Fcgamma receptor IIIA polymorphism as a risk-factor for coronary artery disease

Precision Medicine Approach for Cardiometabolic Risk Factors in Therapeutic Apheresis

Lipoprotein apheresis (LA) is currently the most powerful intervention possible to reach a maximal reduction of lipids in patients with familial hypercholesterolemia and lipoprotein(a) hyperlipidemia. Although LA is an invasive method, it has few side effects and the best results in preventing further major cardiovascular events. It has been suggested that the highly significant reduction of cardiovascular complications in patients with severe lipid disorders achieved by LA is mediated not only by the potent reduction of lipid levels but also by the removal of other proinflammatory and proatherogenic factors. Here we performed a comprehensive proteomic analysis of patients on LA treatment using intra-individually a set of differently sized apheresis filters with the INUSpheresis system. This study revealed that proteomic analysis correlates well with routine clinical chemistry in these patients. The method is eminently suited to discover new biomarkers and risk factors for cardiovascular disease in these patients. Different filters achieve reduction and removal of proatherogenic proteins in different quantities. This includes not only apolipoproteins, C-reactive protein, fibrinogen, and plasminogen but also proteins like complement factor B (CFAB), protein AMBP, afamin, and the low affinity immunoglobulin gamma Fc region receptor III-A (FcγRIIIa) among others that have been described as atherosclerosis and metabolic vascular diseases promoting factors. We therefore conclude that future trials should be designed to develop an individualized therapy approach for patients on LA based on their metabolic and vascular risk profile. Furthermore, the power of such cascade filter treatment protocols may improve the prevention of cardiometabolic disease and its complications.

FCGR2A-HH Gene Variants Encoding the Fc Gamma Receptor for the C-Reactive Protein Are Associated with Enhanced Monocyte CD32 Expression and Cardiovascular Events’ Recurrence after Primary Acute Coronary Syndrome

Fcγ receptors (FcγRs) interact with the C-reactive protein (CRP) and mediate activation of inflammation-related pathogenic mechanisms affecting cardiovascular health. Our study evaluated whether FcγRIIA and FcγRIIIA profiles are associated with the recurrence of adverse cardiovascular events during the first year after a primary acute coronary syndrome (ACS). The primary endpoint was the recurrence of cardiovascular events (RCE), identified as a composite outcome comprising acute heart failure (AHF) and major adverse cardiovascular events (MACE). We obtained blood samples of 145 ACS patients to measure hsCRP circulating levels, to identify FcγRIIA-131RH rs1801274 and FcγRIIIA-158FV rs396991 polymorphisms, to analyze circulating monocytes and NK cell subsets expressing CD16 and CD32, and to detect serum-mediated FCGR2A-HH activation by luciferase reporter assays. The hsCRP, CD32-expression, and Fc-R mediated activation levels were similar in all patients regardless of their MACE risk. In contrast, the hsCRP levels and the proportion of CD14+ circulating monocytes expressing the CD32 receptor for CRP were significantly higher in the patients who developed AHF. The FCGR2A rs1801274 HH genotype was significantly more common in patients who developed RCE and MACE than in RCE-free patients and associated with an enhanced percentage of circulating CD32+CD14+ monocytes. The FCGR2A-HH genotype was identified as an independent predictor of subsequent RCE (OR, 2.7; p = 0.048; CI, 1.01–7.44) by multivariate analysis. These findings bring preliminary evidence that host FCGR2A genetic variants can influence monocyte CD32 receptor expression and may contribute to the fine-tuning of CD32-driven chronic activating signals that affect the risk of developing RCEs following primary ACS events.

Pan-Tissue Aging Clock Genes That Have Intimate Connections with the Immune System and Age-Related Disease

