Chlamydia pneumoniaeInfection in Human Monocytes

Abstract

ABSTRACTChlamydia pneumoniaeinfection has been associated with cardiovascular diseases in seroepidemiological studies and by demonstration of the pathogen in atherosclerotic lesions. It has the capacity to infect several cell types, including monocyte-derived macrophages, which play an essential role in the development of atherosclerosis. However, the persistence ofC. pneumoniaein mononuclear cells is poorly understood. To study the morphology and biological characteristics of the infection, human peripheral blood monocytes were infected withC. pneumoniae. Freshly isolated monocytes resisted the development of infectious progeny, and confocal and transmission electron microscopy showed that the morphology of the inclusions and chlamydial particles was abnormal. Addition of tryptophan or antibodies against gamma interferon did not diminish the inhibition ofC. pneumoniae, suggesting that other factors are involved in the chlamydiostatic activity of the monocytes. Chlamydial mRNA was expressed at least 3 days after infection, however, and a capability for infected monocytes to induce a positive lymphocyte proliferative response was detected for up to 7 days, indicating thatC. pneumoniaeremains metabolically active in the monocytes in vitro. These results are in accordance with the hypothesis thatC. pneumoniaemay participate in the maintenance of local immunological response and inflammation via infected monocytes and thus enhance atherosclerosis.