Relation between direct detection of Chlamydia pneumoniae DNA in human coronary arteries at postmortem examination and histological severity (Stary grading) of associated atherosclerotic plaque

Removal of Polymerase Chain Reaction Inhibitors by Electromembrane Extraction

Polymerase chain reaction (PCR) technology has become the cornerstone of DNA analysis. However, special samples (e.g., forensic samples, soil, food, and mineral medicine) may contain powerful PCR inhibitors. High levels of inhibitors can hardly be sufficiently removed by conventional DNA extraction approaches and may result in the complete failure of PCR. In this work, the removal of PCR inhibitors by electromembrane extraction (EME) was investigated for the first time. To demonstrate the universality of the approach, EME formats with and without supported membranes (termed parallel-EME and μ-EME, respectively) were employed, and both anionic [humic acid (HA)] and cationic (Ca²⁺) PCR inhibitors were used as models. During EME, charged inhibitors in the sample migrate into the liquid membrane in the presence of an electric field and might further leech into the waste solution, while PCR analytes remain in the sample. After EME, the clearance values for HA at 0.2 and 2.5 mg mL^-1 were 94 and 85%, respectively, and that for Ca²⁺ (275 mM) was 63%. Forensic PCR-short tandem repeat (PCR-STR) genotyping showed that EME significantly reduced the interference by HA in PCR-STR analysis and displayed a higher HA purge capability compared to existing methods. Furthermore, by combining EME with liquid-liquid extraction or solid-phase extraction, satisfactory STR profiles were obtained from HA-rich blood samples. In addition, false-negative reports of bacterial detection in mineral medicine and shrimps were avoided after the removal of Ca²⁺ by μ-EME. Our research demonstrates the great potential of EME for the purification of DNA samples containing high-level PCR inhibitors and opens up a new application direction for EME.

Gut microbiota and atherosclerosis: role of B cell for atherosclerosis focusing on the gut-immune-B2 cell axis

Atherosclerosis is the leading cause of cardiovascular mortality and morbidity worldwide and is described as a complex disease involving several different cell types and their molecular products. Recent studies have revealed that atherosclerosis arises from a systemic inflammatory process, including the accumulation and activities of various immune cells. However, the immune system is a complicated network made up of many cell types, hundreds of bioactive cytokines, and millions of different antigens, making it challenging to readily define the associated mechanism of atherosclerosis. Nevertheless, we previously reported a potential persistent inflammatory process underlying atherosclerosis development, centered on a pathological humoral immune response between commensal microbes and activated subpopulations of substantial B cells in the vicinity of the arterial adventitia. Accumulating evidence has indicated the importance of gut microbiota in atherosclerosis development. Commensal microbiota are considered important regulators of immunity and metabolism and also to be possible antigenic sources for atherosclerosis development. However, the interplay between gut microbiota and metabolism with regard to the modulation of atherosclerosis-associated immune responses remains poorly understood. Here, we review the mechanisms by which the gut microbiota may influence atherogenesis, with particular focus on humoral immunity and B cells, especially the gut-immune-B2 cell axis.

Graphical abstract

Role of gut microbiota in atherosclerosis

Infections have been linked to the development of cardiovascular disease and atherosclerosis. Findings from the past decade have identified microbial ecosystems residing in different habitats of the human body that contribute to metabolic and cardiovascular-related disorders. In this Review, we describe three pathways by which microbiota might affect atherogenesis. First, local or distant infections might cause a harmful inflammatory response that aggravates plaque development or triggers plaque rupture. Second, metabolism of cholesterol and lipids by gut microbiota can affect the development of atherosclerotic plaques. Third, diet and specific components that are metabolized by gut microbiota can have various effects on atherosclerosis; for example, dietary fibre is beneficial, whereas the bacterial metabolite trimethylamine-N-oxide is considered harmful. Although specific bacterial taxa have been associated with atherosclerosis, which is supported by increasing mechanistic evidence, several questions remain to be answered to understand fully how the microbiota contributes to atherosclerosis and cardiovascular disease. Such knowledge might pave the way for novel diagnostics and therapeutics based on microbiota.

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.

Differential identification of atypical pneumonia pathogens in aorta and internal mammary artery related to ankle brachial index and walking distance

BACKGROUND

We studied the existence of agents in aorta biopsies, such as Chlamydia pneumoniae, cytomegalovirus, and Mycoplasma pneumoniae, that are thought to have a role in atherosclerosis etiopathogenesis role, and their association with peripheral artery disease.

MATERIALS AND METHODS

We examined aorta wall and internal mammarian artery (IMA) biopsies taken from two different places in 63 patients in whom coronary artery bypass was performed. In these biopsies, we evaluated the deoxyribonuclease (DNA) of these microorganisms using polymerase chain reaction. From the same patients, we recorded the ankle brachial index, road walking distance information, lipid profile, C-reactive proteins, blood parameters such as fibrinogen, and the patient's operation data.

RESULTS

In the nine aorta biopsies taken from 63 patients, we isolated C pneumoniae DNA. In IMA biopsies taken from the same patients, we detected no microorganism DNA (P < 0.001). In the same aorta biopsies, we found no cytomegalovirus or M pneumoniae DNA. We examined 12 patients using an index value of 0.9 in the ankle brachial index evaluation; eight had C pneumoniae in the aorta biopsies (P < 0.001).

CONCLUSIONS

We found a significant relationship between C pneumoniae DNA and the existence of peripheral artery disease. In the development of atherosclerosis with C pneumoniae, there may be a determinant pathogen in both the aorta and the peripheral arteries. The nonexistence of C pneumoniae DNA in the IMA biopsies may indicate infectious agents because of the predominant endothelial functions in this artery, and thus its resistance to atherosclerosis.

