Mouse cytomegalovirus antigenic immune stimulation is sufficient to aggravate atherosclerosis in hypercholesterolemic mice

Inflammation in HIV and Its Impact on Atherosclerotic Cardiovascular Disease

People living with HIV have a 1.5- to 2-fold increased risk of developing cardiovascular disease. Despite treatment with highly effective antiretroviral therapy, people living with HIV have chronic inflammation that makes them susceptible to multiple comorbidities. Several factors, including the HIV reservoir, coinfections, clonal hematopoiesis of indeterminate potential (CHIP), microbial translocation, and antiretroviral therapy, may contribute to the chronic state of inflammation. Within the innate immune system, macrophages harbor latent HIV and are among the prominent immune cells present in atheroma during the progression of atherosclerosis. They secrete inflammatory cytokines such as IL (interleukin)-6 and tumor necrosis-α that stimulate the expression of adhesion molecules on the endothelium. This leads to the recruitment of other immune cells, including cluster of differentiation (CD)8+ and CD4+ T cells, also present in early and late atheroma. As such, cells of the innate and adaptive immune systems contribute to both systemic inflammation and vascular inflammation. On a molecular level, HIV-1 primes the NLRP3 (NLR family pyrin domain containing 3) inflammasome, leading to an increased expression of IL-1β, which is important for cardiovascular outcomes. Moreover, activation of TLRs (toll-like receptors) by HIV, gut microbes, and substance abuse further activates the NLRP3 inflammasome pathway. Finally, HIV proteins such as Nef (negative regulatory factor) can inhibit cholesterol efflux in monocytes and macrophages through direct action on the cholesterol transporter ABCA1 (ATP-binding cassette transporter A1), which promotes the formation of foam cells and the progression of atherosclerotic plaque. Here, we summarize the stages of atherosclerosis in the context of HIV, highlighting the effects of HIV, coinfections, and antiretroviral therapy on cells of the innate and adaptive immune system and describe current and future interventions to reduce residual inflammation and improve cardiovascular outcomes among people living with HIV.

Atherosclerosis by Virus Infection—A Short Review

Atherosclerosis manifests by the thickening of artery walls and their narrowed channels through the accumulation of plaque. It is one of the most important indicators of cardiovascular disease. It can be caused by various factors, such as smoking, a high cholesterol diet, hypertension, hyperglycemia, and genetic factors. However, atherosclerosis can also develop due to infection. It has been reported that some bacteria and viruses can cause the development of atherosclerosis. Examples of these viruses are influenza viruses, herpes viruses, hepatitis viruses, or papillomaviruses, which are all prevalent and eminent globally for infecting the population worldwide. Moreover, many patients with coronavirus disease 2019 (COVID-19) showed symptoms of cardiovascular disease. In this review paper, the viruses linked to the development of atherosclerosis are introduced, and their viral characteristics, the mechanisms of the development of atherosclerosis, and the current vaccines and antiviral treatment methods are summarized.

Viruses, periodontitis, and comorbidities

Seminal studies published in the 1990s and 2000s explored connections between periodontal diseases and systemic conditions, revealing potential contributions of periodontal diseases in the initiation or worsening of systemic conditions. The resulting field of periodontal medicine led to the publication of studies indicating that periodontal diseases can influence the risk of systemic conditions, including adverse pregnancy outcomes, cardiovascular and respiratory diseases, as well as Alzheimer disease and cancers. In general, these studies hypothesized that the periodontal bacterial insult and/or the associated proinflammatory cascade could contribute to the pathogenesis of these systemic diseases. While investigations of the biological basis of the connections between periodontal diseases and systemic conditions generally emphasized the bacteriome, it is also biologically plausible, under an analogous hypothesis, that other types of organisms may have a similar role. Human viruses would be logical "suspects" in this role, given their ubiquity in the oral cavity, association with periodontal diseases, and ability to elicit strong inflammatory response, compromise immune responses, and synergize with bacteria in favor of a more pathogenic microbial consortium. In this review, the current knowledge of the role of viruses in connecting periodontal diseases and systemic conditions is examined. We will also delve into the mechanistic basis for such connections and highlight the importance of those relationships in the management and treatment of patients.

