Chlamydia pneumoniae DNA in non-coronary atherosclerotic plaques and circulating leukocytes

Earlier studies have associated atherosclerosis with Chlamydia pneumoniae i nfection. C. pneumoniae may circulate via monocytes and migrate into plaque s by leukocyte infiltration; however, detection is difficult. We developed a novel polymerase chain reaction (PCR) method to test the hypothesis that C. pneumoniae DNA in circulating leukocytes is correlated with C. pneumonia e DNA in plaque material and that C. pneumoniae copy number is associated w ith disease severity. We obtained plaques from 130 patients who underwent s urgery for carotid stenosis, aneurysm, or peripheral vascular disease. From 60 patients and 51 normal control subjects we also obtained circulating le ukocytes. The C. pneumoniae 16 S rRNA gene was amplified with a highly spec ific quantitative PCR protocol relying on the TaqMan technology. Immunohist ochemistry was performed with antibody against the C. pneumoniae outer memb rane protein. C. pneumoniae DNA was present in 25% of atherosclerotic plaqu es and 20% of circulating leukocytes from patients. The copy number was not correlated with disease severity. C. pneumoniae DNA was more common in you nger patients and smokers. C. pneumoniae antibody titers, C-reactive protei n, fibrinogen, leukocyte count, cholesterol, and diabetes were not associat ed with C. pneumoniae DNA. Although immunostaining of plaque and PCR result s were highly correlated, we found no relationship between C. pneumoniae DN A in plaques and that in circulating leukocytes. Finally, 13% of normal con trol subjects had positive leukocytes; however, their copy number was signi ficantly lower than that of the patients. C. pneumoniae DNA is frequent in atherosclerotic plaques and is correlated with positive immunohistochemistr y. C. pneumoniae DNA may also be found in circulating leukocytes; however, infected leukocytes and plaques do not coincide. Serology is unreliable in predicting C. pneumoniae DNA. Smoking increases the risk of harboring C. pn eumoniae DNA. Our results do not suggest that either test for antibodies or C. pneumoniae DNA from leukocytes in blood is of value in predicting infec ted plaques.