Chlamydia pneumoniae IgG and IgA antibody titers and prognosis in patients with coronary heart disease: results from the CLARICOR trial

The association observed between coronary heart disease (CHD) and Chlamydia (Chlamydophila) pneumoniae antibodies prompted, during the 1990s, several primary and secondary prevention trials with various antibiotics. In our CLARICOR trial, a randomized placebo-controlled trial in 4372 patients with stable CHD, a brief clarithromycin regimen was followed, unexpectedly, by increased long-term mortality. We now compare C. pneumoniae antibody levels at entry with population levels, with the patients' individual histories, and with their subsequent outcomes. IgG antibody levels were somewhat raised, but elevated IgA and IgG titers were unrelated to entry data (including prior acute myocardial infarction), except for an association with smoking and with not using statins. Hazards of mortality and of other outcomes tended to slightly increase with IgA and decrease with IgG titers, but the unfavorable clarithromycin effect was unrelated to antibody levels and remains unexplained. Smoking-related lung disease probably underlies the link between heart disease and increased IgG titers.

Human parvovirus b19 infection in patients with coronary atherosclerosis

BACKGROUND AND AIMS

The identification of possible pathogens for an infectious etiology of atherosclerotic coronary artery disease (CAD) is an expanding field. The present study was undertaken to explore the role of parvovirus B19, a potent infectious agent.

METHODS

A total of 565 patients were analyzed (90 patients with CAD, and 475 controls). Serologic analysis for human paravovirus B19 (B19) specific IgM and IgG was carried out in all patients. In addition, tissue specimens were obtained from five patients who received heart transplants. Direct in situ polymerase chain reaction (PCR) and immunocytochemistry were performed in the samples to localize B19 DNA.

RESULTS

Enzyme immunoassay showed that the seropositive rate of anti-B19 IgG in patients with CAD was 1.5- to 2.7-fold more frequent than in healthy controls. Clinical characteristics did not affect the prevalence of seropositivity for B19. However, anti-B19 IgM and B19-specific DNA were not detected in healthy or individuals with CAD. Furthermore, nonradioactive in situ PCR found that the majority of B19-specific DNA was located in the endothelial cells of the thickened intima.

CONCLUSIONS

Our results first demonstrate a seroepidemiological and histopathological association between chronic B19 infection and CAD, suggesting that B19 infection may have a potential role in the pathogenesis of coronary atherosclerosis.

Chlamydophila pneumoniae infection and COPD: more evidence for lack of evidence?

Chlamydophila pneumoniae has been recognized as a common cause of respiratory tract infections affecting all age groups. The organism has been implicated as an infectious trigger for acute exacerbations of COPD. Moreover, the intracellular existence of this pathogen and the ability to cause chronic respiratory infections have led to a number of studies that investigated its possible association with disease development. The present paper examines and discusses the possible association of acute C. pneumoniae infection in episodes of acute exacerbation of COPD. It also reviews the existing evidence of chronic C. pneumoniae infection with disease pathogenesis and severity. The significant interstudy variation of the choice of diagnostic methods and criteria applied is most likely responsible for the great diversity of results observed. The use of well-standardized, commercially available diagnostic tools, as well as the adoption of a more unified diagnostic approach is probably the key element missing in order to clarify the exact role of C. pneumoniae in COPD.

Severity of carotid atherosclerosis unrelated to Chlamydia pneumoniae infection in acute ischemic stroke patients: a clinicopathological study

BACKGROUND

Both clinical and pathological alterations of the carotid arteries were correlated with Chlamydia pneumoniae infection in 67 acute ischemic stroke patients with severe neurological symptoms.

METHODS

In the clinical study, intima-media thickness (IMT) of the common carotid arteries was determined in vivo by B-mode ultrasound measurement and C. pneumoniae-specific IgG and IgA responses were detected. In the pathological study, the absolute wall thickness of the common, internal and external carotid arteries was measured postmortem in specimens obtained at the autopsy of patients who died due to complications of acute stroke. In the atherosclerotic plaques of the autopsy specimens, C. pneumoniae genomic DNA was detected by polymerase chain reaction amplification.

RESULTS

The Spearman's rho correlation coefficient of IMT with the average wall thickness of the common, internal and external carotid arteries was 0.51 (p = 0.002), 0.34 (p = 0.052) and 0.58 (p < 0.001), respectively. Anti-C. pneumoniae IgG and IgA antibodies were detected in 43 (73%) and 29 (49%) patients, but neither antibody marker correlated with IMT (median: 0.91 mm in IgG positives vs. 0.90 mm in IgG negatives, p = 0.86; 0.88 mm in IgA positives vs. 0.90 mm in IgA negatives, p = 0.53). The presence of C. pneumoniae DNA was detected in the carotid plaques of 21 (54%) of the 39 tested patients, independently of either IMT values or the average wall thickness of all carotid arteries.

CONCLUSIONS

In acute ischemic stroke patients, C. pneumoniae infection was frequently detected in the arteriosclerotic plaques of the carotid arteries but it did not correlate with the severity of carotid arteriosclerosis.

Chlamydia pneumoniae is a likely risk factor for ischemic stroke in young patients

Recently, Chlamydia pneumoniae has been identified as a risk factor for atherosclerosis, cardiovascular disease, and stroke. In young patients the causes of stroke are more diverse, and remain unknown in about 30% of cases, despite thorough investigations. To find a possible relationship between C. pneumoniae infection and stroke at young age, we investigated C. pneumoniae antibody titers in 41 patients with ischemic stroke who were younger than 50 years old and in 55 healthy control subjects. A positive IgA antibody titer to C. pneumoniae was significantly associated with stroke (crude odds ratio 2.1; 90% confidence interval 1.1-9.5; P = .04). After adjusting for hypertension, smoking, and hypercholesterolemia, positive Chlamydia antibodies remained associated with stroke (adjusted odds ratio 2.8; 90% confidence interval 1.1-7.1; P = .04). No significant association between positive IgG antibodies and stroke was found. Because a positive IgA antibody titer may reflect a persistent infection, these data indicate that persistent C. pneumoniae infection may be an independent risk factor for stroke at young age.

