Vaccinia Virus Complement Control Protein Diminishes Formation of Atherosclerotic Lesions: Complement Is Centrally Involved in Atherosclerotic Disease

Canonical and non-canonical roles of complement in atherosclerosis

Cardiovascular diseases are the leading cause of death globally, and atherosclerosis is the major contributor to the development and progression of cardiovascular diseases. Immune responses have a central role in the pathogenesis of atherosclerosis, with the complement system being an acknowledged contributor. Chronic activation of liver-derived and serum-circulating canonical complement sustains endothelial inflammation and innate immune cell activation, and deposition of complement activation fragments on inflamed endothelial cells is a hallmark of atherosclerotic plaques. However, increasing evidence indicates that liver-independent, cell-autonomous and non-canonical complement activities are underappreciated contributors to atherosclerosis. Furthermore, complement activation can also have atheroprotective properties. These specific detrimental or beneficial contributions of the complement system to the pathogenesis of atherosclerosis are dictated by the location of complement activation and engagement of its canonical versus non-canonical functions in a temporal fashion during atherosclerosis progression. In this Review, we summarize the classical and the emerging non-classical roles of the complement system in the pathogenesis of atherosclerosis and discuss potential strategies for therapeutic modulation of complement for the prevention and treatment of atherosclerotic cardiovascular disease.

The use of the vaccinia virus complement control protein (VCP) in the rat retina

The complement system is highly implicated in both the prevalence and progression of Age-Related Macular Degeneration (AMD). Complement system inhibitors therefore have potential therapeutic value in managing excessive activation of the complement pathways in retinal degenerations. The vaccinia virus complement control protein (VCP) has been shown to be effective as a complement inhibitor in neuroinflammatory models including traumatic brain injury and spinal cord injury. We aimed to investigate the potential of VCP as a therapeutic molecule for retinal degenerations. In this study, we investigated the effect, localisation and delivery of VCP to the rodent retina. Complement inhibition activity of VCP was tested using a hemolytic assay. Photoreceptor cell death, inflammation and retinal stress were assayed to determine if any retinal toxicity was induced by an intravitreal injection of VCP. The effect of VCP was investigated in a model of photo-oxidative retinal degeneration. Localisation of VCP after injection was determined using a fluorescein-tagged form of VCP, as well as immunohistochemistry. Finally, a copolymer resin (Elvax) was trialled for the slow-release delivery of VCP to the retina. We found that a dose equivalent to 20μg VCP when intravitreally injected into the rat eye did not cause any photoreceptor cell death or immune cell recruitment, but led to an increase in GFAP. In photo-oxidative damaged retinas, there were no differences in photoreceptor loss, retinal stress (Gfap) and inflammation (Ccl2 and C3) between VCP and saline-injected groups; however, Jun expression was reduced in VCP-treated retinas. After VCP was injected into the eye, it was taken up in all layers of the retina but was cleared within 1-3 hours of delivery. This study indicates that a method to sustain the delivery of VCP to the retina is necessary to further investigate the effect of VCP as a complement inhibitor for retinal degenerations.

Viral-derived complement inhibitors: current status and potential role in immunomodulation

The complement system is one of the body's major innate immune defense mechanisms in vertebrates. Its function is to detect foreign bodies and promote their elimination through opsonisation or lysis. Complement proteins play an important role in the immunopathogenesis of several disorders. However, excessive complement activation does not confer more protection but instead leads to several autoimmune and inflammatory diseases. With inappropriate activation of the complement system, activated complement proteins and glycoproteins may damage both healthy and diseased tissues. Development of complement inhibitors represents an effective approach in controlling dysregulated complement activity and reducing disease severity, yet few studies have investigated the nature and role of novel complement inhibitory proteins of viral origin. Viral complement inhibitors have important implications in understanding the importance of complement inhibition and their role as a promising novel therapeutic approach in diseases caused by dysregulated complement function. In this review, we discuss the role and importance of complement inhibitors derived from several viruses in the scope of human inflammatory and autoimmune diseases.

