Treatment of murine lupus with CTLA4Ig

Immunological characterization of de novo and recall alloantibody suppression by CTLA4Ig in a mouse model of allosensitization

It is well known that CTLA4Ig inhibits allogenic T-cell activation in transplantation. The immunological features and mechanisms associated with alloantibody suppression by CTLA4Ig, however, are poorly understood. Here, we used a mouse model of allosensitization to evaluate the efficacy of CTLA4Ig (abatacept) in suppression of donor-specific antibody (DSA) during de novo and recall alloantibody responses. We found that abatacept inhibited de novo DSA IgM and IgG responses to HLA-A2 expressing skin grafts. Abatacept administered during primary T cell priming also reduced recall IgG responses induced by re-immunization. Suppression of de novo DSA responses by abatacept is associated with a reduction in splenic expression of the germinal center activation marker GL7 and a reduction of CD4(+)PD1(+)CXCR5(+) follicular T helper (Tfh) subset in splenic lymphocytes detected by flow cytometry. The efficacy of abatacept on recall DSA suppression is moderate. In vitro experiments demonstrated that abatacept inhibited DSA IgG secretion by CD138(+) plasma cells isolated from allograft recipients. Additional experiments using an IgG1 secreting mouse hybridoma cell line showed that abatacept binds to CD80 expressed on these cells with subsequent inhibition of cell proliferation and reduction in IgG ELISpot formation. In conclusion, CTLA4Ig is a potent suppressor of de novo DSA responses and also affects recall responses. The data suggests modification of recall DSA responses is due to a direct suppressive effect on plasma cells.

Rethinking biologics in lupus nephritis

Lupus nephritis (LN) is a chronic and devastating complication of systemic lupus erythematosus. Despite advances in our understanding of LN and the availability of effective therapies, LN remains a difficult clinical problem, and progression to end stage renal disease remains a significant challenge. Though the advent of biologics has revolutionized the treatment of many rheumatological conditions, and several clinical trials of biologics have been conducted in LN, the promise of biologics remains unfulfilled. The experience gained from these initial clinical trials can help tailor approaches in future clinical trials, and the lessons learned can be applied to find a cure for this condition.

Immunoregulatory soluble CTLA-4 modifies effector T-cell responses in systemic lupus erythematosus

Background

The inhibitory CTLA-4 molecule is a crucial regulator of immune responses and a target for therapeutic intervention in both autoimmunity and cancer. In particular, CTLA-4 is important in controlling antigen-specific immunity, including responses to autoantigens associated with autoimmune disease. Here, we investigate cytokine responses to a range of lupus-associated autoantigens and assess whether the alternatively spliced isoform of CTLA-4, soluble CTLA-4 (sCTLA-4), contributes to immune regulation of autoantigen-specific immunity in systemic lupus erythematosus (SLE).

Methods

The cell culture supernatant production of sCTLA-4 as well as the cytokines IL-10, IFN-γ, and IL-17 from peripheral blood mononuclear cells (PBMC) from lupus patients and age- and sex-matched healthy volunteer donors were measured in response to previously identified histone and small nuclear ribonucleoprotein (snRNP) autoantigen-derived peptides (H3_91-105, H4_71-93, and U170K_131-151) by ELISA. We also examined the functional contribution of sCTLA-4 to immune regulation in the context of these autoantigenic peptides following blockade of sCTLA-4 with a selective anti-sCTLA-4 monoclonal antibody, JMW-3B3.

Results

We identified responses to autoantigenic peptides, which revealed qualitative differences in cytokine (IL-10, IL-17, and IFN-γ) profiles between SLE patients and healthy donors. PBMC from healthy donors responded to each of the lupus peptides by secreting IFN-γ and IL-17, but PBMC from SLE patients produced IL-10. Although we did not observe differences in the levels of serum or PBMC culture supernatant sCTLA-4 in either cohort, blockade of sCTLA-4 in PBMC cultures responding to antigen enhanced the cytokine profiles associated with each group.

Conclusion

The results show that lupus autoantigen-derived peptides display varied immunogenicity in lupus versus healthy volunteer donors, while sCTLA-4 acts to regulate the T-cell activity independently of response profile.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1075-1) contains supplementary material, which is available to authorized users.

Review: Systemic lupus erythematosus in children: current and emerging therapies

Treatment of children with systemic lupus erythematosus (SLE) is challenging. The therapeutic issues and risks and balances faced by adult patients are further complicated by an unpredictable disease course and long requirement for therapy in children with SLE. Further, non-compliance is a major obstacle to satisfactory outcome which must be recognized and dealt with in every adolescent in our efforts to attain optimal outcome. Treatment with combinations of cytotoxic agents and biologics which result in significant B-cell depletion often provide improved disease control. As our knowledge of the pathogenesis of SLE delineates more specific targets for immunotherapy the incidence of long-term remission rises. Our current emphasis is on therapeutic regimens which will induce remission followed by maintenance therapy in the oncologic model. SLE like neoplastic disease is no longer simply `treatable'. With appropriate therapy many children with SLE attain sustained remissions. In the foreseeable future childhood SLE may be curable. Lupus (2007) 16, 677—683.

Cyclophosphamide in lupus nephritis

Although not licensed for systemic lupus erythematosus (SLE), cyclophosphamide (CYC) has become over the last two decades the most widely prescribed cytotoxic drug for lupus nephritis (LN). A PubMed search using ‘lupus nephritis and cyclophosphamide’ as key words identifies not less than 454 papers on the topic. This should, however, not disguise the fact that its use is still controversial and that many issues remain debated, such as the timing and length of treatment, the route of administration and the ideal dosage. In this review, the different CYC regimes on the basis of the results of prospective randomized trials performed in LN patients is discussed.

