Chlamydia pneumoniae DNA in patients with symptomatic carotid atherosclerotic disease

The Probable Role of Chlamydia pneumoniae Infection in Acute Stroke

Cardiovascular diseases are the most leading cause of worldwide mortality. According to USA statistics, about 1 of 6 cardiovascular deaths is due to stroke. Stroke is the second most common cause of death and a chief cause of disability due to EU data. Treatment, care providing, rehabilitation costs and with the labor loss, the overall cost in EU due to stroke was estimated about €45 billion in year 2017. Acute stroke due to infectious diseases via several possible mechanisms with various clinical presentations were previously reported in the literature. Chlamydia pneumoniae is an obligate intracellular bacteria and extremely common in adult individuals. Besides it being a major cause of pneumonia in adults, association between atherosclerosis and vascular diseases was demonstrated by several sero-epidemiological studies and by direct detection of organism in atherosclerotic lesions by electron microscopy, immunohistochemistry, polymerase chain reaction. Also, several sero-epidemiological studies have demonstrated a link between Chlamydia pneumoniae infection and acute stroke. In this chapter, we will summarize the data in literature regarding the association between Chlamydia pneumoniae infection and acute stroke and we will try to explain the possible mechanisms that could be responsible in pathophysiology of stroke in these patients.

Oxidative Stress and Inflammation in SARS-CoV-2- and Chlamydia pneumoniae-Associated Cardiovascular Diseases

Throughout the years, a growing number of studies have provided evidence that oxidative stress and inflammation may be involved in the pathogenesis of infectious agent-related cardiovascular diseases. Amongst the numerous respiratory pathogens, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel coronavirus responsible for the global ongoing pandemic, and Chlamydia pneumoniae, a widely known intracellular obligate bacteria, seem to have an essential role in promoting reactive oxygen species and cytokine production. The present review highlights the common oxidative and inflammatory molecular pathways underlying the cardiovascular diseases associated with SARS-CoV-2 or C. pneumoniae infections. The main therapeutic and preventive approaches using natural antioxidant compounds will be also discussed.

Chlamydia trachomatis and Chlamydia pneumoniae Interaction with the Host: Latest Advances and Future Prospective

Research in Chlamydia trachomatis and Chlamydia pneumoniae has gained new traction due to recent advances in molecular biology, namely the widespread use of the metagenomic analysis and the development of a stable genomic transformation system, resulting in a better understanding of Chlamydia pathogenesis. C. trachomatis, the leading cause of bacterial sexually transmitted diseases, is responsible of cervicitis and urethritis, and C. pneumoniae, a widespread respiratory pathogen, has long been associated with several chronic inflammatory diseases with great impact on public health. The present review summarizes the current evidence regarding the complex interplay between C. trachomatis and host defense factors in the genital micro-environment as well as the key findings in chronic inflammatory diseases associated to C. pneumoniae.

Molecular characterisation of Chlamydia pneumoniae associated to atherosclerosis

Chlamydia pneumoniae is a respiratory pathogen associated with chronic inflammatory diseases such as asthma and atherosclerosis, and its detection in human carotid and coronary atheroma suggests some support for its involvement in atherogenesis. The main objective of our study was to evaluate the association between Chlamydia pneumoniae and atherosclerosis in Moroccan patients through a case-control approach and detected strain genotyping. A total of 137 cases and 124 controls were enrolled, nested PCR was performed for Chlamydia pneumoniae screening of the peripheral blood mononuclear cells (PBMCs) of both cases and controls as well as atheroma plaques from 37 cases, and positive samples were subjected to sequencing for genotyping and phylogenetic analysis. The results showed 54% and 18%, respectively, for positivity in cases and control PBMCs and 86.5% in atheroma plaques, the difference being significant between the two groups (P < 0.001, ORa = 8.580, CI, 95% [3.273-22.491]). Strain sequence analyses showed more than 98% similarity with human reference strains, and revealed various genotypes. This study supports the involvement of Chlamydia pneumoniae in atherosclerosis in the studied population and genotyping revealed that detected strains were identical to human strains circulating worldwide.

Chlamydia Pneumoniae in Asymptomatic Carotid Atherosclerosis

We evaluated, in 415 patients with asymptomatic carotid atherosclerosis: (i) the prevalence of C. pneumoniae DNA in atherosclerotic carotid plaques and peripheral blood mononuclear cells (PBMC); (ii) the distribution of C. pneumoniae in atherosclerotic carotid plaques and PBMC from the same patients; (iii) the correlation between circulating anti-chlamydial antibodies and the presence of C. pneumoniae DNA. Overall, 160 atherosclerotic carotid plaques and 174 PBMC specimens from patients with asymptomatic carotid atherosclerosis were examined by ompA nested touchdown PCR for presence of C. pneumoniae. In addition, C. pneumoniae DNA was detected in 81 specimens of atherosclerotic carotid plaque and PBMC obtained from the same patients. C. pneumoniae DNA was found in 36.9% of atherosclerotic carotid plaques and in 40.2% of PBMC specimens examined (P=NS). With regard to 81 patients, C. pneumoniae DNA was detected in 27.2% of atherosclerotic carotid plaques and in 44.4% of PBMC specimens (P=0.05). In 18 patients, the presence of C. pneumoniae DNA in PBMC specimens and atherosclerotic carotid plaques coincided (P=0.005). No statistically significant association was found between anti-C pneumoniae antibodies (IgG and IgA) and positive PCR results. In conclusion, our results suggest that the detection of C. pneumoniae DNA in PBMC specimens seems to be a first-choice method to identify the patients at risk for endovascular chlamydial infection.