Lack of association between infectious burden and carotid atherosclerosis in Japanese patients

Several infectious agents, such as Chlamydia pneumoniae, cytomegalovirus (CMV), herpes simplex virus (HSV), and Helicobacter pylori, have been implicated in the pathogenesis of atherosclerosis; however, but the contribution of infection may vary among races and geographic conditions. The present study investigates the association between the presence of these pathogens and carotid atherosclerosis and examines the relevance of an infectious burden during atherogenesis in Japanese patients undergoing carotid endarterectomy. We investigated a total of 50 carotid atherosclerotic plaques resected during carotid endarterectomy by polymerase chain reaction (PCR) for C. pneumoniae, CMV, HSV, and H. pylori and by immunocytochemistry (ICC) for C. pneumoniae. We also examined the presence of antibodies to IgG and/or IgA for each pathogen in blood samples. We detected HSV DNA in 2 specimens (4%) and positive ICC for C. pneumoniae in 8 (16%). The results of PCR, ICC, or serum antibodies, as well as the number of seropositive antibodies, did not correlate with severely stenotic, ulcerative, or symptomatic plaques. Our findings indicate that the detection rate of infectious agents within atherosclerotic plaques was significantly lower in our patients than that in other studies. Thus, an inflammatory mechanism might not correlate with the pathogenesis of carotid atherosclerosis among Japanese patients with severe carotid artery stenosis.

Elevated levels of anti-Chlamydia pneumoniae IgA and IgG antibodies in young adults with ischemic stroke

INTRODUCTION

Data on the role of Chlamydia pneumoniae in patients with ischemic stroke are inconsistent. We investigated the presence of anti-C. pneumoniae antibodies in young adults with ischemic stroke.

METHODS

94 patients (<55 years) with ischemic stroke and 103 controls were enrolled. Indices of anti-C. pneumoniae IgA and IgG were assessed with an ELISA. We determined OR and 95% CI for the IgA and IgG seropositivity in stroke cases.

RESULTS

Mean IgA and IgG indices were higher in stroke patients vs controls (IgA: 1.40 vs 0.56; P < 0.001; IgG: 0.85 vs. 0.78; P < 0.003). The IgA seropositivity was associated with stroke risk (11.92; 5.94-23.92; P < 0.001) as well as IgG seropositivity was (2.31; 1.15-4.61; P < 0.016). Seropositivity assessed with combined IgA and IgG indices was associated with increased stroke risk (OR 9.35; 95% CI 4.78-18.29; P < 0.0001). After controlling for age and sex, the IgA seropositivity yielded a significantly adjusted OR for stroke (8.95; 4.44-18.07; P < 0.002), while IgG seropositivity did not (0.85; 0.53-1.63).

CONCLUSIONS

We find an increased risk of stroke in young patients seropositive to C. pneumoniae in the IgA antibody class. Further studies to explore this finding are warranted.

Correlation between atherosclerosis and periodontal putative pathogenic bacterial infections in coronary and internal mammary arteries

BACKGROUND

Chronic infections, such as periodontitis, have been associated with an increased risk for atherosclerosis and coronary artery disease. The aim of this study was to investigate biopsy samples of coronary and internal mammary arteries for the presence of putative pathogenic bacteria (Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Tannerella forsythensis), Chlamydia pneumoniae, and human cytomegalovirus (CMV).

METHODS

Patients with a diagnosis of coronary artery disease were included in the study. Fifteen coronary arteries with atherosclerosis and 15 internal mammary arteries without clinically assessable atherosclerotic degeneration were investigated. Both groups of specimens were obtained during coronary artery bypass grafting surgery. In all cases, the coronary and mammary artery specimens were taken from the same patient. The detection of periodontal pathogens, C. pneumoniae, and CMV was done by polymerase chain reaction analysis.

RESULTS

Bacterial DNA was found in nine of 15 (60%) coronary artery biopsy samples: P. gingivalis in eight (53.33%), A. actinomycetemcomitans in four (26.67%), P. intermedia in five (33.33%), and T. forsythensis in two (13.33%) samples; CMV was detected in 10 (66.67%) samples, and C. pneumoniae was detected in five (33.33%) samples. Some of the samples contained more than one type of bacteria. Periodontal pathogens were not detected in internal mammary artery biopsies, whereas CMV was present in seven (46.67%) samples and C. pneumoniae was present in six (40%) samples.

CONCLUSION

The absence of putative pathogenic bacteria in internal mammary arteries, which are known to be affected rarely by atherosclerotic changes, and their presence in a high percentage of atherosclerotic coronary arteries support the concept that periodontal organisms are associated with the development and progression of atherosclerosis.

