Circulating Chlamydia pneumoniae DNA as a predictor of coronary artery disease

Chlamydia PneumoniaeDNA in Peripheral Blood Mononuclear Cells in Peritoneal Dialysis Patients

Objective

The aim of the present study was to examine the association between infection with Chlamydia pneumoniae and symptomatic atherosclerosis in peritoneal dialysis (PD) patients.

Design

Cross-sectional study.

Setting

Peritoneal Dialysis Unit of Kingston General Hospital.

Patients

Fifty-five prevalent PD patients.

Outcome Measures

( 1 ) Infection with C. pneumoniae diagnosed by detection of DNA in peripheral blood mono-nuclear cells (PBMCs) using polymerase chain reaction. ( 2 ) Symptomatic atherosclerosis involving the coronary, cerebral, or peripheral circulation.

Results

The DNA of C. pneumoniae was detected in PBMCs in 33 patients (60.0%). Atherosclerosis was present in 16 of 33 (48%) PBMC C. pneumoniae DNA–positive patients, and in 10 of 22 (45%) PBMC C. pneumoniae DNA–negative patients ( p = 0.83). Using multiple logistic regression and controlling for a number of known cardiovascular risk factors, PBMC C. pneumoniae DNA status was not predictive of atherosclerosis. The only significant independent predictors of atherosclerosis were diabetes and age.

Conclusions

In prevalent PD patients, a high prevalence of symptomatic atherosclerosis and of Chlamydia pneumoniae DNA in PBMCs were seen; however, the results of the present study do not support the presence of an association between infection with C. pneumoniae and atherosclerosis.

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 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.

Comparison of Five PCR Assays for DetectingChlamydophila pneumoniaeDNA

We compared five different polymerase chain reaction (PCR) assays for the detection of Chlamydophila pneumoniae DNA using highly purified elementary bodies (EBs) and peripheral blood mononuclear cells (PBMCs) from healthy blood donors. The primers were as follows; two targeting the 16S rRNA gene, one targeting the ompA gene, one targeting the Pst-I gene, and one targeting the 53 kDa outer membrane protein gene. The 16S rRNA touchdown enzyme time release (TETR) PCR, the ompA nested PCR and the 53 kDa nested PCR were the most sensitive assays and could detect one or more EB per assay. These three PCRs also had the same reproducibility, but the minimal amount of C. pneumoniae that could be reproducibly detected (10 of 10 testing positive) was 20 EBs. In a sample of specimens from healthy blood donors, we found 5 of 77 (6.5%) PBMCs specimens to have C. pneumoniae DNA according to the nested ompA PCR. Specimens with the 16S rRNA TETR and 53 kDa nested assays were found to have C. pneumoniae DNA 7 of 77 (9.1%) and 18 of 77 (23.4%) specimens, respectively. The other two assays failed to detect even a single positive. However, the detection rate decreased with repeated testing of the same samples. Our newly designed 53 kDa nested PCR may be as useful as the other four recommended PCR assays and may be a more useful assay for the detection of C. pneumoniae DNA from PBMCs.

Atherosclerosis Induced by Chlamydophila pneumoniae: A Controversial Theory

More than a century ago, inflammation and infection were considered to have atherogenic effects. The old idea that coronary heart disease (CHD) possibly has an infectious etiology has only reemerged in recent years. Atherosclerosis is the main pathological process involved in CHD and is, logically, the first place to look for infectious etiology. The process of atherosclerosis itself provides the first hints of potential infectious cause. Smooth muscle proliferation, with subsequent intimal thickening, luminal narrowing, and endothelial degeneration, constitutes the natural history of atherosclerosis, being with the severity and speed of these changes. Both viral and bacterial pathogens have been proposed to be associated with the inflammatory changes found in atherosclerosis. Recently, Chlamydophila pneumoniae (C. pneumoniae) has been implicated as a possible etiologic agent of coronary artery disease and atherosclerosis. New evidence which supports a role for C. pneumoniae in the pathogenesis of atherosclerosis has emerged. C. pneumoniae has been detected in atherosclerotic arteries by several techniques, and the organism has been isolated from both coronary and carotid atheromas. Recent animal models have suggested that C. pneumoniae is capable of inducing atherosclerosis in both rabbit and mouse models of atherosclerosis. Furthermore, human clinical treatment studies which examined the use of antichlamydial macrolide antibiotics in patients with coronary atherosclerosis have been carried out. The causal relationship has not yet been proven, but ongoing large intervention trials and research on pathogenetic mechanisms may lead to the use of antimicrobial agents in the treatment of CHD in the future.

Chlamydia pneumoniae infection in adolescents with type 1 diabetes mellitus

Chlamydia pneumoniae, an intracellular bacterium, is associated with respiratory diseases, reinfectivity and chronic diseases such as cardiovascular disease, hypertension and stroke. The risk of infection is higher and infections are a serious clinical problem in patients with type 1 (insulin-dependent) diabetes mellitus (T1DM). Although diabetes mellitus and hyperglycaemia are considered possible risk factors for various types of aetiological agents, the epidemiological evidence concerning C. pneumoniae infection is scanty. The aim of the present study was to evaluate the impact of glycosylated haemoglobin (HbA1c) levels, an indicator of a hyperglycaemic state, on C. pneumoniae infection and disease chronicity; in addition we compared the duration of diabetes with the occurrence of C. pneumoniae infection. C. pneumoniae blood real time PCR and serology (IgG, IgA and IgM) assays by an ELISA method were performed. C. pneumoniae DNA was detected in 46.5 % [95 % confidence interval (CI) = 35.1-57.9 %] of the patients with T1DM; this prevalence is higher (P<0.05) than in non-diabetic paediatric controls, 10.5 % (95 % CI = 3.6-17.4 %). IgG/IgA C. pneumoniae antibody positivity was significantly (P≤0.05) more common in patients in poor metabolic control (HbA1c >9 %) versus patients in good metabolic control (HbA1c <7 %), suggesting that the metabolic control of the disease is compromised in the patients with T1DM. In conclusion, adolescents with T1DM were more likely to show signs of infection with C. pneumoniae compared with healthy adolescents and the results suggest an increased risk of progressing from an acute C. pneumoniae infection to a chronic form.

Serum chlamydial lipopolysaccharide as a prognostic factor for a new cardiovascular event

BACKGROUND

Infections caused by Chlamydia pneumoniae are considered to participate in inflammatory processes leading to coronary artery disease. After a primary infection, the bacteria remain dormant intracellularly causing a chronic inflammatory stimulus.

MATERIALS AND METHODS

Blood samples were obtained from 235 patients with acute myocardial infarction (AMI) and 108 patients with unstable angina pectoris (UA). We evaluated the prognostic significance of bacterial and viral antibody titers, serum troponin T, C-reactive protein, and chlamydial lipopolysaccharide (cLPS) concentrations during acute coronary syndrome of patients with AMI and UA for cardiovascular death and new UA and AMI that required hospital care during a 6-year follow-up.

RESULTS

Serum cLPS levels correlated with C-reactive protein and serum troponin T concentrations during acute coronary events. Patients with AMI had significantly higher serum concentration of cLPS compared with patients with UA. Enterovirus antibody titers and cholesterol-lowering therapy at admission of the index event were negatively correlated with cLPS concentration (r = -.198, P = .0003 and r = -.26, P = .019, respectively). The presence of circulating cLPS was associated with a hazard ratio of 2.04 for a new cardiovascular event during the follow-up period (P = .006). The area under the curve in the receiver operating graph was .572.

