2015 Russell Ross Memorial Lecture in Vascular Biology: Protective Autoimmunity in Atherosclerosis

IgG1 Is the Optimal Subtype for Treating Atherosclerosis by Inducing M2 Macrophage Differentiation, and Is Independent of the FcγRIIA Gene Polymorphism

In recent years, it has been established that atherosclerosis is an autoimmune disease. However, little is currently known about the role of FcγRIIA in atherosclerosis. Herein, we sought to investigate the relationship between FcγRIIA genotypes and the effectiveness of different IgG subclasses in treating atherosclerosis. We constructed and produced different subtypes of IgG and Fc-engineered antibodies. In vitro, we observed the effect of different subtypes of IgG and Fc-engineered antibodies on the differentiation of CD14⁺ monocytes from patients or healthy individuals. In vivo, Apoe^-/- mice were fed a high-fat diet (HFD) for 20 weeks and administered injections of different CVI-IgG subclasses or Fc-engineered antibodies. Flow cytometry was used to assess the polarization of monocytes and macrophages. Although CVI-IgG4 reduced the release of MCP-1 compared to the other subtypes, IgG4 did not yield an anti-inflammatory effect by induction of human monocyte and macrophage differentiation in vitro. Furthermore, genetic polymorphisms of FcγRIIA were not associated with different CVI-IgG subclasses during the treatment of atherosclerosis. In vivo, CVI-IgG1 decreased Ly6C^high monocyte differentiation and promoted M2 macrophage polarization. We also found that the secretion of IL-10 was upregulated in the CVI-IgG1-treated group, whereas V11 and GAALIE exerted no significant effect. These findings highlight that IgG1 is the optimal subtype for treating atherosclerosis, and CVI-IgG1 can induce monocyte/macrophage polarization. Overall, these results have important implications for the development of therapeutic antibodies.

Single-cell RNA-Seq reveals CVI-mAb-induced Lyve1+ M2-like macrophages reduce atherosclerotic plaque area in Apoe-/- mice

BACKGROUND

Atherosclerosis is a lipid imbalance-induced autoimmune disease. Macrophages participate in the development and progression of atherosclerosis. Although numerous studies have utilized single-cell RNA sequencing to identify the role of various macrophage phenotypes in atherosclerosis, the macrophage subpopulations that have therapeutic benefits against atherosclerosis are not fully understood.

METHODS

In this study, a single-cell RNA sequencing analysis was performed on the F4/80⁺ macrophages of apolipoprotein E-deficient (Apoe^-/-) mice on a normal diet (ND), a high-fat diet (HFD), and a high-fat diet (HFD) with collagen VI monoclonal antibodies (CVI-mAb) treatment. A population of M2-like macrophages expressing the hyaluronan receptor Lyve1 was almost exclusively detectable in Apoe^-/- mice on an HFD with CVI-mAb treatment, compared with other groups. Differential gene expression and gene ontology enrichment analyses revealed specific gene expression patterns that distinguished this macrophage subset and uncovered its functions.

RESULTS

Lyve1⁺ M2 macrophages appear to have specialized functions in lipid metabolism. Lyve1⁺ M2-like macrophages were sorted via fluorescence- activated cell sorting (FACS) and adoptively transferred to Apoe^-/- mice fed an HFD.

CONCLUSION

Our result showed that Lyve1⁺ M2 macrophages could reduce the plaque areas in Apoe^-/- mice.

Research progress on the active ingredients of traditional Chinese medicine in the intervention of atherosclerosis: A promising natural immunotherapeutic adjuvant

Atherosclerosis (AS) is a chronic inflammatory disease caused by disorders of lipid metabolism. Abnormal deposition of low-density lipoproteins in the arterial wall stimulates the activation of immune cells, including the adhesion and infiltration of monocytes, the proliferation and differentiation of macrophages and lymphocytes, and the activation of their functions. The complex interplay between immune cells coordinates the balance between pro- and anti-inflammation and plays a key role in the progression of AS. Therefore, targeting immune cell activity may lead to the development of more selective drugs with fewer side effects to treat AS without compromising host defense mechanisms. At present, an increasing number of studies have found that the active ingredients of traditional Chinese medicine (TCM) can regulate the function of immune cells in multiple ways to against AS, showing great potential for the treatment of AS and promising clinical applications. In this paper, we review the mechanisms of immune cell action in AS lesions and the potential targets and/or pathways for immune cell regulation by the active ingredients of TCM to promote the understanding of the immune system interactions of AS and provide a relevant basis for the use of active ingredients of TCM as natural adjuvants for AS immunotherapy.

