Chlamydia pneumoniae in human abdominal aortic aneurysms

Matrix Metalloproteinases in the Aneurysm Wall of Patients Treated with Low-Dose Doxycycline

The purpose of this study was to determine the effect of low-dose doxycycline on matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP)-1 expression in the wall of abdominal aortic aneurysms.

A double-blind, randomized study was conducted of patients treated with doxycycline (100 mg/d orally) or placebo for 1 month prior to surgery. MMP-2, -3, and -9 (zymogen and activity); MMP-1, -2, -3, -7, -9, -11, -12, and -14; and TIMP-1 (messenger ribonucleic acid [mRNA]) were measured in the aneurysm wall.

No differences were found between the treatment and placebo groups in zymogen levels of MMP-2, -3, or -9 or in the free or total activities of MMP-2 and -9. Treatment with doxycycline also had no effect on the concentration of any mRNA measured. No relationship was found between the number of tablets taken and MMP or TIMP protein, mRNA, or activity levels in the aneurysm wall.

Low-dose doxycycline treatment does not alter the expression or activity of metalloproteinases or their inhibitor, TIMP-1, in the aneurysm wall.

Chlamydia pneumoniae antibodies and C-reactive protein levels in patients with abdominal aortic aneurysms

INTRODUCTION

The study aim was to assess the relationship between the presence of antibodies to Chlamydia pneumoniae and abdominal aortic aneurysm (AAA) incidence.

PATIENTS AND METHODS

Consecutive AAA patients and AAA-free controls were recruited prospectively. Serum samples from both groups were examined to determine Immunoglobulin (Ig) A and IgG titres against Chlamydia pneumoniae by ELISA and C-reactive protein (CRP) concentrations. Results were expressed as mean (SD) or median (IQR) and compared using χ (2) and Mann-Whitney U tests. A P value of <0.05 was considered statistically significant.

RESULTS

Each study group (AAA/nAAA) comprised 250 patients. 196 (78.7%) AAA patients had positive IgA antichlamydial antibody titres, compared to 181 (72.4%) in the control group (P = 0.008, OR 2.0, 95% CI 1.2-3.5). However, positive IgG antibody titres were similar (191 versus 203; P = 0.222, OR 0.7, 95% CI 0.4-1.3). Average CRP concentrations were higher in AAA individuals. IgA or IgG antibody titres were not related to CRP concentrations.

CONCLUSIONS

These results demonstrated that the frequent incidence of Chlamydia pneumoniae antibodies within the general population makes it difficult to relate its presence to AAA development, despite the high IgA antibody titres. In addition, raised CRP concentrations in AAA patients are not related to the presence of antichlamydial antibodies.

The association between serological markers for Chlamydophila pneumoniae and the development of abdominal aortic aneurysm

BACKGROUND

To investigate the association between serological markers for Chlamydophila pneumoniae (Cpn) and the development of abdominal aortic aneurysm (AAA) in a population-based case-control study.

METHODS

A screening for AAA among 65-75-year-old men and women was performed in a population with high prevalence of disease. Most of the subjects had undergone previous testing at the age of 60, including blood sampling. A total of 42 patients with AAA were compared with 100 age- and gender-matched controls with normal aortas. Cpn immunoglobulin A (IgA) and immunoglobulin G (IgG) antibodies present in plasma samples obtained at the time of screening (current) and in the past 5-15 (mean, 12) years (historical) were analyzed. Cpn antibody titers (<1/64, 1/64, 1/264, and 1/1024) were analyzed using the microimmunofluorescence technique.

RESULTS

No differences in current Cpn immunoglobulin A and IgG antibodies titers (p = 0.111 and 0.659), historical titers (p = 0.449 and 0.228), or titer change (delta) (p = 0.794 and 0.172) were observed between patients with AAA and controls. In all, 82% of the patients with AAA had a current Cpn IgG titer of 1/1024 as compared with the 70% of the control group. All 11 patients who had an aortic diameter of >40 mm reported having high current Cpn IgG titers. The fact that such a large proportion of the healthy population demonstrated an immune response against Cpn made it difficult to demonstrate possible effects of Cpn infection on AAA formation in a case-control study.

CONCLUSION

No significant associations were found between AAA detected by screening and Cpn antibody titer levels at the time of screening or during past screening at the age of 60.

Persistent Chlamydophila pneumoniae infection in thoracic aortic aneurysm and aortic dissection?

OBJECTIVES

Chlamydophila pneumoniae (C. pneumoniae) has been associated with atherosclerosis and abdominal aortic aneurysm and is probably disseminated by peripheral blood mononuclear cells (PBMC). Viable and metabolically active bacteria can be demonstrated by the presence of bacterial mRNA and on-going dissemination by the presence of bacteria in PBMC. The aim of this study was to determine the prevalence of C. pneumoniae DNA and mRNA in aortic biopsies and C. pneumoniae DNA in PBMC in thoracic aortic aneurysm and aortic dissection patients.

DESIGN

Real-time PCR was used to detect C. pneumoniae DNA and mRNA in biopsies and C. pneumoniae DNA in PBMC.

RESULTS

C. pneumoniae DNA was found in biopsies in 26% (6/23) of aneurysm patients and 11% (2/18) of dissection patients but in none of the forensic autopsy controls. C. pneumoniae mRNA was not found in any biopsy, and all PBMC were C. pneumoniae-negative.

