Treatment of murine lupus with CTLA4Ig

A better understanding of the role of the CTLA-CD80/86 axis in the treatment of autoimmune diseases

Autoimmune diseases are diseases in which the regulatory mechanisms of the immune response are disturbed. As a result, the body loses self-tolerance. Since one of the main regulatory mechanisms of the immune response is the CTLA4-CD80/86 axis, this hypothesis suggests that autoimmune diseases potentially share a similar molecular basis of pathogenesis. Hence, investigating the CTLA4-CD80/86 axis may be helpful in finding an appropriate treatment strategy. Therefore, this study aims to investigate the molecular basis of the CTLA4-CD80/86 axis in the regulation of the immune response, and then its role in developing some autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, type 1 diabetes, and multiple sclerosis. As well, the main therapeutic strategies affecting the CTLA4-CD80/86 axis have been summarized to highlight the importance of this axis in management of autoimmune diseases.

Cytotoxic T-lymphocyte associated protein 4 (CTLA4) polymorphisms are linked to systemic lupus erythematosus: an updated meta-analysis

Cytotoxic T-lymphocyte associated protein 4 (CTLA-4) molecule controls T cell immune response. Functional single nucleotide polymorphisms (SNPs) in the CTLA-4 gene have been associated with several autoimmune diseases, including systemic lupus erythematosus (SLE).  However, the genetic association of the CTLA-4 variants with vulnerability to SLE remained contradictory. We have conducted a current meta-analysis by combining the findings of prior published articles in order to make a conclusive statement. Various literature databases were screened with appropriate keywords to obtain relevant articles, and eligible reports were obtained using well-defined inclusion and exclusion criteria. Meta-analysis was performed by Comprehensive Meta-analysis V 3.3, and various statistical parameters such as odds ratio, 95% confidence interval, and probability values were computed. A total of 3847 SLE patients and 5278 healthy controls were considered in the present meta-analysis from 26 individual reports. A significant association of CTLA-4 +49 A/G (G vs. A: p=0.03, OR=1.47) and -1722 T/C (p=0.02, OR=0.87) polymorphisms were observed with susceptibility and resistance against the development of SLE, respectively. However, the other two SNPs in the CTLA-4 gene (-318 C/T and -1661 A/G) failed to establish a connection. Interestingly, subgroup analysis revealed an association of CTLA-4 +49 A/G with a predisposition to SLE only in the Asian population (G vs. A: p=0.04, OR=1.26, GG vs. AA: p=0.02, OR=1.84, AG vs AA: p=0.01, OR=1.44, GG+AG vs AA: p=0.01, OR=1.52) and not in Caucasians. The current meta-analysis suggests a significant CTLA-4 +49 A/G variant association with susceptibility to SLE development in overall and Asian populations. In contrast, the other variant, -1722 T/C, is linked with protection against SLE. However, further case-control studies in diverse ethnic populations are requisite.

Not Dead Yet

I have been a scientific grasshopper throughout my career, moving from question to question within the domain of lupus. This has proven to be immensely gratifying. Scientific exploration is endlessly fascinating, and succeeding in studies you care about with colleagues and trainees leads to strong and lasting bonds. Science isn't easy; being a woman in science presents challenges, but the drive to understand a disease remains strong.

Molecular Mechanisms in Autoimmune Thyroid Disease

The most common cause of acquired thyroid dysfunction is autoimmune thyroid disease, which is an organ-specific autoimmune disease with two presentation phenotypes: hyperthyroidism (Graves-Basedow disease) and hypothyroidism (Hashimoto's thyroiditis). Hashimoto's thyroiditis is distinguished by the presence of autoantibodies against thyroid peroxidase and thyroglobulin. Meanwhile, autoantibodies against the TSH receptor have been found in Graves-Basedow disease. Numerous susceptibility genes, as well as epigenetic and environmental factors, contribute to the pathogenesis of both diseases. This review summarizes the most common genetic, epigenetic, and environmental mechanisms involved in autoimmune thyroid disease.

Can Soluble Immune Checkpoint Molecules on Exosomes Mediate Inflammation?

Immune checkpoints (ICPs) are major co-signaling pathways that trigger effector functions in immune cells, with isoforms that are either membrane bound, engaging in direct cell to cell activation locally, or soluble, acting at distant sites by circulating freely or potentially via extracellular vesicles (EVs). Exosomes are small EVs secreted by a variety of cells carrying various proteins and nucleic acids. They are distributed extensively through biological fluids and have major impacts on infectious diseases, cancer, and neuroinflammation. Similarly, ICPs play key roles in a variety of disease conditions and have been extensively utilized as a prognostic tool for various cancers. Herein, we explored if the association between exosomes and ICPs could be a significant contributor of inflammation, particularly in the setting of cancer, neuroinflammation and viral infections, wherein the up regulation in both exosomal proteins and ICPs correlate with immunosuppressive effects. The detailed literature review of existing data highlights the significance and complexity of these two important pathways in mediating cancer and potentiating neuroinflammation via modulating overall immune response. Cells increasingly secret exosomes in response to intracellular signals from invading pathogens or cancerous transformations. These exosomes can carry a variety of cargo including proteins, nucleic acids, cytokines, and receptors/ligands that have functional consequences on recipient cells. Illustration generated using BioRender software.

