Autoreactive CD4 Research Articles

PD-1+CD8+ T Cell-Mediated Hepatocyte Pyroptosis Promotes Progression of Murine Autoimmune Liver Disease.

The specific mechanisms underlying effector pathways in autoimmune liver disease remain enigmatic and therefore constructing appropriate murine models to investigate disease pathogenesis becomes critical. A spontaneous severe murine model of autoimmune liver disease has been previously established in dnTGFβRII Aire-/- mice, exhibiting disease phenotypes that resemble both human primary biliary cholangitis (PBC) and autoimmune hepatitis (AIH). The data suggests that auto-reactive liver-specific CD8+ T cells are the primary pathogenic cells in liver injury. In this study, these data are advanced through the use of both single-cell sequencing and extensive in vitro analysis. The results identify a specific expanded pathogenic subset of PD-1+CD8+ T cells in the liver, exhibiting strong functional activity and cytotoxicity against target cells. Depletion of PD-1+CD8+ T cells using CAR-T cells effectively alleviates the disease. GSDMD-mediated pyroptosis is found to be aberrantly activated in the livers of model mice, and treatment with a GSDMD-specific inhibitor significantly inhibits disease progression. In vitro experiments reveal that PD-1+CD8+ T cells can induce the pyroptosis of hepatocytes through elevated production of granzyme B and perforin-1. These results provide a novel explanation for the cytotoxic activity of pathogenic liver PD-1+CD8+ T cells in autoimmune liver diseases and offer potential therapeutic targets.

Preclinical characterization of MTX-101: a novel bispecific CD8 Treg modulator that restores CD8 Treg functions to suppress pathogenic T cells in autoimmune diseases

IntroductionRegulatory CD8 T cells (CD8 Treg) are responsible for the selective killing of self-reactive and pathogenic CD4 T cells. In autoimmune disease, CD8 Treg may accumulate in the peripheral blood but fail to control the expansion of pathogenic CD4 T cells that subsequently cause tissue destruction. This CD8 Treg dysfunction is due in part to the expression of inhibitory killer immunoglobulin-like receptors (KIR; KIR2DL isoforms [KIR2DL1, KIR2DL2, and KIR2DL3]); these molecules serve as autoimmune checkpoints and limit CD8 Treg activation.MethodsHere we describe the pre-clinical characterization of MTX-101, a bispecific antibody targeting inhibitory KIR and CD8. Using human peripheral blood mononuculear cells (PBMC) derived from healthy donors and autoimmune patients, humanized mouse models, and human derived tissue organoids, we evaluated the molecular mechanisms and functional effects of MTX-101.ResultsBy binding to KIR, MTX-101 inhibited KIR signaling that can restore CD8 Treg ability to eliminate pathogenic CD4 T cells. MTX-101 bound and activated CD8 Treg in human peripheral blood mononuclear cells (PBMC), resulting in increased CD8 Treg cytolytic capacity, activation, and prevalence. Enhancing CD8 Treg function with MTX-101 reduced pathogenic CD4 T cell expansion and inflammation, without increasing pro-inflammatory cytokines or activating immune cells that express either target alone. MTX-101 reduced antigen induced epithelial cell death in disease affected tissues, including in tissue biopsies from individuals with autoimmune disease (i.e., celiac disease, Crohn’s disease). The effects of MTX-101 were specific to autoreactive CD4 T cells and did not suppress responses to viral and bacterial antigens. In a human PBMC engrafted Graft versus Host Disease (GvHD) mouse model of acute inflammation, MTX-101 bound CD8 Treg and delayed onset of disease. MTX-101 induced dose dependent binding, increased prevalence and cytolytic capacity of CD8 Treg, as well as increased CD4 T cell death. MTX-101 selectively bound CD8 Treg without unwanted immune cell activation or increase of pro-inflammatory serum cytokines and exhibited an antibody-like half-life in pharmacokinetic and exploratory tolerability studies performed using IL-15 transgenic humanized mice with engrafted human lymphocytes, including CD8 Treg at physiologic ratios.ConclusionCollectively, these data support the development of MTX-101 for the treatment of autoimmune diseases.

