Infection and atherosclerosis--focus on cytomegalovirus and Chlamydia pneumoniae

Evaluating the relationship between Helicobacter pylori infection

Introduction

Helicobacter pylori is a gram-negative spiral bacterium that is frequently found in the human stomach. Significant association has been reported between Cytotoxin associated gene A (CagA)- positive Helicobacter pylori strains and coronary heart disease. The aim of the present study is to investigate the carotid intima-media thickness as an indicator of atherosclerosis in people with Helicobacter pylori infection.

Methods

This study was done on patients who underwent upper GI endoscopy and biopsy, and after obtaining conscious consent underwent ultrasound of the right and left carotid arteries for measuring carotid intima-media thickness (CIMT) and blood tests.

Results

In this study, 90 patients who underwent upper GI endoscopy were examined in three groups: negative H. pylori negative, positive cagA and negative cagA. The right, left and average of CIMT in cagA-positive group were significantly higher than the other two groups (p < 0.05). Howerver, the average of CIMT was not significantly different between men and women. Also, the hsCRP average level in positive cagA group was significantly higher than other groups (p < 0.05).

Conclusion

Our findings suggest that there is an increase in CIMT values in patients with H. pylori infection, especially in cases of positive cagA. The positive cagA group showed significantly higher levels of hs-CRP, as a marker of elevated inflammatory response. Therefore, H. pylori infection, especially cagA-positive strains and its associated systemic inflammatory response can be considered as a contributing factor in atherosclerosis and cardiovascular disease.

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H.pylori infection especially in case of positive CagA⁺ caused the right/left CIMT increase.

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Higher levels of inflammation in H.pylori, CagA patients and atherosclerosis risk factors couldn’t cause the significant difference.

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H.pylori infection with positive CagA and its inflammation is an important factor in atherosclerosis and cardiovascular diseases.

Atherosclerosis pathophysiology and the role of novel risk factors: a clinicobiochemical perspective

Atherosclerosis is the root cause of the biggest killer of the 21st century. Mechanisms contributing to atherogenesis are multiple and complex. A number of theories-including the role of dyslipidemia, hypercoagulability, oxidative stress, endothelial dysfunction, and inflammation and infection by certain pathogens-have been propounded from time to time explain this complex phenomenon. Recently it has been suggested that atherosclerosis is a multifactorial, multistep disease that involves chronic inflammation at every step, from initiation to progression, and that all the risk factors contribute to pathogenesis by aggravating the underlying inflammatory process. A better understanding of the pathogenesis of atherosclerosis will aid in devising pharmaceutical and lifestyle modifications for reducing mortality resulting from coronary artery disease (CAD).A comprehensive literature search was conducted using the Web sites of the National Library of Medicine (http:// www.ncbl.nlm.nih.gov/) and PubMed Central, the US National Library of Medicine's digital archive of life sciences literature (http:// www.pubmedcentral.nih.gov/). The data were accessed from books and journals in which relevant articles in this field were published. The whole spectrum of coronary artery disease evolves through various events that lead to the formation and progression of atherosclerotic plaque and finally its complications. Atherosclerosis is the culprit behind coronary artery disease, cerebral vascular disease, and peripheral vascular disease. The pathogenic mechanisms are varied and complex. Of late, the role of lipoprotein (a), homocysteine, and inflammation and infection as prime culprits in pathogenesis of CAD is the subject of intense research and debate. The appreciation of the role of inflammation in atherosclerosis provides a mechanistic framework to understand the clinical benefits of newer therapeutic strategies, and a better understanding of pathogenesis aids in formulating preventive and therapeutic strategies in reducing mortality resulting from CAD.An in-depth knowledge of the various pathogenic mechanisms involved in atherosclerosis can help in substantiating the current existing knowledge about the CAD epidemic. This knowledge will help clinicians to better manage the disease, which affects Indians in its most severe form.

Bacterial Profile and Burden of Periodontal Infection in Subjects With a Diagnosis of Acute Coronary Syndrome

BACKGROUND

Periodontitis has been identified as a potential risk factor in cardiovascular diseases. It is possible that the stimulation of host responses to oral infections may result in vascular damage and the inducement of blood clotting. The aim of this study was to assess the role of periodontal infection and bacterial burden as an explanatory variable to the activation of the inflammatory process leading to acute coronary syndrome (ACS).

METHODS

A total of 161 consecutive surviving cases admitted with a diagnosis of ACS and 161 control subjects, matched with cases according to their gender, socioeconomic level, and smoking status, were studied. Serum white blood cell (WBC) counts, high- and low-density lipoprotein (HDL/LDL) levels, high-sensitivity C-reactive protein (hsC-rp) levels, and clinical periodontal routine parameters were studied. The subgingival pathogens were assayed by the checkerboard DNA-DNA hybridization method.