PDZ Proteins SCRIB and DLG1 Regulate Myeloma Cell Surface CD86 Expression, Growth, and Survival

Despite advances in the treatment of multiple myeloma in the past decades, the disease remains incurable, and understanding signals and molecules that can control myeloma growth and survival are important for the development of novel therapeutic strategies. One such molecule, CD86, regulates multiple myeloma cell survival via its interaction with CD28 and signaling through its cytoplasmic tail. Although the CD86 cytoplasmic tail has been shown to be involved in drug resistance and can induce molecular changes in multiple myeloma cells, its function has been largely unexplored. Here, we show that CD86 cytoplasmic tail has a role in trafficking CD86 to the cell surface. This is due in part to a PDZ-binding motif at its C-terminus which is important for proper trafficking from the Golgi apparatus. BioID analysis revealed 10 PDZ domain-containing proteins proximal to CD86 cytoplasmic tail in myeloma cells. Among them, we found the planar cell polarity proteins, SCRIB and DLG1, are important for proper CD86 surface expression and the growth and survival of myeloma cells. These findings indicate a mechanism by which myeloma cells confer cellular survival and drug resistance and indicate a possible motif to target for therapeutic gain.

IMPLICATIONS

These findings demonstrate the importance of proper trafficking of CD86 to the cell surface in myeloma cell survival and may provide a new therapeutic target in this disease.

Blockage of TIM-3 relieves lupus nephritis by expanding Treg cells and promoting their suppressive capacity in MRL/lpr mice

T Cell Immunoglobulin and Mucin Containing Protein-3 (TIM-3) is an important immune checkpoint protein that is expressed in Tregs and affects their function. However, the expression and role of TIM-3 in modulating regulatory T cells (Tregs) in lupus nephritis (LN) are still unknown. In this study, we found that the percentage of TIM-3⁺ cells among spleen lymphocytes, CD4⁺ T cells and Tregs was higher in MRL/lpr mice than in MpJ mice. TIM-3^high CD4⁺ T cells and TIM-3^high Tregs were mainly responsible for the increase. The percentage of Tregs in TIM-3^high CD4⁺ T cells was lower than that in TIM-3^low CD4⁺ T cells, and the expression of CTLA-4 and IL-10 was lower in TIM-3^high Tregs than in the TIM-3^low Tregs in MRL/lpr mice. Blockade of TIM-3 in vivo significantly increased the Treg population and the expression of CTLA-4 and IL-10 in Tregs, thus relieving the LN symptoms and pathology in MRL/lpr mice. Additionally, bioinformatics analysis indicated that TIM-3 regulates Treg cells in LN mainly through cytokine-cytokine receptor interactions, the PI3K-Akt signaling pathway, the T cell receptor signaling pathway, Th17 cell differentiation and the FoxO signaling pathway. Together, our study has demonstrated that TIM-3 regulates Tregs in LN and that overexpression of TIM-3 in CD4⁺ T cells and Tregs leads to Treg quantity and quality deficiency in MRL/lpr mice. Blockade of TIM-3 protects against LN by expanding Tregs and enhancing their suppressive capacity. Finally, TIM-3 might be a potential therapeutic target for the treatment of LN.

Treatment of experimental autoimmune encephalomyelitis using AAV gene therapy by blocking T cell costimulatory pathways

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS), characterized by inflammation and demyelination. Presently, repeated relapses of MS necessitate long-term immune-regulatory therapy. Blocking the CD28-B7 and CD40-CD40L costimulatory pathways is an effective and synergistic method for the prevention and amelioration of clinical symptoms of experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. In this study, to explore the efficacy and safety of MS gene therapy, we used adeno-associated virus (AAV) as a vector to deliver CTLA4-immunoglobulin (Ig) or CD40-Ig on the EAE induced by myelin oligodendrocyte glycoprotein (MOG). Our results showed that a single administration of AAV8-CTLA4-Ig, either alone or with AAV8-CD40-Ig, protected mice from EAE and reversed disease progression. Decreased CD4⁺ and CD8⁺ T cell infiltration, inhibition of MOG antibody response, and downregulation of neuroinflammation were observed in mice receiving AAV, suggesting that autoimmunity was suppressed in EAE pathology. Moreover, no hematological or hepatic toxicity was observed in AAV-treated mice. Thus, compared with treatment with recombinant CTLA4-Ig (belatacept), AAV gene therapy could effectively control clinical symptoms and suppress autoimmunity in the long term. In summary, our study provides a potential therapeutic method for blocking T cell costimulation for the treatment of MS via gene therapy.

Survey of the association between polymorphisms of CTLA-4 exon 1 49 A/G genes with rheumatoid arthritis in Iran

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), which suppresses T cell proliferation, is a promising candidate for the susceptibility genes to rheumatic arthritis diseases (RA). This study aims to examine the association between the polymorphisms of the CTLA-4 exon 1(+ 49) genes with RA in the Qazvin city of Iran population. The polymerase chain reaction of genomic DNA-restriction fragment length polymorphism (PCR-RFLP) was applied to genotype the CTLA-4 exon 1(+ 49) polymorphisms in 105 RA patients and 90 control subjects. Laboratory diagnostic tests were also measured for RA and control groups. Our results did not demonstrate a significant difference in allele and genotype frequencies of the CTLA-4 exon 1(+ 49) between RA patients and the control group (p < .0001). There was no significant difference in age at onset, CRP, RF value in patients with RA according to the CTLA-4 polymorphisms; just anti-CCP showed a significant difference. Our data declared that polymorphisms of CTLA-4 exon 1(+ 49) genes are not correlated with RA susceptibility and its clinical and paraclinical manifestations.

