Cardiac myosin-specific autoimmune T cells contribute to immune-checkpoint-inhibitor-associated myocarditis

The role of tumor types in immune-related adverse events

Immune checkpoint inhibitors (ICIs) are monoclonal antibodies that block inhibitors of T cell activation and function. With the widespread use of ICIs in cancer therapy, immune-related adverse events (irAEs) have gradually emerged as urgent clinical issues. Tumors not only exhibit high heterogeneity, and their response to ICIs varies, with "hot" tumors showing better anti-tumor effects but also a higher susceptibility to irAEs. The manifestation of irAEs displays a tumor-heterogeneous pattern, correlating with the tumor type in terms of the affected organs, incidence, median onset time, and severity. Understanding the mechanisms underlying the pathogenic patterns of irAEs can provide novel insights into the prevention and management of irAEs, guide the development of biomarkers, and contribute to a deeper understanding of the toxicological characteristics of ICIs. In this review, we explore the impact of tumor type on the therapeutic efficacy of ICIs and further elucidate how these tumor types influence the occurrence of irAEs. Finally, we assess key candidate biomarkers and their relevance to proposed irAE mechanisms. This paper also outlines management strategies for patients with various types of tumors, based on their disease patterns.

Insight of immune checkpoint inhibitor related myocarditis

As the understanding of immune-related mechanisms in the development and progression of cancer advances, immunotherapies, notably Immune Checkpoint Inhibitors (ICIs), have become integral in comprehensive cancer treatment strategies. ICIs reactivate T-cell cytotoxicity against tumors by blocking immune suppressive signals on T cells, such as Programmed Death-1 (PD-1) and Cytotoxic T-lymphocyte Antigen-4 (CTLA-4). Despite their beneficial effects, ICIs are associated with immune-related adverse events (irAEs), manifesting as autoimmune side effects across various organ systems. A particularly alarming irAE is life-threatening myocarditis. This rare but severe side effect of ICIs leads to significant long-term cardiac complications, including arrhythmias and heart failure, and has been observed to have a mortality rate of up to 50% in affected patients. This greatly limits the clinical application of ICI-based immunotherapy. In this review, we provide a comprehensive summary of the current knowledge regarding the diagnosis and management of ICI-related myocarditis. We also discuss the utility of preclinical mouse models in understanding and addressing this critical challenge.

Modeling immune checkpoint inhibitor associated myocarditis in vitro and its therapeutic implications

Immune checkpoint inhibitor-associated myocarditis is the most lethal side effect of immune checkpoint blockade. Myocarditis leads to persistently increased mortality and lacks effective treatments. The development of patient-relevant disease models may enable disease prediction, increased understanding of disease pathophysiology, and the development of effective treatment strategies. Here, we report a new method to model immune checkpoint inhibitor-associated myocarditis in vitro via a co-culture of activated primary human immune cells, human induced pluripotent stem cell-derived cardiomyocytes, and FDA-approved immune checkpoint inhibitors to recapitulate myocarditis in vitro. Significant cardiomyocyte necrosis, arrhythmia development, and sarcomere destruction occur, replicating clinical findings from myocarditis. This tissue culture myocarditis phenotype may rely on an induced pluripotent stem cell-derived cardiomyocyte antigen-specific CD8+ T cell response. The administration of dexamethasone rescued cardiomyocyte viability, morphology, and electrophysiology and suppressed inflammatory cytokine production. In conclusion, we detail how this platform can effectively model and provide critical information about the morphological and electrophysiological changes induced by immune checkpoint inhibitor-associated myocarditis. We have also validated the ability of this platform to screen potential medications to treat immune checkpoint inhibitor-associated myocarditis. This work establishes a robust, scalable model for identifying new therapies and risk factors, which is valuable in delineating the nature of interactions between the immune system and the heart during myocarditis.

4E-BP3 deficiency impairs dendritic cell activation and CD4+ T cell differentiation and attenuates α-myosin-specific T cell-mediated myocarditis in mice

Immune checkpoint inhibitor (ICI)-associated myocarditis is a rare but potentially fatal immune-related adverse event. Previously, we reported a case of ICI-associated myocarditis with elevated autoantibodies to 4E-binding protein 3 (4E-BP3). Recent studies have suggested that 4E-BP3 may play an important role in tumor development. However, its role in cardiac diseases including myocarditis is unknown. We investigated the role of 4E-BP3 in an autoimmune myocarditis mouse model. Myocarditis was induced in wild-type and 4E-BP3 knockout mice by immunization with murine α-myosin peptide. 4E-BP3 gene expression was upregulated in the heart of myocarditis mouse. We found that genetic deletion of 4E-BP3 attenuated myocardial inflammation, reduced fibrosis area, and improved cardiac function in myocarditis mice. Studies in bone marrow-chimeric mice demonstrated that immune cell-derived 4E-BP3 plays a pivotal role in the pathogenesis of myocarditis. Immune cell transfer experiments revealed that 4E-BP3 deficiency in dendritic cells and CD4+ T cells decreased disease severity in recipient mice. Furthermore, dendritic cells that were deficient in 4E-BP3 exhibited a diminished capacity to produce IL-6 and IL-1β. Naive CD4+ T cells lacking 4E-BP3 had a reduced ability to differentiate into T-helper (Th)1 and Th17 cells. These findings suggest that 4E-BP3 in dendritic cells and CD4+ T cells may be critically involved in the pathogenesis of α-myosin-specific T cell-mediated myocarditis. Thus, 4E-BP3 could be a possible therapeutic target for myocarditis.

Immune-Checkpoint Inhibitor-Related Myocarditis: Where We Are and Where We Will Go

Immune checkpoint inhibitors (ICIs) are specific monoclonal antibodies directed against inhibitory targets of the immune system, mainly represented by programmed death-1 (PD1) ligand-1 (PD-L1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4), thus enabling an amplified T-cell-mediated immune response against cancer cells. These drugs have significantly improved prognosis in patients with advanced metastatic cancer (e.g., melanoma, non-small cell lung cancer, renal cell carcinoma). However, uncontrolled activation of anti-tumor T-cells could trigger an excessive immune response, possibly responsible for multi-organ damage, including, among others, lymphocytic myocarditis. The incidence of ICIs-induced myocarditis is underestimated and the patients affected are poorly characterized. The diagnosis and management of this condition are mainly based on expert opinion and case reports. EKG and ultrasound are tests that can help identify patients at risk of myocarditis during treatment by red flags, such as QRS complex enlargement and narrowing of global longitudinal strain (GLS). Therapy of ICI-related myocarditis is based on immunosuppressors, monoclonal antibodies and fusion proteins. A future strategy could involve the use of microRNAs. This review considers the current state of the art of immune-related adverse cardiovascular events, focusing on histological and clinical features, diagnosis and management, including current treatments and future pharmacological targets.

