon co-stimulation by bacterial and fungal cell wall components

Bacterial genomic DNA has recently been shown to elicit a highly evolved immune defense. This response can be selectively triggered for a wide range of therapeutic applications, including use as a vaccine adjuvant to immunotherapies for allergy, cancer, and infectious diseases. Previously, we identified a low-concentration immune synergistic oligodeoxynucleotide (iSN-ODN, named iSN34) from Lactobacillus rhamnosus GG that has immunosynergistic activity upon costimulation of target cells with ligands of Toll-like receptor 9 (TLR9). Here, we extend that observation by demonstrating the synergistic induction (in mouse splenocytes) of IL-6 by the combination of iSN34 with cell wall components of bacteria and fungi. We observed that splenocytes pretreated with iSN34 and then costimulated with agonists for TLR1/2 (Pam₃ CSK₄ ), TLR4 (lipopolysaccharide), or TLR2/6 (Zymosan) exhibited enhanced accumulation of IL-6. These results suggested that the combination of iSN34 with TLR1/2, TLR4, or TLR2/6 agonists may permit the induction of a potent immune response.

B cell-based therapies in CNS autoimmunity: differentiating CD19 and CD20 as therapeutic targets

Increasing recognition of the role of B cells in the adaptive immune response makes B cells an important therapeutic target in autoimmunity. Numerous current and developmental immunotherapies target B cells for elimination through recognition of cell-surface proteins expressed specifically on B cells, in particular CD19 and CD20. Similarities and differences in the function and expression of these two molecules predict some shared, and some distinct, pharmacological effects of agents targeting CD19 versus CD20, potentially leading to differences in the clinical safety and efficacy of such agents. Here, we review current knowledge of CD19 and CD20 function and biology, survey current and developmental therapies that target these molecules, and discuss potential differences in elimination of B cells by drugs that target CD19 versus CD20, with particular focus on the central nervous system autoimmune diseases multiple sclerosis and neuromyelitis optica. The principles and mechanisms herein discussed might also be relevant to a variety of other nervous system autoimmune disorders, including NMDA (N-methyl-D-aspartate) receptor encephalitis, transverse myelitis and myasthenia gravis.

ADCT-402, a PBD dimer-containing antibody drug conjugate targeting CD19-expressing malignancies

Human CD19 antigen is a 95-kDa type I membrane glycoprotein in the immunoglobulin superfamily whose expression is limited to the various stages of B-cell development and differentiation and is maintained in the majority of B-cell malignancies, including leukemias and non-Hodgkin lymphomas of B-cell origin. Coupled with its differential and favorable expression profile, CD19 has rapid internalization kinetics and is not shed into the circulation, making it an ideal target for the development of antibody-drug conjugates (ADCs) to treat B-cell malignancies. ADCT-402 (loncastuximab tesirine) is a novel CD19-targeted ADC delivering SG3199, a highly cytotoxic DNA minor groove interstrand crosslinking pyrrolobenzodiazepine (PDB) dimer warhead. It showed potent and highly targeted in vitro cytotoxicity in CD19-expressing human cell lines. ADCT-402 was specifically bound, internalized, and trafficked to lysosomes in CD19-expressing cells and, following release of the PBD warhead, resulted in formation of DNA crosslinks that persisted for 36 hours. Bystander killing of CD19- cells by ADCT-402 was also observed. In vivo, single doses of ADCT-402 resulted in highly potent, dose-dependent antitumor activity in several subcutaneous and disseminated human tumor models with marked superiority to comparator ADCs delivering tubulin inhibitors. Dose-dependent DNA crosslinks and γ-H2AX DNA damage response were measured in tumors by 24 hours after single dose administration, whereas matched peripheral blood mononuclear cells showed no evidence of DNA damage. Pharmacokinetic analysis in rat and cynomolgus monkey showed excellent stability and tolerability of ADCT-402 in vivo. Together, these impressive data were used to support the clinical testing of this novel ADC in patients with CD19-expressing B-cell malignancies.