Advances in Drug Therapy for Systemic Lupus Erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by a local or systemic inflammatory response. At present, the increasing research results show that the pathogenesis of the disease is complex, and the methods of clinical treatment also show diversity. This review analyzes and summarizes the existing mechanism research and drug treatment methods in order to provide a reference value for further drug research and development.

METHOD

We carried out a thorough literature search using databases. According to the main purpose of the article, irrelevant articles were excluded after further examination and directly relevant articles were included. Finally, the information related to the article was summarized.

RESULT

In this article, seventy-four articles are included. According to related articles, there are mainly four kinds of drugs, namely antimalarial drugs, glucocorticoids, immunosuppressive agents and biological agents. About fifty-five articles summarized the drugs for the treatment of systemic lupus erythematosus. The rest of the articles were related to the research progress of the mechanism of systemic lupus erythematosus.

CONCLUSION

This article describes the pathogenesis of systemic lupus erythematosus, and summarizes the traditional and new therapeutic drugs, which is not only beneficial to the treatment of lupus erythematosus patients, but also plays a vital reference significance for the future development of new systemic lupus erythematosus drugs.

Co-inhibitory Receptor Signaling in T-Cell-Mediated Autoimmune Glomerulonephritis

Autoimmune glomerulonephritis occurs as a consequence of autoantibodies and T-cell effector functions that target autoantigens. Co-signaling through cell surface receptors profoundly influences the optimal activation of T cells. The scope of this review is signaling mechanisms and the functional roles of representative T-cell co-inhibitory receptors in the regulation of autoimmune glomerulonephritis, along with current therapeutic challenges mainly on preclinical trials. Co-inhibitory receptors utilize both shared and unique signaling pathway, suggesting specialized functions that provide the rationale behind therapies for autoimmune glomerulonephritis by targeting these inhibitory receptors. These receptors largely suppress Th1 immunity, modify Th17 and Th2 immune response, and enhance Treg function. Anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA4) immunoglobulin (Ig), which is able to block both activating CD28 and inhibitory CTLA4 signaling, has been shown in preclinical and clinical investigations to have effects on glomerular disease. Other inhibitory receptors for treating glomerulonephritis have not been clinically tested, and efficacy of manipulating these pathways requires further preclinical investigation. While immune checkpoint inhibition using anti-CTLA4 antibodies and anti-programmed cell death 1 (PD-1)/PD-L1 antibodies has been approved for the treatment of several cancers, blockade of CTLA4 and PD-1/PD-L1 is associated with adverse effects that resemble autoimmune disorders, including systemic vasculitis. A renal autoimmune vasculitis model features an initial Th17 dominancy followed later by a Th1-dominant outcome and Treg cells that attenuate autoreactive T-cell function. Toward the development of effective therapies for T-cell-mediated autoimmune glomerulonephritis, it would be preferable to pay attention to the impact of the inhibitory pathways in immunological renal disease settings.

Systemic lupus erythematosus (SLE): emerging therapeutic targets

INTRODUCTION

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a heterogeneous clinical presentation whose etiologies are multifactorial. A myriad of genetic, hormonal, immunologic, and environmental factors contribute to its pathogenesis, and its diverse biological basis and phenotypic presentations make development of therapeutics difficult. In the past decade, tens of therapeutic targets with hundreds of individual candidate therapeutics have been investigated.

AREAS COVERED

We used a PUBMED database search through April 2020 to review the relevant literature. This review discusses therapeutic targets in the adaptive and innate immune systems, specifically: B cell surface antigens, B cell survival factors, Bruton's tyrosine kinase, costimulators, IL-12/IL-23, the calcineurin pathway, the JAK/STAT pathway, and interferons.

EXPERT OPINION

Our ever-improving understanding of SLE pathophysiology in the past decade has allowed us to identify new therapeutic targets. Multiple new drugs are on the horizon that target different elements of the adaptive and innate immune systems. SLE research remains challenging due to the heterogenous clinical presentation of SLE, confounding from background immunosuppressives being taken by SLE patients, animal models that inadequately recapitulate human disease, and imperfect and complicated outcome measures. Despite these limitations, research is promising and ongoing. The search for new therapies that target specific elements of SLE pathophysiology are discussed as well as key findings, pitfalls, and questions surrounding these targets.

Leveraging Heterogeneity in Systemic Lupus Erythematosus for New Therapies

Systemic lupus erythematosus (SLE) is a multisystem, chronic autoimmune disease where treatment varies by patient and disease activity. Strong preclinical results and clinical correlates have motivated development of many drugs, but many of these have failed to achieve efficacy in clinical trials. FDA approval of belimumab in 2011 was the first successful SLE drug in nearly six decades. In this article, we review insights into the molecular and clinical heterogeneity of SLE from transcriptomics studies and detail their potential impact on drug development and clinical practices. We critically examine the pipeline of SLE drugs, including past failures and their associated lessons and current promising approaches. Finally, we identify opportunities for integrating these findings and drug development with new multidisciplinary advances to enhance future SLE treatment.