Infectious Agents in Atherosclerotic Cardiovascular Diseases through Oxidative Stress

Accumulating evidence demonstrates that vascular oxidative stress is a critical feature of atherosclerotic process, potentially triggered by several infectious agents that are considered as risk co-factors for the atherosclerotic cardiovascular diseases (CVDs). C. pneumoniae has been shown to upregulate multiple enzymatic systems capable of producing reactive oxygen species (ROS) such as NADPH oxidase (NOX) and cyclooxygenase in vascular endothelial cells, NOX and cytochrome c oxidase in macrophages as well as nitric oxide synthase and lipoxygenase in platelets contributing to both early and late stages of atherosclerosis. P. gingivalis seems to be markedly involved in the atherosclerotic process as compared to A. actinomycetemcomitans contributing to LDL oxidation and foam cell formation. Particularly interesting is the evidence describing the NLRP3 inflammasome activation as a new molecular mechanism underlying P. gingivalis-induced oxidative stress and inflammation. Amongst viral agents, immunodeficiency virus-1 and hepatitis C virus seem to have a major role in promoting ROS production, contributing, hence, to the early stages of atherosclerosis including endothelial dysfunction and LDL oxidation. In conclusion, oxidative mechanisms activated by several infectious agents during the atherosclerotic process underlying CVDs are very complex and not well-known, remaining, thus, an attractive target for future research.

Investigation of Chlamydia pneumoniae infection in Moroccan patients suffering from cardiovascular diseases

Chlamydia pneumoniae is an intracellular bacterium responsible for respiratory diseases and is highly involved in cardiovascular disease development, mainly atherosclerosis. The main objective of our study was to evaluate C. pneumoniae prevalence in Moroccan patients suffering from cardiovascular diseases. A total of 115 patients with cardiovascular diseases were enrolled, and their clinical and behavioral information was recorded. Blood was sampled from all patients as well as the atheroma plaques from 36 patients undergoing surgery. Nested PCR was performed for C. pneumoniae DNA detection in both peripheral blood mononuclear cells (PBMCs) and atheroma plaques. Statistical analysis was performed using EpiInfo software. Data analysis showed cardiovascular disease dominance in men, with a sex ratio M/F of 3.4, a majority of tobacco users (52.2%), and many diabetics (44.3%). A significant difference between genders was shown for tobacco use (p<0.05). Positive cases for PBMCs and atheroma plaques were 61% and 86%, respectively, and a significant difference between PBMCs and atheroma plaque infection was identified (p=0.02). Data analysis also showed that 12% of patients presented only C. pneumoniae infection as a risk factor. Therefore, the high prevalence of C. pneumoniae suggests its involvement in atherosclerosis, and further investigation is recommended for confirmation.

Chlamydia Pneumoniae Infection in Patients with Acute Coronary Syndrome: A Clinical and Serological 1-Year Follow-Up

The role of Chlamydia pneumoniae infection in pathogenesis and prognostic stratification of patients with acute coronary syndromes is still unclear. However, a limitation of many studies is the evaluation of the long-term prognostic role of a sample obtained during the acute phase, whereas the assessment of the temporal trend of antibody titers could be more useful. One-hundred and fourteen consecutive patients with acute coronary syndromes (71 with acute myocardial infarction and 43 with unstable angina) were studied. Blood samples were obtained immediately after hospital admission and 1, 3, 6 and 12 months after the acute event. The microimmunofluorescence test was used to detect C. pneumoniae specific antibodies. The incidence of new coronary events (death, myocardial infarction, recurrent angina) was recorded during the 1-year follow-up period. No significant difference was found between patients with (n = 35) or without (n = 79) new coronary events (N.C.E.) regarding baseline and serial values of C. pneumoniae antibodies. The rate of high titers at any time of follow-up was also similar in the two groups: IgG ≥1:512 were present in 52%, 64%, 55% and 32% of N.C.E.+ patients, and in 48%, 54%, 52% and 36% of N.C.E.- patients at 1, 3, 6 and 12 months respectively; IgA ≥ 1:256 were present in 26%, 23%, 30% and 23% of N.C.E.+ patients and in 20%, 30%, 25% and 19% of N.C.E.- patients at 1, 3, 6 and 12 months respectively. Our data indicate that elevated titers of C. pneumoniae antibodies, even with a serial 1-year evaluation, are not a predictor of future coronary events in patients with acute myocardial infarction or unstable angina.

Chlamydia Pneumoniae in PBMC: Reproducibility of the OMPA Nested Touchdown PCR

The aim of our study was to evaluate whether the replicate PCR testing may provide more accurate estimates of C. pneumoniae DNA prevalence in PBMC of patients undergoing carotid endarterectomy. Clinical sensitivity and reproducibility of ompA nested touchdown PCR was also performed. Clinical sensitivity and reproducibility was examined by testing C. pneumoniae-negative PBMC spiked with serial dilutions of semipurified C. pneumoniae elementary bodies (from 8 to 0.002 IFU/ml). Detection of C. pneumoniae DNA was performed by ompA nested touchdown PCR. Each clinical and spiked PBMC DNA specimen was analyzed in replicates of 1,3,5 and 10. PCR results of serial dilutions of C. pneumoniae DNA performed in replicates of 10 were analysed by probit analysis.

C. pneumoniae DNA was detected in 14 of the 30 (46.7%) PBMC clinical specimens examined when 10 replicates were tested. When we analyzed 1, 3 and 5 replicates, 4 (13.3%), 7(23.3%), 12(40%) of the 30 specimens were positive, respectively. The limit of detection of ompA nested PCR touchdown was 0.008 IFU/ml when 10 replicates were tested. The ompA nested PCR had reproducibility scores of 10 for 10 from 8 to 4 IFU/ml concentration, but scores decreased for smaller numbers of IFU/ml. Our results showed that repeat testing of the same specimen increased clinical sensitivity as well as reproducibility of the ompA nested touchdown PCR. In conclusion the replicate PCR testing improves the performance of ompA nested touchdown PCR and provides a more accurate estimates of the prevalence of C. pneumoniae in PBMC of patients with atherosclerotic cardiovascular disease.