Advances in immunotherapy modalities for atherosclerosis

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. Atherosclerosis is the pathological basis of atherosclerotic cardiovascular disease (ASCVD). Atherosclerosis is now understood to be a long-term immune-mediated inflammatory condition brought on by a complicated chain of factors, including endothelial dysfunction, lipid deposits in the artery wall, and monocyte-derived macrophage infiltration, in which both innate immunity and adaptive immunity play an indispensable role. Recent studies have shown that atherosclerosis can be alleviated by inducing a protective immune response through certain auto-antigens or exogenous antigens. Some clinical trials have also demonstrated that atherosclerotic is associated with the presence of immune cells and immune factors in the body. Therefore, immunotherapy is expected to be a new preventive and curative measure for atherosclerosis. In this review, we provide a summary overview of recent progress in the research of immune mechanisms of atherosclerosis and targeted therapeutic pathways.

Crosstalk between dendritic cells and T lymphocytes during atherogenesis: Focus on antigen presentation and break of tolerance

Atherosclerosis is a chronic disease resulting from an impaired lipid and immune homeostasis, where the interaction between innate and adaptive immune cells leads to the promotion of atherosclerosis-associated immune-inflammatory response. Emerging evidence has suggested that this response presents similarities to the reactivity of effector immune cells toward self-epitopes, often as a consequence of a break of tolerance. In this context, dendritic cells, a heterogeneous population of antigen presenting cells, play a key role in instructing effector T cells to react against foreign antigens and T regulatory cells to maintain tolerance against self-antigens and/or to patrol for self-reactive effector T cells. Alterations in this delicate balance appears to contribute to atherogenesis. The aim of this review is to discuss different DC subsets, and their role in atherosclerosis as well as in T cell polarization. Moreover, we will discuss how loss of T cell tolerogenic phenotype participates to the immune-inflammatory response associated to atherosclerosis and how a better understanding of these mechanisms might result in designing immunomodulatory therapies targeting DC-T cell crosstalk for the treatment of atherosclerosis-related inflammation.

Connections for Matters of the Heart: Network Medicine in Cardiovascular Diseases

Cardiovascular diseases (CVD) are diverse disorders affecting the heart and vasculature in millions of people worldwide. Like other fields, CVD research has benefitted from the deluge of multiomics biomedical data. Current CVD research focuses on disease etiologies and mechanisms, identifying disease biomarkers, developing appropriate therapies and drugs, and stratifying patients into correct disease endotypes. Systems biology offers an alternative to traditional reductionist approaches and provides impetus for a comprehensive outlook toward diseases. As a focus area, network medicine specifically aids the translational aspect of in silico research. This review discusses the approach of network medicine and its application to CVD research.

Circulating Autoantibodies Recognizing Immunodominant Epitopes From Human Apolipoprotein B Associate With Cardiometabolic Risk Factors, but Not With Atherosclerotic Disease

Rationale

Atherosclerosis is a chronic inflammatory disease of large arteries that involves an autoimmune response with autoreactive T cells and auto-antibodies recognizing Apolipoprotein B (ApoB), the core protein of low-density lipoprotein (LDL). Here, we aimed to establish a clinical association between circulating human ApoB auto-antibodies with atherosclerosis and its clinical risk factors using a novel assay to detect auto-antibodies against a pool of highly immunogenic ApoB-peptides.

Methods and Results

To detect polyclonal IgM- and IgG-antibodies recognizing ApoB, we developed a chemiluminescent sandwich ELISA with 30 ApoB peptides selected by an in silico assay for a high binding affinity to MHC-II, which cover more than 80% of known MHC-II variants in a Caucasian population. This pre-selection of immunogenic self-peptides accounted for the high variability of human MHC-II, which is fundamental to allow T cell dependent generation of IgG antibodies. We quantified levels of ApoB-autoantibodies in a clinical cohort of 307 patients that underwent coronary angiography. Plasma anti-ApoB IgG and IgM concentrations showed no differences across healthy individuals (n = 67), patients with coronary artery disease (n = 179), and patients with an acute coronary syndrome (n = 61). However, plasma levels of anti-ApoB IgG, which are considered pro-inflammatory, were significantly increased in patients with obesity (p = 0.044) and arterial hypertension (p < 0.0001). In addition, patients diagnosed with the metabolic syndrome showed significantly elevated Anti-ApoB IgG (p = 0.002). Even when normalized for total plasma IgG, anti-ApoB IgG remained highly upregulated in hypertensive patients (p < 0.0001). We observed no association with triglycerides, total cholesterol, VLDL, or LDL plasma levels. However, total and normalized anti-ApoB IgG levels negatively correlated with HDL. In contrast, total and normalized anti-ApoB IgM, that have been suggested as anti-inflammatory, were significantly lower in diabetic patients (p = 0.012) and in patients with the metabolic syndrome (p = 0.005).

