Demonstration of Chlamydia pneumoniae in the walls of abdominal aortic aneurysms

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.

Systemic inflammatory parameters in patients with atherosclerosis of the coronary and peripheral arteries

Plasma concentration of markers of inflammation are increased in patients with atherosclerosis. However, it is unclear whether the pattern and magnitude of this increase vary with the site and extent of disease. In 147 patients undergoing semiquantitative coronary angiography, we measured the acute-phase reactants C-reactive protein (CRP) or serum amyloid A (SAA); the proinflammatory cytokine interleukin 6 (IL-6); the active and total fractions of the anti-inflammatory cytokine transforming growth factor-beta (TGF-beta); the macrophage activation marker neopterin; and the infection marker procalcitonin. Compared with 62 patients without either coronary artery disease (CAD) or peripheral artery disease (PAD), 57 patients with CAD but no PAD showed greater median CRP (0. 4 versus 0.2 mg/dL, P=0.004) and IL-6 (3.8 versus 1.6 pg/mL, P=0. 007) levels and a lower level of active-TGF-beta (57 versus 100 ng/mL, P=0.038). Moreover, CRP, IL-6, and neopterin levels showed a positive and the active TGF-beta level a negative correlation with the extent of coronary atherosclerosis. Compared with these 57 patients with CAD alone, 15 patients with PAD and CAD had higher median levels of SAA (17 versus 7 mg/mL, P=0.008), IL-6 (12 versus 4 pg/mL, P=0.002), neopterin (14 versus 11 mg/dL, P=0.006), and total TGF-beta (11834 versus 6417 ng/L, P=0.001). However, these strong univariate associations of markers of inflammation and atherosclerosis were lost in multivariate analysis once age, sex, and high density lipoprotein cholesterol or fibrinogen were taken into account. Increased plasma levels of CRP, SAA, IL-6, TGF-beta, neopterin, and procalcitonin constitute an inflammatory signature of advanced atherosclerosis and are correlated with the extent of disease but do not provide discriminatory diagnostic power over and above established risk factors.

Long term vascular complications of Coxiella burnetii infection in Switzerland: cohort study

OBJECTIVE

To evaluate the range of long term vascular manifestations of Coxiella burnetii infection.

DESIGN

Cohort study in Switzerland of people affected in 1983 by the largest reported outbreak of Q fever and who were followed up 12 years later. Follow up information about possible vascular disease and endocarditis was obtained through a mailed questionnaire and death certificates.

SETTING

Val de Bagnes, a rural Alpine valley in Switzerland.

PARTICIPANTS

2044 (87%) of 2355 people who had serum testing for Coxiella burnetii infection in 1983: 1247 were classed as not having been infected, 411 were classed as having been acutely infected, and 386 were classed as having been infected before 1983.

MAIN OUTCOME MEASURES

Relative risk controlled for age and sex and 12 year risk of vascular diseases and endocarditis among infected participants as compared with those who had never been infected.

RESULTS

The 12 year risk of endocarditis or venous thromboembolic disease was not increased among those who had been acutely infected. The 12 year risk of arterial disease was significantly higher among those who had been acutely infected (7%) as compared with those who had never been infected (4%) (relative risk 2.2, 95% confidence interval 1.4 to 3.6). Specifically, there was an increased risk of developing a cerebrovascular accident (relative risk 3.7, 1.6 to 8.4) and cardiac ischaemia (relative risk 1.9, 1.04 to 3.4). 12 year mortality was significantly higher among the 411 people who had been acutely infected in 1983 (9.7%; age adjusted relative risk 1.8, 1.2 to 2.6) when compared with the 1247 participants who had remained serologically negative in 1983 (7.0%).

CONCLUSIONS

Coxiella burnetii infection may cause long term complications including vascular disease.

The influence of indomethacin on the metabolism and cytokine secretion of human aneurysmal aorta

INTRODUCTION

inflammation and proteolysis are important processes in the development of abdominal aortic aneurysms (AAAs). Prostaglandin E2 (PGE2) (a product of cyclo-oxygenase 2), other inflammatory mediators and proteolytic enzymes are produced in high quantities in the aneurysm wall. We developed an explant culture system for AAA tissue to assess the effects of potential drug therapies.

