Quantification and location of Chlamydia pneumoniae-specific antigen in the walls of abdominal aortic aneurysms.

BACKGROUND: To evaluate the prevalence and quantity of Chlamydia pneumoniae-specific antigen in the three layers (intima, media, and adventitia) of abdominal aortic aneurysms (AAAs), so as to further investigate the pathogenesis of AAAs. METHODS: Aortic walls were collected from 20 patients with AAA and 11 healthy organ donors. Immunohistochemistry was used to identify the C pneumoniae-specific antigen, and image analysis system was used to quantify and locate it. RESULTS: The positive rate of C pneumoniae-specific antigen was higher in the AAA group than in the control group (100% vs. 54.54%, p = 0.003), positive intensity decreased from the tunica intima to the adventitia in the AAA group (16.32% ± 2.13%, 14.84% ± 1.80%, and 14.25% ± 1.67%, respectively, p = 0.003). In the control group, positive cells were mainly found in focal lesion areas. CONCLUSION: We have demonstrated the presence and differentiation of C pneumoniae-specific antigen in the three layers of AAAs, which are in accordance with pathology, thus suggesting a pathogenic role of the antigen.

Morphometrical quantification of Chlamydia pneumoniae and Mycoplasma pneumoniae in human atherosclerotic abdominal aortic aneurysms.

OBJECTIVE: Atherosclerotic inflammation with a possible role of infectious agents can contribute to the pathogenesis of abdominal aortic aneurysms (AAA). The finding of Chlamydia pneumoniae (CP) in these lesions in previous non-quantifying studies ranged from 0-100%. The objective is to quantify the presence of CP and Mycoplasma pneumoniae (MP) in AAA. METHODS: The thickness, and the number of cells positive for CP detected by the immunohistochemistry (immunoperoxidase, which is a type of immunohistochemical stain used in molecular biology, medical research, and clinical diagnostics), and the percentage of the area occupied by the Mycoplasma pneumoniae detected by in situ hybridization in three layers of the aorta were measured using an image-analysis system in 10 necropsies of abdominal aneurysmatic aortas. Three groups were used as controls: 1) samples of the same aortas, outside the aneurysms, except if the dilatation took the whole sub-renal portion of the artery (n=7); 2) aortas with severe atherosclerosis but without aneurysms (n=10); 3) aortas without or with mild atherosclerosis (n=10). All specimens were obtained at necropsies. Wald's test was used to compare groups; significance level was established at 5%. RESULTS: The tunica intima was thinner and the tunica media was thicker in the normal cases than in the other groups (p<0.01). Positive cells for CP were found in all groups, more frequently at the adventitia; no significant difference was detected between the groups (p>0.05). MP was also detected in all groups. This agent predominated in the group of patients with atherosclerosis, but without aneurysms at both tunica intima and adventitia; nevertheless, there were no significant differences between the groups (p>0.05). CONCLUSIONS: Our data suggested that the bacteria we focused to, does not play an important role in the pathogenesis of AAA.

Chlamydia pneumoniae in foci of "early" calcification of the tunica media in arteriosclerotic arteries: an incidental presence?

Only a few previous works investigated the involvement of Chlamydia pneumoniae (Chlamydophila pneumoniae) in arterial calcification. The present study investigated a possible association between C. pneumoniae and medial calcification. Carotid artery segments obtained by endarterectomy from 60 patients were examined by PCR and immunohistochemistry to identify the presence of C. pneumoniae. Arterial specimens showing double-positive (n = 17), double-negative (n = 22), and single-positive results (n = 21) were further analyzed by a combination of histology, immunohistochemistry, and electron microscopy. Medial calcification occurred in 10 of 17 (58.8%) C. pneumoniae double-positive arterial specimens, but no medial calcification was observed in any of 22 C. pneumoniae double-negative arterial specimens. Electron microscopy indicated C. pneumoniae in smooth muscle cells (SMCs) in foci of medial calcification. Medial SMCs showing damage to the cytoplasm and basement membrane contained the structures with the appearance of elementary, reticulate, and aberrant bodies of C. pneumoniae. The presence of C. pneumoniae in SMCs was confirmed by electron-microscopic immunocytochemistry. In the extracellular matrix, calcification was observed in C. pneumoniae aberrant bodies that exited the SMCs. The findings offer a new hypothesis of arterial calcification: they suggest that C. pneumoniae infection of medial SMCs may be associated with the pathophysiological events of arteriosclerotic calcification of the tunica media.

