Toxoplasma gondii Dysregulates IFN-γ-Inducible Gene Expression in Human Fibroblasts: Insights from a Genome-Wide Transcriptional Profiling

Autor: John C. Boothroyd, Ashley E. Fouts, Seon-Kyeong Kim
Rok vydání: 2007
Předmět:
Zdroj: The Journal of Immunology. 178:5154-5165
ISSN: 1550-6606
0022-1767
DOI: 10.4049/jimmunol.178.8.5154
Popis: Toxoplasma gondii is an obligate intracellular parasite that persists for the life of a mammalian host. The parasite’s ability to block the potent IFN-γ response may be one of the key mechanisms that allow Toxoplasma to persist. Using a genome-wide microarray analysis, we show here a complete dysregulation of IFN-γ-inducible gene expression in human fibroblasts infected with Toxoplasma. Notably, 46 of the 127 IFN-γ-responsive genes were induced and 19 were suppressed in infected cells before they were exposed to IFN-γ, indicating that other stimuli produced during infection may also regulate these genes. Following IFN-γ treatment, none of the 127 IFN-γ-responsive genes could be significantly induced in infected cells. Immunofluorescence assays showed at single-cell levels that infected cells, regardless of which Toxoplasma strain was used, could not be activated by IFN-γ to up-regulate the expression of IFN regulatory factor 1, a transcription factor that is under the direct control of STAT1, whereas uninfected cells in the same culture expressed IFN regulatory factor 1 normally in response to IFN-γ. STAT1 trafficked to the nucleus normally and indistinguishably in all uninfected and infected cells treated with IFN-γ, indicating that the inhibitory effects of Toxoplasma infection likely occur via blocking STAT1 transcriptional activity in the nucleus. In contrast, a closely related apicomplexan, Neospora caninum, was unable to inhibit IFN-γ-induced gene expression. A differential ability to interfere with the IFN-γ response may, in part, account for the differences in the pathogenesis seen among Toxoplasma and Neospora parasite strains.
Databáze: OpenAIRE