Sustained improvement in rheumatoid arthritis following a protocol designed to deplete B lymphocytes

Engagement of the CD137 (4-1BB) costimulatory molecule inhibits and reverses the autoimmune process in collagen-induced arthritis and establishes lasting disease resistance

Agonistic antibodies against CD137 act as costimulators in the activation of CD8 T cells. They enhance the immune response against syngeneic tumour grafts and suppress T cell-dependent humoral immune responses in vivo. The present study was undertaken to determine whether suppression of antibody production by anti-CD137 mAb affects the development of collagen-induced arthritis (CIA). Male DBA/1J mice were immunized with bovine collagen II (CII) and treated with an agonistic anti-CD137 mAb or an isotype-matched control mAb. Mice were assessed regularly for macro- and microscopic signs of arthritis and for the appearance of collagen-specific antibody production. Interferon (IFN)-gamma determination, FACS analysis of splenocytes and histopathological joint examinations were performed after the animals were killed. Administration of anti-CD137 mAb at the time of collagen immunization blocked the development of disease and inhibited the humoral immune response against CII. Agonistic anti-CD137 mAb exhibited therapeutic efficacy even after the immune response to CII had succeeded and the disease became apparent. Furthermore, it induced a protective memory in the animals, enabling resistance to subsequent challenges with the pathogenic antigen. Our results suggest a key role for CD137 in the pathogenesis of CIA. This model provides insights into immunoregulatory conditions that control the pathogenesis of autoimmune diseases.

B Lymphocyte signaling established by the CD19/CD22 loop regulates autoimmunity in the tight-skin mouse

Systemic sclerosis (SSc) is characterized by fibrosis and autoimmmunity. Peripheral blood B cells from SSc patients specifically overexpress CD19, a critical cell-surface signal transduction molecule in B cells. CD19 deficiency in B cells also attenuates skin fibrosis in the tight-skin (TSK/+) mouse, a genetic model for SSc. Herein we analyzed two transgenic mouse lines that overexpress CD19. Remarkably, 20% increase of CD19 expression in mice spontaneously induced SSc-specific anti-DNA topoisomerase I (topo I) antibody (Ab) production, which was further augmented by 200% overexpression. In TSK/+ mice overexpressing CD19, skin thickness did not increase, although anti-topo I Ab levels were significantly augmented, indicating that abnormal CD19 signaling influences autoimmunity in TSK/+ mice and also that anti-topo I Ab does not have a pathogenic role. The molecular mechanisms for abnormal CD19 signaling were further assessed. B-cell antigen receptor crosslinking induced exaggerated calcium responses and augmented activation of extracellular signal-regulated kinase in TSK/+ B cells. CD22 function was specifically impaired in TSK/+ B cells. Consistently, CD19, a major target of CD22-negative regulation, was hyperphosphorylated in TSK/+ B cells. These findings indicate that reduced inhibitory signal provided by CD22 results in abnormal activation of signaling pathways including CD19 in TSK/+ mice and also suggest that this disrupted B cell signaling contribute to specific autoantibody production.

Role of chemokines in the development of secondary and tertiary lymphoid tissues

Organogenesis of lymph nodes and Peyer's patches is initiated during embryonic development and depends on the correct expression of a wide variety of molecules. Essential for this process is the paracrine triggering of stromal cells by CD45+CD4+CD3- cells. Hereto CD45+CD4+CD3- cells and stromal cells need to be spatially positioned in close proximity to each other. Expression of adhesion molecules and chemokines is thought to be essential for this process. During adult life, similar processes might also be at the basis of development of organized tertiary lymphoid structures often seen in inflammatory lesions.

B lymphocyte depletion therapy with rituximab in rheumatoid arthritis

B lymphocyte depletion therapy in rheumatoid arthritis can provide major clinical benefits. Widespread use in the future will depend on continued evidence of safety, particularly in the context of long term use. Rituximab is a highly effective agent, but it may be best used in combination with other agents. Substantial improvement following a single course of therapy has been found to last up to 42 months, and it is reasonable to hope that further development of strategies targeting B cells will extend this toward the original aim of truly long-term remission.

Apoptotic Effect of Rituximab on Peripheral Blood B Cells in Rheumatoid Arthritis

Rituximab (RTX) has proven efficacious in the treatment of rheumatoid arthritis (RA). Herein, we assessed the apoptosis-inducing capability of RTX in vitro on RA peripheral blood B-cell subsets and also compared the effects of RTX on B cells from rheumatoid factor-positive (RF+) and RF- patients. The likely relevance of B cells in disease was assessed by measuring B-cell-modulating serum cytokines. Peripheral blood B cells were isolated and cultured with the presence or absence of RTX. The levels of apoptosis within the naïve, memory and IgD+CD27+ B-cell subpopulations were determined by cytofluorometric analysis and caspase 3/7 assays. Levels of serum cytokines were measured with a multiplex cytokine array system. RTX induced significant apoptosis in all B-cell subsets in both RA and controls. In naïve and memory B cells from RA patients, RTX induced significantly higher levels of apoptosis than in controls. RTX induced apoptosis of B cells in RF+ and RF- patients. Serum levels of interleukin-1beta (IL-1beta), IL-4, IL-10 and IL-13 were profoundly increased in RF+ patients compared to RF- patients and controls. Although our cohort was small (10 RA patients), the data suggest that RTX induces apoptosis in all investigated subsets of B cells from RA patients. Interestingly, memory B cells from RA patients were more sensitive to RTX than memory cells from normal controls, suggesting that the delay in treatment response to RTX observed in clinical trials may be due in part to memory cell depletion. The apoptotic effects of RTX were similar in RF+ and RF- patients, but serum levels of B-cell-activating cytokine levels were only elevated in RF+ but not RF- patients. These data suggest that RTX is less effective in RF- RA because B cells play a less significant role in RA pathogenesis in RF- patients.

