Therapeutic B cell depletion and regeneration in rheumatoid arthritis: emerging patterns and paradigms

Expression of NK (CD16+56+) and B cells (CD19) Receptor Molecules as a Reliable Clinical Response Biomarkers of SLE and RA Patients Under the Rituximab Treatment

Introduction

Lately, the use of biological therapy in various autoimmune diseases is increasing. The ideal marker for monitoring the effects of modern therapy is still non-existent.

Aim

To investigate early response biomarkers of SLE and RA patients under the rituximab treatment are in research phase and each new investigations offer new and original useful data.

Material and Methods

Immunophenotyping of cells was carried out by a standard method of sample preparation. We investigated by flow cytometric analyses expression of NK and CD19+ cells at ten SLE and five RA patients before and after treatment with rituximab, in laboratory of Department of Clinical immunology in the Clinical Centre University of Sarajevo.

Results

In both cases, SLE and RA patients, reduced number of CD16+ parameter indicates lower cytotoxic activity of NK cells. Increased number of B cells indicates higher pathological activity leading to severe autoimmune disease allegation.

Conclusion

Determining the proportion of NK and B will be useful diagnostic tool in therapeutic strategy, and also in monitoring of effect of biological therapy.

Non-response to rituximab therapy in rheumatoid arthritis is associated with incomplete disruption of the B cell receptor repertoire

OBJECTIVE

To gain more insight into the dynamics of lymphocyte depletion and develop new predictors of clinical response to rituximab in rheumatoid arthritis (RA).

METHODS

RNA-based next-generation sequencing was used to analyse the B cell receptor (BCR) repertoire in peripheral blood and synovial tissue samples collected from 24 seropositive patients with RA treated with rituximab. Clonal expansion, mutation load and clonal overlap were assessed in samples collected before, at week 4 and at week 16 or 24 after treatment and correlated to the patients' clinical response.

RESULTS

After 4 weeks of rituximab-induced B cell depletion, the peripheral blood BCR repertoire of treated patients consisted of fewer, more dominant and more mutated BCR clones. No significant changes in the synovial tissue BCR repertoire were detected until week 16 post-treatment, when a reduced clonal overlap with baseline and an increased mutation load were observed. In patients who were non-responders at month 3 (n=5) using the European League Against Rheumatism response criteria, peripheral blood samples taken at week 4 after rituximab treatment showed more dominant clones compared with moderate responders (n=9) (median (IQR): 36 (27-52) vs 18 (16-26); p<0.01) and more clonal overlap with the baseline (median (IQR): 5% (2%-20%) vs 0% (0%-0%); p≤0.01).

CONCLUSION

Significant changes in BCR clonality are observed in peripheral blood of patients 4 weeks after rituximab treatment, while changes in synovial tissue were observed at later time points. Incomplete depletion of the dominant baseline peripheral blood BCR repertoire in the first month of treatment might predict clinical non-response at 3 months.

Optimization of novel reversible Bruton's tyrosine kinase inhibitors identified using Tethering-fragment-based screens

Since the approval of ibrutinib for the treatment of B-cell malignancies in 2012, numerous clinical trials have been reported using covalent inhibitors to target Bruton's tyrosine kinase (BTK) for oncology indications. However, a formidable challenge for the pharmaceutical industry has been the identification of reversible, selective, potent molecules for inhibition of BTK. Herein, we report application of Tethering-fragment-based screens to identify low molecular weight fragments which were further optimized to improve on-target potency and ADME properties leading to the discovery of reversible, selective, potent BTK inhibitors suitable for pre-clinical proof-of-concept studies.

Essential Domain-Dependent Roles Within Soluble IgG for in vivo Superantigen Properties of Staphylococcal Protein A: Resolving the B-Cell Superantigen Paradox

Staphylococcus aureus is a common commensal and frequent opportunistic pathogen that causes invasive infections that often recur. Co-evolution with the host has led to the development of toxins that affect diverse immune cell types. Recent reports have highlighted the contributions of staphylococcal protein A (SpA). This small oligomeric secreted protein contains 4–5 homologous domains with two distinct immunoglobulin-binding sites; one for IgG Fc domains, while a separate site binds an evolutionarily conserved surface on Fab encoded by VHIII clan related genes. The Fab-binding site has been implicated in in vivo supraclonal VHIII-BCR targeted B-cell depletion by an activation induced death pathway. Yet the concept of a superantigen for B lymphocytes poses a seeming paradox. Unlike TCR that are expressed only in a membrane-associated form, BCR are expressed in both a membrane BCR form and in secreted Ig forms, which permeate virtually every part of the body at high levels. We therefore asked, why circulating immunoglobulin do not block the superantigen properties of SpA? Herein, we show that soluble IgG molecules are not in vivo inhibitors of these B-cell superantigen effects but are instead essential for potentiating these properties. We also show that the Fc subclass of circulating IgG is an indirect critical determinant of the B-cell superantigen effect. In contrast, host FcγR and complement are not required for SpA mediated in vivo B-cell depletion. Unexpectedly, after VHIII-IgG2a pretreatment SpA challenge resulted in fatal anaphylactic reactions, which we speculate may have involved FcγR interactions with mast cells and basophils. Cumulatively, our findings illuminate a cunning and potent molecular strategy by which a bacterial toxin effectively confounds the contributions of host B-lymphocytes to immune defenses.