Expression and activity analyses of CTLA4 in peripheral blood lymphocytes in systemic lupus erythematosus patients

The objective of this study was to determine the expression and activity of CTLA4 in T-cells of systemic lupus erythematosus (SLE) patients. Expression of CTLA4 on freshly isolated peripheral blood T-cells was evaluated in 33 SLE patients and 25 controls using flow cytometry.The T-cells from 19 SLE patients and 22 controls were stimulated and cultured with Chinese hamster ovary cells expressing CD80 (CHO-CD80) or with CHO cells. T-cell proliferation was determined with [3H] thymidine incorporation (CPM), and the inhibitory effect of CTLA4 on T-cell proliferation was evaluated by the ratio of CPM for T-cells with CHO -CD80 cells to that of T-cells with CHO cells (the CHO -CD80/CHO ratio). IntracellularCTLA4 expressionin freshly isolated peripheral blood T-cells was significantly higher in SLE patients than the controls (P < 0.05), but there was no correlation with clinical features or disease activity. The CHO -CD80/CHO ratio of SLE patients was significantly higher than that of the controls(P < 0.05). Among SLE patients, the CHO -CD80/CHO ratio of patients with lupus nephritis was significantly higher than that of patients without lupus nephritis (P < 0.05). In conclusion, our data suggest that CTLA4 expression is not impaired in SLE patients, but there is a possibility of decreased inhibitory effect of CTLA4 involved in the pathogenesis of SLE.

Novel therapies in lupus nephritis

Renal disease continues to cause major morbidity and some mortality for around 30-40% of patients with systemic lupus erythematosus (SLE). Although the combinations of prednisolone and azathioprine or prednisolone and cyclophosphamide have been beneficial to many patients with SLE, they are not always effective and have significant side effects. It is very encouraging that new immunosuppressive drugs such as mycophenolate mofetil and more targeted therapies e.g., anti-CD20 are coming rapidly to larger scale clinical trials. The treatment of lupus nephritis is set to change quite rapidly in the next decade. In this review we highlight the likely major therapeutic advances.

Theory, targets and therapy in systemic lupus erythematosus

The treatment of systemic lupus erythematosus (SLE) has been refined over the years, with the recognition that a fine balance lies between aggressive and prompt therapy and attendant complications brought upon by immunosuppressive therapy itself. However, there has been limited change to the repertoire of drugs available to treat this challenging disease. The current standard therapy for severe manifestations of SLE includes the use of high-dose corticosteroids and cytotoxic agents such as cyclophosphamide (CYC), which have been associated with an increased risk of serious and opportunistic infections. The need for safer, more targeted therapies has been recognized and now, with the exponential increase in the understanding of immunopathogenic mechanisms in SLE, the way has been paved for the development of biologic or targeted therapies in SLE. Although the potential immunosuppression, long-term safety issues and cost-effectiveness remain unclear. These targeted therapies may range from small molecules that specifically inhibit inflammatory processes at an intracellular, cell-cell or cell-matrix level to monoclonal antibodies, soluble receptors or natural antagonists that interfere with cytokine function, cellular activation and inflammatory gene transcription.

CD28 Costimulation: From Mechanism to Therapy

Ligation of the CD28 receptor on T cells provides a critical second signal alongside T cell receptor (TCR) ligation for naive T cell activation. Here, we discuss the expression, structure, and biochemistry of CD28 and its ligands. CD28 signals play a key role in many T cell processes, including cytoskeletal remodeling, production of cytokines, survival, and differentiation. CD28 ligation leads to unique epigenetic, transcriptional, and post-translational changes in T cells that cannot be recapitulated by TCR ligation alone. We discuss the function of CD28 and its ligands in both effector and regulatory T cells. CD28 is critical for regulatory T cell survival and the maintenance of immune homeostasis. We outline the roles that CD28 and its family members play in human disease and we review the clinical efficacy of drugs that block CD28 ligands. Despite the centrality of CD28 and its family members and ligands to immune function, many aspects of CD28 biology remain unclear. Translation of a basic understanding of CD28 function into immunomodulatory therapeutics has been uneven, with both successes and failures. Such real-world results might stem from multiple factors, including complex receptor-ligand interactions among CD28 family members, differences between the mouse and human CD28 families, and cell-type specific roles of CD28 family members.

Biologics for the treatment of autoimmune renal diseases

Biological therapeutics (biologics) that target autoimmune responses and inflammatory injury pathways have a marked beneficial impact on the management of many chronic diseases, including rheumatoid arthritis, psoriasis, inflammatory bowel disease, and ankylosing spondylitis. Accumulating data suggest that a growing number of renal diseases result from autoimmune injury - including lupus nephritis, IgA nephropathy, anti-neutrophil cytoplasmic antibody-associated glomerulonephritis, autoimmune (formerly idiopathic) membranous nephropathy, anti-glomerular basement membrane glomerulonephritis, and C3 nephropathy - and one can speculate that biologics might also be applicable to these diseases. As many autoimmune renal diseases are relatively uncommon, with long natural histories and diverse outcomes, clinical trials that aim to validate potentially useful biologics are difficult to design and/or perform. Some excellent consortia are undertaking cohort studies and clinical trials, but more multicentre international collaborations are needed to advance the introduction of new biologics to patients with autoimmune renal disorders. This Review discusses the key molecules that direct injurious inflammation and the biologics that are available to modulate them. The opportunities and challenges for the introduction of relevant biologics into treatment protocols for autoimmune renal diseases are also discussed.