Productive Cytomegalovirus Infection Is Associated With Impaired Endothelial Function in ST-Elevation Myocardial Infarction

BACKGROUND

An association between productive cytomegalovirus infection and atherosclerosis was shown recently in several trials, including a previous study of ours. However, the mechanism involved in this association is still under investigation. Here, we addressed the interaction between productive cytomegalovirus infection and endothelial function in patients with ST-elevation myocardial infarction (STEMI).

METHODS

We analyzed the presence of cytomegaloviral DNA in plasma and endothelial function in 33 patients with STEMI and 33 volunteers without cardiovascular diseases, using real-time polymerase chain reaction (PCR) and a noninvasive test of flow-mediated dilation.

RESULTS

Both the frequency of presence and the load of cytomegaloviral DNA were higher in plasma of patients with STEMI than those in controls. This difference was independent of other cardiovascular risk factors (7.38 [1.36-40.07]; P = 0.02). The results of the flow-mediated dilation test were lower in patients in STEMI than in controls (5.0% [2.65%-3.09%] vs 12. %5 [7.5%-15.15%]; P = 0.004) and correlated negatively with the cytomegaloviral DNA load (Spearman R = -0.407; P = 0.019) independently of other cardiovascular risk factors.

CONCLUSIONS

Productive cytomegalovirus infection in patients with STEMI correlated negatively with endothelial function independently of other cardiovascular risk factors. The impact of cytomegalovirus on endothelial function may explain the role of cytomegalovirus in cardiovascular prognosis.

Lytic viral replication and immunopathology in a cytomegalovirus-induced mouse model of secondary hemophagocytic lymphohistiocytosis

Background

Hemophagocytic lymphohistiocytosis (HLH) is a rare immunological disorder caused by unbridled activation of T cells and macrophages, culminating in a life-threatening cytokine storm. A genetic and acquired subtype are distinguished, termed primary and secondary HLH, respectively. Clinical manifestations of both forms are frequently preceded by a viral infection, predominantly with herpesviruses. The exact role of the viral infection in the development of the hemophagocytic syndrome remains to be further elucidated.

Methods

We utilized a recently developed murine model of cytomegalovirus-associated secondary HLH and dissected the respective contributions of lytic viral replication and immunopathology in its pathogenesis.

Results

HLH-like disease only developed in cytomegalovirus-susceptible mouse strains unable to clear the virus, but the severity of symptoms was not correlated to the infectious viral titer. Lytic viral replication and sustained viremia played an essential part in the pathogenesis since abortive viral infection was insufficient to induce a full-blown HLH-like syndrome. Nonetheless, a limited set of symptoms, in particular anemia, thrombocytopenia and elevated levels of soluble CD25, appeared less dependent of the viral replication but rather mediated by the host’s immune response, as corroborated by immunosuppressive treatment of infected mice with dexamethasone.

Conclusion

Both virus-mediated pathology and immunopathology cooperate in the pathogenesis of full-blown virus-associated secondary HLH and are closely entangled. A certain level of viremia appears necessary to elicit the characteristic HLH-like symptoms in the model.

An Unsettled Debate About the Potential Role of Infection in Pathogenesis of Atherosclerosis

Association of infection with atherosclerosis is by no means new. Several sero-epidemiological and pathologic studies as well as animal models have shown a link between infection and atherosclerosis. Exciting discoveries in recent times related to role of inter-individual genetic variation in modulating inflammatory response to infection have reignited the enthusiasm in proving a causal link between infection and atherosclerosis. The purpose of this article was to review and analyze the available evidence linking infection with atherosclerosis.

Influence of age, sex and HCMV-serostatus on blood lymphocyte subpopulations in healthy adults

Using a standardized immunophenotyping procedure we studied thirty-eight distinct subpopulations of T, B and NK lymphocytes in 253 healthy blood donors aged from 19 to 67. We analysed the influence of age, sex and HCMV seropositivity on each lymphocyte subpopulations and established reference ranges. We observed that aging influences the largest number of lymphocyte subpopulations with a slow increase of CD8+ EMRA T lymphocytes and of the numbers of circulating Tregs. The proportion of HLA-DR+ cells among Tregs increased with age and was correlated to the proportion of HLA-DR+ cells among effector T CD4+ lymphocytes. Sex had a major impact on absolute counts of CD4+ T cells which were higher in females. HCMV-seropositivity was associated with higher frequencies of CD8+ EMRA memory T lymphocytes while a high frequency of terminally differentiated EMRA CD4+ T cells was observed in 80% of HCMV-positive individuals and in none of the HCMV seronegative individuals.