RESULTS

Total oral bacterial load was higher in the subjects with ACS (mean difference: 17.4x10(5); SD: 10.8; 95% confidence interval [CI]: 4.2 to 17.4; P<0.001), and significant for 26 of 40 species including Porphyromonas gingivalis, Tannerella forsythensis, and Treponema denticola. Serum WBC counts, hsC-rp levels, Streptococcus intermedius, and Streptococcus sanguis, were explanatory factors to acute coronary syndrome status (Nagelkerke r2=0.49).

CONCLUSION

The oral bacterial load of S. intermedius, S. sanguis, Streptococcus anginosus, T. forsythensis, T. denticola, and P. gingivalis may be concomitant risk factors in the development of ACS.

Fatal attraction: cytomegalovirus-encoded chemokine homologs

Members of the cytomegalovirus (CMV) subfamily of betaherpesviruses infecting primates and rodents encode divergent proteins with sequence characteristics and activities of chemokines, a class of small, secreted proteins that control leukocyte migration and trafficking behavior. Human CMV genes UL146 and UL147 encode proteins with sequence characteristics of CXC chemokines, whereas, murine CMV encodes a CC chemokine homolog (MCK-2). Human CMV UL146 encodes a neutrophil-attracting chemokine denoted viral CXC chemokine-1 (vCXCL1) that is as potent as host IL-8 and functions via the CXCR2 receptor, one of two human IL-8 receptors. Murine CMV MCK-2 is composed of a chemokine domain derived from open reading frame (ORF) m131 (and denoted MCK-1) as well as a domain derived from m129 that does not have sequence similarity to any known class of proteins. A synthetic version of murine CMV m131 (MCK-1) protein carries out many of the activities of a positive-acting chemokine, including transient release of intracellular calcium stores and cell adhesion of peritoneal macrophage populations. In the context of the viral genome and infection of the mouse host, the m131-m129 (MCK-2) gene product confers increased inflammation, higher levels of viremia, and higher titers of virus in salivary glands, consistent with a role in promoting dissemination by attracting an important mononuclear leukocyte population. Other characterized primate CMVs, but not other primate betaherpesviruses, encode gene products similar to human UL146 and UL147. Other characterized rodent CMVs encode a gene product similar to the murine CMV chemokine homolog, although not as a spliced gene product. Thus chemokines, like viral proteins that downmodulate MHC class I expression or have sequence homology to host MHC class I proteins, have evolved in primate and rodent CMVs to carry out an analogous set of immunomodulatory functions during infection of the host even though they arise from distinct origins.

[Atherosclerosis, multiple sclerosis, and Alzheimer's disease: what role for Herpesviridae?]

Herpesviridae are ubiquitous, and are commonly involved in well identified diseases as genital herpes, chickenpox and herpes zoster, infectious mononucleosis, exanthem subitum... They are responsible for latent and chronic infections after primary infection. Atherosclerosis, multiple sclerosis, Alzheimer's disease are diseases which are very different, and for which pathogenesis remains unknown. Several authors have hypothesized that Herpesviridae could play a role in such diseases. The present paper reviews arguments not only in favour but also against such hypothesis. Any formal conclusion is impossible, and more extensive studies are warranted.

Absence of Chlamydia pneumoniae in surgical specimens of coronary and carotid arteries by polymerase chain reaction

PURPOSE

Several recent articles indicate the renewed interest that Chlamydia pneumoniae is associated with and contributes to arterial diseases. Associations have been established for coronary arteries, carotid arteries and abdominal aortic aneurysms by serological studies, immunofluorescence and DNA-specific testing. The purpose of this study was to determine the presence of C. pneumoniae in coronary artery plaques, carotid artery plaques and old vein grafts that were harvested at the time of surgery.

METHODS AND MATERIALS

Interventions were carried out on patients with carotid artery disease and coronary disease based upon their anatomic findings and symptomatology. Plaques were removed from the carotid arteries with standard endarterectomy techniques. The coronary plaques were removed utilizing blunt dissection to peel the plaque from the coronary artery. Old vein grafts were harvested during repeat surgery by excising the vein grafts. The tissue specimens were analyzed by polymerase chain reaction (PCR).

RESULTS

Ninety-nine specimens from 68 consecutive patients with advanced coronary atherosclerosis with or without cerebrovascular disease were analyzed. We failed to find C. pneumoniae in any of the vascular tissue.

CONCLUSIONS

A large cooperative study involving surgical specimen analysis is needed to assess the role of C. pneumoniae in the etiology of atherosclerosis.

