Chlamydia pneumoniae and other risk factors for atherosclerosis

Investigation of Possible Role of Chlamydia in Pseudoexfoliation Syndrome

Background: Pseudoexfoliation syndrome (PES) is a systemic disease characterized by the aggregation of fibrillar extracellular material in intraocular and extraocular tissues with unknown etiology. Clarifying the etiopathogenesis of PES would be important for public health. Objectives: We aimed to investigate the possible role of Chlamydia in the etiology of PES. Methods: This cross-sectional study was carried out in the ophthalmology clinic of a tertiary hospital. The study included two groups, including the patient group (PES patients with nuclear cataracts) and the control group (patients with nuclear cataracts). Patients with other ophthalmic problems and systemic diseases were excluded. Blood samples and conjunctival swabs taken from 49 patients and 42 controls were used in the study. Anti-Chlamydia trachomatis IgG and IgM, anti-C. pneumoniae IgG and IgM, Interleukin (IL)-6, and IL-20 were studied in the serum samples. The PCR study was performed with conjunctival swab samples and sequence analysis of PCR-positive samples was performed. Results: According to the results of the study, there was no statistically significant difference between the groups in terms of anti-C. trachmatis IgG, anti-C. trachmatis IgM, anti-C. pneumoniae IgM, IL-6, and PCR results. There was a statistically significant difference between patient and control groups in terms of anti-C. pneumoniae IgG and IL-20 levels. The DNA sequencing of all PCR products was found to be compatible with C. pneumoniae. Conclusions: It seems that C. pneumoniae might have an important role in the etiology and development of PES. However, further studies in larger groups are needed to clarify these results.

A novel transport mechanism for MOMP in Chlamydophila pneumoniae and its putative role in immune-therapy

Major outer membrane proteins (MOMPs) of Gram negative bacteria are one of the most intensively studied membrane proteins. MOMPs are essential for maintaining the structural integrity of bacterial outer membranes and in adaptation of parasites to their hosts. There is evidence to suggest a role for purified MOMP from Chlamydophila pneumoniae and corresponding MOMP-derived peptides in immune-modulation, leading to a reduced atherosclerotic phenotype in apoE(-/-) mice via a characteristic dampening of MHC class II activity. The work reported herein tests this hypothesis by employing a combination of homology modelling and docking to examine the detailed molecular interactions that may be responsible. A three-dimensional homology model of the C. pneumoniae MOMP was constructed based on the 14 transmembrane β-barrel crystal structure of the fatty acid transporter from Escherichia coli, which provides a plausible transport mechanism for MOMP. Ligand docking experiments were used to provide details of the possible molecular interactions driving the binding of MOMP-derived peptides to MHC class II alleles known to be strongly associated with inflammation. The docking experiments were corroborated by predictions from conventional immuno-informatic algorithms. This work supports further the use of MOMP in C. pneumoniae as a possible vaccine target and the role of MOMP-derived peptides as vaccine candidates for immune-therapy in chronic inflammation that can result in cardiovascular events.

Chlamydia pneumoniae DNA in Peripheral Blood Mononuclear Cells in Healthy Control Subjects and Patients with Diabetes mellitus, Acute Coronary Syndrome, Stroke, and Arterial Hypertension

Infection with Chlamydia pneumoniae has been suggested to play a role in the development and maintenance of atherosclerosis based on differences in the prevalence of antibodies against Chlamydia pneumoniae in patients with and without atherosclerotic lesions. We evaluated the prevalence of Chlamydia pneumoniae DNA in the white cells of the peripheral blood in 194 patients with diabetes mellitus, 50 patients with acute coronary syndrome, 102 hypertensive patients, 193 patients having suffered a stroke and in 368 healthy subjects with a nested polymerase chain reaction (nPCR). Overall the prevalence of Chlamydia pneumoniae DNA in peripheral blood cells was: diabetes mellitus (11.9%), stroke (10.4%), hypertension (6.9%), acute coronary syndrome (4.0%) and healthy subjects (7.9%). The prevalence of Chlamydia pneumoniae DNA in the patients was not significantly different from prevalence in the healthy subjects. However, a significant association was found between high levels of triglycerides and presence of C. pneumoniae DNA (OR = 3.27, p < 0.04). The prevalence of C. pneumoniae DNA was not associated with age, gender, smoking, BMI, HDL, CRP, plasma creatinine and symptoms or signs of ischaemic heart disease. The association between high levels of triglycerides and C. pneumoniae DNA suggests that infection by C. pneumoniae affects lipid metabolism.