Tuberculosis and Cardiovascular Disease: Linking the Epidemics

The burden of tuberculosis and cardiovascular disease (CVD) is enormous worldwide. CVD rates are rapidly increasing in low- and middle-income countries. Public health programs have been challenged with the overlapping tuberculosis and CVD epidemics. Monocyte/macrophages, lymphocytes and cytokines involved in cellular mediated immune responses against Mycobacterium tuberculosis are also main drivers of atherogenesis, suggesting a potential pathogenic role of tuberculosis in CVD via mechanisms that have been described for other pathogens that establish chronic infection and latency. Studies have shown a pro-atherogenic effect of antibody-mediated responses against mycobacterial heat shock protein-65 through cross reaction with self-antigens in human vessels. Furthermore, subsets of mycobacteria actively replicate during latent tuberculosis infection (LTBI), and recent studies suggest that LTBI is associated with persistent chronic inflammation that may lead to CVD. Recent epidemiologic work has shown that the risk of CVD in persons who develop tuberculosis is higher than in persons without a history of tuberculosis, even several years after recovery from tuberculosis. Together, these data suggest that tuberculosis may play a role in the pathogenesis of CVD. Further research to investigate a potential link between tuberculosis and CVD is warranted.

Infection and Atherosclerosis Development

Atherosclerosis is a chronic disease hallmarked by chronic inflammation, endothelial dysfunction and lipid accumulation in the vasculature. Although lipid modification and deposition are thought to be a major source of the continuous inflammatory stimulus, a large body of evidence suggests that infectious agents may contribute to atherosclerotic processes. This could occur by either direct effects through infection of vascular cells and/or through indirect effects by induction of cytokine and acute phase reactant proteins by infection at other sites. Multiple bacterial and viral pathogens have been associated with atherosclerosis by seroepidemiological studies, identification of the infectious agent in human atherosclerotic tissue, and experimental studies demonstrating an acceleration of atherosclerosis following infection in animal models of atherosclerosis. This review will focus on those infectious agents for which biological plausibility has been demonstrated in animal models and on the challenges of proving a role of infection in human atherosclerotic disease.

Danger signaling in atherosclerosis

All aspects of the pathogenesis of atherosclerosis are critically influenced by the inflammatory response in vascular plaques. Research in the field of innate immunity from the past 2 decades has uncovered many novel mechanisms elucidating how immune cells sense microbes, tissue damage, and metabolic derangements. Here, we summarize which triggers of innate immunity appear during atherogenesis and by which pathways they can contribute to inflammation in atherosclerotic plaques. The increased understanding gained from studies assessing how immune activation is associated with the pathogenesis of atherosclerosis has provided many novel targets for potential therapeutic intervention. Excitingly, the concept that inflammation may be the core of cardiovascular disease is currently being clinically evaluated and will probably encourage further studies in this area.

The Impact of Mass Spectrometry-Based Proteomics on Fundamental Discoveries in Virology

In recent years, mass spectrometry has emerged as a core component of fundamental discoveries in virology. As a consequence of their coevolution, viruses and host cells have established complex, dynamic interactions that function either in promoting virus replication and dissemination or in host defense against invading pathogens. Thus, viral infection triggers an impressive range of proteome changes. Alterations in protein abundances, interactions, posttranslational modifications, subcellular localizations, and secretion are temporally regulated during the progression of an infection. Consequently, understanding viral infection at the molecular level requires versatile approaches that afford both breadth and depth of analysis. Mass spectrometry is uniquely positioned to bridge this experimental dichotomy. Its application to both unbiased systems analyses and targeted, hypothesis-driven studies has accelerated discoveries in viral pathogenesis and host defense. Here, we review the contributions of mass spectrometry-based proteomic approaches to understanding viral morphogenesis, replication, and assembly and to characterizing host responses to infection.

Human cytomegalovirus-platelet interaction triggers toll-like receptor 2-dependent proinflammatory and proangiogenic responses

OBJECTIVE

Human cytomegalovirus (HCMV) is a widespread pathogen that correlates with various clinical complications, including atherosclerosis. HCMV is released into the circulation during primary infection and periodic viral reactivation, allowing virus-platelet interactions. Platelets are important in the onset and development of atherosclerosis, but the consequences of platelet-HCMV interactions are unclear.