A novel monoclonal antibody against human B7-1 protects against chronic graft-vs.-host disease in a murine lupus nephritis model

Lupus nephritis (LN) is the most common complication that causes mortality in patients with systemic lupus erythematosus. The B7-1/B7-2 and CD28/cytotoxic T-lymphocyte associated protein 4 co-stimulatory pathway serves a key role in autoimmune disease and organ transplantation. The aim of the present study was to generate and characterize a monoclonal antibody (mAb; clone 4E5) against human B7-1 and to investigate its potential use for the treatment of LN. The results demonstrated that the 4E5 mAb was successfully generated and able to recognize both human and mouse B7-1. After injection of this mAb into a mouse model with chronic graft-vs.-host disease (cGVHD)-induced lupus-like disease, the expression of CD21, CD23, CD80 and CD86 on B220⁺ B-cells in the spleen, and the concentrations of serum autoantibodies and urine protein, were decreased. Direct immunofluorescence analysis of the kidneys revealed that immunofluorescence of immune complex deposits was weaker in the 4E5-treated mice and electron microscopy analyses of renal tissues indicated that pathological injury of the kidneys of 4E5-treated mice was decreased compared with that in the model control mice. The results of the present study demonstrated that inhibition of the B7-1/CD28 co-stimulatory signaling pathway with the 4E5 mAb may represent a promising strategy to decelerate the progression of LN that is induced by cGVHD with potential for use in the treatment of other autoimmune diseases.

Are lupus animal models useful for understanding and developing new therapies for human SLE?

Systemic lupus erythematosus is a systemic autoimmune disease driven by a complex combination of genetic, environmental, and other immunoregulatory factors. The development of targeted therapies is complicated by heterogeneous clinical manifestations, varying organ involvement, and toxicity. Despite advances in understanding the mechanisms contributing to SLE, only one biologic drug, belimumab, is FDA-approved. The identification and development of potential therapies have largely been driven by studies in lupus animal models. Therefore, direct comparison of both the therapeutic and immunological findings in human and murine SLE studies is critical and can reveal important insights into indeed how useful and relevant are murine studies in SLE drug development. Studies involving belimumab, mycophenolate mofetil, abatacept, rituximab, and anti-interferon strategies generally demonstrated analogous findings in the attenuation of SLE manifestations and modulation of select immune cell populations in human and murine SLE. While further basic and translational studies are needed to identify SLE patient subsets likely to respond to particular therapeutic modalities and in dissecting complex mechanisms, we believe that despite some inherent weaknesses SLE mouse models will continue to be integral in developing targeted SLE therapies.

The Role of Immune Checkpoint Receptors in Regulating Immune Reactivity in Lupus

Immune checkpoint receptors with co-stimulatory and co-inhibitory signals are important modulators for the immune system. However, unrestricted co-stimulation and/or inadequate co-inhibition may cause breakdown of self-tolerance, leading to autoimmunity. Systemic lupus erythematosus (SLE) is a complex multi-organ disease with skewed and dysregulated immune responses interacting with genetics and the environment. The close connections between co-signaling pathways and SLE have gradually been established in past research. Also, the recent success of immune checkpoint blockade in cancer therapy illustrates the importance of the co-inhibitory receptors in cancer immunotherapy. Moreover, immune checkpoint blockade could result in substantial immune-related adverse events that mimic autoimmune diseases, including lupus. Together, immune checkpoint regulators represent viable immunotherapeutic targets for the treatment of both autoimmunity and cancer. Therefore, it appears reasonable to treat SLE by restoring the out-of-order co-signaling axis or by manipulating collateral pathways to control the pathogenic immune responses. Here, we review the current state of knowledge regarding the relationships between SLE and the co-signaling pathways of T cells, B cells, dendritic cells, and neutrophils, and highlight their potential clinical implications. Current clinical trials targeting the specific co-signaling axes involved in SLE help to advance such knowledge, but further in-depth exploration is still warranted.

Moving Forward With Biologics in Lupus Nephritis

The majority of patients with systemic lupus erythematosus develop lupus nephritis (LN) which significantly contributes to increased risks of hospitalizations, ESRD, and death. Unfortunately, treatments for LN have not changed over the past 15 years. Despite continued efforts to elucidate the pathogenesis of LN, no new drugs have yet replaced the standard-of-care regimens of cyclophosphamide or mycophenolate mofetil plus high-dose corticosteroids. The significant limitations of standard-of-care are low complete response rates, risk of flares, and ongoing inflammation in the kidney leading to progressive renal dysfunction. Repeat and prolonged treatments are often needed to control disease, leading to a high level of severe side effects. The development of targeted drugs with better efficacy and safety are desperately needed. The rationale for targeting key immunologic pathways in LN continues to be strongly supported by basic and translational research and has generated the hope and excitement of testing these therapies in human LN. This review provides an overview of biologics studied to date in clinical trials of LN, discusses the potential reasons for their failure, and addresses the challenges moving forward.

Biologics in the Treatment of Lupus Erythematosus: A Critical Literature Review

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease affecting multiple organ systems that runs an unpredictable course and may present with a wide variety of clinical manifestations. Advances in treatment over the last decades, such as use of corticosteroids and conventional immunosuppressive drugs, have improved life expectancy of SLE sufferers. Unfortunately, in many cases effective management of SLE is still related to severe drug-induced toxicity and contributes to organ function deterioration and infective complications, particularly among patients with refractory disease and/or lupus nephritis. Consequently, there is an unmet need for drugs with a better efficacy and safety profile. A range of different biologic agents have been proposed and subjected to clinical trials, particularly dedicated to this subset of patients whose disease is inadequately controlled by conventional treatment regimes. Unfortunately, most of these trials have given unsatisfactory results, with belimumab being the only targeted therapy approved for the treatment of SLE so far. Despite these pitfalls, several novel biologic agents targeting B cells, T cells, or cytokines are constantly being evaluated in clinical trials. It seems that they may enhance the therapeutic efficacy when combined with standard therapies. These efforts raise the hope that novel drugs for patients with refractory SLE may be available in the near future. This article reviews the current biological therapies being tested in the treatment of SLE.