Evolving therapeutics and ensuing cardiotoxicities in triple-negative breast cancer

Defined as scarce expression of hormone receptors and human epidermal growth factor receptor 2, triple-negative breast cancer (TNBC) is labeled as the most heterogeneous subtype of breast cancer with poorest prognosis. Despite rapid advancements in precise subtyping and tailored therapeutics, the ensuing cancer therapy-related cardiovascular toxicity (CTR-CVT) could exert detrimental impacts to TNBC survivors. Nowadays, this interdisciplinary issue is incrementally concerned by cardiologists, oncologists and other pertinent experts, propelling cardio-oncology as a booming field focusing on the whole-course management of cancer patients with potential cardiovascular threats. Here in this review, we initially profile the evolving molecular subtyping and therapeutic landscape of TNBC. Further, we introduce various monitoring approaches of CTR-CVT. In the main body, we elaborate on typical cardiotoxicities ensuing anti-TNBC treatments in detail, ranging from chemotherapy (especially anthracyclines), surgery, anesthetics, radiotherapy to immunotherapy, with future perspectives on promising directions in the era of artificial intelligence and traditional Chinese medicine.

Programmed death receptor-1/programmed death-ligand 1 inhibitors: Clinical progress and biomarker exploration in gastric cancer

Gastric cancer is one of the most common malignant tumours, with limited treatment options and poor prognosis in its advanced stages. In recent years, breakthroughs in tumour immunotherapy have led to immune checkpoint inhibitors becoming a new class of clinical oncology drugs. Programmed death receptor-1 (PD-1) and programmed death-ligand 1 (PD-L1) play significant roles in inhibiting T cell responses and tumour immune escape. PD-1/PD-L1 inhibitors can significantly improve the prognosis of patients with advanced gastric cancer. Moreover, the combination of administering PD-1/PD-L1 inhibitors along with chemotherapy, radiotherapy, targeted therapy, and other immunotherapies may further enhance therapeutic efficacy. However, some scientific issues need to be urgently resolved in the immunotherapy of gastric cancer, including the suboptimal efficacy of PD-1/PD-L1 inhibitor monotherapy, high incidence of immune-related adverse events, and the absence of definitive biomarkers for effectively screening treatment-sensitive populations. This article reviews the mechanism of action, therapeutic advances, adverse effects, and putative predictive biomarkers of PD-1/PD-L1 inhibitors in the treatment of advanced gastric cancer.

Injury-induced myosin-specific tissue-resident memory T cells drive immune checkpoint inhibitor myocarditis

Cardiac myosin-specific (MyHC) T cells drive the disease pathogenesis of immune checkpoint inhibitor-associated myocarditis (ICI-myocarditis). To determine whether MyHC T cells are tissue-resident memory T (TRM) cells, we characterized cardiac TRM cells in naive mice and established that they have a distinct phenotypic and transcriptional profile that can be defined by their upregulation of CD69, PD-1, and CXCR6. We then investigated the effects of cardiac injury through a modified experimental autoimmune myocarditis mouse model and an ischemia-reperfusion injury mouse model and determined that cardiac inflammation induces the recruitment of autoreactive MyHC TRM cells, which coexpress PD-1 and CD69. To investigate whether the recruited MyHC TRM cells could increase susceptibility to ICI-myocarditis, we developed a two-hit ICI-myocarditis mouse model where cardiac injury was induced, mice were allowed to recover, and then were treated with anti-PD-1 antibodies. We determined that mice who recover from cardiac injury are more susceptible to ICI-myocarditis development. We found that murine and human TRM cells share a similar location in the heart and aggregate along the perimyocardium. We phenotyped cells obtained from pericardial fluid from patients diagnosed with dilated cardiomyopathy and ischemic cardiomyopathy and established that pericardial T cells are predominantly CD69+ TRM cells that up-regulate PD-1. Finally, we determined that human pericardial macrophages produce IL-15, which supports and maintains pericardial TRM cells.

Cardiovascular toxicity in antitumor therapy: biological and therapeutic insights

The evolution of antitumor therapies has significantly improved cancer prognosis but has concurrently resulted in cardiovascular toxicities. Understanding the biological mechanisms behind these toxicities is crucial for effective management. Immunotherapy-related cardiovascular toxicities are primarily mediated by immune cells and secreted cytokines. Chemotherapy may cause cardiovascular damage through autophagy disruption and mitochondrial dysfunction. Targeted therapies can induce toxicity through endothelin-1 (ET-1) production and cardiac signaling disruption. Radiotherapy may lead to cardiomyopathy and myocardial fibrosis by affecting endothelial cells, triggering inflammatory responses and accelerating atherosclerosis. This review provides insights into these mechanisms and strategies, aiming to enhance the clinical prevention and treatment of cardiovascular toxicities.

Cardiovascular toxicities of immune therapies for cancer - a scientific statement of the Heart Failure Association (HFA) of the ESC and the ESC Council of Cardio-Oncology

The advent of immunological therapies has revolutionized the treatment of solid and haematological cancers over the last decade. Licensed therapies which activate the immune system to target cancer cells can be broadly divided into two classes. The first class are antibodies that inhibit immune checkpoint signalling, known as immune checkpoint inhibitors (ICIs). The second class are cell-based immune therapies including chimeric antigen receptor T lymphocyte (CAR-T) cell therapies, natural killer (NK) cell therapies, and tumour infiltrating lymphocyte (TIL) therapies. The clinical efficacy of all these treatments generally outweighs the risks, but there is a high rate of immune-related adverse events (irAEs), which are often unpredictable in timing with clinical sequalae ranging from mild (e.g. rash) to severe or even fatal (e.g. myocarditis, cytokine release syndrome) and reversible to permanent (e.g. endocrinopathies).The mechanisms underpinning irAE pathology vary across different irAE complications and syndromes, reflecting the broad clinical phenotypes observed and the variability of different individual immune responses, and are poorly understood overall. Immune-related cardiovascular toxicities have emerged, and our understanding has evolved from focussing initially on rare but fatal ICI-related myocarditis with cardiogenic shock to more common complications including less severe ICI-related myocarditis, pericarditis, arrhythmias, including conduction system disease and heart block, non-inflammatory heart failure, takotsubo syndrome and coronary artery disease. In this scientific statement on the cardiovascular toxicities of immune therapies for cancer, we summarize the pathophysiology, epidemiology, diagnosis, and management of ICI, CAR-T, NK, and TIL therapies. We also highlight gaps in the literature and where future research should focus.

Sintilimab-induced myocarditis suspected in a patient with esophageal cancer and followed septic shock: case report and literature review

Background

Immune checkpoint inhibitors (ICIs) have become a prevalent tool in anti-tumor therapy in recent years. They may cause immune-related adverse events (irAEs) including potentially life-threatening cardiovascular toxicities such as myocarditis.

Case presentation

In this report, we describe a 69-year-old man with recurrent esophageal cancer who developed myocarditis after receiving three cycles of sintilimab combined with nab-paclitaxel. Despite a rising cardiac troponin I (cTnI), he initially reported no discomfort. He was later suspected of having with sintilimab-induced myocarditis. Although treatment with methylprednisolone reduced his cTnI levels, he still experienced significant discomfort. Moreover, he developed pneumonia and septic shock.