METHODS

full thickness biopsies of human AAA were established in culture in the presence or absence of indomethacin (a cyclo-oxygenase-2 inhibitor). The conditioned medium was collected at 48 h intervals and analysed for products of collagen breakdown, matrix metalloproteinases, PGE2 and inflammatory cytokines. Explant viability was assessed by histology, glucose consumption, lactate dehydrogenase release and demonstration of protein synthesis in the tissue.

RESULTS

nuclear morphology was maintained for 4 or more days and this, together with biochemical assays, indicated that AAA explants were viable in short-term culture. Indomethacin (10 microM) markedly reduced AAA explant production of prostaglandin E2 from 320 ng/ml to 3.3 ng/ml (p=0.028, n=6). Indomethacin also reduced the release of interleukin-1beta (IL-1beta) (from 166 pg/ml to 9.8 pg/ml, p =0.04, n=5) and interleukin-6 (IL-6) (from 119 ng/ml to 57 ng/ml, p=0.028, n=6), but had no effect on monocyte chemotactic protein 1 or matrix metalloproteinase-9 secretion.

CONCLUSIONS

short-term explants of AAA are a novel method to assess the effects of drugs on aneurysm tissue. Indomethacin reduces the production of PGE2, IL-1beta and IL-6, suggesting that cyclo-oxygenase-2 inhibitors may control the inflammation in the aneurysm wall and potentially limit AAA growth.

Chlamydia pneumoniae reactive T lymphocytes in the walls of abdominal aortic aneurysms

BACKGROUND

The presence of Chlamydia pneumoniae in the walls of abdominal aortic aneurysms (AAAs) has been demonstrated recently, but its role in the cause and/or maintenance of aortic wall inflammation is not known. In the present study, we have investigated the possible relationship between C. pneumoniae and the antigen specificity of T lymphocytes mediating inflammation in AAA tissue.

MATERIALS AND METHODS

Tissue specimens were obtained from 22 consecutive AAA patients undergoing elective surgery (mean age 67 +/- 1 year). Immunohistochemical analysis of the formalin-fixed tissue was performed using the streptavidin-biotin-peroxidase method. In vivo activated T lymphocytes were propagated from the specimens with interleukin (IL) 2, and antigen specificity of the established T-cell lines was analysed in the presence of autologous antigen-presenting cells using radioactive thymidine labelling.

RESULTS

Immunohistological staining of AAA tissue showed the presence of C. pneumoniae antigen in 55% (6/11) of the samples studied. The inflammatory cell infiltrate of the AAA tissue contained 60-90% T (CD45RO) and 0-10% B (CD20) cells. When the tissue specimens were cultured without antigen in the presence of IL-2, lymphocyte propagation was achieved in 17 out of the 22 samples. Chlamydia pneumoniae antigen was found to induce a positive proliferative response in 8 of the 17 lines.

CONCLUSIONS

The presence of C. pneumoniae specific T lymphocytes among in vivo activated cells from the AAA tissue specimens suggests that C. pneumoniae participates in the maintenance of the inflammatory response in the tissue and may thus be involved in the progression of the disease.

Uptake of tetracycline by aortic aneurysm wall and its effect on inflammation and proteolysis

BACKGROUND

Proteolytic degradation of the aortic wall by matrix metalloproteinases (MMPs) is considered important in the pathogenesis of abdominal aortic aneurysms (AAAs). Many of these MMPs are inhibited by tetracycline derivatives, which may have the potential to retard aneurysm growth.

METHODS

Patients undergoing elective repair of an AAA (n = 5) received an intravenous bolus of tetracycline (500 mg) on induction of anaesthesia and levels of tetracycline in serum, aneurysm wall and mural thrombus were assessed by microbiological assay. In a separate series of patients (n = 7) aneurysm biopsies were placed into explant culture (with and without tetracyline) and the accumulation of protein, hydroxyproline, MMP-9, interleukin (IL) 6 and monocyte chemoattractant protein (MCP) 1 in the medium was assessed by colorimetric assay or immunoassay.

RESULTS

At aortic cross-clamping the median concentration of tetracycline was 8.3 microg/ml in serum, 2.9 microg per g tissue in aortic wall and zero in mural thrombus. Tetracycline inhibited, in a concentration-dependent manner, both MMP-9 and MCP-1 secretion (P = 0.022 and P = 0.018 respectively), but did not alter hydroxyproline or IL-6 secretion. At the highest concentration of tetracycline (100 microg/ml) median MMP-9 secretion was reduced from 27 to 5 ng/ml (P = 0.007) and median MCP-1 secretion was reduced from 50 to 10 ng/ml (P = 0.008).