Reversing Autoimmunity Combination of Rituximab and Intravenous Immunoglobulin

In this concept paper, the authors present a unique and novel protocol to treat autoimmune diseases that may have the potential to reverse autoimmunity. It uses a combination of B cell depletion therapy (BDT), specifically rituximab (RTX) and intravenous immunoglobulin (IVIg), based on a specifically designed protocol (Ahmed Protocol). Twelve infusions of RTX are given in 6–14 months. Once the CD20⁺ B cells are depleted from the peripheral blood, IVIg is given monthly until B cells repopulation occurs. Six additional cycles are given to end the protocol. During the stages of B cell depletion, repopulation and after clinical recovery, IVIg is continued. Along with clinical recovery, significant reduction and eventual disappearance of pathogenic autoantibody occurs. Administration of IVIg in the post-clinical period is a crucial part of this protocol. This combination reduces and may eventually significantly eliminates inflammation in the microenvironment and facilitates restoring immune balance. Consequently, the process of autoimmunity and the phenomenon that lead to autoimmune disease are arrested, and a sustained and prolonged disease and drug-free remission is achieved. Data from seven published studies, in which this combination protocol was used, are presented. It is known that BDT does not affect check points. IVIg has functions that mimic checkpoints. Hence, when inflammation is reduced and the microenvironment is favorable, IVIg may restore tolerance. The authors provide relevant information, molecular mechanism of action of BDT, IVIg, autoimmunity, and autoimmune diseases. The focus of the manuscript is providing an explanation, using the current literature, to demonstrate possible pathways, used by the combination of BDT and IVIg in providing sustained, long-term, drug-free remissions of autoimmune diseases, and thus reversing autoimmunity, albeit for the duration of the observation.

Consequences of B-cell-depleting therapy: hypogammaglobulinemia and impaired B-cell reconstitution

Rituximab is a chimeric monoclonal antibody used to treat hematologic and autoimmune diseases by depleting CD20-expressing B cells. Patients may develop hypogammaglobulinemia following treatment, with some demonstrating failure of B-cell recovery. The true frequency of hypogammaglobulinemia and/or impaired B-cell reconstitution post rituximab is unknown due to the lack of prospective studies in different patient cohorts. The clinical significance remains controversial; some patients have recurrent infections while others are relatively asymptomatic. The aim of this review is to describe the prevalence of hypogammaglobulinemia and the associated risk for developing severe infection, in patients with differing underlying clinical conditions treated with rituximab. This may facilitate classification and prognostication of patients who develop these conditions and identify patients who may be at high risk of developing these complications, including those who may benefit from immunoglobulin replacement therapy.

Tuberculosis and biologics in rheumatology: A special situation

India has a huge patient burden of rheumatic diseases (RDs) including rheumatoid arthritis. The use of biologics has transformed the treatment paradigm for RD; however, biologic treatment-related infections (especially tuberculosis [TB]) are an area of potential concern for TB-endemic nations like India. Anti-tumor necrosis factor (TNF) therapy impairs the physiological TNF-mediated signaling and may cause reactivation and dissemination of latent TB infection (LTBI). Careful screening is, thus, crucial in RD patients who are about to commence anti-TNF treatment. To date, there is no consensus available for the screening, evaluation and treatment of LTBI as well as on the drug dosage and duration regimen (monotherapy or combination therapy) in the Indian population. An evidence-based algorithm for LTBI screening and management in RD patients undergoing biologic disease-modifying anti-rheumatic drug therapy is suggested in this review for Indian rheumatologists. The proposed algorithm guides physicians through a step-wise screening approach, including medical history, tuberculin skin test, interferon gamma release assay, chest radiograph and management of LTBI with isoniazid therapy or its combination with rifampicin. Further, the provided algorithm can aid the national bodies (such as National TB Control Program) in formulating recommendations for LTBI in this high-risk population.

Pathogenesis and potential therapeutic targets in systemic lupus erythematosus: from bench to bedside

Systemic lupus erythematosus (SLE) is considered an autoimmune disease with multiorgan involvement. Many advances have been made during the last decade regarding inflammatory pathways, genetic and epigenetic alterations, adaptive and innate immune system mechanisms specifically involved in SLE pathogenesis. Apoptosis has been proposed as an important player in SLE pathogenesis more than a decade ago. However, only recently new key apoptotic pathways have been investigated and the link between apoptotic debris containing autoantigens, innate immunity and ongoing inflammation has been further elucidated. Better understanding of cellular mechanisms and involved cytokines contributed to the development of new biological drugs specifically addressed for SLE therapy.

