CD40L overexpression on T cells and monocytes from patients with systemic lupus erythematosus is resistant to calcineurin inhibition

Proinflammatory cytokines and ARDS pulmonary edema fluid induce CD40 on human mesenchymal stromal cells-A potential mechanism for immune modulation

Human mesenchymal stem/stromal cells (hMSCs) are a promising therapy for acute respiratory distress syndrome (ARDS) and other inflammatory conditions. While considerable research has focused on paracrine effects and mitochondrial transfer that improve lung fluid balance, hMSCs are well known to have immunomodulatory properties as well. Some of these immunomodulatory properties have been related to previously reported paracrine effectors such as indoleamine-2,3-dioxygenase (IDO), but these effects cannot fully account for cell-contact dependent immunomodulation. Here, we report that CD40 is upregulated on hMSCs under the same conditions previously reported to induce IDO. Further, CD40 transcription is also upregulated on hMSCs by ARDS pulmonary edema fluid but not by hydrostatic pulmonary edema fluid. Transcription of CD40, as well as paracrine effectors TSG6 and PTGS2 remained significantly upregulated for at least 12 hours after withdrawal of cytokine stimulation. Finally, induction of this immune phenotype altered the transdifferentiation of hMSCs, one of their hallmark properties. CD40 may play an important role in the immunomodulatory effects of hMSCs in ARDS and inflammation.

Regulation of microRNA in systemic lupus erythematosus: the role of miR-21 and miR-210

miRNAs are small non-coding RNA molecules that participate through silencing in post-transcriptional regulation of gene expression. Recent studies have highlighted the importance of microRNAs (miRNAs) as regulators of both the innate and the adaptive immune response. There are emerging data regarding the role of miRNAs in patients with Systemic Lupus Erythematosus (SLE). One of the main stimuli for the induction of miR-21 is hypoxia. Moreover, the expression and function of miR-210 is directly related to the activity of "hypoxia inducible factor-1a" (HIF-1a). The aim of the study is to examine the regulation of miR-21 and mir-210 in patients with SLE based on the hypothesis that cellular hypoxia may have an important role in SLE pathogenesis. Plasma, PBMC and urine samples will be collected from patients with SLE and normal controls. miR expression will be studied with real-time PCR. Functional experiments will examine the effect of miR-21 and miR- 210 on HIFa and ERK1/2 και PI3K/AKT signalling pathways. The study will provide novel data regarding the expression and the role of miR-21 and miR-210 in patients with SLE. The results of the study will contribute to a better understanding of miR network regulation in SLE in order to ultimately identify molecules that can be used in clinical practice as diagnostic or prognostic markers, treatment response markers, or even as potential future therapeutic targets.

Altered Cell Surface N-Glycosylation of Resting and Activated T Cells in Systemic Lupus Erythematosus

Altered cell surface glycosylation in congenital and acquired diseases has been shown to affect cell differentiation and cellular responses to external signals. Hence, it may have an important role in immune regulation; however, T cell surface glycosylation has not been studied in systemic lupus erythematosus (SLE), a prototype of autoimmune diseases. Analysis of the glycosylation of T cells from patients suffering from SLE was performed by lectin-binding assay, flow cytometry, and quantitative real-time PCR. The results showed that resting SLE T cells presented an activated-like phenotype in terms of their glycosylation pattern. Additionally, activated SLE T cells bound significantly less galectin-1 (Gal-1), an important immunoregulatory lectin, while other lectins bound similarly to the controls. Differential lectin binding, specifically Gal-1, to SLE T cells was explained by the increased gene expression ratio of sialyltransferases and neuraminidase 1 (NEU1), particularly by elevated ST6 beta-galactosamide alpha-2,6-sialyltranferase 1 (ST6GAL1)/NEU1 and ST3 beta-galactoside alpha-2,3-sialyltransferase 6 (ST3GAL6)/NEU1 ratios. These findings indicated an increased terminal sialylation. Indeed, neuraminidase treatment of cells resulted in the increase of Gal-1 binding. Altered T cell surface glycosylation may predispose the cells to resistance to the immunoregulatory effects of Gal-1, and may thus contribute to the pathomechanism of SLE.

