Selection of mutant cell lines resistant to infection by Chlamydia spp [corrected]

Abstract

The lytic outcome of natural infection by Chlamydia trachomatis was exploited to select CHO (Chinese hamster ovary) cells, following chemical mutagenesis, that were deficient in their ability to sustain productive chlamydial infection. Four distinct mutant cell phenotypes with defects in either attachment or postattachment mechanisms that are required for infection by C. trachomatis and Chlamydia pneumoniae were characterized.

FIG. 1.

Parallel assessments of infectivity of C. trachomatis serovar L2 (CT-L2), serovar D (CT-D), and C. pneumoniae (CPn) for each CHO cell mutant. The infectivity of each chlamydial strain for monolayers of each cell line was tested in triplicate. Approximately 48 h postinfection, chlamydial inclusions were detected by immunofluorescence and enumerated by counting inclusions. Similar data were obtained in at least three independent experiments. Qualitative estimates of attachment are indicated as follows: no binding (NB) or cellular-associated binding on a progressive numerical scale of 1+ to 4+, where 1+ represents approximately 10 EBs apparently associated with cell surfaces and 4+ represents many EBs bound with entire staining of the cells.

FIG. 2.

Immunofluorescence staining of C. trachomatis (L2) EBs attached to cells from the cell lines CHO-K1 and CHO-6. EBs were added to monolayers, incubated for 1 h at 4°C, fixed with methanol, and stained with a C. trachomatis-specific monoclonal antibody conjugated with fluorescein isothiocyanate.