Chlamydia pneumoniae infection is associated with elevated body mass index in young men

Chlamydia pneumoniae infection is said to be associated with obesity. We studied the association between C. pneumoniae infection and inflammation and increased BMI in 891 Finnish military recruits. IgG seropositivity in arrival and departure serum samples during 6-12 months of military service was considered as persistence of antibodies and a possible indication of chronic infection. Persistently high C-reactive protein (CRP) level (elevated on arrival and departure) (OR 2.2, 95% CI 1.3-3.9), and persistent C. pneumoniae antibodies (OR 2.1, 95% CI 1.5-2.8) were significant risk factors for overweight (BMI 25 kg/m2). In addition, those who had persistent antibodies and persistently elevated CRP levels, or those who had either of them, had a significantly higher BMI (kg/m2) compared to those who had neither of them (25.8 vs. 24.6 vs. 23.5, respectively; P<0.001). These results provide new information about the association between possible chronic C. pneumoniae infection and obesity in young men.

Association of Chlamydia pneumoniae infection with HLA-B*35 in patients with coronary artery disease

The immune system may interplay between Chlamydia pneumoniae infection and coronary artery disease (CAD). Major histocompatibility complex genes regulate innate and adaptive immunity. Patients with CAD (n = 100) and controls (n = 74) were enrolled. Human leukocyte antigens (HLA-A, HLA-B, and HLA-DRB1), four lymphotoxin alpha single-nucleotide polymorphisms, and complement C4A and C4B allotypes were typed, and their haplotypes were inferred. The presence of serum C. pneumoniae immunoglobulin A (IgA) (titer, > or =40) or IgG (titer, > or =128) antibodies or immune complex (IC)-bound IgG antibodies (titer, > or =2) was considered to be a serological marker suggesting chronic C. pneumoniae infection. C. pneumoniae IgA antibodies were found more frequently in patients than in controls (P = 0.04). Among the patients, multiple logistic regression analysis showed the HLA-B*35 allele to be the strongest-risk gene for C. pneumoniae infection (odds ratio, 7.88; 95% confidence interval, 2.44 to 25.43; P = 0.0006). Markers of C. pneumoniae infection were found more frequently in patients with the HLA-A*03-B*35 haplotype than in those without the haplotype (P = 0.007 for IgA; P = 0.008 for IgG; P = 0.002 for IC). Smokers with HLA-B*35 or HLA-A*03-B*35 had markers of C. pneumoniae infection that appeared more often than in smokers without these genes (P = 0.003 and P = 0.001, respectively). No associations were found in controls. In conclusion, HLA-B*35 may be the link between chronic C. pneumoniae infection and CAD.

Periodontal disease and coronary heart disease

BACKGROUND

Several epidemiological studies have demonstrated an association between periodontal disease and coronary heart disease (CHD). The association could be a result of confounding by mutual risk factors. The present study was undertaken in a Danish population to reveal the significance of common risk factors.

METHODS

The investigation was conducted as a case-control study comprising 250 individuals: 110 individuals with verified CHD from a Department of Cardiovascular Medicine and 140 control individuals without CHD from the Copenhagen City Heart Study. Information on diabetic status, smoking habits, alcohol consumption, physical activity, school attendance, household income, body weight and height, triglyceride, and serum cholesterol was obtained. Full-mouth probing depth (PD), clinical attachment loss (CAL), bleeding on probing (BOP), and alveolar bone level (ABL) on radiographs were registered. ABL was stratified into ABL1=ABL<or=2 mm; ABL2=ABL>2 to <or=4 mm; and ABL3=ABL>4 mm. Multiple logistic regression models with stepwise backward elimination were used allowing variables with P<0.15 to enter the multivariate analysis.

RESULTS

The CHD group had a significantly lower outcome with respect to PD, BOP, CAL, and ABL. For participants<60 years old, only risk factors such as smoking and diabetic status entered the multivariate analysis. For the ABL3 group, there was a significant association with CHD for participants<60 years old, the odds ratio being 6.6 (1.69 to 25.6). For participants>or=60 years old, there was no association.

CONCLUSIONS

The present study showed a positive association between periodontal disease and CHD in agreement with several other studies. The association was highly age dependent and could only be attributed to diabetes and smoking to some extent.