Chlamydial heat-shock protein 60 : A marker for chronic infection with Chlamydia Pneumoniae in atherosclerosis: Investigation of atherosclerotic coronary arteries by immunocytochemistry

Worldwide, ischemic heart disease is an important cause of death and there is an increasing number of pointers toward a causative connection between Chlamydia pneumoniae and atherosclerosis. The presence, localization, and relationship to atheroma of Chlamydial heat-shock protein 60 (cHsp60) in coronary tissue was investigated by immunocytochemical methods and by different investigators. In the present study, for the first time, arterial segments, including the whole course of the great coronary arteries from proximal to distal, were investigated by immunocytochemistry to detect cHsp60. Specimens from coronary arteries of 46 autopsy cases (17 females, 29 males; mean age: 62.7 years, SD 17.9 years) were examined (480 paraffin-embedded samples; 11 sites from each case). Different fixatives were used for the specimens taken at autopsy. Immunocytochemical staining was done using an anti-cHsp60 antibody (Affinity Bioreagents Inc.) and a modified Labeled-Strept-Avidine-Biotin-staining protocol (DAKO). The localization of signals by site of predilection in the course of coronary vessels and by coincidence with specific structural characteristics, was detected by light microscopy. Detection of cHsp60 was possible in 30 of 46 (65.2%) individuals (minimum one sample) and in 87 of 480 specimens (18.1%). The distribution of the signals was correlated to the intensity of atherosclerosis (mild to middle) and a decreasing frequency from proximal to distal arterial segments was found. Macroscopically, nonatherosclerotic vessels presented cHsp60 only occasionally. In accordance with recent publications, cHsp60 was detected in foam cells and macrophages, cell-poor regions, and thickened intimal layers, and more rarely in inflammatory infiltrates and calcified areas. According to previous studies, a distribution independent from atherosclerotic lesions was not found. Detection of cHsp60 was superior using Notox(®) (Earth Industries) as a fixative in comparison with buffered formaldehyde.

Chlamydia pneumoniae immunoreactivity in coronary artery plaques of patients with acute coronary syndromes and its relation with serology

BACKGROUND

An association between Chlamydia pneumoniae (Cpn) infection and coronary artery disease has been reported and examined by different techniques. However, its immunoreactivity in coronary artery plaques of patients with acute coronary syndrome (ACS) and its relation with serology are less well defined.

METHODS

We divided 40 coronary plaque specimens from 40 patients who underwent thrombectomy or directional coronary atherectomy into an ACS group (n = 22) and a non-ACS group (n = 18). Cpn in specimens was detected immunohistochemically and compared quantitatively. Serum immunoglobulin (Ig)A and IgG antibodies to Cpn and high-sensitivity C-reactive protein (hs-CRP) were measured. The relation between serology and immunohistochemical analysis was also investigated.

RESULTS

Cpn immunopositive cells per square millimeter (Cpn+ cells/mm2) in the ACS group were significantly more numerous than in the non-ACS group (median 7.44 vs 1.50, P = .0018). Cpn IgA seropositivity rates and titers in the ACS group were significantly higher than those in the non-ACS group (86.3% vs 22.2%, P = .0002; median titer 1.403 vs 0.545, P = .003). There were no differences in IgG antibodies between the 2 groups. The hs-CRP values (in milligrams per liter) in ACS group were significantly higher than in non-ACS group (median 2.8 vs 1.2, P = .0019). Serum IgA titers in patients with at least 5 Cpn+ cells/mm2 in the specimens were significantly higher than in patients with fewer Cpn+ cells (median 1.52 vs 0.86, P = .026). There was no difference in serum hs-CRP values in patients with more Cpn+ cells but a trend to an increase.

CONCLUSION

Immunohistology frequently detected Cpn in coronary plaques; Cpn+ cells were more prevalent in plaques associated with ACS, and Cpn IgA but not IgG titers were increased with ACS and with high densities of Cpn+ cells within plaque.

Lack of association between Chlamydia Pneumoniae serology and endothelial dysfunction of coronary arteries

BACKGROUND

Recent publications brought up the hypothesis that an infection with Chlamydia Pneumoniae (CP) might be a major cause of coronary artery disease (CAD). Therefore, we investigated whether endothelial dysfunction (ED) as a precursor of atherosclerosis might be detectable in patients with previous infection with CP but without angiographic evidence of CAD.

METHODS

We included 16 patients (6 male / 10 female) of 52 consecutive patients with normal coronary angiography who had typical angina pectoris and pathologic findings in the stress test. Exclusion criteria were: active smoker, elevated cholesterol, hypertension, age > 65 years, diabetes mellitus, treatment with ACE-inhibitors, or known CAD. Blood sample analysis for serum titer against CP (aCP-IgG) was performed after coronary angiography. We looked for endothelial dysfunction analyzing the diameter of the left anterior descending coronary artery (LAD) before and after acetylcholine (ACh) i. c. Quantitative analysis of luminal diameter (LD) was performed in at least two planes during baseline conditions and after ACh for 2 minutes in dosages of 7.2 microg/min and 36 microg/min with an infusion speed of 2 ml/min. Using Doppler guide wire, the coronary flow velocity was measured continuously in the LAD. The coronary flow velocity reserve (CFVR) was measured after 20 microg adenosine i. c.

RESULTS

10 patients had an elevated aCP-IgG (> 1:8). 6 patients with negative titers (aCP-IgG <or= 1:8) served as control (CTRL). Both groups were comparable in age, gender, angina class, results of non-invasive stress-test and the baseline values of LD and flow. In the CP positive group 3 patients (30%) did not show an increase of LD after ACh as evidence of ED. In the CTRL group 4 patients (67 %) had ED. There was no association between aCP-IgG and changes of coronary blood flow after ACh. All patients showed normal CFVR (3.0 +/- 0.27) irrespective of their aCP-IgG values.

CONCLUSION

In patients with typical symptoms of coronary ischemia but without angiographically visible CAD and absence of other factors affecting the endothelial function, a previous infection with CP is not associated with endothelial dysfunction.

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.