APPROACH AND RESULTS

We studied the effects of HCMV-platelet interactions in blood from healthy donors using the purified clinical HCMV isolate VR1814. We demonstrated that HCMV bound to a Toll-like receptor (TLR) 2-positive platelet subpopulation, which resulted in signal transduction, degranulation, and release of proinflammatory CD40L and interleukin-1β and proangiogenic vascular endothelial-derived growth factor. In mice, murine CMV activated wild-type but not TLR2-deficient platelets. However, supernatant from murine CMV-stimulated wild-type platelets also activated TLR2-deficient platelets, indicating that activated platelets generated soluble mediators that triggered further platelet activation, independent of TLR2 expression. Inhibitor studies, using ADP receptor antagonists and apyrase, revealed that ADP release is important to trigger secondary platelet activation in response to HCMV. HCMV-activated platelets rapidly bound to and activated neutrophils, supporting their adhesion and transmigration through endothelial monolayers. In an in vivo model, murine CMV induced systemic upregulation of platelet-leukocyte aggregates and plasma vascular endothelial-derived growth factor in mice and showed a tendency to enhance neutrophil extravasation in a TLR2-dependent fashion.

CONCLUSIONS

HCMV is a well-adapted pathogen that does not induce immediate thrombotic events. However, HCMV-platelet interactions lead to proinflammatory and proangiogenic responses, which exacerbate tissue damage and contribute to atherogenesis. Therefore, platelets might contribute to the effects of HCMV in accelerating atherosclerosis.

Atherosclerosis and Alzheimer--diseases with a common cause? Inflammation, oxysterols, vasculature

BACKGROUND

Aging is accompanied by increasing vulnerability to pathologies such as atherosclerosis (ATH) and Alzheimer disease (AD). Are these different pathologies, or different presentations with a similar underlying pathoetiology?

DISCUSSION

Both ATH and AD involve inflammation, macrophage infiltration, and occlusion of the vasculature. Allelic variants in common genes including APOE predispose to both diseases. In both there is strong evidence of disease association with viral and bacterial pathogens including herpes simplex and Chlamydophila. Furthermore, ablation of components of the immune system (or of bone marrow-derived macrophages alone) in animal models restricts disease development in both cases, arguing that both are accentuated by inflammatory/immune pathways. We discuss that amyloid β, a distinguishing feature of AD, also plays a key role in ATH. Several drugs, at least in mouse models, are effective in preventing the development of both ATH and AD. Given similar age-dependence, genetic underpinnings, involvement of the vasculature, association with infection, Aβ involvement, the central role of macrophages, and drug overlap, we conclude that the two conditions reflect different manifestations of a common pathoetiology.

MECHANISM

Infection and inflammation selectively induce the expression of cholesterol 25-hydroxylase (CH25H). Acutely, the production of 'immunosterol' 25-hydroxycholesterol (25OHC) defends against enveloped viruses. We present evidence that chronic macrophage CH25H upregulation leads to catalyzed esterification of sterols via 25OHC-driven allosteric activation of ACAT (acyl-CoA cholesterol acyltransferase/SOAT), intracellular accumulation of cholesteryl esters and lipid droplets, vascular occlusion, and overt disease.

SUMMARY

We postulate that AD and ATH are both caused by chronic immunologic challenge that induces CH25H expression and protection against particular infectious agents, but at the expense of longer-term pathology.

Expansion of the NKG2C+ natural killer-cell subset is associated with high-risk carotid atherosclerotic plaques in seropositive patients for human cytomegalovirus

OBJECTIVE

Human cytomegalovirus (HCMV), a pathogen involved in the development and progression of atherosclerosis, promotes in some individuals a marked reconfiguration of the natural killer (NK)-cell compartment whose hallmark is a persistent expansion of a peripheral blood NK-cell subset expressing the CD94/NKG2C NK receptor. We aimed to evaluate whether the HCMV-associated NK-cell compartment reconfiguration is related to carotid atherosclerotic plaque (CAP) instability.

