Monoclonal Autoantibody Against a Cryptic Epitope on Tissue-Adherent Low-Density Lipoprotein for Molecular Imaging in Atherosclerosis.

BACKGROUND: Antibody-based constructs for molecular imaging and therapeutic delivery provide promising opportunities for the diagnosis and treatment of atherosclerosis. OBJECTIVES: The authors aimed to generate and characterize immunoglobulin (Ig)G monoclonal autoantibodies in atherosclerosis for targeting of novel molecular determinants. METHODS: The authors created hybridomas from an unimmunized low-density lipoprotein (LDL) receptor-deficient (Ldlr-/-) mouse and selected an IgG2b isotype autoantibody, LO9, for further characterization. RESULTS: LO9 reacted well with native LDL bound to immobilized matrix components and less well to oxidized LDL. LO9 binding to immobilized native LDL was not neutralized by fluid-phase native LDL, indicating an adhesion-dependent epitope. The authors localized the epitope to a 20 amino-acid peptide sequence (P5) in the globular amino-terminus of apolipoprotein B. LO9 reacted with antigen in mouse atherosclerosis and in both human stable and ruptured coronary atherosclerosis. Furthermore, in vivo near-infrared fluorescence molecular tomographic imaging, and ex vivo confocal microscopy showed that intravenously injected LO9 localized beneath endothelium of the aortic arch in Ldlr-/- mice, in the vicinity of macrophages. CONCLUSIONS: The authors believe LO9 is the first example of an IgG autoantibody that reacts with a native LDL epitope revealed by adherence to tissue matrix. Antibodies against adherent native LDL have potential as molecular targeting agents for imaging of and therapeutic delivery to atherosclerosis.

Depletion of Homeostatic Antibodies against Malondialdehyde-Modified Low-Density Lipoprotein Correlates with Adverse Events in Major Vascular Surgery.

We aimed to investigate if major vascular surgery induces LDL oxidation, and whether circulating antibodies against malondialdehyde-modified LDL (MDA-LDL) alter dynamically in this setting. We also questioned relationships between these biomarkers and post-operative cardiovascular events. Major surgery can induce an oxidative stress response. However, the role of the humoral immune system in clearance of oxidized LDL following such an insult is unknown. Plasma samples were obtained from a prospective cohort of 131 patients undergoing major non-cardiac vascular surgery, with samples obtained preoperatively and at 24- and 72 h postoperatively. Enzyme-linked immunoassays were developed to assess MDA-LDL-related antibodies and complexes. Adverse events were myocardial infarction (primary outcome), and a composite of unstable angina, stroke and all-cause mortality (secondary outcome). MDA-LDL significantly increased at 24 h post-operatively (p < 0.0001). Conversely, levels of IgG and IgM anti-MDA-LDL, as well as IgG/IgM-MDA-LDL complexes and total IgG/IgM, were significantly lower at 24 h (each p < 0.0001). A smaller decrease in IgG anti-MDA-LDL related to combined clinical adverse events in a post hoc analysis, withstanding adjustment for age, sex, and total IgG (OR 0.13, 95% CI [0.03-0.5], p < 0.001; p value for trend <0.001). Major vascular surgery resulted in an increase in plasma MDA-LDL, in parallel with a decrease in antibody/complex levels, likely due to antibody binding and subsequent removal from the circulation. Our study provides novel insight into the role of the immune system during the oxidative stress of major surgery, and suggests a homeostatic clearance role for IgG antibodies, with greater reduction relating to downstream adverse events.

Trends in Mortality From Aortic Stenosis in Europe: 2000-2017.