In our recent transcriptomic meta-analysis, we used random forest machine learning to accurately predict age in human blood, bone, brain, heart, and retina tissues given gene inputs. Although each tissue-specific model utilized a unique number of genes for age prediction, we found that the following six genes were prioritized in all five tissues: CHI3L2, CIDEC, FCGR3A, RPS4Y1, SLC11A1, and VTCN1. Since being selected for age prediction in multiple tissues is unique, we decided to explore these pan-tissue clock genes in greater detail. In the present study, we began by performing over-representation and network topology-based enrichment analyses in the Gene Ontology Biological Process database. These analyses revealed that the immunological terms "response to protozoan," "immune response," and "positive regulation of immune system process" were significantly enriched by these clock inputs. Expression analyses in mouse and human tissues identified that these inputs are frequently upregulated or downregulated with age. A detailed literature search showed that all six genes had noteworthy connections to age-related disease. For example, mice deficient in Cidec are protected against various metabolic defects, while suppressing VTCN1 inhibits age-related cancers in mouse models. Using a large multitissue transcriptomic dataset, we additionally generate a novel, minimalistic aging clock that can predict human age using just these six genes as inputs. Taken all together, these six genes are connected to diverse aspects of aging.

Identification of Post-myocardial Infarction Blood Expression Signatures Using Multiple Feature Selection Strategies

Myocardial infarction (MI) is a type of serious heart attack in which the blood flow to the heart is suddenly interrupted, resulting in injury to the heart muscles due to a lack of oxygen supply. Although clinical diagnosis methods can be used to identify the occurrence of MI, using the changes of molecular markers or characteristic molecules in blood to characterize the early phase and later trend of MI will help us choose a more reasonable treatment plan. Previously, comparative transcriptome studies focused on finding differentially expressed genes between MI patients and healthy people. However, signature molecules altered in different phases of MI have not been well excavated. We developed a set of computational approaches integrating multiple machine learning algorithms, including Monte Carlo feature selection (MCFS), incremental feature selection (IFS), and support vector machine (SVM), to identify gene expression characteristics on different phases of MI. 134 genes were determined to serve as features for building optimal SVM classifiers to distinguish acute MI and post-MI. Subsequently, functional enrichment analyses followed by protein-protein interaction analysis on 134 genes identified several hub genes (IL1R1, TLR2, and TLR4) associated with progression of MI, which can be used as new diagnostic molecules for MI.

Genetic and Functional Profiling of CD16-Dependent Natural Killer Activation Identifies Patients at Higher Risk of Cardiac Allograft Vasculopathy

BACKGROUND

Cardiac transplantation is an effective therapy for end-stage heart failure. Because cardiac allograft vasculopathy (CAV) is the major cause of late mortality after heart transplant (HT), there is a need to identify markers that reflect inflammatory or cytotoxic immune mechanisms contributing to its onset. Noninvasive and early stratification of patients at risk remains a challenge for adapting individualized therapy. The CD16 (Fc-gamma receptor 3A [FCGR3A]) receptor was recently identified as a major determinant of antibody-mediated natural killer (NK) cell activation in HT biopsies; however, little is known about the role of CD16 in promoting allograft vasculopathy. This study aimed to investigate whether markers that reflect CD16-dependent circulating NK cell activation may identify patients at higher risk of developing CAV after HT.

METHODS

Blood samples were collected from 103 patients undergoing routine coronarography angiography for CAV diagnosis (median 5 years since HT). Genomic and phenotypic analyses of FCGR3A/CD16 Fc-receptor profiles were compared in CAV-positive (n=52) and CAV-free patients (n=51). The levels of CD16 expression and rituximab-dependent cell cytotoxic activity of peripheral NK cells in HT recipients were evaluated using a noninvasive NK-cellular humoral activation test.

RESULTS

Enhanced levels of CD16 expression and antibody-dependent NK cell cytotoxic function of HT recipients were associated with the FCGR3A-VV genotype. The frequency of the FCGR3A-VV genotype was significantly higher in the CAV⁺ group (odds ratio, 3.9; P=0.0317) than in the CAV^- group. The FCGR3A-VV genotype was identified as an independent marker correlated with the presence of CAV at the time of coronary angiography by using multivariate logistic regression models. The FCGR3A-VV genotype was also identified as a baseline-independent predictor of CAV risk (odds ratio, 4.7; P=0.023).

CONCLUSIONS

This study unravels a prominent role for the CD16-dependent NK cell activation pathway in the complex array of factors that favor the progression of transplant arteriosclerosis. It highlights the clinical potential of a noninvasive evaluation of FCGR3A/CD16 in the early stratification of CAV risk. The recognition of CD16 as a major checkpoint that controls immune surveillance may promote the design of individualized NK cell-targeted therapies to limit vascular damage in highly responsive sensitized patients.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01569334.