CONCLUSION

cLPS is evidently liberated from the infected atherosclerotic tissue during an acute coronary event. Our study supports the view that inflammation caused by C. pneumoniae infection is an important but as yet poorly understood factor in the development of atherosclerosis and may play a role in acute vascular events.

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.

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.

Isolation of Chlamydophila pneumoniae from atheromas of the carotid artery and their antibiotics susceptibility profile

BACKGROUND

Atherosclerosis is pathogenically similar to a chronic inflammatory response. Peripheral arterial disease (PAD) is a common manifestation of atherosclerosis. Chlamydophila pneumoniae has been suggested to play a role in the origin of PAD.

OBJECTIVE

To determine whether C. pneumoniae is present in atherosclerosis lesions of the carotid artery wall in patients with PAD through several diagnostic methods and to characterize C. pneumoniae susceptibility profiles.

METHODS

The presence of C. pneumoniae in 9 tissue samples from atherosclerotic lesions obtained by carotid endarterectomy was investigated by 3 methods. Karnofsky-fixed specimens were examined by transmission electron microscopy (TEM), isolation of C. pneumoniae was attempted in LLCMK2 cell structure (ICC), and the presence of chlamydial DNA was investigated by polymerase chain reaction (PCR). The in vitro activities of azithromycin, roxithromycin and penicillin were tested in 4 isolations and the reference strain of C. pneumoniae (AR39).

RESULTS

C. pneumoniae was detected in atherosclerotic plaques from 4 patients with PAD. The pathogen was identified by TEM, PCR and ICC. We report data of the in vitro susceptibility of 4 strains. These strains did not differ from respiratory AR39 strain in their susceptibility patterns to azithromycin, roxithromycin and penicillin.

CONCLUSIONS

C. pneumoniae is frequently found in the advanced carotid atherosclerotic lesions of patients undergoing endarterectomy. Although these findings do not establish causality in carotid artery atherosclerosis, they should stimulate investigation of the possible causal or pathogenic role of C. pneumoniae. Notably, the profiles of antibiotic susceptibility of C. pneumoniae isolated from 4 of the patients did not differ from those of the reference strain.

Detection of Chlamydia in the peripheral blood cells of normal donors using in vitro culture, immunofluorescence microscopy and flow cytometry techniques

BACKGROUND

Chlamydia trachomatis (Ct) and Chlamydia pneumoniae (Cp) are medically significant infectious agents associated with various chronic human pathologies. Nevertheless, specific roles in disease progression or initiation are incompletely defined. Both pathogens infect established cell lines in vitro and polymerase chain reaction (PCR) has detected Chlamydia DNA in various clinical specimens as well as in normal donor peripheral blood monocytes (PBMC). However, Chlamydia infection of other blood cell types, quantification of Chlamydia infected cells in peripheral blood and transmission of this infection in vitro have not been examined.

METHODS

Cp specific titers were assessed for sera from 459 normal human donor blood (NBD) samples. Isolated white blood cells (WBC) were assayed by in vitro culture to evaluate infection transmission of blood cell borne chlamydiae. Smears of fresh blood samples (FB) were dual immunostained for microscopic identification of Chlamydia-infected cell types and aliquots also assessed using Flow Cytometry (FC).

RESULTS

ELISA demonstrated that 219 (47.7%) of the NBD samples exhibit elevated anti-Cp antibody titers. Imunofluorescence microscopy of smears demonstrated 113 (24.6%) of samples contained intracellular Chlamydia and monoclonals to specific CD markers showed that in vivo infection of neutrophil and eosinophil/basophil cells as well as monocytes occurs. In vitro culture established WBCs of 114 (24.8%) of the NBD samples harbored infectious chlamydiae, clinically a potentially source of transmission, FC demonstrated both Chlamydia infected and uninfected cells can be readily identified and quantified.

CONCLUSION

NBD can harbor infected neutrophils, eosinophil/basophils and monocytes. The chlamydiae are infectious in vitro, and both total, and cell type specific Chlamydia carriage is quantifiable by FC.

Novel enzyme immunoassay utilizing lipopolysaccharide-binding protein as a capture molecule for the measurement of chlamydial lipopolysaccharide in serum

Chlamydia pneumoniae causes respiratory tract infections. It has a tendency to cause persistent infections, which have been associated with several chronic diseases (e.g., atherosclerosis). At present, there is no reliable method for the diagnosis of chronic C. pneumoniae infection. We developed a novel enzyme immunoassay (EIA) for the quantification of chlamydial lipopolysaccharide (cLPS) in human serum. Serum cLPS was solubilized with detergent and then captured by LPS-binding protein (LBP). LBP-LPS complexes were bound to the solid phase with anti-cLPS monoclonal antibody, and the bound complexes were detected with anti-LBP antibodies. The new method was used to quantify serum cLPS in acute coronary syndrome (ACS) patients (n = 102) and their healthy controls. cLPS was detected in 77.5% of ACS patients and in 52% of controls (P < .001) with geometric mean concentrations of 1.87 and 0.61 microg/mL (P < .001), respectively. The novel cLPS EIA method will provide a potential diagnostic tool for C. pneumoniae infection.

Serum and peripheral blood mononuclear cells infectious burden: Correlation to inflammation and atherosclerosis in haemodialysis patients

BACKGROUND

Infectious agents may be implicated in the inflammatory atherosclerotic process. Not only specific microorganisms but also the infectious burden, defined as the number of pathogens to which a patient is exposed, has been associated with atherosclerosis. In the present study, the infectious burden, determined directly (by identification of viable pathogens in peripheral blood mononuclear cells (PBMC)) and indirectly (by serum antibodies detection) is correlated to the inflammatory and atherosclerotic status in haemodialysis (HD) patients, a population at high risk for cardiovascular disease.

METHODS

The viable forms of four microorganisms (Chlamydia pneumoniae, herpes virus 1 and 2 and cytomegalovirus) were identified in patients PBMC by cell cultures and subsequent polymerase chain reaction. Serum IgG against the above pathogens and Helicobacter pylori were also determined. Inflammation was assessed by measurement of C-reactive protein (CRP), serum amyloid A (SAA), three pro- and one anti-inflammatory cytokines and four adhesion molecules. Atherosclerosis was defined by a scoring system using medical history data.

RESULTS

The number of viable pathogens identified in PBMC in the 122 HD patients included in the study were zero in 22.1% of them, one in 33.6%, two in 43.4% and three in one patient. The number of IgG antibodies determined was one in 6.6% of patients, two in 32%, three in 48.4% and four in 13.1%. Seropositivity was not significantly different between patients with or without the respective viable pathogen identified in PBMC. Atherosclerosis was present in 40.2% of patients, and CRP, SAA and interleukin-6 were all increased in these patients. Neither inflammatory indexes nor atherosclerosis were significantly different in patients with a higher number of viable pathogens detected in PBMC or in those with a higher antibodies number.

CONCLUSIONS

The direct infectious burden determination (the number of viable pathogens in PBMC) does not coincide with the serum (by IgG detection) infectious burden. Although inflammation correlates to atherosclerosis, neither PBMC nor the serum infectious burden is associated with these two entities in the inflamed and atherosclerotic HD patients.