Association of Platelet Binding to Lymphocytes with B Cell Abnormalities and Clinical Manifestations in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease associated with the polyclonal activation of B lymphocytes and the production of autoantibodies that cause immune complex-related inflammation. Immunological factors derived from platelets modulate B cell function in SLE disease. However, platelets do not only modify the immune system by soluble factors. The binding of platelets to lymphocytes can modulate immune response. Thus, we speculate that the binding of platelets to lymphocytes in SLE patients may play a role in abnormal B lymphocyte response and the pathogenesis of SLE. We observed that levels of lymphocytes with bound platelets were higher in SLE patients than in healthy donors (HD). In SLE patients, the percentage of B lymphocytes with bound platelets positively correlated with plasmatic levels of IgG, IgA, IL-10, and soluble CD40L and negatively correlated with IgM levels, though not in HD. Preswitched memory B lymphocytes were the subpopulation with more bound platelets. Lymphocytes with bound platelets from both HD and SLE patients had major levels of CD86 and BAFFR and a greater production of IL-10 than lymphocytes without bound platelets. However, only B lymphocytes with bound platelets from SLE patients had increased levels of IgG and IgA on their surface. SLE patients with a suggestive renal manifestation had the highest levels of B and T lymphocytes with bound platelets. These results suggest that the binding of platelets to lymphocytes plays a role in SLE disease and that controlling this binding may be a promising therapeutic approach.

Safety, pharmacokinetics and pharmacodynamics of single rising doses of BI 655064, an antagonistic anti-CD40 antibody in healthy subjects: a potential novel treatment for autoimmune diseases

PURPOSE

The CD40-CD40L pathway is a promising treatment target for autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus and lupus nephritis. The safety, pharmacokinetics and pharmacodynamics of BI 655064, a novel humanised antagonistic anti-CD40 monoclonal antibody, were investigated in this first-in-human trial.

METHODS

Healthy male subjects (n = 72) were randomised 3:1, within each BI 655064 dose group, to single intravenous (IV; 0.2-120 mg) or subcutaneous (SC; 40-120 mg) doses of BI 655064 or placebo. Safety, plasma exposure, CD40 receptor occupancy and CD40L-induced CD54 upregulation were assessed over 12 weeks.

RESULTS

Adverse events (AEs) were reported in 43% of subjects (n = 31). Frequency and intensity of AEs were generally similar between BI 655064 and placebo and showed no dose relationship. The most frequent AEs were headache and nasopharyngitis. One mild rash and one local reaction occurred with SC BI 655064; two serious AEs were reported, both judged unrelated to BI 655064. Pharmacokinetic evaluation demonstrated a more than proportional increase in plasma exposure relative to BI 655064 dose, with a terminal half-life between 4 h and 4 days IV and approximately 5 days SC; doses ≥ 20 mg IV and 120 mg SC showed > 90% CD40 receptor occupancy and inhibition of CD54 upregulation, which lasted 7 days in the 120 mg IV and SC groups.

CONCLUSIONS

Single doses up to 120 mg BI 655064 IV and SC were well tolerated and showed a high potential to block the CD40-CD40L pathway, supporting further clinical development of BI 655064 in patients with autoimmune disease.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01510782.

Scaffold protein JLP mediates TCR-initiated CD4+T cell activation and CD154 expression

CD4⁺ T-cell activation and its subsequent induction of CD154 (CD40 ligand, CD40L) expression are pivotal in shaping both the humoral and cellular immune responses. Scaffold protein JLP regulates signal transduction pathways and molecular trafficking inside cells, thus represents a critical component in maintaining cellular functions. Its role in regulating CD4⁺ T-cell activation and CD154 expression, however, is unclear. Here, we demonstrated expression of JLP in mouse tissues of lymph nodes, thymus, spleen, and also CD4⁺ T cells. Using CD4+ T cells from jlp-deficient and jlp-wild-type mice, we demonstrated that JLP-deficiency impaired T-cell proliferation, IL-2 production, and CD154 induction upon TCR stimulations, but had no impacts on the expression of other surface molecules such as CD25, CD69, and TCR. These observed impaired T-cell functions in the jlp-/- CD4⁺ T cells were associated with defective NF-AT activation and Ca²⁺ influx, but not the MAPK, NF-κB, as well as AP-1 signaling pathways. Our findings indicated that, for the first time, JLP plays a critical role in regulating CD4⁺ T cells response to TCR stimulation partly by mediating the activation of TCR-initiated Ca²⁺/NF-AT.