APPROACH AND RESULTS

NK receptor expression (ie, LILRB1, NKG2A, NKG2C, and killer immunoglobulin-like receptors [KIR]) by peripheral NK and T cells was evaluated in 40 patients with HCMV+ with CAP, including nonatherosclerotic strokes (n=15) and healthy subjects (n=11) as controls. High-risk CAP (n=16), defined as carotid stenosis >50% with ipsilateral neurological symptomatology in the previous 180 days, compared with non-high-risk CAP had higher %NKG2C+ NK cells (29.5 ± 22.4% versus 16.3 ± 13.2%; P=0.026; odds ratio, 1.053; 95% confidence interval, 1.002-1.106; P=0.042), with a corresponding reduction in the NKG2A+ NK subset (31.7 ± 17.8% versus 41.8 ± 15.8%; P=0.072). The proportions of NKG2C+ NK cells in high-risk CAP were inversely correlated with the CD4+/CD8+ ratio (R(Spearman)=-0.629; P=0.009) and directly with high-sensitivity C-reactive protein levels (R(Pearson) = 0.591; P=0.012), consistent with higher subclinical systemic inflammation. The intraplaque inflammatory infiltrate, evaluated in 27 CAP obtained after endarterectomy, showed a higher presence of subintimal CD3+ lymphocytes in those patients with HCMV-induced changes in the peripheral NK- and T-cell compartments.

CONCLUSIONS

The expansion of NKG2C+ NK cells in patients with CAP seems to be associated with an increased risk of plaque destabilization in some patients with chronic HCMV infection.

Atherosclerosis and infection: is the jury still not in?

Atherosclerosis is a chronic inflammatory process accounting for increased cardiovascular and cerebrovascular morbidity and mortality. A wealth of recent data has implicated several infectious agents, mainly Chlamydophila pneumoniae, Helicobacter pylori, CMV and periodontal pathogens, in atherosclerosis. Thus, we sought to comprehensively review the available data on the topic, exploring in particular the pathogenetic mechanisms, and discuss anticipated future directions.

Evidence for the role of Epstein Barr Virus infections in the pathogenesis of acute coronary events

BACKGROUND

The role of viral infections in the pathogenesis of atherosclerosis remains controversial largely due to inconsistent detection of the virus in atherosclerotic lesions. However, viral infections elicit a pro-inflammatory cascade known to be atherogenic and to precipitate acute ischemic events. We have published in vitro data that provide the foundation for a mechanism that reconciles these conflicting observations. To determine the relation between an early viral protein, deoxyuridine triphosphate nucleotidohydrolase (dUTPase), produced following reactivation of Epstein Barr Virus (EBV) to circulating pro-inflammatory cytokines, intercellular adhesion molecule-1 (ICAM-1) and acute coronary events.

METHODOLOGY/PRINCIPAL FINDINGS

Blood samples were obtained from 299 patients undergoing percutaneous coronary intervention for stable angina (SA), unstable angina (UA), or acute myocardial infarction (AMI). Plasma concentrations of pro-inflammatory cytokines and neutralizing antibody against EBV-encoded dUTPase were compared in the three patient groups. AMI was associated with the highest measures of interleukin-6 (ANOVA p<0.05; 4.6 ± 2.6 pg/mL in patients with AMI vs. 3.2 ± 2.3 pg/mL in SA). ICAM-1 was significantly higher in patients with AMI (ANOVA p<0.05; 304 ± 116 pg/mL in AMI vs. 265 ± 86 pg/mL SA). The highest values of ICAM-1 were found in patients having an AMI and who were antibody positive for dUTPase (ANOVA p=0.008; 369 ± 183 pg/mL in AMI and positive for dUTPase vs. 249 ± 70 pg/mL in SA negative for dUTPase antibody).

CONCLUSIONS/SIGNIFICANCE

These clinical data support a model, based on in vitro studies, by which EBV may precipitate AMI even under conditions of low viral load through the pro-inflammatory action of the early protein dUTPase that is produced even during incomplete viral replication. They further support the putative role of viral infections in the pathogenesis of atherosclerosis and coronary artery events.