Background: Trends in mortality from aortic stenosis across European countries are not well-understood, especially given the significant growth in transcatheter aortic valve implantation (TAVI) in the last 10 years. Methods: Age-standardised death rates were extracted from the World Health Organisation Mortality Database, using the International Classification of Diseases 10th edition code for non-rheumatic aortic stenosis for those aged > 45 years between 2000 and 2017. The UK and countries from the European Union with at least 1,000,000 inhabitants and at least 50% available datapoints over the study period were included: a total of 23 countries. Trends were described using Joinpoint regression analysis. Results: No reductions in mortality were demonstrated across all countries 2000-2017. Large increases in mortality were found for Croatia, Poland and Slovakia for both sexes (>300% change). Mortality plateaued in Germany from 2008 in females and 2012 in males, whilst mortality in the Netherlands declined for both sexes from 2007. Mortality differences between the sexes were observed, with greater mortality for males than females across most countries. Conclusions: Mortality from aortic stenosis has increased across Europe from 2000 to 2017. There are, however, sizable differences in mortality trends between Eastern and Western European countries. The need for health resource planning strategies to specifically target AS, particularly given the expected increase with ageing populations, is highlighted.

The Placebo-Controlled Effect of Percutaneous Coronary Intervention on Exercise Induced Changes in Anti-Malondialdehyde-LDL Antibody Levels in Stable Coronary Artery Disease: A Substudy of the ORBITA Trial.

Aim: Malondialdehyde-modified low-density lipoprotein (MDA-LDL) forms a significant component of oxidised LDL. The effects of exercise on levels of MDA-LDL and anti-MDA-LDL antibodies are not well-understood. Furthermore, it is not known whether these can be modified in patients with coronary artery disease by percutaneous coronary intervention (PCI). Methods: The Objective Randomised Blinded Investigation with optimal medical Therapy of Angioplasty in stable angina (ORBITA) trial was the first blinded, multi-centre randomised trial of PCI vs. placebo procedure for angina relief. Serum samples were available at four time-points: pre-randomisation pre- (P1) and post- (P2) exercise and post-randomisation (6-weeks following the PCI or placebo procedure), pre- (P3) and post- (P4) exercise. ELISAs were performed using laboratory-developed assays for MDA-LDL (adjusted for Apolipoprotein B) and anti-MDA-LDL antibodies. Results: One hundred ninety-six of the 200 patients (age 66.1 [SD 8.99] years, 28% female) with severe single vessel coronary artery disease suitable for PCI enrolled in the ORBITA trial had blood available for analysis. With exercise at pre-randomisation (P2-P1) there was no significant change in adjusted MDA-LDL (-0.001, 95% CI -0.004 to 0.001; p = 0.287); however, IgG and IgM anti-MDA-LDL significantly declined (-0.022, 95% CI -0.029 to -0.014, p < 0.0001; -0.016, 95% CI -0.024 to -0.008, p = 0.0002, respectively). PCI did not have a significant impact on either the pre-exercise values (P3 controlling for P1) of MDA-LDL (p = 0.102), IgG (p = 0.444) or IgM anti-MDA-LDL (p = 0.909). Nor did PCI impact the exercise induced changes in these markers (P4 controlling for P1, P2, and P3) for MDA-LDL (p = 0.605), IgG (p = 0.725) or IgM anti-MDA-LDL (p = 0.171). Pre-randomisation ischaemia on stress echo did not impact these interactions. Conclusions: Exercise results in an acute reduction in anti-oxLDL antibodies in patients with severe single vessel coronary disease, possibly indicating an induction in homoeostatic clearance via the innate immune system. However, PCI did not ameliorate this effect.

A Novel Immunoassay for Malondialdehyde-Conjugated Low-Density Lipoprotein Measures Dynamic Changes in the Blood of Patients Undergoing Coronary Artery Bypass Graft Surgery.