CONCLUSION

Tetracycline rapidly penetrates the aortic wall, but the concentration achieved may be insufficient to alter collagen turnover through limitation of MMP production or activity.

Chronic infection in the aetiology of atherosclerosis--focus on Chlamydia pneumoniae

An inflammatory basis to atherosclerosis is now accepted. It remains plausible (but unproven) that common infectious agents may contribute to the inflammatory signal, and hence the development (and/or progression of atherosclerosis and its clinical sequelae. Of the candidate microorganisms implicated, Chlamydia pneumoniae has emerged as the most likely pathogen to have a casual role. Evidence for this is based on sero-epidemiological, pathological and laboratory-based evidence, in addition to early animal models and small-scale antibiotic studies. A past decade of research has now culminated in prospective antibiotic intervention trials in coronary heart disease to be conducted. The results of these studies should help to finally determine whether infection with C. pneumoniae is a pathogenetic factor in atherosclerosis, and whether antibiotic therapy has a role in the secondary prevention of coronary heart disease.

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.

Cardiac infections: medical and surgical therapies

Infections of the heart can be acute or subacute, depending on host susceptibility, the cause and associated virulence, early diagnosis, and effective therapy. The following review will discuss the causes, clinical manifestations, diagnosis, and medical or surgical management of infective endocarditis, prosthetic valve endocarditis, myocarditis, and pericarditis. Nursing considerations emphasize understanding the pathogenesis, early recognition of signs and symptoms, and appropriate prevention and intervention.

The prevalence of Chlamydia pneumoniae in atherosclerotic and nonatherosclerotic blood vessels of patients attending for redo and first time coronary artery bypass graft surgery

OBJECTIVES

To determine if Chlamydia pneumoniae (C. pneumoniae) is more prevalent in atherosclerotic compared with normal blood vessels of patients requiring redo and first time coronary artery bypass graft surgery (CABG).

BACKGROUND

Serological and pathological studies have associated atherosclerosis with C. pneumoniae infection. As atherosclerosis is one of the causes of graft failure following CABG, then it may be expected that the prevalence of the organism in failed grafts and diseased native vessels should be greater than in the new grafts.

METHODS

Endarterectomy specimens and failed and new grafts were collected from 49 patients with late graft failure. Endarterectomy specimens and new grafts were also collected from nine patients having first time CABG. The presence of C. pneumoniae DNA was then checked for using a nested polymerase chain reaction.

RESULTS

The prevalence of C. pneumoniae DNA in failed venous grafts (38.2%) was similar to that in endarterectomy specimens from native coronary arteries (38.5%) and greater than that in new saphenous vein grafts (11.8%). However, it was similar to that in new internal mammary artery grafts (30.0%). Also, the interval between surgery in redo patients was the same regardless of whether C. pneumoniae was present or not.

CONCLUSIONS

Cross sectional studies cannot determine whether C. pneumoniae is a cause of atherosclerosis since they do not show whether infection precedes or follows its development. However, our results suggest that the organism is not an important factor in graft failure or atherosclerosis.

Is infection control an academic study?

This editorial aims to answer the question of whether infection control is an academic specialty. By considering the consequences of a lack of infection control in terms of patient morbidity and mortality and hence cost, it is easy to establish the importance of the area. Infection control embraces not only developing policies for preventing the physical spread of a micro-organism but also prophylactic therapy such as vaccination and therapeutic measures such as antibiotics. Infection control not only applies to localized infection in hospital due to antibiotic resistant microbes but also to the community. Bacteria such as Helicobacter pylori and Chlamydia pneumoniae and the viruses hepatitis B, hepatitis C, human lymphotropic virus type 1, Epstein-Barr viruses and human papilloma virus have been implicated in diseases not previously thought to have an infectious origin. Coping with these problems is clearly an academic area.

