Taming the TCR: antigen-specific immunotherapeutic agents for autoimmune diseases

T Cells in Atherosclerosis: Key Players in the Pathogenesis of Vascular Disease

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of lipid-rich plaques within arterial walls. T cells play a pivotal role in the pathogenesis of atherosclerosis in which they help orchestrate immune responses and contribute to plaque development and instability. Here, we discuss the recognition of atherosclerosis-related antigens that may trigger T cell activation together with additional signaling from co-stimulatory molecules and lesional cytokines. Although few studies have indicated candidates for the antigen specificity of T cells in atherosclerosis, further research is needed. Furthermore, we describe the pro-atherogenic and atheroprotective roles of diverse subsets of T cells such as CD4+ helper, CD8+ cytotoxic, invariant natural killer, and γδ T cells. To classify and quantify T cell subsets in atherosclerosis, we summarize current methods to analyze cellular heterogeneity including single cell RNA sequencing and T cell receptor (TCR) sequencing. Further insights into T cell biology will help shed light on the immunopathology of atherosclerosis, inform potential therapeutic interventions, and pave the way for precision medicine approaches in combating cardiovascular disease.

An appraisal of emerging therapeutic targets for multiple sclerosis derived from current preclinical models

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory, demyelinating, and neurodegenerative condition affecting the central nervous system (CNS). Although therapeutic approaches have become available over the last 20 years that markedly slow the progression of disease, there is no cure for MS. Furthermore, the capacity to repair existing CNS damage caused by MS remains very limited.

AREAS COVERED

Several animal models are widely used in MS research to identify potential druggable targets for new treatment of MS. In this review, we look at targets identified since 2019 in studies using these models, and their potential for effecting a cure for MS.

EXPERT OPINION

Refinement of therapeutic strategies targeting key molecules involved in the activation of immune cells, cytokine, and chemokine signaling, and the polarization of the immune response have dominated recent publications. While some progress has been made in identifying effective targets to combat chronic demyelination and neurodegeneration, much more work is required. Progress is largely limited by the gaps in knowledge of how the immune system and the nervous system interact in MS and its animal models, and whether the numerous targets present in both systems respond in the same way in each system to the same therapeutic manipulation.

Anti-double Stranded DNA Antibodies: Origin, Pathogenicity, and Targeted Therapies

Systemic lupus erythematosus (SLE) is characterized by high-titer serological autoantibodies, including antibodies that bind to double-stranded DNA (dsDNA). The origin, specificity, and pathogenicity of anti-dsDNA antibodies have been studied from a wider perspective. These autoantibodies have been suggested to contribute to multiple end-organ injuries, especially to lupus nephritis, in patients with SLE. Moreover, serum levels of anti-DNA antibodies fluctuate with disease activity in patients with SLE. By directly binding to self-antigens or indirectly forming immune complexes, anti-dsDNA antibodies can accumulate in the glomerular and tubular basement membrane. These autoantibodies can also trigger the complement cascade, penetrate into living cells, modulate gene expression, and even induce profibrotic phenotypes of renal cells. In addition, the expression of suppressor of cytokine signaling 1 is reduced by anti-DNA antibodies simultaneously with upregulation of profibrotic genes. Anti-dsDNA antibodies may even participate in the pathogenesis of SLE by catalyzing hydrolysis of certain DNA molecules or peptides in cells. Recently, anti-dsDNA antibodies have been explored in greater depth as a therapeutic target in the management of SLE. A substantial amount of data indicates that blockade of pathogenic anti-dsDNA antibodies can prevent or even reverse organ damage in murine models of SLE. This review focuses on the recent research advances regarding the origin, specificity, classification, and pathogenicity of anti-dsDNA antibodies and highlights the emerging therapies associated with them.