B cells regulate macrophage phenotype and response to chemotherapy in squamous carcinomas

B cells foster squamous cell carcinoma (SCC) development through deposition of immunoglobulin-containing immune complexes in premalignant tissue and Fcγ receptor-dependent activation of myeloid cells. Because human SCCs of the vulva and head and neck exhibited hallmarks of B cell infiltration, we examined B cell-deficient mice and found reduced support for SCC growth. Although ineffective as a single agent, treatment of mice bearing preexisting SCCs with B cell-depleting αCD20 monoclonal antibodies improved response to platinum- and Taxol-based chemotherapy. Improved chemoresponsiveness was dependent on altered chemokine expression by macrophages that promoted tumor infiltration of activated CD8(+) lymphocytes via CCR5-dependent mechanisms. These data reveal that B cells, and the downstream myeloid-based pathways they regulate, represent tractable targets for anticancer therapy in select tumors.

ZAP-70+ B cell subset influences response to B cell depletion therapy and early repopulation in rheumatoid arthritis

OBJECTIVE

To define the role of ZAP-70+ B cells (CD19+/ZAP-70+) as a biomarker of response to B cell depletion therapy (BCDT), their relationship with clinical outcome, and their behavior during repopulation of peripheral blood in patients with rheumatoid arthritis (RA).

METHODS

Thirty-one patients with RA underwent BCDT and were followed for 12 months. Disease activity was assessed with the European League Against Rheumatism (EULAR) criteria. Cytofluorimetric analysis of peripheral blood B cell subsets at baseline and at 6- and 12-month intervals after BCDT was performed using surface markers (CD45, CD3, CD56, CD19, IgD, CD38, CD27) and intracellular ZAP-70.

RESULTS

A moderate/good EULAR response was achieved in 66.6% of the RA cohort. The baseline percentage of CD19+/ZAP-70+ cells was lower in good responder patients (1.8% ± 1.7%) compared to poor responders (5.6% ± 4.9%; p = 0.02). A decrease of plasmablasts (IgD-CD27+CD38+) and pre-switch memory (IgD+CD27+) B cells occurred after BCDT. Recovery of B cells in peripheral blood after the first course of BCDT was characterized by the reappearance of B cell subtypes that showed a naive, activated phenotype, coupled with a decrease in memory cells. B cells carrying intracytoplasmic ZAP-70 increased significantly from the baseline value of 4.4% ± 4.5% to 12.4% ± 9.2% (p = 0.001) at the 6-month and to 9.4% ± 6.4% (p = 0.002) at the 12-month followup.

CONCLUSION

Baseline percentage of CD19+/ZAP-70+ cells is associated with the clinical outcome after BCDT in patients with RA. Depletion of plasmablasts and pre-switch memory B cells and increase of CD19+/ZAP-70+ cells are features of the recovery of the B cell pool after BCDT.

Biomarkers of good EULAR response to the B cell depletion therapy in all seropositive rheumatoid arthritis patients: clues for the pathogenesis

Objective

To find out whether a high number of auto-antibodies can increase the probability of a “good-EULAR response” and to identify the possible biomarkers of response in seropositive rheumatoid arthritis (RA) patients undergoing the B cell depletion therapy (BCDT).

Patients and Methods

One hundred and thirty-eight patients with long standing RA (LSRA), 75% non or poorly responsive to one or more TNFα blockers, all seropositive for at least one autoantibody (AAB) (RF-IgM, RF-IgA, RF-IgG, anti-MCV, ACPA-IgG, ACPA-IgA, ACPA-IgM) received one full course of BCDT. The major outcomes (moderate or good-EULAR response) were assessed after 6 months of therapy. The IL6 and BAFF levels were also determined.

Results

At a 6-month follow-up, 33 (23.9%) of the RA patients achieved a good EULAR response. Having up to 5-AABs positivity increased the chances for treatment response. After a logistic regression analysis, however, only 4 baseline factors arose as associated with a good-EULAR response: no steroid therapy (OR = 6.25), a lymphocyte count <1875/uL (OR = 10.74), a RF-IgG level >52.1 IU/ml (OR = 8.37) and BAFF levels <1011 pg/ml (OR = 7.38). When all the AABs, except for RF-IgM and ACPA-IgG, were left in the analysis, the two final predictors were no-steroid therapy and low lymphocyte count.

Discussion

The number of AABs increased the chances of being a “good-EULAR” responder. The only predictors, however, at the baseline of a good response in this seropositive cohort of RA patients were 2 simple variables – no steroids and lymphocyte count – and two laboratory assays – IgG-RF and BAFF.