Association of Helicobacter pylori infection with elevated serum lipids

Helicobacter pylori causes a chronic gastric infection, which has been associated with coronary heart disease. To evaluate the mechanisms of this association, we studied whether the infection affects serum lipid levels as previously shown in acute infections. We analysed the serum samples of 880 males who participated in a reindeer herders' health survey in Northern Finland in 1989. H. pylori IgG and IgA antibodies were measured by enzyme-linked immunosorbent assay and triglyceride, total cholesterol and high-density lipoprotein cholesterol concentrations by routine enzymatic methods. A total of 52% of the subjects were positive for both H. pylori specific IgG and IgA and 31% were antibody-negative. The serum triglyceride and total cholesterol concentrations were significantly higher in the males with positive IgG and IgA antibody titres for H. pylori than in the males with no signs of infection (1.20 vs. 1.03 mmol/l, P < 0.001 and 6.59 vs. 6.11 mmol/l, P < 0.001, respectively). The associations remained statistically significant in non-smokers after the adjustment for age, body mass index (BMI) and social class. The finding supports the hypothesis that chronic infections may modify the serum lipid profile in a way that increases the risk of atherosclerosis.

Chlamydia pneumoniae in vascular tissue

This review summarizes the evidence for the presence of Chlamydia pneumoniae organisms in atherosclerotic lesions. A total of 17 publications are mentioned concerning this topic. In all but two, both from the same group, evidence is presented by means of various techniques for the existence of the organisms in atherosclerotic tissue. Thus, they have been found in the aorta and in coronary, carotid, pulmonary, femoral and iliac arteries. In the first study in the UK, the aorta, femoral and iliac arteries were found to be positive for C. pneumoniae. In a recent study on autopsy specimens undertaken in conjunction with South African investigators, 71% of atheromatous arteries were positive for C. pneumoniae compared with only 9% of non-atheromatous arteries. Interestingly, the organisms were detected in 67% of the vessels showing only early atherosclerotic lesions (fatty streaks). The relationship between the age of the subject and the probability of detecting C. pneumoniae organisms is discussed; the youngest subjects with arteries positive for these organisms were aged 15 and 20 years. It is concluded that the presence of chlamydiae within atherosclerotic lesions is now beyond doubt, but as yet there is no conclusive evidence for a causal role in atherosclerosis.

Endovascular presence of Chlamydia pneumoniae DNA is a generalized phenomenon in atherosclerotic vascular disease

The common respiratory pathogen Chlamydia pneumoniae has been implicated in the pathogenesis of coronary artery disease and acute myocardial infarction. In order to verify the endovascular presence of potentially viable chlamydia by detection of genomic DNA, we examined atherosclerotic arteries from various vascular regions using a C. pneumoniae specific nested polymerase chain reaction (PCR). The samples were obtained during surgical revascularization procedures or at autopsy. Chlamydial DNA was detected in 51/238 (21%) atherosclerotic samples. A total of 17 non-atherosclerotic control samples were PCR-negative. Chlamydial presence was detected in 36/140 (26%) vascular samples obtained at coronary revascularization procedures, in 9/61 (15%) samples from carotid artery stenosis, 3/17 (18%) samples from the aorta, and 3/20 (15%) iliac artery samples. Histomorphological discrimination of infected and non-infected arterial samples was not possible. Antichlamydial IgG and IgM response as examined by microimmunofluorescence assay did not aid identification of individual endovascular infection. C. pneumoniae is present in a significant proportion of atherosclerotic arteries. Its occurrence in atheromatous plaques is not limited to coronary arteries and may be considered indicative of an infectious component in atherosclerosis. However, it remains unclear whether chlamydia actually initiates atherosclerotic injury, facilitates its progression, or merely colonizes pre-existing atheromata.

Chlamydia pneumoniae and vascular disease

BACKGROUND

There is an increasing body of evidence linking the human pathogen Chlamydia pneumoniae with atherosclerosis.

METHODS

A Medline-based review of the literature was carried out.

RESULTS AND CONCLUSION

Seroepidemiological studies have revealed the possibility that evidence of infection with C. pneumoniae and atherosclerotic disease are related. Studies on human tissue have demonstrated that evidence of the organism can be found in human atherosclerotic tissue by both direct and indirect methods significantly more often than in control vascular tissue. Using animal models it is possible to show that C. pneumoniae can be disseminated haematogenously following pulmonary infection and that it shows a tropism for atherosclerotic tissue. In vitro work has demonstrated that the organism is capable of infecting, surviving and multiplying in cells of the human vascular wall, and that it can provoke a cell-mediated cytokine response which has implications both locally and systemically. Two clinical trials of macrolide antibiotics have demonstrated that they confer increased cardiovascular protection in patients following myocardial infarction. Adequately powered trials are needed to establish the therapeutic role of antibiotics in peripheral arterial disease.