Management of extra-articular disease manifestations in rheumatoid arthritis

PURPOSE OF REVIEW

To discuss the rationale for various treatment strategies in rheumatoid arthritis with extra-articular manifestations, and to review advances in understanding the impact of extra-articular rheumatoid arthritis and its management.

RECENT FINDINGS

Recent epidemiologic studies of extra-articular rheumatoid arthritis manifestations have emphasized their major role as predictors of premature mortality in patients with rheumatoid arthritis, and provide a rationale for aggressive ant-rheumatic treatment of extra-articular rheumatoid arthritis. Previous uncontrolled or nonrandomized studies favor the use of cyclophosphamide in patients with systemic rheumatoid vasculitis, and methotrexate in the case of other manifestations of extra-articular rheumatoid arthritis. Recent case reports indicate that patients with rheumatoid lung disease may respond to cyclosporine or tumor necrosis factor inhibitors, and that tumor necrosis factor blocking therapy also may be successful in cases of treatment-resistant vasculitis. By contrast, it has been suggested that tumor necrosis factor inhibitors may induce some manifestations of extra-articular rheumatoid arthritis. Data indicating a high risk of serious infections and cardiovascular disease in patients with extra-articular rheumatoid arthritis underline the importance of carefully monitoring such patients.

SUMMARY

Extra-articular rheumatoid arthritis is a serious condition, and rheumatoid arthritis patients with extra-articular manifestations should be aggressively treated and monitored. Advances in the understanding of the pathogenesis of rheumatoid arthritis and developments of new, more specific drugs may be of particular benefit to patients with extra-articular disease.

Anti-CD20 monoclonal antibody treatment in 6 patients with therapy-refractory chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is an important determinant of long-term morbidity and mortality in allogeneic stem cell transplantation patients. Because cGVHD has clinical, histologic, and laboratory findings of autoimmune diseases and anti-B-cell therapy has shown efficacy in autoimmune diseases, we hypothesized that monoclonal anti-CD20 antibody therapy might improve patients with cGVHD. We treated 5 men and 1 woman with therapy-refractory extensive cGVHD with anti-CD20 monoclonal antibody. Intravenous infusion was given at a weekly dose of 375 mg/m(2) for 4 weeks. In case of incomplete clinical response, additional courses of 4 weeks were given. Five patients responded to treatment with marked clinical, biochemical, and histologic improvement. One patient failed to respond. Anti-CD20 monoclonal antibody seems to be effective in cGVHD. A controlled trial is mandatory to confirm these results. The outcome of this study suggests a participating role of B cells in the pathogenesis of cGVHD.

A phase II study of Rituximab in rheumatoid arthritis patients with recurrent disease following haematopoietic stem cell transplantation

Haematopoietic stem cell transplantation (HSCT) has been used recently as an effective therapy in patients with resistant rheumatoid arthritis (RA). Although disease control occurs in the majority of cases, recurrence is common, often coinciding with B-cell reconstitution. We hypothesized that Rituximab, a monoclonal anti-CD20 antibody, would have activity in this group of patients. We treated 10 RA patients (8F:2M, median age 46.5 years), who had recurrent disease post HSCT. All patients received two doses of Rituximab 1 g, 2 weeks apart with no major adverse sequelae and were followed for 12 months. A total of eight out of 10 patients experienced major clinical responses as measured by the American College of Rheumatology (ACR) criteria, with 50-70% improvement in disease parameters. Responses were equivalent to previous responses attained with HSCT. Disease responses were maximal at 4-8 months post Rituximab and correlated with B-cell lymphopenia and a reduction of rheumatoid factor titre. Disease recurrence occurred in 6/9 responders within 12 months and four patients were subsequently retreated, with major responses again attained. This study provides further evidence that B-cell depletion leads to a significant improvement in disease activity in patients with severe RA and provides data for future trials of HSCT and Rituximab therapy.

The innate mononuclear phagocyte network depletes B lymphocytes through Fc receptor-dependent mechanisms during anti-CD20 antibody immunotherapy

Anti-CD20 antibody immunotherapy effectively treats non-Hodgkin's lymphoma and autoimmune disease. However, the cellular and molecular pathways for B cell depletion remain undefined because human mechanistic studies are limited. Proposed mechanisms include antibody-, effector cell-, and complement-dependent cytotoxicity, the disruption of CD20 signaling pathways, and the induction of apoptosis. To identify the mechanisms for B cell depletion in vivo, a new mouse model for anti-CD20 immunotherapy was developed using a panel of twelve mouse anti-mouse CD20 monoclonal antibodies representing all four immunoglobulin G isotypes. Anti-CD20 antibodies rapidly depleted the vast majority of circulating and tissue B cells in an isotype-restricted manner that was completely dependent on effector cell Fc receptor expression. B cell depletion used both FcgammaRI- and FcgammaRIII-dependent pathways, whereas B cells were not eliminated in FcR common gamma chain-deficient mice. Monocytes were the dominant effector cells for B cell depletion, with no demonstrable role for T or natural killer cells. Although most anti-CD20 antibodies activated complement in vitro, B cell depletion was completely effective in mice with genetic deficiencies in C3, C4, or C1q complement components. That the innate monocyte network depletes B cells through FcgammaR-dependent pathways during anti-CD20 immunotherapy has important clinical implications for anti-CD20 and other antibody-based therapies.

Efficacy of B-cell-targeted therapy with rituximab in patients with rheumatoid arthritis

BACKGROUND

An open-label study indicated that selective depletion of B cells with the use of rituximab led to sustained clinical improvements for patients with rheumatoid arthritis. To confirm these observations, we conducted a randomized, double-blind, controlled study.