Inhibition of T Cell Receptor Activation by Semi-Synthetic Sesquiterpene Lactone Derivatives and Molecular Modeling of Their Interaction with Glutathione and Tyrosine Kinase ZAP-70

A variety of natural compounds have been shown to modulate T cell receptor (TCR) activation, including natural sesquiterpene lactones (SLs). In the present studies, we evaluated the biological activity of 11 novel semi-synthetic SLs to determine their ability to modulate TCR activation. Of these compounds, α-epoxyarglabin, cytisinyl epoxyarglabin, 1β,10α-epoxyargolide, and chloroacetate grosheimin inhibited anti-CD3-induced Ca²⁺ mobilization and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation in Jurkat T cells. We also found that the active SLs depleted intracellular glutathione (GSH) in Jurkat T cells, supporting their reactivity towards thiol groups. Because the zeta-chain associated tyrosine kinase 70 kDa (ZAP-70) is essential for TCR signaling and contains a tandem SH2 region that is highly enriched with multiple cysteines, we performed molecular docking of natural SLs and their semi-synthetic derivatives into the ZAP-70 binding site. The docking showed that the distance between the carbon atom of the exocyclic methylene group and the sulfur atom in Cys39 of the ZAP-70 tandem SH2 module was 3.04–5.3 Å for active compounds. Furthermore, the natural SLs and their derivatives could be differentiated by their ability to react with the Cys39 SH-group. We suggest that natural and/or semi-synthetic SLs with an α-methylene-γ-lactone moiety can specifically target GSH and the kinase site of ZAP-70 and inhibit the initial phases of TCR activation.

The natural sesquiterpene lactones arglabin, grosheimin, agracin, parthenolide, and estafiatin inhibit T cell receptor (TCR) activation

Inhibition of the T cell receptor (TCR) pathway represents an effective strategy for the treatment of T cell-mediated inflammatory and autoimmune diseases. To identify natural compounds that could inhibit inflammatory T cell responses, we screened 13 sesquiterpene lactones, including achillin, arglabin, argolide, argracin, 3β-hydroxyarhalin, artesin, artemisinin, estafiatin, grosheimin, grossmisin, leucomisine, parthenolide, and taurine, for their ability to modulate activation-induced Ca²⁺ mobilization in Jurkat T cells. Five of the compounds (arglabin, grosheimin, argracin, parthenolide, and estafiatin) inhibited anti-CD3-induced mobilization of intercellular Ca²⁺ ([Ca²⁺]_i) in Jurkat cells, with the most potent being parthenolide and argacin (IC₅₀ = 5.6 and 6.1 μM, respectively). Likewise, phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 in activated Jurkat cells was inhibited by these five compounds, with the most potent being parthenolide and estafiatin (IC₅₀ = 13.8 and 15.4 μM, respectively). These compounds also inhibited ERK1/2 phosphorylation in primary human T cells and depleted intracellular glutathione. In contrast, none of the sesquiterpene lactones inhibited ERK1/2 phosphorylation in HL60 cells transfected with N-formyl peptide receptor 2 (FPR2) and stimulated with the FPR2 peptide agonist WKYMVM, indicating specificity for T cell activation. Estafiatin, a representative sesquiterpene lactone, was also profiled in a cell-based phosphokinase array for 43 kinase phosphorylation sites, as well as in a cell-free competition binding assay for its ability to compete with an active-site directed ligand for 95 different protein kinases. Besides inhibition of ERK1/2 phosphorylation, estafiatin also inhibited phosphorylation of p53, AMPKα1, CREB, and p27 elicited by TCR activation in Jurkat cells, but it did not bind to any of 95 kinases evaluated. These results suggest that arglabin, grosheimin, agracin, parthenolide, and estafiatin can selectively inhibit initial phases of TCR activation and may be natural compounds with previously undescribed immunotherapeutic properties.