Current and emerging treatment options in the management of lupus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease with variable clinical manifestations. While the clearest guidelines for the treatment of SLE exist in the context of lupus nephritis, patients with other lupus manifestations such as neuropsychiatric, hematologic, musculoskeletal, and severe cutaneous lupus frequently require immunosuppression and/or biologic therapy. Conventional immunosuppressive agents such as mycophenolate mofetil, azathioprine, and cyclophosphamide are widely used in the management of SLE with current more rationalized treatment regimens optimizing the use of these agents while minimizing potential toxicity. The advent of biologic therapies has advanced the treatment of SLE particularly in patients with refractory disease. The CD20 monoclonal antibody rituximab and the anti-BLyS agent belimumab are now widely in use in clinical practice. Several other biologic agents are in ongoing clinical trials. While immunosuppressive and biologic agents are the foundation of inflammatory disease control in SLE, the importance of managing comorbidities such as cardiovascular risk factors, bone health, and minimizing susceptibility to infection should not be neglected.

CD28 Deficiency Enhances Type I IFN Production by Murine Plasmacytoid Dendritic Cells

Type I IFNs (IFN-I) are key innate mediators that create a profound antiviral state and orchestrate the activation of almost all immune cells. Plasmacytoid dendritic cells (pDCs) are the most powerful IFN-I-producing cells and play important roles during viral infections, cancer, and autoimmune diseases. By comparing gene expression profiles of murine pDCs and conventional DCs, we found that CD28, a prototypic T cell stimulatory receptor, was highly expressed in pDCs. Strikingly, CD28 acted as a negative regulator of pDC IFN-I production upon TLR stimulation but did not affect pDC survival or maturation. Importantly, cell-intrinsic CD28 expression restrained pDC (and systemic) IFN-I production during in vivo RNA and DNA viral infections, limiting antiviral responses and enhancing viral growth early after exposure. Finally, CD28 also downregulated IFN-I response upon skin injury. Our study identified a new pDC regulatory mechanism by which the same CD28 molecule that promotes stimulation in most cells that express it is co-opted to negatively regulate pDC IFN-I production and limit innate responses.

Progress with the use of monoclonal antibodies for the treatment of systemic lupus erythematosus

In recent years, significant progress has been made in the use of monoclonal antibodies in the treatment of systemic lupus erythematosus (SLE). Advances in our understanding of the complexity of SLE immunopathogenesis have led to the testing of several biologic agents in clinical trials. Monoclonal therapies currently emerging or under development include B-cell depletion therapies, agents targeting B-cell survival factors, blockade of T-cell co-stimulation and anticytokine therapies. Issues remain, however, regarding clinical trial design and outcome measures in SLE which need to be addressed to optimize translation of these promising therapies into clinical practice.

Key issues in the management of patients with systemic lupus erythematosus: latest developments and clinical implications

Systemic lupus erythematous (SLE) is a chronic multisystem disease with significant associated morbidity and mortality. A deeper understanding of the pathogenesis of SLE has led to the development of biologic agents, primarily targeting B cells and others inhibiting costimulatory molecules, type I interferons and cytokines such as interleukin-6. Several of these agents have been studied in clinical trials; some have shown promise while others have yielded disappointing results. Economic and regulatory issues continue to hamper the availability of such therapies for SLE patients. With increasing recognition that recurrent flares of disease activity lead to long-term damage accrual, one of the most important recent developments in patient management has been the concept of treat-to-target in SLE while minimizing patient exposure to excessive corticosteroid and other immunosuppressive therapy. This article reviews these key issues in SLE management, outlining recent developments and clinical implications for patients.

Targeting the alternatively spliced soluble isoform of CTLA-4: prospects for immunotherapy?

CTLA-4 is an inhibitory protein that contributes to immune homeostasis and tolerance, a role that has led to its exploitation as a therapeutic in several clinical settings including cancer and autoimmune disease. Development of CTLA-4 therapies focused largely on the full-length receptor isoform but other CTLA-4 isoforms are also expressed, including a secretable form of CTLA-4 (soluble CTLA-4 [sCTLA-4]). The contribution of sCTLA-4 to immune regulation has been less well studied, primarily because it was identified some years after the original description of CTLA-4. Here, we examine how sCTLA-4 might contribute to immune regulation and ask whether it might be a biomarker to inform current CTLA-4 therapies or represent a novel CTLA-4 target for future therapeutics.

Immunogenetics of autoimmune thyroid diseases: A comprehensive review

Both environmental and genetic triggers factor into the etiology of autoimmune thyroid disease (AITD), including Graves' disease (GD) and Hashimoto's thyroiditis (HT). Although the exact pathogenesis and causative interaction between environment and genes are unknown, GD and HT share similar immune-mediated mechanisms of disease. They both are characterized by the production of thyroid autoantibodies and by thyroidal lymphocytic infiltration, despite being clinically distinct entities with thyrotoxicosis in GD and hypothyroidism in HT. Family and population studies confirm the strong genetic influence and inheritability in the development of AITD. AITD susceptibility genes can be categorized as either thyroid specific (Tg, TSHR) or immune-modulating (FOXP3, CD25, CD40, CTLA-4, HLA), with HLA-DR3 carrying the highest risk. Of the AITD susceptibility genes, FOXP3 and CD25 play critical roles in the establishment of peripheral tolerance while CD40, CTLA-4, and the HLA genes are pivotal for T lymphocyte activation and antigen presentation. Polymorphisms in these immune-modulating genes, in particular, significantly contribute to the predisposition for GD, HT and, unsurprisingly, other autoimmune diseases. Emerging evidence suggests that single nucleotide polymorphisms (SNPs) in the immunoregulatory genes may functionally hinder the proper development of central and peripheral tolerance and alter T cell interactions with antigen presenting cells (APCs) in the immunological synapse. Thus, susceptibility genes for AITD contribute directly to the key mechanism underlying the development of organ-specific autoimmunity, namely the breakdown in self-tolerance. Here we review the major immune-modulating genes that are associated with AITD and their potential functional effects on thyroidal immune dysregulation.