Relation of Chlamydia pneumoniae infection to documented coronary artery disease in Shiraz, Southern Iran

The possibility that infectious agents may trigger a cascade of reactions leading to inflammation, atherogenesis, and vascular thrombotic events has recently been raised. Chlamydia pneumoniae is one of those that have received the most investigative attention with respect to coronary artery disease (CAD). This study was undertaken for the first time in Shiraz, Iran to determine this relationship. A case-control study was conducted in 167 subjects (81 women and 86 men) who underwent coronary angiography at cardiac catheterization laboratories of Shiraz University of Medical Sciences Hospitals. Immunoglobulin G (IgG), and IgA antibodies to C. pneumoniae antigen were estimated in baseline serum samples from 109 patients (mean age 57 years) experiencing a coronary event and from their matched controls (n = 58, mean age 50 years) by ELISA method. The prevalence of IgG and IgA antibodies to C. pneumoniae did not show any case-control differences (82.6% vs 74.1% and 22% vs 15.5%, respectively). These results suggest that although C. pneumoniae was highly prevalent among these patients, it did not appear to be associated with angiographically documented CAD and cannot be regarded as a positive predictor for the development of acute coronary syndrome.

Asymptomatic carotid atherosclerosis is associated with circulating chlamydia pneumoniae DNA in younger normotensive subjects in a general population survey

OBJECTIVE

Chlamydia pneumoniae infection has been associated with atherosclerosis, but serodiagnosis is unreliable in predicting vascular infection. Direct detection of circulating chlamydial DNA in peripheral blood mononuclear cells (PBMCs) was thus evaluated as a marker for cardiovascular risk in a general population survey using the common carotid intima-media thickness (IMT) as surrogate marker of asymptomatic atherosclerosis.

METHODS AND RESULTS

C pneumoniae DNA in PBMCs was determined by nested polymerase chain reaction and associated with IMT for 1032 healthy participants of a general population survey who were within the highest or lowest IMT distribution quartile. C pneumoniae DNA was more prevalent in those with increased IMT (13.4% versus 10.7%), but this was not significant in univariate and of borderline significance in multivariate analysis. Testing for potential effect modifications by known strong determinants of an increased IMT in group interaction analysis revealed an independent association between C pneumoniae DNA and IMT in normotensive subjects (odds ratio [OR], 2.06; 95% CI, 1.05 to 4.03; P=0.04) and in those <70 years old (OR, 1.84; 95% CI, 1.06 to 3.19; P=0.03).

CONCLUSIONS

Asymptomatic atherosclerosis is associated with circulating C pneumoniae DNA independently of classical cardiovascular risk factors in normotensive subjects and those <70 years old. C pneumoniae has been implicated in atherogenesis. We determined the association of chlamydial DNA in peripheral blood mononuclear cells with the carotid intima-media thickness from 1032 healthy subjects from a general population survey. A stratified group interaction analysis revealed an independent association in normotensive subjects and those <70 years old.

Effect of levofloxacin on the viability of intracellular Chlamydia pneumoniae and modulation of proinflammatory cytokine production by human monocytes

Although antibiotics are known to affect the intracellular growth of Chlamydia pneumoniae in acute infections, their efficacy in therapy for chronic infections, including atherosclerosis, remains debatable. Human monocyte-derived macrophages (MDM) obtained from monocytes of healthy donors were infected with C. pneumoniae AR-39 and treated with levofloxacin (8 microg/mL) immediately after infection (0 hours) or 24 hours after infection. Levofloxacin treatment at 24 hours, but not at 0 hours, resulted in a significant decrease in the number of C. pneumoniae inclusions within the MDM (p < 0.05). Also decreased were concentrations of proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, and IL-8 in the extracellular medium (p < 0.01). Viable counts in titrations remained similar to those in untreated controls. In summary, levofloxacin administered to MDM at serum-attainable levels 24 hours after C. pneumoniae infection significantly decreased inclusion counts and proinflammatory cytokine production, but did not eliminate the C. pneumoniae infection.

Cox-2 inhibition abrogates Chlamydia pneumoniae-induced PGE2 and MMP-1 expression

Peripheral blood monocytes (PBMC) promote vascular inflammation and atherosclerosis. Chlamydia pneumoniae (Cp) infection of PBMC is found in atherosclerotic patients, appears refractory to antibiotics, and may predispose to vascular damage. In Cp-infected human PBMC we analyzed the role of cyclooxygenase-2 (Cox-2) for the proatherosclerotic key mediators prostaglandin E2 (PGE2) and interstitial collagenase (MMP-1). Cp infection resulted in rapid and sustained Cox-2 mRNA and protein stimulation depending on p38 and p44/42 MAPkinases. Subsequent upregulation of PGE synthase and MMP-1 was completely abrogated by the selective Cox-2 inhibitor NS398. Enhanced synthesis of PGE2 and MMP-1 in Cp infected PBMC is mediated through initiation of the p38 and p44/42 MAPK pathways and requires sustained Cox-2 activation. Selective Cox-2 inhibitors, currently under investigation for cardiovascular risk reduction, may represent a novel therapeutic option for patients with endovascular Cp infection as they target the actuated pathological signal transduction cascade in persistently infected PBMC.

Chlamydia pneumoniae and Atherosclerosis: No Way-Out or Long Way?

Recently, Chlamydia pneumoniae is the microorganism frequently implicated in the infection-based inflammatory atherogenous hypothesis. Although in vitro experimental data and initial sero-epidemiologic, pathology-based studies and antibiotic trials supported this interesting hypothesis, later data are conflicting. Some confounding factors are the causes of uncertainty; lacking of standard methods for C. pneumoniae detection, co-existence of other atherosclerotic risk factors and anti-inflammatory effects of antibiotics used in clinical trials seem to be the principal ones. Standardization of methodology used, antibiotic trials with a different orientation-design and a vaccine preparation that eventually will be tested in clinical trials with a long follow-up, should provide a definite answer regarding the probability C. pneumoniae to be a main, a secondary or an irrelevant factor to atherosclerosis. Studies linking C. pneumoniae to inflammation and accelerated atherosclerosis in renal failure patients are accumulated but limitations are similar to the above mentioned.

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.

Prevalence of viable Chlamydia pneumoniae in peripheral blood mononuclear cells of healthy blood donors

BACKGROUND

Demonstration of viable Chlamydia (Chlamydophila) pneumoniae in peripheral blood mononuclear cells (PBMNCs) is essential to understand the involvement of C. pneumoniae in atherosclerosis. Nevertheless, the prevalence of viable C. pneumoniae in the blood of healthy donors has not yet been studied.

STUDY DESIGN AND METHODS

The presence of C. pneumoniae transcript in PBMNCs from blood of healthy human donors was assessed by real-time reverse transcription-polymerase chain reaction (RT-PCR) with primers for C. pneumoniae 16S rRNA, which is more sensitive than genomic-DNA-based analysis, and by the use of staining with fluorescein isothiocyanate-conjugated chlamydia monoclonal antibody (MoAb).