Mucosal Addressin Cell Adhesion Molecule-1 Mediates T Cell Migration into Pancreas-Draining Lymph Nodes for Initiation of the Autoimmune Response in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease that is caused by autoreactive T cell-mediated destruction of insulin-producing β cells in the pancreatic islets. Although naive autoreactive T cells are initially primed by islet antigens in pancreas-draining lymph nodes (pan-LNs), the adhesion molecules that recruit T cells into pan-LNs are unknown. We show that high endothelial venules in pan-LNs of young nonobese diabetic mice have a unique adhesion molecule profile that includes strong expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Anti-MAdCAM-1 antibody blocked more than 80% of the migration of naive autoreactive CD4+ T cells from blood vessels into pan-LNs. Transient blockade of MAdCAM-1 in young nonobese diabetic mice led to increased numbers of autoreactive regulatory CD4+ T cells in pan-LNs and pancreas and to long-lasting protection from T1D. These results indicate the importance of MAdCAM-1 in the development of T1D and suggest MAdCAM-1 as a potential therapeutic target for treating T1D.

Vitiligo: From mechanisms of disease to treatable pathways

AbstractVitiligo is a chronic autoimmune‐mediated disease characterised by the loss of pigmentary melanocytes in the epidermis. Vitiligo is associated with loss of functional epithelium and significant reductions in quality of life with limited long‐term treatment options, highlighting a continued unmet clinical need. A comprehensive understanding of the pathophysiology and newly investigated treatment pathways may guide multimodal treatment strategies and identify future drug targets. The pathology of vitiligo is multifactorial; however, environmental insults in genetically susceptible populations may lead to disease development. Autoreactive CD8+ T‐cells that target melanocytes and release inflammatory mediators, including interferon‐γ and interleukins 2, 6, 15, 17 and 33 among others, have been identified in vitiligo pathogenesis. Treatment modalities for vitiligo revolve around six broad disease concepts, including procedural modalities (tissue and cellular grafting), phototherapy, stem cells, anti‐inflammatories, genetic polymorphisms and antioxidants/vitamins/herbals. Genetic polymorphisms, such as catalase gene variations and toll‐like receptor polymorphisms, along with stem cell targets such as melanocytes derived from stem cells, have been implicated in vitiligo onset and possible treatment. Novel JAK‐STAT inhibitors have been recently investigated for vitiligo, whereas topical corticosteroids and calcineurin inhibitors continue to be used. Vitamin D, vitamin E, zinc, copper, piperine, pseudo catalase and other vitamins/herbals may improve vitiligo outcomes primarily through antioxidant supplementation pathways. Future studies should investigate alternative drug pathways and targets implicated in vitiligo in large patient cohorts, as well as treatments that target suspected causative immune cells, including memory T‐cells, which may provide long‐lasting disease‐free remission.

LL37-DNA Complex Drives Vitiligo Progression Through TLR9-MyD88 Signaling Pathways.

Vitiligo is an autoimmune disorder characterized by chronic depigmentation and milk-white patches on the skin. Skin infiltration by autoreactive CD8+ T cells causes melanocyte destruction in vitiligo. Multiple risk factors, particularly immune-related inflammatory factors, are involved in the disappearance of melanocytes. LL37 is a classic damage-associated molecular pattern molecule that is involved in the development of various autoimmune diseases. An enhanced expression of LL37 in vitiligo is known; however, the exact role of LL37 in melanocyte loss has not yet been elucidated. In the present study, we detected increased LL37 expression in vitiligo serum and lesions. Furthermore, we confirmed that cultured keratinocytes released LL37 after treatment with H2O2. Moreover, the LL37-DNA complex enhanced the secretion of CXCL9, CXCL10, and CXCL16 from keratinocytes via the TLR9-MyD88 signaling pathway and facilitated the migration of CD8+ T cells. Altogether, our study demonstrates that LL37 released from keratinocytes binds to DNA and contributes to melanocyte destruction under oxidative stress-induced autoimmunity in vitiligo.