Targeting the CD80/CD86 costimulatory pathway with CTLA4-Ig directs microglia toward a repair phenotype and promotes axonal outgrowth

Among the costimulatory factors widely studied in the immune system is the CD28/cytotoxic T-lymphocyte antigen-4 (CTLA4)-CD80/CD86 pathway, which critically controls the nature and duration of the T-cell response. In the brain, up-regulated expression of CD80/CD86 during inflammation has consistently been reported in microglia. However, the role of CD80/CD86 molecules has mainly been studied in a context of microglia-T cell interactions in pathological conditions, while the function of CD80/CD86 in the regulation of intrinsic brain cells remains largely unknown. In this study, we used a transgenic pig line in which neurons express releasable CTLA4-Ig, a synthetic molecule mimicking CTLA4 and binding to CD80/CD86. The effects of CTLA4-Ig on brain cells were analyzed after intracerebral transplantation of CTLA4-Ig-expressing neurons or wild-type neurons as control. This model provided in vivo evidence that CTLA4-Ig stimulated axonal outgrowth, in correlation with a shift of the nearby microglia from a compact to a ramified morphology. In a culture system, we found that the CTLA4-Ig-induced morphological change of microglia was mediated through CD86, but not CD80. This was accompanied by microglial up-regulated expression of the anti-inflammatory molecule Arginase 1 and the neurotrophic factor BDNF, in an astrocyte-dependent manner through the purinergic P2Y1 receptor pathway. Our study identifies for the first time CD86 as a key player in the modulation of microglia phenotype and suggests that CTLA4-Ig-derived compounds might represent new tools to manipulate CNS microglia.

Linking susceptibility genes and pathogenesis mechanisms using mouse models of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) represents a challenging autoimmune disease from a clinical perspective because of its varied forms of presentation. Although broad-spectrum steroids remain the standard treatment for SLE, they have many side effects and only provide temporary relief from the symptoms of the disease. Thus, gaining a deeper understanding of the genetic traits and biological pathways that confer susceptibility to SLE will help in the design of more targeted and effective therapeutics. Both human genome-wide association studies (GWAS) and investigations using a variety of mouse models of SLE have been valuable for the identification of the genes and pathways involved in pathogenesis. In this Review, we link human susceptibility genes for SLE with biological pathways characterized in mouse models of lupus, and discuss how the mechanistic insights gained could advance drug discovery for the disease.

Treatment of lupus nephritis with abatacept: the Abatacept and Cyclophosphamide Combination Efficacy and Safety Study

OBJECTIVE

To assess the efficacy and safety of a 24-week course of abatacept in the treatment of active lupus nephritis and to assess the potential of abatacept to induce "clinical tolerance," defined as sustained clinical quiescence of lupus nephritis after discontinuation of immunosuppressive therapy.

METHODS

Patients with active lupus nephritis (n = 134) were enrolled in a randomized, double-blind phase II add-on trial in which they received either abatacept or placebo in conjunction with the Euro-Lupus Nephritis Trial regimen of low-dose cyclophosphamide (CYC) followed by azathioprine (AZA). The primary efficacy outcome was the frequency of complete response at week 24. Thereafter, patients who met either complete or partial response criteria continued blinded treatment through week 52. During this phase of the study, subjects in the abatacept treatment group in whom a complete response was achieved at week 24 discontinued immunosuppressive therapy other than prednisone (10 mg/day).

RESULTS

There were no statistically significant differences between groups with respect to the primary outcome or any of the secondary outcomes, including measures of safety. A complete response was achieved in 33% of the subjects in the treatment group and in 31% of the subjects in the control group at week 24. Fifty percent of the subjects in the treatment group who met complete response criteria and therefore discontinued immunosuppressive therapy at week 24 maintained their complete response status through week 52.

CONCLUSION

The addition of abatacept to a regimen of CYC followed by AZA did not improve the outcome of lupus nephritis at either 24 or 52 weeks. No worrisome safety signals were encountered.

Biologicals for the treatment of systemic lupus erythematosus: current status and emerging therapies

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease resulting from the dysregulation of various immunological pathways. There has been major progress in recent years in the understanding of the pathogenesis of SLE, which has led to an emergence of a new class of drugs designed to target specific components of the disease process.Evidence from a number of open-label, uncontrolled studies has supported the use of rituximab (an anti-CD20 monoclonal antibody) in SLE for more than one decade. However, these promising results are in clear contrast with the poor results of the completed Efficacy and Safety of Rituximab in Patients with Severe SLE (EXPLORER) and Efficacy and Safety of Rituximab in Subjects with class III or IV Lupus Nephritis (LUNAR) randomized controlled trials. In contrast to EXPLORER and LUNAR results, controlled trials for belimumab (a fully humanized monoclonal antibody against B lymphocyte stimulator) showed positive results and subsequently, belimumab was the first drug approved for the treatment of SLE patients. This has paved the way for the development of further biological agents, potentially revolutionizing the treatment of SLE. In this study, the potential benefits of novel biological agents are explored, obstacles to the development of a treatment target in SLE are identified, and possible strategies to achieve this goal are discussed.

