Prevention of lupus nephritis development in NZB/NZW mice by selective blockade of CD28

Celastrol ameliorates lupus by promoting apoptosis of autoimmune T cells and preventing autoimmune response in MRL/lpr mice

OBJECTIVE

Celastrol is a bioactive constituent extracted from Tripterygium wilfordii (thunder god vine). It has been demonstrated to have a therapeutic effect on experimental disease models for chronic inflammatory and immune disorders. In the present study, we investigated whether and how celastrol exerts a regulatory effect on the autoimmune response in MRL/lpr mice.

METHODS

We performed an in vivo study to determine the therapeutic effects of celastrol in MRL/lpr mice and then further investigated the underlying mechanism of celastrol in the regulation of the autoimmune response in MRL/lpr mice.

RESULTS

Celastrol showed a therapeutic effect in MRL/lpr mice by preventing the enlargement of the spleen and lymph nodes, alleviating renal injury, and reducing the levels of ANA and anti-double-stranded DNA antibodies. Furthermore, celastrol suppressed the in vivo inflammatory response in MRL/lpr mice by reducing the serum levels of multiple cytokines, including interleukin (IL)-6, tumour necrosis factor (TNF) and interferon (IFN)-γ, and the production of multiple antibody subsets, including total IgG, IgG1 and IgG2b. In vitro, celastrol reduced anti-CD3 antibody stimulation-induced T helper 1 and TNF-producing cells in CD4+ T cells of MRL/lpr mice. In addition, celastrol significantly affected B cell differentiation and prevented the generation of plasma cells from B cells in MRL/lpr mice by reducing the frequency of activated and germinal centre B cells. Celastrol treatment also affected T cell differentiation and significantly reduced central memory T cell frequencies in MRL/lpr mice. Importantly, celastrol treatment specifically promoted apoptosis of CD138+ but not CD138- T cells to suppress autoimmune T cell accumulation in MRL/lpr mice.

CONCLUSIONS

Celastrol exerted therapeutic effects on lupus by specifically promoting apoptosis of autoimmune T cells and preventing the progression of autoimmune response.

Immune Checkpoint Inhibitors and Lupus Erythematosus

Immune checkpoint inhibitors (ICIs) are the standard of care for a growing number of malignancies. Unfortunately, they are associated with a broad range of unique toxicities that mimic the presentations of primary autoimmune conditions. These adverse events are termed immune-related adverse events (irAEs), of which ICI-lupus erythematosus (ICI-LE) constitutes a small percentage. Our review aims to describe the available literature on ICI-LE and ICI treatment for patients with pre-existing lupus. Most diagnoses of ICI-LE had findings of only cutaneous lupus; four diagnoses of ICI-LE had systemic lupus manifestations. Over 90% (27 of 29) of cases received anti-PD-1/PDL-1 monotherapy, 1 received combination therapy, and 1 received only anti-CTLA-4 treatment. About three-fourths (22 of 29 or 76%) of patients with ICI-lupus were managed with topical steroids, 13 (45%) received hydroxychloroquine, and 10 (34%) required oral corticosteroids. In our case series, none of the patients with pre-existing lupus receiving ICI therapy for cancer had a flare of their lupus, but few had de novo irAE manifestations, all of which were characterized as low-grade. The review of the literature yielded seven ICI-LE flares from a total of 27 patients with pre-existing lupus who received ICI. Most flares were manageable without need for ICI cessation.

Current understanding of CTLA-4: from mechanism to autoimmune diseases

Autoimmune diseases (ADs) are characterized by the production of autoreactive lymphocytes, immune responses to self-antigens, and inflammation in related tissues and organs. Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is majorly expressed in activated T cells and works as a critical regulator in the inflammatory response. In this review, we first describe the structure, expression, and how the signaling pathways of CTLA-4 participate in reducing effector T-cell activity and enhancing the immunomodulatory ability of regulatory T (Treg) cells to reduce immune response, maintain immune homeostasis, and maintain autoimmune silence. We then focused on the correlation between CTLA-4 and different ADs and how this molecule regulates the immune activity of the diseases and inhibits the onset, progression, and pathology of various ADs. Finally, we summarized the current progress of CTLA-4 as a therapeutic target for various ADs.