Systemic lupus erythematosus in the light of the regulatory effects of galectin-1 on T-cell function

Galectin-1 is an endogenous immunoregulatory lectin-type protein. Its most important effects are the inhibition of the differentiation and cytokine production of Th1 and Th17 cells, and the induction of apoptosis of activated T-cells. Galectin-1 has been identified as a key molecule in antitumor immune surveillance, and data are accumulating about the pathogenic role of its deficiency, and the beneficial effects of its administration in various autoimmune disease models. Initial animal and human studies strongly suggest deficiencies in both galectin-1 production and responsiveness in systemic lupus erythematosus (SLE) T-cells. Since lupus features widespread abnormalities in T-cell activation, differentiation and viability, in this review the authors wished to highlight potential points in T-cell signalling processes that may be influenced by galectin-1. These points include GM-1 ganglioside-mediated lipid raft aggregation, early activation signalling steps involving p56Lck, the exchange of the CD3 ζ-ZAP-70 to the FcRγ-Syk pathway, defective mitogen-activated protein kinase pathway activation, impaired regulatory T-cell function, the failure to suppress the activity of interleukin 17 (IL-17) producing T-cells, and decreased suppression of the PI3K-mTOR pathway by phosphatase and tensin homolog (PTEN). These findings place galectin-1 into the group of potential pathogenic molecules in SLE.

Follicular Helper T Cells in Systemic Lupus Erythematosus: Why Should They Be Considered as Interesting Therapeutic Targets?

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by B cell hyperactivity leading to the production of autoantibodies, some of which having a deleterious effect. Reducing autoantibody production thus represents a way of controlling lupus pathogenesis, and a better understanding of the molecular and cellular factors involved in the differentiation of B cells into plasma cells could allow identifying new therapeutic targets. Follicular helper T cells (T_FH) represent a distinct subset of CD4⁺ T cells specialized in providing help to B cells. They are required for the formation of germinal centers and the generation of long-lived serological memory and, as such, are suspected to play a central role in SLE. Recent advances in the field of T_FH biology have allowed the identification of important molecular factors involved in T_FH differentiation, regulation, and function. Interestingly, some of these T_FH-related molecules have been described to be dysregulated in lupus patients. In the present review, we give an overview of the aberrant expression and/or function of such key players in lupus, and we highlight their potential as therapeutic targets.

Recent advances and current state of immunotherapy in systemic lupus erythematosus

INTRODUCTION

Systemic lupus erythematosus (SLE) is an autoimmune syndrome that poses significant challenges in diagnosis and treatment. Dysregulated innate and adaptive immune systems are involved in its pathogenesis. A plethora of novel immunotherapies have been developed for the treatment of SLE but many have failed early clinical trials.

AREAS COVERED

This review summarizes immunotherapies under recent development with relevance to the targeted cellular or soluble factors involved in the pathogenesis of SLE.

EXPERT OPINION

SLE is a complicated disease with much heterogeneity. Novel immunotherapies with different mechanisms of action that are currently under development include biologic agents targeting co-stimulatory molecules, cytokines or their receptors and signaling molecules and B cells, cell-based therapy and peptide therapy. Together with good scientific rationale and advanced biological engineering techniques, optimization of clinical trial design, patient selection and disease outcome measures are essential to demonstrate the clinical efficacy and safety of these agents.

First-in-human trial of the safety, pharmacokinetics and immunogenicity of a PEGylated anti-CD40L antibody fragment (CDP7657) in healthy individuals and patients with systemic lupus erythematosus

OBJECTIVE

The objective of this paper is to investigate the safety, pharmacokinetics (PK) and immunogenicity of CDP7657, a PEGylated anti-CD40L antibody fragment, in healthy individuals and patients with systemic lupus erythematosus (SLE).