Fcγ Receptors in Solid Organ Transplantation

In the current era, one of the major factors limiting graft survival is chronic antibody-mediated rejection (ABMR), whilst patient survival is impacted by the effects of immunosuppression on susceptibility to infection, malignancy and atherosclerosis. IgG antibodies play a role in all of these processes, and many of their cellular effects are mediated by Fc gamma receptors (FcγRs). These surface receptors are expressed by most immune cells, including B cells, natural killer cells, dendritic cells and macrophages. Genetic variation in FCGR genes is likely to affect susceptibility to ABMR and to modulate the physiological functions of IgG. In this review, we discuss the potential role played by FcγRs in determining outcomes in solid organ transplantation, and how genetic polymorphisms in these receptors may contribute to variations in transplant outcome.

Anti-platelet drugs attenuate the expansion of circulating CD14highCD16+ monocytes under pro-inflammatory conditions

Aims

Levels of circulating CD14^highCD16⁺ monocytes increase in atherosclerotic patients and are predictive of future cardiovascular events. Platelet activation has been identified as a crucial determinant in the acquisition of a CD16⁺ phenotype by classical CD14^highCD16⁻ cells. We tested the hypothesis that anti-platelet drugs modulate the phenotype of circulating monocytes.

Methods and results

Sixty healthy subjects undergoing influenza immunization were randomly assigned to either no treatment or anti-platelet therapy, namely aspirin 300 mg or 75 mg daily, or clopidogrel (300 mg loading dose followed by 75 mg), for 48 h post-immunization (n = 15/group). Monocyte subsets, high-sensitivity C-reactive protein, pro-inflammatory cytokines, and P-selectin were measured at baseline and post-immunization. The CD14^highCD16⁺ monocyte cell count rose by 67.3% [interquartile range (IQR): 35.7/169.2; P = 0.0002 vs. baseline] in untreated participants. All anti-platelet regimes counteracted expansion of this monocytic subpopulation. Although no statistical differences were noted among the three treatments, aspirin 300 mg was the most efficacious compared with the untreated group (−12.5% change from baseline; IQR: −28.7/18.31; P = 0.001 vs. untreated). Similarly, the rise in P-selectin (17%; IQR: −5.0/39.7; P = 0.03 vs. baseline) observed in untreated participants was abolished by all treatments, with aspirin 300 mg exerting the strongest effect (−30.7%; IQR: −58.4/−0.03; P = 0.007 vs. untreated). Changes in P-selectin levels directly correlated with changes in CD14^highCD16⁺ cell count (r = 0.5; P = 0.0002). There was a similar increase among groups in high-sensitivity C-reactive protein (P < 0.03 vs. baseline levels).

Conclusions

Anti-platelet drugs exert an immunomodulatory action by counteracting CD14^highCD16⁺ monocyte increase under pro-inflammatory conditions, with this effect being dependent on the amplitude of P-selectin reduction.

Biomarkers Related to Carotid Intima-Media Thickness and Plaques in Long-Term Survivors of Ischemic Stroke

Lifestyle risk factors, inflammation and genetics play a role in the development of atherosclerosis. We therefore studied Fc gamma receptor (FcγR) polymorphisms, interleukin (IL)-10 polymorphisms and other biomarkers related to carotid intima-media thickness (cIMT) in patients with ischemic stroke at a young age. Patients were evaluated 12 years after stroke occurrence. Patients (n = 232) 49 years of age or younger with an index stroke between 1988 and 1997 were retrospectively selected. Blood samples were taken at a first follow-up 6 years after the stroke. At a second follow-up, additional arterial events were registered for 140 patients, new blood samples were taken, and measurements of cIMT and blood pressure (BP) were performed. Unadjusted logistic regression analysis showed that cIMT ≥1 mm was associated with age, male gender, additional arterial events, BP, cholesterol, sedimentation rate, haemoglobin, triglycerides, creatinine, glycolysed haemoglobin (HbA1c) and FcγRIIIB-NaII/NaII. Adjusted backward stepwise logistic regression showed significance for age (odds ratio (OR) 1.13, 95 % confidence interval (CI) 1.04 to1.23, p = 0.003), male gender (OR 4.07, 95 % CI 1.15 to 14.5, p = 0.030), HbA1c (OR 6.65, 95 % CI 1.21 to 36.5, p = 0.029) and FcγRIIIB-NaII/NaII (OR 3.94, 95 % CI 1.08 to 14.3, p = 0.037). In this long-term follow-up study of patients with ischemic stroke at a young age, FcγRIIIB-NaII/NaII was identified as a possible contributing factor for cIMT ≥1 mm together with known risk factors, such as age, male gender, systolic BP, additional arterial events and HbA1c.