Conclusion

Using a novel ELISA method to detect auto-antibodies against ApoB in humans, we show that anti-ApoB IgG associate with cardiovascular risk factors but not with the clinical appearance of atherosclerosis, suggesting that humoral immune responses against ApoB are shaped by cardiovascular risk factors but not disease status itself. This novel tool will be helpful to develop immune-based risk stratification for clinical atherosclerosis in the future.

Modulating Autoimmunity against LDL: Development of a Vaccine against Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall that leads to the build-up of occluding atherosclerotic plaques. Its clinical sequelae, myocardial infarction and stroke, represent the most frequent causes of death worldwide. Atherosclerosis is a multifactorial pathology that involves traditional risk factors and chronic low-grade inflammation in the atherosclerotic plaque and systemically. This process is accompanied by a strong autoimmune response that involves autoreactive T cells in lymph nodes and atherosclerotic plaques, as well as autoantibodies that recognize low-density lipoprotein (LDL) and its main protein component apolipoprotein B (ApoB). In the past 60 years, numerous preclinical observations have suggested that immunomodulatory vaccination with LDL, ApoB, or its peptides has the potential to specifically dampen autoimmunity, enhance tolerance to atherosclerosis-specific antigens, and protect from experimental atherosclerosis in mouse models. Here, we summarize and discuss mechanisms, challenges, and therapeutic opportunities of immunomodulatory vaccination and other strategies to enhance protective immunity in atherosclerosis.

ApoB-Specific CD4+ T Cells in Mouse and Human Atherosclerosis

Atherosclerosis is a chronic inflammatory condition of the arterial wall that leads to the formation of vessel-occluding plaques within the subintimal space of middle-sized and larger arteries. While traditionally understood as a myeloid-driven lipid-storage disease, growing evidence suggests that the accumulation of low-density lipoprotein cholesterol (LDL-C) ignites an autoimmune response with CD4+ T-helper (TH) cells that recognize self-peptides from Apolipoprotein B (ApoB), the core protein of LDL-C. These autoreactive CD4+ T cells home to the atherosclerotic plaque, clonally expand, instruct other cells in the plaque, and induce clinical plaque instability. Recent developments in detecting antigen-specific cells at the single cell level have demonstrated that ApoB-reactive CD4+ T cells exist in humans and mice. Their phenotypes and functions deviate from classical immunological concepts of distinct and terminally differentiated TH immunity. Instead, ApoB-specific CD4+ T cells have a highly plastic phenotype, can acquire several, partially opposing and mixed transcriptional programs simultaneously, and transit from one TH subset into another over time. In this review, we highlight adaptive immune mechanisms in atherosclerosis with a focus on CD4+ T cells, introduce novel technologies to detect ApoB-specific CD4+ T cells at the single cell level, and discuss the potential impact of ApoB-driven autoimmunity in atherosclerosis.

Pathogenic Autoimmunity in Atherosclerosis Evolves From Initially Protective Apolipoprotein B100-Reactive CD4+ T-Regulatory Cells

BACKGROUND

Throughout the inflammatory response that accompanies atherosclerosis, autoreactive CD4⁺ T-helper cells accumulate in the atherosclerotic plaque. Apolipoprotein B₁₀₀ (apoB), the core protein of low-density lipoprotein, is an autoantigen that drives the generation of pathogenic T-helper type 1 (T_H1) cells with proinflammatory cytokine secretion. Clinical data suggest the existence of apoB-specific CD4⁺ T cells with an atheroprotective, regulatory T cell (T_reg) phenotype in healthy individuals. Yet, the function of apoB-reactive T_regs and their relationship with pathogenic T_H1 cells remain unknown.

METHODS

To interrogate the function of autoreactive CD4⁺ T cells in atherosclerosis, we used a novel tetramer of major histocompatibility complex II to track T cells reactive to the mouse self-peptide apo B_978-993 (apoB⁺) at the single-cell level.