METHODS

We randomly assigned 161 patients who had active rheumatoid arthritis despite treatment with methotrexate to receive one of four treatments: oral methotrexate (> or =10 mg per week) (control); rituximab (1000 mg on days 1 and 15); rituximab plus cyclophosphamide (750 mg on days 3 and 17); or rituximab plus methotrexate. Responses defined according to the criteria of the American College of Rheumatology (ACR) and the European League against Rheumatism (EULAR) were assessed at week 24 (primary analyses) and week 48 (exploratory analyses).

RESULTS

At week 24, the proportion of patients with 50 percent improvement in disease symptoms according to the ACR criteria, the primary end point, was significantly greater with the rituximab-methotrexate combination (43 percent, P=0.005) and the rituximab-cyclophosphamide combination (41 percent, P=0.005) than with methotrexate alone (13 percent). In all groups treated with rituximab, a significantly higher proportion of patients had a 20 percent improvement in disease symptoms according to the ACR criteria (65 to 76 percent vs. 38 percent, P< or =0.025) or had EULAR responses (83 to 85 percent vs. 50 percent, P< or =0.004). All ACR responses were maintained at week 48 in the rituximab-methotrexate group. The majority of adverse events occurred with the first rituximab infusion: at 24 weeks, serious infections occurred in one patient (2.5 percent) in the control group and in four patients (3.3 percent) in the rituximab groups. Peripheral-blood immunoglobulin concentrations remained within normal ranges.

CONCLUSIONS

In patients with active rheumatoid arthritis despite methotrexate treatment, a single course of two infusions of rituximab, alone or in combination with either cyclophosphamide or continued methotrexate, provided significant improvement in disease symptoms at both weeks 24 and 48.

Improvement of refractory rheumatoid arthritis after depletion of B cells

OBJECTIVE

B cells are involved in the pathogenesis of rheumatoid arthritis (RA). To evaluate the effect of therapeutic B-cell depletion for treatment of RA, an open label study has been performed using the B-cell depleting anti-CD20 antibody rituximab.

METHODS

Five patients with refractory RA were treated weekly with four infusions of rituximab (375 mg/m2) alone, or in combination with ongoing methotrexate (MTX). Patients were followed for at least 44 weeks and monitored for safety and tolerability of treatment.

RESULTS

Treatment could be performed without serious side effects and resulted in peripheral B-cell depletion lasting between 36 weeks up to > 1 year. The follow-up revealed no significant treatment-associated side effects. At 22 weeks, 4/5 patients showed a significant improvement (> 1.2) of the Disease Activity Score (DAS28). The mean DAS28 of all patients declined from 6.2 to 4.1. At 44 weeks there was one drop-out, another patient still had a sustained response, and three patients showed slowly increasing disease activity (mean DAS28 of the remaining four patients: Week 0: 6.0; Week 22: 3.85; Week 44: 5.6). Despite relatively constant immunoglobulin levels, rheumatoid factor levels decreased parallel to disease activity.

CONCLUSION

In patients with refractory RA, B-cell depletion with rituximab is safe and well tolerated. A reduction of disease activity could be observed, which eventually deteriorated after B-cell repopulation. The findings give more evidence for B-cell targeted therapies in RA.

B cells as therapeutic targets for rheumatic diseases

PURPOSE OF REVIEW

Trials treating human rheumatic diseases with biologic agents and drugs that selectively affect B cells will be reviewed. Rituximab, an anti-CD20 monoclonal mouse/human antibody, will be the primary focus of the review because it has been widely used in several autoimmune and rheumatic conditions, but the limited studies on other reagents such as anti-BlyS, anti-CD154, and B cell tolerogens will also be covered.

RECENT FINDINGS

The single most important recent development was the completion of a randomized, double-blind, placebo-controlled trial of rituximab in methotrexate-resistant rheumatoid arthritis. In this trial, B cell depletion with rituximab led to a sustained clinical response with an impressive improvement in America College of Rheumatology 50% response (ACR 50) at both 24 and 48 weeks. Additional open studies of rituximab showing clinical benefit in systemic lupus erythematosus, cryoglobulinemia, antineutrophil cytoplasmic antibodies+ vasculitis, and dermatomyositis are noteworthy but must be interpreted with caution until randomized control trials are available. Two well-designed studies of anti-CD154 antibodies in systemic lupus erythematosus were reported. Unfortunately, one was halted because of unexpected vascular complications, and the other failed to show any beneficial clinical effect. A phase I study using anti-BlyS in SLE demonstrated a selective effect on B cells and no overt toxicity, but in this very short-term study no effect on serology or clinical activity was seen. Two B cell tolerogens have been used in human trials. The first tolerogen, directed at anti-dsDNA responses in SLE, did significantly decrease titers of high-affinity anti-dsDNA antibodies but had no clinically beneficial effect overall. A phase I trial of a tolerogen directed at anti-beta2-glycoprotein I antibodies demonstrated a decrease in antibody titers after a single injection.

SUMMARY

Several therapeutic agents targeting B cells have now been tested or are being tested in human trials. The success of rituximab in a well-controlled trial confirms previous preliminary reports indicating that B cell depletion can treat established autoimmune disease.

The transfer of a laboratory based hypothesis to a clinically useful therapy: the development of anti-TNF therapy of rheumatoid arthritis

The development of anti-TNF therapy is a key step forward in rheumatology as it is the first new therapy for based on investigating the molecular mechanisms of this disease. This chapter reviews how this discovery was made.