Fcγ receptors and ligands and cardiovascular disease

Fcγ receptors (FcγRs) classically modulate intracellular signaling on binding of the Fc region of IgG in immune response cells. How FcγR and their ligands affect cardiovascular health and disease has been interrogated recently in both preclinical and clinical studies. The stimulation of activating FcγR in endothelial cells, vascular smooth muscle cells, and monocytes/macrophages causes a variety of cellular responses that may contribute to vascular disease pathogenesis. Stimulation of the lone inhibitory FγcR, FcγRIIB, also has adverse consequences in endothelial cells, antagonizing NO production and reparative mechanisms. In preclinical disease models, activating FcγRs promote atherosclerosis, whereas FcγRIIB is protective, and activating FcγRs also enhance thrombotic and nonthrombotic vascular occlusion. The FcγR ligand C-reactive protein (CRP) has undergone intense study. Although in rodents CRP does not affect atherosclerosis, it causes hypertension and insulin resistance and worsens myocardial infarction. Massive data have accumulated indicating an association between increases in circulating CRP and coronary heart disease in humans. However, Mendelian randomization studies reveal that CRP is not likely a disease mediator. CRP genetics and hypertension warrant further investigation. To date, studies of genetic variants of activating FcγRs are insufficient to implicate the receptors in coronary heart disease pathogenesis in humans. However, a link between FcγRIIB and human hypertension may be emerging. Further knowledge of the vascular biology of FcγR and their ligands will potentially enhance our understanding of cardiovascular disorders, particularly in patients whose greater predisposition for disease is not explained by traditional risk factors, such as individuals with autoimmune disorders.

Scavenger receptor function of mouse Fcγ receptor III contributes to progression of atherosclerosis in apolipoprotein E hyperlipidemic mice

Recent studies showed loss of CD36 or scavenger receptor-AI/II (SR-A) does not ameliorate atherosclerosis in a hyperlipidemic mouse model, suggesting receptors other than CD36 and SR-A may also contribute to atherosclerosis. In this report, we show that apolipoprotein E (apoE)-CD16 double knockout (DKO; apoE-CD16 DKO) mice have reduced atherosclerotic lesions compared with apoE knockout mice. In vivo and in vitro foam cell analyses showed apoE-CD16 DKO macrophages accumulated less neutral lipids. Reduced foam cell formation in apoE-CD16 DKO mice is not due to change in expression of CD36, SR-A, and LOX-1. This led to a hypothesis that CD16 may have scavenger receptor activity. We presented evidence that a soluble form of recombinant mouse CD16 (sCD16) bound to malondialdehyde-modified low-density lipoprotein (MDALDL), and this binding is blocked by molar excess of MDA- modified BSA and anti-MDA mAbs, suggesting CD16 specifically recognizes MDA epitopes. Interestingly, sCD16 inhibited MDALDL binding to macrophage cell line, as well as soluble forms of recombinant mouse CD36, SR-A, and LOX-1, indicating CD16 can cross-block MDALDL binding to other scavenger receptors. Anti-CD16 mAb inhibited immune complex binding to sCD16, whereas it partially inhibited MDALDL binding to sCD16, suggesting MDALDL binding site may be in close proximity to the immune complex binding site in CD16. Loss of CD16 expression resulted in reduced levels of MDALDL-induced proinflammatory cytokine expression. Finally, CD16-deficient macrophages showed reduced MDALDL-induced Syk phosphorylation. Collectively, our findings suggest scavenger receptor activity of CD16 may, in part, contribute to the progression of atherosclerosis.

The proinflammatory effect of C-reactive protein on human endothelial cells depends on the FcγRIIa genotype

INTRODUCTION

The stimulatory effects of CRP (C-reactive protein) on endothelial cells are mainly mediated via FcγRIIa. This receptor exists in two different allotypes bearing either arginine (R131) or histidine (H131) at the extracellular amino acid position 131 of the mature protein, but only FcγRIIa-R131 displays high avidity for CRP. This study investigated the role of the FcγRIIa genotype in CRP-stimulated endothelial cells.