Detection of Chlamydia pneumoniae in atherosclerotic coronary arteries

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

Polymorphism of the 3'-Untranslated Region of Interleukin-12 p40 Gene is not Associated With the Presence or Severity of Coronary Artery Disease

BACKGROUND

Interleukin (IL)-12 is thought to play an important role in the development of atherosclerosis and recently, polymorphism of the 3'-untranslated region of the IL-12 p40 gene (A1188C) was reported to be associated with diabetes and multiple sclerosis. However, the association between this genetic polymorphism and coronary artery disease (CAD) has not been studied.

METHODS AND RESULTS

The frequency of this polymorphism was investigated in 555 patients undergoing coronary angiography: 395 had CAD, of whom 161 also had a myocardial infarction (MI). With regard to the IL-12 p40 polymorphism, 125 had the A/A, 268 had the A/C, and 162 had the C/C genotype. The prevalence of CAD did not differ among the groups (71%, 73%, and 69%, respectively; p= NS). The prevalence of MI was also similar among the groups (28%, 27%, and 33%, respectively; p= NS). Moreover, the number of >50% stenotic vessels, >50% stenotic segments, and < or =50% stenotic segments did not differ among the 3 groups.

CONCLUSIONS

Polymorphism of IL-12 p40 gene was not found to be associated with the presence or severity of CAD, suggesting that it does not play an important role in the development of this disease.

Association of Mycoplasma pneumoniae infection with coronary artery disease and its interaction with chlamydial infection

Mycoplasma pneumoniae (MP) seropositivity was reported to be associated with coronary events. MP organisms were detected with Chlamydia pneumoniae (CP) in coronary plaques. We investigated MP and CP seropositivity in 549 patients undergoing coronary angiography. Coronary artery disease (CAD) was found in 396 patients, of whom 154 had myocardial infarction (MI). MP seropositivity was more prevalent in patients with CAD than without CAD (14% versus 6%, P < 0.01). The highest prevalence was found in patients with MI. In contrast, the prevalence of CP seropositivity was similar in patients with and without CAD (62% versus 59%). To clarify interaction with CP infection, 549 patients were divided into two groups with and without CP seropositivity. Among patients with CP seropositivity, MP seropositivity was more prevalent in patients with CAD than without CAD (17% versus 5%, P < 0.01), whereas among patients without CP seropositivity, MP seropositivity did not differ between patients with and without CAD (9% versus 6%). In multivariate analysis, MP seropositivity was associated with CAD only in patients with CP seropositivity (odds ratio = 5.1, 95% CI = 1.8-14.9). Thus, MP seropositivity was associated with CAD. However, this association was confined to patients with CP seropositivity. Coinfection by MP and CP may be an important cofactor for CAD.

Is the perceived association between Chlamydia pneumoniae and vascular diseases biased by methodology?

Inter- and intralaboratory inconsistencies in detection rates of Chlamydia pneumoniae in vascular specimens have been demonstrated. In this study, 66 vascular tissue specimens from 66 patients with vascular disease were tested by three PCR assays: a 16S PCR-based reverse line blot (RLB) assay, a single-step PCR, and a nested PCR. Also, we explored the impacts of different DNA polymerase enzymes on the results based on gel electrophoresis and hybridization. The PCR results by gel electrophoresis in the single-step PCR depended on which DNA polymerase was used. All samples were negative with AmpliTaq Gold DNA polymerase, and 54.5% (36 of 66) were positive with the conventional Taq DNA polymerase. All samples were negative after hybridization with a C. pneumoniae-specific probe. In the nested PCR, all specimens were negative by gel electrophoresis and after hybridization. The RLB assay failed to detect C. pneumoniae in any specimen; however, 20 specimens were Chlamydia sp. positive. The sequence analysis of six of these samples demonstrated Chlamydia-like organisms. RLB detected Chlamydia sp. DNA in water and in the elution buffer after passage of the Qiagen columns (11 of 40). This study identified factors that may influence the detection of C. pneumoniae DNA in vascular tissues and consequently bias the perception of a link between C. pneumoniae and vascular diseases. The following are strongly recommended: to use DNA polymerases that have to be activated, to decontaminate with dUTP-uracil-DNA glycosylase, to hybridize with specific probes, to include sufficient controls, and to use molecular grade water.

Heart disease: the greatest 'risk' factor of them all

By the turn of the last century, flying in the face of over a hundred years of research and clinical observation to the contrary, medicine abandoned the link between infection and atherogenesis; not because it was ever proven wrong, but because it did not fit in with the trends of a medical establishment convinced that chronic disease such as heart disease must be multifactorial, degenerative and non-infectious. Yet it was the very inability of 'established' risk factors such as hypercholesterolemia, hypertension and smoking to completely explain the incidence and trends in cardiovascular disease that resulted in historically repeated calls to search out an infectious cause, a search that began more than a century ago. Today, half of US heart attack victims have acceptable cholesterol levels and 25% or more have none of the "risk factors" associated with heart disease, including smoking, high blood pressure or obesity, most of which are not inconsistent with being caused by infection. Even the case of the traditionalist's latest 2003 JAMA assault to 'debunk' what they call the "50% risk factor myth" falls woefully short under scrutiny. In one group 30% died of heart disease with a cholesterol of at least 240 mg/dl, a condition which also existed in 21% who did not die during the same period. And the overlap was obvious throughout the so-called risk categories. Under such scrutiny, lead author Greenland conceded that if obesity, inactivity and elevated cholesteriol in the elderly are included, just about everyone has a risk factor and he likened the dilemma of people who do or do not wind up with heart disease akin to the susceptibility of people who are exposed to tuberculosis but do not get the disease. In Infections and Atherosclerosis: New Clues from an old Hypothesis? Nieto stressed the need to extend the possible role of infectious agents beyond the three infections which have in recent years been the focus of research: Cytomegalovirus (CMV) Chlamydia pneumoniae and Helicobactor pylori. Mycobacterial disease shares interesting connections to heart disease. Not only is tuberculosis the only microorganism to depend on cholesterol for its pathogenesis but CDC maps for cardiovascular disease bear a striking similarity to those of State and regional TB case rates. Ellis, Hektoen, Osler, McCallum, Swartz, Livingston and Alexander-Jackson all saw clinical and laboratory evidence of a causative relationship between the mycobacteria and heart disease. And Xu showed that proteins of mycobacterial origin actually led to experimental atherosclerosis in laboratory animals Furthermore present day markers suggested as indicators for heart disease susceptibility such as C-Reactive Protein (CRP), interleukin-6 and homocysteine are all similarly elevated in tuberculosis. It therefore behooves us to explore the link between heart disease and typical and atypical tuberculosis.

