Characterization of Chlamydia pneumoniae Persistence in HEp-2 Cells Treated with Gamma Interferon

Infection with Chlamydia pneumoniae has been implicated as a potential risk factor for atherosclerosis. This study demonstrated the effects of gamma interferon (IFN-γ)-mediated indoleamine 2,3-dioxygenase activity on C. pneumoniae persistence in HEp-2 cells, inclusion morphology, and ultrastructure. C. pneumoniae replication showed a dose-dependent decrease when treated with increasing concentrations of IFN-γ and a phenotypic switch resulting in a decrease in typical inclusions with an increase in smaller, less-dense atypical inclusions. Ultrastructural analysis of IFN-γ-treated C. pneumoniae revealed atypical inclusions containing large reticulatate-like aberrant bodies with no evidence of redifferentiation into elementary bodies.