Adult stem cell therapy for autoimmune disease

Many studies of autologous hematopoietic stem cell transplantation (HSCT) and allogeneic HSCT have been conducted for autoimmune disease in various animal models. Because of the substantial risk of morbidity and mortality associated with allogeneic bone marrow transplantation, autologous transplants justified trying this approach in patient with severe autoimmune disease who were refractory to current treatments. Remission was achieved in some of the patients and some of them relapsed. Recently, many in vitro studies have reported that mesenchymal stem cells (MSC) have immunomodulatory properties and immunosuppressive effects on MHC-mismatched lymphocytes proliferation by inhibiting naïve, memory and activated T cells, B cell, NK cells and dendritic cells. In addition, adipose tissue-derived MSC (AT-MSC) are becoming an alternative source of MSC for therapeutic applications because adipose tissues are abundant, easily accessible, easily obtainable with little patient discomfort and large amounts of AT-MSC can be easily obtained. A large body of in vitro research has shown that AT-MSC have same or similar immunomodulatory effects with bone marrow derived MSC. Drawing on this finding, the increasing numbers of researchers have turned on their attention to preclinical studies on AT-MSC. As this new path of research evolves with subsequent reports, MSC would make a significant contribution to stem cell therapy or combination therapy for ameliorating symptoms and curing autoimmune disease. By searching and studying the appropriate therapeutic gene, the therapeutic gene transfected stem cell therapy will be able to acquire the synergy effect and the combined advantage of gene therapy and stem cell therapy.

Novel approaches to the development of targeted therapeutic agents for systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic multisystem disease in which various cell types and immunological pathways are dysregulated. Current therapies for SLE are based mainly on the use of non-specific immunosuppressive drugs that cause serious side effects. There is, therefore, an unmet need for novel therapeutic means with improved efficacy and lower toxicity. Based on recent better understanding of the pathogenesis of SLE, targeted biological therapies are under different stages of development. The latter include B-cell targeted treatments, agents directed against the B lymphocyte stimulator (BLyS), inhibitors of T cell activation as well as cytokine blocking means. Out of the latter, Belimumab was the first drug approved by the FDA for the treatment of SLE patients. In addition to the non-antigen specific agents that may affect the normal immune system as well, SLE-specific therapeutic means are under development. These are synthetic peptides (e.g. pConsensus, nucleosomal peptides, P140 and hCDR1) that are sequences of conserved regions of molecules involved in the pathogenesis of lupus. The peptides are tolerogenic T-cell epitopes that immunomodulate only cell types and pathways that play a role in the pathogenesis of SLE without interfering with normal immune functions. Two of the peptides (P140 and hCDR1) were tested in clinical trials and were reported to be safe and well tolerated. Thus, synthetic peptides are attractive potential means for the specific treatment of lupus patients. In this review we discuss the various biological treatments that have been developed for lupus with a special focus on the tolerogenic peptides.

Investigation of soluble and transmembrane CTLA-4 isoforms in serum and microvesicles

Expression of the CTLA-4 gene is absolutely required for immune homeostasis, but aspects of its molecular nature remain undefined. In particular, the characterization of the soluble CTLA-4 (sCTLA-4) protein isoform generated by an alternatively spliced mRNA of CTLA4 lacking transmembrane-encoding exon 3 has been hindered by the difficulty in distinguishing it from the transmembrane isoform of CTLA-4, Tm-CTLA-4. In the current study, sCTLA-4 has been analyzed using novel mAbs and polyclonal Abs specific for its unique C-terminal amino acid sequence. We demonstrate that the sCTLA-4 protein is secreted at low levels following the activation of primary human CD4⁺ T cells and is increased only rarely in the serum of autoimmune patients. Unexpectedly, during our studies aimed to define the kinetics of sCTLA-4 produced by activated human CD4⁺ T cells, we discovered that Tm-CTLA-4 is associated with microvesicles produced by the activated cells. The functional roles of sCTLA-4 and microvesicle-associated Tm-CTLA-4 warrant further investigation, especially as they relate to the multiple mechanisms of action described for the more commonly studied cell-associated Tm-CTLA-4.

CXCL11-dependent induction of FOXP3-negative regulatory T cells suppresses autoimmune encephalomyelitis

A single G protein-coupled receptor (GPCR) can activate multiple signaling cascades based on the binding of different ligands. The biological relevance of this feature in immune regulation has not been evaluated. The chemokine-binding GPCR CXCR3 is preferentially expressed on CD4+ T cells, and canonically binds 3 structurally related chemokines: CXCL9, CXCL10, and CXCL11. Here we have shown that CXCL10/CXCR3 interactions drive effector Th1 polarization via STAT1, STAT4, and STAT5 phosphorylation, while CXCL11/CXCR3 binding induces an immunotolerizing state that is characterized by IL-10(hi) (Tr1) and IL-4(hi) (Th2) cells, mediated via p70 kinase/mTOR in STAT3- and STAT6-dependent pathways. CXCL11 binds CXCR3 with a higher affinity than CXCL10, suggesting that CXCL11 has the potential to restrain inflammatory autoimmunity. We generated a CXCL11-Ig fusion molecule and evaluated its use in the EAE model of inflammatory autoimmune disease. Administration of CXCL11-Ig during the first episode of relapsing EAE in SJL/J mice not only led to rapid remission, but also prevented subsequent relapse. Using GFP-expressing effector CD4+ T cells, we observed that successful therapy was associated with reduced accumulation of these cells at the autoimmune site. Finally, we showed that very low doses of CXCL11 rapidly suppress signs of EAE in C57BL/6 mice lacking functional CXCL11.

Update on the use of abatacept for the treatment of rheumatoid arthritis

Abatacept is approved for the treatment of moderate-to-severe active rheumatoid arthritis (RA) patients with inadequate response to one or more disease-modifying antirheumatic drugs (DMARDs), including methotrexate or a TNF antagonist, and can be used either as monotherapy or concomitantly with nonbiologic DMARDs. It can be administered either intravenously or subcutaneously. It has demonstrated to improve signs and symptoms of RA, physical function and health-related quality of life, and it inhibits radiographic progression of structural damage across a wide range of early and long-standing RA populations. The safety profile appears good and close to RA patients treated with nonbiologic DMARDs. Meta-analysis and real-world studies support these findings. This article reviews published data on clinical and radiographic efficacy as well as the safety of this drug, incorporating recent relevant information reported at scientific meetings.