Conclusion

In our literature search to identify all reported cases of sintilimab-associated adverse events involving myocarditis, we found 14 patients, including those with esophageal cancer, thymoma, lung cancer, gastric cancer, hepatobiliary carcinoma, and chordoma. The primary treatment for ICI-induced cardiotoxicity is methylprednisolone. However, the long-term or high-dose use of steroids can also induce side effects, which have not been the focus of these case reports. This is the first reported case of asymptomatic immune-mediated myocarditis occurring during the treatment of esophageal cancer with sintilimab. It is also the first to address the side effects of methylprednisolone used in the treatment of sintilimab-related myocarditis. To facilitate an early diagnosis, regular monitoring is required during sintilimab treatment. We should also focus on the prevention and management of adverse effects related to steroid use.

Global burden of myocarditis in youth and middle age (1990-2019): A systematic analysis of the disease burden and thirty-year forecast

BACKGROUND

Myocarditis is increasingly recognized as a critical health issue, particularly among youth and middle-aged populations. This study aims to analyze the global burden and trends of myocarditis in these age groups to emphasize the need for region-specific prevention and treatment strategies.

METHODS

Using data from the Global Burden of Disease (GBD) study (1990-2019), we evaluated the age-standardized rates (ASR) of myocarditis in individuals aged 10 to 54 years. We calculated average annual percentage changes (AAPC) and estimated annual percentage changes (EAPC). Additionally, we examined the correlation between myocarditis incidence and the Human Development Index (HDI) and Socio-demographic Index (SDI). Age and sex trends in myocarditis were analyzed, and Bayesian age-period-cohort (BAPC) models were used to forecast prevalence trends up to 2050.

RESULTS

The High-income Asia Pacific region had the highest ASR of myocarditis, while North Africa and the Middle East had the lowest. North Africa and the Middle East also experienced the fastest average annual growth in ASR, whereas High-income North America saw the most significant decline. Correlational analysis showed that countries with a high SDI exhibited higher myocarditis ASR. The burden of myocarditis was greater among males than females, with this disparity increasing with age. Projections indicate a stable trend in the incidence of myocarditis among the youth and middle-aged population up to 2050, although the total number of cases is expected to rise.

CONCLUSION

Our study reveals a significant upward trend in myocarditis among youth and middle-aged populations, highlighting the urgency for early monitoring and preventative strategies.

Toxicity in the era of immune checkpoint inhibitor therapy

Immune checkpoint inhibitors (ICIs) reinvigorate anti-tumor immune responses by disrupting co-inhibitory immune checkpoint molecules such as programmed cell death 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA-4). Although ICIs have had unprecedented success and have become the standard of care for many cancers, they are often accompanied by off-target inflammation that can occur in any organ system. These immune related adverse events (irAEs) often require steroid use and/or cessation of ICI therapy, which can both lead to cancer progression. Although irAEs are common, the detailed molecular and immune mechanisms underlying their development are still elusive. To further our understanding of irAEs and develop effective treatment options, there is pressing need for preclinical models recapitulating the clinical settings. In this review, we describe current preclinical models and immune implications of ICI-induced skin toxicities, colitis, neurological and endocrine toxicities, pneumonitis, arthritis, and myocarditis along with their management.

Gasdermin-E-mediated pyroptosis drives immune checkpoint inhibitor-associated myocarditis via cGAS-STING activation

Immune checkpoint inhibitor (ICI)-induced myocarditis involves intensive immune/inflammation activation; however, its molecular basis is unclear. Here, we show that gasdermin-E (GSDME), a gasdermin family member, drives ICI-induced myocarditis. Pyroptosis mediated by GSDME, but not the canonical GSDMD, is activated in myocardial tissue of mice and cancer patients with ICI-induced myocarditis. Deficiency of GSDME in male mice alleviates ICI-induced cardiac infiltration of T cells, macrophages, and monocytes, as well as mitochondrial damage and inflammation. Restoration of GSDME expression specifically in cardiomyocytes, rather than myeloid cells, in GSDME-deficient mice reproduces ICI-induced myocarditis. Mechanistically, quantitative proteomics reveal that GSDME-dependent pyroptosis promotes cell death and mitochondrial DNA release, which in turn activates cGAS-STING signaling, triggering a robust interferon response and myocardial immune/inflammation activation. Pharmacological blockade of GSDME attenuates ICI-induced myocarditis and improves long-term survival in mice. Our findings may advance the understanding of ICI-induced myocarditis and suggest that targeting the GSDME-cGAS-STING-interferon axis may help prevent and manage ICI-associated myocarditis.

Genetic factors in the pathogenesis of cardio-oncology

In recent years, with advancements in medicine, the survival period of patients with tumours has significantly increased. The adverse effects of tumour treatment on patients, especially cardiac toxicity, have become increasingly prominent. In elderly patients with breast cancer, treatment-related cardiovascular toxicity has surpassed cancer itself as the leading cause of death. Moreover, in recent years, an increasing number of novel antitumour drugs, such as multitargeted agents, antibody‒drug conjugates (ADCs), and immunotherapies, have been applied in clinical practice. The cardiotoxicity induced by these drugs has become more pronounced, leading to a complex and diverse mechanism of cardiac damage. The risks of unintended cardiovascular toxicity are increased by high-dose anthracyclines, immunotherapies, and concurrent radiation, in addition to traditional cardiovascular risk factors such as smoking, hypertension, diabetes, hyperlipidaemia, and obesity. However, these factors do not fully explain why only a subset of individuals experience treatment-related cardiac toxicity, whereas others with similar clinical features do not. Recent studies indicate that genetics play a significant role in susceptibility to the development of cardiovascular toxicity from cancer therapies. These genes are involved in drug metabolism, oxidative damage, cardiac dysfunction, and other processes. Moreover, emerging evidence suggests that epigenetics also plays a role in drug-induced cardiovascular toxicity. We conducted a review focusing on breast cancer as an example to help oncologists and cardiologists better understand the mechanisms and effects of genetic factors on cardiac toxicity. In this review, we specifically address the relationship between genetic alterations and cardiac toxicity, including chemotherapy-related genetic changes, targeted therapy-related genetic changes, and immune therapy-related genetic changes. We also discuss the role of epigenetic factors in cardiac toxicity. We hope that this review will improve the risk stratification of patients and enable therapeutic interventions that mitigate these unintended adverse consequences of life-saving cancer treatments.