RESULTS

We found that apoB⁺ T cells build an oligoclonal population in lymph nodes of healthy mice that exhibit a T_reg-like transcriptome, although only 21% of all apoB⁺ T cells expressed the T_reg transcription factor FoxP3 (Forkhead Box P3) protein as detected by flow cytometry. In single-cell RNA sequencing, apoB⁺ T cells formed several clusters with mixed T_H signatures that suggested overlapping multilineage phenotypes with pro- and anti-inflammatory transcripts of T_H1, T helper cell type 2 (T_H2), and T helper cell type 17 (T_H17), and of follicular-helper T cells. ApoB⁺ T cells were increased in mice and humans with atherosclerosis and progressively converted into pathogenic T_H1/T_H17-like cells with proinflammatory properties and only a residual T_reg transcriptome. Plaque T cells that expanded during progression of atherosclerosis consistently showed a mixed T_H1/T_H17 phenotype in single-cell RNA sequencing. In addition, we observed a loss of FoxP3 in a fraction of apoB⁺ T_regs in lineage tracing of hyperlipidemic Apoe^-/- mice. In adoptive transfer experiments, converting apoB⁺ T_regs failed to protect from atherosclerosis.

CONCLUSIONS

Our results demonstrate an unexpected mixed phenotype of apoB-reactive autoimmune T cells in atherosclerosis and suggest an initially protective autoimmune response against apoB with a progressive derangement in clinical disease. These findings identify apoB autoreactive T_regs as a novel cellular target in atherosclerosis.

Elastin-Specific Autoimmunity in Smokers With Thoracic Aortic Aneurysm and Dissection is Independent of Chronic Obstructive Pulmonary Disease

Background Thoracic aortic aneurysm ( TAA ) and dissection ( TAD ) are characterized by progressive disorganization of the aortic wall matrix, including elastin, a highly immunogenic molecule. Whether acquired autoimmune responses can be detected in TAA / TAD patients who are smokers is unknown. The objectives of this study were to determine whether TAA / TAD smokers have increased T-cell responses to human elastin fragments, and to determine whether autoimmune responses in TAA / TAD smokers are dependent on chronic obstructive pulmonary disease. Methods and Results In a cross-sectional study (N=86), we examined peripheral blood CD 4⁺ T cell responses to elastin fragments in never-, former-, or current-smokers with or without TAA / TAD . CD 4⁺ T cells were co-cultured with irradiated autologous peripheral blood CD 1a⁺/ CD 14⁺ antigen presenting cells pulsed with or without elastin fragments to measure cytokine production. Baseline plasma concentration of anti-elastin antibodies and elastin-degrading enzymes (eg, matrix metalloproteinase-9, and -12, and neutrophil elastase) were measured in the same cohort. elastin fragment-specific CD 4⁺ T cell expression of interferon-γ, and anti-elastin antibodies were dependent on history of smoking in TAA / TAD patients but were independent of chronic obstructive pulmonary disease. Matrix metalloproteinase-9, and -12, and neutrophil elastase plasma concentrations were also significantly elevated in ever-smokers with TAA / TAD . Conclusions Cigarette smoke is associated with loss of self-tolerance and induction of elastin-specific autoreactive T- and B-cell responses in patients with TAA / TAD . Development of peripheral blood biomarkers to track immunity to self-antigens could be used to identify and potentially prognosticate susceptibility to TAA / TAD in smokers.

T cell subsets and functions in atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall and the primary underlying cause of cardiovascular disease. Data from in vivo imaging, cell-lineage tracing and knockout studies in mice, as well as clinical interventional studies and advanced mRNA sequencing techniques, have drawn attention to the role of T cells as critical drivers and modifiers of the pathogenesis of atherosclerosis. CD4+ T cells are commonly found in atherosclerotic plaques. A large body of evidence indicates that T helper 1 (TH1) cells have pro-atherogenic roles and regulatory T (Treg) cells have anti-atherogenic roles. However, Treg cells can become pro-atherogenic. The roles in atherosclerosis of other TH cell subsets such as TH2, TH9, TH17, TH22, follicular helper T cells and CD28null T cells, as well as other T cell subsets including CD8+ T cells and γδ T cells, are less well understood. Moreover, some T cells seem to have both pro-atherogenic and anti-atherogenic functions. In this Review, we summarize the knowledge on T cell subsets, their functions in atherosclerosis and the process of T cell homing to atherosclerotic plaques. Much of our understanding of the roles of T cells in atherosclerosis is based on findings from experimental models. Translating these findings into human disease is challenging but much needed. T cells and their specific cytokines are attractive targets for developing new preventive and therapeutic approaches including potential T cell-related therapies for atherosclerosis.