CONCLUSIONS

Presence of C. pneumoniae DNA but not mRNA in aortic biopsies and no evidence of C. pneumoniae in PBMC suggest that the infection in the aorta has passed into a state of persistence.

Chlamydial lipopolysaccharide (cLPS) is present in atherosclerotic and aneurysmal arterial wall--cLPS levels depend on disease manifestation

BACKGROUND

The role of Chlamydia pneumoniae in peripheral atherosclerosis disease and abdominal aortic aneurysm (AAA) remains unclear. Chlamydial lipopolysaccharide (cLPS) detection is a method used conventionally in routine chlamydial diagnosis of gynecological or ophthalmic samples.

METHODS

We compared cLPS concentrations, as well as other markers of bacterial load, in plaques and sera of patients operated on for carotid artery stenosis (n=110), aorto-occlusive disease (n=22), or AAAs (n=50) at the Helsinki University Central Hospital.

RESULTS

The median levels of cLPS in plaques were 2.28, 0.80, and 0.29 ng/ml in AAA, aorto-occlusive disease, and carotid artery stenosis patients, respectively (P<.001, Kruskal-Wallis). cLPS in serum correlated with LPS binding protein levels (Spearman's rho=0.52, P<.001), suggesting that the presence of chlamydiae is sufficient to produce an innate immune response reaction in these patients. Serum inflammatory markers interleukin 6 and highly sensitive C-reactive protein also correlate with cLPS (Spearman's rho=0.42 and 0.51, respectively, P<.001).

CONCLUSIONS

cLPS is present in arterial disease, and the potential role of C. pneumoniae in the pathogenesis of both peripheral atherosclerosis disease and AAA should not be forgotten. cLPS has a positive correlation with serum inflammatory markers, but this is no proof of a causal association.

Thoracic aortic aneurysm patients with Chlamydophila pneumoniae infection showed a shift in trace element levels in serum and diseased aortic tissue

Few studies have been performed on trace elements in tissues and serum in cardiovascular disease and none in aortic aneurysm. In this study the concentrations of 10 trace elements were determined in serum and aneurysmatic aortic tissue from 23 patients undergoing thoracic surgery. Macroscopically, normal thoracic aortic tissue specimens from 10 forensic autopsies and serum from 23 healthy blood donors served as controls. DNA from the intracellular respiratory pathogen Chlamydophila pneumoniae (C. pneumoniae), which may be involved in the pathogenesis of atherosclerosis, was found in 26% (6/23) of the patients but in none of the controls. The serum copper/zinc ratio, a well-known marker of ongoing infection and/or inflammation, was higher (26%, p<0.001) in aneurysm patients. C. pneumoniae requires iron for its growth. In our aneurysm patients iron was higher in serum (by 54%, p<0.001) and aneurysmal tissue (by 60%, p<0.001). Although calcium was lower in patient sera (by 8%, p<0.001), it tended to be higher (by 20%, ns) in aneurysmatic tissue. In addition, mercury concentrations in serum and aneurysmatic tissue were positively correlated (r=0.51, p<0.05). Moreover, C. pneumoniae-positive aneurysmatic tissues had lower concentrations of manganese (46%, p<0.05) and zinc (26%, ns) but a higher concentration of mercury (50%, p<0.05) than C. pneumoniae-negative aneurysmatic tissues. In conclusion, aneurysm patients showed a shift in trace element levels in serum and in the diseased part of the aorta, the pattern being partly different in C. pneumoniae-positive compared with C. pneumoniae-negative patients. The results are compatible with active infection and/or inflammation, possibly initiated by C. pneumoniae.

Role of Chlamydia pneumoniae in atherosclerosis

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

Chronic Inflammation, Immune Response, and Infection in Abdominal Aortic Aneurysms

Abdominal aortic aneurysms (AAA) are associated with atherosclerosis, transmural degenerative processes, neovascularization, decrease in content of vascular smooth muscle cells, and a chronic infiltration, mainly located in the outer aortic wall. The chronic infiltration consists mainly of macrophages, lymphocytes, and plasma cells. The dominant cells are Th2 restricted CD3+ lymphocytes expressing interleukine 4, 5, 8, and 10, and tumor necrosis factor-alpha for regulation of the local immune response. They also produce interferon-gamma and CD40 ligand to stimulate surrounding cells to produce matrix metalloproteases and cysteine proteases for aortic matrix remodeling. The lymphocyte activation may be mediated by microorganisms as well as autoantigens generated from vascular structural proteins, perhaps through molecular mimicry. As in autoimmune diseases, the risk of AAA is increased by certain genotypes concerning human leucocyte antigen class II. These types are also associated with increased aneurysmal inflammation indicating a genetic susceptibility to aortic inflammation. Chlamydia pneumoniae is often detected in AAA but the validity of the methods can be questioned, and two small antibiotic trials have been disappointing. However, serum antibodies against C. pneumoniae have been associated with AAA growth and cross-react with AAA wall proteins. Thus, immune responses mediated by microorganisms and autoantigens may play a pivotal role in AAA pathogenesis.