CD22 Promotes B-1b Cell Responses to T Cell-Independent Type 2 Antigens

CD22 (Siglec-2) is a critical regulator of B cell activation and survival. CD22^-/- mice generate significantly impaired Ab responses to T cell-independent type 2 (TI-2) Ags, including haptenated Ficoll and pneumococcal polysaccharides, Ags that elicit poor T cell help and activate BCR signaling via multivalent epitope crosslinking. This has been proposed to be due to impaired marginal zone (MZ) B cell development/maintenance in CD22^-/- mice. However, mice expressing a mutant form of CD22 unable to bind sialic acid ligands generated normal TI-2 Ab responses, despite significantly reduced MZ B cells. Moreover, mice treated with CD22 ligand-binding blocking mAbs, which deplete MZ B cells, had little effect on TI-2 Ab responses. We therefore investigated the effects of CD22 deficiency on B-1b cells, an innate-like B cell population that plays a key role in TI-2 Ab responses. B-1b cells from CD22^-/- mice had impaired BCR-induced proliferation and significantly increased intracellular Ca²⁺ concentration responses following BCR crosslinking. Ag-specific B-1b cell expansion and plasmablast differentiation following TI-2 Ag immunization was significantly impaired in CD22^-/- mice, consistent with reduced TI-2 Ab responses. We generated CD22^-/- mice with reduced CD19 levels (CD22^-/-CD19^+/-) to test the hypothesis that augmented B-1b cell BCR signaling in CD22^-/- mice contributes to impaired TI-2 Ab responses. BCR-induced proliferation and intracellular Ca²⁺ concentration responses were normalized in CD22^-/-CD19^+/- B-1b cells. Consistent with this, TI-2 Ag-specific B-1b cell expansion, plasmablast differentiation, survival, and Ab responses were rescued in CD22^-/-CD19^+/- mice. Thus, CD22 plays a critical role in regulating TI-2 Ab responses through regulating B-1b cell signaling thresholds.

A distinct plasmablast and naïve B-cell phenotype in primary immune thrombocytopenia

Primary immune thrombocytopenia is an autoimmune disorder in which platelet destruction is a consequence of both B- and T-cell dysregulation. Flow cytometry was used to further characterize the B- and T-cell compartments in a cross-sectional cohort of 26 immune thrombocytopenia patients including antiplatelet antibody positive (n=14) and negative (n=12) patients exposed to a range of therapies, and a cohort of matched healthy volunteers. Markers for B-cell activating factor and its receptors, relevant B-cell activation markers (CD95 and CD21) and markers for CD4(+) T-cell subsets, including circulating T-follicular helper-like cells, were included. Our results indicate that an expanded population of CD95(+) naïve B cells correlated with disease activity in immune thrombocytopenia patients regardless of treatment status. A population of CD21-naïve B cells was specifically expanded in autoantibody-positive immune thrombocytopenia patients. Furthermore, the B-cell maturation antigen, a receptor for B-cell activating factor, was consistently and strongly up-regulated on plasmablasts from immune thrombocytopenia patients. These observations have parallels in other autoantibody-mediated diseases and suggest that loss of peripheral tolerance in naïve B cells may be an important component of immune thrombocytopenia pathogenesis. Moreover, the B-cell maturation antigen represents a potential target for plasma cell directed therapies in immune thrombocytopenia.