METHODS

This randomized, double-blind, single-dose, dose-escalation phase I study consisted of two parts. In part 1, 28 healthy individuals received CDP7657 IV (0.004-5 mg/kg) or placebo. In part 2, 17 patients with SLE received CDP7657 IV (5-60 mg/kg) or placebo. The CDP7657:placebo ratio was 3:1.

RESULTS

Adverse events (AEs) were reported by 76% of healthy individuals and 100% of patients with SLE treated with CDP7657; most were mild or moderate in intensity. Two healthy individuals reported serious AEs (SAEs), one of which was considered treatment related (infusion-related reaction; 5 mg/kg cohort). One patient with SLE (60 mg/kg cohort) experienced three SAEs, one of which was considered treatment related (herpes zoster infection). No thromboembolic events were reported. CPD7657 exposure increased in a dose-proportional manner. Low anti-CDP7657 antibody titres were detected in the majority of CDP7657-treated participants with no apparent impact on the PK of CDP7657.

CONCLUSION

Single doses of CDP7657 showed predictable PK in healthy individuals and patients with SLE and were well tolerated, with no safety signals of concern. These findings support further investigation of CDP7657 as a therapy for SLE.

Costimulatory pathways: physiology and potential therapeutic manipulation in systemic lupus erythematosus

System lupus erythematosus (SLE) is an immune-complex-mediated autoimmune condition with protean immunological and clinical manifestation. While SLE has classically been advocated as a B-cell or T-cell disease, it is unlikely that a particular cell type is more pathologically predominant than the others. Indeed, SLE is characterized by an orchestrated interplay amongst different types of immunopathologically important cells participating in both innate and adaptive immunity including the dendritic cells, macrophages, neutrophils and lymphocytes, as well as traditional nonimmune cells such as endothelial, epithelial, and renal tubular cells. Amongst the antigen-presenting cells and lymphocytes, and between lymphocytes, the costimulatory pathways which involve mutual exchange of information and signalling play an essential role in initiating, perpetuating, and, eventually, attenuating the proinflammatory immune response. In this review, advances in the knowledge of established costimulatory pathways such as CD28/CTLA-4-CD80/86, ICOS-B7RP1, CD70-CD27, OX40-OX40L, and CD137-CD137L as well as their potential roles involved in the pathophysiology of SLE will be discussed. Attempts to target these costimulatory pathways therapeutically will pave more potential treatment avenues for patients with SLE. Preliminary laboratory and clinical evidence of the potential therapeutic value of manipulating these costimulatory pathways in SLE will also be discussed in this review.

LTβR and CD40: working together in dendritic cells to optimize immune responses

Generating an immune response tailored to destroy an infecting organism while limiting bystander damage involves guiding T-cell activation using a variety of cues taken from the immunogen (antigen type, dose, and persistence, accompanying danger signals) as well as the host (tissue environment, T-cell frequency, and affinity for antigen). Dendritic cells (DCs) serve as translators of much of this information and are critically required for effective pathogen and tumor clearance. Moreover, dysregulation of DC activation can lead to autoimmunity. Inhibition of the lymphotoxin (LT) and CD40 pathways has been shown to be effective at quieting inflammation in settings where DC-T-cell interactions are key instigators of disease progression. In this review, we compare and contrast the CD40 and LT pathways in the context of receptor/ligand expression, signal transduction, and DC biology. We provide evidence that these two pathways play complementary roles in DC cytokine secretion, thus indirectly shaping the nature of the CD8(+) T-cell response to foreign antigen. Given the distinct role of these pathways in the context of DC function, we propose that dual therapies targeted at both the CD40 and LTβ receptor may have therapeutic potential in silencing DC-driven autoimmunity or in promoting tumor clearance.