Oxidized low-density lipoproteins play an important role in tissue pathology. In this study, we report a sensitive novel enzyme-linked immunosorbent assay for the detection of malondialdehyde-modified low-density lipoprotein (MDA-LDL), a key component of oxidized LDL. The assay is capable of measuring a variable presence of MDA-LDL within human plasma and serum. We demonstrate the robust nature of the assay on samples stored for over 20 months, as well as high inter-operator reproducibility (r = 0.74, p < 0.0001). The assay was capable of detecting dynamic changes in patient blood samples after coronary artery bypass graft surgery, indicating synthesis or release of MDA-LDL with the oxidative stress of surgery, followed by homeostatic clearance. This robust, sensitive and specific assay for circulating MDA-LDL will serve as a valuable translational tool for the improved detection of oxidative forms of LDL in response to a range of physiological or pathological stimuli, with potential clinical applicability.

Coronary Computed Tomography Angiography From Clinical Uses to Emerging Technologies: JACC State-of-the-Art Review.

Evaluation of coronary artery disease (CAD) using coronary computed tomography angiography (CCTA) has seen a paradigm shift in the last decade. Evidence increasingly supports the clinical utility of CCTA across various stages of CAD, from the detection of early subclinical disease to the assessment of acute chest pain. Additionally, CCTA can be used to noninvasively quantify plaque burden and identify high-risk plaque, aiding in diagnosis, prognosis, and treatment. This is especially important in the evaluation of CAD in immune-driven conditions with increased cardiovascular disease prevalence. Emerging applications of CCTA based on hemodynamic indices and plaque characterization may provide personalized risk assessment, affect disease detection, and further guide therapy. This review provides an update on the evidence, clinical applications, and emerging technologies surrounding CCTA as highlighted at the 2019 National Heart, Lung and Blood Institute CCTA Summit.

Vulnerable plaques and patients: state-of-the-art.

Despite advanced understanding of the biology of atherosclerosis, coronary heart disease remains the leading cause of death worldwide. Progress has been challenging as half of the individuals who suffer sudden cardiac death do not experience premonitory symptoms. Furthermore, it is well-recognized that also a plaque that does not cause a haemodynamically significant stenosis can trigger a sudden cardiac event, yet the majority of ruptured or eroded plaques remain clinically silent. In the past 30 years since the term 'vulnerable plaque' was introduced, there have been major advances in the understanding of plaque pathogenesis and pathophysiology, shifting from pursuing features of 'vulnerability' of a specific lesion to the more comprehensive goal of identifying patient 'cardiovascular vulnerability'. It has been also recognized that aside a thin-capped, lipid-rich plaque associated with plaque rupture, acute coronary syndromes (ACS) are also caused by plaque erosion underlying between 25% and 60% of ACS nowadays, by calcified nodule or by functional coronary alterations. While there have been advances in preventive strategies and in pharmacotherapy, with improved agents to reduce cholesterol, thrombosis, and inflammation, events continue to occur in patients receiving optimal medical treatment. Although at present the positive predictive value of imaging precursors of the culprit plaques remains too low for clinical relevance, improving coronary plaque imaging may be instrumental in guiding pharmacotherapy intensity and could facilitate optimal allocation of novel, more aggressive, and costly treatment strategies. Recent technical and diagnostic advances justify continuation of interdisciplinary research efforts to improve cardiovascular prognosis by both systemic and 'local' diagnostics and therapies. The present state-of-the-art document aims to present and critically appraise the latest evidence, developments, and future perspectives in detection, prevention, and treatment of 'high-risk' plaques occurring in 'vulnerable' patients.

IgM anti-malondialdehyde low density lipoprotein antibody levels indicate coronary heart disease and necrotic core characteristics in the Nordic Diltiazem (NORDIL) study and the Integrated Imaging and Biomarker Study 3 (IBIS-3).