Immune-checkpoint inhibitor-mediated myocarditis: CTLA4, PD1 and LAG3 in the heart

Immune-checkpoint inhibitors (ICIs) have revolutionized oncology, with nearly 50% of all patients with cancer eligible for treatment with ICIs. However, patients on ICI therapy are at risk for immune-related toxicities that can affect any organ. Inflammation of the heart muscle, known as myocarditis, resulting from ICI targeting cytotoxic T lymphocyte-associated antigen 4 (CTLA4), programmed cell death protein 1 (PD1) and PD1 ligand 1 (PDL1) is an infrequent but potentially fatal complication. ICI-mediated myocarditis (ICI-myocarditis) is a growing clinical entity given the widespread use of ICIs, its increased clinical recognition and growing use of combination ICI treatment, a well-documented risk factor for ICI-myocarditis. In this Review, we approach ICI-myocarditis from a basic and mechanistic perspective, synthesizing the recent data from both preclinical models and patient samples. We posit that mechanistic understanding of the fundamental biology of immune-checkpoint molecules may yield new insights into disease processes, which will enable improvement in diagnostic and therapeutic approaches. The syndrome of ICI-myocarditis is novel, and our understanding of immune checkpoints in the heart is in its nascency. Yet, investigations into the pathophysiology will inform better patient risk stratification, improved diagnostics and precision-based therapies for patients.

Preclinical models of cardiotoxicity from immune checkpoint inhibitor therapy

Immune checkpoint inhibitor (ICI) therapy represents a ground-breaking paradigm in cancer treatment, harnessing the immune system to combat malignancies by targeting checkpoints such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1). The use of ICI therapy generates distinctive immune-related adverse events (irAEs) including cardiovascular toxicity, necessitating targeted research efforts. This comprehensive review explores preclinical models dedicated to ICI-mediated cardiovascular complications including myocarditis. Tailored preclinical models of ICI-mediated myocardial toxicities highlight the key role of CD8+ T cells, emphasizing the profound impact of immune checkpoints on maintaining cardiac integrity. Cytokines and macrophages were identified as possible driving factors in disease progression, and at the same time, initial data on possible cardiac antigens responsible are emerging. The implications of contributing factors including thoracic radiation, autoimmune disorder, and the presence of cancer itself are increasingly understood. Besides myocarditis, mouse models unveiled an accelerated progression of atherosclerosis, adding another layer for a thorough understanding of the diverse processes involving cardiovascular immune checkpoint signalling. This review aims to discuss current preclinical models of ICI cardiotoxicity and their potential for improving enhanced risk assessment and diagnostics, offering potential targets for innovative cardioprotective strategies. Lessons from ICI therapy can drive novel approaches in cardiovascular research, extending insights to areas such as myocardial infarction and heart failure.

Molecular fingerprints of cardiovascular toxicities of immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy by unleashing the power of the immune system against malignant cells. However, their use is associated with a spectrum of adverse effects, including cardiovascular complications, which can pose significant clinical challenges. Several mechanisms contribute to cardiovascular toxicity associated with ICIs. First, the dysregulation of immune checkpoints, such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein-1 (PD-1) and its ligand (PD-L1), and molecular mimicry with cardiac autoantigens, leads to immune-related adverse events, including myocarditis and vasculitis. These events result from the aberrant activation of T cells against self-antigens within the myocardium or vascular endothelium. Second, the disruption of immune homeostasis by ICIs can lead to autoimmune-mediated inflammation of cardiac tissues, manifesting as cardiac dysfunction and heart failure, arrhythmias, or pericarditis. Furthermore, the upregulation of inflammatory cytokines, particularly tumor necrosis factor-alpha, interferon-γ, interleukin-1β, interleukin-6, and interleukin-17 contributes to cardiac and endothelial dysfunction, plaque destabilization, and thrombosis, exacerbating cardiovascular risk on the long term. Understanding the intricate mechanisms of cardiovascular side effects induced by ICIs is crucial for optimizing patient care and to ensure the safe and effective integration of immunotherapy into a broader range of cancer treatment protocols. The clinical implications of these mechanisms underscore the importance of vigilant monitoring and early detection of cardiovascular toxicity in patients receiving ICIs. Future use of these key pathological mediators as biomarkers may aid in prompt diagnosis of cardiotoxicity and will allow timely interventions.

Post-immunotherapy CTLA-4 Ig treatment improves antitumor efficacy

Immune checkpoint therapies (ICT) improve overall survival of patients with cancer but may cause immune-related adverse events (irAEs) such as myocarditis. Cytotoxic T lymphocyte-associated antigen 4 immunoglobulin fusion protein (CTLA-4 Ig), an inhibitor of T cell costimulation through CD28, reverses irAEs in animal models. However, concerns exist about potentially compromising antitumor response of ICT. In mouse tumor models, we administered CTLA-4 Ig 1) concomitantly with ICT or 2) after ICT completion. Concomitant treatment reduced antitumor efficacy, while post-ICT administration improved efficacy without affecting frequency and function of CD8 T cells. The improved response was independent of the ICT used, whether CTLA-4 or PD-1 blockade. The frequency of Tregs was significantly decreased with CTLA-4 Ig. The resulting increased CD8/Treg ratio potentially underlies the enhanced efficacy of ICT followed by CTLA-4 Ig. This paradoxical mechanism shows that a CTLA-4 Ig regimen shown to reduce irAE severity does not compromise antitumor efficacy.

Immune checkpoints in cardiac physiology and pathology: therapeutic targets for heart failure

Immune checkpoint molecules are physiological regulators of the adaptive immune response. Immune checkpoint inhibitors (ICIs), such as monoclonal antibodies targeting programmed cell death protein 1 or cytotoxic T lymphocyte-associated protein 4, have revolutionized cancer treatment and their clinical use is increasing. However, ICIs can cause various immune-related adverse events, including acute and chronic cardiotoxicity. Of these cardiovascular complications, ICI-induced acute fulminant myocarditis is the most studied, although emerging clinical and preclinical data are uncovering the importance of other ICI-related chronic cardiovascular complications, such as accelerated atherosclerosis and non-myocarditis-related heart failure. These complications could be more difficult to diagnose, given that they might only be present alongside other comorbidities. The occurrence of these complications suggests a potential role of immune checkpoint molecules in maintaining cardiovascular homeostasis, and disruption of physiological immune checkpoint signalling might thus lead to cardiac pathologies, including heart failure. Although inflammation is a long-known contributor to the development of heart failure, the therapeutic targeting of pro-inflammatory pathways has not been successful thus far. The increasingly recognized role of immune checkpoint molecules in the failing heart highlights their potential use as immunotherapeutic targets for heart failure. In this Review, we summarize the available data on ICI-induced cardiac dysfunction and heart failure, and discuss how immune checkpoint signalling is altered in the failing heart. Furthermore, we describe how pharmacological targeting of immune checkpoints could be used to treat heart failure.