Biologics-based therapy for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) remains a major clinical problem, but treatments involving biologics have revolutionized its management. They target pathogenically relevant cytokines such as tumor necrosis factor and immune cells such as B cells. In RA, biologics reduce joint inflammation, limit erosive damage, decrease disability, and improve quality of life. Infections are the main risk associated with their use. Because of the high prices of biologics, their cost-effectiveness is a matter of debate. They are mainly coadministered with disease-modifying drugs such as methotrexate when the latter are found to achieve insufficient disease control on their own.

Atacicept: targeting B cells in multiple sclerosis

Multiple sclerosis (MS) has traditionally been considered to be a T-cell-mediated disease. However, there is an increasing body of evidence for the involvement of B cells and autoantibodies in the pathology of this disease, providing a rationale for treatments directed against B cells. In this paper we summarize evidence for the key role of B cells in the immunopathology of MS and review data supporting the use of a novel B-cell targeted therapy, atacicept, in this condition. Atacicept is a human recombinant fusion protein that comprises the binding portion of a receptor for both BLyS (B-Lymphocyte Stimulator) and APRIL (A PRoliferation-Inducing Ligand), two cytokines that have been identified as important regulators of B-cell maturation, function and survival. Atacicept has shown selective effects on cells of the B-cell lineage, acting on mature B cells and blocking plasma cells and late stages of B-cell development while sparing B-cell progenitors and memory cells. The efficacy of atacicept in animal models of autoimmune disease and the biological activity of atacicept in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) has been demonstrated. Clinical studies were initiated to investigate the safety, tolerability and efficacy of atacicept in patients with MS. An unexpected increase in inflammatory activity in one of the trials, however, led to suspension of all atacicept trials in MS.

Targeting the B cell in rheumatoid arthritis

There has been renewed interest in the B cell as a target for the treatment of rheumatoid arthritis (RA) over the past decade. Efficacy with rituximab has been demonstrated in randomised clinical trials (RCTs) resulting in regulatory approval for patients failing tumour necrosis factor (TNF) inhibitors. Although the actual mechanism of action has not been clearly delineated, several molecules are under development to modify B cell number/function in hope of superior efficacy/safety or ease of administration. The safety of rituximab over the intermediate time point has been comparable to that seen with other biologic disease-modifying anti-rheumatic drugs (DMARDs). The recent report of cases of progressive multifocal leukoencephalopathy in three patients receiving rituximab for RA is a concern and, for now, limits rituximab to salvage therapy for the treatment-resistant patient. How this impacts on other B-cell inhibitors under development is not yet clear. Development of biomarkers that will assist our therapeutic decisions to enhance the benefit/risk ratio for our patients are needed as we move forward with further selective targeted therapies.

A double-edged sword in B-cell-targeted therapy for inflammatory diseases

Cells of the immune system, including B cells, perform inflammatory functions against microbial invasion, accompanied by anti-inflammatory responses to avoid host damage. B-cell-depletion therapy using anti-CD20 monoclonal antibodies against inflammatory diseases has beneficial or adverse effects depending on the timing and/or microenvironment in which they are used. To achieve effective B-cell-targeted therapy, it is necessary to identify and understand the modes of action of pathogenic and regulatory B cells, which include antibody production, formation of immune complexes, cytokine and chemokine production, cytotoxic killing, lymphoid neogenesis and antigen presentation. B cells interact with multiple cells, including dendritic cells, T cells and natural killer T cells, creating a complex regulatory network. Specific targeting of B-cell subsets and/or their interaction partners might lead to clinical benefits with minimal host damage.

[Atacicept: a new B lymphocyte-targeted therapy for multiple sclerosis]

Multiple sclerosis (MS) has traditionally been considered to be a T cell-mediated disease. However, there is an increasing body of evidence for the involvement of B cells and autoantibodies in the pathology of this disease, providing a rationale for treatment strategies directed against B cells. This paper summarizes the evidence for a key role of B cells in the immunopathology of MS and reviews data supporting the use of a novel B cell-targeted therapy, atacicept, for this condition. Atacicept is a human recombinant fusion protein that comprises the binding portion of a receptor for both BLyS (B Lymphocyte Stimulator) and APRIL (A PRoliferation-Inducing Ligand), two cytokines that have been identified as important regulators of B cell maturation, function and survival. Atacicept has shown selective effects on cells of the B cell lineage, acting on mature B cells and blocking plasma cells and late stages of B cell development while sparing B cell progenitors and memory cells. The efficacy of atacicept in animal models of autoimmune disease and the biological activity of atacicept in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) has been demonstrated. Ongoing clinical studies are investigating the safety, tolerability and efficacy of atacicept in patients with MS, SLE and RA.