Is there an infective aetiology to atherosclerosis?

Conventional cardiovascular risk factors fail to completely explain the observed variations in the prevalence and severity of coronary heart disease (CHD). Common chronic infections may have an aetiological role in the development of atherosclerosis and CHD, either independently or by interacting with traditional atherogenic risk factors. The evidence for Chlamydia pneumoniae as a potential causative agent is strongest, and is based on findings of numerous sero-epidemiological studies, examination of atheromatous plaque specimens, in vitro animal models and, recently, pilot antichlamydial antibiotic intervention trials. However, the complete natural history of C. pneumoniae, its mechanisms of damage in atherosclerotic disease, and the temporal sequence of infection and CHD remain unclear. Confirmation of true causality for the link between C. pneumoniae and CHD could come after the results of large-scale prospective antibiotic trials, which are to be conducted over the next few years. A proven association could have important implications for public health worldwide, potentially leading to novel and relatively inexpensive therapeutic measures in the secondary prevention of CHD--broad-spectrum antibiotics.

Demonstration of Chlamydia pneumoniae in patients with chronic pharyngitis

12 patients with longstanding throat symptoms, who were also positive by PCR (polymerase chain reaction) for Chlamydia pneumoniae were selected for a longitudinal study to determine whether C. pneumoniae is an aetiological agent for chronic pharyngitis. Specimens for culture and PCR detection of C. pneumoniae were taken from the retropharyngeal wall and blood specimens were taken for serology. Biopsies were taken from the mucosal membrane of the retropharyngeal wall for histological and immunohistochemical studies. C. pneumoniae was cultured from 4 cases. 10 patients had specific humoral antibodies to C. pneumoniae and 9 had high and increasing specific antibody titres to C. pneumoniae suggesting ongoing infection. The organism was demonstrated in the tissue from the retropharyngeal mucosal membrane by immunohistochemistry in 9 patients. The findings suggest that C. pneumoniae may be an aetiological agent for chronic pharyngitis.

Chlamydia pneumoniae-specific cell-mediated and humoral immunity in healthy people

In this work, cell-mediated immunity to Chlamydia pneumoniae was studied in 157 healthy individuals using lymphoproliferative assay and serum antibodies were analysed by microimmunofluorescence techniques. The C. pneumoniae-specific IgG antibodies were elevated more frequently and the geometric mean titres for IgG (67.5 versus 44.1; P = 0.05) and IgA (14.9 versus 11.3; P = 0.025) antibodies were significantly higher in males than in females. However, no gender-dependent differences were observed in cellular reactivity to C. pneumoniae, since the median cellular responses were similar (stimulation indices 7.5) in men and women. Although the cell-mediated and humoral responses to C. pneumoniae did not correlate clearly, elevated IgG antibodies were associated with slightly higher lymphocyte proliferation in comparison to all subjects (15.5 versus 7.5) and significantly stronger in comparison to those with persistently elevated IgA (> 80) antibodies (15.5 versus 3.5; P = 0.023). Further studies are needed to evaluate a possible role of reduced cellular reactivity in the cause of chronic C. pneumoniae infection.

Chlamydia pneumoniae and occlusive vascular disease: identification and characterization

Chlamydia pneumoniae, a respiratory pathogen, has been associated with occlusive vascular disease, including atherosclerosis and intimal hyperplasia, through seroepidemiologic studies. Furthermore, using immunohistochemistry (IHC), polymerase chain reaction (PCR), transmission electron microscopy (TEM), and in situ hybridization, this association has been reconfirmed by detecting this organism in atherosclerotic vascular tissue. This review summarizes and critically analyzes these findings and also discusses various mechanisms of how Chlamydia pneumoniae could be involved in the pathogenesis of occlusive vascular disease. Although more studies are needed to reproduce these results and, possibly, uncover a mechanism, the current literature fails to include detailed methodologies for studying Chlamydia pneumoniae. Therefore, to provide a general standard, we have also outlined specific protocols for IHC, PCR, and TEM. These protocols incorporate essential components from various studies and are presented in a concise and easily adaptable format.

Chlamydia pneumoniae in human abdominal aortic aneurysms

OBJECTIVES

To investigate the presence of Chlamydia pneumoniae DNA in the wall of infrarenal abdominal aortic aneurysms, and in the wall of non-aneurysmal infrarenal abdominal aortas.

DESIGN

Case-control study.