Acazicolcept (ALPN-101), a dual ICOS/CD28 antagonist, demonstrates efficacy in systemic sclerosis preclinical mouse models

Background

Uncontrolled immune response with T cell activation has a key role in the pathogenesis of systemic sclerosis (SSc), a disorder that is characterized by generalized fibrosis affecting particularly the lungs and skin. Costimulatory molecules are key players during immune activation, and recent evidence supports a role of CD28 and ICOS in the development of fibrosis. We herein investigated the efficacy of acazicolcept (ALPN-101), a dual ICOS/CD28 antagonist, in two complementary SSc-related mouse models recapitulating skin fibrosis, interstitial lung disease, and pulmonary hypertension.

Methods

Expression of circulating soluble ICOS and skin-expressed ICOS was investigated in SSc patients. Thereafter, acazicolcept was evaluated in the hypochlorous acid (HOCL)-induced dermal fibrosis mouse model and in the Fra-2 transgenic (Tg) mouse model. In each model, mice received 400 μg of acazicolcept or a molar-matched dose of an Fc control protein twice a week for 6 weeks. After 6 weeks, skin and lung were evaluated.

Results

ICOS was significantly increased in the sera from SSc patients and in SSc skin biopsies as compared to samples from healthy controls. Similar body weight changes were observed between Fc control and acazicolcept groups in both HOCL and Fra-2 Tg mice suggesting a good tolerance of acazicolcept treatment. In mice challenged with HOCL, acazicolcept induced a significant decrease in dermal thickness, collagen content, myofibroblast number, and inflammatory infiltrates characterized by B cells, T cells, neutrophils, and macrophages. In the Fra-2 Tg mouse model, acazicolcept treatment reduced lung collagen content, fibrillar collagen, histological fibrosis score, and right ventricular systolic pressure (RVSP). A reduction in frequency of CD4+ and T effector memory cells and an increase in the percentage of CD4+ T naïve cells in spleen and lung of acazicolcept-treated Fra-2 Tg mice was observed as compared to Fc control-treated Fra-2 Tg mice. Moreover, acazicolcept reduced CD69 and PD-1 expression on CD4+ T cells from the spleen and the lung. Target engagement by acazicolcept was demonstrated by blockade of CD28 and ICOS detection by flow cytometry in treated mice.

Conclusions

Our results confirm the importance of costimulatory molecules in inflammatory-driven fibrosis. Our data highlight a key role of ICOS and CD28 in SSc. Using complementary models, we demonstrated that dual ICOS/CD28 blockade by acazicolcept decreased dermal and pulmonary fibrosis and alleviated pulmonary hypertension. These results pave the way for subsequent research on ICOS/CD28-targeted therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02709-2.

Bridging the Gap: Connecting the Mechanisms of Immune-Related Adverse Events and Autoimmunity Through PD-1

The emergence of anti-cytotoxic T-lymphocyte antigen 4 (anti-CTLA-4), anti-programmed cell death 1 ligand (anti-PD-1), and anti-PD-L1 antibodies as immune checkpoint inhibitors (ICIs) revolutionized the treatment of numerous types of tumors. These antibodies, both alone and in combination, provide great clinical efficacy as evidenced by tumor regression and increased overall patients' survival. However, with this success comes multiple challenges. First, while patients who respond to ICIs have outstanding outcomes, there remains a large proportion of patients who do not respond at all. This all-or-none response has led to looking downstream of programmed cell death 1 (PD-1) for additional therapeutic targets and for new combination therapies. Second, a majority of patients who receive ICIs go on to develop immune-related adverse events (irAEs) characterized by end-organ inflammation with T-cell infiltrates. The hallmarks of these clinically observed irAEs share many similarities with primary autoimmune diseases. The contribution of PD-1 to peripheral tolerance is a major mechanism for protection against expansion of self-reactive T-cell clones and autoimmune disease. In this review, we aim to bridge the gaps between our cellular and molecular knowledge of PD-1 signaling in T cells, ICI-induced irAEs, and autoimmune diseases. We will highlight shared mechanisms and the potential for new therapeutic strategies.