Cyclosporine-resistant, Rab27a-independent mobilization of intracellular preformed CD40 ligand mediates antigen-specific T cell help in vitro

CD40L is critically important for the initiation and maintenance of adaptive immune responses. It is generally thought that CD40L expression in CD4(+) T cells is regulated transcriptionally and made from new mRNA following Ag recognition. However, recent studies with two-photon microscopy revealed that most cognate interactions between effector CD4(+) T cells and APCs are too short for de novo synthesis of CD40L. Given that effector and memory CD4(+) T cells store preformed CD40L (pCD40L) in lysosomal compartments and that pCD40L comes to the cell surface within minutes of antigenic stimulation, we and others have proposed that pCD40L might mediate T cell-dependent activation of cognate APCs during brief encounters in vivo. However, it has not been shown that this relatively small amount of pCD40L is sufficient to activate APCs, owing to the difficulty of separating the effects of pCD40L from those of de novo CD40L and other cytokines in vitro. In this study, we show that pCD40L surface mobilization is resistant to cyclosporine or FK506 treatment, while de novo CD40L and cytokine expression are completely inhibited. These drugs thus provide a tool to dissect the role of pCD40L in APC activation. We find that pCD40L mediates selective activation of cognate but not bystander APCs in vitro and that mobilization of pCD40L does not depend on Rab27a, which is required for mobilization of lytic granules. Therefore, effector CD4(+) T cells deliver pCD40L specifically to APCs on the same time scale as the lethal hit of CTLs but with distinct molecular machinery.

Therapeutic interventions targeting CD40L (CD154) and CD40: the opportunities and challenges

CD40 was originally identified as a receptor on B-cells that delivers contact-dependent T helper signals to B-cells through interaction with CD40 ligand (CD40L, CD154). The pivotal role played by CD40-CD40L interaction is illustrated by the defects in B-lineage cell development and the altered structures of secondary lymphoid tissues in patients and engineered mice deficient in CD40 or CD40L. CD40 signaling also provides critical functions in stimulating antigen presentation, priming of helper and cytotoxic T-cells and a variety of inflammatory reactions. As such, dysregulations in the CD40-CD40L costimulation pathway are prominently featured in human diseases ranging from inflammatory conditions to systemic autoimmunity and tissue-specific autoimmune diseases. Moreover, studies in CD40-expressing cancers have provided convincing evidence that the CD40-CD40L pathway regulates survival of neoplastic cells as well as presentation of tumor-associated antigens to the immune system. Extensive research has been devoted to explore CD40 and CD40L as drug targets. A number of anti-CD40L and anti-CD40 antibodies with diverse biological effects are in clinical development for treatment of cancer and autoimmune diseases. This chapter reviews the role of CD40-CD40L costimulation in disease pathogenesis, the characteristics of therapeutic agents targeting this pathway and status of their clinical development.

Physiopathologie du lupus érythémateux systémique

Innate immunity is directly implicated in the pathophysiology of lupus through the dendritic cell system and the activation by immune complexes of some toll-like receptors (TLR). Interferon-alpha plays a key role in the pathophysiology of lupus and represents a promising target for immune therapy. Dendritic cells are activated and able to capture large quantities of nuclear antigen-containing bodies to stimulate specific adaptive immune response.

Increased levels of NF-ATc2 differentially regulate CD154 and IL-2 genes in T cells from patients with systemic lupus erythematosus

T cells from patients with systemic lupus erythematosus (SLE) are characterized by heightened TCR-initiated free intracytoplasmic calcium responses. We demonstrate that activated T cells from SLE patients, but not from rheumatoid arthritis patients, displayed higher levels of the calcineurin-dependent transcription factor NF-ATc2 in the nucleus compared with control T cells. DNA NF-AT-binding activity was also increased, as was the amount of NF-ATc2 bound to the promoters of CD154 (CD40L) and IL-2 genes. Nevertheless, although high NF-ATc2 levels translated into higher CD154 transcription in SLE, IL-2 transcription was decreased. The absence of important transcriptional activators (AP-1, NF-kappaBeta) and the presence of transcriptional repressors (cAMP response element modulator) on the IL-2 promoter explain this dichotomous effect.

Trichostatin A down-regulates ZAP-70, LAT and SLP-76 content in Jurkat T cells

We exploited Jurkat leukemia T cell clone E6-1 as a model of Trichostatin A (TSA) effect on cellular levels of ZAP-70, LAT and SLP-76 molecules involved in the signal transduction pathway from T cell receptor to nucleus. Using reverse transcription real-time quantitative PCR and Western blotting analysis we observed that TSA resulted in ZAP-70, LAT and SLP-76 transcript and protein down-regulation in Jurkat leukemia T cells. We also found that TSA reduced half-life of ZAP-70, LAT and SLP-76 mRNAs from 4.8, 3.5, and 4.8 to approximately 2.3, 1.9 and 1.7 h, respectively. Employing the protein biosynthesis inhibitor cycloheximide, we demonstrated the involvement of RNase and/or mRNA stabilization protein in ZAP-70, LAT and SLP-76 mRNAs stabilization. The effect of TSA on ZAP-70, LAT and SLP-76 content in T cells confirms an immunosuppressive effect by TSA, and the usefulness of this histone deacetylase inhibitor in the treatment of autoimmune diseases.