Targeting of Ly9 (CD229) Disrupts Marginal Zone and B1 B Cell Homeostasis and Antibody Responses

Marginal zone (MZ) and B1 B cells have the capacity to respond to foreign Ags more rapidly than conventional B cells, providing early immune responses to blood-borne pathogens. Ly9 (CD229, SLAMF3), a member of the signaling lymphocytic activation molecule family receptors, has been implicated in the development and function of innate T lymphocytes. In this article, we provide evidence that in Ly9-deficient mice splenic transitional 1, MZ, and B1a B cells are markedly expanded, whereas development of B lymphocytes in bone marrow is unaltered. Consistent with an increased number of these B cell subsets, we detected elevated levels of IgG3 natural Abs and a striking increase of T-independent type II Abs after immunization with 2,4,6-trinitrophenyl-Ficoll in the serum of Ly9-deficient mice. The notion that Ly9 could be a negative regulator of innate-like B cell responses was supported by the observation that administering an mAb directed against Ly9 to wild-type mice selectively eliminated splenic MZ B cells and significantly reduced the numbers of B1 and transitional 1 B cells. In addition, Ly9 mAb dramatically diminished in vivo humoral responses and caused a selective downregulation of the CD19/CD21/CD81 complex on B cells and concomitantly an impaired B cell survival and activation in an Fc-independent manner. We conclude that altered signaling caused by the absence of Ly9 or induced by anti-Ly9 may negatively regulate development and function of innate-like B cells by modulating B cell activation thresholds. The results suggest that Ly9 could serve as a novel target for the treatment of B cell-related diseases.

A unique population of IgG-expressing plasma cells lacking CD19 is enriched in human bone marrow

Healthy human BM is enriched for PC lacking CD19 that express a prosurvival and distinctly mature phenotype. CD19− PC resist mobilization into blood during immune responses after vaccination as well as B-cell depletion with rituximab.

Critical role of SHP2 (PTPN11) signaling in germinal center-derived lymphoma

Germinal center lymphoma is a heterogeneous human lymphoma entity. Here we report that constitutive activity of SHP2 (PTPN11) and its downstream kinase ERK is essential for the viability of germinal center lymphoma cells and disease progression. Mechanistically, SHP2/ERK inhibition impedes c-Myc transcriptional activity, which results in the repression of proliferative phenotype signatures of germinal center lymphoma. Furthermore, SHP2/ERK signaling is required to maintain the CD19/c-Myc loop, which preferentially promotes survival of a distinct subtype of germinal center lymphoma cells carrying the MYC/IGH translocation. These findings demonstrate a critical function for SHP2/ERK signaling upstream of c-Myc in germinal center lymphoma cells and provide a rationale for targeting SHP2 in the therapy of germinal center lymphoma.

Seed targeting with tiny anti-miR-155 inhibits malignant progression of multiple myeloma cells

BACKGROUND

miR-155 acts as a ubiquitous oncogene in major classes of human cancers and is a potential target for therapeutic intervention. However, the role of miR-155 in multiple myeloma is poorly understood.

METHODS

To explore the role of miR-155 in multiple myeloma, we assessed the influence of tiny seed-targeting anti-miR-155 (t-anti-miR-155) on multiple myeloma cell line (RPMI-8266) viability and apoptosis in vitro.

RESULTS

t-anti-miR-155 significantly inhibited multiple myeloma cell proliferation, migration, and colony formation. Additionally, t-anti-miR-155 significantly increased CD19 positive cell numbers, which are novel biomarkers for multiple myeloma and suppressor of cytokine signaling 1(SOCS1) was shown to be a target gene for miR-155 in multiple myeloma. Finally, the miR-155 signaling pathway was investigated by KEGG assay.

CONCLUSION

miR-155 in RPMI-8266 cells is a critical oncomiR in multiple myeloma and seed-targeting t-anti-miR-155 might be a novel strategy for miR-155-based therapeutics.