Application of quartz crystal microbalance with dissipation monitoring technology for studying interactions of poxviral proteins with their ligands

Poxviruses are one of the most complex of animal viruses and encode for over 150 proteins. The interactions of many of the poxviral-encoded proteins with host proteins, as well as with other proteins, such as transcription complexes, have been well characterized at the qualitative level. Some have also been characterized quantitatively by two hybrid systems and surface plasmon resonance approaches. Presented here is an alternative approach that can enable the understanding of complex interactions with multiple ligands. The example given is that of vaccinia virus complement control protein (VCP). The complement system forms the first line of defense against microorganisms and a failure to appropriately regulate it is implicated in many inflammatory disorders, such as traumatic brain injury, Alzheimer's disease (AD), and rheumatoid arthritis. The complement component C3 is central to the complement activation. Complement regulatory proteins, capable of binding to the central complement component C3, may therefore effectively be employed for the treatment and prevention of these disorders. There are many biochemical and/or immunoassays available to study the interaction of proteins with complement components. However, protocols for many of them are time consuming, and not all assays are useful for multiple screening. In addition, most of these assays may not give information regarding the nature of binding, the number of molecules interacting with the complement component C3, as well as kinetics of binding. Some of the assays may require labeling which may induce changes in protein confirmation. We report a protocol for an assay based on quartz crystal microbalance with dissipation monitoring (QCM-D) technology, which can effectively be employed to study poxviral proteins for their ability to interact with their ligand. A protocol was developed in our laboratories to study the interaction of VCP with the complement component C3 using Q-sense (D-300), equipment based on QCM-D technology. The protocol can also be used as a prototype for studying both proteins and small-sized compounds (for use as anti-poxvirals) for their ability to interact with and/or inhibit the activity of their ligands.

The role of complement in the development and manifestation of murine atherogenic inflammation: novel avenues

Atherosclerosis is a chronic progressive inflammatory disease which manifests in the arterial vascular tree. It is a major cause of cardiovascular morbidity and contributes significantly to mortality in the developed world. Triggers for this inflammatory process are elevated levels of cholesterol, bacterial infection and obesity. The immune response in atherosclerosis is essentially pro-atherogenic, leading to lipid accumulation and cellular changes within the arterial wall. Small-animal models of atherosclerosis are used to study the relevance of candidate factors (cells, genes, diets) in the development and progression of lesions. From a multidisciplinary viewpoint, there are challenges and limitations to this approach. Activation of complement determines or modifies the outcome of acute and chronic inflammation. This review dissects the role of complement in the early development as well as the progressive manifestation of murine atherosclerosis and the advances in knowledge provided by the use of specific mouse models. It gives a critical overview of existing models, analyses seemingly conflicting results obtained with complement-deficient mouse models, highlights the importance of interrelationships between pro-coagulpant activity, adipose tissue, macrophages and complement, and uncovers exciting avenues of topical research.

Complement in atherosclerosis: friend or foe?

Atherosclerosis is a chronic inflammatory disease and the complement system plays a central role in innate immunity. Increasing evidence exists that the complement system is activated within atherosclerotic plaques. However, the role of complement in atherogenesis is not fully understood. Whereas complement activation by the classic and lectin pathway may be protective by removing apoptotic cells and cell debris from atherosclerotic plaques, activation of the complement cascade by the alternative pathway and beyond the C3 convertase with formation of anaphylatoxins and the terminal complement complex may be proatherogenic and may play a role in plaque destabilization leading to its rupture and the onset of acute cardiovascular events. In this review article we present evidence for complement activation within atherosclerotic plaques and we discuss recent data derived from experimental animal models that suggest a dual role of complement in the development of the disease. In addition, we summarize the role of complement components as biomarkers for cardiovascular disease.