Increased expression of the FoxP3 functional marker of regulatory T cells following B cell depletion with rituximab in patients with lupus nephritis

B cell depletion may affect T cell activation and costimulation status in rituximab-treated patients with SLE. We examined whether rituximab administration in patients with active lupus nephritis is related to changes in mRNA expression of genes that define regulatory T cells (Tregs) in peripheral blood lymphocytes, measured by real-time PCR. At the early phase of B cell depletion mRNA levels of CD25, CTLA-4, GITR and the bona fide Treg functional marker FOXP3 increased significantly in all 7 patients examined. In contrast, mRNA levels of the costimulatory/activation T cell molecule CD40L were profoundly reduced, while mRNA levels of TGF-beta, a cytokine contributing to Treg induction, increased significantly in all. During follow-up, increased FOXP3 mRNA persisted in those patients in clinical remission, while in those patients with active disease subsequent decreases were noted. Further studies should examine whether modulation of Tregs by therapeutic B cell depletion contributes and/or predicts lupus disease remission.

CD40 ligand binds to alpha5beta1 integrin and triggers cell signaling

It was originally thought that the critical role of the CD40 ligand (CD40L) in normal and inflammatory immune responses was mainly mediated through its interaction with the classic receptor, CD40. However, data from CD40L(-/-) and CD40(-/-) mice suggest that the CD40L-induced inflammatory immune response involves at least one other receptor. This hypothesis is supported by the fact that CD40L stabilizes arterial thrombi through an alphaIIbbeta3-dependent mechanism. Here we provide evidence that soluble CD40L (sCD40L) binds to cells of the undifferentiated human monocytic U937 cell line in a CD40- and alphaIIbbeta3-independent manner. Binding of sCD40L to U937 cells was inhibited by anti-CD40L monoclonal antibody 5C8, anti-alpha5beta1 monoclonal antibody P1D6, and soluble alpha5beta1. The direct binding of sCD40L to purified alpha5beta1 was confirmed in a solid phase binding assay. Binding of sCD40L to alpha5beta1 was modulated by the form of alpha5beta1 expressed on the cell surface as the activation of alpha5beta1 by Mn(2+) or dithiothreitol resulted in the loss of sCD40L binding. Moreover, sCD40L induced the translocation of alpha5beta1 to the Triton X-100-insoluble fraction of U937 cells, the rapid activation of the MAPK pathways ERK1/2, and interleukin-8 gene expression. The binding of sCD40L to CD40 on BJAB cells, an alpha5beta1-negative B cell line, and the resulting activation of ERK1/2 was not inhibited by soluble alpha5beta1, suggesting that sCD40L can bind concomitantly to both receptors. These results document the existence of novel CD40L-dependent pathways of physiological relevance for cells expressing multiple receptors (CD40, alpha5beta1, and alphaIIbbeta3) for CD40L.

Update on the treatment of lupus nephritis

Lupus nephritis (LN) is a major cause of morbidity and mortality in patients with systemic lupus erythematosus. Although the use of aggressive immunosuppression has improved both patient and renal survival over the past several decades, the optimal treatment of LN remains challenging. Improved outcomes have come at the expense of significant adverse effects owing to therapy. Moreover with long-term survival, the chronic adverse effects of effective therapies including risk of malignancy, atherosclerosis, infertility, and bone disease all become more important. Finally, some patients fail to achieve remission with standard cytotoxic therapy and others relapse when therapy is reduced. For these reasons, recent clinical trials have attempted to define alternate treatment protocols that appear to be efficacious in achieving and maintaining remission, but with less toxicity than standard regimens. This paper discusses established and newer treatment options for patients with proliferative and membranous LN, with an emphasis on the results of these recent clinical trials. We also review the experimental and human data regarding some of the novel targeted forms of therapy that are under investigation and in different phases of clinical trials.