Presence of Chlamydia pneumoniae in patients with and without atherosclerosis

Data published over the past decade show that Chlamydia pneumoniae is likely associated with the development of atherosclerosis. The aim of this study was to ascertain whether C. pneumoniae infections occur more frequently in patients with atherosclerosis than in healthy subjects. A total of 517 persons were studied. Serum samples, leukocytes, and tissue samples were assayed for the presence of C. pneumoniae-specific IgG and IgA antibodies and C. pneumoniae DNA. C. pneumoniae DNA was found in renal, iliac, and brachial vessels, but it was not detected in radial arteries. C. pneumoniae DNA was found most often in directional coronary atherectomy tissue specimens (11/41, 26.8%), but it was also found in the leukocytes of 14.9% (28/188) of patients with atherosclerosis and 24.6% (28/114) of patients without atheroma changes in vessels. Specific IgG and IgA antibodies were present in 63.8 and 49.9% of atheroma patients, respectively. The prevalence of C. pneumoniae antibodies differs significantly in patients with and without atherosclerosis (for IgG, p=0.002, and for IgA, p=0.006). The identification of persons with chlamydial infection of atherosclerotic arteries necessitates the examination of vascular tissues obtained during revascularization procedures. Serological investigation alone cannot identify individuals with vascular chlamydial infections. Detection of C. pneumoniae DNA in peripheral blood mononuclear cells does not seem to be the exclusive marker of persistent vascular infection. A more easily accessible parameter that allows prediction of chlamydial vascular infection is required.

Chlamydia pneumoniae infection in HIV-positive patients: prevalence and relationship with lipid profile

OBJECTIVES

The aims of this study were to evaluate the prevalence and impact of Chlamydia pneumoniae infection in HIV-positive patients and to establish the relationship between C. pneumoniae infection and lipid profile.

METHODS

Detection of C. pneumoniae was by polymerase chain reaction (PCR) on Peripheral Blood Mononuclear Cells (PBMCs) collected from 97 HIV-positive patients. Samples were collected after overnight fast in EDTA-treated tubes. On the same day, patients were also tested for routine chemistry, HIV viral load, CD3, CD8 and CD4 cell counts and lipid profile [cholesterol, high-density lipoproteins (HDLs), low-density lipoproteins (LDLs) and triglycerides].

RESULTS

The overall prevalence of C. pneumoniae was 39%. The prevalence of C. pneumoniae was inversely related to the CD4 lymphocyte count (P=0.03). In the naive group, C. pneumoniae-positive patients had both significantly higher HIV load (71 021+/-15 327 vs. 14 753+/-14 924 HIV-1 RNA copies/mL; P=0.03) and lower CD4 cell count (348.0+/-165.4 vs. 541.7+/-294.8; P=0.04) than C. pneumoniae-negative patients. Moreover, treatment-naive patients with C. pneumoniae infection had significantly higher mean levels of cholesterol (185.3+/-56.2 vs. 124.8+/-45.9 mg/dL; P=0.01), triglycerides (117.2+/-74.7 vs. 68+/-27.6 mg/dL; P=0.04) and LDL (122.4+/-60.1 vs. 55.6+/-58 mg/dL; P=0.05) than C. pneumoniae-negative patients.

CONCLUSIONS

These data indicate that, in HIV-positive subjects, C. pneumoniae infection is relatively frequent and is associated with both low CD4 cell count and high HIV load. Furthermore, C. pneumoniae appears to be associated with hyperlipidaemia and might therefore represent a further risk factor for cardiovascolar disease in HIV-positive 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.

Smoking increases the risk of coronary artery disease in Chinese with Chlamydia pneumoniae infection

BACKGROUND

The infection with Chlamydia pneumoniae (Cp) has been claimed to associate with coronary artery disease (CAD). However, the seroepidemiological study of association between Cp infection and CAD still remains a source of controversy. The aim of the present study is to investigate the possible association of Cp infection with CAD in Chinese mainland population and the potential role of Cp infection combined with the traditional risk factors in CAD.

METHODS

1422 hospitalized patients with angiographically demonstrated CAD and 297 controls were recruited and tested for specific Cp IgG with enzyme-linked immunoassay (ELISA).