Chlamydia pneumoniae infections augment atherosclerotic lesion formation: a role for serum amyloid P

Multiple reports have demonstrated an association between Chlamydia pneumoniae (Cpn) and cardiovascular disease. In this study we evaluated the effect of Cpn infections on early lesion progression in C57BL/6J mice. Since plaque formation in these mice does not develop past the initial stage, we thought these mice might be a better model for unravelling the effect of Cpn infection on early lesion type progression. C57BL/6J mice were fed an atherogenic diet and injected 10 times with 5 x 10(7) IFU Cpn or mock. At sacrifice, lesion number, size and type were analysed. To study the role of Cpn in inflammation, serum amyloid P (SAP) in plasma was determined as well as T-cells, macrophages and SAP in the lesions. In the aortic sinus of both groups, type 2 lesions were found. Cpn infection resulted in a 2.2-fold increase in total lesion size (Cpn: 10821+/-2429 microm(2)vs mock: 5022+/-1348 microm(2); p=0.04). No difference in lesion number was observed. Also, Cpn infection increased SAP in the lesions from 1.10(-4)+/-0.1.10(-4) SAP-positive cells/lesion area to 10.10(-4)+/-1.10(-4) SAP-positive cells/lesion area (p=0.05). The influx of T-lymphocytes and macrophages in the lesions as well as SAP plasma levels were not different between groups. Multiple Cpn infections resulted in a significant increase in total lesion size of C57BL/6J mice. Increase in total SAP-positive area in infected mice suggests a role for this acute-phase protein in lesion enlargement.

Inflammatory Abdominal Aortic Aneurysms

BACKGROUND

Inflammatory abdominal aortic aneurysms (IAAA) are a variant of aortic aneurysm characterised by extensive peri-aneurysmal fibrosis, thickened walls and dense adhesions and represent between 3 and 10% of all abdominal aortic aneurysms (AAA). Surgery is technically challenging and is still associated with an increased morbidity and mortality. Controversy exists about aetiology and pathogenesis.

METHODS

We review the literature on the current theories, the available imaging modalities and the current thinking on management of IAAA. A Medline database search was performed. Articles were cross-referenced.

RESULTS AND CONCLUSIONS

Aneurysm development is multifactorial with important genetic and environmental factors. The literature supports the theory that IAAA arise from the same antigenic stimulus that is responsible for the non-IAAA, representing one extreme of an inflammatory spectrum. The results after open repair have improved and there is now little difference in the mortality between non-IAAA and IAAA repair. However, there is likely to be a role for endovascular stenting in IAAA management and this requires further study. It is clear that closer follow-up of patients after IAAA repair with either technique is necessary to monitor the inflammatory process. No evidence-based follow-up protocol exists but three to six-monthly monitoring of renal function and erythrocyte sedimentation rate (ESR) for 24 months post-repair would seem a reasonable regime.

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.

[Relationship between the peripheral arterial occlusive disease and the infection by Chlamydophila pneumoniae]

BACKGROUND AND OBJECTIVE

The relationship between peripheral arterial occlusive disease (PAOD) and Chlamydophila pneumoniae infection was studied by analyzing clinical samples from 95 patients with PAOD (cases) and 100 controls.

PATIENTS AND METHOD

The following investigations were conducted: IgG and IgA against lipopolysaccharide (LPS) and against purified C. pneumoniae-specific antigens from elementary bodies (EB) with ELISA; anti-EB IgG, with MIF; C. pneumoniae DNA in arterial biopsy and peripheral blood leukocyte cells (PBLCs) with heminested PCR; LPS with ELISA; and bacteria culture in HEp-2 cells from arterial biopsy.

RESULTS

The percentage of positive results in cases and controls groups for anti-LPS IgG was: 21% and 14%, respectively, with no differences; nor were there any differences with IgA (22 and 21%, respectively). However, differences were seen in the anti-EB IgG between cases (74% and 72%, for ELISA and MIF, respectively) and controls (31% and 34%). There were no differences in anti-EB IgA. Bacterial DNA was detected in 67% of atheromatous plaques (cases) vs. 12% of pudendal arteries (controls) (p = 0.0001). No C. pneumoniae DNA and LPS was detected in PBLCs and biopsic samples, respectively; and no C. pneumoniae strain could be recovered by cell culture from cases.

CONCLUSIONS

On the basis of our results, PAOD is significantly associated with C. pneumoniae infection through the detection of anti-EB IgG from serum and bacterial DNA from arterial biopsy.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL RELEVANCE

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

The detection of Chlamydia pneumoniae in aneurysm of abdominal aorta and in normal aortic wall of organ donors

Sixty patients underwent surgery due to abdominal aortic aneurysms; the group included 30 patients with asymptomatic aneurysm and 30 with ruptured aneurysm. A control group comprised 30 organ donors. Surgical specimens derived from aneurysm or aorta fragments were investigated for Chlamydia pneumoniae DNA using PCR. In asymptomatic aneurysms, DNA was found in 9 cases (29%), and in ruptured aneurysms in 14 cases (49%). In the control group, C. pneumoniae DNA was not detected in an aortic wall. These results suggest that healthy aortic wall is not susceptible to chlamydial infection. A large number of aneurysm infections implies C. pneumoniae role in proteolysis and degradation of the aneurysm wall. The biological effect of this process may cause an enlargement of the aneurysm.

Does Lipoprotein(a) Inhibit Elastolysis in Abdominal Aortic Aneurysms?