Targeting the autoreactive CD8+ T-cell receptor in type 1 diabetes: Insights from scRNA-seq for immunotherapy

Type 1 Diabetes (T1D) is an autoimmune disease characterized by the attack and destruction of Pancreatic islet beta cells by T cells. Understanding the role of T-cell receptor (TCR) in the development of T1D is of paramount importance. This study employs single-cell RNA sequencing (scRNA-seq) to delve into the mechanistic actions and potential therapeutic applications of autoreactive stem cell-like CD8 TCR in T1D. By retrieving T-cell data from non-obese diabetic (NOD) mice via the GEO database, it was revealed that CD8+ T cells are the predominant T-cell subset in the pancreatic tissue of T1D mice, along with the identification of T-cell marker genes closely associated with T1D. Moreover, the gene TRAJ23 exhibits a preference for T1D, and its knockout alleviates T1D symptoms and adverse reactions in NOD mice. Additionally, engineered TCR-T cells demonstrate significant cytotoxicity towards β cells in T1D.

RNF213 promotes Treg cell differentiation by facilitating K63-linked ubiquitination and nuclear translocation of FOXO1

Autoreactive CD4+ T helper cells are critical players that orchestrate the immune response both in multiple sclerosis (MS) and in other neuroinflammatory autoimmune diseases. Ubiquitination is a posttranslational protein modification involved in regulating a variety of cellular processes, including CD4+ T cell differentiation and function. However, only a limited number of E3 ubiquitin ligases have been characterized in terms of their biological functions, particularly in CD4+ T cell differentiation and function. In this study, we found that the RING finger protein 213 (RNF213) specifically promoted regulatory T (Treg) cell differentiation in CD4+ T cells and attenuated autoimmune disease development in an FOXO1-dependent manner. Mechanistically, RNF213 interacts with Forkhead Box Protein O1 (FOXO1) and promotes nuclear translocation of FOXO1 by K63-linked ubiquitination. Notably, RNF213 expression in CD4+ T cells was induced by IFN-β and exerts a crucial role in the therapeutic efficacy of IFN-β for MS. Together, our study findings collectively emphasize the pivotal role of RNF213 in modulating adaptive immune responses. RNF213 holds potential as a promising therapeutic target for addressing disorders associated with Treg cells.

Exploring the Role of PD-1 in the Autoimmune Response: Insights into Its Implication in Systemic Lupus Erythematosus.

Despite advances in understanding systemic lupus erythematosus (SLE), many challenges remain in unraveling the precise mechanisms behind the disease's development and progression. Recent evidence has questioned the role of programmed cell death protein 1 (PD-1) in suppressing autoreactive CD4+ T cells during autoimmune responses. Research has investigated the potential impacts of PD-1 on various CD4+ T-cell subpopulations, including T follicular helper (Tfh) cells, circulating Tfh (cTfh) cells, and T peripheral helper (Tph) cells, all of which exhibit substantial PD-1 expression and are closely related to several autoimmune disorders, including SLE. This review highlights the complex role of PD-1 in autoimmunity and emphasizes the imperative for further research to elucidate its functions during autoreactive T-cell responses. Additionally, we address the potential of PD-1 and its ligands as possible therapeutic targets in SLE.

Direct presentation of inflammation-associated self-antigens by thymic innate-like T cells induces elimination of autoreactive CD8+ thymocytes

Upregulation of diverse self-antigens that constitute components of the inflammatory response overlaps spatially and temporally with the emergence of pathogen-derived foreign antigens. Therefore, discrimination between these inflammation-associated self-antigens and pathogen-derived molecules represents a unique challenge for the adaptive immune system. Here, we demonstrate that CD8+ T cell tolerance to T cell-derived inflammation-associated self-antigens is efficiently induced in the thymus and supported by redundancy in cell types expressing these molecules. In addition to thymic epithelial cells, this included thymic eosinophils and innate-like T cells, a population that expressed molecules characteristic for all major activated T cell subsets. We show that direct T cell-to-T cell antigen presentation by minute numbers of innate-like T cells was sufficient to eliminate autoreactive CD8+ thymocytes. Tolerance to such effector molecules was of critical importance, as its breach caused by decreased thymic abundance of a single model inflammation-associated self-antigen resulted in autoimmune elimination of an entire class of effector T cells.