Autoimmune Myocarditis, Old Dogs and New Tricks

Autoimmunity significantly contributes to the pathogenesis of myocarditis, underscored by its increased frequency in autoimmune diseases such as systemic lupus erythematosus and polymyositis. Even in cases of myocarditis caused by viral infections, dysregulated immune responses contribute to pathogenesis. However, whether triggered by existing autoimmune conditions or viral infections, the precise antigens and immunologic pathways driving myocarditis remain incompletely understood. The emergence of myocarditis associated with immune checkpoint inhibitor therapy, commonly used for treating cancer, has afforded an opportunity to understand autoimmune mechanisms in myocarditis, with autoreactive T cells specific for cardiac myosin playing a pivotal role. Despite their self-antigen recognition, cardiac myosin-specific T cells can be present in healthy individuals due to bypassing the thymic selection stage. In recent studies, novel modalities in suppressing the activity of pathogenic T cells including cardiac myosin-specific T cells have proven effective in treating autoimmune myocarditis. This review offers an overview of the current understanding of heart antigens, autoantibodies, and immune cells as the autoimmune mechanisms underlying various forms of myocarditis, along with the latest updates on clinical management and prospects for future research.

Murine MHC-Deficient Nonobese Diabetic Mice Carrying Human HLA-DQ8 Develop Severe Myocarditis and Myositis in Response to Anti-PD-1 Immune Checkpoint Inhibitor Cancer Therapy

Myocarditis has emerged as an immune-related adverse event of immune checkpoint inhibitor (ICI) cancer therapy associated with significant mortality. To ensure patients continue to safely benefit from life-saving cancer therapy, an understanding of fundamental immunological phenomena underlying ICI myocarditis is essential. We recently developed the NOD-cMHCI/II-/-.DQ8 mouse model that spontaneously develops myocarditis with lower mortality than observed in previous HLA-DQ8 NOD mouse strains. Our strain was rendered murine MHC class I and II deficient using CRISPR/Cas9 technology, making it a genetically clean platform for dissecting CD4+ T cell-mediated myocarditis in the absence of classically selected CD8+ T cells. These mice are highly susceptible to myocarditis and acute heart failure following anti-PD-1 ICI-induced treatment. Additionally, anti-PD-1 administration accelerates skeletal muscle myositis. Using histology, flow cytometry, adoptive transfers, and RNA sequencing analyses, we performed a thorough characterization of cardiac and skeletal muscle T cells, identifying shared and unique characteristics of both populations. Taken together, this report details a mouse model with features of a rare, but highly lethal clinical presentation of overlapping myocarditis and myositis following ICI therapy. This study sheds light on underlying immunological mechanisms in ICI myocarditis and provides the basis for further detailed analyses of diagnostic and therapeutic strategies.

Previous cardiovascular injury is a prerequisite for immune checkpoint inhibitor-associated lethal myocarditis in mice

AIMS

Immune checkpoint inhibitors (ICIs) are antineoplastic drugs designed to activate the immune system's response against cancer cells. Evidence suggests that they may lead to immune-related adverse events, particularly when combined (e.g., anti-CTLA-4 plus anti-PD-1), sometimes resulting in severe conditions such as myocarditis. We aimed to investigate whether a previously sustained cardiac injury, such as pathological remodelling due to hypertension, is a prerequisite for ICI therapy-induced myocarditis.

METHODS

We evaluated the cardiotoxicity of ICIs in a hypertension (HTN) mouse model (C57BL/6). Weekly doses were administered up to day 21 after the first administration. Our analysis encompassed the following parameters: (i) survival and cardiac pathological remodelling, (ii) cardiac function assessed using pressure-volume (PV)-loops, with brain natriuretic peptide (BNP) serving as a marker of haemodynamic dysfunction and (iii) cardiac inflammation (cytokine levels, infiltration, and cardiac antigen autoantibodies).

RESULTS

After the first administration of ICI combined therapy, the treated HTN group showed a 30% increased mortality (P = 0.0002) and earlier signs of hypertrophy and pathological remodelling compared with the untreated HTN group. BNP (P = 0.01) and TNF-α (<0.0001) increased 2.5- and 1.7-fold, respectively, in the treated group, while IL-6 (P = 0.8336) remained unchanged. Myocarditis only developed in the HTN group treated with ICIs on day 21 (score >3), characterised by T cell infiltration and increased cardiac antigen antibodies (86% showed a titre of 1:160). The control group treated with ICI was unaffected in any evaluated feature.

CONCLUSIONS

Our findings indicate that pre-existing sustained cardiac damage is a necessary condition for ICI-induced myocarditis.

Clinical and translational attributes of immune-related adverse events

With immune checkpoint inhibitors (ICIs) becoming the mainstay of treatment for many cancers, managing their immune-related adverse events (irAEs) has become an important part of oncological care. This Review covers the clinical presentation of irAEs and crucial aspects of reversibility, fatality and long-term sequelae, with special attention to irAEs in specific patient populations, such as those with autoimmune diseases. In addition, the genetic basis of irAEs, along with cellular and humoral responses to ICI therapy, are discussed. Detrimental effects of empirically used high-dose steroids and second-line immunosuppression, including impaired ICI effectiveness, call for more tailored irAE-treatment strategies. We discuss open therapeutic challenges and propose potential avenues to accelerate personalized management strategies and optimize outcomes.

The PD-1-PD-L1 pathway maintains an immunosuppressive environment essential for neonatal heart regeneration

The adult mouse heart responds to injury by scarring with consequent loss of contractile function, whereas the neonatal heart possesses the ability to regenerate. Activation of the immune system is among the first events upon tissue injury. It has been shown that immune response kinetics differ between regeneration and pathological remodeling, yet the underlying mechanisms of the distinct immune reactions during tissue healing remain unclear. Here we show that the immunomodulatory PD-1-PD-L1 pathway is highly active in regenerative neonatal hearts but rapidly silenced later in life. Deletion of the PD-1 receptor or inactivation of its ligand PD-L1 prevented regeneration of neonatal hearts after injury. Disruption of the pathway during neonatal cardiac injury led to increased inflammation and aberrant T cell activation, which ultimately impaired cardiac regeneration. Our findings reveal an immunomodulatory and cardioprotective role for the PD-1-PD-L1 pathway in heart regeneration and offer potential avenues for the control of adult tissue regeneration.

Bone morphogenic protein-4 availability in the cardiac microenvironment controls inflammation and fibrosis in autoimmune myocarditis

Myocarditis is an inflammatory heart disease that leads to loss of cardiomyocytes and frequently precipitates fibrotic remodeling of the myocardium, culminating in heart failure. However, the molecular mechanisms underlying immune cell control and maintenance of tissue integrity in the inflamed cardiac microenvironment remain elusive. In this study, we found that bone morphogenic protein-4 (BMP4) gradients maintain cardiac tissue homeostasis by single-cell transcriptomics analyses of inflamed murine and human myocardial tissues. Cardiac BMP pathway dysregulation was reflected by reduced BMP4 serum concentration in patients with myocarditis. Restoration of BMP signaling by antibody-mediated neutralization of the BMP inhibitors gremlin-1 and gremlin-2 ameliorated T cell-induced myocardial inflammation in mice. Moreover, progression to inflammatory cardiomyopathy was blocked through the reduction of fibrotic remodeling and preservation of cardiomyocyte integrity. These results unveil the BMP4-gremlin axis as a druggable pathway for the treatment of myocardial inflammation, limiting the severe sequelae of cardiac fibrosis and heart failure.