RESULTS

Thirteen of 70 donors (18.5%) showed the presence of bacterial transcript in cultured PBMNCs. The prevalence of bacterial detection and bacterial numbers was significantly increased in PBMNC cultures incubated with cycloheximide. Immunostaining of PBMNCs with antichlamydial MoAb also revealed the presence of bacterial antigen in the PBMNCs judged as positive. Nevertheless, cultivation of C. pneumoniae from all PCR-positive donors was unsuccessful. There was no significant correlation between the presence of chlamydia and either sex or current smoking habits. A possible age variation, however, in the presence of chlamydia in blood of healthy donors was suggested by the results obtained.

CONCLUSION

The bacterial transcripts in PBMNCs obtained from healthy donors were detected by the RT-PCR method. Viable C. pneumoniae may be present in healthy human PBMNCs.

Immunohistostaining assays for detection of Chlamydia pneumoniae in atherosclerotic arteries indicate cross-reactions with nonchlamydial plaque constituents

Detection of Chlamydia pneumoniae antigens in PCR-negative atheromata by immunohistochemistry assays has given rise to controversies regarding a link between the bacterium and atherosclerosis. One hundred ninety-seven human arterial segments removed surgically were examined for C. pneumoniae DNA by conventional PCR with three different primer pairs and by real-time PCR in two different laboratories. No C. pneumoniae DNA was detected. Eighty atherosclerotic lesions were studied by immunohistochemistry assays. Immunoreactivity for C. pneumoniae was frequently present but was not related to the extent of atherosclerosis. Mammary arteries showed immunoreactivity. Serial sections of 17 atheromata were analyzed by Western blotting, histological staining, and UV fluorescence microscopy. Chlamydial proteins were not detected. The sites with positive results by C. pneumoniae immunohistostaining assays precisely matched the sites with autofluorescent ceroid deposits. Immunoblotting and antigenic staining for C. pneumoniae were negative in tests with fetal aortas. The absence of C. pneumoniae DNA in human atherosclerotic lesions, together with negative results for C. pneumoniae proteins by Western blotting analysis, and the perfect matching of C. pneumoniae immunoreactive sites with sites with autofluorescent ceroid deposits suggest a nonspecific reactivity of antichlamydial antibodies with plaque constituents. On the basis of the results of the present study, there are no arguments for an etiologic role of C. pneumoniae in atherosclerosis.

Chlamydia pneumoniae infection is associated with coronary artery disease but not implicated in inducing plaque instability

BACKGROUND

Many authors have shown an association between Chlamydia pneumoniae (C. pneumoniae) infection and coronary artery disease. However, whether C. pneumoniae infection plays an important role in triggering an acute coronary event remains to be elucidated.

METHODS

Sixty-four consecutive patients with unstable angina (group A), 56 consecutive patients with stable exertional angina (group B) and 74 control subjects (group C) were studied. The IgM, IgG and IgA anti-C. pneumoniae titers were assessed (microimmunofluorescence test Labsystem), values > or =1:16, > or =1:32 and > or =1:16 being respectively considered positive.

RESULTS

IgM antibodies were found in 10.9% of group A and 12.5% of group B patients, whereas no subject of group C showed IgM titers (A vs. B, p=ns; C vs. A and B, p<0.05). Positive IgG titers were found in 76.6%, 82% and 44.6% in groups A, B and C, respectively (A vs. B, p=ns; C vs. A and B, p<0.05). Positive IgA titers were found in 62.5%, 61% and 31.1% in groups A, B and C, respectively (A vs. B, p=ns; C vs. A and B, p<0.05). Acute infection was observed in 10.9% and 12.5% of patients in groups A and B, respectively (p=ns); reinfection in 17% and 11%; no patient of the control group had signs of acute infection or reinfection. Chronic infection was observed in 34.4% and 37.5% in group A and B, respectively (p=ns).

CONCLUSION

C. pneumoniae infection is associated with coronary artery disease, but no difference in serology is present between unstable and stable angina. Therefore, it does not seem implicated in triggering an acute coronary event.

Association of antibodies to chlamydial lipopolysaccharide with the endovascular presence of Chlamydophila pneumoniae in carotid artery disease

Atherosclerotic lesions often harbor Chlamydophila pneumoniae (C. pneumoniae). The objective of the present study was to examine whether serological tests are able to predict individual endovascular infection. Endarterectomy specimens from 70 patients with severe carotid artery stenosis were stained immunohistochemically for C. pneumoniae. Antibody titers to C. pneumoniae were measured in serum with a recombinant ELISA recognizing chlamydial lipopolysaccharide (cLPS) and with microimmunofluorescence (MIF). C. pneumoniae antigens were detected in 64 (91%) carotid artery specimens. Serum IgG antibodies to C. pneumoniae were detected in 43% of patients by cLPS-ELISA and in 77% by MIF test. Detection of C. pneumoniae positive cells within atherectomy specimens was strongly correlated to seroprevalence (P = 0.002) and to titers (P = 0.003) of cLPS-IgG antibodies, but not to results of the MIF-test. We conclude that cLPS-IgG antibodies hold promise as a surrogate marker to identify individuals with high endovascular antigen load.

Neopterin levels in patients with coronary artery disease are independent of Chlamydia pneumoniae seropositivity

BACKGROUND

Chronic infection with Chlamydia pneumoniae (Cpn) has been associated with atherosclerotic cardiovascular disease in sero-epidemiological, pathological and animal-model studies. Inflammation and immune activation has been proposed as the pathophysiological link between chronic infection and atherosclerosis. The aim of this study was to assess whether Cpn seropositivity is associated with serum neopterin concentrations, a marker of macrophage activation, in patients with stable and unstable angina pectoris.

METHODS

We examined 100 patients with angiographically documented coronary artery disease: 60 patients had chronic stable angina and 40 had Braunwald class III unstable angina. Neopterin concentrations were measured with a commercially available immunoassay. Cpn titres were measured with a microimmunofluorescence (MIF) assay.

RESULTS

Neopterin concentrations were significantly higher in patients with unstable angina compared to those with chronic stable angina (6.30 [4.85-8.80] nmol/L vs 4.95 [3.35-7.05] nmol/L, P =.004), even after adjustment for variables that were significantly different between the 2 groups on univariate analysis. In contrast, the prevalence of positive Cpn serology did not differ significantly between the 2 angina patient groups (65% v 58%, P =.50). Neopterin levels were similar between Cpn-negative and Cpn-positive patients (P =.40) in both stable and unstable angina groups.

CONCLUSIONS

Patients with unstable angina had higher neopterin concentrations than patients with chronic stable angina, probably reflecting the higher degree of immune activation in acute coronary syndromes. Neopterin levels, however, were independent of Cpn serostatus when combining both stable and unstable angina patients. Thus, immune activation in patients with acute coronary syndromes appears to be unrelated to Cpn seropositivity.

Lack of association between Chlamydia pneumoniae seropositivity and aortic atherosclerotic plaques: a population-based transesophageal echocardiographic study

OBJECTIVES

The objective of this study was to examine the relationship between Chlamydia pneumoniae seropositivity and aortic atherosclerotic plaques in the general population.

BACKGROUND

Seroepidemiologic studies suggest that C pneumoniae infection plays a role in the pathogenesis of atherosclerosis.

METHODS

Transesophageal echocardiography was performed in 385 subjects (median age 66 years, range 51 to 101 years; 53% men), a sample of the Olmsted County (Minnesota) population. The association between C pneumoniae immunoglobulin (Ig) G antibody titers and aortic atherosclerotic plaques was examined.