Translational Mini-Review Series on B Cell-Directed Therapies: Recent advances in B cell-directed biological therapies for autoimmune disorders

B cell-directed therapies are promising treatments for autoimmune disorders. Besides targeting CD20, newer B cell-directed therapies are in development that target other B cell surface molecules and differentiation factors. An increasing number of B cell-directed therapies are in development for the treatment of autoimmune disorders. Like rituximab, which is approved as a treatment for rheumatoid arthritis (RA), many of these newer agents deplete B cells or target pathways essential for B cell development and function; however, many questions remain about their optimal use in the clinic and about the role of B cells in disease pathogenesis. Other therapies besides rituximab that target CD20 are the furthest along in development. Besides targeting CD20, the newer B cell-directed therapies target CD22, CD19, CD40-CD40L, B cell activating factor belonging to the TNF family (BAFF) and A proliferation-inducing ligand (APRIL). Rituximab is being tested in an ever-increasing number of autoimmune disorders and clinical studies of rituximab combined with other biological therapies are being pursued for the treatment of rheumatoid arthritis (RA). B cell-directed therapies are being tested in clinical trials for a variety of autoimmune disorders including RA, systemic lupus erythematosus (SLE), Sjögren's syndrome, vasculitis, multiple sclerosis (MS), Graves' disease, idiopathic thrombocytopenia (ITP), the inflammatory myopathies (dermatomyositis and polymyositis) and the blistering skin diseases pemphigus and bullous pemphigoid. Despite the plethora of clinical studies related to B cell-directed therapies and wealth of new information from these trials, much still remains to be discovered about the pathophysiological role of B cells in autoimmune disorders.

Rituximab in severe lupus nephritis: early B-cell depletion affects long-term renal outcome

BACKGROUND AND OBJECTIVES

Standard treatment for lupus nephritis, including corticosteroids and cyclophosphamide, is efficient but is still associated with refractory or relapsing disease, or severe deleterious effects. Rituximab, a monoclonal chimeric anti-B cell antibody, is increasingly used in patients with lupus nephritis, but reported series were small and had a short follow-up.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The authors analyzed clinical and histologic data of 20 patients who were treated with rituximab for lupus nephritis and followed up for at least 12 mo.

RESULTS

Nineteen women and one man received rituximab as induction treatment for an active class IV (15 cases) or class V (5 cases) lupus nephritis. Rituximab was given for lupus nephritis refractory to standard treatment (12 cases), for relapsing disease (6 cases), or as first-line treatment (2 cases). Three patients received cyclophosphamide concomitantly with rituximab. Ten received new injections of rituximab as maintenance therapy. Side effects included mainly five infections and four moderate neutropenias. After a median follow-up of 22 mo, complete or partial renal remission was obtained in 12 patients (60%). Lupus nephritis relapsed in one patient, who responded to a new course of rituximab. The achievement of B cell depletion 1 mo after rituximab, which negatively correlated with black ethnicity and hypoalbuminemia, was strongly associated with renal response. Rapidly progressive glomerulonephritis did not respond to rituximab.

CONCLUSION

Rituximab is an interesting therapeutic option in relapsing or refractory lupus nephritis when early B cell depletion is obtained.

Modulation of molecular imprints in the antigen-experienced B cell repertoire by rituximab

OBJECTIVE

Transient B cell depletion by rituximab has recently gained more importance in the treatment of rheumatic disorders. Nevertheless, little is known about the reemerging B cells. We analyzed dynamic changes in the repopulating B cells, particularly the postswitch B cells, and studied the mutational patterns of Ig genes in antigen-experienced B cells.

METHODS

Five patients with active rheumatoid arthritis (RA) were treated with rituximab. In 3 patients, B cell receptor (BCR) gene analysis was performed before treatment and during B cell recovery using genomic DNA. In 2 patients, B cell subsets were studied during the early recovery phase using single-cell technology. For comparison, immunophenotyping of B cell subsets was performed.

RESULTS

Early B cell recovery was marked by a relatively expanded population of highly mutated B cells, which were correlated with B cells with a plasmablast phenotype on comparative immunophenotyping. Analysis of the mutational pattern in these cells revealed increased RGYW/WRCY (where R = A/G, Y = C/T, and W = A/T) hotspot targeting (44% before rituximab versus 59% after) and elevated ratios of replacement to silent mutations within the complementarity-determining regions in Ig genes (1.87 before rituximab versus 2.67 after; P < or = 0.0025).

CONCLUSION

Our findings show that rituximab leads to qualitative changes in the imprints of highly mutated, antigen-experienced BCRs, representing the result of selection, whereas molecular processes such as Ig V rearrangements are not affected by this treatment.

Polarized immune responses differentially regulate cancer development

Tumor-associated immune responses assert varied responses toward developing neoplasms that can either act to eradicate malignant cells via engagement of potent cytotoxic programs or alternatively enhance tumor growth through release of multifunctional pro-tumor mediators. Seemingly paradoxical, these disparate activities reflect a continuum of polarization (or activation) states possible for distinct leukocyte subsets that demonstrate tissue, organ, and tumor selectivity. Herein, we review clinical and experimental studies investigating cellular and molecular mechanisms utilized by neoplastic tissues to alternatively polarize immune responses that favor either pro- or anti-tumor immunity.