Immune inhibitory proteins and their pathogenic and therapeutic implications in autoimmunity and autoimmune hepatitis

Key inhibitory proteins can blunt immune responses to self-antigens, and deficiencies in this repertoire may promote autoimmunity. The goals of this review are to describe the key immune inhibitory proteins, indicate their possible impact on the development of autoimmune disease, especially autoimmune hepatitis, and encourage studies to clarify their pathogenic role and candidacy as therapeutic targets. English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed. Cytotoxic T lymphocyte antigen-4 impairs ligation of CD28 to B7 ligands on antigen presenting cells and inhibits the adaptive immune response by increasing anti-inflammatory cytokines, generating regulatory T cells, and reducing T cell activation and proliferation. Programed cell death antigen-1 inhibits T cell selection, activation, and proliferation by binding with two ligands at different phases and locations of the immune response. A soluble alternatively spliced variant of this protein can dampen the inhibitory signal. Autoimmune hepatitis has been associated with polymorphisms of the cytotoxic T lymphocyte antigen-4 gene, reduced hepatic expression of a ligand of programed cell death antigen-1, an interfering soluble variant of this key inhibitory protein, and antibodies against it. Findings have been associated with laboratory indices of liver injury and suboptimal treatment response. Abatacept, belatacept, CD28 blockade, and induction of T cell exhaustion are management considerations that require scrutiny. In conclusion, deficiencies in key immune inhibitory proteins may promote the occurrence of autoimmune diseases, such as autoimmune hepatitis, and emerging interventions may overcome these deficiencies. Investigations should define the nature, impact and management of these inhibitory disturbances in autoimmune hepatitis.

Dendritic cells, T cells and their interaction in rheumatoid arthritis

Dendritic cells (DCs) are the key professional antigen-presenting cells which bridge innate and adaptive immune responses, inducing the priming and differentiation of naive to effector CD4+ T cells, the cross-priming of CD8+ T cells and the promotion of B cell antibody responses. DCs also play a critical role in the maintenance of immune homeostasis and tolerance. DC-T cell interactions underpin the generation of an autoimmune response in rheumatoid arthritis (RA). Here we describe the function of DCs and review evidence for DC and T cell involvement in RA pathogenesis, in particular through the presentation of self-peptide by DCs that triggers differentiation and activation of autoreactive T cells. Finally, we discuss the emerging field of targeting the DC-T cell interaction for antigen-specific immunotherapy of RA.

Achievement of Tolerance Induction to Prevent Acute Graft-vs.-Host Disease

Acute graft-vs.-host disease (GVHD) limits the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT), a main therapy to treat various hematological disorders. Despite rapid progress in understanding GVHD pathogenesis, broad immunosuppressive agents are most often used to prevent and remain the first line of therapy to treat GVHD. Strategies enhancing immune tolerance in allo-HSCT would permit reductions in immunosuppressant use and their associated undesirable side effects. In this review, we discuss the mechanisms responsible for GVHD and advancement in strategies to achieve immune balance and tolerance thereby avoiding GVHD and its complications.

Abatacept for the treatment of rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a complex disease in which different mechanisms are involved. Studies suggest a key role for aberrant pathways of T-cell activation in the initiation and perpetuation of disease. Abatacept is a fusion protein composed of the Fc region of the immunoglobulin G1 (IgG1) fused to the extracellular domain of cytotoxic T lymphocyte-associated antigen (CTLA4). It has the ability to modulate T-cell activation by interfering with co-stimulation of these cells, a necessary step to become activated. This suggests that abatacept may play a role in the progression and/or even the initiation of RA. Areas covered: a review of the different studies carried out during clinical development of abatacept was performed. Both formulations, intravenous (IV) and subcutaneous (SC), showed a similar and consistent efficacy and safety profile. Abatacept was effective both in RA patients not responding to methotrexate (MTX) and to tumor necrosis factor (TNF) inhibitors. Expert commentary: abatacept, with its unique mechanism of action, proved to be a useful therapeutic alternative in RA, also having an acceptable safety profile. Evidence points out that abatacept may be able to alter the RA disease course. Ongoing studies will clarify this issue.

Costimulatory blockade molecules and B-cell-mediated immune response: current knowledge and perspectives

There is an urgent need for therapeutic agents that target humoral alloimmunity in solid organ transplantation. This includes sensitized patients with preformed donor-specific human leukocyte antigen antibodies and patients who develop de novo donor-specific antibodies, both of which are associated with acute and chronic antibody-mediated rejection and allograft loss. In the last decade, both experimental and clinical studies highlighted the major impact of costimulation molecules in the control of immune responses both in the field of transplantation and autoimmune disease. Although these molecules have been initially developed to control the early steps of T-cell activation, recent evidence also supports their influence at several steps of the humoral response. In this review, we aim to provide an overview of the current knowledge of the effects of costimulatory blockade agents on humoral responses in both autoimmune and allogeneic contexts. We first present the effects of costimulatory molecules on the different steps of alloantibody production. We then summarize mechanisms and clinical results observed using cytotoxic T lymphocyte antigen-4 (CTLA4)-Ig molecules both in transplantation and autoimmunity. Finally, we present the potential interest and implications of other costimulatory family members as therapeutic targets, with emphasis on combinatorial approaches, for the optimal control of the alloantigen-specific humoral response.