Rituximab anti-B-cell therapy in systemic lupus erythematosus: pointing to the future

PURPOSE OF REVIEW

To discuss the clinical effects and the immunologic consequences of transient B-cell depletion using the anti-CD20 monoclonal antibody rituximab in systemic lupus erythematosus.

RECENT FINDINGS

A total of 100 rituximab-treated patients with severe disease, refractory to major immunosuppressive treatment, have been reported so far. Within a median follow-up period of 12 months rituximab was well tolerated, which is compatible with the experience accumulated from its use in more than 500 000 lymphoma patients. About 80% of patients achieved marked and rapid reductions in global disease activity. Because of the clinical heterogeneity, dosing differences, and concomitant treatments, including cyclophosphamide in 35% of patients, a proper evaluation of the clinical efficacy or rituximab is difficult. Variable degrees of clinical benefit have been reported for all clinical systemic lupus erythematosus manifestations, including active proliferative nephritis. Whereas 4-weekly infusions of 375 mg/m of rituximab result in complete B-cell depletion lasting most often from 3 to 8 months, a prolonged depletion does not always correlate with a more favorable clinical response. Total immunoglobulin levels and protective antibodies are preserved, but anti-dsDNA antibody titers decrease, often independently of the clinical response.

SUMMARY

The findings reviewed point to a growing optimism for targeting B cells in the treatment of systemic lupus erythematosus; therefore double-blind studies comparing rituximab with existing immunosuppressive therapies are needed. Moreover, careful assessments of the effects of transient B-cell depletion on distinct autoimmune pathogenetic processes will enable optimization of therapeutic single or combined therapeutic schemes.

Remission of proliferative lupus nephritis following B cell depletion therapy is preceded by down-regulation of the T cell costimulatory molecule CD40 ligand: an open-label trial

OBJECTIVE

Autoreactive B cells play a key role in tissue injury in systemic autoimmune disease, and therefore a treatment resulting in B cell depletion could have benefit. This open-label study was undertaken to evaluate the efficacy of the anti-CD20 monoclonal antibody rituximab in the treatment of lupus nephritis.

METHODS

Lupus patients with active proliferative nephritis (4 with focal disease and 6 with diffuse disease) received rituximab (4 weekly infusions of 375 mg/m(2)) combined with oral prednisolone. Clinical, laboratory, and immunologic responses, including peripheral lymphocyte subsets measured by flow cytometry, were prospectively assessed at monthly intervals for 12 months. Complete remission of nephritis was defined as normal serum creatinine and albumin levels, inactive urine sediment, and 24-hour urinary protein <500 mg. Partial remission was defined as >50% improvement in all renal parameters that were abnormal at baseline.

RESULTS

B cell depletion lasted from 1 month to 7 months and was well tolerated. Partial remission was achieved in 8 of 10 patients within a median of 2 months (range 1-4 months); in 5 of them, complete remission was subsequently established (at a median of 3 months from baseline), and it was sustained at 12 months in 4. As early as 1 month from baseline, the expression of the costimulatory molecule CD40 ligand on CD4+ T cells was decreased by 4-fold, and it was almost blocked when partial remission was clinically evident. The expression of T cell activation markers CD69 and HLA-DR was significantly decreased at time points when partial remission was observed, and was further decreased during complete remission. In contrast, in patients who did not exhibit a response or when relapse was detected in patients in whom an initial remission had been achieved, such decreases were not prominent. Serum concentrations of double-stranded DNA autoantibodies were decreased in all patients, regardless of clinical outcome.

CONCLUSION

Following B cell depletion, clinical remission of lupus nephritis is associated with a decrease in T helper cell activation, suggesting an additional role for B cells, independent of autoantibody production, in promoting disease. A controlled trial to confirm these promising clinical results is warranted.