PURPOSE

to test the hypothesis that there is a negative association between serum levels of lipoprotein(a) (Lp(a)) and elastin-derived peptides (EDP) as well as matrix metalloproteinase (MMP)-9 activation in the aneurysm wall in patients with asymptomatic abdominal aortic aneurysms (AAA).

MATERIAL AND METHODS

from 30 patients operated for asymptomatic AAAs, preoperative serum samples and AAA biopsies were collected. Lp(a) (mg/L) and EDP (ng/ml) in serum were measured by enzyme linked immunosorbent assays. MMP-9 activity (arbitrary units) in the AAA wall was measured by gelatin zymography and the ratio: active MMP-9/total MMP-9 were calculated.

RESULTS

there was a significant negative correlation (Spearman's rho) between serum levels of Lp(a) and EDP (r= -0.707, p<0.001), as well as the share of activated MMP-9 (r= -0.461, p=0.01) in the AAA wall.

CONCLUSION

this preliminary study indicate that Lp(a) inhibit elastolysis in asymptomatic AAA.

Evaluation of five DNA extraction methods for purification of DNA from atherosclerotic tissue and estimation of prevalence of Chlamydia pneumoniae in tissue from a Danish population undergoing vascular repair

BACKGROUND

To date PCR detection of Chlamydia pneumoniae DNA in atherosclerotic lesions from Danish patients has been unsuccessful. To establish whether non-detection was caused by a suboptimal DNA extraction method, we tested five different DNA extraction methods for purification of DNA from atherosclerotic tissue.

RESULTS

The five different DNA extraction methods were tested on homogenate of atherosclerotic tissue spiked with C. pneumoniae DNA or EB, on pure C. pneumoniae DNA samples and on whole C. pneumoniae EB. Recovery of DNA was measured with a C. pneumoniae-specific quantitative real-time PCR. A DNA extraction method based on DNA-binding to spin columns with a silica-gel membrane (DNeasy Tissue kit) showed the highest recovery rate for the tissue samples and pure DNA samples. However, an automated extraction method based on magnetic glass particles (MagNA Pure) performed best on intact EB and atherosclerotic tissue spiked with EB. The DNeasy Tissue kit and MagNA Pure methods and the highly sensitive real-time PCR were subsequently used on 78 atherosclerotic tissue samples from Danish patients undergoing vascular repair. None of the samples were positive for C. pneumoniae DNA. The atherosclerotic samples were tested for inhibition by spiking with two different, known amounts of C. pneumoniae DNA and no samples showed inhibition.

CONCLUSION

As a highly sensitive PCR method and an optimised DNA extraction method were used, non-detection in atherosclerotic tissue from the Danish population was probably not caused by use of inappropriate methods. However, more samples may need to be analysed per patient to be completely certain on this. Possible methodological and epidemiological reasons for non-detection of C. pneumoniae DNA in atherosclerotic tissue from the Danish population are discussed. Further testing of DNA extraction methods is needed as this study has shown considerable intra- and inter-method variation in DNA recovery.

Failure to detect Chlamydia pneumoniae DNA in cerebral aneurysmal sac tissue with two different polymerase chain reaction methods

OBJECTIVE

Chlamydia pneumoniae (C pneumoniae) is a common cause of a usually mild, community acquired pneumonia. This organism, however, can spread from the respiratory tract into other parts of the body and has been detected in up to 70% of atheromatous lesions in blood vessels. Although the exact mechanism of the C Pneumoniae contribution to the pathogenesis of atherosclerosis remains unknown, prophylactic antibiotic trials are planned for people at high risk for coronary disease.

METHOD

In this study the authors aimed to investigate C pneumoniae DNA content in the cerebral aneurysmal sac tissue with the aid of polymerase chain reaction (PCR) method. C pneumoniae DNA was searched in 15 surgically clipped and removed aneurysmal sac tissue and in two tumour (an ependymoma of the fourth ventricle and a craniofaringoma) samples by touchdown enzyme time release PCR (TETR PCR) targeting 16S rRNA gene and by nested PCR targeting ompA gene.

RESULTS

Both PCR methods were sensitive to detect in C pneumoniae 4x10(-2) genomes. C pneumoniae DNA was not detected in any of the 17 sample tissues of these patients.

CONCLUSION

The contribution of C pneumoniae in the development of intracranial aneurysms cannot be excluded despite the results of this study. Further studies on the possible role of C pneumoniae or any other micro-organisms in the pathogenesis of aneurysms should be performed.

Prevalence of Chlamydia pneumoniae in the atherosclerotic plaque of patients with unstable angina and its relation with serology

BACKGROUND

Chlamydia pneumoniae has been associated with coronary artery disease by both seroepidemiological studies, and by direct detection of the micro-organism in atherosclerotic lesions. This bacteria could play a potential role in the development of acute coronary events. We examined coronary arteries from patients with unstable angina in order to verify an endovascular presence of C. pneumoniae, and to determine if there is any relationship between serology of acute infection by this pathogen and its presence inside the atherosclerotic plaque of these patients.

METHODS

We analysed a total of 76 atherosclerotic plaques obtained from 45 patients who underwent coronary artery bypass surgery. In all patients unstable angina was present within the prior 3 weeks. The presence of C. pneumoniae in the plaque was determined by nested polymerase chain reaction (PCR). Antichlamydial immunoglobulin G (IgG), A (IgA) and M (IgM) was examined by microimmunofluorescence and compared to the PCR result.