Tissue-resident memory T cells break tolerance to renal autoantigens and orchestrate immune-mediated nephritis

Immune-mediated nephritis is a leading cause of acute kidney injury and chronic kidney disease. While the role of B cells and antibodies has been extensively investigated in the past, the advent of immune-checkpoint inhibitors has led to a reappraisal of the role of T cells in renal immunology. However, it remains elusive how T cells with specificity for renal autoantigens are activated and participate in immune-mediated nephritis. Here, we followed the fate and function of pathogen-activated autoreactive CD8 T cells that are specific for a renal autoantigen. We demonstrate that recently activated splenic CD8 T cells developed a hybrid phenotype in the context of renal autoantigen cross-presentation, combining hallmarks of activation and T cell dysfunction. While circulating memory T cells rapidly disappeared, tissue-resident memory T cells emerged and persisted within the kidney, orchestrating immune-mediated nephritis. Notably, T cells infiltrating kidneys of patients with interstitial nephritis also expressed key markers of tissue residency. This study unveils how a tissue-specific immune response can dissociate from its systemic counterpart driving a compartmentalized immune response in the kidneys of mice and man. Consequently, targeting tissue-resident memory T cells emerges as a promising strategy to control immune-mediated kidney disease.

Differential expression of serum CXCL9 and CXCL10 levels in vitiligo patients and their correlation with disease severity and stability: A cross-sectional study.

Background Vitiligo is an acquired disorder of pigmentation with an elusive pathogenesis, though various theories have been proposed. The presence of peri-lesional autoreactive CD8+ T cell infiltrate suggests the involvement of abnormal immune responses and autoimmunity in vitiligo. Recent studies have identified the IFN-γ-CXCL9/CXCL-10 axis as a key component of the autoimmune response that perpetuates disease activity in vitiligo. Objectives The primary objective was to estimate serum CXCL9 and CXCL10 levels in vitiligo patients compared to age- and sex-matched controls. Additionally, the study aimed to find correlations between CXCL9 and CXCL10 levels and disease severity and stability. Secondary objectives included comparing levels in segmental/nonsegmental vitiligo and stable/progressive vitiligo and assessing the impact of age and gender. Methods A hospital-based cross-sectional study included 60 vitiligo patients and 30 age- and sex-matched controls. Serum levels of CXCL9 and CXCL10 were assessed using Enzyme-linked immunosorbent assay (ELISA). Cases were clinically evaluated for the type of vitiligo (segmental or non-segmental), disease severity (VASI score), and disease stability (VIDA score). Statistical analysis included t-tests, chi-square tests, and correlation coefficients. P value less than 0.5 was taken as significant. Results Serum CXCL9 and CXCL10, both, were significantly raised in vitiligo patients as compared to controls (p-value = 0.001* & 0.001* respectively) and correlated positively with both VASI score (p-value = 0.001* & 0.001* respectively) and with VIDA score (p-value = 0.032* & 0.001* respectively). Serum CXCL10 showed significant elevation in progressive vitiligo, and CXCL9 exhibited a non-significant trend. No significant difference was observed between segmental and non-segmental vitiligo. Both chemokines positively correlated with disease severity and stability, while age and gender did not significantly impact chemokine levels. Conclusion The expression of chemokines CXCL9 and CXCL10 is markedly increased and correlated positively with disease severity & instability, underscoring their mechanistic role in vitiligo pathogenesis. The values were also higher in the progressive group than in the stable group, inferring their conceivable potential as serum biomarkers. Both serum CXCL9 and CXCL10 were significantly elevated in vitiligo patients compared to controls and they can be used as potential serum biomarkers for assessing the disease activity. Limitations Small sample size of control population. The voluntary sampling technique led to an unequal number of patients in progressive and stable vitiligo groups, as well as in segmental and non-segmental groups. The current study did not include blister fluid analysis and the effect of therapy on the chemokine levels. Conclusion The expression of chemokines CXCL9 and CXCL10 is markedly increased and correlates positively with disease severity and instability, underscoring their mechanistic role in vitiligo pathogenesis. The values were also higher in the progressive group than in the stable group, inferring their conceivable potential as serum biomarkers. *represents statistically significant results.