The Role of Immune Complexes in Atherogenesis

Atherosclerosis is now recognized as a chronic inflammatory disease and is characterized by features of inflammation at all stages of its development. It also appears to display elements of autoimmunity, and several autoantibodies including those directed against oxidized low-density lipoprotein (ox-LDL) and heat shock proteins (Hsps) have been identified in atherosclerosis. Immune complexes (ICs) may form between these antigens and autoantibodies and via Fc receptor signaling and complement activation may modulate the inflammation in atherosclerosis. Antibody isotype may direct the role that ICs play in atherogenesis, immunoglobulin G (IgG) being potentially pro-atherogenic and immunoglobulin M (IgM) playing a protective role. Therapeutic options targeting complement activation and those which are potentially Fc-receptor mediated have been investigated in animal models, though targeting Fc receptor signaling is an area that needs further investigation.

C-reactive protein-mediated vascular injury requires complement

BACKGROUND

We previously demonstrated that vascular injury-induced neointima formation is exaggerated in human C-reactive protein (CRP) transgenic (CRPtg) compared to nontransgenic (NTG) mice. We now test the hypothesis that complement is required for this effect.

METHODS AND RESULTS

CRPtg and NTG with a normal complement system versus their counterparts lacking expression of complement component 3 (C3) protein (CRPtg/C3(-/-) and NTG/C3(-/-)) underwent carotid artery ligation. Twenty-eight days later, the injured vessels in CRPtg had thicker neointimas and more immunoreactive C3 in the surrounding adventitia compared with NTG. In CRPtg/C3(-/-), there was no increase in neointimal thickness compared with NTG or NTG/C3(-/-). Decreasing human CRP blood levels through administration of a selective antisense oligonucleotide eliminated the depletion of serum C3 associated with vascular injury and reduced immunoreactive C3 in the resultant lesions. In injured vessels, C3 colocalized with F4/80 (macrophage marker), and in vitro, human CRP elicited increased expression of C3 by bone marrow-derived macrophages.

CONCLUSIONS

Human CRP exaggeration of neointima formation in injured mouse carotid arteries associates with decreased circulating C3 and increased tissue-localized C3. C3 elimination or pharmacological reduction of human CRP prevents CRP-driven exacerbation of the injury response. In the CRPtg model system, mouse C3 is essential for the effect of human CRP.

Poor 1-year outcomes after percutaneous coronary interventions in systemic lupus erythematosus: report from the National Heart, Lung, and Blood Institute Dynamic Registry

BACKGROUND

Women with systemic lupus erythematosus (SLE) have premature and accelerated atherosclerosis. Although percutaneous coronary intervention (PCI) is used frequently to treat coronary artery disease in SLE, little is known regarding PCI outcomes immediately after PCI and after discharge.

METHODS AND RESULTS

Baseline demographic, procedure-related, and adverse outcome data on consecutive patients undergoing PCI during 5 recruitment "waves" of the National Heart, Lung, and Blood Institute Dynamic Registry across 23 clinical centers were collected. SLE patients (n=28) were compared with non-SLE patients (n=3385). SLE patients were younger and more often female in comparison with non-SLE patients undergoing PCI. SLE patients were less likely than non-SLE patients to have hyperlipidemia but had a similar prevalence of hypertension, diabetes mellitus, and tobacco use. The prevalence of multivessel disease was similar between groups. Initial intervention success (by angiographic definition) was not significantly different between groups. At 1 year, SLE patients were more likely to experience a myocardial infarction (15.6% versus 4.8%, P=0.01) and more often required repeat PCI (31.3% versus 11.8%, P=0.009) than non-SLE patients, even after adjustment for important covariates.

CONCLUSIONS

SLE patients had significantly worse cardiovascular outcomes at 1 year than non-SLE patients. Even considering the small number of SLE patients, these differences were striking. Further study is warranted to explore other factors potentially accounting for this disparity, including SLE disease activity and duration, presence of hypercoagulable state, and immunosuppressive therapy.