Complement serves as a switch between CD4+ T cell-independent and -dependent RBC antibody responses

RBC alloimmunization represents a significant immunological challenge for patients requiring lifelong transfusion support. The majority of clinically relevant non-ABO(H) blood group antigens have been thought to drive antibody formation through T cell-dependent immune pathways. Thus, we initially sought to define the role of CD4+ T cells in formation of alloantibodies to KEL, one of the leading causes of hemolytic transfusion reactions. Unexpectedly, our findings demonstrated that KEL RBCs actually possess the ability to induce antibody formation independent of CD4+ T cells or complement component 3 (C3), two common regulators of antibody formation. However, despite the ability of KEL RBCs to induce anti-KEL antibodies in the absence of complement, removal of C3 or complement receptors 1 and 2 (CR1/2) rendered recipients completely reliant on CD4+ T cells for IgG anti-KEL antibody formation. Together, these findings suggest that C3 may serve as a novel molecular switch that regulates the type of immunological pathway engaged following RBC transfusion.

Visualising the interaction of CD4 T cells and DCs in the evolution of inflammatory arthritis

OBJECTIVES

Successful early intervention in rheumatoid arthritis (RA) with the aim of resetting immunological tolerance requires a clearer understanding of how specificity, cellular kinetics and spatial behaviour shape the evolution of articular T cell responses. We aimed to define initial seeding of articular CD4+ T cell responses in early experimental arthritis, evaluating their dynamic behaviour and interactions with dendritic cells (DCs) in the inflamed articular environment.

METHODS

Antigen-induced arthritis was used to model articular inflammation. Flow cytometry and PCR of T cell receptor (TCR) diversity genes allowed phenotypic analysis of infiltrating T cells. The dynamic interactions of T cells with joint residing DCs were visualised using intravital multiphoton microscopy.

RESULTS

Initial recruitment of antigen-specific T cells into the joint was paralleled by accumulation of CD4+ T cells with diverse antigen-receptor expression and ability to produce tumour necrosis factor alpha (TNFα) and interferon gamma (IFNγ) on mitogenic restimulation. A proportion of this infiltrate demonstrated slower motility speeds and engaged for longer periods with articular DCs in vivo. Abatacept treatment did not disrupt these interactions but did reduce T cell expression of inducible costimulatory (ICOS) molecule. We also demonstrated that non-specific CD4+ T cells could be recruited during these early articular events.

CONCLUSIONS

We demonstrate that CD4+ T cells engage with articular DCs supporting antigen specific T cell reactivation. This cellular dialogue can be targeted therapeutically to reduce local T cell activation.

Curcumin modulation of the activation of PYK2 in peripheral blood mononuclear cells from patients with lupus nephritis

INTRODUCTION

Proline-rich tyrosine kinase 2 (PYK2) provides important signals during the activation of lymphocytes, which is essential in autoimmune diseases. Systemic lupus erythematosus (SLE) is a representative autoimmune disease, and lupus nephritis (LN) is one of its most severe complications. Although glucocorticoid-binding immuno-suppression is the first-line therapy for patients with LN, the common and severe side effects of such treatment call for new strategies to improve long-term prognosis and life quality for these patients. Curcumin has been used to treat autoimmune disease with good curative effect, but little is known about the effect of curcumin on LN patients. Our aim was to investigate the mechanism of curcumin for management of LN, specifically regarding the PYK2 pathways.

MATERIAL AND METHODS

Freshly isolated peripheral blood mononuclear cells (PBMCs) from 20 LN patients and 20 healthy individuals were cultured and stimulated with either PMA, PMA+TyrA9 (PYK2 specific inhibitor), or PMA+Curcumin, and with PBS as control. After 48 hours of incubation, cells were harvested and the expression of PYK2, p-PYK2, CD40L, CTLA-4, and PBMCs proliferation were measured. Then the expression and activation of PYK2 was evaluated using Western blot, the expression of costimulatory molecules CD40L and CTLA-4 protein was evaluated using flow cytometry, and PBMC proliferation was assessed using a [3H]-thymidine incorporation assay.

RESULTS

Curcumin inhibited the expression and activation of PYK2 in PBMCs in patients with LN in vitro. The inhibition rate of curcumin was negatively correlated with the level of serum complement, but positively correlated with 24-h proteinuria. Curcumin also suppressed the expression of costimulatory molecules CD40L and CTLA-4, as well as PBMC proliferation. Interestingly, these effects were not reproduced on PBMC cultures of healthy subjects.

CONCLUSIONS

The inhibition of PYK2 signalling protein may be one of the mechanisms underlying the action of curcumin in LN treatment.

Bioconjugate Strategies for the Induction of Antigen-Specific Tolerance in Autoimmune Diseases

Antigen-specific immunotherapy (ASI) holds great promise for the treatment of autoimmune diseases. In mice, administration of major histocompatibility complex (MHC) binding synthetic peptides which modulate T cell receptor (TCR) signaling under subimmunogenic conditions induces selective tolerance without suppressing the global immune responses. However, clinical translation has yielded limited success. It has become apparent that the TCR signaling pathway via synthetic peptide antigen alone is inadequate to induce an effective tolerogenic immunity in autoimmune diseases. Bioconjugate strategies combining additional immunomodulatory functions with TCR signaling can amplify the antigen-specific immune tolerance and possibly lead to the development of new treatments in autoimmune diseases. In this review, we provide a summary of recent advances in the development of bioconjugates to achieve antigen-specific immune tolerance in vivo, with the discussion focused on the underlying design principles and challenges that must be overcome to target these therapies to patients suffering from autoimmune diseases.