Chlamydia pneumoniae and oxidative stress in cardiovascular disease: state of the art and prevention strategies

Chlamydia pneumoniae, a pathogenic bacteria responsible for respiratory tract infections, is known as the most implicated infectious agent in atherosclerotic cardiovascular diseases (CVDs). Accumulating evidence suggests that C. pneumoniae-induced oxidative stress may play a critical role in the pathogenesis of CVDs. Indeed, the overproduction of reactive oxygen species (ROS) within macrophages, endothelial cells, platelets and vascular smooth muscle cells (VSMCs) after C. pneumoniae exposure, has been shown to cause low density lipoprotein oxidation, foam cell formation, endothelial dysfunction, platelet adhesion and aggregation, and VSMC proliferation and migration, all responsible for the typical pathological changes of atherosclerotic plaque. The aim of this review is to improve our insight into C. pneumoniae-induced oxidative stress in order to suggest potential strategies for CVD prevention. Several antioxidants, acting on multi-enzymatic targets related to ROS production induced by C. pneumoniae, have been discussed. A future strategy for the prevention of C. pneumoniae-associated CVDs will be to target chlamydial HSP60, involved in oxidative stress.

Infectious burden and atherosclerosis: A clinical issue

Atherosclerotic cardiovascular diseases, chronic inflammatory diseases of multifactorial etiology, are the leading cause of death worldwide. In the last decade, more infectious agents, labeled as “infectious burden”, rather than any single pathogen, have been showed to contribute to the development of atherosclerosis through different mechanisms. Some microorganisms, such as Chlamydia pneumoniae (C. pneumoniae), human cytomegalovirus, etc. may act directly on the arterial wall contributing to endothelial dysfunction, foam cell formation, smooth muscle cell proliferation, platelet aggregation as well as cytokine, reactive oxygen specie, growth factor, and cellular adhesion molecule production. Others, such as Helicobacter pylori (H. pylori), influenza virus, etc. may induce a systemic inflammation which in turn may damage the vascular wall (e.g., by cytokines and proteases). Moreover, another indirect mechanism by which some infectious agents (such as H. pylori, C. pneumoniae, periodontal pathogens, etc.) may play a role in the pathogenesis of atherosclerosis is molecular mimicry. Given the complexity of the mechanisms by which each microorganism may contribute to atherosclerosis, defining the interplay of more infectious agents is far more difficult because the pro-atherogenic effect of each pathogen might be amplified. Clearly, continued research and a greater awareness will be helpful to improve our knowledge on the complex interaction between the infectious burden and atherosclerosis.

Chlamydia pneumoniae infection and cerebrovascular disease: a systematic review and meta-analysis

Background

A wealth of published studies have been published on association between Chlamydia pneumoniae (C.pneumoniae) infection and cerebrovascular (CV) disease, but the results were inconsistent. This meta-analysis provides a systematic review of the available evidence from all serological and pathological studies of CV disease and C.pneumoniae.

Methods

A comprehensive research was conducted of MEDLINE, EMBASE, CNKI, WanFang technological periodical database and reference lists of articles to identify eligible case-control and cohort studies. Odds radio (OR) was calculated for each study outcome. Random effect model was used as pooling method and publication bias was estimated for the results.

Results

Fifty-two published studies that met criteria were selected. In case control studies, an association between C.pneumoniae infection and CV disease was revealed by serum specific IgG (OR, 1.61; 95% CI: 1.34 to 1.94), serum IgA (OR, 2.33; 95% CI: 1.76 to 3.08) and PCR technique of C.pneumoniae in peripheral blood cells (OR, 1.90; 95% CI: 1.17 to 3.07). No significant association was found in serum anti-C.pneumonae IgM seropositivity or in-situ-detection of C.pneumoniae in arterial biopsies with CV disease. Subgroup analysis by available studies suggested that C.pneumoniae may paly a role in atherosclerotic stroke, but be less significant in stroke of cardioembolism or other etiologies.

Conclusion

Association between C.pneumoniae infection and CV disease depends on the analytical method adopted, which seems stronger with stroke due to large artery atherosclerosis. Establishing a causal relationship between C.peumoniae infection and CV disease will require more prospective studies with combination of techniques and stratified by etiological subtypes.

The Elusive but Pathogenic Peptidoglycan of Chlamydiae

Chlamydia species cause a broad spectrum of diseases in humans including severe chronic sequelae related to persistent forms. Despite the lack of detectable amounts of peptidoglycan, several studies suggest the presence of small quantities of peptidoglycan or its derivative at least in some stages of the growth cycle. Based on recent discovery in Chlamydiae of the aminotransferase pathway for biosynthesis of meso-diaminopimelic acid, we demonstrated the up-regulation of the gene (cp0259) encoding L,L-diaminopimelate aminotransferase in chlamydial persistent forms. This finding may be important in the search for target molecules to diagnose and treat Chlamydia-associated chronic diseases.

Chlamydophila pneumoniae Infection and Its Role in Neurological Disorders

Chlamydophila pneumoniae is an intracellular pathogen responsible for a number of different acute and chronic infections. The recent deepening of knowledge on the biology and the use of increasingly more sensitive and specific molecular techniques has allowed demonstration of C. pneumoniae in a large number of persons suffering from different diseases including cardiovascular (atherosclerosis and stroke) and central nervous system (CNS) disorders. Despite this, many important issues remain unanswered with regard to the role that C. pneumoniae may play in initiating atheroma or in the progression of the disease. A growing body of evidence concerns the involvement of this pathogen in chronic neurological disorders and particularly in Alzheimer's disease (AD) and Multiple Sclerosis (MS). Monocytes may traffic C. pneumoniae across the blood-brain-barrier, shed the organism in the CNS and induce neuroinflammation. The demonstration of C. pneumoniae by histopathological, molecular and culture techniques in the late-onset AD dementia has suggested a relationship between CNS infection with C. pneumoniae and the AD neuropathogenesis. In particular subsets of MS patients, C. pneumoniae could induce a chronic persistent brain infection acting as a cofactor in the development of the disease. The role of Chlamydia in the pathogenesis of mental or neurobehavioral disorders including schizophrenia and autism is uncertain and fragmentary and will require further confirmation.