MATERIALS AND METHODS

The study group consisted of 40 patients operated transperitoneally for an infrarenal abdominal aortic aneurysm (IAAA) (eight females, 32 males; mean age 69 years, median age 68 years). Specimens from the aneurysm wall were taken peroperatively under sterile conditions. The control group consisted of 40 deceased persons without aortic aneurysms (14 females, 26 males; mean age 71 years, median age 70 years). Specimens from the non-aneurysmal infrarenal aortas (NIAA) were collected within 48 h after death. The specimens from both groups were frozen at -70 degrees C immediately after collection. A nested polymerase chain reaction (PCR) method, using two sets of primers designed to detect a fragment of the major outer membrane protein gene of C. pneumoniae, was used.

RESULTS

The detection of C. pneumoniae-specific DNA was significantly higher in the study group (14/40 = 35%) than in the control group (2/40 = 5%); (p = 0.001). No clinical factor predicting the presence of C. pneumoniae in the aneurysm wall, could be found.

CONCLUSION

Chlamydia pneumoniae was detected at a significantly higher frequency in the wall of IAAAs than in the wall of NIAAs. Although this finding does not prove that C. pneumoniae causes IAAAs, further studies on the possible role of C. pneumoniae in the pathogenesis of aneurysms should be performed.

Chlamydia pneumoniae and its role in chronic obstructive pulmonary disease

The diverging of T-helper (Th) cells into predominantly Th1 and Th2 subsets on the basis of their cytokine profiles has decisively improved our understanding of the pathogenesis of many chronic infectious diseases. Recent data suggest that the presence of interferon-gamma and the subsequent suppression of interleukin-4 production leads to a Th1-type response that is required for the resolution of infections caused by intracellular pathogens. The ability of the macrophages to respond aggressively during early antigen contact seems to be one crucial factor in the development of an appropriate Th-cell response. Several host-related factors can affect macrophage function and the polarization of T-cell responses, ie the shift from a Th1 response to a Th2 one, and thus dramatically deteriorate the resolution of infections caused by intracellular agents such as Chlamydia pneumoniae. Chronic C. pneumoniae infection has been associated with several common chronic diseases, quite recently with chronic obstructive pulmonary disease. Chronic C. pneumoniae infection may amplify smoking-associated inflammation in the bronchi and may be a contributory factor in the development of irreversible pathological changes.

Elevated circulating levels of inflammatory cytokines in patients with abdominal aortic aneurysm

The basic feature in the pathogenesis of abdominal aortic aneurysm (AAA) is the degradation of extracellular matrix components. This process is induced partly by cytokines secreted from inflammatory and mesenchymal cells. Circulating levels of inflammatory cytokines were studied in AAA patients and compared with subjects suffering from atherosclerotic disease only. Furthermore, the predictive value of cytokine concentrations was evaluated for aneurysm expansion rate. Circulating levels of interleukin 1 beta (IL-1 beta), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) were measured in 50 AAA patients (40 men, 10 women), 42 patients with coronary heart disease (CHD) (23 men, 19 women), and 38 controls whose angiogram was normal (17 men, 21 women). No differences in cytokine concentrations were found between the CHD patients and the controls. AAA disease was found to be associated with significantly higher IL-1 beta and IL-6 concentrations in both male patients (median concentrations of 19.40 pmol/L and 6.45 pmol/L, respectively) and female patients (19.26 pmol/L and 7.99 pmol/L) than in either the CHD patients or the controls (P < .005). TNF-alpha levels were slightly higher in the AAA patients (1.64 pmol/L in the males and 1.59 pmol/L in the females) than in the other groups (P < .05). IFN-gamma levels were elevated significantly in the female AAA patients (3.75 pmol/L) compared with levels found in the other female (P < .05) or male (P < .01) patient groups. The measured cytokine concentrations were not related to the size of the aneurysm or the maximal thickness of the thrombus within the aneurysm. IFN-gamma concentration showed a significant positive correlation to the aneurysm expansion (R = .37, P < .02) and negative correlation to the concentration of aminoterminal propeptide of type III procollagen during 6-month follow up (R = -.42, P < .005). The results show that circulating levels of inflammatory cytokines are elevated in patients with AAA disease, suggesting that the production of these cytokines is increased in these patients compared with CHD patients and controls. Elevated INF-gamma concentrations seem to predict an increased rate of expansion in AAA.