Successful Therapy of Rheumatoid Arthritis With Rituximab

Rheumatoid arthritis (RA) is often considered a T cell-mediated disease, yet recent studies describe benefit with rituximab, a monoclonal antibody directed against the B cell antigen CD20. We report our experience using rituximab for 5 patients with severe, disease-modifying antirheumatic drug (DMARD)-refractory RA. Five patients with seropositive, erosive RA received rituximab as 4 weekly doses of 375 mg/m. Four subjects experienced remission lasting 5 to 12 months after noting lack of efficacy with antitumor necrosis factor (TNF) therapy. All patients have relapsed, with signs and symptoms of RA returning a mean of 8 months after therapy. Rituximab appears to be a safe and potentially helpful treatment of refractory RA and, until U.S. Food and Drug Administration approval, could be considered for compassionate use in people who have failed multiple DMARDs. Individuals who do not respond to anti-TNF therapy could experience arthritis that is perpetuated by B cell more than T cell function; these patients could be most likely to respond to rituximab. Further studies are needed to clarify the optimal dose and frequency of rituximab therapy, and its role in combination therapy for individuals with RA.

The use of rituximab, anti-CD20 monoclonal antibody, in pediatric transplantation

Rituximab, chimeric anti-human CD-20, is approved for treatment of B-cell lymphoma in adults. It is being used experimentally in other various immune-related disease such as immune thrombocytopenic purpura, myasthenia gravis, and rheumatoid arthritis. In transplant recipients it is used for treatment of post-transplant lymphoproliferative disease, and prevention and treatment of acute rejection. There are few data on its use in children. This paper reviews the use of rituximab in these disease states and provides hypotheses for its mode of action.

Altered blood B lymphocyte homeostasis in systemic sclerosis: Expanded naive B cells and diminished but activated memory B cells

OBJECTIVE

To determine phenotypic and functional abnormalities of blood B cell subsets in patients with systemic sclerosis (SSc).

METHODS

Cell surface marker expression was determined by flow cytometry. Spontaneous apoptosis was evaluated by annexin V expression with flow cytometric analysis. IgG production by isolated IgD- memory B cells was examined by enzyme-linked immunosorbent assay.

RESULTS

The numbers of blood CD27- naive B cells from SSc patients were increased compared with normal control cells, while memory B cells expressing medium levels of CD27 and plasmablasts expressing high levels of CD27 were reduced. In contrast, plasmablasts were the predominant population in patients with systemic lupus erythematosus (SLE). Memory B cells in SSc showed increased expression of activation markers, including CD80, CD86, and CD95, relative to normal controls. Consistent with CD95 up-regulation, SSc memory B cells exhibited augmented spontaneous apoptosis after 24-hour incubation; augmented apoptosis may explain the reduced memory B cell number. Nonetheless, isolated IgD- SSc memory B cells treated with stimuli had an enhanced ability to produce IgG. Furthermore, expression of CD19, a critical signal transduction molecule of B cells that regulates autoantibody production, was significantly increased in memory B cells as well as in naive B cells in SSc. In contrast, CD19 expression was decreased in SLE B cells.

CONCLUSION

SSc patients have distinct abnormalities of blood homeostasis and B cell compartments, characterized by expanded naive B cells and activated but diminished memory B cells. Our results suggest that CD19 overexpression in SSc memory B cells is related to their hyperreactivity.

Use of localised gene transfer to develop new treatment strategies for the salivary component of Sjögren's syndrome

Effective treatment for Sjögren's syndrome (SS) might be developed locally by introducing genes encoding cytokines, which are potentially anti-inflammatory, or by introducing a cDNA encoding a soluble form of a key cytokine receptor, which can act as an antagonist and decrease the availability of certain cytokines, such as soluble tumour necrosis factor alpha receptors. Currently, the preferred choice of viral vector for immunomodulatory gene transfer is recombinant adeno-associated virus. The use of gene transfer to help determine the pathophysiology and to alter the course of the SS-like disease in the NOD mouse model can ultimately lead to the development of new treatments for managing the salivary component in patients with SS.

Safety of rituximab in the treatment of B cell malignancies: implications for rheumatoid arthritis

The chimeric anti-CD20 monoclonal antibody rituximab has been used extensively in the treatment of B cell malignancies, and more recently it has emerged as a potential treatment for rheumatoid arthritis (RA), via selective B lymphocyte depletion. Experience in oncology shows that rituximab is well tolerated in a variety of settings, with mild-to-moderate infusion related reactions following the first infusion being the most common adverse event. Current data suggest that the safety profile of rituximab in patients with RA is similar to that in oncology, but that the adverse events are less frequent and less severe in patients with RA.

B cell depletion in autoimmune disease

The CD20 cell marker appears early in the process of B cell development. In this review we focus on the results of attempts to utilize B cell depletion based on the use of a chimeric monoclonal antibody (MAb) specific for human CD20, rituximab, for the treatment of patients with autoimmune diseases. In 1997, rituximab was approved for the treatment of low-grade B cell non-Hodgkin's lymphoma. Following these encouraging results, rituximab started to be used experimentally in other diseases presumed to be due to B cell pathology. The first autoimmune disease to be treated effectively was chronic idiopathic thrombocytopaenia. More recent success has been demonstrated in patients with rheumatoid arthritis and systemic lupus erythematosus.

Differential in vivo effects of rituximab on two B-cell subsets in cynomolgus monkeys

Cynomolgus monkeys (Macaca fascicularis) are widely used animal models in biomedical research and have been used to study new therapeutics aimed at B-cell depletion. We have recently identified two different B-cell subsets in cynomolgus monkey, with the CD20lowCD40highCD21+ subset being phenotypically closer to human B cells and having a similar responsivness to anti-CD20 mAb, rituximab, in in vitro depletion assays. Here, we show that similar to in vitro findings CD20highCD40lowCD21- and CD20lowCD40highCD21+ cynomolgus monkey B cells differ significantly in their in vivo susceptibility to rituximab, as the low dose of 0.05 mg/kg of rituximab resulted in more than 70% depletion of the former B-cell subset and virtually no depletion of the latter B-cell subset. Our data suggest that for the B-cell-targeting anti-CD20 therapeutics, depletion of CD20lowCD40highCD21+ subset rather than depletion of all cynomolgus monkey B cells is more relevant to dose-efficacy projections for humans. In addition, we show that differential cell surface expression of CD80/CD86 costimulatory molecules on the two different cynomolgus monkey B-cell subsets is similar to that identified in rhesus monkeys, suggesting that our in vivo study may be relevant to other monkey models.