Emerging biological therapies for systemic lupus erythematosus

INTRODUCTION

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with unpredictable disease course, intermingled with periods of remission and exacerbation. Current therapies for SLE are not ideal in terms of efficacy and toxicity. Although the prognosis of the disease has improved in the past decades, further improvement is hindered by the occurrence of organ damage as a result of persistent disease activity and treatment-related complications. Novel biological therapies targeting at higher treatment efficacy and fewer adverse effects are being developed.

AREAS COVERED

This review summarizes recent data on novel biological therapies for SLE. The pitfalls of clinical trial design and future directions of the development of SLE therapeutics are discussed.

EXPERT OPINION

The variable therapeutic response observed in SLE reflects the clinical and immunological heterogeneity of the disease. The treatment plan of SLE patients should be individualized, with the target of quenching out disease activity, minimizing disease flares, and treatment related morbidities. Despite the disappointment of recent clinical trials, avenues are being opened for novel agents that intervene at different levels of the pathophysiological cascade of SLE. With the availability of a new treatment armamentarium, it is hoped that the survival rate and quality of life of SLE patients can continue to improve.

Autoimmune pancreatitis in MRL/Mp mice is a T cell-mediated disease responsive to cyclosporine A and rapamycin treatment

BACKGROUND

Autoimmune pancreatitis (AIP) in humans invariably responds to steroid treatment, but little is known about the underlying pathogenesis and the benefits of alternative treatments.

OBJECTIVE

To study the pathogenesis, and the efficacy of alternative immunosuppressant agents in the MRL/Mp mouse model of AIP.

DESIGN

MRL/Mp mice were pretreated for 4 weeks with polyinosinic:polycytidylic acid to induce AIP. Pancreatic sections of mice genetically deleted for CTLA-4 were analysed. Blockage of CTLA-4 was achieved by intraperitoneal antibody treatment with 2 μg/g anti-mouse-CD152. Subsequent therapeutic studies were performed for a period of 4 weeks using cyclosporine A (40 μg/g), rapamycin (1 μg/g) or azathioprine (15 μg/g).

RESULTS

Blockage of CTLA-4 in MRL/Mp mice suppressed regulatory T cell (Treg) function and raised the effector T cell (Teff) response with subsequent histomorphological organ destruction, indicating that AIP is a T cell-driven disease. Using an established histopathological score, we found that dexamethasone, cyclosporine A and rapamycin, but less so azathioprine, reduced pancreatic damage. However, the beneficial effects of cyclosporine A and rapamycin were achieved via different mechanisms: cyclosporine A inhibited Teff activation and proliferation whereas rapamycin led to selective expansion of Tregs which subsequently suppressed the Teff response.

CONCLUSIONS

The calcineurin inhibitor cyclosporine A and the mammalian target of rapamycin (mTOR) inhibitor, rapamycin, improve the course of AIP in MRL/Mp mice via different mechanisms. These findings further support the concept of autoreactive T cells as key players in the pathogenesis of AIP and suggest that cyclosporine A and rapamycin should be considered for treatment of AIP in humans.

Biologics in SLE: towards new approaches

In recent years the use of biologic therapies in the management of systemic lupus erythematosus (SLE) has increased, and a number of clinical trials have highlighted both the potential and the pitfalls in the development of such agents. Many investigators reported that the off-label use of rituximab seemed promising in patients with refractory disease, but randomised trials with this agent failed. Likewise, the theoretical appeal of the co-stimulation blocker abatacept could not be confirmed in two clinical trials. Various considerations and post hoc analyses nonetheless suggest that these two biologics might have a role in the treatment of SLE. The anti-B-lymphocyte stimulator (anti-Blys) antibody belimumab demonstrated efficacy and safety in two large randomised trials and became the first approved biologic for lupus. Use in clinical practice has increased slowly, in part, due to uncertainty over which patients should be treated with this agent and in what stage of the disease. Finally, several other biologic agents are currently in advanced stages of clinical development for SLE. The overall picture that emerges is one of optimism that advances in SLE therapy will be realised through the targeted use of an increasing number of biologics.

Targeting co-stimulatory pathways: transplantation and autoimmunity

The myriad of co-stimulatory signals expressed, or induced, upon T-cell activation suggests that these signalling pathways shape the character and magnitude of the resulting autoreactive or alloreactive T-cell responses during autoimmunity or transplantation, respectively. Reducing pathological T-cell responses by targeting T-cell co-stimulatory pathways has met with therapeutic success in many instances, but challenges remain. In this Review, we discuss the T-cell co-stimulatory molecules that are known to have critical roles during T-cell activation, expansion, and differentiation. We also outline the functional importance of T-cell co-stimulatory molecules in transplantation, tolerance and autoimmunity, and we describe how therapeutic blockade of these pathways might be harnessed to manipulate the immune response to prevent or attenuate pathological immune responses. Ultimately, understanding the interplay between individual co-stimulatory and co-inhibitory pathways engaged during T-cell activation and differentiation will lead to rational and targeted therapeutic interventions to manipulate T-cell responses and improve clinical outcomes.

Immune checkpoint receptors in regulating immune reactivity in rheumatic disease

Immune checkpoint regulators are critical modulators of the immune system, allowing the initiation of a productive immune response and preventing the onset of autoimmunity. Co-inhibitory and co-stimulatory immune checkpoint receptors are required for full T-cell activation and effector functions such as the production of cytokines. In autoimmune rheumatic diseases, impaired tolerance leads to the development of diseases such as rheumatoid arthritis, systemic lupus erythematosus, and Sjogren's syndrome. Targeting the pathways of the inhibitory immune checkpoint molecules CD152 (cytotoxic T lymphocyte antigen-4) and CD279 (programmed death-1) in cancer shows robust anti-tumor responses and tumor regression. This observation suggests that, in autoimmune diseases, the converse strategy of engaging these molecules may alleviate inflammation owing to the success of abatacept (CD152-Ig) in rheumatoid arthritis patients. We review the preclinical and clinical developments in targeting immune checkpoint regulators in rheumatic disease.