Cutting Edge: A Threshold of B Cell Costimulatory Signals Is Required for Spontaneous Germinal Center Formation in Autoimmunity

Cognate interactions between autoreactive B and T cells promote systemic lupus erythematosus pathogenesis by inter alia facilitating spontaneous germinal center (GC) formation. Whereas both myeloid and B cell APCs express B7 ligands (CD80 and CD86), the prevailing model holds that dendritic cell costimulation is sufficient for CD28-dependent T cell activation. In this study, we report that B cell-intrinsic CD80/CD86 deletion unexpectedly abrogates GCs in murine lupus. Interestingly, absent GCs differentially impacted serum autoantibodies. In keeping with distinct extrafollicular and GC activation pathways driving lupus autoantibodies, lack of GCs correlated with loss of RNA-associated autoantibodies but preserved anti-dsDNA and connective tissue autoantibody titers. Strikingly, even heterozygous B cell CD80/CD86 deletion was sufficient to prevent autoimmune GCs and RNA-associated autoantibodies. Together, these findings identify a key mechanism whereby B cells promote lupus pathogenesis by providing a threshold of costimulatory signals required for autoreactive T cell activation.

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.

The PD-1/PD-L pathway in rheumatic diseases

BACKGROUND/PURPOSE

Autoimmune diseases are diseases in which the body produces an abnormal immune response to self-antigens and damages its own tissues. Programmed death-1 (PD-1) and its ligands (PD-Ls) have been discovered to be important negative regulators of the immune system, playing crucial roles in autoimmunity.

METHODS

We analyzed the existing scientific literature dealing with this issue. In this review, the PD-1/PD-L pathway in the genetic susceptibility to and pathogenesis of rheumatic diseases is discussed. The PD-1/PD-L pathway might be helpful for diagnosing, evaluating the disease activity of and treating rheumatic diseases.

RESULTS

PD-1/PD-L gene polymorphisms are associated with a genetic predisposition to rheumatic disorders, which can provide reference information for diagnosis and disease activity. The conclusion of the crucial role of the PD-1/PD-L pathway in the pathogenesis of rheumatic diseases is consistent, but the details remain controversial. In some animal models, manipulating the PD-1/PD-L pathway could decrease disease severity. PD-1/PD-Ls may enable us to develop new therapeutics for patients with rheumatic diseases in the future.

CONCLUSION

The PD-1/PD-L pathway plays crucial roles in rheumatic disease. More work is needed to provide a better mechanistic understanding of the PD-1/PD-L pathway and to facilitate the precise therapeutic manipulation of this pathway.

Stimulatory and Inhibitory Co-signals in Autoimmunity

Co-receptors cooperatively regulate the function of immune cells to optimize anti-infectious immunity while limiting autoimmunity by providing stimulatory and inhibitory co-signals. Among various co-receptors, those in the CD28/CTLA-4 family play fundamental roles in the regulation of lymphocytes by modulating the strength, quality, and/or duration of the antigen receptor signal. The development of the lethal lymphoproliferative disorder and various tissue-specific autoimmune diseases in mice deficient for CTLA-4 and PD-1, respectively, clearly demonstrates their pivotal roles in the development and the maintenance of immune tolerance. The recent success of immunotherapies targeting CTLA-4 and PD-1 in the treatment of various cancers highlights their critical roles in the regulation of cancer immunity in human. In addition, the development of multifarious autoimmune diseases as immune-related adverse events of anti-CTLA-4 and anti-PD-1/PD-L1 therapies and the successful clinical application of the CD28 blocking therapy using CTLA-4-Ig to the treatment of arthritis assure their crucial roles in the regulation of autoimmunity in human. Accumulating evidences in mice and humans indicate that genetic and environmental factors strikingly modify effects of the targeted inhibition and potentiation of co-signals. In this review, we summarize our current understanding of the roles of CD28, CTLA-4, and PD-1 in autoimmunity. Deeper understandings of the context-dependent and context-independent functions of co-signals are essential for the appropriate usage and the future development of innovative immunomodulatory therapies for a diverse array of diseases.

