A single infection with Chlamydia pneumoniae is sufficient to exacerbate atherosclerosis in ApoE deficient mice.

Several studies have demonstrated a strong link between Chlamydia pneumoniae (Cp) infection and atherosclerosis progression/exacerbation. Here, we try to understand whether a single administration of Cp could exacerbate atherosclerosis. Apoe(-/-) mice were intranasally infected with Cp followed by a high fat diet. Mice were sacrificed at different time points after Cp infection to monitor the development of the atheroma. Cp infection increased lipid content in the aortic sinus of Apoe(-/-) mice starting from 8 weeks. This was associated with increased numbers of active myeloid dendritic cells and plasmacytoid DCs which were co-localized with T-cells in the atherosclerotic plaque. The serum levels of IFN-γ showed a Th1-like environment typical of atherosclerosis. In conclusion, we demonstrate that one dose of Cp could exacerbate atherosclerotic lesion development, triggering innate immune cell accumulation early on that allowed the involvement of Th1-like cells in the exacerbation of the atherosclerotic plaque at later time points.