Antagonist Anti-CD28 Therapeutics for the Treatment of Autoimmune Disorders

The effector functions of T lymphocytes are responsible for most autoimmune disorders and act by directly damaging tissues or by indirectly promoting inflammation and antibody responses. Co-stimulatory and co-inhibitory T cell receptor molecules are the primary pharmacological targets that enable interference with immune-mediated diseases. Among these, selective CD28 antagonists have drawn special interest, since they tip the co-stimulation/co-inhibition balance towards efficiently inhibiting effector T cells while promoting suppression by pre-existing regulatory T-cells. After having demonstrated outstanding therapeutic efficacy in multiple models of autoimmunity, inflammation and transplantation, and safety in phase-I studies in humans, selective CD28 antagonists are currently in early clinical development for the treatment of systemic lupus erythematous and rheumatoid arthritis. Here, we review the available proof of concept studies for CD28 antagonists in autoimmunity, with a special focus on the mechanisms of action.

CD86 regulates myeloma cell survival

Although prognosis for patients with multiple myeloma has improved over the past decade, research toward discovery of new therapeutic avenues is important and could lead to a cure for this plasma cell malignancy. Here we show that blocking the CD28-CD86 pathway via silencing of either CD28 or CD86 leads to myeloma cell death. Inhibiting this pathway leads to downregulation of integrins and IRF4, a known myeloma survival factor. Our data also indicate that CD86, the canonical ligand in this pathway, has prosurvival activity that is dependent on its cytosolic domain. These findings indicate that targeting of this pathway is a promising therapeutic avenue for myeloma, because it leads to modulation of different processes important in cell viability.

Co-stimulatory and Co-inhibitory Pathways in Autoimmunity

The immune system is guided by a series of checks and balances, a major component of which is a large array of co-stimulatory and co-inhibitory pathways that modulate the host response. Although co-stimulation is essential for boosting and shaping the initial response following signaling through the antigen receptor, inhibitory pathways are also critical for modulating the immune response. Excessive co-stimulation and/or insufficient co-inhibition can lead to a breakdown of self-tolerance and thus to autoimmunity. In this review, we will focus on the role of co-stimulatory and co-inhibitory pathways in two systemic (systemic lupus erythematosus and rheumatoid arthritis) and two organ-specific (multiple sclerosis and type 1 diabetes) emblematic autoimmune diseases. We will also discuss how mechanistic analysis of these pathways has led to the identification of potential therapeutic targets and initiation of clinical trials for autoimmune diseases, as well as outline some of the challenges that lie ahead.

Costimulation Blockade in Autoimmunity and Transplantation: The CD28 Pathway

T cell activation is a complex process that requires multiple cell signaling pathways, including a primary recognition signal and additional costimulatory signals. TCR signaling in the absence of costimulatory signals can lead to an abortive attempt at activation and subsequent anergy. One of the best-characterized costimulatory pathways includes the Ig superfamily members CD28 and CTLA-4 and their ligands CD80 and CD86. The development of the fusion protein CTLA-4-Ig as an experimental and subsequent therapeutic tool is one of the major success stories in modern immunology. Abatacept and belatacept are clinically approved agents for the treatment of rheumatoid arthritis and renal transplantation, respectively. Future interventions may include selective CD28 blockade to block the costimulatory potential of CD28 while exploiting the coinhibitory effects of CTLA-4.

Challenges and opportunities in targeting the CD28/CTLA-4 pathway in transplantation and autoimmunity

INTRODUCTION

T cell activation is a complex process that requires multiple cell signaling pathways, including a primary recognition signal and additional costimulatory signals. One of the best-characterized costimulatory pathways includes the Ig superfamily members CD28 and CTLA-4 and their ligands CD80 and CD86. Areas covered: This review discusses past, current and future biological therapies that have been utilized to block the CD28/CTLA-4 cosignaling pathway in the settings of autoimmunity and transplantation, as well the challenges facing successful implementation of these therapies. Expert opinion: The development of CD28 blockers Abatacept and Belatacept provided a more targeted therapy approach for transplant rejection and autoimmune disease relative to calcineurin inhibitors and anti-proliferatives, but overall efficacy may be limited due to their collateral effect of simultaneously blocking CTLA-4 coinhibitory signals. As such, current investigations into the potential of selective CD28 blockade to block the costimulatory potential of CD28 while exploiting the coinhibitory effects of CTLA-4 are promising. However, as selective CD28 blockade inhibits the activity of both effector and regulatory T cells, an important goal for the future is the design of therapies that will maximize the attenuation of effector responses while preserving the suppressive function of T regulatory cells.

T-cell-directed therapies in systemic lupus erythematosus

Drug development for the treatment of systemic lupus erythematosus (SLE) has largely focused on B-cell therapies. A greater understanding of the immunopathogenesis of SLE coupled with advanced bioengineering has allowed for clinical trials centered on other targets for SLE therapy. The authors discuss the benefits and shortcomings of focusing on T-cell-directed therapies in SLE and lupus nephritis clinical trials.