Chlamydia pneumoniae in coronary bypass grafts of redo patients. The concept of the ‘adventitial baseline infection’

The pathogenic role of Chlamydia pneumoniae in late coronary bypass graft failure has not yet been extensively investigated. We examined failed and new arterial/venous bypass grafts using immunohistochemistry, polymerase chain reaction (PCR), and serology. Thirty-four long-term failed grafts and 28 new grafts were examined in 21 patients undergoing redo coronary artery bypass grafting (CABG). Immunohistochemically, 28 (82%) failed grafts were positive in the intimal-medial compartment, and 33 grafts (97%) were positive for C. pneumoniae in the adventitia. Thirteen (46%) and 27 (96%) new grafts showed infection in the intima-media and in the adventitia, respectively (p < 0.05). Immunohistochemically, the overall presence of C. pneumoniae in all vessels examined was 66% in the intima-media and 97% in the adventitia (p < 0.05). C. pneumoniae was detected by PCR in 19 (31%) of all the vessels examined. C. pneumoniae seems to be frequently present in grafts of patients considered for redo CABG in Hungary. The adventitia of both failed, and new grafts particularly often contained C. pneumoniae. The results suggest that there exists an adventitial baseline infection from which infection of the inner wall layers develops, depending on local microenvironmental conditions. This is the first study to evaluate chlamydial infection in arterial/venous coronary grafts by immunohistochemistry, PCR, and serology.

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.

DETECTION OF CHLAMYDIA PNEUMONIAE IN LIVER TRANSPLANT PATIENTS WITH CHRONIC ALLOGRAFT REJECTION

BACKGROUND

Chlamydia pneumoniae is one of the possible pathogenetic factors of atherosclerotic processes. Foam cell arteriopathy is a generally accepted pathologic feature of chronic liver allograft rejection and has several similarities to the early lesions of atherosclerosis. The aim of the authors' study was to show any existing correlation between the occurrence of Chlamydia pneumoniae and the presence of foam cell arteriopathy in transplanted livers with chronic rejection.

METHODS

Ten liver samples from patients with chronic liver rejection including foam cell arteriopathy and 10 liver samples from healthy individuals were analyzed for the presence of Chlamydia pneumoniae by specific immunohistochemistry and polymerase chain reaction (PCR). Liver samples from two transplant patients with chronic liver rejection without any evidence of foam cell arteriopathy and nine patients with acute liver allograft rejection were also investigated by PCR.

RESULTS

In all 10 rejected liver samples, Chlamydia pneumoniae was detected by PCR, whereas only one of the healthy control samples and one of the samples with acute rejection were found to be positive. Immunohistochemistry showed similar results. The positive signals of Chlamydia pneumoniae were localized mainly in the hepatocytes, sinusoidal and perisinusoidal cells, and the cells of portal tracts, whereas most of the altered hepatic arteries showed no or very weak positivity.

CONCLUSIONS

The results strongly suggest an association between the occurrence of Chlamydia pneumoniae and the presence of foam cell arteriopathy in transplanted livers.

Vaccination and atherosclerosis

Atherosclerosis is an inflammatory disease. Both innate and adaptive immunity are involved in lesion formation and development. A number of antigen candidates, such as oxidized low-density lipoprotein and heat shock protein, have been associated with the inflammation and immune reaction that is part of the atherosclerotic process. Because experimental models of some other inflammatory/autoimmune diseases can be improved by vaccination, it is of interest to investigate if vaccination can also be applied to prevent or retard atherosclerosis. Indeed, the modification of immune responses in animal models can greatly affect the development and progression of atherosclerosis. This review provides an overview of our current understanding of effects and proposed mechanisms of immunization on preventing atherosclerosis.

Serologic markers of persistent Chlamydia pneumonia infection and long-term prognosis after successful coronary stenting

BACKGROUND

Previous studies have shown an incremental role of inflammation in late prognosis following coronary stenting (CS). In particular, high preprocedural levels of plasma C-reactive protein (CRP) have been related to increased hazard of late ischemic complications. Persistent Chlamydia pneumoniae (Cp) infection, detected by positive IgA anti-Cp titers, may be associated with this inflammatory process and portend a high risk of late adverse prognosis after CS.

METHODS

A total of 483 consecutive patients with either stable or unstable coronary syndromes were followed-up for 1 year after successful CS. The composite of cardiac death, myocardial infarction, rehospitalization for rest-unstable angina, and exertional angina, whichever occurred first, was the clinical end point. Additionally, the rate of in-stent restenosis and progression of coronary artery disease during this period were evaluated. Anti-Cp titers and plasma CRP levels were measured before the procedure.