Calpain in the cleavage of alpha-synuclein and the pathogenesis of Parkinson's disease

Parkinson's disease (PD) devastates 6.3 million people, ranking it as one of the most prevalent neurodegenerative motor disorders worldwide. PD patients may manifest symptoms of postural instability, bradykinesia, and resting tremors as a result of increasing α-synuclein aggregation and neuron death with disease progression. Therapy options are limited, and those available to patients may worsen their condition. Thus, investigations to understand disease progression may help develop therapeutic strategies for improvement of quality of life for patients suffering from PD. This review provides an overview of α-synuclein, a presynaptic neuronal protein whose function in the healthy brain and PD pathology remains a mystery. This review also focuses on calcium-induced activation of calpain, a neutral protease, and the subsequent cascade of cellular processing of α-synuclein and emerging defense responses observed in experimental models of PD: microglial activation, dysregulation of T cells, and inflammatory responses in the brain. In addition, this review discusses the events of cross presentation of synuclein peptides by professional antigen presenting cells and microglia, induction of inflammatory responses in the periphery and brain, and emerging calpain-targeted therapeutic strategies to attenuate neuronal death in PD.

Aberrant Expressions of Co-stimulatory and Co-inhibitory Molecules in Autoimmune Diseases

Co-signaling molecules include co-stimulatory and co-inhibitory molecules and play important roles in modulating immune responses. The roles of co-signaling molecules in autoimmune diseases have not been clearly defined. We assessed the expressions of co-stimulatory and co-inhibitory molecules in autoimmune diseases through a bioinformatics-based study. By using datasets of whole-genome transcriptome, the expressions of 54 co-stimulatory or co-inhibitory genes in common autoimmune diseases were analyzed using Robust rank aggregation (RRA) method. Nineteen array datasets and 6 RNA-seq datasets were included in the RRA discovery study and RRA validation study, respectively. Significant genes were further validated in several autoimmune diseases including Graves' disease (GD). RRA discovery study suggested that CD160 was the most significant gene aberrantly expressed in autoimmune diseases (Adjusted P = 5.9E-12), followed by CD58 (Adjusted P = 5.7E-06) and CD244 (Adjusted P = 9.5E-05). RRA validation study also identified CD160 as the most significant gene aberrantly expressed in autoimmune diseases (Adjusted P = 5.9E-09). We further found that the aberrant expression of CD160 was statistically significant in multiple autoimmune diseases including GD (P < 0.05), and CD160 had a moderate role in diagnosing those autoimmune diseases. Flow cytometry confirmed that CD160 was differentially expressed on the surface of CD8⁺ T cells between GD patients and healthy controls (P = 0.002), which proved the aberrant expression of CD160 in GD at the protein level. This study suggests that CD160 is the most significant co-signaling gene aberrantly expressed in autoimmune diseases. Treatment strategy targeting CD160-related pathway may be promising for the therapy of autoimmune diseases.