The association of infection and coronary artery disease: an update

Numerous studies have reported an association of coronary atherosclerosis and restenosis with certain bacterial and viral infections. This article reviews the pathophysiology of atherosclerosis, the role of infectious agents (cytomegalovirus, Chlamydia pneumoniae and Helicobacter pylori) in atherogenesis and studies supporting the potential beneficial effects of antibiotics or antiviral agents in the management of atherosclerotic disease. The interactions of cytomegalovirus and the arterial wall have been extensively studied. However, despite the successful preliminary therapeutic trials with the use of macrolides in augmenting possible C. pneumoniae-induced cardiovascular events, the exact mechanisms of how C. pneumoniae enters the arterial wall remains unknown at this point. For H. pylori, regardless of the large number of studies performed to assess the association between H. pylori and coronary artery disease, no definitive conclusion could be made at this time, due to contradictory results. Before one can widely adopt the use of antibiotics or antiviral agents as treatment for atherosclerosis, further studies must be designed to address some important issues. In vivo animal models need to be established to further examine the various hypotheses regarding the interaction of infectious agents and atherosclerosis and restenosis. Large-scale prospective cohort studies should be designed to relate evidence of infection to future risk of cardiovascular diseases. Confounding variables, such as other cardiovascular risk factors and socio-economic status, should be controlled in order to strengthen the association. Further interventional studies are also required to establish the best antibiotic or antiviral regimen to maximise efficacy and minimise side effects.

The quality of dialysate: an integrated approach

The role of bacterial contamination of dialysis water with respect to chronic inflammatory diseases associated with long-term hemodialysis therapy has been greatly underestimated in the last two decades. In the present article, recent multicenter studies assessing the bacteriological quality of water and dialysate are discussed. In addition, we describe that pyrogenic substances of bacterial origin derived from contaminated dialysate penetrate intact dialyzer membranes with the consequence of the induction of an inflammatory response in the patients. The influence of dialyzer membrane characteristics on the passage of bacterial substances from dialysate into blood are discussed. Reaching the patients blood, bacteria-derived substances activate circulating mononuclear cells to produce proinflammatory cytokines. Cytokines such as interleukin-1 beta and tumor necrosis factor-alpha are mediators of the acute phase response resulting in elevated levels of acute phase proteins (for example, C-reactive protein). The consequence is a state of microinflammation that may contribute to progressive inflammatory diseases in chronic renal failure such as beta2-microglobulin amyloidosis, protein catabolism, and atherosclerosis. The use of sterile dialysate reduces cytokine production and plasma levels of acute phase proteins, and may positively influence progressive inflammatory diseases in patients with end-stage renal failure.

[Hematologic and immunologic manifestations of primary cytomegalovirus infections in non-immunocompromised hospitalized adults]

PURPOSE

Cytomegalovirus (CMV) infection in non-immunocompromised adults can sometimes induce hematological and immunological disorders that may mislead diagnosis.

METHODS

Case reports of hospitalized non-immunocompromised adults with positive serology for CMV including the presence of immunoglobulin M or seroconversion were assessed in a retrospective study (1981-1998). We focused on clinical and biological abnormalities showing the role of CMV in disruption of functioning of hematological and immunological systems.

RESULTS

Among 115 patients, lymphoma-like syndrome with large adenopathies and/or splenomegaly was diagnosed in eight patients, uncovering underlying CMV infection. Lymphoma was accompanied by hematoma in two patients. Three patients presented leg purpura (with thrombotic thrombocytopenic purpura in one case), one patient had cutaneous vasculitis and on other a Still's disease. Blood abnormalities were mononucleosis (64%), anemia (20%), and thrombopenia (25%) often of peripheral or hemolytic origin or due to hypersplenia. Electrophoresis of serum proteins showed an increase in immune globulins in 56% of the cases and monoclonal abnormality in nine cases. Immunological assessment was conducted in 18 patients. At least one abnormality was depicted in ten patients, consisting of either antinuclear, anti-platelet or anti smooth muscle antibodies, cryoglobulinemia, rheumatoid factor, or reduced complement fixation.

CONCLUSION

Testing for CMV infection can be of value in case of blood or immunological disorders associated with clinical or biological signs. Although hematological disorders occur early, they are rarely severe. Immunological disorders are rarely symptomatic, but often raise issues regarding the potential genesis of immune diseases in at-risk patients.

Chlamydia pneumoniae and anti-infective therapy: their role in the pathogenesis and treatment of coronary artery disease

Cardiovascular disease remains the most common cause of death in the United States; however, conventional cardiovascular risk factors fail to explain completely the pathogenesis of atherosclerosis and coronary artery disease. There has been recent interest in the association between Chlamydia pneumoniae and the risk of development or progression of atherosclerotic disease. This association has become evident through serologic, pathologic, and animal-based models and, more recently, through limited trials of antichlamydial antibiotics in humans. Whether C. pneumoniae is a causative agent or "innocent bystander" or whether antibiotic therapy has any role in the treatment of cardiovascular disease remains to be determined.