MATERIALS AND METHODS

We tested the effects of CRP on expression of the adhesion molecules ICAM-1, VCAM-1, and E-selectin, as well as the endothelial release of pro-inflammatory molecules as a function of the FcγRIIa-genotype (FcγRIIa-H/H131, FcγRIIa-H/R131, FcγRIIa-R/R131) in HUVEC (Human Umbilical Vein Endothelial Cells). HUVEC were grouped according to their FcγRIIa status by genotyping with an allele specific nested-PCR. The expression of ICAM-1, VCAM-1, and E-selectin on HUVEC was detected by flow cytometry. The release of soluble markers (sCD40L, IL-6, IL-8, MCP-1, tPA, sP-selectin, and sVCAM-1) was measured using a multiplex assay for flow cytometry.

RESULTS AND CONCLUSIONS

CRP-stimulated expression of ICAM-1 and E-selectin was dependent on the specific FcγRIIa-genotype, with most pronounced induction in HUVEC with the FcγRIIa-R/R genotype, followed by H/R and H/H. In accordance with this finding, the supernatants of stimulated HUVEC with the R/R genotype showed significantly higher levels of tPA, MCP-1, and IL-6. Our data show that CRP stimulates the expression of adhesion molecules and the release of soluble markers by HUVEC as a function of the FcγRIIa-genotype. These findings could be relevant in the context of risk stratification in patients with cardiovascular disease.

Gene Deficiency in Activating Fcγ Receptors Influences the Macrophage Phenotypic Balance and Reduces Atherosclerosis in Mice

Immunity contributes to arterial inflammation during atherosclerosis. Oxidized low-density lipoproteins induce an autoimmune response characterized by specific antibodies and immune complexes in atherosclerotic patients. We hypothesize that specific Fcγ receptors for IgG constant region participate in atherogenesis by regulating the inflammatory state of lesional macrophages. In vivo we examined the role of activating Fcγ receptors in atherosclerosis progression using bone marrow transplantation from mice deficient in γ-chain (the common signaling subunit of activating Fcγ receptors) to hyperlipidemic mice. Hematopoietic deficiency of Fcγ receptors significantly reduced atherosclerotic lesion size, which was associated with decreased number of macrophages and T lymphocytes, and increased T regulatory cell function. Lesions of Fcγ receptor deficient mice exhibited increased plaque stability, as evidenced by higher collagen and smooth muscle cell content and decreased apoptosis. These effects were independent of changes in serum lipids and antibody response to oxidized low-density lipoproteins. Activating Fcγ receptor deficiency reduced pro-inflammatory gene expression, nuclear factor-κB activity, and M1 macrophages at the lesion site, while increasing anti-inflammatory genes and M2 macrophages. The decreased inflammation in the lesions was mirrored by a reduced number of classical inflammatory monocytes in blood. In vitro, lack of activating Fcγ receptors attenuated foam cell formation, oxidative stress and pro-inflammatory gene expression, and increased M2-associated genes in murine macrophages. Our study demonstrates that activating Fcγ receptors influence the macrophage phenotypic balance in the artery wall of atherosclerotic mice and suggests that modulation of Fcγ receptor-mediated inflammatory responses could effectively suppress atherosclerosis.

Patients with unstable angina pectoris show an increased frequency of the Fc gamma RIIa R131 allele

Patients with Systemic Lupus Erythematosus (SLE) carry an increased risk for the development of coronary artery disease (CAD). The R131 allele of the Fc gamma receptor IIa (FcγRIIa) is associated with SLE incidence and disease severity but also with CAD. Compared to stable angina pectoris (SAP) the unstable angina (UAP), as a manifestation of destabilizing CAD, is associated with increased risk of persistent instability, myocardial infarction, and death. Identification of clinically relevant determinants for unstable angina promises reduction of UAP-associated mortality in patients with SLE. We conducted a clinical study among 553 consecutive patients with stable angina pectoris (n = 330) and unstable angina pectoris (n = 223). All patients were genotyped for a frequent functional variant at position 131 of the mature FcγRIIa. UAP, but not SAP was significantly associated with the R/R131 genotype (P < 0.001). In troponin-negative patients with angina carrying the R/R131 genotype the odds ratio for suffering from UAP was 4.02 (95% confidence interval, 2.52-6.41) compared to those with non-R/R131 genotypes. In a multivariable analysis, the R/R131 genotype independently predicted the risk for development of UAP in a model adjusted for classical atherogenic risk factors. Our data imply that risk stratification of SLE- and other high risk patients with troponin-negative angina could be significantly improved by FcγRIIa genotyping.