Background: Certain immunoglobulins (Ig) are proposed to have protective functions in atherosclerosis. Objectives: We tested whether serum levels of IgG and IgM autoantibodies against malondialdehyde low density lipoprotein (MDA-LDL) are associated with clinical coronary heart disease (CHD) and unfavorable plaque characteristics. Methods: NORDIL was a prospective study investigating adverse cardiovascular outcomes in hypertensive patients. IBIS-3 analyzed lesions in a non-culprit coronary artery with <50% stenosis using radiofrequency intravascular ultrasound (RF-IVUS) and near-infrared spectroscopy (NIRS). Imaging was repeated after a median of 386?days on rosuvastatin. Associations of antibodies with incident CHD and imaging parameters were assessed in the two sub-studies respectively. Findings: From 10,881 NORDIL patients, 87 had serum sampled at baseline and developed CHD over 4.5 years, matched to 227 controls. Higher titers of IgM anti-MDA-LDL had a protective effect on adverse outcomes, with odds ratio 0.29 (0.11, 0.76; p=0.012; p=0.016 for trend). Therefore, the effect was explored at the lesional level in IBIS-3. 143 patients had blood samples and RF-IVUS measurements available, and NIRS was performed in 90 of these. At baseline, IgM anti-MDA-LDL levels had a strong independent inverse relationship with lesional necrotic core volume (p=0.027) and percentage of plaque occupied by necrotic core (p=0.011), as well as lipid core burden index (p=0.024) in the worst 4 mm segment. Interpretation: Our study supports the hypothesis that lower circulating levels of IgM anti-MDA-LDL are associated with clinical CHD development, and for the first time relates these findings to atherosclerotic plaque characteristics that are linked to vulnerability.

Developing a Strategy for Interventional Molecular Imaging of Oxidized Low-Density Lipoprotein in Atherosclerosis.

The identification of vulnerable coronary artery atherosclerotic plaques offers the prospect of either localized or systematic therapeutic targeting in order to prevent myocardial infarction. Molecular imaging of atherosclerosis adds to morphological imaging by focusing on the immunobiology hidden in and behind the endothelium and therefore may be able to improve the identification of prospective culprit lesions. Our focus has been on identifying arterial accumulation of oxidized low-density lipoprotein (oxLDL) by exploiting advances in knowledge of vascular pathobiology. Here, we reflect on our work developing near-infrared fluorescence imaging of oxLDL using LO1, a monoclonal autoantibody generated in our laboratory. We detail progress to date and discuss our vision on taking the work through the early translational pipeline toward a multitargeted approach in imaging rupture-prone atherosclerotic plaques. Ultimately, molecular imaging of coronary arteries should be able to assess the regional risk that is specific to a lesion, which can then be used in concert with global risk factors to personalize the therapeutic strategy for patients in a way that goes beyond generalized population-based therapies.

Endothelial repair in stented arteries is accelerated by inhibition of Rho-associated protein kinase.

AIMS: Stent deployment causes endothelial cells (EC) denudation, which promotes in-stent restenosis and thrombosis. Thus endothelial regrowth in stented arteries is an important therapeutic goal. Stent struts modify local hemodynamics, however the effects of flow perturbation on EC injury and repair are incompletely understood. By studying the effects of stent struts on flow and EC migration, we identified an intervention that promotes endothelial repair in stented arteries. METHODS AND RESULTS: In vitro and in vivo models were developed to monitor endothelialization under flow and the influence of stent struts. A 2D parallel-plate flow chamber with 100 µm ridges arranged perpendicular to the flow was used. Live cell imaging coupled to computational fluid dynamic simulations revealed that EC migrate in the direction of flow upstream from the ridges but subsequently accumulate downstream from ridges at sites of bidirectional flow. The mechanism of EC trapping by bidirectional flow involved reduced migratory polarity associated with altered actin dynamics. Inhibition of Rho-associated protein kinase (ROCK) enhanced endothelialization of ridged surfaces by promoting migratory polarity under bidirectional flow (P < 0.01). To more closely mimic the in vivo situation, we cultured EC on the inner surface of polydimethylsiloxane tubing containing Coroflex Blue stents (65 µm struts) and monitored migration. ROCK inhibition significantly enhanced EC accumulation downstream from struts under flow (P < 0.05). We investigated the effects of ROCK inhibition on re-endothelialization in vivo using a porcine model of EC denudation and stent placement. En face staining and confocal microscopy revealed that inhibition of ROCK using fasudil (30 mg/day via osmotic minipump) significantly increased re-endothelialization of stented carotid arteries (P < 0.05). CONCLUSIONS: Stent struts delay endothelial repair by generating localized bidirectional flow which traps migrating EC. ROCK inhibitors accelerate endothelial repair of stented arteries by enhancing EC polarity and migration through regions of bidirectional flow.