Pentraxins, anti-pentraxin antibodies, and atherosclerosis

Atherosclerosis is a disease of the vascular wall, which predominantly affects large and medium-sized arteries. It represents a leading cause of morbidity and mortality in the Western world. In the last few decades, it has been clearly shown that immune system plays a relevant role in atherogenesis. The effectors of both innate and adaptive immunity, including immune cells, cell or soluble receptors, cytokines, chemokines, complement components or coagulation systems, and autoantibodies are able to modulate atherosclerosis. Among proteins belonging to innate immunity, the highly conserved pentraxin family, which encompass C-reactive protein (CRP), serum amyloid P (SAP), and the long pentraxin 3 (PTX3) seems to be directly involved in the induction and progression of atherosclerosis. By immunohistochemical staining, pentraxins were found within the atherosclerotic plaques where they could play a key role interacting with atherogenic-modified lipoproteins, favoring the formation of foam cells, and exerting a proinflammatory action. Pentraxin serum levels have been shown to be associated with clinical and subclinical atherosclerosis in general population. Antibodies against pentraxins have been demonstrated in patients with autoimmune diseases, but their role in atherogenesis is still controversial.

Static and dynamic contact angles of water droplet on a solid surface using molecular dynamics simulation

The present study investigates the variation of static contact angle of a water droplet in equilibrium with a solid surface in the absence of a body force and the dynamic contact angles of water droplet moving on a solid surface for different characteristic energies using the molecular dynamics simulation. With increasing characteristic energy, the static contact angle in equilibrium with a solid surface in the absence of a body force decreases because the hydrophobic surface changes its characteristics to the hydrophilic surface. In order to consider the effect of moving water droplet on the dynamic contact angles, we apply the constant acceleration to an individual oxygen and hydrogen atom. In the presence of a body force, the water droplet changes its shape with larger advancing contact angle than the receding angle. The dynamic contact angles are compared with the static contact angle in order to see the effect of the presence of a body force.

Linkage analysis of the C4A/C4B copy number variation and polymorphisms of the adjacent steroid 21-hydroxylase gene in a healthy population

Genes encoding the steroid 21-hydroxylase (CYP21A2) and the complement component C4 proteins (C4A and C4B) are located in the MHC region in a strongly linked structure named RCCX module. Previous studies found that carriers of C4B gene deficiency (C4B*Q0) have higher risk for cardiovascular diseases. A potential explanation is that lacking the C4B gene may result in altered function of the neighboring CYP21A2 gene. Therefore we sequenced the CYP21A2 gene in 96 healthy individuals to identify polymorphisms and to characterize their linkage pattern. Fifty-three variations were detected including a new one which alters the TATA-box of the gene. Only three known mutations (V281L, Q318X and R479L) associated with congenital adrenal hyperplasia, were found in 7, 2 and 1 subjects, respectively. Linkage analysis revealed that some variations exhibit strong correlation with the C4 copy number polymorphism and constituents of the MHC III region. Rare alleles of three polymorphisms were identified as components of the 8.1 ancestral haplotype. Haplotyping and family study confirmed that the variant alleles of two intronic SNPs were constituents of haplotype blocks lacking the C4B gene. These results suggest that variations of CYP21A2 gene can be involved in disease associations of the 8.1 haplotype and the C4B*Q0 genotype.

Inhibition of complement and CD14 attenuates the Escherichia coli-induced inflammatory response in porcine whole blood

The innate immune response is a double-edged sword in systemic inflammation and sepsis. Uncontrolled or inappropriate activation can damage and be lethal to the host. Several studies have investigated inhibition of downstream mediators, including tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta). Emerging evidence indicates that upstream inhibition is a better therapeutic approach for attenuating damaging immune activation. Therefore, we investigated inhibition of two central innate immune pathways, those of complement and CD14/Toll-like receptor 4 (TLR4)/myeloid differentiation protein 2 (MD-2), in a porcine in vitro model of Escherichia coli-induced inflammation. Porcine whole blood anticoagulated with lepuridin, which did not interfere with the complement system, was incubated with E. coli lipopolysaccharide (LPS) or whole bacteria. Inhibitors of complement and CD14 and thus the LPS CD14/TLR4/MD-2 receptor complex were tested to investigate the effect on the inflammatory response. A broad range of inflammatory readouts were used to monitor the effect. Anti-CD14 was found to saturate the CD14 molecule on granulocytes and completely inhibited LPS-induced proinflammatory cytokines in a dose-dependent manner. Anti-CD14 significantly reduced the levels of the E. coli-induced proinflammatory cytokines TNF-alpha and IL-1beta, but not IL-8, in a dose-dependent manner. No effect on bacterial clearance was seen. Vaccinia complement control protein and smallpox inhibitor of complement enzymes, two Orthopoxvirus-encoded complement inhibitors, completely inhibited complement activation. Furthermore, these agents almost completely inhibited the expression of wCD11R3, which is associated with CD18 as a beta2 integrin, on porcine granulocytes and decreased IL-8 levels significantly in a dose-dependent manner. As expected, complement inhibition reduced bacterial clearance. We conclude that inhibition of complement and CD14 attenuates E. coli-induced inflammation and might be used as a therapeutic regimen in gram-negative sepsis along with appropriate treatment with antibiotics.