Chlamydia pneumoniae and atherosclerosis: current state and future prospectives

Chlamydia pneumoniae, an intracellular bacterial pathogen, is known as a leading cause of human respiratory tract infections worldwide. Over the last decade, several reports in the literature have suggested that infection with C. pneumoniae may contribute to the pathogenesis of atherosclerosis. In order to play a causative role in chronic disease, C. pneumoniae would need to persist within infected tissue for extended periods of time, thereby stimulating a chronic inflammatory response. C. pneumoniae has been shown to disseminate systemically from the lungs through infected peripheral blood mononuclear cells and to localize in arteries where it may infect endothelial cells, vascular smooth muscle cells, monocytes/macrophages and promote inflammatory atherogenous process. The involvement of C. pneumoniae in atherosclerosis was investigated by seroepidemiological and pathological studies, in vivo and in vitro studies, and in clinical antibiotic treatment trials. This review will provide an update on the role of C. pneumoniae in atherosclerosis focusing on the recent insights and suggesting areas for future research.

Chlamydia pneumoniae encodes a functional aromatic amino acid hydroxylase

Chlamydia pneumoniae is a community-acquired respiratory pathogen that has been associated with the development of atherosclerosis. Analysis of the C. pneumoniae genome identified a gene (Cpn1046) homologous to eukaryotic aromatic amino acid hydroxylases (AroAA-Hs). AroAA-Hs hydroxylate phenylalanine, tyrosine, and tryptophan into tyrosine, dihydroxyphenylalanine, and 5-hydroxytryptophan, respectively. Sequence analysis of Cpn1046 demonstrated that residues essential for AroAA-H enzymatic function are conserved and that a subset of Chlamydia species contain an AroAA-H homolog. The chlamydial AroAA-Hs are transcriptionally linked to a putative bacterial membrane transport protein. We determined that recombinant Cpn1046 is able to hydroxylate phenylalanine, tyrosine, and tryptophan with roughly equivalent activity for all three substrates. Cpn1046 is expressed within 24 h of infection, allowing C. pneumoniae to hydroxylate host stores of aromatic amino acids during the period of logarithmic bacterial growth. From these results we can conclude that C. pneumoniae, as well as a subset of other Chlamydia species, encode an AroAA-H that is able to use all three aromatic amino acids as substrates. The maintenance of this gene within a number of Chlamydia suggests that the enzyme may have an important role in shaping the metabolism or overall pathogenesis of these bacteria.

Presence of Chlamydophila pneumoniae DNA but not mRNA in stenotic aortic heart valves

BACKGROUND

The pathogenesis of aortic valve stenosis may involve inflammation and we have previously demonstrated Chlamydophila pneumoniae (C. pneumoniae) DNA in stenotic aortic heart valves. Dissemination of these bacteria is probably mediated by alveolar macrophages. Bacterial DNA alone does not indicate whether the bacteria are viable and replicating. This study aimed to investigate the presence of C. pneumoniae mRNA, a marker of replicating bacteria, and C. pneumoniae DNA in stenotic aortic valves and the prevalence of C. pneumoniae in peripheral blood mononuclear cells (PBMC).

METHODS

DNA was extracted from heart valves and PBMC and mRNA from heart valves from 76 patients undergoing aortic valve replacement surgery. C. pneumoniae DNA and mRNA were measured by real-time PCR targeting the ompA gene.

RESULTS

C. pneumoniae DNA was demonstrated in 22% of heart valves and in 5% of PBMC. C. pneumoniae mRNA was not detected in any valve. Patients positive for C. pneumoniae in the valve underwent coronary artery by-pass grafting more often (p=0.01) and suffered from angina pectoris (p=0.02) and arterial hypertension (p=0.03) more often than patients negative for C. pneumoniae in the valve.

CONCLUSIONS

These findings support a role for C. pneumoniae in the pathogenesis of aortic valve stenosis and indicate that the bacteria disseminate from the respiratory tract long before the patients were in need of surgery and that the valve infection thereafter entered into a persistent and non-replicative state. Moreover, patients positive for C. pneumoniae in the valve more often needed by-pass grafting because of more advanced coronary disease.

Chlamydia Pneumoniae and Chronic Diseases with a Great Impact on Public Health

Chlamydia pneumoniae is recognised as a common cause of respiratory tract infections and has recently been implicated in several extrapulmonary chronic diseases, with great impact on public health, such as atherosclerosis, multiple sclerosis and Alzheimer's disease. The involvement of C. pneumoniae in such diseases may be correlated to characteristic features of this pathogen, including intracellular growth and ability to induce persistent forms. C. pneumoniae persistent forms are inherently more suited to evade the host immune response and are more difficult to eradicate by antibiotics. Our preliminary experimental findings show that interaction of C. pneumoniae with macrophages and/or T cells characterized by interference with TNF-α production, and redox state, culminates in the induction of T cell apoptosis and survival of infected macrophages. Based on our evidence, the poor cooperation between T cells and macrophages could lead to an inappropriate immune response against C. pneumoniae that may therefore promote the development of extrapulmonary chronic diseases.

No evidence of involvement of Chlamydia pneumoniae in lung cancer by means of quantitative real-time polymerase chain reaction

Chlamydia pneumoniae, an obligate intracellular pathogen, is well-known as etiological agent of acute respiratory infections; the repeated or prolonged exposure to chlamydial antigens may promote the persistence of C. pneumoniae in the respiratory tract leading to chronic diseases, such as chronic obstructive pulmonary disease and asthma. The predilection of C. pneumoniae to cause respiratory tract infections combined with its persistent nature suggest that it might play a role in lung cancer. The aim of our study is to evaluate the involvement of C. pneumoniae in pathogenesis of lung cancer. We therefore investigated the presence of C. pneumoniae DNA in tumor lung tissues by using real-time PCR assay. Simultaneously, tumor and healthy tissues from the same patient with primary carcinoma lung were analyzed. C. pneumoniae DNA was not detected in a single lung tumor tissue by means of an highly sensitive, and specific real-time PCR assay based on FRET hybridization probes. In conclusion, this study does not support the involvement of C. pneumoniae in the pathogenesis of lung cancer, suggesting that further investigations are needed to clarify other potential causative factors for the development of this malignancy.