CD86 is an activation receptor for NK cell cytotoxicity against tumor cells

CTLA4Ig has been successfully used in the clinic for suppression of T cell activation. However, patients treated with CTLA4Ig experienced reduced incidence of tumors than predicted, but the underlying mechanism remains unknown. In this paper, we showed that brief administration of CTLA4Ig significantly reduced tumor metastasis and prolonged the survival of host mice bearing B16 melanoma. Depletion of NK cells prior to CTLA4Ig administration eliminated the CTLA4Ig-mediated anti-tumor activity. CTLA4Ig enhanced NK cell cytotoxicity to tumor cells via up-regulation of NK cell effecter molecules CD107a and perforin in vivo. In addition, we demonstrated that, upon activation, NK cells could significantly increase the expression of CD86 both in vitro and in vivo, and ligation of CD86 with CTLA4Ig significantly increased the ability of NK cells to kill tumor cells. Furthermore, a human NK cell line that expressed high level of CD86 was directly activated by CTLA4Ig so that killing of tumor targets was enhanced; this enhanced killing could be inhibited by blocking CD86. Our findings uncover a novel function of CTLA4Ig in tumor immunity and suggest that CD86 on NK cells is an activating receptor and closely involved in the CTLA4Ig-mediated anti-tumor response.

B7 family checkpoint regulators in immune regulation and disease

Fine-tuning the immune response and maintaining tolerance to self-antigens involves a complex network of co-stimulatory and co-inhibitory molecules. The recent FDA approval of ipilimumab, a monoclonal antibody blocking cytotoxic T lymphocyte antigen (CTLA)-4, demonstrates the impact of checkpoint regulators in disease. This is reinforced by ongoing clinical trials targeting not only CTLA-4, but also the programmed death (PD)-1 and B7-H4 pathways in various disease states. Recently, two new B7 family inhibitory ligands, V-domain Ig suppressor of T cell activation (VISTA) and B7-H6 were identified. Here, we review recent understanding of B7 family members and their concerted regulation of the immune response to either self or foreign pathogens. We also discuss clinical developments in targeting these pathways in different disease settings, and introduce VISTA as a putative therapeutic target.

IFNα Inducible Models of Murine SLE

The role of type I interferons (IFNs) in SLE pathogenesis has been a subject of intense investigation in the last decade. The strong link between type I IFNs and SLE was initially provided by ex vivo studies showing that exposure of peripheral blood mononuclear cells to immune complexes from SLE patients elicits a signature of IFN inducible genes and was then further highlighted by human genetic studies. The mechanisms by which type I IFNs, especially IFN alpha (IFNα), modulate the immune system and exacerbate SLE have been largely elucidated through studies in mouse lupus models. In this review, we discuss the characteristics of several such models in which disease is accelerated by ectopically expressed IFNα. We also summarize several studies which tested therapeutic interventions in these models and discuss the advantages and disadvantages of using IFNα accelerated models to study experimental treatments for lupus.

Future prospects in biologic therapy for systemic lupus erythematosus

With the approval by the FDA in 2011 of a biologic agent (namely belimumab) for the treatment of systemic lupus erythematosus (SLE), optimism abounds that additional biologic (and nonbiologic) agents will be similarly endorsed. Given the numerous immune-based abnormalities associated with SLE, the potential therapeutic targets for biologic agents and the candidate biologic approaches are also numerous. These approaches include: biologic agents that promote B-cell depletion, B-cell inactivation, or the generation of regulatory B cells; biologic agents that induce T-cell tolerance, block T-cell activation and differentiation, or alter T-cell trafficking; biologic agents that target the B-cell activating factor (BAFF) axis, type I interferons, IL-6 and its receptor, or TNF; and the adoptive transfer of ex vivo-generated regulatory T cells. Owing to the great heterogeneity inherent to SLE, no single approach should be expected to be effective in all patients. As our understanding of the pathogenic mechanisms of SLE continues to expand, additional therapeutic targets and approaches will undoubtedly be identified and should be fully exploited.

Lack of Impact of Cytotoxic T-Lymphocyte Antigen 4 Gene Exon 1 Polymorphism on Susceptibility to or Clinical Course of Egyptian Childhood Immune Thrombocytopenic Purpura

Dysfunctional T-lymphocyte immunity plays an important role in the pathophysiology of immune thrombocytopenic purpura (ITP). Cytotoxic T-lymphocyte antigen 4 ( CTLA-4)—a surface marker expressed on T regulatory cells and activated T lymphocytes—is a negative modulator of T-cell responses. Polymorphisms of the CTLA-4 may alter the level of antigen expression and hence may influence immune regulation. The study aimed to evaluate the possible contribution of CTLA-4 exon 1 49 A>G polymorphism to the pathogenesis of ITP and its relation to age of disease onset, clinical course, and response to therapy. Genotyping of CTLA-4 exon 1 49 A>G was performed in 100 pediatric patients with ITP and 259 healthy individuals by polymerase chain reaction–restricted fragment length polymorphism. No significant differences existed in genotype or allele distributions between patients and controls for the studied polymorphism. Comparable genotypes and allele frequencies were obtained between the 2 groups after their stratification by age of disease onset, clinical course, or response to therapy. In conclusion, CTLA-4 exon 1 49 A>G polymorphism is not associated with susceptibility to ITP in the Egyptian population; neither it affects the clinical picture of the disease.