The inflammatory spectrum of cardiomyopathies

Infiltration of the myocardium with various cell types, cytokines and chemokines plays a crucial role in the pathogenesis of cardiomyopathies including inflammatory cardiomyopathies and myocarditis. A more comprehensive understanding of the precise immune mechanisms involved in acute and chronic myocarditis is essential to develop novel therapeutic approaches. This review offers a comprehensive overview of the current knowledge of the immune landscape in cardiomyopathies based on etiology. It identifies gaps in our knowledge about cardiac inflammation and emphasizes the need for new translational approaches to improve our understanding thus enabling development of novel early detection methods and more effective treatments.

Immune checkpoint inhibitors associated cardiovascular immune-related adverse events

Immune checkpoint inhibitors (ICIs) are specialized monoclonal antibodies (mAbs) that target immune checkpoints and their ligands, counteracting cancer cell-induced T-cell suppression. Approved ICIs like cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed death-1 (PD-1), its ligand PD-L1, and lymphocyte activation gene-3 (LAG-3) have improved cancer patient outcomes by enhancing anti-tumor responses. However, some patients are unresponsive, and others experience immune-related adverse events (irAEs), affecting organs like the lung, liver, intestine, skin and now the cardiovascular system. These cardiac irAEs include conditions like myocarditis, atherosclerosis, pericarditis, arrhythmias, and cardiomyopathy. Ongoing clinical trials investigate promising alternative co-inhibitory receptor targets, including T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) and T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT). This review delves into the mechanisms of approved ICIs (CTLA-4, PD-1, PD-L1, and LAG-3) and upcoming options like Tim-3 and TIGIT. It explores the use of ICIs in cancer treatment, supported by both preclinical and clinical data. Additionally, it examines the mechanisms behind cardiac toxic irAEs, focusing on ICI-associated myocarditis and atherosclerosis. These insights are vital as ICIs continue to revolutionize cancer therapy, offering hope to patients, while also necessitating careful monitoring and management of potential side effects, including emerging cardiac complications.

Investigation into Cardiac Myhc-α 334-352-Specific TCR Transgenic Mice Reveals a Role for Cytotoxic CD4 T Cells in the Development of Cardiac Autoimmunity

Myocarditis is one of the major causes of heart failure in children and young adults and can lead to dilated cardiomyopathy. Lymphocytic myocarditis could result from autoreactive CD4+ and CD8+ T cells, but defining antigen specificity in disease pathogenesis is challenging. To address this issue, we generated T cell receptor (TCR) transgenic (Tg) C57BL/6J mice specific to cardiac myosin heavy chain (Myhc)-α 334-352 and found that Myhc-α-specific TCRs were expressed in both CD4+ and CD8+ T cells. To investigate if the phenotype is more pronounced in a myocarditis-susceptible genetic background, we backcrossed with A/J mice. At the fourth generation of backcrossing, we observed that Tg T cells from naïve mice responded to Myhc-α 334-352, as evaluated by proliferation assay and carboxyfluorescein succinimidyl ester staining. The T cell responses included significant production of mainly pro-inflammatory cytokines, namely interferon (IFN)-γ, interleukin-17, and granulocyte macrophage-colony stimulating factor. While the naïve Tg mice had isolated myocardial lesions, immunization with Myhc-α 334-352 led to mild myocarditis, suggesting that further backcrossing to increase the percentage of A/J genome close to 99.99% might show a more severe disease phenotype. Further investigations led us to note that CD4+ T cells displayed the phenotype of cytotoxic T cells (CTLs) akin to those of conventional CD8+ CTLs, as determined by the expression of CD107a, IFN-γ, granzyme B natural killer cell receptor (NKG)2A, NKG2D, cytotoxic and regulatory T cell molecules, and eomesodermin. Taken together, the transgenic system described in this report may be a helpful tool to distinguish the roles of cytotoxic cardiac antigen-specific CD4+ T cells vs. those of CD8+ T cells in the pathogenesis of myocarditis.

Expansion of Pathogenic Cardiac Macrophages in Immune Checkpoint Inhibitor Myocarditis

BACKGROUND

Immune checkpoint inhibitors (ICIs), antibodies targeting PD-1 (programmed cell death protein 1)/PD-L1 (programmed death-ligand 1) or CTLA4 (cytotoxic T-lymphocyte-associated protein 4), have revolutionized cancer management but are associated with devastating immune-related adverse events including myocarditis. The main risk factor for ICI myocarditis is the use of combination PD-1 and CTLA4 inhibition. ICI myocarditis is often fulminant and is pathologically characterized by myocardial infiltration of T lymphocytes and macrophages. Although much has been learned about the role of T-cells in ICI myocarditis, little is understood about the identity, transcriptional diversity, and functions of infiltrating macrophages.

METHODS

We used an established murine ICI myocarditis model (Ctla4+/-Pdcd1-/- mice) to explore the cardiac immune landscape using single-cell RNA-sequencing, immunostaining, flow cytometry, in situ RNA hybridization, molecular imaging, and antibody neutralization studies.

RESULTS

We observed marked increases in CCR2 (C-C chemokine receptor type 2)+ monocyte-derived macrophages and CD8+ T-cells in this model. The macrophage compartment was heterogeneous and displayed marked enrichment in an inflammatory CCR2+ subpopulation highly expressing Cxcl9 (chemokine [C-X-C motif] ligand 9), Cxcl10 (chemokine [C-X-C motif] ligand 10), Gbp2b (interferon-induced guanylate-binding protein 2b), and Fcgr4 (Fc receptor, IgG, low affinity IV) that originated from CCR2+ monocytes. It is important that a similar macrophage population expressing CXCL9, CXCL10, and CD16α (human homologue of mouse FcgR4) was expanded in patients with ICI myocarditis. In silico prediction of cell-cell communication suggested interactions between T-cells and Cxcl9+Cxcl10+ macrophages via IFN-γ (interferon gamma) and CXCR3 (CXC chemokine receptor 3) signaling pathways. Depleting CD8+ T-cells or macrophages and blockade of IFN-γ signaling blunted the expansion of Cxcl9+Cxcl10+ macrophages in the heart and attenuated myocarditis, suggesting that this interaction was necessary for disease pathogenesis.

CONCLUSIONS

These data demonstrate that ICI myocarditis is associated with the expansion of a specific population of IFN-γ-induced inflammatory macrophages and suggest the possibility that IFN-γ blockade may be considered as a treatment option for this devastating condition.

Immunotherapy-Associated Atherosclerosis: A Comprehensive Review of Recent Findings and Implications for Future Research

Purpose of the Review

Even as immune checkpoint inhibitors (ICIs) have transformed the lifespan of many patients, they may also trigger acceleration of long-term cardiovascular disease. Our review aims to examine the current landscape of research on ICI-mediated atherosclerosis and address key questions regarding its pathogenesis and impact on patient management.