RESULTS

Chlamydia pneumoniae IgG antibodies (titers >or=1:16) were detected in 287 subjects (74.5%): low titers (1:16 to 1:32) in 58 (15.1%), intermediate titers (1:64 to 1:128) in 144 (37.4%), and high titers (>or=1:256) in 85 subjects (22.1%). Antibody titers were not associated with the presence of aortic plaques after adjustment for age, gender, and smoking status (p = 0.64). Compared with titers <1:16, the adjusted odds ratios for aortic plaques were 1.46 (95% confidence interval [CI] 0.63 to 3.42) for low titers, 1.32 (95% CI 0.68 to 2.55) for intermediate titers, and 0.94 (95% CI 0.42 to 2.07) for high titers. Among the subgroup with plaques, antibody titers were not associated with the presence of plaques >or=4 mm thick (p = 0.99), plaques >or=6 mm (p = 0.49), or mobile debris (p = 0.71), after adjustment for age and smoking.

CONCLUSIONS

Chlamydia pneumoniae IgG antibody titers are not associated with the presence or severity of aortic atherosclerosis in the general population. These observations do not support a role for C pneumoniae infection in the initiation or progression of atherosclerosis.

Chlamydia pneumoniae DNA in patients with symptomatic carotid atherosclerotic disease

OBJECTIVE

We evaluated the correlation between the presence of Chlamydia pneumoniae in atherosclerotic carotid plaques, lymph nodes, and peripheral blood mononuclear cells (PBMCs), and symptomatic carotid atherosclerotic disease.

METHODS

Fifty-one consecutive patients undergoing carotid endarterectomy were enrolled; 18 of the 51 patients had symptomatic disease, whereas 33 had asymptomatic disease. Detection of C pneumoniae DNA in atherosclerotic carotid plaques, lymph nodes, and PBMCs was performed with polymerase chain reaction (PCR). C pneumoniae antibodies were measured with a microimmunofluorescence test.

RESULTS

C pneumoniae DNA in atherosclerotic carotid plaques was detected in 44.4% of patients with symptomatic disease and in 30.3% of those with asymptomatic disease (P =.48). C pneumoniae DNA in lymph nodes was detected in 33.3% of patients with symptomatic disease and 18.2% of those with asymptomatic disease (P =.19). Prevalence of C pneumoniae DNA in PBMCs was significantly higher in patients with symptomatic disease (72.2%) compared with those with asymptomatic disease (30.3%) (P =.01). Serologic results support the association between C pneumoniae DNA in PBMCs and symptomatic carotid atherosclerotic disease, because seropositivity for anti-chlamydial immunoglobulin (Ig) A antibodies was significantly higher in PCR-positive PBMCs in patients with symptomatic disease compared with patients with asymptomatic disease (P =.02).

CONCLUSIONS

Detection of C pneumoniae in PBMCs shows that C pneumoniae may be associated with symptomatic carotid atherosclerotic disease. Although we believe there is need for standardization of PCR methods and for assessing sensitivity, specificity, and predictive values of the tests, we suggest that presence of C pneumoniae DNA in PBMCs is a valid surrogate marker of risk for endovascular chlamydial infection. Only long-term cohort studies and interventional trials will clarify the etiopathogenic role of C pneumoniae.

The effect of viable Chlamydia pneumoniae on serum cytokines and adhesion molecules in hemodialysis patients

BACKGROUND

Chlamydia pneumoniae (Cp) induces the production of cytokines and adhesion molecules in infected host eukaryotic cells. The causes for pro-inflammatory cytokine and adhesion molecule increase in hemodialysis (HD) patients have not been fully elucidated. The possibility that, in this particularly atherosclerotic population, Cp, a microorganism implicated in the infectious-based inflammatory hypothesis of atherosclerosis' is also responsible for these molecules' increase is assessed in this study.

METHODS

In 130 stable HD patients, serum interleukin-1 beta (IL-1), interleukin-6, tumor necrosis factor alpha, interleukin-10, L-selectin, E-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 (VCAM-1) levels were determined. Cp presence was identified by inoculation of the patient's peripheral blood mononuclear cells (PBMCs) in Hep-2 cell lines and subsequent polymerase chain reaction (PCR) in DNA extracted from cell cultures, as well as by determination of serum IgG antibodies against Cp (IgGCp).

RESULTS

Patients, positive or negative for IgGCp, had no statistically significant differences in all molecules measured. Patients with viable Cp in PBMCs had higher serum levels of IL-1 and soluble VCAM-1 than negative ones for IgGCp (IL-1 6.87 +/- 7.35 vs. 2.34 +/- 1.47 pg/mL; P = 0.0009 and VCAM-1 1647.16 +/- 513.64 vs. 1162.14 +/- 546.83 ng/mL; P = 0.0115, respectively). Viable Cp in PBMCs remained a significant predictor factor for IL-1 and VCAM-1 in statistical analysis, when patients' characteristics and dialysis conditions were also evaluated.

CONCLUSIONS

Our results showed that some serum cytokine and adhesion molecule increase in HD patients could be attributed to viable Cp presence in PBMCs. These findings support the Cp-based inflammatory atherogenous hypothesis and add a better understanding of these molecules' increase in HD patients.

Detection of Chlamydia pneumoniae in peripheral blood mononuclear cells: correlation with inflammation and atherosclerosis in haemodialysis patients

BACKGROUND

Chlamydia pneumoniae has been implicated as an inflammatory agent in atherosclerosis. Clinical studies in this field have yielded conflicting results, which may have resulted from a lack of standardization for C.pneumoniae detection. We attempted to accurately estimate C.pneumoniae prevalence and to examine whether C.pneumoniae is associated with atherosclerosis and inflammation in haemodialysis (HD) patients. To do this, we assessed C.pneumoniae presence by a combination of methods and correlated its levels with inflammatory and atherosclerotic indexes in these patients.

METHODS

Chlamydia pneumoniae was identified by polymerase chain reaction (PCR) in DNA extracted from cell cultures inoculated with patient buffy coats and by serum IgG antibodies against C.pneumoniae (IgGCp). Inflammation was assessed by C-reactive protein and serum amyloid A and atherosclerosis was evaluated from clinical and laboratory data.

RESULTS

Of the 130 patients, only nine had viable C.pneumoniae in peripheral blood mononuclear cells (PBMCs) while 64 had serum IgGCp. Although patients with viable C.pneumoniae had higher atherosclerotic scores, seropositive and negative patients showed similar scores. Patients with atherosclerosis exhibited higher inflammatory indexes. Neither patients with detectable C.pneumoniae in PBMCs nor seropositive subjects had higher inflammation than negative patients.

CONCLUSIONS

We found that viable C.pneumoniae in PBMCs, assessed by cell culture and PCR, was present in a small percentage of HD patients and was correlated with atherosclerosis. Seropositivity was much higher in HD patients but was not associated with viable C.pneumoniae or with atherosclerosis. Further studies in HD patients using high sensitivity and specificity methods in larger populations will be necessary to clarify the relationship between C.pneumoniae and atherosclerosis.