Limited role for C. pneumoniae, CMV and HSV-1 in cerebral large and small vessel atherosclerosis

Aims: To explore whether Chlamydia pneumoniae, Cytomegalovirus and Herpes Simplex Virus type 1 could be detected in large and small cerebral arteries, as well as in an area of brain parenchyma where white matter lesions (leukoaraiosis) can be found, in patients with clinically unmanifested cerebrovascular atherosclerosis. Methods and results( Arterial specimens from the basilar artery and middle cerebral artery, and brain samples from the basal ganglia and periventricular white matter were obtained. Neuropathological changes were assessed in Haematoxylin-Eosin stained sections. Polymerase chain reaction (PCR) was performed on paraffin embedded sections. Subsequently, we performed immunohistochemical staining on samples, which were found positive in PCR. We failed to detect C. pneumoniae, CMV, or HSV-1, in any of the cerebral large vessels. In the brain tissue, we found only one case positive for CMV, and one for C. pneumoniae. Conclusions (our findings suggest a limited role for C. pneumoniae, CMV and HSV-1 in cerebral large and small vessel atherosclerosis.

Role of Chlamydia pneumoniae in atherosclerosis

Cardiovascular disease, resulting from atherosclerosis, is a leading cause of global morbidity and mortality. Genetic predisposition and classical environmental risk factors explain much of the attributable risk for cardiovascular events in populations, but other risk factors for the development and progression of atherosclerosis, which can be identified and modified, may be important therapeutic targets. Infectious agents, such as Chlamydia pneumoniae, have been proposed as contributory factors in the pathogenesis of atherosclerosis. In the present review, we consider the experimental evidence that has accumulated over the last 20 years evaluating the role of C. pneumoniae in atherosclerosis and suggest areas for future research in this field.

Comparison of polymerase chain reaction methods, in situ hybridization, and enzyme immunoassay for detection of Chlamydia pneumoniae in atherosclerotic carotid plaques

Chlamydia pneumoniae has been associated with cardiovascular diseases and has been shown by different methods to be present in atherosclerotic lesions. However, not all studies have found C. pneumoniae in atherosclerotic tissues. We compared polymerase chain reaction (PCR) methods, in situ hybridization (ISH), and measurement of chlamydial lipopolysaccharide (cLPS) by enzyme immunoassay (EIA) from homogenized atherosclerotic tissue in the detection of C. pneumoniae. In a study population of 110 patients with carotid artery disease, cLPS was found in 22.2%, and DNA by PCR was found in 34.3% and by ISH in 39.4% of the samples. Poor repeatability was shown to complicate PCR, and the technical problems inherent in ISH were not insignificant. In contrast, the cLPS EIA test was fast and easy to perform. If the sensitivity could be increased, for example, by testing multiple tissue pieces, cLPS EIA might provide a standardized commercial method for the detection of chlamydia in tissue samples, and it, thus, merits further characterization and validation in different patient populations.

Measurement of Chlamydia pneumoniae bacterial load in peripheral blood mononuclear cells may be helpful to assess the state of chlamydial infection in patients with carotid atherosclerotic disease

BACKGROUND

Chlamydia pneumoniae has been repeatedly associated with atherosclerotic cardiovascular diseases. We investigated the pattern of distribution of C. pneumoniae among patients with carotid atherosclerotic disease evaluating chlamydial load in carotid plaque, peripheral blood mononuclear cells (PBMC) and lymph node from same patient.

METHODS AND RESULTS

Thirty carotid plaques, 30 PBMC and 30 lymph nodes were examined by real-time PCR assay. C. pneumoniae DNA was detected, in carotid plaques, PBMC and lymph nodes in 11 patients; in carotid plaques and PBMC in five patients; in PBMC and lymph nodes in four patients; in lymph nodes in two patients; and in PBMC only in one patient. C. pneumoniae DNA in PBMC significantly coincided with the presence of the respective DNA in carotid plaque (p=0.0001) and lymph node (p=0.02). A higher chlamydial load was detected in PBMC than in lymph nodes and carotid plaques. More than 90% of patients with carotid plaques, PBMC and lymph nodes positive to C. pneumoniae were symptomatic, smokers, hypertensives, dyslipidemics and showed carotid plaques with rupture on the surface, hemorrhage and thrombosis.

CONCLUSION

The measurement of chlamydial load in PBMC may be helpful in the future to assess the state of C. pneumoniae infection and the risk of developing sequelae.

No detectable Chlamydia pneumoniae and cytomegalovirus DNA in leukocytes in subjects with echolucent and echogenic carotid artery plaques

BACKGROUND

Controversy exists whether persistent Chlamydia pneumoniae or cytomegalovirus infections cause initiation or progression of atherosclerosis. C. pneumoniae DNA in peripheral blood mononuclear cells (PBMC) has been proposed to be a more reliable marker of cardiovascular risk than are C. pneumoniae antibodies. Reported prevalences of C. pneumoniae DNA among cardiovascular patients vary greatly, indicating methodological limitations. There is an increasing concern that published results may have been biased by extensive use of less specific polymerase chain reaction (PCR) technology.

METHODS

C. pneumoniae DNA and cytomegalovirus DNA were determined by probe-based real-time PCR technology in PBMCs among subjects with echolucent (n=29) or echogenic (n=28) carotid artery plaques, and in controls without carotid plaques (n=38), all recruited from a population-based study. Samples were examined in multiple repeats with PCR assays targeting two different sequences of the genome for both microorganisms.

