Chlamydia pneumoniae infection in human monocytes
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Updated: Oct 24, 2026
Isolation, Transfection, and Culture of Primary Human Monocytes
Published on: December 16, 2019
S Airenne1, H M Surcel, H Alakärppä
1National Public Health Institute, Oulu, Helsinki, Finland.
Insights
Chlamydia pneumoniae infection in monocytes hinders infectious particle development but remains metabolically active. This persistence may contribute to inflammation and cardiovascular disease progression.
Area of Science:
- Microbiology
- Immunology
- Cardiovascular Research
Background:
- Chlamydia pneumoniae infection is linked to cardiovascular diseases, with monocytes playing a key role in atherosclerosis.
- The persistence of Chlamydia pneumoniae within mononuclear cells remains poorly understood.
Purpose of the Study:
- To investigate the morphology and biological characteristics of Chlamydia pneumoniae infection in human peripheral blood monocytes.
- To understand the factors contributing to the inhibition of infectious progeny development in monocytes.
Main Methods:
- Infection of human peripheral blood monocytes with Chlamydia pneumoniae.
- Confocal and transmission electron microscopy to analyze chlamydial morphology.
- Assessment of chlamydial mRNA expression and lymphocyte proliferative response in infected monocytes.
Main Results:
- Monocytes inhibited the development of infectious Chlamydia pneumoniae progeny, with abnormal inclusion and particle morphology observed.
- Tryptophan or anti-gamma interferon antibodies did not overcome this inhibition, suggesting other chlamydiostatic factors.
- Chlamydial mRNA expression persisted for at least 3 days, and infected monocytes induced lymphocyte proliferation for up to 7 days, indicating metabolic activity.
Conclusions:
- Chlamydia pneumoniae persists metabolically within monocytes despite inhibited progeny development.
- Infected monocytes may contribute to local immune responses and inflammation, potentially exacerbating atherosclerosis.
- Further research is needed to elucidate the mechanisms of chlamydial persistence and its role in cardiovascular pathology.
Abstract:
Chlamydia pneumoniae infection 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 of C. pneumoniae in mononuclear cells is poorly understood. To study the morphology and biological characteristics of the infection, human peripheral blood monocytes were infected with C. 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 of C. 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 that C. pneumoniae remains metabolically active in the monocytes in vitro. These results are in accordance with the hypothesis that C. pneumoniae may participate in the maintenance of local immunological response and inflammation via infected monocytes and thus enhance atherosclerosis.
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