CD19 as a molecular target in CNS autoimmunity

Multiple sclerosis (MS) and neuromyelitis optica (NMO) are the most prevalent neuroinflammatory diseases of the central nervous system (CNS). The immunological cascade of these disorders is complex, and the exact spatial and temporal role of different immune cells is not fully understood. Although MS has been considered for many years to be primarily T cell driven, it is well established that B cells and the humoral immune response play an important role in its pathogenesis. This has long been evident from laboratory findings that include the presence of oligoclonal bands in the CSF. In NMO, the importance of the humoral immune system appears even more obvious as evidenced by pathogenic antibodies against aquaporin 4 (AQP4). Besides their capacity to mature into antibody-producing plasma cells, B cells are potent antigen-presenting cells to T lymphocytes and they can provide soluble factors for cell activation and differentiation to other immune-competent cells. In MS and NMO, there are substantial data from clinical trials that B cell depletion with CD20-directed agents is effective and relatively safe. Plasma cells, which produce antibodies against molecular targets expressed by the host, but which also provide humoral immune responses against pathogens, are not targeted by anti-CD20 therapies. Therefore, the depletion of CD19-expressing cells would offer potential advantages with regard to efficacy, but potentially higher risks with regard to infectious complications. This review will outline the rationale for CD19 as a molecular target in CNS autoimmunity. The current stage of drug development is illustrated. Potential safety concerns will be discussed.

CD19 and CD32b differentially regulate human B cell responsiveness

B cell activation is regulated by a variety of signals. CD19 positively regulates B cell activation, augmenting signals delivered through the BCR complex. In contrast, CD32b contains an ITIM and negatively regulates BCR signaling. Importantly, there are drugs currently in clinical trials and preclinical development that cross-link CD32b to molecules within the BCR complex. We wanted to address how single engagement versus cotargeting these molecules affects human B cell function. When B cells from healthy individuals were activated by signals that mimic a T cell response (IL-21 costimulation), ligation of CD32b, but not CD19, inhibited B cell expansion and plasma cell (PC) differentiation. In contrast, when B cells were activated through TLR, anti-CD19, but not anti-CD32b, blunted the response. However, when both CD19 and CD32b were coengaged by a bispecific anti-CD19×CD32b Ab, both types of stimuli were potently inhibited. Cross-linking CD19 with CD32b also inhibited Ab-independent functions of B cells, such as HLA upregulation, cytokine production, and the ability of B cells to prime CD4(+) T cells. Finally, although cross-linking CD19 and CD32b inhibited PC differentiation of primary B cells, it did not alter Ig production from pre-established PCs. These data elucidate the mechanism by which a complex set of signals determines the fate of B cell responsiveness. Although signals through CD19 influence TLR-driven activation, CD32b impacts the magnitude of the response following IL-21 costimulation. Therefore, simultaneous targeting of multiple surface molecules may be a necessary approach to comprehensively modulate B cell activation in vivo.

CAR-modified anti-CD19 T cells for the treatment of B-cell malignancies: rules of the road

INTRODUCTION

Malignancies of the B lymphocyte or its precursor include B-cell non-Hodgkin lymphoma as well as chronic and acute lymphoid leukemias. These are among the most common hematologic malignancies and many patients with B-cell malignancies are incurable. Although most patients initially respond to first-line treatment, relapse is frequent and is associated with a poor prognosis. T cells that are genetically engineered to express chimeric antigen receptors (CARs) recognizing the B-cell-associated molecule CD19 have emerged as a potentially potent and exciting therapeutic modality in recent years.

AREAS COVERED

This review explores the current peer-reviewed publications in the field and a discussion of expert opinion.

EXPERT OPINION

Genetic engineering of T cells has become clinically feasible and appears to be safe. Here we provide an insight into the process of patient selection, engineered T-cell production, infusion procedure, expected toxicities and efficacy of this exciting approach as it is practiced in the treatment of B-cell malignancies. Anti-CD19-redirected T cells likely represent the vanguard of an exciting new approach to treating cancer.

