Chlamydophila pneumoniae and human cytomegalovirus in atherosclerotic carotid plaques--combined presence and possible interactions.

The aim of our study was to investigate the combination of Chlamydophila pneumoniae and human cytomegalovirus (HCMV) as a pathogenic factor in atherosclerosis. Accordingly, we tested by means of PCR and immunohistochemistry the presence of these pathogens in the same atherosclerotic carotid specimen. The histology of the samples and the patients' antibodies against these pathogens were evaluated. Further, we examined the impact of C. pneumoniae and HCMV infection on the gene expression of the human monocytic cell line U937. Six of the 22 samples contained only C. pneumoniae, 4 contained only HCMV, 7 contained both C. pneumoniae DNA and/or antigens of both pathogens, and 5 samples were negative. No correlation was found between the presence of these microbes and either the cellular structure of the plaques, or the serostatus of the patients. The infection of U937 cells with HCMV and especially C. pneumoniae induced inflammation and atherosclerosis-related genes. Furthermore, the doubly-infected cells produced higher levels of the mRNA of pro-platelet basic protein and fatty acid binding protein 4. In conclusion, C. pneumoniae is often present in combination with HCMV in atherosclerotic carotid lesions. The in vitro coinfection model reveals that the doubly-infected monocytes are potent expressors of proatherosclerotic genes, suggesting that this coinfected population may accelerate the process of atherosclerosis.