Anti-CD20 therapy in patients with rheumatoid arthritis: predictors of response and B cell subset regeneration after repeated treatment

OBJECTIVE

B cell depletion with the anti-CD20 antibody rituximab has proven efficacy in patients with rheumatoid arthritis (RA). The effects on B cell homeostasis after repeated treatments and the relationship of certain B cell subsets to clinical response or relapse are currently not known.

METHODS

In this open-label study, 17 patients with RA refractory to standard therapy were treated with 1 cycle of rituximab. Of these 17 patients, 11 received a second cycle of rituximab therapy. Immunophenotyping was performed before therapy and during B cell recovery.

RESULTS

Twelve of 17 patients showed a good European League Against Rheumatism response after receiving 1 cycle of rituximab therapy. At the time of B cell recovery, the IgD+,CD27+ memory B cell subset was significantly larger (P = 0.019) in the nonresponder group. Within the group of 12 responders, 6 patients, whose disease was characterized by a significantly higher proportion of overall CD27+ memory B cells before therapy, experienced an early relapse (weeks 24-40 posttreatment). Eleven patients were re-treated, again resulting in a good clinical response. B cell reconstitution followed a similar pattern after each cycle. The early reconstitution phase was characterized by immature CD38++,IgD+,CD10+ B cells, whereas the number of naive B cells increased continuously thereafter. The number of memory B cells was still reduced at the time of the second depletion but recovered to levels similar to those following the first cycle of therapy.

CONCLUSION

Data derived from repeated B lymphocyte depletion with rituximab in patients with RA suggest that analysis of certain memory B cell subsets provides information on efficacy, response, and late as well as early relapse, consistent with the conclusion that targeting memory B cells is a key to its mechanism of action.

Pharmacokinetics and biological activity of atacicept in patients with rheumatoid arthritis

Atacicept is a recombinant fusion protein containing the extracellular ligand-binding portion of the transmembrane activator and CAML interactor (TACI, CD267) receptor and inhibits B lymphocyte stimulator (BLyS, CD257) and a proliferation-inducing ligand (APRIL, CD256), both potent stimulators of B cell maturation, proliferation, and survival. Atacicept pharmacokinetics and pharmacodynamics were assessed in a double-blind, placebo-controlled, phase I study in patients with active, moderate to severe rheumatoid arthritis receiving atacicept either as a single subcutaneous or repeated, every other week dose. Pharmacokinetic profiles were determined by measuring serum concentrations of free atacicept and its complex with BLyS. Nonspecific immunoglobulin (Ig)M, IgG, and IgA; IgM-RF (rheumatoid factor), IgG-RF, and IgA-RF antibody levels; and B cell profiles provided markers of biological activity. Pharmacokinetic, biological activity, and relationships between atacicept dose and Ig antibody response were evaluated. Pharmacokinetic profiles of atacicept were nonlinear, influenced by saturable binding with its ligands, but were consistent and predictable. Atacicept treatment reduced Ig and RF serum concentration. IgM antibody levels were most sensitive to atacicept, followed by IgA and IgG, underlining the biological activity of atacicept in patients with rheumatoid arthritis. These findings can be used to explore dosing regimen design scenarios in future studies.

Immunohistochemical analysis as a means to predict responsiveness to rituximab treatment

OBJECTIVE

Anti-CD20-mediated B cell depletion with rituximab is a new and effective therapy for rheumatoid arthritis (RA). Although B cells in peripheral blood (PB) are consistently depleted in all patients, the clinical effects are more heterogeneous, possibly related to differences in the depleting effects of lymphoid or solid tissues. The aim of this study was to investigate B cell depletion in different compartments (PB, bone marrow, and synovium) and determine predictive variables for responsiveness to rituximab therapy.

METHODS

Before and 12 weeks after rituximab treatment, samples of PB, bone marrow, and synovium were collected from 25 patients with RA refractory to disease-modifying antirheumatic drugs and tumor necrosis factor-blocking agents. CD19+ and CD20+ B cells in PB and bone marrow were measured by flow cytometric analysis, whereas CD79a+ and cytoplasmic CD20+ B cells in the synovium were stained by immunohistochemistry. The effects of rituximab on serum Ig and autoantibodies were measured by enzyme-linked immunosorbent assay.