The role of Fcγ receptors in atherosclerosis

Atherosclerosis is widely considered to be an immune-mediated process. Fcγ receptors (Fcγ Rs) contribute to the regulation of a multitude of immune and inflammatory responses and are implicated in human atherosclerotic lesions. Major cell types involved in the pathogenesis of atherosclerosis express Fcγ Rs and their proatherogenic ligands such as immune complexes and C-reactive protein, which act to activate Fcγ R signaling pathways. This review summarizes recent significant progress addressing the multifaceted roles of Fcγ Rs in atherogenesis which comes from the studies of Fcγ R-deficient animal models, clinical investigations and in vitro molecular and cellular studies. These new findings help us appreciate the emerging role of Fcγ Rs in atherosclerosis, and suggest Fcγ Rs as a potential therapeutic target for atherosclerosis.

The Fcγ receptor IIA R131H gene polymorphism is associated with endothelial function in patients with hypercholesterolaemia

OBJECTIVE

A gene polymorphism substituting arginine (R) for histidine (H) at position 131 has been described within the Fcγ receptor IIa (FcγRIIa). The R allele is associated with increased binding of CRP and enhanced activation of monocytes. FcγRIIa is also expressed on endothelial cells, and we hypothesized this polymorphism would be associated with alterations of endothelial function.

METHODS

Genomic DNA was extracted and allele-specific PCR reactions were used to determine the FcγRIIa H131R polymorphism in 78 hypercholesterolaemic subjects. Using strain gauge plethysmography, forearm blood flow (FBF) responses were determined to intra-arterial infusion of acetylcholine (ACH), for endothelium-dependent vasodilatation (EDV), to nitroprusside (NP), for endothelium-independent vasodilatation (EIV), to NG-monomethyl-l-arginine (l-NMMA), for basal NO activity, and to ACH in the presence of l-NMMA, to assess the contribution of NO release to EDV.

RESULTS

Homozygous carriers of the H allele (n=30) had significantly better EDV than homozygous carriers of the R allele (n=15), while heterozygotes showed an intermediate phenotype (n=33) (e.g. % increase of FBF to ACH 48μg/min: 527±359% in H/H versus 452±262% in H/R versus 332±413% in R/R, p=0.0012 by 2-way ANOVA). EIV and basal NO activity were not affected by genotype, and co-infusion of l-NMMA abolished the differences in EDV.

CONCLUSIONS

The R allele of the FcγRIIa polymorphism is associated with impaired EDV and reduced NO activity during endothelial cell stimulation. These data suggest that the functional effects of the FcγRIIa H131R gene polymorphism previously observed in vitro translate into clinically relevant alterations of endothelial function in vivo.

Functional and clinical consequences of Fc receptor polymorphic and copy number variants

Receptors for immunoglobulins (Fc receptors) play a central role during an immune response, as they mediate the specific recognition of antigens of almost infinite diversity by leucocytes, thereby linking the humoral and cellular components of immunity. Indeed, engagement of Fc receptors by immunoglobulins initiates a range of immunoregulatory processes that might also play a role in disease pathogenesis. In the circulation, five main types of immunoglobulins (Ig) exist - namely IgG, IgA, IgE, IgM and IgD and receptors with the ability to recognize and bind to IgG (Fc gamma receptor family), IgE (Fc epsilon RI and CD23), IgA (CD89; Fc alpha/microR) and IgM (Fc alpha/microR) have been identified and characterized. However, it is astonishing that nearly all the known human Fc receptors display extensive genetic variation with clear implications for their function, thus representing a substantial genetic risk factor for the pathogenesis of a range of chronic inflammatory disorders.