Real-world effectiveness and safety of tofacitinib for alopecia areata: A retrospective cohort study of 202 patients.

Alopecia areata (AA) is an autoimmune hair loss disorder characterised by collapse of hair follicle immune privilege and mediated by autoreactive CD8+ T lymphocytes and natural killer cells. Treatment is often unsatisfactory. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway is implicated in the pathogenesis of AA and Janus Kinase inhibitor (JAKi) medications are promising emerging treatments for AA. We evaluated the safety and effectiveness of tofacitinib in a real-world setting over 18 months of treatment. A retrospective cohort study of all patients with scalp AA commenced on tofacitinib between 1 November 2016 and 31 May 2019. The primary endpoint was the percent change in Severity of Alopecia Tool (SALT) score at 18 months. Two hundred and two patients were included. After 18 months of treatment, 55.9%, 42.6% and 29.2% achieved 50%, 75% and 90% reductions in their SALT scores respectively. Increased duration of AA was a negative predictor of hair regrowth. Males and patients with baseline SALT ≥90 were slower to respond to treatment in the first 12 months. One hundred and twenty-four patients and 168 patients received concomitant systemic corticosteroids or low-dose oral minoxidil during tofacitinib therapy respectively. There were no serious adverse events. Tofacitinib was a safe and effective treatment for patients with moderate-to-severe AA. Further randomised controlled studies are needed to establish the optimal treatment regimen.

Autoimmune CD8+ T cells in type 1 diabetes: from single-cell RNA sequencing to T-cell receptor redirection.

Type 1 diabetes (T1D) is an organ-specific autoimmune disease caused by pancreatic β cell destruction and mediated primarily by autoreactive CD8+ T cells. It has been shown that only a small number of stem cell-like β cell-specific CD8+ T cells are needed to convert normal mice into T1D mice; thus, it is likely that T1D can be cured or significantly improved by modulating or altering self-reactive CD8+ T cells. However, stem cell-type, effector and exhausted CD8+ T cells play intricate and important roles in T1D. The highly diverse T-cell receptors (TCRs) also make precise and stable targeted therapy more difficult. Therefore, this review will investigate the mechanisms of autoimmune CD8+ T cells and TCRs in T1D, as well as the related single-cell RNA sequencing (ScRNA-Seq), CRISPR/Cas9, chimeric antigen receptor T-cell (CAR-T) and T-cell receptor-gene engineered T cells (TCR-T), for a detailed and clear overview. This review highlights that targeting CD8+ T cells and their TCRs may be a potential strategy for predicting or treating T1D.

Reshaping immune cells and the antigen-specific repertoire by anti-CD3 mAb teplizumab in Type 1 diabetes

Abstract Teplizumab, a FcR non-binding anti-CD3 mAb, is approved to delay progression of type 1 diabetes (T1D) at-risk patients. Previous investigations described the immediate effects of the 14-day treatment, but longer-term effects of the drug remain unknown. We analyzed the phenotypes, transcriptome, and repertoire of peripheral blood and autoreactive CD8+ T cells from individuals at-risk for T1D, before and after teplizumab. There were changes in CD4+ and CD8+ T cells at 3 months and 18 months after treatment in genes related to immune regulation. The differential gene expression in the T cells increased after drug was cleared. Persistent EOMES expression was a predictor for the time to clinical T1D diagnosis. Our trajectory analysis showed differentiation into cells with gene signatures related to immunoregulation and exhaustion after teplizumab treatment. This analysis aligned with inhibition of expansion of autoreactive CD8+, which was observed with the placebo, but not following teplizumab. These findings illustrate that a single course of teplizumab can instigate substantial T cell changes at 3 months, with evolution of CD8+ T cell exhaustion up to 18 months. Teplizumab restrains the expansion of autoantigen reactive CD8+ cells, suggesting mechanisms underlying operational tolerance.