High Serum Immunoglobulin G and M Levels Predict Freedom From Adverse Cardiovascular Events in Hypertension: A Nested Case-Control Substudy of the Anglo-Scandinavian Cardiac Outcomes Trial.

AIMS: We aimed to determine whether the levels of total serum IgM and IgG, together with specific antibodies against malondialdehyde-conjugated low-density lipoprotein (MDA-LDL), can improve cardiovascular risk discrimination. METHODS AND RESULTS: The Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) randomized 9098 patients in the UK and Ireland into the Blood Pressure-Lowering Arm. 485 patients that had cardiovascular (CV) events over 5.5years were age and sex matched with 1367 controls. Higher baseline total serum IgG, and to a lesser extent IgM, were associated with decreased risk of CV events (IgG odds ratio (OR) per one standard deviation (SD) 0.80 [95% confidence interval, CI 0.72,0.89], p<0.0001; IgM 0.83[0.75,0.93], p=0.001), and particularly events due to coronary heart disease (CHD) (IgG OR 0.66 (0.57,0.76); p<0.0001, IgM OR 0.81 (0.71,0.93); p=0.002). The association persisted after adjustment for a basic model with variables in the Framingham Risk Score (FRS) as well as following inclusion of C-reactive protein (CRP) and N-terminal pro-B-type natriuretic peptide (NtProBNP). IgG and IgM antibodies against MDA-LDL were also associated with CV events but their significance was lost following adjustment for total serum IgG and IgM respectively. The area under the receiver operator curve for CV events was improved from the basic risk model when adding in total serum IgG, and there was improvement in continuous and categorical net reclassification (17.6% and 7.5% respectively) as well as in the integrated discrimination index. CONCLUSION: High total serum IgG levels are an independent predictor of freedom from adverse cardiovascular events, particularly those attributed to CHD, in patients with hypertension.

Near Infrared Fluorescence (NIRF) Molecular Imaging of Oxidized LDL with an Autoantibody in Experimental Atherosclerosis.

We aimed to develop a quantitative antibody-based near infrared fluorescence (NIRF) approach for the imaging of oxidized LDL in atherosclerosis. LO1, a well- characterized monoclonal autoantibody that reacts with malondialdehyde-conjugated LDL, was labeled with a NIRF dye to yield LO1-750. LO1-750 specifically identified necrotic core in ex vivo human coronary lesions. Injection of LO1-750 into high fat (HF) fed atherosclerotic Ldlr(-/-) mice led to specific focal localization within the aortic arch and its branches, as detected by fluorescence molecular tomography (FMT) combined with micro-computed tomography (CT). Ex vivo confocal microscopy confirmed LO1-750 subendothelial localization of LO1-750 at sites of atherosclerosis, in the vicinity of macrophages. When compared with a NIRF reporter of MMP activity (MMPSense-645-FAST), both probes produced statistically significant increases in NIRF signal in the Ldlr(-/-) model in relation to duration of HF diet. Upon withdrawing the HF diet, the reduction in oxLDL accumulation, as demonstrated with LO1-750, was less marked than the effect seen on MMP activity. In the rabbit, in vivo injected LO1-750 localization was successfully imaged ex vivo in aortic lesions with a customised intra-arterial NIRF detection catheter. A partially humanized chimeric LO1-Fab-Cys localized similarly to the parent antibody in murine atheroma showing promise for future translation.