RESULTS

Positive immunoglobulin A (IgA), but not positive immunoglobulin G (IgG), titers were significantly associated with high plasma CRP levels in patients with unstable coronary syndromes (P =.005), but not in those with stable angina (P =.7). Moreover, positive IgA titers were significantly related to increased risk of both the composite clinical end point (P =.04) and progression of coronary artery disease (P <.001) in patients with unstable coronary syndromes but not in those with stable angina. Neither positive IgA nor positive IgG titers were associated with the rate of in-stent restenosis.

CONCLUSIONS

Persistent Cp infection may drive an inflammatory response in the coronary vasculature and portends an adverse late outcome after CS in patients with unstable coronary syndromes.

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.

Identification and quantification of Chlamydia pneumoniae in human atherosclerotic plaques by LightCycler real-time-PCR

A real-time PCR assay for Chlamydia pneumoniae in human atherosclerotic plaques by the use of novel probes and FRET LightCycler technology, is described. The assay proved particularly suitable for the specific and quantitative detection of a low DNA copy number in conventional PCR-negative samples. Among fifteen nested-PCR negative atherosclerotic plaques examined, our method detected three positive plaques containing 50(+/-3), 37(+/-2) and 24(+/-2) DNA copy number+/-SD in three independent experiments. Real-time PCR holds promise for C. pneumoniae quantitation in human atherosclerotic plaques.

Limited association of Chlamydia pneumoniae detection with coronary atherosclerosis

The association of Chlamydia pneumoniae (C. pneumoniae) detection with atherosclerosis has been controversial because of recent conflicting results. In order to assess how and to what extent C. pneumoniae detection contributes to atherosclerosis, the association between immunohistochemical detection of C. pneumoniae antigen, intimal lesions, and the intimal thickening ratio was examined in 1674 left anterior descending coronary arterial segments from 100 autopsied Japanese patients being free from coronary heart disease. These specimens contained full spectrum of atherosclerotic lesions as defined by the American Heart Association classification. The intimal thickening ratio increased in C. pneumoniae-positive sections comparing to that in C. pneumoniae-negative sections only in the group with normal intima and diffuse intimal thickening, but there was no such association in the other advanced intimal lesion groups. Furthermore, in 50 C. pneumoniae-positive cases out of 100 investigated, the frequency and extent of immunoreactivity did not associate with progression of intimal lesions or the intimal thickening ratio, and the mean score of C. pneumoniae detection did not correlate with the mean intimal thickening ratio in individual cases. These results suggest only a limited association between C. pneumoniae detection and coronary atherosclerosis development and that C. pneumoniae does not influence promotion of atherosclerotic lesions. The role of C. pneumoniae on atherogenesis may be limited only at the beginning stage of atherosclerosis development.

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.

Infectious agents in coronary atheromas: a possible role in the pathogenesis of plaque rupture and acute myocardial infarction

In this review we report our recent findings of histopathological features of plaque instability and the association with Mycoplasma pneumoniae (MP) and Chlamydia pneumoniae (CP) infection, studying thrombosed coronary artery segments (CAS) of patients who died due to acute myocardial infarction. Vulnerable plaques are known to be associated with fat atheromas and inflammation of the plaque. Here we demonstrated that vulnerability is also related with focal positive vessel remodeling that maintains relatively well preserved lumen even in the presence of large atheromatous plaques. This phenomena may explain why the cinecoronariography may not detect large and dangerous vulnerable plaques. Greater amount of these bacteria in vulnerable plaques is associated with adventitial inflammation and positive vessel remodeling: the mean numbers of lymphocytes were significantly higher in adventitia than in the plaque, good direct correlation was obtained between numbers of CD20 B cells and numbers of CP infected cells in adventitia, and between % area of MP-DNA in the plaque and cross sectional area of the vessel, suggesting a cause-effect relationship. Mycoplasma is a bacterium that needs cholesterol for proliferation and may increase virulence of other infectious agents. In conclusion, co-infection by Mycoplasma pneumoniae and Chlamydia pneumoniae may represent an important co-factor for plaque instability, leading to coronary plaque thrombosis and acute myocardial infarction, since larger amount of these bacteria strongly correlated with histological signs of more vulnerability of the plaque. The search of CMV and Helicobacter pilori in these tissues resulted negative.

Chlamydia pneumoniae in atherosclerotic lesions of patients undergoing vascular surgery

The pathophysiological implications of Chlamydia pneumoniae in atherosclerotic lesions and its contribution to atherosclerotic complications remain unclear. Therefore, the purpose of the present study was to evaluate whether or not there is an association between the presence of Chlamydia pneumoniae in atherosclerotic lesions and the clinical manifestations as well as risk factors of atherosclerotic disease in patients undergoing vascular surgery. Specimens from atherosclerotic arteries were collected during endarterectomy of the carotid artery (n = 15), endarterectomy of the femoral artery (n = 19), or repair of an abdominal aortic aneurysm (n = 28). Detection of Chlamydia pneumoniae was performed by using immunohistochemical staining (IHC) with specific antibodies. Clinical manifestations of atherosclerotic disease were defined by the presence of cardiovascular risk factors, coronary heart disease, and previous vascular surgery. Inflammatory serum markers were determined in all patients prior to surgery. The specimens of all 62 patients revealed severe atherosclerosis in histological examination and a positive IHC was observed in 41 samples (66%). There were no differences regarding cardiovascular risk factors, coronary heart disease, events of previous vascular surgery, or inflammatory serum markers when comparing patients with positive and negative IHC. In conclusion, our findings showed no correlation between clinical or laboratory parameters of atherosclerosis and the presence of Chlamydia pneumoniae in atherosclerotic lesions. Therefore, Chlamydia pneumoniae appears to be a concomitant phenomenon rather than a causative principle in atherosclerosis.