Targeting CD19 in B-cell lymphoma: emerging role of SAR3419

Non-Hodgkin lymphoma symbolizes a heterogeneous group of diseases resulting from malignant transformation of lymphocytes with differing patterns of behavior and responses to treatment. The potential curability of non-Hodgkin lymphoma differs among the various histologic subtypes and is associated in part with the stage at presentation. CD19 antigen is a type I transmembrane glycoprotein belonging to the immunoglobulin Ig superfamily. CD19 is specifically expressed in normal and neoplastic B-cells. Recent study showed that in a mouse model, CD19 and c-Myc synergize functionally to accelerate B-cell lymphomagenesis, which is associated with increased disease severity. Specificity is the most important challenge in cancer therapeutics. Antibody–drug conjugates have the prospect of enhancing the therapeutic efficacy over unconjugated monoclonal antibodies through the selective delivery of cytotoxic agents to cancer cells. The ubiquitous expression of CD19 in these tumors, especially at an earlier stage and the property of efficient internalization, makes CD19 an attractive and affective target for antibody–drug conjugate therapy as compared to CD20. SAR3419 (huB4-DM4) is a novel antibody–drug conjugate that is composed of a humanized monoclonal IgG1 anti-CD19 antibody (huB4) attached to the potent cytotoxic drug, a maytansine derivative (DM4), through a cleavable disulfide cross-linking agent N-Succinimidyl-4-2-pyridyldithio butanoic acid (SPDB). The preclinical efficacy of maytansine derivative–anti-CD19 conjugate was demonstrated in our laboratory, and SAR3419 was found to be more effective than CHOP in a xenograft model. Phase I trials have also been conducted on the basis of preclinical studies that demonstrated promising antitumor activity with acceptable safety results in human B-cell lymphoma models. Additional trials are ongoing and will provide additional insight into the full potential of this novel drug.

CD19: a biomarker for B cell development, lymphoma diagnosis and therapy

The human CD19 antigen is a 95 kd transmembrane glycoprotein belonging to the immunoglobulin superfamily. CD19 is classified as a type I transmembrane protein, with a single transmembrane domain, a cytoplasmic C-terminus, and extracellular N-terminus. CD19 is a biomarker for normal and neoplastic B cells, as well as follicular dendritic cells. CD19 is critically involved in establishing intrinsic B cell signaling thresholds through modulating both B cell receptor-dependent and independent signaling. CD19 functions as the dominant signaling component of a multimolecular complex on the surface of mature B cells, alongside complement receptor CD21, and the tetraspanin membrane protein CD81 (TAPA-1), as well as CD225. Through study of CD19 transgenic and knockout mouse models, it becomes clear that CD19 plays a critical role in maintaining the balance between humoral, antigen-induced response and tolerance induction. This review also summarized latest clinical development of CD19 antibodies, anti-B4-bR (an immunotoxin conjugate), blinatumomab (BiTE), and SAR3419 (huB4-DM4), a novel antibody-drug conjugate.

Rationale of anti-CD19 immunotherapy: an option to target autoreactive plasma cells in autoimmunity

Anti-CD20 therapy using rituximab directly targeting B cells has been approved for treatment of non-Hodgkin lymphoma, rheumatoid arthritis and anti-neutrophil cytoplasmic antibody-associated vasculitides and has led to reappreciation of B-lineage cells for anti-rheumatic treatment strategies. Moreover, blocking B-cell activating factor with belimumab, a drug that is licensed for treatment of active, seropositive systemic lupus erythematosus (SLE), represents an alternative, indirect anti-B-cell approach interfering with proper B-cell development. While these approaches apparently have no substantial impact on antibody-secreting plasma cells, challenges to improve the treatment of difficult-to-treat patients with SLE remain. In this context, anti-CD19 antibodies have the promise to directly target autoantibody-secreting plasmablasts and plasma cells as well as early B-cell differentiation stages not covered by anti-CD20 therapy. Currently known distinct expression profiles of CD19 by human plasma cell subsets, experiences with anti-CD19 therapies in malignant conditions as well as the rationale of targeting autoreactive plasma cells in patients with SLE are discussed in this review.