Reliability of nested PCR for detection of Chlamydia pneumoniae DNA in atheromas: results from a multicenter study applying standardized protocols

The present multicenter study was designed to find explanations for the discrepancies in the reported rates of detection of Chlamydia pneumoniae DNA in endarterectomy specimens. Coded identical sets of (i) a C. pneumoniae DNA dilution series (panel 1; n = 10), (ii) spiked control tissue specimens (panel 2; n = 10 specimens, including 5 negative controls), and (iii) endarterectomy specimens (panel 3; 15 atheromas, 5 negative controls) were analyzed at four laboratories by three standardized DNA extraction methods in each laboratory and a nested touchdown PCR protocol targeting the ompA gene of C. pneumoniae. Panel 1 samples were correctly identified as positive to levels of 0.3 inclusion-forming units (IFU)/PCR mixture (100%) and 0.03 IFU/PCR mixture (50%). All negative controls were correctly reported as negative. Panel 2 samples were identified as C. pneumoniae positive to levels of 0.01 IFU/PCR mixture (100%) and 0.005 IFU/PCR mixture (91%), independent of the DNA extraction method used, and only one false-positive result was reported. For panel 3 samples, 5 of 240 (2%) analyses (in which DNA extractions and PCR were performed at the same laboratory) were positive; the positive specimens were from three endarterectomy specimens and two negative controls. After exchange of DNA extracts between laboratories, 13 of 15 atheroma samples were C. pneumoniae DNA positive in at least 1 of a series of 48 analyses per atheroma sample; however, the overall positivity rate did not exceed 5% (33 of 720 analyses) and therefore was lower than that for the negative controls (8%; 19 of 240 analyses). Not a single positive result could be achieved when all panel 3 extracts (n = 240 analyses) were reamplified by a 16S rRNA PCR followed by hybridization with a C. pneumoniae-specific probe. Statistical analyses demonstrated that positive results did not occur in an independent and random fashion and could most likely be explained by amplicon carryover at the nested PCR level as well as amplicon introduction during DNA extraction, but not by the patterns of distribution of very low target levels or a certain DNA extraction protocol. The results of studies by nested PCR for detection of the prevalence of C. pneumoniae will always be questionable.

Association of circulating Chlamydia pneumoniae DNA with cardiovascular disease: a systematic review

BACKGROUND

Chlamydia pneumoniae antigens, nucleic acids, or intact organisms have been detected in human atheroma. However, the presence of antibody does not predict subsequent cardiovascular (CV) events. We performed a systematic review to determine whether the detection of C. pneumoniae DNA in peripheral blood mononuclear cells (PBMC) was associated with CV disease.

METHODS

We sought studies of C. pneumoniae DNA detection in PBMC by polymerase chain reaction (PCR) among patients with CV disease or other clinical conditions. We pooled studies in which CV patients were compared with non-diseased controls. We analyzed differences between studies by meta-regression, to determine which epidemiological and technical characteristics were associated with higher prevalence.

RESULTS

Eighteen relevant studies were identified. In nine CV studies with control subjects, the prevalence of circulating C. pneumoniae DNA was 252 of 1763 (14.3%) CV patients and 74 of 874 (8.5%) controls, for a pooled odds ratio of 2.03 (95% CI: 1.34, 3.08, P < 0.001). Prevalence was not adjusted for CV risk factors. Current smoking status, season, and age were associated with C. pneumoniae DNA detection. High prevalence (>40%) was found in patients with cardiac, vascular, chronic respiratory, or renal disease, and in blood donors. Substantial differences between studies were identified in methods of sampling, extraction, and PCR targets.

CONCLUSIONS

C. pneumoniae DNA detection was associated with CV disease in unadjusted case-control studies. However, adjustment for potentially confounding measures such as smoking or season, and standardization of laboratory methods, are needed to confirm this association.

The intracellular life of chlamydiae

The ability to cause persistent infection is one of the major characteristics of all chlamydial species in their appropriate hosts. Persistent infection with Chlamydia trachomatis and Chlamydia pneumoniae has been implicated in the pathogenesis of many chronic diseases, some initially not thought to be infectious, including pelvic inflammatory disease, arthritis, asthma, and atherosclerosis. Chlamydiae have a unique developmental cycle with morphologically distinct infectious and reproductive forms: elementary (EB) and reticulate bodies (RB). Chlamydiae appear to circumvent the host endocytic pathway and inhabit a nonacidic vacuole that is dissociated from late endosomes and lysosomes. Chlamydiae also have been demonstrated to enter a persistent state after treatment with cytokines such as interferon-gamma (IFN-gamma), treatment with antibiotics, or restriction of certain nutrients, or to enter this state spontaneously under certain culture conditions. While the organism is in the persistent state, metabolic activity is reduced, and the organism is often refractory to antibiotic treatment. Ultrastructural analysis of IFN-gamma-treated C pneumoniae demonstrates atypical inclusions containing large reticulate-like aberrant bodies with no evidence of redifferentiation into EBs. Persistent C pneumoniae infection appears to be associated with continued expression of genes associated with DNA replication but not with those genes involved with bacterial cell division. The latter observation may explain the appearance of the large abnormal RBs seen in ultrastructural studies. Studies of the association of chlamydiae with chronic disease have been hampered by difficulties in diagnosing chronic, persistent infection with the organism, which, in turn, render determining the efficacy of antibiotic therapy very difficult.

Detection of Chlamydia pneumoniae by polymerase chain reaction-enzyme immunoassay in intestinal mucosal biopsies from patients with inflammatory bowel disease and controls

BACKGROUND AND AIM

It has been suggested that Chlamydia is an organism that may have the potential to cause inflammatory bowel disease (IBD) in susceptible individuals. Chlamydia pneumoniae has emerged as an important human pathogen in the last decade. The objective of the present study was to investigate the frequency of the presence of C. pneumoniae DNA in intestinal biopsies from patients with IBD and from non-IBD controls.

METHODS

The DNA was extracted from 222 colonoscopic biopsies, which were obtained from 11 patients with Crohn's disease (CD), 18 patients with ulcerative colitis (UC) and from 37 non-IBD control patients. The presence of the C. pneumoniae omp1 gene and C. trachomatis 16S rRNA gene was determined using a rapid and sensitive polymerase chain reaction-enzyme immunoassay (PCR-EIA).

RESULTS

The C. pneumoniae-specific DNA was detected in 32 (14.4%) of 222 endoscopic biopsies. Among them, C. pneumoniae DNA were found in nine of 42 (21.4%) biopsies from patients with CD, nine of 59 (15.3%) biopsies from patients with UC, and 14 out of 122 (11.4%) biopsies from non-IBD control patients, respectively. Moreover, the percentage of patients with at least one biopsy positive for C. pneumoniae was higher, although not statistically significant, in CD (36.4%) and UC patients (38.9%) compared to non-IBD controls (16.2%). In contrast, C. trachomatis DNA was detected in only two of 222 (0.9%) biopsy samples.

CONCLUSION

The C. pneumoniae DNA was detected in the intestine of both patients with IBD and in non-IBD control patients, probably reflecting the high prevalence of this organism in the environment. The moderate yield of positive biopsies in our IBD patients and the fact that the detection rate of C. pneumoniae DNA was similar in endoscopic biopsies from IBD patients and non-IBD controls does not support a direct role for this organism in the pathogenesis of IBD.

Chlamydia pneumoniae in infrequently examined blood vessels

AIM

To determine the prevalence of Chlamydia pneumoniae DNA in infrequently examined blood vessels.