RESULTS AND CONCLUSION

IgG seropositivity was frequent in all three groups, confirming previous exposure, but C. pneumoniae DNA or cytomegalovirus DNA was not detected in a single PBMC sample by means of probe-based, highly sensitive, and specific real-time PCR assays. Our results indicate that persistent C. pneumoniae or CMV infection is not a common phenomenon in subjects with carotid atherosclerosis.

The association of carotid plaque inflammation and Chlamydia pneumoniae infection with cerebrovascular symptomatology

OBJECTIVE

Inflammation and infection have been implicated in the pathogenesis of carotid artery atherosclerosis, but their role in cerebrovascular disease symptomatology is not so well defined. We hypothesized that carotid disease symptomatology was associated with specific serologic markers of inflammation and Chlamydia pneumoniae infection and the presence of the pathogen and concentration of tumor necrosis factor-alpha (TNF-alpha) on the atheroma.

METHODS

In 2004, 78 patients underwent carotid endarterectomy in our department, 46 of whom were symptomatic (group A) and 32 were asymptomatic (group B). A detailed medical history, the presence of atherosclerosis risk factors, ankle-brachial index and boxy mass index were recorded. We measured preoperatively the levels of C-reactive protein, fibrinogen, TNF-alpha, and the titers of immunoglobulin (Ig) A and IgG antibodies against C pneumoniae in the serum. Finally, the atherosclerotic plaques of all patients were immunohistochemically examined for the presence of C pneumoniae and their TNF-alpha concentration was determined.

RESULTS

Isolation of the pathogen on the atheromatous lesion was statistically correlated with several risk factors and some of the variables that were tested. After testing independence of association, using the multiple regression analysis, only male gender (P = .024), hypertension (P = .008), hypercholesterolemia (P = .001), and TNF-alpha plaque values (P = .008) remained significantly associated. Hypertension, serum levels of fibrinogen and anti-C pneumoniae immunoglobulin A, detection of C. pneumoniae on the plaque, and plaque TNF-alpha values were significantly correlated with carotid disease symptomatology. After multiple analyses, only the presence of the pathogen on the lesion (P = .008) and atheroma TNF-alpha levels (P = .025) remained significantly associated with cerebrovascular events.

CONCLUSIONS

It seems that hypertensive hypercholesterolemic men are more likely to have C. pneumoniae infected carotid plaques and that these plaques have higher TNF-alpha concentrations. Cerebrovascular disease symptomatology is strongly correlated with both C. pneumoniae infection and TNF-alpha concentration of the atheroma.

Circulating Chlamydia pneumoniae DNA and advanced coronary artery disease

BACKGROUND

Chlamydia pneumoniae (C. pneumoniae) has been linked to atherosclerosis. Detection of this pathogen in peripheral blood cells may be valuable in the diagnosis of disease state. This study aimed to evaluate the prevalence of circulating C. pneumoniae DNA and its relationship with severity and extent of coronary artery disease (CAD).

METHODS

Blood samples from 269 patients undergoing coronary angiography were collected. The presence of circulating C. pneumoniae DNA was determined by real-time PCR assay. Data regarding coronary risk factors and severity and extent of CAD were collected. Severity and extent of CAD was defined by the number of major epicardial coronary arteries with >50% stenosis and by the Duke jeopardy score.

RESULTS

Sixteen of 269 specimens (5.9%) from the study cohort were positive for C. pneumoniae DNA. Thirteen specimens among 149 samples from patients with multi-vessel disease (8.7%) were positive for C. pneumoniae DNA compared with 3 of 120 (2.5%) among patients without multi-vessel CAD. The prevalence of circulating C. pneumoniae DNA was significantly associated with multi-vessel disease. The odds ratio was 5.1 (P=0.02) after adjustment for conventional risk factors.

CONCLUSIONS

Presence of circulating C. pneumoniae DNA is associated with advanced CAD, suggesting C. pneumoniae infection as a contributing factor to progression of coronary atherosclerosis.

Chlamydia pneumoniae and vascular disease: an update

Exposure to Chlamydia pneumoniae is extremely common, and its incidence increases with age. C pneumoniae infection is strongly associated with coronary artery disease, as well as with atherosclerosis of the carotid artery, aorta, and peripheral arteries. This association has been shown in seroepidemiologic studies and by direct detection of the organism in atherosclerotic lesions by immunohistochemistry, polymerase chain reaction, electron microscopy, and tissue culture. Animal models of atherosclerosis have been used to study the role of C pneumoniae in the initiation and progression of atherosclerotic disease. The association of this organism with cardiovascular complications has inspired many human trials of antibiotics for the secondary prevention of atherosclerosis. C pneumoniae can infect several types of cells, including circulating macrophages, arterial smooth muscle cells, and vascular endothelial cells, causing the secretion of proinflammatory cytokines and procoagulants by endothelial cells and foam cell formation by infected macrophages. This report reviews the role of C pneumoniae in atherogenesis in light of recent, large antibiotic treatment trials, animal studies, and in vitro studies. The role of Chlamydia heat shock protein as a potential mediator of this harmful effect is also reviewed.

Descripción de inmunógenos de Chlamydia pneumoniae reconocidos por el suero de sujetos con enfermedad arterial periférica

BACKGROUND AND OBJECTIVE

The relationship between antibodies to C. pneumoniae and presence of the bacteria was studied in individuals with peripheral arterial disease.

PATIENTS AND METHOD

An observational analytical, case-control study was performed in 118 patients (68 cases, 50 controls) to investigate immunoglobulin (Ig) G and A against C. pneumoniae in serum, using Western-blot (commercial and no commercial methods), ELISA and MIF; DNA of the bacteria in vascular tissue biopsy specimens was studied by polymerase chain reaction.