A c-Myc and surface CD19 signaling amplification loop promotes B cell lymphoma development and progression in mice

Malignant B cells responding to external stimuli are likely to gain a growth advantage in vivo. These cells may therefore maintain surface CD19 expression to amplify transmembrane signals and promote their expansion and survival. To determine whether CD19 expression influences this process, Eμ-Myc transgenic (c-Myc(Tg)) mice that develop aggressive and lethal B cell lymphomas were made CD19 deficient (c-Myc(Tg)CD19⁻/⁻). Compared with c-Myc(Tg) and c-Myc(Tg)CD19⁺/⁻ littermates, the median life span of c-Myc(Tg)CD19⁻/⁻ mice was prolonged by 81-83% (p < 0.0001). c-Myc(Tg)CD19⁻/⁻ mice also lived 42% longer than c-Myc(Tg) littermates following lymphoma detection (p < 0.01). Tumor cells in c-Myc(Tg) and c-Myc(Tg)CD19⁻/⁻ mice were B lineage derived, had a similar phenotype with a large blastlike appearance, invaded multiple lymphoid tissues, and were lethal when adoptively transferred into normal recipient mice. Importantly, reduced lymphomagenesis in c-Myc(Tg)CD19⁻/⁻ mice was not due to reductions in early B cell numbers prior to disease onset. In mechanistic studies, constitutive c-Myc expression enhanced CD19 expression and phosphorylation on active sites. Reciprocally, CD19 expression in c-Myc(Tg) B cells enhanced c-Myc phosphorylation at regulatory sites, sustained higher c-Myc protein levels, and maintained a balance of cyclin D2 expression over that of cyclin D3. These findings define a new and novel c-Myc:CD19 regulatory loop that positively influences B cell transformation and lymphoma progression.

Clinical consequences of defects in B-cell development

Abnormalities in humoral immunity typically reflect a generalized or selective failure of effective B-cell development. The developmental processes can be followed through analysis of cell-surface markers, such as IgM, IgD, CD10, CD19, CD20, CD21, and CD38. Early phases of B-cell development are devoted to the creation of immunoglobulin and testing of B-cell antigen receptor signaling. Failure leads to the absence of B cells and immunoglobulin in the blood from birth. As the developing B cells begin to express a surface B-cell receptor, they become subject to negative and positive selection pressures and increasingly depend on survival signals. Defective signaling can lead to selective or generalized hypogammaglobulinemia, even in the presence of normal numbers of B cells. In the secondary lymphoid organs some B cells enter the splenic marginal zone, where preactivated cells lie ready to rapidly respond to T-independent antigens, such as the polysaccharides that coat some microorganisms. Other cells enter the follicle and, with the aid of cognate follicular T cells, divide to help form a germinal center (GC) after their interaction with antigen. In the GC B cells can undergo the processes of class switching and somatic hypermutation. Failure to properly receive T-cell signals can lead to hyper-IgM syndrome. B cells that leave the GC can develop into memory B cells, short-lived plasma cells, or long-lived plasma cells. The latter ultimately migrate back to the bone marrow, where they can continue to produce protective antigen-specific antibodies for decades.

Patients referred to an indoor air health clinic: exposure to water-damaged buildings causes an increase of lymphocytes in bronchoalveolar lavage and a decrease of CD19 leucocytes in peripheral blood

BACKGROUND

Respiratory and other symptoms are often associated with exposure to microbes present in water-damaged buildings.

MATERIAL AND METHODS

We examined 82 consecutive patients referred to the Indoor Air Clinic, Helsinki University Hospital, due to symptoms suspected of having been caused by long-term exposure to water damage in the home or workplace. Exposure to water damage was assessed by building inspections and microbial analyses as needed. Bronchoalveolar lavage, lung function measurements, skin prick tests to inhalant allergens and radiological examinations were performed in all patients. Leucocyte subsets in peripheral blood were analysed in 35 patients.