Aberrant B-lymphocyte responses in lupus: inherent or induced and potential therapeutic targets

BACKGROUND

Lupus is a prototype autoimmune disease of unknown aetiology. The disease is complex; manifest diverse clinical symptoms and disease mechanisms. This complexity has provided many leads to explore: from disease mechanisms to approaches for therapy. B-lymphocytes play a central role in the pathogenesis of the disease. However, the cause of aberrant B-lymphocyte responses in patients and, indeed, its causal relationship with the disease remain unclear.

DESIGN

This article provides a synopsis of current knowledge of immunological abnormalities in lupus with an emphasis on abnormalities in the B-lymphocyte compartment.

RESULTS

There is evidence for abnormalities in most compartments of the immune system in animal models and patients with lupus including an ever expanding list of abnormalities within the B-lymphocyte compartment. In addition, recent genome-wide linkage analyses in large cohorts of patients have identified new sets of genetic association factors some with potential links with defective B-lymphocyte responses although their full pathophysiological effects remain to be determined. The accumulating knowledge may help in the identification and application of new targeted therapies for treating lupus disease.

CONCLUSIONS

Cellular, molecular and genetic studies have provided significant insights into potential causes of immunological defects associated with lupus. Most of this insight relate to defects in B- and T-lymphocyte tolerance, signalling and responses. For B-lymphocytes, there is evidence for altered regulation of inter and intracellular signalling pathways at multiple levels. Some of these abnormalities will be discussed within the context of potential implications for disease pathogenesis and targeted therapies.

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.

Aberrant B cell selection and activation in systemic lupus erythematosus

The detrimental role of B lymphocytes in systemic lupus erythematosus (SLE) is evident from the high levels of pathogenic antinuclear autoantibodies (ANAs) found in SLE patients. Affirming this causative role, additional antibody-independent roles of B cells in SLE were appreciated. In recent years, many defects in B cell selection and activation have been identified in murine lupus models and SLE patients that explain the increased emergence and persistence of autoreactive B cells and their lowered activation threshold. Therefore, clinical trials with B cell depletion regimens in SLE patients were initiated but disappointingly the efficacy of B cell depleting agents proved to be limited. Remarkably however, a major breakthrough in SLE therapy was accomplished by blocking B cell survival factors rather then eliminating B cells. This surprising finding indicates that although SLE is a B cell-driven disease, the amplifying crosstalk between B cells and other cells of the immune system likely evokes the observed tolerance breakdown in B cells. Moreover, this implies that intelligent interception of pro-inflammatory loops rather then selectively silencing B cells will be key to the development of new SLE therapies. In this review, we will not only highlight the intrinsic B cell defects that facilitate the persistence of autoreactive B cells and their activation, but in addition we will focus on B cell extrinsic signals derived from T cells and innate immune cells that lower the activation threshold for B cells.

Maintenance immunosuppression in renal transplantation

The need to maintain allograft recipients on immunosuppression is nearly universal. Immunosuppressive agents used in organ transplantation target one or more steps of the host alloimmune response, specifically processes related to CD4-positive T lymphocytes. Calcineurin-inhibitor based steroid-containing regimens have been the mainstay of maintenance immunosuppression over the last two decades. Newer agents have shown efficacy in this role in recent trials with comparable allograft and patient outcomes. These agents have permitted calcineurin-inhibitor minimization and steroid-sparing strategies in selected groups of patients.

Novel therapeutic agents in clinical development for systemic lupus erythematosus

Conventional immunosuppressive therapies have radically transformed patient survival in systemic lupus erythematosus (SLE), but their use is associated with considerable toxicity and a substantial proportion of patients remain refractory to treatment. A more comprehensive understanding of the complexity of SLE immunopathogenesis has evolved over the past decade and has led to the testing of several biologic agents in clinical trials. There is a clear need for new therapeutic agents that overcome these issues, and biologic agents offer exciting prospects as future SLE therapies.An array of promising new therapies are currently emerging or are under development including B-cell depletion therapies, agents targeting B-cell survival factors, blockade of T-cell co-stimulation and anti-cytokine therapies, such as monoclonal antibodies against interleukin-6 and interferon-α.

Immune suppression in cynomolgus monkeys by XPro9523: an improved CTLA4-Ig fusion with enhanced binding to CD80, CD86 and neonatal Fc receptor FcRn

The CTLA4-Ig fusion proteins abatacept and belatacept are clinically proven immunosuppressants used for rheumatoid arthritis and renal transplant, respectively. Given that both biologics are typically administered chronically by infusion, a need exists for a next-generation CTLA4-Ig with more convenient dosing. We used structure-based protein engineering to optimize the affinity of existing CTLA4-Ig therapeutics for the ligands CD80 and CD86, and for the neonatal Fc receptor, FcRn. From a rationally designed library, we identified four substitutions that enhanced binding to human CD80 and CD86. Coupled with two IgG1 Fc substitutions that enhanced binding to human FcRn, these changes comprise the novel CTLA4-Ig fusion protein, XPro9523. Compared with abatacept, XPro9523 demonstrated 5.9-fold, 23-fold, and 12-fold increased binding to CD80, CD86, and FcRn, respectively; compared with belatacept, CD80, CD86, and FcRn binding increased 1.5-fold, 7.7-fold, and 11-fold, respectively. XPro9523 and belatacept suppressed human T cell proliferation and IL-2 production more potently than abatacept. XPro9523 also suppressed inflammation in the mouse collagen-induced arthritis model. In cynomolgus monkeys, XPro9523 saturated CD80 and CD86 more effectively than abatacept and belatacept, potently inhibited IgM and IgG immunization responses, and demonstrated longer half-life. Pharmacokinetic modeling of its increased potency and persistence suggests that, in humans, XPro9523 may demonstrate superior efficacy and dosing convenience compared with abatacept and belatacept.