RESULTS

Using commercial Western-blot, significant presence of IgG anti-39 kDa and anti-54 kDa was found in cases and was related to MIF results and C. pneumoniae DNA findings; IgA anti-LPS, anti-92 kDa and anti-Hsp60 kDa were also found and related to DNA presence. Using no commercial Western-blot, significant presence of 128.8 and 9.2 kDa bands for IgG was detected in cases and associated with DNA presence; 70.8, 58.9, 47.9, 47.5, 18.4, 12.1, 10.6, 8.1, and 7.6 kDa bands for IgG were found in cases; and DNA was present when 54.6 and 1.1 kDa bands for IgG and 79.4, 50.1, and 18.4 kDa bands for IgA were also detected.

CONCLUSIONS

Using Western-blot, a greater serologic response was found against certain proteins of the bacteria in individuals with peripheral arterial disease. This may reflect an initial stage with presence of DNA and specific IgG. Subsequently, even in absence of the bacteria, an immunomediated disease may develop with presence of IgA and IgG.

Could Chlamydia Pneumoniae Be Considered an Infectious Risk Factor for Inflammatory Diseases Such as Atherosclerosis ?

Chlamydia pneumoniae, a Gram-negative intracellular obligate bacteria, is recognised as a common cause of upper respiratory tract infections, and accounts for ∼10% of community-acquired pneumonia. In recent years, chronic and persistent infection with C. pneumoniae has been implicated in the pathogenesis of atherosclerosis. Atherosclerosis is regarded as a chronic inflammatory disease that results from complex interactions between a variety of cell types such as endothelial cells, vascular smooth muscle cells, monocytes/macrophages and inflammatory mediators. Involvement of C. pneumoniae in the pathogenesis of atherosclerosis has been supported by findings from seroepidemiologic studies, direct detection of chlamydial DNA, experimental animal and in vitro studies, and antibiotic intervention trials. The spectrum of cell biological, animal, and human clinical data suggests that C. pneumoniae may be considered an infectious risk factor for atherosclerosis but further studies are needed to clarify the etiopathogenetic role of C. pneumoniae in atherosclerotic vessel walls.

Oral bacteria in the occluded arteries of patients with Buerger disease

OBJECTIVE

Recent studies have suggested that infectious organisms play a role in vascular diseases. In this study, to explore a possible link between oral infection and Buerger disease, we investigated whether oral (periodontal) bacteria were present in occluded arteries removed from patients with characteristic Buerger disease.

METHODS

Fourteen male patients with a smoking history who had developed characteristics of Buerger disease before the age of 50 years were included in this study. Occluded arteries, including superficial femoral (n = 4), popliteal (n = 2), anterior tibial (n = 4), and posterior tibial (n = 4) arteries, were removed and studied. A periodontist performed a periodontal examination on each patient and collected dental plaque and saliva samples from them at the same time. The polymerase chain reaction method was applied to detect whether seven species of periodontal bacteria--Porphyromonas gingivalis, Tannerella forsythensis, Treponema denticola, Campylobacter rectus, Actinobacillus actinomycetemcomitans, Prevotella intermedia , and Prevotella nigrescens--were present in the occluded arteries and oral samples. In addition, arterial specimens from seven control patients were examined by polymerase chain reaction analysis.

RESULTS

DNA of oral bacteria was detected in 13 of 14 arterial samples and all oral samples of patients with Buerger disease. Treponema denticola was found in 12 arterial and all oral samples. Campylobacter rectus, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, and Prevotella nigrescens were found in 14% to 43% of the arterial samples and 71% to 100% of the oral samples. A pathologic examination revealed that arterial specimens showed the characteristics of an intermediate-chronic-stage or chronic-stage lesion of Buerger disease. All 14 patients with Buerger disease had moderate to severe periodontitis. None of the control arterial samples was positive for periodontal bacteria.

CONCLUSIONS

This is the first study to identify oral microorganisms in the lesions of Buerger disease. Our findings suggest a possible etiologic link between Buerger disease and chronic infections such as oral bacterial infections.

Discordant detection of Chlamydia pneumoniae in patients with carotid artery disease using polymerase chain reaction, immunofluorescence microscopy and serological methods

AIM

To determine the presence of Chlamydia pneumoniae in carotid plaque and peripheral blood mononuclear cells (PBMCs) using a combination of serology, direct antigen detection by immunofluorescence (IF) microscopy and polymerase chain reaction (PCR), and to compare the results obtained from each assay.

METHODS

A total of 54 atherosclerotic carotid plaques were tested for the presence of Chlamydia by PCR and IF methods. Of these 54 patients with carotid artery disease (CAD), 43 were also tested for the presence of C. pneumoniae DNA in PBMCs and for Chlamydia antibodies using two methods, the Medac Chlamydien rELISA and Focus Chlamydia microimmunofluorescence (MIF) methods.

RESULTS

Eighteen of the 54 (33%) carotid specimens were positive for the presence of C. pneumoniae DNA, whereas only two of 43 (5%) patients had C. pneumoniae DNA present within their PBMC fraction. Chlamydial antibodies were detected by MIF and/or rELISA in 56% (24/43) of the patients tested. None of the 43 patients was C. pneumoniae positive in all of the test specimens (plaque, PBMCs and serum).

CONCLUSIONS

Chlamydia pneumoniae is commonly found in Australian patients with CAD. Serology and PCR-based detection of C. pneumoniae in PBMCs and plaque give highly discordant results.

Detection of Chlamydia pneumoniae in atherosclerotic coronary arteries

Chlamydia pneumoniae has recently been associated with the development of coronary heart diseases by sero-epidemiological studies and by direct detection of the organism in atherosclerotic tissues. The aim of our study was to employ a semi-nested PCR approach to investigate the presence of C. pneumoniae in both normal and atherosclerotic coronary arteries of humans obtained at autopsy. Moreover, we have evaluated the role of infection with C. pneumoniae in relation to the extent of coronary atherosclerosis. One hundred and eighty coronary artery specimens were collected at autopsy from 60 consecutive subjects (three arterial segments from each subject). Atherosclerosis in each arterial segment was graded histologically by the Stary classification. Thirty normal coronary arteries were also taken at autopsy as control. PCR results evidenced the presence of C. pneumoniae DNA in atherosclerotic coronary arteries in 19 (31.7%) of 60 subjects examined, while none of the 30 subjects with non-atherosclerotic tissues was positive (p=0.001). Moreover, of the 180 atherosclerotic specimens examined, C. pneumoniae DNA was detected in 3.4% (2/59) of mild atherosclerotic lesions, and in 14.0% (17/121) of advanced atherosclerotic lesions (p=0.05). Our results demonstrate that the presence of C. pneumoniae DNA may be associated with the severity of coronary atherosclerosis.