RESULTS

Marked water damage was detected in the homes or workplaces of 47 (59%) patients; the remaining 34 patients formed the control group. The exposed group expressed more symptoms in total than the control group: fatigue, conjunctival symptoms, rhinitis with sinusitis, recurrent bronchitis and asthma were more common in the exposed group, but a significant difference was seen only for headache. In BAL (bronchoalveolar lavage) samples, lymphocytes represented 25% of the total cell population in non-smoking-exposed patients compared with 12% in control patients (p=0.004). In peripheral blood, CD19 leucocytes were significantly decreased in the exposed group (7.5% versus 12.3%; p<0.01).

CONCLUSIONS

Confirmed exposure to water damage was associated with an increase in symptoms. Exposure to water damage caused a significant change in the cellular composition in BAL fluid (lymphocytosis) and blood (decrease of CD19 cells). The depletion of CD19 leucocytes in peripheral blood may indicate an active immune response in the lungs.

CD21/35 promotes protective immunity to Streptococcus pneumoniae through a complement-independent but CD19-dependent pathway that regulates PD-1 expression

Humoral immunity to T cell-independent type 2 Ags (TI-2 Ag) is critical for protection against encapsulated bacteria such as Streptococcus pneumoniae. The CD21/35 receptor is thought to promote protective humoral immunity to encapsulated bacteria by enabling complement-decorated capsular polysaccharides to coligate the CD21/35-CD19 signaling complex with the B cell Ag receptor (BCR), thereby enhancing Ag-specific B cell activation. However, Ab responses to S. pneumoniae type 3 capsular polysaccharide (PPS-3) and other strong TI-2 Ags were significantly impaired in CD21/35(-/-) but not C3(-/-) or C4(-/-) mice. B cells from CD21/35(-/-) mice expressed significantly higher levels of cell surface CD19. CD21/35(-/-) B cells exhibited enhanced BCR-induced calcium responses and significantly higher expression of the inhibitory programmed death-1 (PD-1) receptor following immunization with a TI-2 Ag or BCR crosslinking. Reducing CD19 expression in CD21/35(-/-) mice normalized BCR-induced calcium responses, PD-1 induction, and PPS-3-specific IgG3 responses and restored protection during S. pneumoniae infection. PD-1 blockade also selectively rescued PPS-3-specific IgG3 responses in CD21/35(-/-) mice. Thereby, CD21/35 promotes protective humoral immunity to S. pneumoniae and other strong TI-2 Ags through a complement-independent pathway by negatively regulating CD19 expression and PD-1 induction.

Calcium signalling and cell-fate choice in B cells

Alterations in the cytosolic concentration of calcium ions (Ca2+) transmit information that is crucial for the development and function of B cells. Cytosolic Ca2+ concentration is determined by a balance of active transport and gradient-driven Ca2+ fluxes, both of which are subject to the influence of multiple receptors and environmental sensing pathways. Recent advances in genomics have allowed for the compilation of an increasingly comprehensive list of Ca2+ transporters and channels expressed by B cells. The increasing understanding of the function and regulation of these proteins has begun to shift the frontier of Ca2+ physiology in B cells from molecular analysis to determining how diverse inputs to cytosolic Ca2+ concentration are integrated in specific immunological contexts.

Defining In Vivo Transcription Factor Complexes of the Murine CD21 and CD23 Genes

The expression of the CD21 and CD23 genes is coincident with differentiation from transition 1 B cells (T1) to transition 2 B cells (T2). To define constituents controlling CD21 and CD23 expression, we conducted chromatin immunoprecipitation analyses for candidate transcription factors. We found constitutive binding of Oct-1, NFAT species, YY1, NF-kappaB-p52, Pax5, E2A, and RBP-Jkappa to CD21 sequences and NF-kappaB-p52, Pax5, NFAT species, E2A, and RBP-Jkappa to CD23 promoter sequences. Splenic T and B cell subsets displayed constitutive binding of YY1, NF-kappaB-p52, Pax5, and Oct-1 proteins to CD21 sequences in B cells but no specific binding of NFATc3 or Pax5 in T cells. Similarly, CD23 sequences demonstrated constitutive binding of NF-kappaB-p52 in splenic T and B cells but only Pax5 in B cells. Of the various NFAT species, only a subset were found forming constitutive DNA/protein complexes with the CD21, CD23, and IL-2 gene sequences. Maturing B cells in the marrow possess stable Pax5 complexes on CD19, CD21, and CD23 gene promoters in the nuclei of such cells, even though only CD19 is expressed. The similarity of genetic controlling elements between the CD21 and CD23 genes does not suggest a mechanism for alternative regulation of these genes; however, separation of splenic B cell subsets into T1, T2, marginal zone (MZ), and mature follicular B cells, followed by quantitative RT-PCR, demonstrated the lack of appreciable CD23 transcripts in CD21(+) MZ cells. We propose an alternative derivation of MZ cells as maturing directly from T1 cells, leaving CD23 transcriptionally inactive in that lineage of cells.

