Project description:In a forward genetic screen we identified a Chlamydia trachomatis L2/434/Bu mutant that causes rapid apoptotic and necrotic death of infected host cells. This phenotype could be linked to the loss of the inclusion membrane protein CpoS. We observed a reduction in cell death when infections were carried out in the presence of cycloheximide or actinomycin D, suggesting that the engagement of cell death depends on host transcription and protein synthesis. We applied RNA-Seq to study the transcriptional response of human endocervical epithelial (A2EN) cells to infection with wild-type or CpoS-deficient bacteria. At 6 hpi the transcriptional profiles of cells infected with the two strains were similar to each other and to the transcriptome of uninfected cells. However, by 18 hpi the transcriptional profile of cells infected with the mutant was strongly altered, with 400 host genes being upregulated greater than two-fold. Among those differentially expressed genes, we observed an enrichment of immunity-related genes, including in particular cytokine genes and interferon-stimulated genes. Overall these data demonstrate that the CpoS-deficient mutant induces an exacerbated interferon response.
Project description:C. trachomatis possess a cryptic 7.5 kb plasmid of unknown function. Here we describe a comprehensive molecular and biological characterization of the naturally occurring plasmidless human Chlamydia trachomatis strain L2 (25667R). We found that despite minimal chromosomal polymorphisms the LGV L2 (25667R) strain was indistinguishable from the L2 (434) plasmid positive strain in its in vitro infectivity characteristics such as growth kinetics, plaquing efficiency, and plaque size. The primary in vitro phenotypic differences between L2 (434) and L2 (25667R) were the accumulation of glycogen granules in the inclusion matrix and the lack of the typical intra-inclusion Brownian-like movement characteristic of C. trachomatis strains. Conversely, we observed a marked difference between the two strains in their ability to colonize and infect the female mouse genital tract. The ID50 of the L2 (25667R) plasmidless strain was 500 fold greater (1.XX x 10X IFU) than the L2 (434) plasmid bearing strain (1. XX x 10X IFU). Transcriptome analysis of the two strains clearly demonstrated a decrease in transcript levels of a subset of chromosomal genes for the L2 (25667R) strain. Among those genes was glgA which encodes for glycogen synthase; a finding consistent with the failure of the L2 (25667R) strain to accumulate glycogen granules. Collectively, these findings support an important role for the plasmid in in vivo infectivity and suggest that this virulence characteristic might be controlled by the plasmids ability to regulate the expression of specific chromosomal genes. These results also support an important role for the plasmid in the pathogenesis of human infection and disease. Keywords: strain comparison C. trachomatis strain L2-25667R compared to strain L2-434