Antibodies against Chlamydia pneumoniae and their relation to lymphocyte population levels

Chlamydia pneumoniae infection has long been suspected as a possible cause of atherosclerosis and has been frequently detected in atheromatous plaques of the coronary arteries. Nevertheless, its distribution is not correlated to the severity or extent of the disease, but it would support the hypothesis that the organism may be an active factor in the pathogenesis of atherosclerosis. A group of patients with stable angina were examined as to whether or not the positivity of antibodies against Chlamydia pneumoniae modified cellular populations as mechanisms responsible for the alterations of inflammatory response. We concluded that the presence of IgG anti-C. pneumoniae antibodies do not participate in the activation of inflammatory mechanisms that may intervene in the genesis of atherosclerosis in patients with stable angina.

Chronic infections and atherosclerosis/thrombosis

An emerging pathophysiologic paradigm implicates chronic inflammation in the initiation, progression, and destabilization of atherosclerotic vascular disease. Various potential contributors to the inflammatory response in the vessel wall include atherogenic lipids, mechanical stress and injury, hypertension and angiotensin II, cigarette smoking, immune response to neoantigens, and chronic infections with viruses and or bacteria (Table 1). The potential link between chronic infection and atherosclerosis/thrombosis is under extensive investigation in several laboratories around the world. Although indirect evidence and experimental data tend to support this link, definitive proof is still lacking. If such a link is eventually proven to be causal in nature, it will provide a novel target for preventive and therapeutic strategies (anti-infective drugs, vaccines, etc.) against a common disease that is the leading killer of people in Western nations. Results of ongoing, large-scale clinical trials are eagerly awaited.

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: 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.

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.

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.

Effects of interleukin-1 gene polymorphisms on the development of coronary artery disease associated with Chlamydia pneumoniae infection

OBJECTIVES

This study was done to elucidate the effects of interleukin (IL)-1 gene polymorphisms on coronary artery disease (CAD) associated with Chlamydia pneumoniae (CP) infection.

BACKGROUND

It was suggested that CP was associated with CAD. However, genetic factors involved in CAD associated with CP infection are unknown.

METHODS

We evaluated CP immunoglobulin G (IgG) seropositivity and IL-1 beta (a C/T transition at -511) and IL-1 receptor antagonist (IL-1Ra) (a variable-number repeat in intron 2) gene polymorphisms in 292 patients undergoing coronary angiography.

RESULTS

Seropositivity for CP was present in 61% of patients with CAD versus 51% without CAD (p = NS). The percentage of patients having IL-1 beta (-511) C/C genotype and/or IL-1Ra (intron 2) 2- or 3-repeat allele was higher in patients with CAD than without CAD (29 vs. 16%, p < 0.025). To clarify the effects of these CAD-associated variants (IL-1 beta C/C and/or IL-1Ra 2- or 3-repeat), patients were divided into four groups. A stepwise increase in CAD prevalence was observed depending on CP seropositivity and the variants. Odds ratios (ORs) for CAD were 1.4 in the group with seropositivity alone, 1.7 with the variants alone and 3.8 with seropositivity and the variants. Such variants were associated with CAD in both patients with and without seropositivity. Interestingly, high prevalence of myocardial infarction (MI) was confined to the group with seropositivity and the variants (OR, 2.8). The variants were associated with MI only in patients with CP seropositivity.

CONCLUSIONS

The IL-1 gene polymorphisms were found to play a role in the development of CAD, especially MI, in patients with CP infection.

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.

The adventitia of atherosclerotic coronary arteries frequently contains Chlamydia pneumoniae

The presence of Chlamydia pneumoniae in the human arterial system has mainly been determined in atherosclerotic plaque, whereas the adventitia has remained relatively unexplored. We assessed the presence of C. pneumoniae in all three vessel wall layers of coronary (n=72) and brachial (n=48) arteries in relation to local atherosclerosis. Immunohistochemical staining of C. pneumoniae was observed in plaque and adventitia. Cells stained for C. pneumoniae were detected in the same areas as cells stained for macrophages in adjacent sections. C. pneumoniae staining in the adventitia was associated with the extent and severity of atherosclerosis. Coronary sections with C. pneumoniae staining in both adventitia and plaque more often contained advanced atherosclerosis than sections with staining only in the adventitia. Staining was observed more often in the coronary artery than in the brachial artery (24/72 vs. 5/48 and 51/72 vs. 8/48 for plaque and adventitia, respectively, P=0.004 and P<0.001). PCR confirmed the presence of C. pneumoniae DNA in the adventitia. In summary, the adventitia of atherosclerotic coronary arteries frequently contains C. pneumoniae that seems to be located within macrophages. These results might indicate a possible route for infected circulating macrophages to home into atherosclerotic lesions in the artery via vasa vasorum.

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.

The role of inflammation and infection in coronary artery disease

New insights into atherosclerosis, the most common disease affecting coronary arteries, may change therapeutic strategies from largely symptomatic to causal. Atherosclerotic plaques contain a lipid-related, immune-mediated inflammation, with release of secretory products capable of changing plaque morphology. Plaques prone to complications contain large numbers of inflammatory cells; stable plaques contain little inflammation. Similarly, atherectomy specimens from patients with coronary syndromes revealed more inflammatory cells in unstable than in stable patients. These observations, and the fact that acute coronary syndromes are associated with increased blood levels of inflammatory markers, have renewed interest in the possible relationship between infection and atherogenesis. Of all potential candidate antigens, Chlamydia pneumoniae presently is considered the most likely because a substantial number of patients with unstable syndromes contain C. pneumoniae-reactive T cells, both in blood and within the atherosclerotic plaque, suggesting enhancement of intraplaque inflammation.