CD28 Deficiency Ameliorates Thoracic Blast Exposure-Induced Oxidative Stress and Apoptosis in the Brain through the PI3K/Nrf2/Keap1 Signaling Pathway

Blast exposure is a worldwide public health concern, but most related research has been focused on direct injury. Thoracic blast exposure-induced neurotrauma is a type of indirect injuries where research is lacking. As CD28 stimulates T cell activation and survival and contributes to inflammation initiation, it may play a role in thoracic blast exposure-induced neurotrauma. However, it has not been investigated. To explore the effects of CD28 on thoracic blast exposure-induced brain injury and its potential molecular mechanisms, a mouse model of thoracic blast exposure-induced brain injury was established. Fifty C57BL/6 wild-type (WT) and fifty CD28 knockout (CD28^-/-) mice were randomly divided into five groups (one control group and four model groups), with ten mice (from each of the two models) for each group. Lung and brain tissue and serum samples were collected at 12 h, 24 h, 48 h, and 1 week after thoracic blast exposure. Histopathological changes were detected by hematoxylin-eosin staining. The expressions of inflammatory-related factors were detected by ELISA. Oxidative stress in the brain tissue was evaluated by determining the generation of reactive oxygen species (ROS) and the expressions of thioredoxin (TRX), malondialdehyde (MDA), SOD-1, and SOD-2. Apoptosis in the brain tissue was evaluated by TUNEL staining and the levels of Bax, Bcl-xL, Bad, Cytochrome C, and caspase-3. In addition, proteins of related pathways were also studied by western blotting and immunofluorescence. We found that CD28 deficiency significantly reduced thoracic blast exposure-induced histopathological changes and decreased the levels of inflammatory-related factors, including IL-1β, TNF-α, and S100β. In the brain tissue, CD28 deficiency also significantly attenuated thoracic blast exposure-induced generation of ROS and expressions of MDA, TRX, SOD-1, and SOD-2; lowered the number of apoptotic cells and the expression of Bax, cleaved caspase-3, Cytochrome C, and Bad; and maintained Bcl-xL expression. Additionally, CD28 deficiency significantly ameliorated thoracic blast exposure-induced increases of p-PI3K and Keap1 and the decrease of Nrf2 expression in the brain. Our results indicate that CD28 deficiency has a protective effect on thoracic blast exposure-induced brain injury that might be associated with the PI3K/Nrf2/Keap1 signaling pathway.

A selective CD28 antagonist and rapamycin synergise to protect against spontaneous autoimmune diabetes in NOD mice

AIMS/HYPOTHESIS

The CD28/B7 interaction is critical for both effector T cell activation and forkhead box P3 (FOXP3)⁺ regulatory T cell (Treg) generation and homeostasis, which complicates the therapeutic use of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4)-immunoglobulin fusion protein (CTLA-4Ig) in autoimmunity. Here, we evaluated the impact of a simultaneous and selective blockade of the CD28 and mammalian target of rapamycin (mTOR) pathways in the NOD mouse model of type 1 diabetes.

METHODS

NOD mice were treated with PEGylated anti-CD28 Fab' antibody fragments (PV1-polyethylene glycol [PEG], 10 mg/kg i.p., twice weekly), rapamycin (1 mg/kg i.p., twice weekly) or a combination of both drugs. Diabetes incidence, pancreatic islet infiltration and autoreactive T cell responses were analysed.

RESULTS

We report that 4 week administration of PV1-PEG combined with rapamycin effectively controlled the progression of autoimmune diabetes in NOD mice at 10 weeks of age by reducing T cell activation and migration into the pancreas. Treatment with rapamycin alone was without effect, as was PV1-PEG monotherapy initiated at 4, 6 or 10 weeks of age. Prolonged PV1-PEG administration (for 10 weeks) accelerated diabetes development associated with impaired peripheral Treg homeostasis. This effect was not observed with the combined treatment.

CONCLUSIONS/INTERPRETATION

CD28 antagonist and rapamycin treatment act in a complementary manner to limit T cell activation and infiltration of pancreatic islets and diabetes development. These data provide new perspectives for the treatment of autoimmune diabetes and support the therapeutic potential of protocols combining antagonists of CD28 (presently in clinical development) and the mTOR pathway.

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.