A novel therapeutic approach targeting articular inflammation using the filarial nematode-derived phosphorylcholine-containing glycoprotein ES-62

Understanding modulation of the host immune system by pathogens offers rich therapeutic potential. Parasitic filarial nematodes are often tolerated in human hosts for decades with little evidence of pathology and this appears to reflect parasite-induced suppression of host proinflammatory immune responses. Consistent with this, we have previously described a filarial nematode-derived, secreted phosphorylcholine-containing glycoprotein, ES-62, with immunomodulatory activities that are broadly anti-inflammatory in nature. We sought to evaluate the therapeutic potential of ES-62 in vitro and in vivo in an autoimmune disease model, namely, collagen-induced arthritis in DBA/1 mice. ES-62 given during collagen priming significantly reduced initiation of inflammatory arthritis. Crucially, ES-62 was also found to suppress collagen-induced arthritis severity and progression when administration was delayed until after clinically evident disease onset. Ex vivo analyses revealed that in both cases, the effects were associated with inhibition of collagen-specific pro-inflammatory/Th1 cytokine (TNF-alpha, IL-6, and IFN-gamma) release. In parallel in vitro human tissue studies, ES-62 was found to significantly suppress macrophage activation via cognate interaction with activated T cells. Finally, ES-62 suppressed LPS-induced rheumatoid arthritis synovial TNF-alpha and IL-6 production. Evolutionary pressure has promoted the generation by pathogens of diverse mechanisms enabling host immune system evasion and induction of "tolerance." ES-62 represents one such mechanism. We now provide proof of concept that parasite-derived immunomodulatory strategies offer a novel therapeutic opportunity in inflammatory arthritis.

Serologic changes following B lymphocyte depletion therapy for rheumatoid arthritis

OBJECTIVE

To explore the changes in serologic variables and clinical disease activity following B lymphocyte depletion in 22 patients with rheumatoid arthritis (RA).

METHODS

B lymphocyte depletion was attained using combination therapy based on the monoclonal anti-CD20 antibody rituximab. Levels of a serologic indicator of inflammation, C-reactive protein (CRP), of antimicrobial antibodies, of autoantibodies including IgA-, IgM-, and IgG-class rheumatoid factors (RF), and of antibodies to cyclic citrullinated peptide (anti-CCP) were assayed.

RESULTS

The majority of patients showed a marked clinical improvement after treatment with rituximab, with benefit lasting up to 33 months. Levels of total serum immunoglobulins fell, although the mean values each remained within the normal range. Whereas the IgM-RF response paralleled the changes in total serum IgM levels, the levels of IgA-RF, IgG-RF, and IgG and anti-CCP antibodies decreased significantly more than did those of their corresponding total serum immunoglobulin classes. The kinetics for the reduction in CRP levels also paralleled the decreases in autoantibody levels. In contrast, levels of antimicrobial antibodies did not change significantly. B lymphocyte return occurred up to 21 months posttreatment. The time to relapse after B lymphocyte return was often long and unpredictable (range 0-17 months). Relapse was, however, closely correlated with rises in the level of at least one autoantibody. Increased autoantibody levels were rarely observed in the absence of clinical change.

CONCLUSION

Following B lymphocyte depletion in patients with RA, a positive clinical response occurred in correlation with a significant drop in the levels of CRP and autoantibodies. Antibacterial antibody levels were relatively well maintained. B lymphocyte return preceded relapse in all patients. There was also a temporal relationship between clinical relapse and rises in autoantibody levels. Although these observations are consistent with a role for B lymphocytes in the pathogenesis of RA, the precise mechanisms involved remain unclear.

Rituximab in idiopathic membranous nephropathy: a one-year prospective study

Currently available monoclonal antibodies against the B cell surface antigen CD20 have been employed to explore whether specific inhibition of B cells may help improve the outcome of idiopathic membranous nephropathy (IMN) and may avoid the side effects of steroids and immunosuppressants. This prospective, observational study evaluated the 1-yr outcome of eight IMN patients with persistent (>6 mo) urinary protein excretion > 3.5 g/24 h given four weekly infusions of the anti-CD20 antibody rituximab (375 mg/m(2)). At 3 and 12 mo, proteinuria significantly decreased from mean (+/- SD) 8.6 +/- 4.2 to 4.3 +/- 3.3 (-51%, P < 0.005) and 3.0 +/- 2.5 (-66%, P < 0.005) g/24 h, albumin fractional clearance from 2.3 +/- 2.1 to 1.2 +/- 1.7 (-47%, P < 0.05) and 0.5 +/- 0.6 (-76%, P < 0.003), and serum albumin concentration increased from 2.7 +/- 0.5 to 3.1 +/- 0.3 (+21%, P < 0.05) and 3.5 +/- 0.4 (+41%, P < 0.05) mg/dl. At 12 mo, proteinuria decreased to < or =0.5 g/24 h or < or =3.5 g/24 h in two and three patients, respectively. Proteinuria decreased in the remaining patients by 74%, 44%, and 41%, respectively. Body weight, diastolic BP, and serum cholesterol progressively decreased in parallel with an improvement of edema in all patients. Renal function stabilized (Delta1/creatinine: +0.002 +/- 0.007). CD20 B lymphocytes fell below normal ranges up to study-end. No patient had major drug-related events or major changes in other laboratory parameters. Rituximab thus promotes sustained disease remission in patients otherwise predicted to progress to ESRD, and it is safe. The long-term risk/benefit profile of this novel, disease-specific approach seems much more favorable to that of commonly employed immunosuppressive drugs.