FINDINGS

DNA of C. pneumoniae was detected in 57 (75%) of 76 atherosclerotic lesions. In most cases (74/76: 97%) a positive IgA, IgM or IgG result was seen. Seven (12%) and 54 (94%) of the 57 PCR positive plaques came from patients with a positive IgM and IgA result, respectively. There was no statistical significant difference between PCR positive and PCR negative plaques in patients with a positive or negative serological result. Clinical characteristics were similarly distributed in patients with and without infected lesions.

INTERPRETATION

C. pneumoniae organisms are frequently found in the atherosclerotic lesions of patients undergoing coronary surgery for unstable angina. Neither serological results of acute or recent infection by C. pneumoniae nor clinical characteristics are useful in predicting the individual risk of harbouring C. pneumoniae in the coronary lesions of patients with unstable angina.

Lack of association between serum immunoreactivity and Chlamydia pneumoniae detection in the human aortic wall

BACKGROUND

Only a few studies have focused the attention on the relation between elevated anti-Chlamydia pneumoniae (CP) antibodies and the detection of CP in the arterial wall. The aim of our study is thus to investigate the relationship between immune response to CP and detection of CP in the aortic walls of patients with abdominal aortic aneurysm.

METHODS AND RESULTS

A specimen of aortic wall was obtained from 102 consecutive patients who underwent abdominal aneurysm repair. The possible presence of CP was studied by polymerase chain reaction and confirmed by nonradioactive DNA hybridization. Antibody response to CP was studied (IgG, IgA titers). We found 33 patients (32.4%) with CP DNA+. No correlation between CP DNA detection and antibody titers was found (IgG P=0.52, IgA P=0.66). High correlation between IgG and IgA titer was observed (P<0.01). Endovascular presence of CP and antibody titers was not related to the age of the patient.

CONCLUSIONS

CP antibody titers are not associated with the presence of CP in the aortic wall of patients with abdominal aortic aneurysm.

Presence of Chlamydia pneumoniae in abdominal aortic aneurysms is not associated with increased activity of matrix metalloproteinases

OBJECTIVE

to test the hypothesis that the presence of Chlamydia pneumoniae (C. pneumoniae) in the wall of abdominal aortic aneurysms (AAA) is associated with increased activity of matrix metalloproteinase (MMP)-2 and/or MMP-9.

DESIGN

case-control study.

MATERIAL AND METHODS

in a series of 40 patients with AAA > or =5cm in maximal cross-sectional diameter, C. pneumoniae-DNA was identified in the aneurysm wall by nested PCR in 14 (35%) patients. Another 14 C. pneumoniae-DNA-negative AAA patients from the same series, matched for gender and aneurysm diameter, were used as controls. In each group there were 7 asymptomatic (aAAA) and 7 ruptured (rAAA) aneurysms. MMP-2 and -9 activity was estimated in AAA wall biopsies by gelatin zymography.

RESULTS

patients with a C. pneumoniae-DNA-positive aneurysm wall specimen showed an over-all lower activity of MMP-2 and MMP-9 (pro- and active enzyme) compared to the C. pneumoniae-DNA negative patients. However, there were no statistically significant differences in MMP activity between the two groups of patients with aAAA. Among patients with rAAA both pro-MMP-9 (p=0,026) and active-MMP-9 (p=0.007) were significantly lower in C. pneumoniae-DNA-positive patients compared to C. pneumoniae-DNA-negative patients, whereas there were no significant differences in pro-MMP-2 or active-MMP-2.

CONCLUSION

this preliminary study does not support the hypothesis that the presence of C. pneumoniae in the AAA wall is associated with increased activity of MMP-2 and MMP-9.

Proteolysis of the abdominal aortic aneurysm wall and the association with rupture

PURPOSE

to investigate proteolysis of the abdominal aortic aneurysm (AAA) wall and the association with rupture.

METHODS

levels of matrix metalloproteinases (MMP-2 and MMP-9) and tissue inhibitor of metalloproteinases (TIMP-1 and TIMP-2) were measured in the walls of medium-sized (5-7 cm in diameter) ruptured AAA (rAAA) (n =30) and large (> or = 7 cm in diameter) asymptomatic AAA (aAAA) (n=30).

RESULTS

MMP-2 levels (median, range) were significantly higher in the walls of large aAAA (165 ng/g AAA tissue, 50-840) than from medium-sized rAAA (110 ng/g AAA tissue, 47-547, p=0.007). MMP-9 levels were significantly higher in the walls of medium-sized rAAA (107 ng/g AAA tissue, 19-582) than from large aAAA (55 ng/g AAA tissue, 11-278, p=0.012). TIMP-1 and TIMP-2 levels were equivalent. There was a positive correlation between MMP-2 and the diameter of aAAA (r=0.54, p=0.002), but a negative correlation with MMP-9 (r= -0.44, p=0.017). No significant correlations were found between aAAA diameter and TIMP-1 or TIMP-2.

CONCLUSION

AAA rupture is associated with higher levels of MMP-9. There is no association with TIMP-1 or TIMP-2 levels. MMP-2 levels are positively, whereas MMP-9 levels are negatively, correlated with aAAA size. MMP-9 may play a role in the progression towards rupture, whereas MMP-2 may play a role in expansion.

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.