Genetic variation in Fc gamma receptor IIa and risk of coronary heart disease: negative results from two large independent populations

BACKGROUND

The role of the Fc gamma receptor IIa (Fc gamma RIIa), a receptor for C-reactive protein (CRP), the classical acute phase protein, in atherosclerosis is not yet clear. We sought to investigate the association of Fc gamma RIIa genotype with risk of coronary heart disease (CHD) in two large population-based samples.

METHODS

Fc gamma RIIa-R/H131 polymorphisms were determined in a population of 527 patients with a history of myocardial infarction and 527 age and gender matched controls drawn from a population-based MONICA- Augsburg survey. In the LURIC population, 2227 patients with angiographically proven CHD, defined as having at least one stenosis >or= 50%, were compared with 1032 individuals with stenosis <50%.

RESULTS

In both populations genotype frequencies of the Fc gamma RIIa gene did not show a significant departure from the Hardy-Weinberg equilibrium. Fc gamma RIIa R(-131) --> H genotype was not independently associated with lower risk of CHD after multivariable adjustments, neither in the MONICA population (odds ratio (OR) 1.08; 95% confidence interval (CI) 0.81 to 1.44), nor in LURIC (OR 0.96; 95% CI 0.81 to 1.14).

CONCLUSION

Our results do not confirm an independent relationship between Fc gamma RIIa genotypes and risk of CHD in these populations.

FcgammaRIIa genotype is associated with acute coronary syndromes as first manifestation of coronary artery disease

OBJECTIVE

Identification of clinically relevant determinants for acute coronary syndromes (ACS) promises reduction of ACS-associated mortality. C-reactive protein (CRP) has proved to be useful identifying people at risk for cardiovascular events. However, it is unknown whether genetic variants at Fcgamma receptor IIa (FcgammaRIIa), the main receptor for CRP, are involved in CRP-related cardiovascular risk. We evaluated the potential impact of FcgammaRIIa through a genetic association study in patients with ACS.

METHODS AND RESULTS

We conducted a genetic association study among 701 consecutive patients with first event of ACS compared to 467 patients with stable angina pectoris. All patients were genotyped for a frequent functional variant at position 131 of the mature FcgammaRIIa, where the arginine (R) allele results in an increased signal transduction upon CRP binding. In our study, the R/R131 genotype was significantly associated with ACS as the first manifestation of coronary artery disease (P=1.2x10(-9), odds ratio 2.86, 95% CI: 2.06-3.99) compared to the non-R/R131 genotype.

CONCLUSIONS

Our data show a genetic association of the FcgammaRIIa R/R131 genotype with a more frequent occurrence of ACS as the first manifestation of coronary artery disease, probably mediated via its interaction with CRP. Genotyping of this FcgammaRIIa variant could help to improve risk stratification in the course of coronary disease in the future.

Anti-CD16 autoantibodies and delayed phagocytosis of apoptotic cells in primary biliary cirrhosis

Primary biliary cirrhosis is characterized by chronic hepatic inflammation and immune mediated apoptosis of bile duct epithelial cells. Delayed macrophage phagocytosis of opsonized apoptotic cells, noted in other autoimmune diseases, may promote inflammation. Recent studies suggest serum anti-CD16 autoantibodies contribute to impaired macrophage phagocytosis by blocking complement receptor 3 (CR3) signaling via CD16. Therefore, serum anti-CD16 levels and the ability of monocyte derived macrophages from individuals with PBC to phagocytosis apoptotic cells were compared to controls. The mean level of anti-CD16 IgM autoantibodies (0.86+/-0.62 v. 0.35+/-0.22, respectively, p=0.031) was increased in PBC compared to control sera, and mean PBC phagocytosis of opsonized apoptotic cells was significantly decreased compared to controls (23.9+/-12.2% v. 43.9+/-14.4%, respectively, p=0.020). However, PBC phagocytosis of opsonized apoptotic cells was not significantly affected by the presence or absence of autologous serum (20.8+/-13.5% v. 23.9+/-12.2%, respectively, p=0.560). PBC phagocytosis of opsonized apoptotic cells inversely correlated with CD16 (and CR3) expression levels on Day 5 after culture in the presence or absence of autologous serum (r=-0.546, p=0.033 and r=-0.519, p=0.042, respectively). Phagocytosis of non-opsonized apoptotic cells did not correlate with CD16 or CR3 expression (p>0.050). In conclusion, PBC macrophage phagocytosis of opsonized apoptotic cells is impaired, irrespective of serum factors and may increase hepatic inflammation.

