Abstract
BackgroundThe requirements for growth and survival of the intracellular pathogen Trypanosoma cruzi within mammalian host cells are poorly understood. Transcriptional profiling of the host cell response to infection serves as a rapid read-out for perturbation of host physiology that, in part, reflects adaptation to the infective process. Using Affymetrix oligonucleotide array analysis we identified common and disparate host cell responses triggered by T. cruzi infection of phenotypically diverse human cell types.ResultsWe report significant changes in transcript abundance in T. cruzi-infected fibroblasts, endothelial cells and smooth muscle cells (2852, 2155 and 531 genes respectively; fold-change ≥ 2, p-value < 0.01) 24 hours post-invasion. A prominent type I interferon response was observed in each cell type, reflecting a secondary response to secreted cytokine in infected cultures. To identify a core cytokine-independent response in T. cruzi-infected fibroblasts and endothelial cells transwell plates were used to distinguish cytokine-dependent and -independent gene expression profiles. This approach revealed the induction of metabolic and signaling pathways involved in cell proliferation, amino acid catabolism and response to wounding as common themes in T. cruzi-infected cells. In addition, the downregulation of genes involved in mitotic cell cycle and cell division predicted that T. cruzi infection may impede host cell cycle progression. The observation of impaired cytokinesis in T. cruzi-infected cells, following nuclear replication, confirmed this prediction.ConclusionMetabolic pathways and cellular processes were identified as significantly altered at the transcriptional level in response to T. cruzi infection in a cytokine-independent manner. Several of these alterations are supported by previous studies of T. cruzi metabolic requirements or effects on the host. However, our methods also revealed a T. cruzi-dependent block in the host cell cycle, at the level of cytokinesis, previously unrecognized for this pathogen-host cell interaction.
Highlights
The requirements for growth and survival of the intracellular pathogen Trypanosoma cruzi within mammalian host cells are poorly understood
T. cruzi elicits a robust cytokine-dependent response in diverse cell types To reveal a signature response elicited by Trypanosoma cruzi in phenotypically diverse non-phagocytic mammalian cell types, RNA was prepared from mock- and parasite-infected human vascular smooth muscle cells (VSMC), human microvascular endothelial cells (HMVEC) and human foreskin fibroblasts (HFF) at 24 hours post-infection and prepared for hybridization to HG_U133 plus 2.0 Affymetrix arrays for analysis of over 47,000 transcripts
VSMC were found to be less responsive to T. cruzi infection than HFF or Human cardiac microvascular endothelial cells (HMVEC) where the average number of gene expression changes observed in two independent experiments was as follows: VSMC: 531 genes (408 up, 131 down); HFF: 2852 genes (1204 up, 1648 down) and HMVEC 2155 genes
Summary
The requirements for growth and survival of the intracellular pathogen Trypanosoma cruzi within mammalian host cells are poorly understood. Transcriptional response data provide valuable insights into pathogen-triggered host defense pathways and changes in expression of host cell metabolic genes during infection, the transcriptional outcomes of such events are often obscured by compounded responses to diffusible molecules released by infected or neighboring cells. We have carried out a comparative analysis of host cell transcriptional response to the intracellular protozoan parasite, Trypanosoma cruzi, in three phenotypically diverse mammalian cell types with a view to uncovering a common signature response to parasite infection. We coupled this approach with the use of a transwell plating system to permit the identification of cytokine-dependent and independent responses to this pathogen
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