title: IFN-gamma induced persistent Chlamydia pneumoniae infection in HL and Mono Mac 6 cells: characterization by real-time quantitative PCR and culture.
abstract: Growth of Chlamydia pneumoniae during gamma interferon (IFN-gamma) induced persistent infection in epithelial (HL) and monocyte-macrophage (Mono Mac 6) cell lines was studied by a quantitative real-time PCR and passage. When HL cultures were treated with IFN-gamma (25 U/ml), the replication of C. pneumoniae DNA was unaffected while differentiation into infectious elementary bodies (EB) was strongly inhibited, and in contrast to the untreated cultures, no second cycle of infection was observed. The estimated doubling time of C. pneumoniae genomes was 6-7 h in both IFN-gamma treated and untreated HL cultures. At 72 h post inoculation, most infectious EBs were released from untreated cultures, whereas in IFN-gamma treated HL cells >90% of C. pneumoniae genomes were in non-infectious form. A higher dose (1000 U/ml) of IFN-gamma was needed to restrict growth of C. pneumoniae in Mono Mac 6 cells. In untreated Mono Mac 6 cultures, the growth curve of C. pneumoniae resembled that observed in HL cells, except that no second cycle of infection could be detected. In IFN-gamma treated Mono Mac 6 cultures, the number of infectious C. pneumoniae EBs recovered decreased gradually after 3 days post inoculation, while C. pneumoniae genome load remained unaltered suggesting persistence of C. pneumoniae also in these cells.
authors.affiliation: Department of Virology, Haartman Institute, University of Helsinki, P.O. Box 21, 00014, Helsinki, Finland. laura.mannonen@helsinki.fi
authors.forename: Laura
authors.initials: L
authors.lastname: Mannonen
authors.forename: Eveline
authors.initials: E
authors.lastname: Kamping
authors.forename: Tuula
authors.initials: T
authors.lastname: Penttilä
authors.forename: Mirja
authors.initials: M
authors.lastname: Puolakkainen
mesh_terms: D000465:Algorithms; D001483:Base Sequence; D002460:Cell Line; D023521:Chlamydophila Infections / Q000209:etiology* / Q000382:microbiology; D016993:Chlamydophila pneumoniae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D004261:DNA Replication; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D004847:Epithelial Cells / Q000382:microbiology; D016680:Genome, Bacterial; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008264:Macrophages / Q000382:microbiology; D008854:Microscopy, Electron; D008954:Models, Biological; D009000:Monocytes / Q000382:microbiology; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins
chemical_list: D004269:DNA, Bacterial; D011994:Recombinant Proteins; D007371:Interferon-gamma