Anti-OxLDL IgG blocks OxLDL interaction with CD36, but promotes FcgammaR, CD32A-dependent inflammatory cell adhesion

Generation of antibodies against oxidized-low-density lipoproteins (oxLDL) during atherosclerosis could result in the formation and deposition of oxLDL immune complexes (oxLDL-IC) on the vascular endothelial cells. Inflammatory cells express scavenger receptor (SR such as CD36) and Fcgamma receptor (FcgammaR: CD32A and CD64) that can bind to oxLDL and oxLDL-IC, respectively. Hence, depending on anti-oxLDL IgG titer, circulating monocytes could adhere to endothelium to oxLDL-IC-coated vascular bed via either FcgammaR and/or CD36. In this study, we determined the relative contribution of SR and FcgammaR in mediating monocyte interaction with oxLDL-IC deposited on vascular bed. At saturating levels of anti-oxLDL IgG concentration, monocytic cells adhered to oxLDL-IC and this adhesion is completely blocked by anti-CD32A mAb. Using CHOK1-CD32A-CD36 cells expressing equal levels of CD32A and CD36, it was observed that at lower concentrations of anti-oxLDL IgG, CD32A and CD36 contribute about 75% and 25% of cell adhesion, respectively, while at higher concentrations of anti-oxLDL IgG the adhesion is completely CD32A-dependent. CD32A-dependent adhesion was further confirmed with peripheral blood monocytes and platelets that express 2- to 5-fold higher levels of CD36 compared to CD32A. Further, PBMC adhesion to oxLDL-IC-deposited endothelial cells induced secretion of pro-inflammatory chemokines, MCP-1 and IL-8. Our results demonstrate that anti-oxLDL IgG blocks oxLDL interaction with SR such as CD36, whereas oxLDL-IC formation promotes monocyte adhesion and subsequent chemokine release through FcgammaR. These findings suggest a role for FcgammaR-mediated inflammatory cell activation in the progression of atherosclerosis.

Asp92Asn polymorphism in the myeloid IgA Fc receptor is associated with myocardial infarction in two disparate populations: CARE and WOSCOPS

OBJECTIVE

Statins reduce inflammation and risk of myocardial infarction (MI). Because the myeloid IgA Fc receptor encoded by FCAR mediates inflammation, we hypothesized that the FCAR Asp92Asn polymorphism is associated with risk of MI and that this risk would be modified by pravastatin.

METHODS AND RESULTS

In the placebo arm of the Cholesterol and Recurrent Events (CARE) study, male carriers of the 92Asn allele had an adjusted hazard ratio for incident MI of 1.68 (95% CI 1.10 to 2.57); relative risk reduction by pravastatin was 69% in carriers and 12% in noncarriers (P(interaction)=0.007). In the placebo arm of the all-male West of Scotland Coronary Prevention Study (WOSCOPS), carriers had an adjusted odds ratio for incident coronary heart disease (CHD) of 1.46 (90% CI 1.05 to 2.03); for pravastatin compared with placebo treatment, the adjusted odds ratios were 0.55 (95% CI 0.32 to 0.93) in carriers and 0.65 (95% CI 0.51 to 0.83) in noncarriers (P(interaction)=0.55).

CONCLUSIONS

Carriers of 92Asn had increased risk of MI in CARE and increased odds of CHD in WOSCOPS. Pravastatin significantly reduced risk in carriers in both CARE and WOSCOPS. A genotype by treatment interaction was observed in CARE but not in WOSCOPS.

Engineering of therapeutic antibodies to minimize immunogenicity and optimize function

One of the first difficulties in developing monoclonal antibody therapeutics was the recognition that human anti-mouse antibody (HAMA) response limited the administration of murine antibodies. Creative science has lead to a number of ways to counter the immunogenicity of non-human antibodies, primarily through chimeric, humanized, de-immunized, and most recently, human-sequence therapeutic antibodies. Once therapeutic antibodies of low or no immunogenicity were available, the creativity then turned to engineering both the antigen-binding domains (e.g., affinity maturation, stability) and altering the effector functions (e.g. antibody-dependent cellular cytotoxicity, complement-dependent cellular cytotoxicity, and clearance rate).