High-throughput single-nucleotide polymorphism analysis of the IL1RN locus in patients with ankylosing spondylitis by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry

OBJECTIVE

To examine single-nucleotide polymorphisms (SNPs) in the 3' region of the IL1RN gene in a large Caucasoid case-control series and in ankylosing spondylitis (AS) families from Western Canada by use of high-throughput MassArray matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry SNP typing.

METHODS

An association analysis was performed in a case-control cohort of 394 AS cases and 500 controls. Family-based association analysis was performed in 58 simplex and 13 multiplex families. Three SNPs located in the 3' region of the IL1RN gene (T/C at position 27810 in exon 4, T/C at position 30735 in exon 6, and G/C at position 31017 in exon 6) were examined by high-throughput MassArray MALDI-TOF mass spectrometry. Haplotype inference software programs were used to infer the most likely haplotypes and to compare haplotype frequencies, which were then further analyzed in family-based association studies by transmission disequilibrium tests.

RESULTS

The frequency of allele C at SNP position 30735 in exon 6 was significantly increased in AS cases (35.1%) versus controls (27.8%), as was the phenotype frequency (61.7% versus 48.6%). A significantly increased frequency of SNP allele G at position 31017 in exon 6 in cases (32.9%) versus controls (28.3%) was also noted. A highly significant difference in the overall distribution of haplotype frequencies was evident between cases and controls, with significant increases in the frequencies of the 27810C/30735C/31017C and 27810C/30735T/31017G haplotypes, but a significant reduction in the estimated frequency of the 27810C/30735T/31017C haplotype, in the AS cases. Estimation of haplotype frequencies based on 2 SNP markers indicated a highly significant increase in the 30735C/31017C haplotype and a highly significant decrease in the 30735T/31017C haplotype in cases compared with controls. Preliminary evidence for reduced transmission of the 27810C/30735T/31017C 3-marker haplotype was also found in family-based association analyses.

CONCLUSION

Our data establish a highly significant disease association with markers in the IL1RN gene. In the absence of nonsynonymous coding sequence substitutions, it is possible that the primary disease-associated locus regulates gene expression. Association with specific haplotypes raises the possibility that the primary disease locus is in linkage disequilibrium with a specific combination(s) of markers in the IL1RN gene.

The power of the third dimension: tissue architecture and autoimmunity in rheumatoid arthritis

Lymphoid organs are the anatomic solution to the challenge of responding to minute amounts of antigen with powerful effector mechanisms. By arranging interacting cells in complex three-dimensional topographies lymphoid organs provide an optimal match between form and function. This principle is exploited in ectopic lymphoid structures that characteristically appear in rheumatoid synovitis. Synovial tissue T cells and B cells cooperate in different types of lymphoid organizations. Dendritic cell networks in the inflamed synovial membrane optimize antigen collection, storage, processing, and presentation. Synovial tissue cells participate in lymphocyte recruitment and the formation of tissue architectures that amplify immune responses. Recent data support the concept that the tissue organization in the rheumatoid joint fosters a breakdown in self-tolerance by promoting a phase transition from self-limited immune responses to self-perpetuating autoimmune responses.

The role of B cells in rheumatoid arthritis: mechanisms and therapeutic targets

Our understanding of the role of B cells as part of the immune system has been remarkably expanded in the past few years. Autoimmunity, the production of autoantibodies or the activation and expansion of autoimmune T cells, is relatively common, whereas the development of autoimmune diseases with destruction of tissue is much less frequent. In rheumatoid arthritis, the autoantigen(s) involved in tissue damage and their role in disease have not been fully elucidated. Recent data suggest that the impact of B cells in rheumatoid arthritis may be of significance; therefore, a depleting anti-B cell therapy appears to be another therapeutic strategy. This review will focus on recent findings of the role of B cells in rheumatoid arthritis and the implications to target B cells in this disease.

Effect of anti-CD20 monoclonal antibody, Rituxan, on cynomolgus monkey and human B cells in a whole blood matrix

BACKGROUND

Cynomolgus monkeys are widely used animal models in biomedical research. The differences between cynomolgus monkey and human B cells are not completely understood. However, these differences are of crucial importance for interpretation of data from studies on new therapeutic agents aimed at B-cell depletion, such as anti-CD20 monoclonal antibodies.

METHODS

Multicolor fluorescence-activated cell sorting analysis of peripheral blood B cells was performed on samples treated ex vivo with the anti-CD20 therapeutic monoclonal antibody, Rituxan, in a whole blood matrix.

RESULTS

In contrast to humans, cynomolgus monkeys had two distinct B-cell subsets, CD20highCD40lowCD21- and CD20lowCD40highCD21+. These B-cell subsets had a 2.5-fold difference in the EC50 for Rituxan binding and differed significantly in their in vitro susceptibility to Rituxan depletion. Human B cells were similar to the CD20lowCD40highCD21+ cynomolgus monkey B cells with regard to their EC50 for Rituxan and response to Rituxan in a whole blood matrix assay. CD21 was upregulated, whereas CD40 was downregulated at incubation with Rituxan in the CD20lowCD40highCD21+ monkey and human B cells in a concentration-dependent manner.

CONCLUSIONS

These findings have direct implications for in vivo studies of therapeutic agents that target B cells in cynomolgus monkeys and for extrapolation of the results to humans. In addition, our data are consistent with the model in which CD20, CD21, and CD40 exist in a supramolecular complex that is affected by anti-CD20 monoclonal antibodies.

