Toxoplasma on the Brain: Understanding Host-Pathogen Interactions in Chronic CNS Infection

Table 1

The response of CNS-resident cells to Toxoplasma gondii infection.

Brain cell type	Parasite stage	Activity	Reference
Neuron	Tachyzoite	Parasites can encyst in neurons	[75]
Neuron	Tachyzoite	Infection induces cytokine and chemokine production; stimulated neurons are unable to inhibit parasite growth	[121]
Neuron	Bradyzoite	Neurons containing parasite cysts avoid scrutiny by CD8^+ T cells	[89]
Neuron, microglia	Tachyzoite	Murine Nramp1^−/− models are affected in stress response and mortality following Toxoplasma gondii infection	[122]
Microglia	Tachyzoite, bradyzoite	Microglial cells are preferentially infected, but most effectively inhibit parasitic growth within CNS cells	[25]
Microglia	Tachyzoite	Upon Toxoplasma infection, microglia produce IL-1 beta, IL-10, and tumor necrosis factor-alpha	[123]
Microglia, endothelium	Tachyzoite	Murine model infection induce an upregulation of CD200R & CD200, which control CNS inflammation	[124]
Microglia, astrocyte	Tachyzoite	Infection downregulates MHC class II expression	[125]
Microglia	Tachyzoite	Toxoplasmic encephalitis induces IL-12p40, iNOS, IL-1beta, TNF-alpha largely due to CD8^+ T cell interaction. MHC classes I and II, ICAM-1, and leukocyte function-associated antigen-1 are also upregulated	[126]
Endothelium	Tachyzoite	Toxoplasmic encephalitis induces vascular cell adhesion molecule, ICAM-1, and MHC classes I and II. Induction depends on IFN-gamma receptor	[127]
Endothelium	Tachyzoite	Infection induces ICAM-1, IL-6, and MCP-1; Induction levels vary depending on parasite strain	[26]
Astrocyte, neuron	Tachyzoite	Astrocytes are preferentially infected compared to neurons	[75]
Astrocyte, microglia	Tachyzoite	Intracellular infection reduces expressed MHC II	[125]
Astrocyte	Tachyzoite	Interferon-gamma-activated indoleamine 2,3-dioxygenase (IDO) induction inhibits parasite growth	[128]
Astrocyte	Tachyzoite	IFN- gamma induced parasite growth inhibition is independent on reactive oxygen intermediates	[129]
Astrocyte	Tachyzoite, bradyzoite	Tissue Inhibitor of Metalloproteinases-1 (TIMP-1) is induced by infection	[85]
Astrocyte	Tachyzoite	Autophagy may be involved in the elimination of the degraded parasite material from the astrocyte host cell cytoplasm	[79]
Astrocyte	Tachyzoite	IGTP is required for IFN-gamma-induced inhibition of parasite growth	[130]