Recent Findings

Preclinical mouse models suggest that T cell dysregulation and proatherogenic cytokine production are key contributors to plaque development after checkpoint inhibition. Clinical data also highlight the significant burden of atherosclerotic cardiovascular disease (ASCVD) in patients on immunotherapy, although the value of proactively preventing and treating ASCVD in this population remains an open area of inquiry. Current treatment options include dietary/lifestyle modification and traditional medications to manage hypertension, hyperlipidemia, and diabetes risk factors; no current targeted therapies exist.

Summary

Early identification of high-risk patients is crucial for effective preventive strategies and timely intervention. Future research should focus on refining screening tools, elucidating targetable mechanisms driving ICI atherosclerosis, and evaluating long-term cardiovascular outcomes in cancer survivors who received immunotherapy. Moreover, close collaboration between oncologists and cardiologists is essential to optimize patient outcomes.

Priorities in Cardio-Oncology Basic and Translational Science: GCOS 2023 Symposium Proceedings: JACC: CardioOncology State-of-the-Art Review

Despite improvements in cancer survival, cancer therapy-related cardiovascular toxicity has risen to become a prominent clinical challenge. This has led to the growth of the burgeoning field of cardio-oncology, which aims to advance the cardiovascular health of cancer patients and survivors, through actionable and translatable science. In these Global Cardio-Oncology Symposium 2023 scientific symposium proceedings, we present a focused review on the mechanisms that contribute to common cardiovascular toxicities discussed at this meeting, the ongoing international collaborative efforts to improve patient outcomes, and the bidirectional challenges of translating basic research to clinical care. We acknowledge that there are many additional therapies that are of significance but were not topics of discussion at this symposium. We hope that through this symposium-based review we can highlight the knowledge gaps and clinical priorities to inform the design of future studies that aim to prevent and mitigate cardiovascular disease in cancer patients and survivors.

Recurrent Adrenergic Stress Provokes Persistent Myocarditis in PD-1-Deficient Mice

It is unclear how the immune system initiates effective tissue repair responses without also simultaneously activating adaptive immune responses to self-antigens released by damaged or necrotic cells. We studied the role of repetitive adrenergic mediated stress on cardiac injury wild-type and programmed death-1-deficient (PD-1-/-) mice treated with 3 intraperitoneal low doses of isoproterenol followed by an intraperitoneal injection of high-dose ISO 7 days later (ISOprimed/ISOinjury). Repetitive adrenergic stress in ISOprimed/ISOinjury PD-1-/- mice resulted in a persistent dysregulated myocardial inflammatory response characterized by the expansion of autoreactive effector CD8+ T cells, increased cardiac hypertrophy, mild left ventricular dysfunction, and increased lethality when compared with ISOprimed/ISOinjury wild-type mice.

Thymus alterations and susceptibility to immune checkpoint inhibitor myocarditis

Immune checkpoint inhibitors (ICI) have transformed the therapeutic landscape in oncology. However, ICI can induce uncommon life-threatening autoimmune T-cell-mediated myotoxicities, including myocarditis and myositis. The thymus plays a critical role in T cell maturation. Here we demonstrate that thymic alterations are associated with increased incidence and severity of ICI myotoxicities. First, using the international pharmacovigilance database VigiBase, the Assistance Publique Hôpitaux de Paris-Sorbonne University data warehouse (Paris, France) and a meta-analysis of clinical trials, we show that ICI treatment of thymic epithelial tumors (TET, and particularly thymoma) was more frequently associated with ICI myotoxicities than other ICI-treated cancers. Second, in an international ICI myocarditis registry, we established that myocarditis occurred earlier after ICI initiation in patients with TET (including active or prior history of TET) compared to other cancers and was more severe in terms of life-threatening arrythmias and concurrent myositis, leading to respiratory muscle failure and death. Lastly, we show that presence of anti-acetylcholine-receptor antibodies (a biological proxy of thymic-associated autoimmunity) was more prevalent in patients with ICI myocarditis than in ICI-treated control patients. Altogether, our results highlight that thymic alterations are associated with incidence and seriousness of ICI myotoxicities. Clinico-radio-biological workup evaluating the thymus may help in predicting ICI myotoxicities.

Immune Responses in Checkpoint Myocarditis Across Heart, Blood, and Tumor

Immune checkpoint inhibitors (ICIs) are widely used anti-cancer therapies that can cause morbid and potentially fatal immune-related adverse events (irAEs). ICI-related myocarditis (irMyocarditis) is uncommon but has the highest mortality of any irAE. The pathogenesis of irMyocarditis and its relationship to anti-tumor immunity remain poorly understood. We sought to define immune responses in heart, tumor, and blood during irMyocarditis and identify biomarkers of clinical severity by leveraging single-cell (sc)RNA-seq coupled with T cell receptor (TCR) sequencing, microscopy, and proteomics analysis of 28 irMyocarditis patients and 23 controls. Our analysis of 284,360 cells from heart and blood specimens identified cytotoxic T cells, inflammatory macrophages, conventional dendritic cells (cDCs), and fibroblasts enriched in irMyocarditis heart tissue. Additionally, potentially targetable, pro-inflammatory transcriptional programs were upregulated across multiple cell types. TCR clones enriched in heart and paired tumor tissue were largely non-overlapping, suggesting distinct T cell responses within these tissues. We also identify the presence of cardiac-expanded TCRs in a circulating, cycling CD8 T cell population as a novel peripheral biomarker of fatality. Collectively, these findings highlight critical biology driving irMyocarditis and putative biomarkers for therapeutic intervention.

Stocking the toolbox-Using preclinical models to understand the development and treatment of immune checkpoint inhibitor-induced immune-related adverse events

Cancer patients treated with immune checkpoint inhibitors (ICIs) are susceptible to a broad and variable array of immune-related adverse events (irAEs). With increasing clinical use of ICIs, defining the mechanism for irAE development is more critical than ever. However, it currently remains challenging to predict when these irAEs occur and which organ may be affected, and for many of the more severe irAEs, inaccessibility to the tissue site hampers mechanistic insight. This lack of understanding of irAE development in the clinical setting emphasizes the need for greater use of preclinical models that allow for improved prediction of biomarkers for ICI-initiated irAEs or that validate treatment options that inhibit irAEs without hampering the anti-tumor immune response. Here, we discuss the utility of preclinical models, ranging from exploring databases to in vivo animal models, focusing on where they are most useful and where they could be improved.