RESULTS

The prevalence of Cp IgG seropositivity in patients with CAD was significantly higher than that in controls (31.1% vs. 24.9%, P=0.035). Unadjusted odds ratios (OR) and 95% confidence intervals (CI) for CAD with the presence of seropositivity of IgG to Cp was 1.4 (1.0-1.8). After full adjustment for possible confounders on multiple logistic regression analysis, only a weak association of Cp infection with CAD was found. The adjusted OR (95% CI) for CAD associated with Cp infection was 1.3 (0.95-1.71, P=0.1). To further delineate the potential role of Cp infection in CAD, we divided subjects into seropositive (n=516) and seronegative (n=1203) groups according to their Cp IgG status. Notably, the adjusted OR (95% CI) for CAD associated with smoking was 4.0 (1.8-8.6) in the seropositive group, 0.9 (0.5-1.4) in the seronegative group, indicating that smoking can significantly increase the risk of CAD in subjects with Cp infection.

CONCLUSIONS

Cp infection is not strongly associated with CAD in Chinese mainland population; however, smoking increases the risk of CAD in those with Cp infection.

Chlamydophila pneumoniae infection of human aortic endothelial cells induces the expression of FC gamma receptor II (FcgammaRII)

Chronic endothelial infection is believed to be one of the factors able to cause endothelial cell damage and trigger the onset of human atherosclerosis. Chlamydophila pneumoniae infects endothelial cells and has received special attention because of both epidemiological and experimental evidence supporting its role as a risk factor for atherosclerosis. It is also possible that otherwise independent risk factors for atherosclerosis may have synergistic effects. Immune phenomena, such as the formation of circulating immune complexes (IC) containing modified LDL and corresponding antibodies, have been linked to the development of coronary artery disease. The antibodies involved in the immune response to modified lipoproteins are predominantly of the pro-inflammatory IgG1 and IgG3 subclasses. However, it is difficult to understand how circulating IC could cause endothelial damage and initiate the atherosclerotic process, unless they were formed in the subendothelial space or immobilized by endothelial cells. The last hypothesis would be possible if endothelial cells expressed Fcgamma receptors. Healthy endothelial cells do not express Fcgamma receptors, but endothelial cells infected by a variety of infectious agents do. Thus we decided to investigate whether infection of endothelial cells with C. pneumoniae is also able to cause the expression of Fcgamma receptors. The expression of Fcgamma receptors (CD64, 32, and 16) on human aortic endothelial cells infected with C. pneumoniae for 4, 24, 36, and 48 h was studied by flow cytometry. Twenty-four hours after infection 30-40% of the endothelial cells had detectable inclusion bodies, 8-9% of the total number of cells (approximately 25% of the infected cells) expressed FcgammaRII, and about 1.5-2% (5% of infected cells) expressed FcgammaRI and FcgammaRIII. Double-staining studies confirmed that the expression of FcgammaRII was limited to C. pneumoniae-infected endothelial cells. We conclude that C. pneumoniae infection induces primarily the expression of FcgammaRII by endothelial cells and this may be a significant link between two proposed pathogenic mechanisms involved in the pathogenesis of human atherosclerosis.

Chlamydia pneumoniae seropositivity is associated with increased plasma levels of soluble cellular adhesion molecules in community-dwelling subjects: the Shimanami Health Promoting Program (J-SHIPP) study

BACKGROUND AND PURPOSE

In vitro studies have demonstrated that Chlamydia pneumoniae infection of the endothelium increases the expression of adhesion molecules and chemokines, indicating that C pneumoniae infection affects the adhesion and recruitment of leukocytes to the endothelium, which is believed to be involved in the initial steps of atherosclerosis. However, whether chronic C pneumoniae infection increases these molecules in vivo has not been elucidated.

METHODS

The association between C pneumoniae seropositivity and plasma concentrations of soluble adhesion molecules and a chemokine was investigated in 200 community-dwelling residents free from cardiovascular diseases and medication. Plasma levels of IgA and IgG antibodies to C pneumoniae were measured by enzyme-linked immunosorbent assay. Indices of IgG and IgA antibodies were determined as the ratio to the standardized positive control. The subjects were divided into 3 groups according to the indices of antibodies: C pneumoniae seronegative (n=57, IgA<1.0 and IgG<1.0), C pneumoniae intermediate (n=81, 1.0< or =IgA> or =1.1 or 1.0< or =IgG> or =1.1), and C pneumoniae seropositive (n=62, IgA>1.1 and IgG>1.1). Plasma concentrations of soluble forms of intercellular adhesion molecule-1 (ICAM-1), vascular cellular adhesion molecule-1, and monocyte chemoattractant protein-1 were determined by enzyme-linked immunosorbent assay.