Murine cytomegalovirus (MCMV) infection upregulates P38 MAP kinase in aortas of Apo E KO mice: a molecular mechanism for MCMV-induced acceleration of atherosclerosis

Multiple studies suggest an association between cytomegalovirus (CMV) infection and atherogenesis; however, the molecular mechanisms by which viral infection might exacerbate atherosclerosis are not well understood. Aortas of MCMV-infected and uninfected Apo E knockout (KO) mice were analyzed for atherosclerotic lesion development and differential gene expression. Lesions in the infected mice were larger and showed more advanced disease compared to the uninfected mice. Sixty percent of the genes in the MAPK pathway were upregulated in the infected mice. p38 and ERK 1/2 MAPK genes were 5.6- and 2.0-fold higher, respectively, in aortas of infected vs. uninfected mice. Levels of VCAM-1, ICAM-1, and MCP-1 were ~2.0-2.6-fold higher in aortas of infected vs. uninfected mice. Inhibition of p38 with SB203580 resulted in lower levels of pro-atherogenic molecules and MCMV viral load in aortas of infected mice. MCMV-induced upregulation of p38 may drive the virus-induced acceleration of atherogenesis observed in our model.

Pathogens and atherosclerosis: update on the potential contribution of multiple infectious organisms to the pathogenesis of atherosclerosis

It is currently unclear what causes the chronic inflammation within atherosclerotic plaques. One emerging paradigm suggests that infection with bacteria and/or viruses can contribute to the pathogenesis of atherosclerosis either via direct infection of vascular cells or via the indirect effects of cytokines or acute phase proteins induced by infection at non-vascular sites. This paradigm has been supported by multiple epidemiological studies that have established positive associations between the risk of cardiovascular disease morbidity and mortality and markers of infection. It has also been supported by experimental studies showing an acceleration of the development of atherosclerosis following infection of hyperlipidaemic animal models. There are now a large number of different infectious agents that have been linked with an increased risk of cardiovascular disease. These include: Chlamydia pneumoniae, Porphyromonas gingivalis, Helicobacter pylori , influenza A virus, hepatitis C virus, cytomegalovirus, and human immunodeficiency virus. However, there are significant differences in the strength of the data supporting their association with cardiovascular disease pathogenesis. In some cases, the infectious agents are found within the plaques and viable organisms can be isolated suggesting a direct effect. In other cases, the association is entirely based on biomarkers. In the following review, we evaluate the strength of the data for individual or groups of pathogens with regard to atherosclerosis pathogenesis and their potential contribution by direct or indirect mechanisms and discuss whether the established associations are supportive of the infectious disease paradigm. We also discuss the failure of antibiotic trials and the question of persistent infection.

Association of Atherosclerosis With Expression of the LILRB1 Receptor By Human NK and T-Cells Supports the Infectious Burden Hypothesis

Objective—

The contribution of human cytomegalovirus (HCMV) to vascular disease may depend on features of the immune response not reflected by the detection of specific antibodies. Persistent HCMV infection in healthy blood donors has been associated with changes in the distribution of NK cell receptors (NKR). The putative relationship among HCMV infection, NKR distribution, subclinical atherosclerosis, and coronary heart disease was assessed.

Methods and Results—

NKR expression was compared in acute myocardial infarction (AMI) patients ( n =70) and a population-based control sample ( n =209). The relationship between NKR expression and carotid intima-media thickness (CIMT) in controls ( n =149) was also studied. HCMV infection was associated with higher proportions of NKG2C+ and LILRB1+ NK and T-cells. In contrast, only LILRB1+ NK and CD56+ T-cells were found to be increased in AMI patients, independent of age, sex, conventional vascular risk factors, and HCMV seropositivity. Remarkably, LILRB1 expression in NK and T-cells significantly correlated with CIMT in controls.

Conclusion—

The association of overt and subclinical atherosclerotic disease with LILRB1+ NK and T-cells likely reflects a relationship between the immune challenge by infections and cardiovascular disease risk, without attributing a dominant role for HCMV. Our findings may lead to the identification of novel biomarkers of vascular disease.

The immune system in atherosclerosis

Cardiovascular disease, a leading cause of mortality worldwide, is caused mainly by atherosclerosis, a chronic inflammatory disease of blood vessels. Lesions of atherosclerosis contain macrophages, T cells and other cells of the immune response, together with cholesterol that infiltrates from the blood. Targeted deletion of genes encoding costimulatory factors and proinflammatory cytokines results in less disease in mouse models, whereas interference with regulatory immunity accelerates it. Innate as well as adaptive immune responses have been identified in atherosclerosis, with components of cholesterol-carrying low-density lipoprotein triggering inflammation, T cell activation and antibody production during the course of disease. Studies are now under way to develop new therapies based on these concepts of the involvement of the immune system in atherosclerosis.