Ectopic germinal center formation in rheumatoid synovitis

Synovial inflammation in rheumatoid arthritis is closely related to the formation of ectopic lymphoid microstructures. In synovial tissue from some patients, one finds seemingly diffuse infiltrates; in others, T cells and B cells cluster in aggregates with interdigitating dendritic cells (DCs) but no follicular DCs (FDCs). In a third group, T cell/B cell follicles with germinal center (GC) reactions are generated. Within a given patient, aggregates and GCs are mutually exclusive and stable over time. Because antigen storage capacity, lymphoid density, and three-dimensional topography of GCs optimize immune responses, synovial GCs should play a crucial role in the breakdown of self-tolerance. We have identified factors critical for ectopic GCs, thereby transforming the synovial inflammatory process. Tissues with GCs produced 10- to 20-fold higher amounts of the chemokines CXCL13 and CCL21. CXCL13 derived from three sources, endothelial cells, synovial fibroblasts, and FDC networks. The level of CXCL13 transcripts strongly predicted GCs; however, some tissues had high levels of CXCL13 but lacked GCs. Tissue expression of LT-beta emerged as a second key factor. LT-beta protein was detected on follicular center and mantle zone B cells. Multivariate regression analysis identified CXCL13 and LT-beta as the only cytokines predicting GCs. Remarkably, LT-alpha did not contribute independently. The contribution of B cells to ectopic lymphoid organogenesis was not limited to LT-beta production. Rather, synovial tissue B cells were critical in regulating T cell activation. In adoptive transfer experiments in human synovium-SCID mouse chimeras, activation of synovium-derived CD4 T cells was strictly dependent on T cell/B cell follicles. Depletion of synovial tissue B cells abrogated T cell function, and non-B cell antigen-presenting cells could not maintain T cell stimulation. Unexpectedly, GC function in the rheumatoid lesion was also dependent on CD8 T cells. The majority of T cell receptors derived from CD8 T cells were shared between distinct GCs. Depletion of CD8 T cells disrupted synovial GCs, FDC networks disappeared, and transcription of LT-beta, IgG, and Igkappa declined. Follicle-sustaining CD8 T cells were located at the edge of or within the mantle zone. Cell-cell communication in the mantle zone, including CD8 T cells, appears to be critical for ectopic GC formation in rheumatoid synovitis.

Rheumatoid arthritis: proposal for the use of anti-microbial therapy in early cases

Rheumatoid arthritis (RA) is a chronic disease, affecting women more than men, especially in those possessing the "shared epitope" (EQK/RRAA) amino acid sequences present in HLA-DR1/4 molecules. Proteus mirabilis carries sequences showing molecular mimicry to the "shared epitope" and to type XI collagen of hyaline cartilage. Elevated levels of antibodies to P. mirabilis have been reported from 14 different countries involving 1375 RA patients and the microbe has been isolated from urine cultures of such patients. Our working hypothesis is that the disease develops as a result of repeated episodes of Proteus upper urinary tract infections. Prospective studies involving the trial of anti-Proteus measures in RA patients should be evaluated in the management of this disease. Antibiotics, high fluid intake, and fruit extracts, such as cranberry juice, have all been found to be effective in the treatment of urinary tract infections. Such measures could be used as possible additional adjuncts to the standard therapy with NSAIDs and DMARDs.

Regulation of B lymphocytes in health and disease. Meeting review

Signal transduction by the B cell receptor (BCR) is an absolute requirement for the selection and development of B lymphocytes at multiple checkpoints. Binding to antigen via the BCR is complemented by a co-stimulus delivered through accessory and co-stimulatory cell surface molecules that regulate the signalling threshold. In addition, identification of genes associated with immunodeficiency syndromes has highlighted the importance of genetic regulation, particularly in immunoglobulin class-switching and somatic hypermutation. A 1-day symposium organised by the Biochemical Society considered some of the recent advances in our understanding of the molecules and regulatory pathways involved in B lymphocyte activation, differentiation and survival and the health consequences when threshold settings malfunction.

B cells as a therapeutic target in autoimmune disease

Depleting B cells with anti-CD20 monoclonal antibodies emerges as a new therapeutic strategy in autoimmune diseases. Preliminary clinical studies suggest therapeutic benefits in patients with classic autoantibody-mediated syndromes, such as autoimmune cytopenias. Treatment responses in rheumatoid arthritis have opened the discussion about whether mechanisms beyond the removal of potentially pathogenic antibodies are effective in B-cell depletion. B cells may modulate T-cell activity through capturing and presenting antigens or may participate in the neogenesis of lymphoid microstructures that amplify and deviate immune responses. Studies exploring which mechanisms are functional in which subset of patients hold the promise of providing new and rational treatment approaches for autoimmune syndromes.

CD20-mediated apoptosis: signalling through lipid rafts

CD20 is an effective target for therapeutic B-cell depletion with monoclonal antibodies. One proposed mechanism of action is direct cytotoxicity mediated via tyrosine kinase-dependent signalling pathways activated upon CD20 cross-linking. The association of CD20 with membrane microdomains known as lipid rafts, enriched in src-family tyrosine kinases and other signalling effectors, suggests an indirect mechanism of anti-CD20-induced apoptosis in which activation of src-family kinases occurs as a consequence of lipid raft clustering.

An open study of B lymphocyte depletion in systemic lupus erythematosus

OBJECTIVE

To gain preliminary evidence for the safety and efficacy of B lymphocyte depletion therapy in refractory systemic lupus erythematosus (SLE).

METHODS

Six female patients with active SLE, resistant to standard immunosuppressive therapy, were treated on an open-label basis. During a 2-week period, each patient received two 500-mg infusions of rituximab, two 750-mg infusions of cyclophosphamide, and high-dose oral corticosteroids.