In vitro degradation of aortic elastin by Chlamydia pneumoniae

OBJECTIVES

to investigate whether Chlamydia pneumoniae (C. pneumoniae) may increase elastin degradation in the aortic wall.

MATERIALS AND METHODS

eighteen full thickness aortic wall samples from non-aneurysmal infrarenal abdominal aortas were collected from autopsies. Two adjacent and equally large pieces were cut out of each aortic sample. From each sample, one piece was incubated in a HEp-2 cell culture infected with C. pneumoniae and the other piece was incubated in an uninfected HEp-2 cell culture. The incubation time was one week at 35 degrees C. The concentration of elastin-derived peptides (EDP) (ng/ml) in the medium of each cell culture was measured in duplicate. For each paired sample, delta-EDP (EDP in HEp-2 cell culture infected with C. pneumoniae- EDP in uninfected HEp-2 cell culture) was calculated.

RESULT

there was a significantly increased degradation of aortic elastin, estimated by EDP concentrations in cell culture conditioned medium, when aortic wall samples were incubated in C. pneumoniae cultures compared with uninfected cultures (p=0.025, Wilcoxon signed ranks test).

CONCLUSION

these results indicate that there is a relationship between the presence of C. pneumoniae and increased elastin degradation in the aortic wall in vitro. This suggests C. pneumoniae in the aortic wall directly or indirectly leads to the degradation of aortic elastin.

Use of doxycycline to decrease the growth rate of abdominal aortic aneurysms: a randomized, double-blind, placebo-controlled pilot study

OBJECTIVE

Eradication of Chlamydia pneumoniae infection and inhibition of elastolytic matrix metalloproteinases with doxycycline have been suggested to reduce the growth rates of small abdominal aortic aneurysms (AAA). We designed a study to investigate the efficacy of doxycycline in reducing the expansion of small AAAs.

SUBJECTS AND METHODS

This was a prospective, double-blind, randomized, placebo-controlled study that was set in a university referral hospital. The study group consisted of 32 of 34 initially eligible patients who had an AAA diameter perpendicular to the aortic axis of 30 mm or more in size or a ratio of infrarenal to suprarenal aortic diameter of 1.2 or more and a diameter less than 55 mm. Patients were randomly assigned to receive either doxycycline (150 mg daily) or placebo during a 3-month period and underwent ultrasound surveillance during an 18-month period. Outcome measures included aneurysm expansion rates, the number of patients who had AAA rupture or repair, C pneumoniae antibody titers, and serum concentrations of C-reactive protein.

RESULTS

The aneurysm expansion rate in the doxycycline group was significantly lower than that in the placebo group during the 6- to 12-month (P = .01) and the 12- to 18-month periods (P =.01). Five patients (41%) in the placebo group and 1 patient (7%) in the doxycycline group had an overall expansion of the aneurysm of 5 mm or more during the 18-month follow-up. Among the placebo group patients, a higher expansion rate was observed in those with enhanced C pneumoniae immunoglobulin G antibody titers (> 128) than in those with lower titers (P = .03). Doxycycline treatment had no clear effect on antibody titers. However, at 6-month follow-up, C-reactive protein levels in the doxycycline group were significantly lower than the baseline levels (P = .01).

CONCLUSIONS

The results of this small pilot study suggest that doxycycline may favorably alter the outcome of patients with small AAA. However, because of the small size of this randomized study and of the potentially confounding effect of pretreatment risk factors, doxycycline-based treatment cannot be justified only on the ground of the current results. Because of the high prevalence of this disorder and its clinical, social, and economic relevance, a multicenter study should be performed to further investigate whether there is any place for medical treatment of small AAAs.

Randomized double-blind controlled trial of roxithromycin for prevention of abdominal aortic aneurysm expansion

BACKGROUND

Macrolide treatment has been reported to lower the risk of recurrent ischaemic heart disease. The influence of macrolides on the expansion rate of abdominal aortic aneurysms (AAAs) remains unknown. The aim was to investigate the effect of roxithromycin on the expansion rate of small AAAs.

METHODS

A total of 92 subjects with a small AAA were recruited from two populations. One population consisted of 6339 men aged 65-73 years who were offered a hospital-based mass screening programme for AAA. From this population 66 subjects were recruited. The remaining 26 men were recruited from among 49 subjects diagnosed at interval screening for an initial aortic diameter between 25 and 29 mm. Subjects were randomized to receive either oral roxithromycin 300 mg once daily for 28 days or matching placebo, and followed for a mean of 1.5 years.

RESULTS

During the first year the mean annual expansion rate of AAAs was reduced by 44 [corrected] per cent in the intervention group (1.56 mm per year), compared with 2.80 mm per year following placebo (P = 0.02). During the second year the difference was only 5 per cent [corrected]. Multiple linear regression analysis showed that roxithromycin treatment and initial AAA size were significantly related to AAA expansion when adjusted for smoking, diastolic blood pressure and immunoglobulin A level of 20 or more [corrected]. Logistic regression analysis confirmed a significant difference in expansion rates above 2 mm annually between the intervention and placebo groups: odds ratio = 0.09 (95 per cent confidence interval 0.01-0.83) [corrected].

CONCLUSION

In comparison to placebo, roxithromycin 300 mg daily for 4 weeks reduced the expansion rate of AAAs.