METHODS

Vessels obtained from 15 men and six women at coronary artery bypass surgery were tested by a nested polymerase chain reaction (PCR) assay for C pneumoniae DNA.

RESULTS

Chlamydia pneumoniae DNA was detected in four of six atheromatous ascending aorta specimens but in none of eight non-atheromatous aorta specimens, in six of 11 atheromatous internal mammary artery specimens but in none of seven non-atheromatous internal mammary artery specimens, in five of seven long saphenous vein specimens showing evidence of disease but in none of 12 specimens without evidence of disease, and in two of three previously grafted veins. Overall, C pneumoniae occurred significantly more often in diseased than in normal vessels (p = < 0.00001).

CONCLUSIONS

Chlamydia pneumoniae is often present in diseased areas of arteries, including the internal mammary arteries, and even in diseased areas of veins. It is not present in apparently healthy areas of either type of vessel.

Development and evaluation of real-time PCR-based fluorescence assays for detection of Chlamydia pneumoniae

Chlamydia pneumoniae is an important respiratory pathogen recently associated with atherosclerosis and several other chronic diseases. Detection of C. pneumoniae is inconsistent, and standardized PCR assays are needed. Two real-time PCR assays specific for C. pneumoniae were developed by using the fluorescent dye-labeled TaqMan probe-based system. Oligonucleotide primers and probes were designed to target two variable domains of the ompA gene, VD2 and VD4. The limit of detection for each of the two PCR assays was 0.001 inclusion-forming unit. Thirty-nine C. pneumoniae isolates obtained from widely distributed geographical areas were amplified by the VD2 and VD4 assays, producing the expected 108- and 125-bp amplification products, respectively. None of the C. trachomatis serovars, C. psittaci strains, other organisms, or human DNAs tested were amplified. The amplification results of the newly developed assays were compared to the results of culturing and two nested PCR assays, targeting the 16S rRNA and ompA genes. The assays were compared by testing C. pneumoniae purified elementary bodies, animal tissues, 228 peripheral blood mononuclear cell (PBMC) specimens, and 179 oropharyngeal (OP) swab specimens obtained from ischemic stroke patients or matched controls. The real-time VD4 assay and one nested PCR each detected C. pneumoniae in a single, but different, PBMC specimen. Eleven of 179 OP specimens (6.1%) showed evidence of the presence of C. pneumoniae in one or more tests. The real-time VD4 assay detected the most positive results of the five assays. We believe that this real-time PCR assay offers advantages over nested PCR assays and may improve the detection of C. pneumoniae in clinical specimens.

Chlamydia pneumoniae and atherosclerosis -- what we know and what we don't

The clinical manifestations of atherosclerosis include coronary artery disease (CAD), stroke, abdominal aortic aneurysm and peripheral vascular disease. World-wide, CAD and stroke are the leading causes of death and disability. The recognition of atherosclerosis as an inflammatory disease in its genesis, progression and ultimate clinical manifestations has created an interesting area of vascular research. Apart from those well-known traditional risk factors for atherosclerosis, novel and potentially treatable atherosclerotic risk factors such as homocysteine (an amino acid derived from the metabolism of dietary methionine that induces vascular endothelial dysfunction) and infections have emerged. In fact, the century-old 'infectious' hypothesis of atherosclerosis has implicated a number of micro-organisms that may act as contributing inflammatory stimuli. Although cytomegalovirus, Helicobacter pylori and Chlamydia pneumoniae are the three micro-organisms most extensively studied, this review will focus on C. pneumoniae. Collaborative efforts from many disciplines have resulted in the accumulation of evidence from seroepidemiological, pathological, animal model, immunological and antibiotic intervention studies, linking C. pneumoniae with atherosclerosis. Seroepidemiological observations provide circumstantial evidence, which is weak in most prospective studies. Pathological studies have demonstrated the preferential existence of C. pneumoniae in atherosclerotic plaque tissues, while animal model experiments have shown the induction of atherosclerosis by C. pneumoniae. Finally, immunological processes whereby C. pneumoniae could participate in key atherogenic and atherothrombotic events have also been identified. Although benefits of the secondary prevention of atherosclerosis have been demonstrated in some antibiotic intervention studies, a number of negative studies have also emerged. The results of the ongoing large prospective human antibiotic intervention trials may help to finally establish if there is a causal link between C. pneumoniae infection and atherosclerosis.

Chlamydia pneumoniae and atherosclerosis: critical assessment of diagnostic methods and relevance to treatment studies

A number of studies have found that inflammation of the vessel wall plays an essential role in both the initiation and progression of atherosclerosis and erosion and fissure and the eventual rupture of plaques. Chlamydia pneumoniae is one of the infectious agents that have been investigated as possible causes of this inflammation. Initial studies of the association of C. pneumoniae and cardiovascular disease (CVD) were seroepidemiologic, and these were followed by studies in which the organism was identified in vascular tissue from patients with CVD by electron microscopy, PCR and immunocytochemical staining (ICC). C. pneumoniae has also been isolated by culture from vascular tissue in a small number patients. However, no single serologic, PCR, or ICC assay has been used consistently across all studies. The assays used are also not standardized. Recent studies of serologic and PCR assays for diagnosis of C. pneumoniae infection have suggested that there may be substantial interlaboratory variation in the performance of these tests. It now appears that some of the inconsistency of results from study to study may be due, in part, to lack of standardized methods. Although initial seroepidemiologic studies demonstrated a significantly increased risk of adverse cardiac outcome in patients who were seropositive, subsequent prospective studies found either small or no increased risk. In addition to the lack of consistent serologic criteria, recent evaluations have demonstrated inherent problems with performance of the most widely used serologic methods. Most importantly, we do not have a reliable serologic marker for chronic or persistent C. pneumoniae infection.

Secondary prevention of coronary artery disease with antimicrobials: current status and future directions

Over the past several decades, coronary artery disease (CAD) has become the major health problem in the Western world with more than 50% of deaths attributed to its complications. The exact causes of atherosclerosis are not clearly known, although multiple risk factors (e.g. hypertension, hyperlipidemia, diabetes mellitus, family history, and smoking) have been well described. However, these risk factors account for only about 50% of the total risk of CAD. Consequently, an ongoing search is under way to discover new risk factors for atherosclerosis as well as the basic underlying causes of progression. Although the evidence is not yet definitive, recent studies have shown that chronic infection by such bacterial organisms as Chlamydia pneumoniae, Helicobacter pylori, and a variety of dental pathogens may play a causative role in atherosclerosis. If this is true, then antimicrobial therapy may be helpful in the secondary prevention of CAD. Indeed, several small studies have already been completed testing this hypothesis. This article reviews the evidence associating these bacterial pathogens to CAD and presently available information regarding the use of antibiotics in the setting. At present, most studies evaluating the potential efficacy antimicrobials in the secondary prevention of CAD have tested the use of macrolide antibodies. Although several small preliminary studies have reported promising results favoring a clinical benefit from even short (<3 months) courses of antimicrobial therapy, the first large clinical trial, the Weekly Intervention with Zithromax for Atherosclerosis and its Related Disorders (WIZARD) study, did not show a statistically significant beneficial effect of a 3 month course of azithromycin over placebo by the end of up to 4 years follow-up. However, a statistically significant (p = 0.03) 33% reduction in death and myocardial infarction was found at 6 months, 3 months after the discontinuation of antibiotics. This robust clinical benefit, however, was not sustained over the ensuing 3.5 years of follow-up. These disappointing long-term outcomes of short-term therapy with antimicrobials may be explained by the recently discovered difficulty found in eradicating chronic vascular infections such as C. pneumoniae. It remains possible that longer term antimicrobial therapy or short-term use of more potent single agents or combinations, capable of effectively eradicating the offending organisms might provide added clinical benefit in the fight against CAD. Further studies are ongoing or planned to evaluate this potential. In the meantime, it is not presently recommended that antimicrobials be routinely prescribed for the secondary prevention of CAD.