Whole-body irradiation impairs naïve CD4 T cell function

Abstract Advancements in nuclear power and radiotherapy have expanded new avenues for whole-body irradiation (WBI) to humans, urging the need to understand its impact on immune cells. While most studies focus on the numerical recovery of naïve T cells post-WBI, less is known regarding its impact on their function. We subjected B6 SPF mice to 0/5Gy doses of WBI and used I-Ab tetramer enrichment to track the recovery of naïve CD4s of different antigen specificities post WBI. The number of MOG40 specific CD4 T cells is diminished 10 days post-irradiation (DPR), and recovered by 40DPR. To test if they are able to induce EAE post-WBI, we administered MOG+CFA, followed by pertussis toxin (PTX). The 10DPR mice showed delayed EAE development, likely due to diminished MOG40 naïve precursors. Interestingly, the 40DPR mice potentiated EAE compared to the 0Gy mice, evidenced by increased CD4 priming in the dLN, and spine infiltration. While WBI-mediated CD4 T cell-intrinsic changes could contribute to the timing/severity of EAE, T cell-extrinsic factors could also influence disease. To test if WBI compromises the blood-brain barrier (BBB) and facilitates EAE progression, EAE is induced in +/-WBI mice without PTX. In the absence of PTX, 0Gy mice did not develop EAE, while the 10- and 40DPR mice developed EAE suggesting BBB impairment. Overall, WBI directly impacts the number and function of autoreactive CD4 T cells, while helping them enter the spine by changing the environment.

Unraveling the Role of CD137 in Treg-Mediated Suppression of Type 1 Diabetes: Insights from Treg-Specific CD137 Knockout Mice

Abstract CD137, encoded by Tnfrsf9, acts as a costimulatory molecule on activated T cells. Conversely, soluble CD137 exerts immunosuppression by binding to CD137L on T cells, inhibiting activation. In the NOD mouse model of Type 1 Diabetes (T1D), CD137 expression in Foxp3+ regulatory CD4 T cells (Tregs) inhibits T1D, but the underlying mechanism remains elusive. To investigate the role of CD137 in Treg-mediated T1D suppression, we generated Treg-specific CD137 knockout mice (NOD.Treg-Tnfrsf9-/-). While no systemic inflammation was observed, these mice developed accelerated T1D compared to wildtype control. Reduced serum-soluble CD137 in these mice indicated Tregs are its main producers. scRNA-seq revealed phenotypic alterations of Tregs isolated from pancreatic islets of NOD.Treg-Tnfrsf9-/- mice, showing lower activation and clonal expansion than wildtype counterparts. Reduced Treg activity in these mice was associated with increased frequencies of islet-activated CD8 T cell subsets and their clonal expansion. MHC class I tetramer staining revealed a higher frequency of β-cell antigen IGRP206-214 specific CD8 T cells in NOD.Treg-Tnfrsf9-/- mice. No discernible differences in the initial expansion and activation of β-cell autoreactive CD8 T cells in pancreatic lymph nodes were observed. Our results suggest CD137 expression in Tregs is critical for restraining ongoing autoimmune inflammation in islets of NOD mice but dispensable for controlling autoreactive T cells in lymphoid tissues.

Immunopeptidome mining reveals a novel ERS-induced target in T1D.

Autoreactive CD8+ T cells play a key role in type 1 diabetes (T1D), but the antigen spectrum that activates autoreactive CD8+ T cells remains unclear. Endoplasmic reticulum stress (ERS) has been implicated in β-cell autoantigen generation. Here, we analyzed the major histocompatibility complex class I (MHC-I)-associated immunopeptidome (MIP) of islet β-cells under steady and ERS conditions and found that ERS reshaped the MIP of β-cells and promoted the MHC-I presentation of a panel of conventional self-peptides. Among them, OTUB258-66 showed immunodominance, and the corresponding autoreactive CD8+ T cells were diabetogenic in nonobese diabetic (NOD) mice. High glucose intake upregulated pancreatic OTUB2 expression and amplified the OTUB258-66-specific CD8+ T-cell response in NOD mice. Repeated OTUB258-66 administration significantly reduced the incidence of T1D in NOD mice. Interestingly, peripheral blood mononuclear cells (PBMCs) from patients with T1D, but not from healthy controls, showed a positive IFN-γ response to human OTUB2 peptides. This study provides not only a new explanation for the role of ERS in promoting β-cell-targeted autoimmunity but also a potential target for the prevention and treatment of T1D. The data are available via ProteomeXchange with the identifier PXD041227.