Activity of matrix metalloproteinase-2 and -9 in abdominal aortic aneurysms. Relation to size and rupture

OBJECTIVES

to investigate the activity of matrix metalloproteinase (MMP)-2 and -9 in asymptomatic abdominal aortic aneurysms (aAAAs) and ruptured abdominal aortic aneurysms (rAAAs).

DESIGN

cross-sectional study.

MATERIALS AND METHODS

MMP-2 and MMP-9 activity was estimated in biopsies from the anterior wall of 60 AAAs using gelatin zymography. There were 20 medium-sized (diameter 5<7 cm) aAAAs, 20 large (>57 cm) aAAAs and 20 rAAAs. MMP activity was quantified using a laser densitometer and expressed as arbitrary units (au).

RESULTS

mean (SEM) MMP-9 activity was significantly lower in large aAAAs (1190 au +/-247) than in rAAAs (2647 au +/-498, p<0.05). There was no difference in MMP-2 activity.

CONCLUSION

High MMP-9 activity in the AAA wall is associated with rupture.

Infections and atherosclerosis

More than a century ago, inflammation and infection were considered to have atherogenic effects. During last century, however, this hypothesis was completely abandoned, and the old idea that coronary heart disease (CHD) possibly has an infectious etiology has only re-emerged in recent years. Both viral and bacterial pathogens have been proposed to be associated with the inflammatory changes found in atherosclerosis. Herpes group viruses, especially cytomegalovirus (CMV) and herpes simplex virus type 1 (HSV1), have been associated with both atherosclerosis and restenosis. Helicobacter pylori and dental infections have also been linked to CHD, but the evidence is strongest for a respiratory tract bacterium, Chlamydia pneumoniae. The association was originally found in seroepidemiological studies, but the presence of organisms in atherosclerotic lesions, the first animal studies and preliminary successful intervention trials with antibiotics suggest that C. pneumoniae may have a pathogenetic role in the disease. The causal relationship has not yet been proven, but ongoing large intervention trials and research on pathogenetic mechanisms may lead to the use of antimicrobial agents in the treatment of CHD in the future.

Analytical sensitivity, reproducibility of results, and clinical performance of five PCR assays for detecting Chlamydia pneumoniae DNA in peripheral blood mononuclear cells

Chlamydia pneumoniae has been associated with atherosclerosis and coronary artery disease (CAD), and its DNA has been detected in atheromatous lesions of the aorta, carotid, and coronary arteries by a variety of PCR assays. The objective of this study was to compare the performances of five published PCR assays in the detection of C. pneumoniae in peripheral blood mononuclear cells (PBMCs) from patients with coronary artery disease. The assays included two conventional PCRs, one targeting a cloned PstI fragment and one targeting the 16S rRNA gene; two nested PCRs, one targeting the 16S rRNA gene and one targeting ompA; and a touchdown enzyme time release (TETR) PCR, targeting the 16S rRNA gene. All PCRs had similar analytical sensitivities and detected a minimum of 0.005 inclusion-forming units (IFU) of C. pneumoniae; the ompA nested PCR and the TETR PCR were slightly more sensitive and detected 0.001 IFU. Assay reproducibility was examined by testing 10 replicates of C. pneumoniae DNA by each assay. All five assays showed excellent reproducibility at high levels of DNA, with scores of 10 out of 10 for 0.01 IFU, but exhibited decreased reproducibility for smaller numbers of C. pneumoniae IFU for all tests. Pairwise comparison of test results indicated that there was a significant difference between tests (Cochran Q = 32.0, P<0.001), with the PstI fragment (P<0.001) and 16S rRNA (P = 0.002) assays having lower reproducibility than the nested ompA and TETR assays. To further analyze assay sensitivity, C. pneumoniae-infected U-937 mononuclear cells were added to whole blood, and extracted mononuclear-cell DNA was tested by each assay. All five assays showed similar sensitivities, detecting 15 infected cells; three assays detected 3 infected cells, while all assays were negative at the next dilution (1.5 infected cells). A striking difference in performance of the five assays was seen, however, when PBMCs from CAD patients were tested for C. pneumoniae DNA. The ompA nested PCR detected C. pneumoniae DNA in 11 of 148 (7.4%) specimens, the 16S rRNA nested PCR detected 2 positives among the 148 specimens (1.4%) (P<0.001), and the other 3 assays detected no positive specimens (P<0.001, compared with the ompA assay). These results indicate that analytical sensitivity alone does not predict the ability of an assay to detect C. pneumoniae in whole-blood-derived PBMCs. Before standardized assays can be used in wide-scale epidemiological studies, further characterization of these assays will be required to improve our understanding of their performance in the detection of C. pneumoniae in clinical material.

Detection of Chlamydia pneumoniae DNA and antigen in the circulating mononuclear cell fractions of humans and koalas

Chlamydia pneumoniae is a common respiratory pathogen of humans which, in addition to causing disease at the respiratory site, has recently been linked to disease at other body sites. If C. pneumoniae does contribute to disease at nonrespiratory sites, then it must have a mechanism by which it reaches these sites. We analyzed the peripheral blood mononuclear cell (PBMC) fractions from 60 healthy human blood donors for the presence of C. pneumoniae DNA (by ompA PCR) and chlamydial antigens (by genus- and species-specific monoclonal antibody staining). Ten of the sixty (16. 7%) blood donors were C. pneumoniae positive by PCR, and all 10 of these PCR-positive individuals' samples demonstrated specific staining with anti-C. pneumoniae monoclonal antibodies. The only other host naturally infected with C. pneumoniae is the koala, in which the bacterium also causes respiratory infections. We demonstrated the presence of C. pneumoniae DNA and antigens in the PBMC fractions of 30% of 20 koalas tested. Our finding of C. pneumoniae-infected PBMCs in koalas as well as humans suggests that the ability to infect PBMCs and to disseminate from the respiratory site is not restricted to the human biovar of C. pneumoniae but is a general characteristic of this chlamydial species.

