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Microarray analysis reveals previously unknown changes in Toxoplasma gondii-infected human cells
I J Blader1, I D Manger, J C Boothroyd
1Department of Microbiology and Immunology, Stanford University, Stanford, California 94305-5124, USA.
Abstract:
Cells infected with the intracellular protozoan parasite Toxoplasma gondii undergo up-regulation of pro-inflammatory cytokines, organelle redistribution, and protection from apoptosis. To examine the molecular basis of these and other changes, gene expression profiles of human foreskin fibroblasts infected with Toxoplasma were studied using human cDNA microarrays consisting of approximately 22,000 known genes and uncharacterized expressed sequence tags. Early during infection (1-2 h), <1% of all genes show a significant change in the abundance of their transcripts. Of the 63 known genes in this group, 27 encode proteins associated with the immune response. These genes are also up-regulated by secreted, soluble factors from extracellular parasites indicating that the early response does not require parasite invasion. Later during infection, genes involved in numerous host cell processes, including glucose and mevalonate metabolism, are modulated. Many of these late genes are dependent on the direct presence of the parasite; i.e. secreted products from either the parasite or infected cells are insufficient to induce these changes. These results reveal several previously unknown effects on the host cell and lay the foundation for detailed analysis of their role in the host-pathogen interaction.
Insights
Toxoplasma gondii infection alters host cell gene expression, initially boosting immune responses via parasite secretions. Later, direct parasite presence modifies host cell processes like metabolism, revealing new host-pathogen interactions.
Area of Science:
- Cellular biology
- Parasitology
- Immunology
Background:
- Toxoplasma gondii infection induces pro-inflammatory cytokines, organelle redistribution, and apoptosis resistance in host cells.
- Understanding the molecular mechanisms behind these host cell alterations is crucial for studying host-pathogen interactions.
Purpose of the Study:
- To investigate the gene expression profiles of human foreskin fibroblasts infected with Toxoplasma gondii.
- To identify host genes modulated during early and late stages of infection.
- To differentiate between host responses induced by parasite invasion versus secreted factors.
Main Methods:
- Gene expression profiling using human cDNA microarrays (approx. 22,000 genes).
- Infection of human foreskin fibroblasts with Toxoplasma gondii.
- Analysis of gene transcript abundance at early (1-2 h) and later time points post-infection.
Main Results:
- Early infection (<1% of genes altered) showed up-regulation of immune response genes, triggered by parasite secretions alone.
- Later infection revealed modulation of host cell processes, including glucose and mevalonate metabolism.
- Late-stage gene modulation required direct parasite presence, not just secreted factors.
Conclusions:
- Toxoplasma gondii infection elicits distinct early and late host gene expression responses.
- Early immune gene activation is mediated by secreted parasite factors, independent of invasion.
- Later metabolic changes are dependent on the parasite's direct interaction with the host cell, highlighting novel host-pathogen interplay.