Abstract 6594: 4-1BB: A double-edged sword for T cells

Abstract Background: The costimulatory receptor 4-1BB (CD137) is expressed on the surface of activated T cells, playing a pivotal role in enhancing T cell responses and emerging as a promising target for cancer immunotherapy. Its primary ligand, 4-1BBL (CD137L), is found on antigen-presenting cells and various immune cells. The interaction between 4-1BBL and 4-1BB provides crucial costimulatory signals to both CD4+ and CD8+ T cells, amplifying their activation and effector functions. However, recent studies have shed light on a distinct role of 4-1BB in T cells. Prior work has revealed that 4-1BB can distinguish intratumoral regulatory T cells (Tregs) from peripheral Tregs and other CD4 lineage T cells in cancer patients, and the overexpression of 4-1BB on Tregs has been associated with unfavorable survival outcomes. Additionally, targeting 4-1BB with IgG2a isotype antibodies has shown significant anti-tumor efficacy in preclinical models by depleting Tregs. Furthermore, agonist monoclonal antibodies targeting 4-1BB have not only shown promise in inducing tumor regressions but also demonstrated improved outcomes in mouse models of autoimmune diseases induced by autoreactive CD4+ T cells. These findings indicate the existence of specific ligands or factors that modulate 4-1BB function on T cells that can vary depending on the disease state. Methods: To identify potential ligand(s) involved in the modulation of 4-1BB function, we developed an innovative CRISPR/Cas9-based transcriptional activation (CRISPRa) screening system that integrates CRISPR/Cas9-guide mediated gene activation, high avidity bead-based selection, serial enrichment, and flow cytometry-based monitoring. This screening platform provides enhanced sensitivity for identifying extracellular interactions between receptor-ligand partners that have not been fully characterized before, even with low-affinity. Results: Through our unbiased CRISPRa screen, we discovered that Myelin-Associated Glycoprotein (MAG), also known as siglec-4, a member of the siglec (sialic acid-binding immunoglobulin-like lectins) family, interacts with 4-1BB in trans. Our study demonstrated that MAG binds to activated T cells via 4-1BB and inhibits their activation and proliferation, suggesting a potential role of the MAG-4-1BB interaction in modulating T cell function. Notably, our data revealed that trans-binding to MAG-positive cells inhibits c-Jun signaling in activated T cells. Furthermore, the presence of MAG on target cells can hinder Chimeric Antigen Receptor (CAR) T-cell activity. Conclusion: Utilizing a highly efficient cell-based CRISPRa system, we discovered a novel interactor of 4-1BB capable of modulating T cell activation through its interaction with 4-1BB. This interaction suggests an immunosuppressive role of 4-1BB, explaining the paradoxical roles of 4-1BB in T cells. These findings provide crucial insights for the development of precise therapeutics targeting 4-1BB. Citation Format: Liping Yang, Timothy P. Sheets, Yang Feng, Kuo-Sheng Hsu, Guojun Yu, Steven Seaman, Pradip Bajgain, Daeho So, Jaewon Lee, Raj Chari, Brad St. Croix. 4-1BB: A double-edged sword for T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6594.

Identification of apolipoprotein B-reactive CDR3 motifs allows tracking of atherosclerosis-related memory CD4+T cells in multiple donors.