RESULTS

Rituximab effectively depleted the CD20+ subset of B cells in the PB, bone marrow, and synovium of RA patients. Rituximab significantly reduced autoantibody production (anti-citrullinated protein antibodies [ACPAs] and rheumatoid factor [RF]), in part due to a nonspecific decrease in total Ig production. Importantly, positivity for circulating ACPA IgM, in combination with a high infiltration of CD79a+ B cells in the synovium, but not of CD138+ plasma cells, was a predictor of clinical outcome after rituximab treatment. ACPA IgM titers were independently associated with synovial infiltration of CD20-,CD79a+ B cells, but not with CD138+ plasma cells.

CONCLUSION

These data provide novel insights into the mechanisms of CD20-mediated B cell depletion in the lymphoid and solid tissues of RA patients and suggest a pivotal role for ACPA IgM-producing plasmablasts in RA.

B cells and tertiary lymphoid organs in renal inflammation

B lymphocytes are part of the inflammatory cells recruited to the human kidney in various disease settings. B cell infiltrates have been described in renal allografts, in acute and chronic interstitial nephritis, and the most common glomerular diseases like immunoglobulin A (IgA) and membranous nephropathy. These cells are almost exclusively recruited to the tubulointerstitium, but not the glomerular tuft. In addition to diffuse tubulointerstitial infiltrates, B cells together with T cells and dendritic cells form organized nodular aggregates surrounded by neo-lymphatic vessels. The functional significance of these tertiary lymphoid organs remains to be fully defined. Intrarenal B cells may be part of a local system to enhance the immunological response by functioning as antigen presenting cells, and as a source for cytokines promoting T-cell proliferation and lymphatic neoangiogenesis. In this way, they could enhance the local immune response to persisting autoantigens in the tubulointerstitium.

Anti-BR3 antibodies: a new class of B-cell immunotherapy combining cellular depletion and survival blockade

Removal of pathogenic B lymphocytes by depletion of monoclonal antibodies (mAbs) or deprivation of B-cell survival factors has demonstrated clinical benefit in both oncologic and immunologic diseases. Partial clinical responses and emerging data demonstrating incomplete B-cell depletion after immunotherapy fuels the need for improved therapeutic modalities. Lessons from the first generation of therapeutics directed against B-cell-specific antigens (CD20, CD22) are being applied to develop novel antibodies with additional functional attributes. We describe the generation of a novel class of B-cell-directed therapy (anti-BR3 mAbs) that combines the depleting capacity of a therapeutic mAb and blockade of B-cell-activating factor (BAFF)-BR3 B-cell survival. In mice, treatment with antagonistic anti-BR3 antibodies results in quantitatively greater reduction in some B-cell subsets and qualitatively different effects on bone marrow plasma cells compared with BR3-Fc BAFF blockade or with anti-CD20 treatment. Comparative analysis of BR3-Fc and anti-BR3 mAb reveals a lower B-cell dependence for BAFF-mediated survival in nonhuman primates than in mice. This novel class of B-cell-targeted therapies shows species characteristics in mice and primates that will guide translation to treatment of human disease.

Role of chemokines for the localization of leukocyte subsets in the kidney

Chemokines comprise a family of structurally related chemotactic proteins. They bind to about 20 corresponding receptors. Chemokines provide a general communication system for cells, and regulate lymphocyte migration under normal (homeostatic) and inflammatory conditions. Chemokines organize microenvironments in lymphoid tissue, lymphoid organogenesis, and participate in vascular and lymphatic angiogenesis. Expressed at the site of injury in the kidney, chemokines are involved in the recruitment of specific leukocyte subsets to particular renal compartments. Here we summarize recent data on chemokine biology with a focus on the role of chemokines in the recruitment of neutrophils (polymorphonuclear leukocytes), monocytes/macrophages, dendritic cells, T cells, including regulatory T cells, and B cells in renal inflammation.

B cell modulation in rheumatology

While evidence of dysregulation of the B cell compartment was first demonstrated with the identification of autoantibodies, other functional roles of B lymphocytes in autoimmune pathogenesis have generally been underappreciated or completely overlooked. With the recent approval of the first B cell targeting agent in rheumatoid arthritis, new strategies are being developed to target B cells through a range of membrane-associated lineage-specific molecules and also by interfering with B-cell-specific pro-survival signals. B-cell-directed agents therefore provide an effective new mechanistic approach to treatment and also enable new perspectives from the dissection of the contributions of B cells in physiologic and pathologic immune responses.

Assessment of rituximab's immunomodulatory synovial effects (ARISE trial). 1: clinical and synovial biomarker results

OBJECTIVE

Treatment with the anti-CD20 monoclonal antibody (mAb) rituximab is effective in rheumatoid arthritis (RA). Marked depletion of circulating B cells, seen in almost all patients, does not correlate with efficacy. The potential synovial immunomodulatory effects of rituximab have not been fully defined.

METHODS

The ARISE trial is an open label, serial synovial biopsy (pre-treatment and 8 weeks) study of rituximab, given 1 g intravenously on days 0 and 14 without peri-infusional steroids, in active RA patients on concomitant methotrexate (MTX). Synovial tissue was analysed by immunohistochemistry with digital image analysis and gene expression by real-time PCR.