RCMV increases intimal hyperplasia by inducing inflammation, MCP-1 expression and recruitment of adventitial cells to intima

Background

Cytomegalovirus (CMV) infection has been associated with accelerated transplant vasculopathy. In this study, we assessed the effects of acute rat CMV (RCMV) infection on vessel remodeling in transplant vasculopathy, focusing on allograft morphology, inflammation and contribution of adventitial cells to intimal hyperplasia.

Methods

Infrarenal aorta was locally infected with RCMV and transplanted from female F344 rats to male Lewis rats. Graft samples were collected 2 and 8 weeks after transplantation and analyzed for intimal hyperplasia, collagen degradation and inflammation. Transplantation of aorta followed by transplantation of RCMV infected and labeled isogenic adventitia were performed to study migration of adventitial cells towards the intima.

Results

Intimal hyperplasia was increased threefold in infected allografts. RCMV induced apoptosis in the media, expression of matrix metalloproteinase 2, and decreased collagen deposits. Macrophage infiltration was increased in the infected allografts and resulted in increased production of MCP-1. RCMV-infected macrophages were observed in the adventitia and intima. Cells derived from infected adventitia migrated towards the intima of the allograft.

Conclusions

RCMV enhances infiltration of macrophages to the allografts, and thereby increases MCP-1 production and inflammation, followed by recruitment of adventitial cells to the intima and accelerated intimal hyperplasia.

Detection of human cytomegalovirus in atherosclerotic carotid arteries in humans

BACKGROUND/PURPOSE

Atherosclerosis plays an important role in stroke. A microbiological infection has been suggested to be involved in the pathogenesis of atherosclerosis, in particular the human cytomegalovirus (HCMV). The objective of this study was to determine the association between HCMV infection and atherosclerosis of the internal carotid arteries in patients of Chinese Han ethnicity with ischemic stroke.

METHODS

HCMV DNA and antigen were detected in atherosclerotic internal carotid arteries from 35 patients with ischemic stroke and 20 controls from a Chinese Han ethnic population. Immunohistochemistry, in situ hybridization and polymerase chain reaction were used to detect the HCMV immediate early (IE) and late (L) antigen as well as DNA in the vascular walls.

RESULTS

We observed that the proportion of cases that tested positive for HCMV IE but not L antigen and DNA was statistically greater in stroke patients compared with the control population.

CONCLUSION

HCMV IE antigen and DNA were associated with the pathological process of atherosclerosis. The vessel wall might be the infection site of the dormant virus.

Infections and autoimmunity: a panorama

For more than 2,000 years, it was thought that malignant spirits caused diseases. By the end of nineteenth century, these beliefs were displaced by more modern concepts of disease, namely, the formulation of the “germ theory,” which asserted that bacteria or other microorganisms caused disease. With the emergence of chronic degenerative and of autoimmune diseases in the last century, the causative role of microorganisms has been intensely debated; however, no clear explanatory models have been achieved. In this review, we examine the current available literature regarding the relationships between infections and 16 autoimmune diseases. We critically analyzed clinical, serological, and molecular associations, and reviewed experimental models of induction of and, alternatively, protection from autoimmune diseases by infection. After reviewing several studies and reports, a clinical and experimental pattern emerges: Chronic and multiple infections with viruses, such as Epstein–Barr virus and cytomegalovirus, and bacteria, such as H. pylori, may, in susceptible individuals, play a role in the evolvement of autoimmune diseases. As the vast majority of infections pertain to our resident microbiota and endogenous retroviruses and healthy carriage of infections is the rule, we propose to focus on understanding the mechanisms of this healthy carrier state and what changes its configurations to infectious syndromes, to the restoration of health, or to the sustaining of illness into a chronic state and/or autoimmune disease. It seems that in the development of this healthy carriage state, the infection or colonization in early stages of ontogenesis with key microorganisms, also called ‘old friends’ (lactobacilli, bifidobacteria among others), are important for the healthy living and for the protection from infectious and autoimmune syndromes.