Chlamydia pneumoniae and atherosclerosis

Chlamydia pneumoniae (C. pneumoniae) is a common respiratory pathogen. Many reports have documented the presence of C. pneumoniae in atheromatous coronary arteries, aorta, carotid arteries, and peripheral arteries using a variety of techniques. There is clear experimental evidence that C. pneumoniae can infect macrophages, endothelial cells, smooth muscle cells, and induce the formation of foam cells. Evidence from basic research and epidemiologic studies suggest that C. pneumoniae can induce macrophage foam cell formation by dysregulating native LDL uptake or metabolism (or both). Relatively small, secondary prevention studies, have suggested that antibiotic therapy might reduce monocyte activation and C. pneumoniae antibody titers, reduce inflammatory markers and possibly reduce adverse cardiovascular events. It is possible that C. pneumoniae enhances atherogenesis by causing inflammation and eliciting immune responses and may be one of the factors contributing to this multifactorial disease process.

Genitourinary chlamydial infection: a reappraisal and hypothesis

Our understanding of genitourinary chlamydial infection and disease remains limited. That natural defences and/or apparently adequate treatments leave some patients with latent disease is suspected. There is, however, no consensus as to its nature. Furthermore, many patients, most obviously males, presenting with similar or identical symptoms and signs remain unexplained in microbiological terms; this in spite of many years of dedicated research endeavour. The recent trend towards an impasse has coincided with a growing acquaintance with the immunobiology and immunopathology of chlamydial infections. The time would seem to have arrived for a reappraisal of available clinical and laboratory observations. A hypothesis with research suggestions is presented for discussion.

Chlamydia pneumoniae in abdominal aortic aneurysms: abundance of membrane components in the absence of heat shock protein 60 and DNA

In this article, we describe the results of a comparative study for the detection of Chlamydia pneumoniae in abdominal aortic aneurysm specimens of 19 patients through the use of immunocytochemistry (ICC), in situ hybridization (ISH), and polymerase chain reaction (PCR), along with the detection of cytomegalovirus (CMV) and herpes simplex virus (HSV) by ICC and PCR. C pneumoniae-specific membrane protein was detected in specimens of all 19 (100%; 95% confidence interval [CI] 82% to 100%) and of 15 (79%; 95% CI 54% to 94%) patients with monoclonal antibodies RR-402 and TT-401, respectively. Chlamydial lipopolysaccharide was detected in specimens of 15 (79%; 95% CI 54% to 94%) patients when the results of 4 different monoclonal antibodies were combined. Surprisingly, chlamydial heat shock protein 60 was not detected in any of the specimens by ICC. Furthermore, C pneumoniae DNA was not detected by ISH when a C pneumoniae major outer membrane protein gene fragment was used as probe, nor was it reproducibly detected by PCR on extracted DNA. These results may be explained either by different kinetics of degradation of the different components of C pneumoniae after infection of the vessel wall or by the involvement of other Chlamydia-like microorganisms. Coexistence of C pneumoniae antigens and HSV antigens but not CMV antigens was observed in specimens from 10 of 18 (56%; 95% CI 31% to 78%) patients by ICC. CMV and HSV DNAs were not detected by PCR. In conclusion, we have demonstrated the presence of antigens of C pneumoniae in the absence of specific DNA in abdominal aortic aneurysms, suggesting persistence of the antigens rather than a persistent infection.

Chlamydia pneumoniae and atherosclerosis

OBJECTIVE

To review the literature for evidence that chronic infection with Chlamydia pneumoniae is associated with atherosclerosis and acute coronary syndromes.

DATA SOURCES

MEDLINE and Institute of Science and Information bibliographic databases were searched at the end of September 1998. Indexing terms used were chlamydi*, heart, coronary, and atherosclerosis. Serological and pathological studies published as papers in any language since 1988 or abstracts since 1997 were selected.

DATA EXTRACTION

It was assumed that chronic C pneumoniae infection is characterised by the presence of both specific IgG and IgA, and serological studies were examined for associations that fulfilled these criteria. Pathological studies were also reviewed for evidence that the presence of C pneumoniae in diseased vessels is associated with the severity and extent of atherosclerosis.

DATA SYNTHESIS

The majority of serological studies have shown an association between C pneumoniae and atherosclerosis. However, the number of cases in studies that have reported a positive association when using strict criteria for chronic infection is similar to the number of cases in studies which found no association. Nevertheless, the organism is widely found in atherosclerotic vessels, although it may not be at all diseased sites and is not confined to the most severe lesions. Rabbit models and preliminary antibiotic trials suggest that the organism might exacerbate atherosclerosis.

CONCLUSION

More evidence is required before C pneumoniae can be accepted as playing a role in atherosclerosis. Although use of antibiotics in routine practice is not justified, large scale trials in progress will help to elucidate the role of C pneumoniae.