RESULTS

Plasma concentrations of ICAM-1 (392+/-118, 398+/-94, 470+/-154 ng/mL, P=0.0004) and vascular cellular adhesion molecule-1 (402+/-146, 419+/-130, 472+/-181 ng/mL, P=0.03) were significantly different among the C pneumoniae seronegative, intermediate, and seropositive groups respectively. However, plasma monocyte chemoattractant protein-1 was not significantly different among the 3 groups. Stepwise regression analysis showed that plasma concentration of ICAM-1 was significantly associated with C pneumoniae seropositivity, independent of other known risk factors for atherosclerosis and carotid intima-media thickness.

CONCLUSION

These findings indicate that C pneumoniae seropositivity is associated with higher plasma concentrations of soluble forms of adhesion molecules in the general population. The increase in circulating adhesion molecules may underlie the mechanisms linking C pneumoniae infection and atherosclerosis in vivo.

Evidence for infectious agents in cardiovascular disease and atherosclerosis

During the past decade, several novel risk factors for atherosclerosis, including inflammation and infections, have been reported. Seroepidemiological studies suggest an association between several microbes and coronary heart disease. Microbes or their structural components are found in atherosclerotic plaques, but the only intact microbes commonly present are herpes viruses and Chlamydia pneumoniae. These agents are able to initiate and accelerate atherosclerosis in animal models. If they cause persistent infection in the vessel wall, they can directly promote a proinflammatory, procoagulant, and proatherogenic environment. Microbes could also have a remote effect--e.g., bacterial heat shock proteins with high sequence homology with human counterpart could, in the presence of a chronic infection, induce autoimmunity against vascular cells, and lead to an atherosclerotic process. Several intervention trials with antibiotics are underway, and will hopefully shed new light on the role of bacteria in atherosclerosis. The causal relationship can be proved by use of vaccination to prevent infections.

Chlamydia pneumoniae infection of the central nervous system

Chlamydia pneumoniae is a common respiratory pathogen that is now being implicated in a number of chronic diseases. That the organism can infect vascular endothelium, macrophages and smooth muscle cells suggests that it may play a role in many systemic diseases. The present review focuses on the possibility that the central nervous system can also be a target of this agent. The tropism of C. pneumoniae to the neural tissue suggests it may play a role in diverse neurologic diseases, including Alzheimer's disease, multiple sclerosis and giant-cell arteritis.

Chlamydia pneumoniae in Atherosclerotic Carotid Artery Plaques: High Prevalence among Heavy Smokers

This study was designed to determine the prevalence of Chlamydia pneumoniae in carotid artery plaques. Although there have been numerous studies evaluating coronary plaques for this bacterium fewer studies have assessed noncoronary vasculature. In addition we wished to evaluate whether correlation exists between the presence of C. pneumoniae in carotid plaques and established risk factors for atherosclerosis. Sixty intact carotid artery plaques removed during surgery (carotid endarterectomy) were formalin-fixed and paraffin-embedded according to conventional techniques. These samples were evaluated by polymerase chain reaction analysis to detect presence of C. pneumoniae DNA. Results were tabulated and compared against established risk factors for atherosclerosis: diabetes, hypertension, hyperlipidemia, age, and smoking. Forty-two (70.0%) of the 60 plaques that were evaluated tested positive for the presence of C. pneumoniae DNA by polymerase chain reaction analysis. In the sample defined as being from heavy smokers (greater than 15-pack-year history) 33 (94.3%) of 35 plaques tested positive whereas two (5.7%) tested negative. This correlation demonstrated statistical significance ( P = 1.36 x 10–6, two-tailed Fisher exact test). Presence of C. pneumoniae in carotid plaques demonstrated no statistically significant correlation with diabetes, hypertension, or hyperlipidemia. Age as a risk factor was examined but not statistically evaluated because of the narrow range within our patient sample. Analysis of the data reveals that C. pneumoniae is present in large numbers of atheromatous plaques as is consistent with emerging data. What is interesting though is that 33 (94.3%) of the 35 smokers had plaques that tested positive for the bacterium as opposed to only nine (36.0%) of the 25 nonsmokers. Identification of specific populations exhibiting a high prevalence of C. pneumoniae may serve to focus future studies. Ongoing investigation will seek to determine whether C. pneumoniae plays an active role in the pathogenesis of atherosclerosis.