Genomic, serologic, and clinical case-control study of Chlamydia pneumoniae and peripheral artery occlusive disease

OBJECTIVES

Chlamydia pneumoniae has been related to atherosclerotic disease in both seroepidemiologic and genomic studies. We performed a case-control study to determine seropositivity and DNA detection in arteries of patients with peripheral artery occlusive disease and of healthy subjects.

METHODS

The study included 64 patients with peripheral artery occlusive disease, and 50 control subjects who underwent varicose vein surgery, matched to the patient group for age, sex, and tobacco use. The fibrinogen level in all study subjects was measured as a marker of inflammation. Blood samples were taken from all subjects for determination of immunoglobulin (Ig) G elementary bodies (EB) against C pneumoniae with microimmunofluorescence (MIF) and enzyme-linked immunosorbent assay (ELISA), and of IgA EB with ELISA. The cutoff titers were 1:32 for MIF and 1.1 for ELISA. Biopsy specimens of arterial atheromatous plaque were obtained from patients, and of pudendal artery and saphenous vein from control subjects, and were studied with hemi-nested polymerase chain reaction.

RESULTS

There were no differences in fibrinogen level between patients and controls. The prevalence of IgG anti-EB with MIF was 78% in patients and 24% in control subjects (P =.0001; odds ratio [OR], 11.3; 95% confidence interval [CI], 4.7-27.2). Prevalence of IgG anti-EB with ELISA was 75% in patients and 16% in control subjects (P =.0001; OR, 15.7; 95% CI, 6.1-40). There were no differences in IgA anti-EB titers. Bacterial DNA was detected in 67% of atheromatous plaques versus 12% of pudendal arteries (P =.0001) and 4% of saphenous veins. A weak correlation was found between seropositivity and the presence of intravascular DNA.

CONCLUSIONS

Our results support the hypothesis that C pneumoniae is related to the pathogenesis of atherosclerotic peripheral artery occlusive disease.

CLINICAL RELEVANCE

This study explored the infectious hypothesis in the context of the pathogenesis of atherosclerosis. This hypothesis has been supported by findings that certain infectious agents can cause or accelerate the course of diseases in which the possibility of a microbial cause was not previously proposed, as in the case of peptic ulcer and spongiform encephalopathy. The present study demonstrated the presence of Chlamydia pneumoniae and seropositivity in atheromatous plaques in patients with peripheral artery occlusive disease. These results contribute to a body of research that is opening up the possibility of treating atherosclerotic disease with antibiotic agents, and preventing it with immunization.

Association of Peripheral Mononuclear Cells Containing Chlamydia Pneumoniae DNA with Acute Coronary Syndrome and Stable Coronary Artery Disease in Japanese Subjects

To clarify the association of Chlamydia pneumoniae DNA in peripheral blood mononuclear cells (PBMCs) with acute coronary syndrome (ACS) and stable coronary artery disease (CAD) in Japanese adults, touchdown-nested polymerase chain reaction was used to detect the presence of C. pneumoniae DNA. The prevalence of C. pneumoniae DNA in PBMCs was similar in a comparison of 88 patients (52.3%) with ACS, 164 patients (50.0%) with stable CAD, and 88 control subjects (50.0%). Temporal changes in the prevalence of C. pneumoniae DNA in PBMCs were also assessed every 3 months during a 1-year period (n=59). The prevalence was significantly higher in the first 3-month period (January through March) than in any of the other 3-month periods. In conclusion, the prevalence of C. pneumoniae DNA in PBMCs in patients with ACS or stable CAD was comparable to that in control populations. Furthermore, the presence of circulating C. pneumoniae was strongly associated with seasonal variability.

No evidence of involvement of Chlamydia pneumoniae in severe cerebrovascular atherosclerosis by means of quantitative real-time polymerase chain reaction

BACKGROUND AND PURPOSE

All studies reporting high numbers of Chlamydia pneumoniae DNA positives in stroke patients published to date have used polymerase chain reaction (PCR) techniques highly prone to generate false-positive results. The aim of this study was to analyze the prevalence of C. pneumoniae DNA in plaques of the carotid artery as well as in peripheral blood by means of a new, closed, real-time PCR system.

METHODS

Carotid endarterectomy specimens and preoperative peripheral blood mononuclear cells (PBMC) of 75 individuals with severe cerebrovascular atherosclerosis were analyzed by means of a C. pneumoniae-specific quantitative ompA-based real-time PCR TaqMan system. Plaques were also cultured onto HEp-2 cells. Before the surgical intervention, C. pneumoniae-specific IgM, IgG, and IgA as well as C-reactive protein (CRP) levels were determined.

RESULTS

89% of all patients studied had C. pneumoniae-specific antibodies, but the pathogen was not detected in a single carotid atheroma by real-time PCR and cell culture. However, C. pneumoniae DNA was detected in 4 PBMC samples (5.3%) at very low levels (<1 inclusion/6 mL EDTA blood). No statistical significance was found between symptomatic/asymptomatic patients, C. pneumoniae PCR, results and CRP values after correction for multiplicity-of-test adjustment.

CONCLUSIONS

By means of a closed, highly sensitive, and specific real-time PCR, C. pneumoniae was not detected in cerebrovascular atherosclerosis. PCR on PBMC was not predictive for endovascular chlamydia infection and most likely stem from previous C. pneumoniae respiratory tract infection in individual cases.