Protein tyrosine phosphatase SHP-1: resurgence as new drug target for human autoimmune disorders

Recognition of self-antigen and its destruction by the immune system is the hallmark of autoimmune diseases. During the developmental stages, immune cells are introduced to the self-antigen, for which tolerance develops. The inflammatory insults that break the immune tolerance provoke immune system against self-antigen, progressively leading to autoimmune diseases. SH2 domain containing protein tyrosine phosphatase (PTP), SHP-1, was identified as hematopoietic cell-specific PTP that regulates immune function from developing immune tolerance to mediating cell signaling post-immunoreceptor activation. The extensive research on SHP-1-deficient mice elucidated the diversified role of SHP-1 in immune regulation, and inflammatory process and related disorders such as cancer, autoimmunity, and neurodegenerative diseases. The present review focalizes upon the implication of SHP-1 in the pathogenesis of autoimmune disorders, such as allergic asthma, neutrophilic dermatosis, atopic dermatitis, rheumatoid arthritis, and multiple sclerosis, so as to lay the background in pursuance of developing therapeutic strategies targeting SHP-1. Also, new SHP-1 molecular targets have been suggested like SIRP-α, PIPKIγ, and RIP-1 that may prove to be the focal point for the development of therapeutic strategies.

Deep sequencing of the T cell receptor β repertoire reveals signature patterns and clonal drift in atherosclerotic plaques and patients

The T cell receptor (TCR) β repertoire directly reflects the status of T cell function. Meanwhile, the immune/inflammatory responses regulated by T cells are the critical determinants of atherosclerosis development. However, due to technical limitations, the composition and molecular characteristics of the TCR repertoire in atherosclerotic patients have not been fully elucidated. In the present study, we use powerful immune repertoire sequencing technology to study this issue. Results show that the utilization of V and/or J genes and the diversity of TCRβ repertoire in atherosclerotic plaques are significantly reduced compared to those in the peripheral blood of normal subjects and atherosclerotic patients. The frequencies of the common T cell clones with certain lengths of the complement determining region 3 regions are notably different among all groups. The high-frequency common clones are also increased in the atherosclerotic plaques compared to that in the other two groups. The expansion of several T cell clonotypes (V29-1J2-1, V20-1J1-6, V6-3J2-7 and V11-2J2-2) is validated in atherosclerotic patients. In short, this study reveals that the diversity of TCR β repertoire significantly decreases in atherosclerotic plaques, probably because of the reduced utilization of VJ genes and marked expansion of some T cell subclones. It provides the basis for understanding the roles of T lymphocytes in the pathogenesis of atherosclerosis.

Predicting the effects of potentially therapeutic modified peptides on polyclonal T cell populations in a mouse model of multiple sclerosis

Altered peptide ligands (APLs) have routinely been studied in clonal populations of Th cells that express a single T cell receptor (TCR), but results generated in this manner poorly predict the effects of APLs on polyclonal Th cells in vivo, contributing to the failure of phase II clinical trials of APLs in autoimmune diseases such as multiple sclerosis (MS). We have used a panel of APLs derived from an encephalitogenic epitope of myelin proteolipid protein to investigate the relationship between antigen cross-reactivity in a polyclonal environment, encephalitogenicity, and the capacity of an APL to provide protection against experimental autoimmune encephalomyelitis (EAE) in SJL mice. In general, polyclonal Th cell lines specific for encephalitogenic APLs cross-reacted with other encephalitogenic APLs, but not with non-encephalitogenic APLs, and vice versa. This, alongside analysis of TCR Vβ usage, suggested that encephalitogenic and non-encephalitogenic subgroups of APLs expand largely non-cross-reactive Th cell populations. As an exception to the rule, one non-encephalitogenic APL, L188, induced proliferation in polyclonal CD4⁺ T cells specific for the native encephalitogen, with minimal induction of cytokine production. Co-immunization of L188 alongside the native encephalitogen slightly enhanced disease development. In contrast, another APL, A188, which induced IL-10 production without proliferation in CD4⁺ T cells specific for the native encephalitogen, was able to protect against development of EAE in a dose-dependent fashion when co-immunized alongside the native encephalitogen. These results suggest that testing against polyclonal Th cell lines in vitro may be an effective strategy for distinguishing between potentially therapeutic and non-therapeutic APLs.