Prevalence of Chlamydia pneumoniae in peripheral blood mononuclear cells in Italian patients with acute ischaemic heart disease

Chlamydia pneumoniae infection generally starts in the respiratory tract and probably disseminates systemically in the blood stream within alveolar macrophages. We investigated the prevalence of C. pneumoniae DNA in peripheral blood mononuclear cells (PBMC) in patients with acute ischaemic heart disease. Samples of blood were obtained from 93 consecutive patients with acute ischaemic heart disease and from 42 healthy subjects, for detection of C. pneumoniae DNA in PBMC by polymerase chain reaction (PCR) and for serology. C. pneumoniae DNA in PBMC was detected in 25.8% (24/93) of the patients with acute ischaemic heart disease and in 4.8% (2/42) of the healthy subjects (P=0.008). C. pneumoniae IgG was found in 76.3% of patients and in 45.2% of healthy subjects (P=0.0008) while C. pneumoniae IgA was found in 59.1% and in 33.3%, respectively (P=0.01). No correlation was found between anti-C. pneumoniae antibody titers and positive PCR results. The detection of C. pneumoniae DNA in PBMC may aid in selecting patients who may benefit from antibiotic treatment; however, to support this contention, longitudinal studies on patients treated with antibiotics would also be necessary.

Chlamydia pneumoniae and cytomegalovirus seropositivity, inflammatory markers, and the risk of myocardial infarction at a young age

BACKGROUND

Pathogens causing chronic infections may promote atherosclerosis. The aim of our study was to evaluate the association of Chlamydia pneumoniae (Cp) and cytomegalovirus (CMV) infection and of inflammatory activation with premature myocardial infarction (MI).

METHODS

Specific anti-Cp and anti-CMV immunoglobulin G (IgG), fibrinogen, white blood cells (WBC), and C-reactive protein (CRP) were measured in 120 post-MI patients </=50 years old and in 120 age-matched controls.

RESULTS

Seropositivity to Cp and elevated concentrations of anti-Cp and anti-CMV IgGs were more frequent (P =.01) in patients than in control subjects, and fibrinogen, CRP, and WBC levels (P =.02) were more elevated. After adjustment for coronary risk factors and socioeconomic status, the odds ratios (95% confidence intervals) for premature MI were 2.4 (1.3-4.6) for Cp infection and 2.9 (1.5-5.8) for CMV. The risk of Cp infection was greater in smokers (3.7, 1.8-7.6). When both infections were present (35% of patients vs 8% of controls, P =.001), CRP was higher (P =.01) and the risk increased by 12 times (12.5, 4-38.9) compared with that in subjects without any infection and by 5 times (4.9, 2.2-10.9) if only one was present.

CONCLUSIONS

After adjustment for confounders, seropositivity to both Cp and CMV infections is associated with the diagnosis of premature MI. The combination of both infections is associated with an enhanced inflammatory response and a markedly increased risk of premature MI.

Detection of Chlamydia pneumoniae antigenin PBMNCs of healthy blood donors

BACKGROUND

Because it has been increasingly recognized that Chlamydia pneumoniae may be linked to some chronic inflammatory diseases, including atherosclerosis, detection of this pathogen in blood from patients may be valuable in the diagnosis of such diseases. However, the prevalence of chlamydia in the blood of healthy donors has not yet been extensively studied.

STUDY DESIGN AND METHODS

The presence of C. pneumoniae in PBMNCs obtained from healthy persons who donated blood for blood transfusion was assessed by a PCR that was specific for the C. pneumoniae 16S rRNA gene and by the use of staining with FITC-conjugated chlamydia MoAb.

RESULTS

Twenty-one (8.9%) of 237 blood samples tested showed the presence of C. pneumoniae DNA and antigen in the PBMNCs. There was no significant difference in the presence of chlamydia in blood according to sex or to age between 20 and 59 years of age. However, a possible seasonal variation in the presence of chlamydia in blood from healthy donors was suggested by the results obtained.

CONCLUSION

A significant percentage of healthy donors carry C. pneumoniae, which may be a risk factor for some chronic diseases.

Demonstration of Chlamydia pneumoniae in atherosclerotic arteries from various vascular regions

Chlamydia pneumoniae (CP) has been reported to be a pathogenic agent in the mechanism leading to atherosclerosis. The majority of available data is focused mainly on coronary artery disease whereas the distribution of CP in different areas, associated with atherosclerotic disorders, has not been completely clarified. In this study we investigated the presence of CP in atheromasic plaques from five different vascular areas (basilary artery, coronary artery, thoracic aorta, abdominal aorta, renal arteries) using nested polymerase chain reaction (PCR) and immunohistochemical staining (IHC), in order to establish the putative association of CP with atherosclerotic disease. The same atheromasic plaques were also tested for the presence of Helicobacter pylori (HP) and cytomegalovirus (CMV), other putative agents of atherosclerosis, using a nested PCR technique. Our data indicate that the presence of CP can be demonstrated in 100% of patients tested, considering globally the five areas of analysis. On the other hand the presence of HP has been demonstrated in four out of 18 patients (22.2%), and CMV only in three out of 18 (16.6%). Our results strongly suggest an association between CP and atherosclerosis and highlight the need for the detection of CP in multiple vascular areas of the same patient.

Periodontal infections and cardiovascular disease--how strong is the association?

In the past decade there has been renewed interest in the old hypothesis that infections increase the risk of developing cardiovascular disease and stroke. There is now a convincing body of evidence that atherosclerosis has a major inflammatory component and is much more than the simple vascular accumulation of lipids. Infectious agents that have been linked to an increased risk of coronary heart disease (CHD) include Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus, and herpesviruses. The concept has emerged that each of these agents is an independent risk factor for CHD and that common chronic infections are important. In addition, periodontal infections have also been implicated as one of several factors contributing to the development of CHD. Evidence supporting a causative role of chronic infections in CHD is largely circumstantial. However, the evidence is sufficiently strong to warrant further examination of the possible link between chronic infections and CHD. In this review the lines of evidence for a causative role of C. pneumoniae in the development of CHD are summarized and contrasted with the lines of evidence suggesting a periodontal infection--CHD association. If common or widespread chronic infections are truly important risk factors for CHD, it is unlikely that a single infection will be shown to be causative. It is likely that the entire microbial burden of the patient from several simultaneous chronic infections is more important (e.g., H. pylori-caused gastric ulcers + C. pneumoniae-caused bronchitis + periodontitis). Increased cooperation between cardiologists and periodontists will be required to determine if, and what, combinations of common chronic infections are important in the pathogenesis of CHD and stroke.