Immunity and Inflammation in Atherosclerosis

There is now overwhelming experimental and clinical evidence that atherosclerosis is a chronic inflammatory disease. Lessons from genome-wide association studies, advanced in vivo imaging techniques, transgenic lineage tracing mice, and clinical interventional studies have shown that both innate and adaptive immune mechanisms can accelerate or curb atherosclerosis. Here, we summarize and discuss the pathogenesis of atherosclerosis with a focus on adaptive immunity. We discuss some limitations of animal models and the need for models that are tailored to better translate to human atherosclerosis and ultimately progress in prevention and treatment.

Anti-inflammatory Therapies for Cardiovascular Disease: Signaling Pathways and Mechanisms

Cardiovascular diseases (CVD) are the clinical manifestation of atherosclerosis, a chronic inflammatory disease promoted by several risk factors such as dyslipidemia, type 2 diabetes mellitus, hypertension, and smoking. Acute CVD events are the result of an unresolved inflammatory chronic state that promotes the rupture of unstable plaque lesions. Of note, the existing intensive therapies modify risk factors but do not prevent life-threatening recurrent ischemic events in high-risk patients, who have a residual inflammatory risk displayed by increased C-reactive protein (CRP) levels. Better understanding of the role of innate and adaptive immunity in plaque development and rupture has led to intensive investigation of anti-inflammatory strategies for CVD. Some of them are being tested in specific clinical trials and use lower doses of existing medications originally developed for other inflammatory diseases such as rheumatoid arthritis and psoriasis, which have high CVD risk. Other investigations are retrospective and meta-analyses of existing clinical trials that evaluate the incidence of CVD in these inflammatory diseases. Others are based on preclinical testing such as vaccines. In this article, we summarize the main anti-inflammatory strategies and associated molecular mechanisms that are being evaluated in preclinical or clinical CVD studies.

[Immunity and inflammation in atherosclerosis]

There is now overwhelming experimental and clinical evidence that arteriosclerosis is a chronic inflammatory disease. Lessons learned from genome-wide association studies, advanced in vivo imaging techniques, transgenic lineage tracing mice models and clinical interventional studies have shown that both innate and adaptive immune mechanisms can accelerate or curb arteriosclerosis. This article summarizes and discusses the pathogenesis of arteriosclerosis with a focus on the role of the adaptive immune system. Some limitations of animal models are discussed and the need for models that are tailored to better translate to human atherosclerosis and ultimately progress in prevention and treatment are emphasized.

Vaccination against atherosclerosis

Atherosclerosis is a chronic inflammatory disease that causes most heart attacks and strokes, making it the biggest killer in the world. Although cholesterol-lowering drugs have dramatically reduced these major adverse cardiovascular events, there remains a high residual risk called inflammatory risk. Atherosclerosis has an autoimmune component that can be manipulated by immunologic approaches including vaccination. Vaccination is attractive, because it is antigen-specific, does not impair host defense, and provides long-term protection. Several candidate antigens for atherosclerosis vaccine development have been identified and have been shown to reduce atherosclerosis in animal models. In this review, we focus on two different types of atherosclerosis vaccines: antibody-inducing and regulatory T cell-inducing.

Peptide serum markers in islet autoantibody-positive children

AIMS/HYPOTHESIS

We sought to identify minimal sets of serum peptide signatures as markers for islet autoimmunity and predictors of progression rates to clinical type 1 diabetes in a case-control study.

METHODS

A double cross-validation approach was applied to first prioritise peptides from a shotgun proteomic approach in 45 islet autoantibody-positive and -negative children from the BABYDIAB/BABYDIET birth cohorts. Targeted proteomics for 82 discriminating peptides were then applied to samples from another 140 children from these cohorts.

RESULTS

A total of 41 peptides (26 proteins) enriched for the functional category lipid metabolism were significantly different between islet autoantibody-positive and autoantibody-negative children. Two peptides (from apolipoprotein M and apolipoprotein C-IV) were sufficient to discriminate autoantibody-positive from autoantibody-negative children. Hepatocyte growth factor activator, complement factor H, ceruloplasmin and age predicted progression time to type 1 diabetes with a significant improvement compared with age alone.

CONCLUSION/INTERPRETATION

Distinct peptide signatures indicate islet autoimmunity prior to the clinical manifestation of type 1 diabetes and enable refined staging of the presymptomatic disease period.