Tobacco smoke induces a persistent, but recoverable state in Chlamydia pneumoniae infection of human endothelial cells

We investigated the extent to which tobacco smoke could induce persistence of Chlamydia pneumoniae in human endothelial cells. Aortic and coronary artery endothelia were infected in the absence or presence of non-cytotoxic concentrations of tobacco smoke medium. Following exposure to smoke medium, chlamydial inclusions were smaller and demonstrated fewer genome copies as determined by real-time PCR. Enumeration of inclusion-forming units (IFU) established a significant smoke-mediated, dose-dependent inhibition of elementary bodies (EB). Host cell apoptosis did not contribute to the observed restriction of productive infection. Ultrastructure analysis demonstrated an arrest in chlamydial development following smoke-exposure, with a predominance of reticulate bodies (RB) observed inside inclusions. Recovery of viable IFU was achieved with removal of smoke-medium and addition of L-tryptophan. In the presence of smoke, C. pneumoniae infection demonstrated all the characteristics of persistence in human endothelia cells. This is the first time that primary human arterial endothelial cells have been shown to support chlamydial persistence. Tobacco smoke is a well-characterized risk factor for progression of atherosclerosis, but a novel means of inducing chlamydial persistence in vascular cells. Thus, smoking may additionally contribute to atherosclerotic disease by inducing a persistent chlamydial infection in arterial endothelium.