In vivo murine CD23 destabilization enhances CD23 shedding and IgE synthesis

To investigate the effects of in vivo CD23 destabilization on CD23 shedding and IgE production, an anti-CD23 stalk monoclonal (19G5), previously shown to enhance proteolysis of CD23 in vitro, was utilized. Compared to isotype control-treated mice, BALB/cJ mice injected with 19G5 displayed significantly enhanced serum soluble CD23 and IgE. Soluble CD23 and IgE levels were also increased in 19G5-treated C57BL/6J mice (intermediate IgE responders); however, the kinetics of the responses differed between the high (BALB/cJ) and intermediate responder mice, suggesting a potential role for CD23 in regulating IgE responder status. The 19G5-induced IgE response was dependent on IL-4 and independent of CD21 as demonstrated through use of IL-4Ralpha and CD21/35-deficient mice, respectively. Overall, the data provide a direct demonstration for CD23's role in regulating IgE production in vivo and suggest that therapies aimed at stabilizing cell surface CD23 would be beneficial in controlling allergic disease.

Complement Component C3d-Antigen Complexes Can Either Augment or Inhibit B Lymphocyte Activation and Humoral Immunity in Mice Depending on the Degree of CD21/CD19 Complex Engagement

C3d can function as a molecular adjuvant by binding CD21 and thereby enhancing B cell activation and humoral immune responses. However, recent studies suggest both positive and negative roles for C3d and the CD19/CD21 signaling complex in regulating humoral immunity. To address whether signaling through the CD19/CD21 complex can negatively regulate B cell function when engaged by physiological ligands, diphtheria toxin (DT)-C3d fusion protein and C3dg-streptavidin (SA) complexes were used to assess the role of CD21 during BCR-induced activation and in vivo immune responses. Immunization of mice with DT-C3d3 significantly reduced DT-specific Ab responses independently of CD21 expression or signaling. By contrast, SA-C3dg tetramers dramatically enhanced anti-SA responses when used at low doses, whereas 10-fold higher doses did not augment immune responses, except in CD21/35-deficient mice. Likewise, SA-C3dg (1 microg/ml) dramatically enhanced BCR-induced intracellular calcium concentration ([Ca2+]i) responses in vitro, but had no effect or inhibited [Ca2+]i responses when used at 10- to 50-fold higher concentrations. SA-C3dg enhancement of BCR-induced [Ca2+]i responses required CD21 and CD19 expression and resulted in significantly enhanced CD19 and Lyn phosphorylation, with enhanced Lyn/CD19 associations. BCR-induced CD22 phosphorylation and Src homology 2 domain-containing protein tyrosine phosphatase-1/CD22 associations were also reduced, suggesting abrogation of negative regulatory signaling. By contrast, CD19/CD21 ligation using higher concentrations of SA-C3dg significantly inhibited BCR-induced [Ca2+]i responses and inhibited CD19, Lyn, CD22, and Syk phosphorylation. Therefore, C3d may enhance or inhibit Ag-specific humoral immune responses through both CD21-dependent and -independent mechanisms depending on the concentration and nature of the Ag-C3d complexes.