Advances in targeting co-inhibitory and co-stimulatory pathways in transplantation settings: the Yin to the Yang of cancer immunotherapy

In the past decade, the power of harnessing T-cell co-signaling pathways has become increasingly understood to have significant clinical importance. In cancer immunotherapy, the field has concentrated on two related modalities: First, targeting cancer antigens through highly activated chimeric antigen T cells (CAR-Ts) and second, re-animating endogenous quiescent T cells through checkpoint blockade. In each of these strategies, the therapeutic goal is to re-ignite T-cell immunity, in order to eradicate tumors. In transplantation, there is also great interest in targeting T-cell co-signaling, but with the opposite goal: in this field, we seek the Yin to cancer immunotherapy's Yang, and focus on manipulating T-cell co-signaling to induce tolerance rather than activation. In this review, we discuss the major T-cell signaling pathways that are being investigated for tolerance induction, detailing preclinical studies and the path to the clinic for many of these molecules. These include blockade of co-stimulation pathways and agonism of coinhibitory pathways, in order to achieve the delicate state of balance that is transplant tolerance: a state which guarantees lifelong transplant acceptance without ongoing immunosuppression, and with preservation of protective immune responses. In the context of the clinical translation of immune tolerance strategies, we discuss the significant challenge that is embodied by the fact that targeted pathway modulators may have opposing effects on tolerance based on their impact on effector vs regulatory T-cell biology. Achieving this delicate balance holds the key to the major challenge of transplantation: lifelong control of alloreactivity while maintaining an otherwise intact immune system.

Cellular and Molecular Mechanisms of Autoimmunity and Lupus Nephritis

Autoimmunity involves immune responses directed against self, which are a result of defective self/foreign distinction of the immune system, leading to proliferation of self-reactive lymphocytes, and is characterized by systemic, as well as tissue-specific, inflammation. Numerous mechanisms operate to ensure the immune tolerance to self-antigens. However, monogenetic defects or genetic variants that weaken immune tolerance render susceptibility to the loss of immune tolerance, which is further triggered by environmental factors. In this review, we discuss the phenomenon of immune tolerance, genetic and environmental factors that influence the immune tolerance, factors that induce autoimmunity such as epigenetic and transcription factors, neutrophil extracellular trap formation, extracellular vesicles, ion channels, and lipid mediators, as well as costimulatory or coinhibitory molecules that contribute to an autoimmune response. Further, we discuss the cellular and molecular mechanisms of autoimmune tissue injury and inflammation during systemic lupus erythematosus and lupus nephritis.

General and Specific Genetic Polymorphism of Cytokines-Related Gene in AITD

Autoimmune thyroid disease (AITD) shows the highest incidence among organ-specific autoimmune diseases and is the most common thyroid disease in humans, including Graves' disease (GD) and Hashimoto's thyroiditis (HT). The susceptibility to autoimmune diseases is affected by increased autoantibody levels, susceptibility gene polymorphisms, environmental factors, and psychological factors, but the pathogenesis remains unclear. Various cytokines and related genes encoding them play important roles in the development and progression of AITD. CD152, an expression product of the CTLA-4 gene, downregulates T cell activation. The A/A genotype polymorphism in the CT60 locus may reduce the production of thyroid autoantibodies. The C1858T polymorphism of the PTNP22 gene reduces the expression of its encoded LYP, which increases the risk of GD and HT. GD is an organ-specific autoimmune disease involving increased secretion of thyroid hormone, whereas HT may be associated with the destruction of thyroid gland tissue and hypothyroidism. These two diseases exhibit similar pathogenesis but opposite trends in the clinical manifestations. In this review, we focus on the structure and function of these cytokines and related genes in AITD, as well as the association of polymorphisms with susceptibility to GD and HT, and attempt to describe their differences in pathogenesis and clinical manifestations.

Lupus pathobiology based on genomics

Systemic lupus erythematosus (SLE) is an autoimmune disorder with complex genetic underpinnings. This review attempts to assemble the myriad of genomic findings to build a clearer picture of the pathobiology of SLE to serve as a guide for therapeutics. Over 100 genes are now known for SLE, and several more penetrant ones have led to the emergence of more defined lupus phenotypes. Also discussed here are the targeted therapies that have come up on the horizon and the specific biologic mechanisms of more traditional therapies which have only recently been explored. The diagnostic toolbox has been enhanced by the addition of new antibodies, gene expression signatures, and mutation panels. This provides an opportunity to piece together the lupus puzzle and even revisit the clinical classification of SLE.

Lessons Learned From the Clinical Trials of Novel Biologics and Small Molecules in Lupus Nephritis

Systemic lupus erythematosus (SLE) is a ripe area for drug development. There are great unmet needs, especially for those with lupus nephritis, in which good responses occur only in the minority of treated patients. An expanded understanding of immunopathogenesis of SLE coupled with the availability of sophisticated bioengineering technologies has resulted in the ability to supply the lupus community with the reagents needed to perform clinical trials. However, drug development in SLE has proven to be particularly challenging. Only one drug, belimumab, has been approved for patients with SLE through the traditional route of randomized controlled trials. The basis for our failures is unknown, but most assuredly relates to trial design issues, confounding by background medicines, and the multiplicity of active biologic pathways in this disease. Off-label use of failed trial drugs such as mycophenolate mofetil and rituximab paradoxically has become routine in many parts of the world. Despite the obstacles, there currently is unprecedented clinical trial activity in lupus nephritis, which most likely will lead to at least one drug approval in years to come.