Mediators and mechanisms of immune checkpoint inhibitor-associated myocarditis: Insights from mouse and human

The broad application of immune checkpoint inhibitors (ICIs) has led to significant gains in cancer outcomes. By abrogating inhibitory signals, ICIs promote T cell targeting of cancer cells but can frequently trigger autoimmune manifestations, termed immune-related adverse events (irAEs), affecting essentially any organ system. Among cardiovascular irAEs, immune-related myocarditis (irMyocarditis) is the most described and carries the highest morbidity. The currently recommended treatment for irMyocarditis is potent immunosuppression with corticosteroids and other agents, but this has limited evidence basis. The cellular pathophysiology of irMyocarditis remains poorly understood, though mouse models and human data have both implicated effector CD8+ T cells, some of which are specific for the cardiomyocyte protein α-myosin. While the driving molecular signals and transcriptional programs are not well defined, the involvement of chemokine receptors such as CCR5 and CXCR3 has been proposed. Fundamental questions regarding why only approximately 1% of ICI recipients develop irMyocarditis and why irMyocarditis carries a much worse prognosis than other forms of lymphocytic myocarditis remain unanswered. Further work in both murine systems and with human samples are needed to identify better tools for diagnosis, risk-stratification, and treatment.

Risk Factors for Immune Checkpoint Inhibitor-Mediated Cardiovascular Toxicities

PURPOSE OF REVIEW

Immune checkpoint inhibitors (ICIs) have improved the field of cancer, especially in patients with advanced malignancies. Nevertheless, cardiovascular immune-related adverse events (irAEs) with high mortality and morbidity have been observed, including myocarditis, pericarditis, and vasculitis. To date, only a few clinical risk factors have been described and are currently being investigated.

RECENT FINDINGS

In this review, we address the four most prevailing risk factors for cardiovascular irAEs. ICI combination therapy is a predominant risk factor for developing ICI-mediated myocarditis. Additionally, ICI combined with other anti-cancer treatments (e.g., tyrosine kinase inhibitors, radiation, chemotherapy) seems to increase the risk of developing cardiovascular irAEs. Other risk factors include female sex, pre-existing cardiovascular disease, and specific tumors, on which we will further elaborate in this review. An a priori risk strategy to determine who is at risk to develop these cardiovascular irAEs is needed. Insights into the impact of risk factors are therefore warranted to help clinicians improve care and disease management in these patients.

Myocardial Immune Cells: The Basis of Cardiac Immunology

The mammalian heart is characterized by the presence of striated myocytes, which allow continuous rhythmic contraction from early embryonic development until the last moments of life. However, the myocardium contains a significant contingent of leukocytes from every major class. This leukocyte pool includes both resident and nonresident immune cells. Over recent decades, it has become increasingly apparent that the heart is intimately sensitive to immune signaling and that myocardial leukocytes exhibit an array of critical functions, both in homeostasis and in the context of cardiac adaptation to injury. Here, we systematically review current knowledge of all major leukocyte classes in the heart, discussing their functions in health and disease. We also highlight the connection between the myocardium, immune cells, lymphoid organs, and both local and systemic immune responses.

Expansion of Disease Specific Cardiac Macrophages in Immune Checkpoint Inhibitor Myocarditis

Background

Immune checkpoint inhibitors (ICIs), antibodies targeting PD-1/PD-L1 or CTLA4 have revolutionized cancer management but are associated with devastating immune-related adverse events (irAEs) including myocarditis. The main risk factor for ICI myocarditis is the use of combination PD-1 and CTLA4 inhibition. ICI-myocarditis is often fulminant and is pathologically characterized by myocardial infiltration of T lymphocytes and macrophages. While much has been learned regarding the role of T-cells in ICI-myocarditis, little is understood regarding the identity, transcriptional diversity, and functions of infiltrating macrophages.

Methods

We employed an established murine ICI myocarditis model ( Ctla4 +/- Pdcd1 -/- mice) to explore the cardiac immune landscape using single-cell RNA-sequencing, immunostaining, flow cytometry, in situ RNA hybridization and molecular imaging and antibody neutralization studies.

Results

We observed marked increases in CCR2 + monocyte-derived macrophages and CD8 + T-cells in this model. The macrophage compartment was heterogeneous and displayed marked enrichment in an inflammatory CCR2 + subpopulation highly expressing Cxcl9 , Cxcl10 , Gbp2b , and Fcgr4 that originated from CCR2 + monocytes. Importantly, a similar macrophage population expressing CXCL9 , CXCL10 , and CD16α (human homologue of mouse FcgR4) was found selectively expanded in patients with ICI myocarditis compared to other forms of heart failure and myocarditis. In silico prediction of cell-cell communication suggested interactions between T-cells and Cxcl9 + Cxcl10 + macrophages via IFN-γ and CXCR3 signaling pathways. Depleting CD8 + T-cells, macrophages, and blockade of IFN-γ signaling blunted the expansion of Cxcl9 + Cxcl10 + macrophages in the heart and attenuated myocarditis suggesting that this interaction was necessary for disease pathogenesis.

Conclusion

These data demonstrate that ICI-myocarditis is associated with the expansion of a specific population of IFN-γ induced inflammatory macrophages and suggest the possibility that IFN-γ blockade may be considered as a treatment option for this devastating condition.

The potential of auto-antigen-guided treatment of immune checkpoint inhibitor-mediated myocarditis

Immune checkpoint inhibitor (ICI)-mediated myocarditis is a rare but devastating side effect of cancer immunotherapy with up to 40% mortality and long-term cardiac issues such as arrhythmias and heart failure in affected patients.1 Recently, Axelrod et al.2 suggested an auto-antigen-driven mechanism as the immunological basis for this disease.

Advances in immune checkpoint inhibitors induced-cardiotoxicity

Immune checkpoint inhibitors (ICIs) are approved as the first-line drug for treating many cancers and has shown significant survival benefits; however, it also causes immune-related adverse events (irAEs) while activating the immune system, involving multiple organs. Among them, cardiovascular immune-related adverse events (CV-irAE) are rare, but common causes of death in ICIs treated cancer patients, which manifest as myocardial, pericardial, vascular and other cardiovascular toxicities. Therefore, it is important that irAEs, especially CV-irAE should be carefully recognized and monitored during the whole ICIs treatment because early detection and treatment of CV-irAE can significantly reduce the mortality of such patients. Consequently, it is urgent to fully understand the mechanism and management strategies of CV-irAE. The effects of ICIs are multifaceted and the exact mechanism of CV-irAE is still elusive. Generally, T cells identify tumor cell antigens as well as antigen in cardiomyocytes that are the same as or homologous to those on tumor cells, thus causing myocardial damage. In addition, ICIs promote formation of cardiac troponin I (cTnI) that induces cardiac dysfunction and myocardial dilatation; moreover, ICIs also increase the production of cytokines, which promote infiltration of inflammation-linked molecules into off-target tissues. Currently, the management and treatment of cardiovascular toxicity are largely dependent on glucocorticoids, more strategies for prevention and treatment of CV-irAE, such as predictive markers are being explored. This review discusses risk factors, potential pathophysiological mechanisms, clinical manifestations, and management and treatment of CV-irAE, guiding the development of more effective prevention, treatment and management strategies in the future.