HCMV microinfections in inflammatory diseases and cancer

Human cytomegalovirus (HCMV) is a wide-spread human virus that was mainly known to cause disease in immunocompromised patients. A new entity of infection can be diagnosed with high sensitive techniques; HCMV microinfections that often exhibit an altered pattern of IE protein expression. We have recently discovered that HCMV microinfections are very common in patients with inflammatory diseases and certain cancers. The discovery of active HCMV infections in tissue specimens from patients with inflammatory diseases raises the question of whether the infection is an epiphenomenon or whether the virus plays a causative role in disease development. After a primary infection, which is generally asymptomatic in immunocompetent individuals, HCMV establishes latency and persists in its host. In infected cells, the virus can produce over 250 proteins, but only about 50-60 are believed to be essential for viral replication. Thus, the vast majority of these viral proteins enable the virus to co-exist with its host. Such proteins act through highly sophisticated mechanisms to control different cellular and immunological functions in order to facilitate viral production and to avoid detection and elimination of the virus by the immune system. These proteins may also contribute to the development of common inflammation-related diseases.

Chronic Immune Reactivity Against Persisting Microbial Antigen in the Vasculature Exacerbates Atherosclerotic Lesion Formation

Objective— The purpose of this study was to examine the relative contribution of different immunopathological mechanisms during murine cytomegalovirus (MCMV)-mediated acceleration of atheroma formation in apolipoprotein E–deficient (apoE −/− ) mice.

Methods and Results— To distinguish between the effects of systemic activation and cognate immune reactivity against a pathogen-derived persisting antigen in the vasculature, we used hypercholesterolemic transgenic mice constitutively expressing the β-galactosidase (β-gal) transgene in the cardiovascular system (apoE −/− ×SM-LacZ). After infection with β-gal–recombinant MCMV-LacZ, apoE −/− , and apoE −/− ×SM-LacZ mice mounted comparable cellular immune responses against the virus. β-gal–specific CD8 + T cells expanded rapidly and remained detectable for at least 100 days in both mouse strains. However, compared with apoE −/− mice, apoE −/− ×SM-LacZ mice developed drastically accelerated atherosclerosis. Moreover, atherosclerotic lesions in MCMV-LacZ–infected apoE −/− ×SM-LacZ but not apoE −/− mice were associated with pronounced inflammatory infiltrates.

Conclusions— Taken together, our data indicate that chronic immune reactivity against pathogen-derived antigens persisting in the vasculature significantly exacerbates atherogenesis.

Innate immune system regulation of nuclear hormone receptors in metabolic diseases

The immune system modulates a number of biological processes to properly defend against pathogens. Here, we review how crosstalk between nuclear hormone receptors and the innate immune system may influence multiple biological functions during an immune response. Although nuclear hormone receptor repression of innate immune responses and inflammation has been well studied, a number of new studies have identified repression of nuclear hormone receptor signaling by various innate immune responses. IFN regulatory factor 3, a key transcription factor involved in the induction of antiviral genes, may play a role in mediating such crosstalk between the innate immune response and nuclear receptor-regulated metabolism. This crosstalk mechanism is now implicated in the pathogenesis of atherosclerosis and Reye's syndrome and could provide an explanation for other pathogen-associated metabolic and developmental disorders.

Immune activation following cytomegalovirus infection: More important than direct viral effects in cardiovascular disease?

BACKGROUND

Over the last 30 years multiple micro-organisms have been associated with different types of vascular disease, like atherosclerosis, restenosis or transplant arteriosclerosis. Nonetheless, it is still ambiguous which molecular mechanisms are exactly involved in the exacerbating effect of microbes in these disorders.

OBJECTIVES AND STUDY DESIGN

The present review summarizes sero-epidemiological, in vitro and animal data supporting the role of cytomegalovirus, a member of the herpes virus family, in vascular disease. Additionally, various ways by which the virus can potentially affect the disease will be discussed.

RESULTS

Rodent models as well as in vitro studies suggested that CMV might enhance lesion formation in various ways, like augmentation of the oxLDL uptake, altering monocyte adhesion or increasing the production of pro-inflammatory cytokines. Nevertheless, recent data from our lab and others suggest that alternative mechanisms also may contribute to CMV induced. Inspired by this, we will hypothesise alternative mechanisms by which CMV might affect atherosclerosis.

CONCLUSIONS

Although researchers have tried for many years to unravel the tactics by which micro-organisms, like CMV, aggravate atherosclerosis, so far most suggested mechanisms failed to fully explain both experimental and clinical observations. Therefore, new means to elucidate the observed effects are required.