IL-10 production in B cells is confined to CD154+ cells in patients with systemic lupus erythematosus

The immunological hallmark of SLE is B cell hyperactivity. CD154 (CD40-L) is normally expressed in activated T cells, and plays an important role in T-B interactions. Its expression is increased in SLE T cells. Additionally, its expression on B cells leads to the development of SLE-like disease in a transgenic model. IL-10 is a key cytokine in the disturbed SLE immune system. The aim of this work was to explore the relation between IL-10 and CD154 expression in SLE B cells. We studied 11 SLE patients and 10 healthy volunteers. Mononuclear cells were isolated from peripheral blood and cultured in the presence or absence of Cowan I Strain Staphylococcus (CSS). Surface CD154 and intracytoplasmic IL-10 expression were quantified with flow cytometry. In basal conditions, CD154 expression was not different in patients and controls. B cell stimulation did not cause a significant increase in CD154 expression in control B cells. However, its expression increased 2 times in B cells obtained from SLE patients. IL-10 expression was confined to CD154(+) cells. Our results show that IL-10 production is intimately linked to CD154 expression in B cells, and that the IL-10(+)CD154(+) B cell subset increases abnormally when SLE-derived cells are stimulated with CSS.

CD40/CD154 interactions at the interface of tolerance and immunity

Development of the acquired immune response is dependent on the signaling of CD40 by its ligand, CD154. These molecules govern both the magnitude and quality of humoral- and cell-mediated immunity. A litany of studies have conclusively documented that blockade of this ligand-receptor pair can prevent, and also intervene in, the progression of antibody- and cell-mediated autoimmune diseases, and can instill long-lived allogeneic and xenogeneic graft tolerance. Many effector mechanisms of inflammation are abolished as a result of CD154 blockade, but we are now beginning to understand that CD154 blockade may, in some instances, engender long-lived, antigen-specific tolerance. In the context of transplantation tolerance, we present a hypothesis that alpha CD154 blockade is most effective at inducing long-lived allospecific tolerance if anergy and regulation can be elicited prior to the onslaught of inflammation that is induced by grafting (preemptive tolerance). This facet of alpha CD154-induced tolerance appears to co-opt the normal processes of peripheral tolerance induced by immature DCs and can be exploited to induce long-lived antigen-specific tolerance. The underlying science and the prospects for inducing long-lived antigen-specific tolerance in a model of allograft tolerance through CD154 blockade are presented and discussed.

Costimulation Blockade in the Treatment of Rheumatic Diseases

The autoimmune response is executed via cognate interactions between effector immune cells and antigen presenting cells. Cognate interactions provide the immune effectors with specific signals generated through the antigen receptor as well as with second, non-specific signals, generated from the interaction of pairs of cell-surface molecules (costimulatory molecules) present on their plasma membrane. Disruption of this second, non-specific costimulatory signal results in the interruption of the productive (auto)immune response, leading to anergy, a state of immune unresponsiveness. The CD28:B7 families of molecules and the CD40:CD40L pair of molecules are considered as critical costimulatory elements. Disruption of the CD28:B7 interaction using a genetically engineered soluble form of the inhibitory molecule CTLA4 in vitro, as well as in experimental models of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), led to the inhibition of the autoimmune response. Similarly, promising data stem from the use of an anti-CD40L monoclonal antibody (mAb) in murine SLE. While such treatments prevent the development of autoimmunity in animal models, this preventive approach is inapplicable to human diseases. However, the rational bench-to-bedside approach led investigators to clinical trials of CTLA4-Ig and of two different humanized anti-human CD40L mAbs in patients with RA and SLE, respectively. Initial experience with the use of CTLA4-Ig in patients with RA is encouraging, since in one short-term trial the construct was well-tolerated and produced clinically meaningful improvement of the disease in a significant proportion of those treated. Surprisingly, the anti-CD40L mAb treatment approach in human lupus was not fruitful, since short-term administration of the anti-CD40L mAb ruplizumab in lupus nephritis was correlated with life-threatening prothrombotic activity despite initial encouraging data in the serology and renal function of the patients. Also, IDEC-131 anti-CD40L mAb treatment did not prove to be clinically effective in human SLE, despite being well tolerated. Precise tailoring of the administration schemes for these novel therapeutic modalities is awaited.Finally, conceptually different approaches to block costimulation by inhibiting the induced expression of costimulatory molecules or the transmission of their specific intracytoplasmic signal have already produced encouraging preliminary results.