Atherosclerosis is a major pathological condition that underlies many cardiovascular diseases (CVDs). Its etiology involves breach of tolerance to self, leading to clonal expansion of autoreactive apolipoprotein B (APOB)-reactive CD4+T cells that correlates with clinical CVD. The T-cell receptor (TCR) sequences that mediate activation of APOB-specific CD4+T cells are unknown. In a previous study, we had profiled the hypervariable complementarity determining region 3 (CDR3) of CD4+T cells that respond to six immunodominant APOB epitopes in most donors. Here, we comprehensively analyze this dataset of 149,065 APOB-reactive and 199,211 non-reactive control CDR3s from six human leukocyte antigen-typed donors. We identified 672 highly expanded (frequency threshold > 1.39E-03) clones that were significantly enriched in the APOB-reactive group as compared to the controls (log10 odds ratio ≥1, Fisher's test p < 0.01). Analysis of 114,755 naïve, 91,001 central memory (TCM) and 29,839 effector memory (TEM) CDR3 sequences from the same donors revealed that APOB+ clones can be traced to the complex repertoire of unenriched blood T cells. The fraction of APOB+ clones that overlapped with memory CDR3s ranged from 2.2% to 46% (average 16.4%). This was significantly higher than their overlap with the naïve pool, which ranged from 0.7% to 2% (average 1.36%). CDR3 motif analysis with the machine learning-based in-silico tool, GLIPHs (grouping of lymphocyte interactions by paratope hotspots), identified 532 APOB+ motifs. Analysis of naïve and memory CDR3 sequences with GLIPH revealed that ~40% (209 of 532) of these APOB+ motifs were enriched in the memory pool. Network analysis with Cytoscape revealed extensive sharing of the memory-affiliated APOB+ motifs across multiple donors. We identified six motifs that were present in TCM and TEM CDR3 sequences from >80% of the donors and were highly enriched in the APOB-reactive TCR repertoire. The identified APOB-reactive expanded CD4+T cell clones and conserved motifs can be used to annotate and track human atherosclerosis-related autoreactive CD4+T cells and measure their clonal expansion.

Ozanimod-mediated remission in experimental autoimmune encephalomyelitis is associated with enhanced activity of CNS CD27low/- NK cell subset.

Ozanimod (RPC1063) is an immunomodulator that has been recently approved by the FDA (2020) for the treatment of relapsing-remitting multiple sclerosis (RRMS). It is a selective agonist of the sphingosine-1-phophate receptors 1 and 5, expressed on naïve and central memory T and B cells, as well as natural killer (NK) cells, and is involved in lymphocyte trafficking. Oral administration of ozanimod was reported to result in rapid and reversible reduction in circulating lymphocytes in multiple sclerosis (MS) patients, however, only minimal effect on NK cells was observed. In this study, we sought to investigate the effect of ozanimod on NK cells and assess whether they play any role in ozanimod-induced remission in experimental autoimmune encephalomyelitis (EAE), the animal model of MS. Active EAE induction was done in C57BL/6 female mice, followed by daily oral treatment with ozanimod (0.6mg/kg) starting at disease onset (score 1). Flow cytometry of blood and CNS was performed 24 hours after the last oral dose of ozanimod treatment in diseased mice. Histological analysis of lumbar spinal cord was performed for evaluating the level of inflammation and demyelination. Depletion of peripheral NK cells was done using anti-NK1.1 mouse antibody (mAb) at day 5 post-EAE induction. Ozanimod was effective in reducing the clinical severity of EAE and reducing the percentage of autoreactive CD4+ and CD8+ T cells along with significant inhibition of lymphocyte infiltration into the spinal cord, accompanied by reversed demyelination. Furthermore, ozanimod treatment resulted in a significant increase in the frequency of total NK cells in the blood and CNS along with upregulation of the activating receptor NKG2D on CD27low/- NK cell subset in the CNS. The effectiveness of ozanimod treatment in inhibiting the progression of the disease was reduced when NK cells were depleted using anti-NK1.1 mAb. The current study demonstrated that ozanimod treatment significantly improved clinical symptoms in EAE mice. Ozanimod and anti-NK1.1 mAb appear to function in opposition to one another. Collectively, our data suggest that ozanimod-mediated remission is associated with an increased percentage of total NK cells and CD27low/- NK cells expressing the activating receptor, NKG2D in the CNS.