RESULTS

No significant adverse events were observed during followup. Patient 1 had not improved at 3 months but was then lost to followup. At 6 months, all 5 remaining patients had improved, as evidenced by improvement in British Isles Lupus Assessment Group global scores, from a median of 14 (range 9-27) at baseline to a median of 6 (range 3-8) at 6 months. Manifestations of SLE such as fatigue, arthralgia/arthritis, and serositis responded particularly well to this protocol. Hemoglobulin levels increased in patients 2, 3, 5, and 6. The erythrocyte sedimentation rate decreased in patients 2, 3, 4, and 5 and was stable in patient 1. In patients 4 and 5, the urinary protein-to-creatinine ratio decreased significantly. C3 serum levels increased in all 5 patients who had low levels at baseline; in two of these patients, patients 2 and 5, C3 values were normal at 6 months. The variation in the level of anti-double-stranded DNA antibody was different in individual patients.

CONCLUSION

This study provides sufficient evidence for the safety and possible efficacy of B lymphocyte depletion therapy in SLE to justify a formal controlled trial.

Clinical outcome in 22 patients with rheumatoid arthritis treated with B lymphocyte depletion

OBJECTIVES

To obtain evidence for dose response and to extend evidence of safety and efficacy for B lymphocyte depletion in rheumatoid arthritis.

METHODS

Twenty two patients with rheumatoid arthritis received a total of 29 treatments with five different combinations of rituximab (RTX), cyclophosphamide (CP), and/or high dose prednisolone (PR) on an open basis as follows; cohort I: RTX 1400 mg/m(2), CP 750x2+PR; cohort II: RTX 300-700 mg/m(2), -CP+/-PR); cohort III: RTX 600-700 mg/m(2), CP 750x2+PR; cohort IV: RTX 1200 mg/m(2), CP 750x2-PR; cohort V: RTX 500 mg/m(2), CP 750x2+PR. American College of Rheumatology (ACR) criteria of improvement at six months were chosen as the primary outcome measure. Disease activity scores and total duration of improvement and of B cytopenia were also recorded.

RESULTS

No major adverse events attributable to treatment were seen. ACR grades of improvement at six months were as follows: cohort I: ACR70x3, ACR50x2; cohort II: ACR20x1, ACR0x3; cohort III: ACR70x6, ACR50x2, ACR20x2; cohort IV: ACR70x2, ACR50x2, ACR20x1, ACR0x1; cohort V: ACR0x4.

CONCLUSIONS

B lymphocyte depletion in rheumatoid arthritis has so far proved to be safe and associated with major improvement with protocols including RTX 600 mg/m(2) or more and CP, but not with more limited protocols. These observations provide an initial basis for the design of formal trials of B cell depletion and other B cell directed treatments, including a phase II controlled trial now in progress.

Efficacy of selective B cell blockade in the treatment of rheumatoid arthritis: evidence for a pathogenetic role of B cells

OBJECTIVE

The pathogenetic role of B cells in rheumatoid arthritis (RA) is under debate, but it is currently believed to be marginal. The availability of selective anti-B cell treatment provides a unique opportunity to clarify this issue. This study was undertaken to investigate the effects of B cell blockade in the treatment of refractory RA, and to evaluate the implications with regard to the role of B cells in the disease.

METHODS

Five female patients with active, evolving erosive RA were treated with rituximab, an anti-CD20 chimeric monoclonal antibody. All 5 patients had been nonresponders to combination therapy with methotrexate plus cyclosporin A. Two of the 5 had also failed to respond to anti-tumor necrosis factor alpha therapy. All of these treatments were discontinued 1 month before institution of anti-CD20 therapy.

RESULTS

Marked clinical improvement was observed in 2 patients (American College of Rheumatology 70% response [ACR70] and ACR50, respectively), starting at the end of the second month after institution of anti-CD20 therapy (month 2) and lasting until month 10 in 1 patient (articular relapse) and month 12 in the other (last followup). ACR20 response was observed in 2 additional patients, lasting until month 5 and month 7, respectively (articular relapse in both). Decrease or normalization of serum C-reactive protein and rheumatoid factor levels were observed in these patients. In contrast, patient 3 had no response to the treatment. RA synovitis and evolving erosive damage were decreased in patients exhibiting a major response, as demonstrated by imaging studies.

CONCLUSION

Our finding of the clinical efficacy of selective B cell blockade indicates that B cells play a critical role in rheumatoid synovitis, at least in a subset of patients. Qualitative or quantitative differences in B cell commitment in RA pathobiology might have a function in the different responses observed.

B cells and immunoglobulins dependent mechanisms in rheumatoid arthritis: a possible rationale of the extracorporeal immunomodulation for rheumatoid arthritis

Patients with rheumatoid arthritis (RA) have several options for treatment nowadays, although we do not know what types of therapies are effective for these patients because RA is a very heterogenous disease. We discuss several possible mechanisms of RA in this review and explain one possible scenario of autoantibodies dependent arthritis confirmed by anti-glucose-6-phosphate isomerase antibodies. We also propose several efficacious treatments for treating these patients as made-to-order therapies.

Novel pathways that regulate tumor necrosis factor-alpha production in rheumatoid arthritis

Clinical intervention studies have clearly shown the benefit in suppressing tumor necrosis factor-alpha (TNF-alpha) rheumatoid arthritis (RA). In consequence, considerable interest has arisen in those pathways that in turn regulate TNF-alpha production, because they may offer further possible therapeutic targets. Several candidate pathways are currently being investigated. They include T cell/macrophage interactions mediated primarily through cell-cell membrane contact; novel cytokine activities; microbial-derived products, in particular bacterial deoxyribonucleic acid sequences; autoreactive T cells, and immunoglobulins. At the subcellular level, there is further interest in targeting signaling and mRNA processing and cytokine cleavage pathways required for optimal TNF-alpha production. The key recent observations in these areas, particularly in the extracellular compartment, are reviewed.