Smoking and a complement gene polymorphism interact in promoting cardiovascular disease morbidity and mortality

We have demonstrated previously that carriers of a genotype called C4B*Q0 (silent allele of the C4B gene) have a substantially increased risk to suffer from myocardial infarction or stroke, and are selected out from the healthy elderly population. Because smoking carries a major risk for cardiovascular disease (CVD), it seemed worthwhile to study if these two factors interact. Study 1 involved 74 patients with angina pectoris (AP), 85 patients with recent acute myocardial infarction (AMI) and 112 survivors of a previous AMI and 382 controls from Iceland. Study 2 involved 233 patients with severe CVD and 274 controls from Hungary. Smoking habits were registered for each subject. The number of C4A and C4B genes was determined by phenotyping or genotyping. Compared to controls, C4B*Q0 carrier frequency was significantly higher at diagnosis in Icelandic smokers with AP (P = 0.005) and AMI (P = 0.0003) and Hungarian smokers with severe coronary artery disease (P = 0.023), while no such difference was observed in non-smoking subjects. Age-associated decrease in C4B*Q0 observed previously in two remote Caucasian populations was found, in the present study, to be associated strongly with smoking, and to already occur in smokers after age 50 years both in Iceland and Hungary. Our findings indicate that the C4B*Q0 genotype can be considered as a major covariate of smoking in precipitating the risk for AMI and associated deaths.

Candidate inhibitors of porcine complement

Therapeutic complement inhibition is a promising strategy for treatment of a number of diseases as judged from rodent studies. The species distance from rodents to humans may limit the clinical relevance of these studies. The pig is an alternative animal for studies of human diseases like sepsis and ischemia/reperfusion injury. However, available complement inhibitors for use in pigs are scarce. The aim of the present study was to investigate and compare the efficacy of selected candidate inhibitors of porcine complement in vitro for possible future application in vivo. Sera from three different pigs were each incubated with three different activators of the complement system (zymosan, heat-aggregated immunoglobulin G (HAIGG) and Escherichia coli). Three groups of complement inhibitor candidates were tested: serine protease inhibitors (FUT-175 and C1-inhibitor), monoclonal antibodies (anti-factor B (fB) and anti-factor D (fD)) and a recombinant regulatory protein (vaccinia virus complement control protein (VCP)). Read-out was the terminal C5b-9 complement complex (TCC). The serine protease inhibitors FUT-175 and C1-inhibitor dose-dependently inhibited TCC formation in zymosan-, HAIGG- and E. coli-activated porcine sera, but with different efficacy. Complete inhibition of TCC was obtained using 0.2 mg/mL FUT-175, but required 16 mg/mL of C1-inhibitor. The monoclonal anti-fB and -fD antibodies both inhibited TCC formation dose-dependently, but in different ways. Anti-fB at high dose (1 mg/mL) completely inhibited TCC formation in sera activated with zymosan and virtually completely in sera activated with HAIGG, but not in sera activated with E. coli. Anti-fD inhibited all three activators at low dose (0.05 mg/mL), and approximately 50% TCC reduction was obtained. The recombinant complement regulatory protein VCP efficiently and dose-dependently inhibited TCC formation with a complete inhibition found at 0.05 mg/mL for all three activators. All candidates tested inhibited porcine complement activation, but in different ways and to different degrees. Of the complement-specific candidates, VCP inhibited all activators completely at low doses.