RESULTS

The mean (SD) baseline DAS28 score was 6.5 (0.4), and mean MTX dose 17.3 mg/week. Of 13 patients, 11 had failed prior tumour necrosis factor (TNF) inhibitor therapy. With treatment, all patients experienced near complete depletion of circulating B cell numbers. During the 6 months after treatment, 7/13 patients achieved an American College of Rheumatology (ACR) 20% improvement (ACR20) response, 3/13 an ACR50 response and 2/13 an ACR70 response. There was a significant decrease in synovial B cells after treatment, but only a small trend towards greater reduction among clinical responders. Among the three patients with ACR50 responses there was a significant decrease in synovial immunoglobulin synthesis.

CONCLUSIONS

These data suggest that unlike those in circulation, synovial B cells are decreased but are not eliminated by rituximab therapy. Patients with higher levels of response may have more consistent depletion of synovial B cells, and may also have an alteration in synovial B cell function, as indicated by decreases in synovial immunoglobulin synthesis. Thus, effects on synovial B cells may be necessary but not sufficient for inducing clinical efficacy. Other effects, such as on primary lymph organ B cell antigen presentation or cytokine production, may be operative.

What is the role of rituximab in the treatment of rheumatoid arthritis?

Rituximab is a monoclonal antibody against CD20 that was developed for the treatment of relapsed or refractory B-cell non-Hodgkin's lymphoma (NHL). Recent controlled trials have shown that B cell-targeted therapy with rituximab is effective in RA (which suggest that B lymphocytes may be critical in its pathogenesis of RA) and early exposure data suggest that the tolerability and safety profile of rituximab may be even better in RA than in NHL patients. Rituximab is generally well tolerated, with a low incidence of serious adverse events, including serious infections. Available evidence suggests that its clinical benefits depend on effective B cell depletion, and the fact that its novel mode of action leads to the depletion of B cells makes it distinct from other biological therapies for RA that target T cells and their related cytokines. Although complete peripheral B cell depletion is regularly seen in RA and other autoimmune diseases, especially systemic lupus erythematosus (SLE), incomplete depletion has been reported in a subset of patients, even after full dosing with rituximab.

B cell targeted therapy in autoimmunity

Autoimmunity results from a break in self-tolerance involving humoral and/or cell-mediated immune mechanisms. Part of the pathological consequence of a failure in central and/or peripheral tolerance, results from survival and activation of self-reactive B cells. Such B cells produce tissue-damaging pathogenic autoantibodies, and subsequent formation of complement-fixing immune complexes that contribute to tissue damage. Current pharmacological strategies for treating autoimmune diseases involve global use of broad-acting immunosuppressants that with long term use have associated toxicities. The present drive in drug development is towards therapies that target a specific biological pathway or pathogenic cell population. This review focuses on some of the emerging therapies based on co-stimulation blockers, and compounds which contribute to a specific B cells depletion, based on studies in animal models and human clinical studies.

Humoral immunity, inflammation and cancer

Clinical and experimental data now clearly indicate that chronic inflammation significantly contributes to cancer development. Emerging out of these studies is an appreciation that persistent humoral immune responses exacerbate recruitment and activation of innate immune cells in neoplastic microenvironments where they regulate tissue remodeling, pro-angiogenic and pro-survival pathways that together potentiate cancer development. Population-based studies examining individuals with chronic inflammatory disorders have revealed that states of suppressed cellular immunity, in combination with enhanced humoral immunity and humoral immunity-associated cytokines, cooperate and effectively suppress anti-tumor immune responses while simultaneously enhancing angiogenesis and presumably overall cancer risk in afflicted tissue. In addition, studies in transgenic mouse models of de novo organ-specific cancer development have revealed that inflammation mediated by immunoglobulins and immune complexes might be functionally significant parameters of tumor promotion and progression. These recent advances support the hypothesis that enhanced states of local humoral and innate immune activation, in combination with suppressed cellular immunity and failed cytotoxic T cell anti-tumor immunity, alter cancer risk and therefore represent powerful targets for anti-cancer immunotherapeutics.

Biologic therapies in rheumatology: lessons learned, future directions

During the past decade biologic therapies such as monoclonal antibodies and fusion proteins have revolutionized the management of rheumatic disease. By targeting key cytokines and immune cells biologics have provided more specific therapeutic interventions with less immunosuppression. Clinical use, however, has revealed that their theoretical simplicity hides a more complex reality. Efficacy, toxicity and even pharmacodynamic effects can deviate from those predicted, as poignantly illustrated by the catastrophic effects witnessed during the first-into-human administration of TGN1412. This review summarizes lessons gleaned from practical experience and discusses how these can inform future discovery and development of new biologic therapies for rheumatology.