Early atherosclerosis and Chlamydia pneumoniae infection in the coronary arteries.

In non-atheromatous segments of coronary arteries a sequence of preatherosclerotic changes was identified which consisted of medial thickening followed by intimal thickening. More recently, Chlamydia pneumoniae seropositivity was associated with enhanced intima-media thickness of arteries. In the present study the intimal and medial thickness of coronary artery of young adults were measured, and were correlated with the presence of Chlamydia pneumoniae antigens. Proximal and distal segments of the left anterior descending coronaries (LAD) obtained at autopsy from young adults (15-34 years) were studied. The thickness and cellular density of the intima and of the media without clear-cut atherosclerotic changes were measured by image analysis. The hypertrophy index was calculated as the ratio of cell density and the thickness of the respective layer. Atherosclerotic lesions occurring elsewhere in the same coronary were noted and graded by severity. The presence of Chlamydia pneumoniae verified by immunohistochemistry was correlated with the severity of lesions and with the hypertrophy index. In the proximal segments, atherosclerosis of LAD was associated with the widening of both the intima and the media of lesion free-sites. In the distal coronary segments the proportion of the intimal thickening had a significant association with atherosclerosis. Compared to non-infected arteries, Chlamydia pneumoniae infection was associated with higher hypertrophy index in the intima as well as in the media. The rate of Chlamydia pneumoniae positivity increased with the severity of lesions. As a conclusion: in the LAD coronary, the intimal thickening is the main preatherosclerotic change. Chlamydia pneumoniae may favour arterial wall hypertrophy and plays a role in lesion progression.

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.

Distribution of Chlamydia pneumoniae in the human arterial system and its relation to the local amount of atherosclerosis within the individual.

BACKGROUND: Chlamydia pneumoniae has been suggested to play a role in the origin of atherosclerosis. We studied the prevalence of C pneumoniae at multiple locations in the arterial system within the same individual. Studying the association between atherosclerosis and C pneumoniae within the individual excludes confounding by interindividual variability. METHODS AND RESULTS: Postmortem, the presence in the intima/plaque and media of C pneumoniae membrane protein was determined by use of a C pneumoniae-specific monoclonal antibody. In 24 individuals, 33 arterial locations were studied (n=738 segments). Area stenosis was determined in adjacent cross sections. In all individuals, immunostaining of C pneumoniae was observed in >/=1 artery. The highest prevalences were observed in the abdominal aorta (67%), internal and common iliac arteries (41%), and coronary arteries (33%). The lowest prevalences were observed in the radial (0%) and cerebral (2%) arteries. Within the individual, area stenosis was larger in cross sections with immunoreactivity compared with cross sections without immunoreactivity (31.0+/-11.9% versus 14.3+/-6.1%, respectively; P:<0.001). In the individual, immunoreactivity was observed in 15+/-10% of the arteries (range, 3% to 45%). Between individuals, the percentage of arteries with immunoreactivity to C pneumoniae was associated with the average area stenosis throughout the arterial system (r(2)=0.56, P:<0.001). CONCLUSIONS: C pneumoniae was mostly observed at locations that are related to clinically relevant features. Within the individual, the distribution of C pneumoniae is associated with the distribution of atherosclerosis. The role of the microorganism in atherosclerotic disease remains to be elucidated.