Toxoplasma effector GRA15-dependent suppression of IFN-γ-induced antiparasitic response in human neurons

Hironori Bando, Youngae Lee, Naoya Sakaguchi, Ariel Pradipta, Ryoma Sakamoto, Shun Tanaka, Ji Su Ma, Miwa Sasai, Masahiro Yamamoto

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Toxoplasma gondii is an important human and animal pathogen that causes life-threatening toxoplasmosis. The host immune system produces interferon-γ (IFN-γ) to inhibit T. gondii proliferation. IFN-γ-inducible indole-2,3-dioxygenase 1 (IDO1), which mediates tryptophan degradation, has a major role in anti-T. gondii immune responses in various human cells. In response to the host's immune system, T. gondii secretes many virulence molecules into the host cells to suppress IFN-γ-dependent antiparasitic immune responses. The GRA15-induced proparasitic mechanism for suppressing IDO1-dependent immune responses has previously been tested only in human hepatocyte and monocyte co-cultures. Thus, whether human cells other than hepatocytes contain this virulence mechanism remains unclear. Here, we show that the GRA15-dependent virulence mechanism for suppressing the IDO1-dependent anti-T. gondii response operates in human neuronal cell lines and primary human neurons. Analysis of various human cell lines revealed that IL-1β-induced iNOS-dependent reduction of IDO1 mRNA expression occurred in brain cell lines (A172; glioblastoma, IMR-32; neuroblastoma, and T98G; glioblastoma) and liver cell lines (Huh7 and HepG2), but not in other cell lines. Moreover, co-culturing type II T. gondii-infected THP-1 human monocytes with the brain cell lines inhibited the IDO1-mediated anti-T. gondii response in a GRA15-dependent manner. These data suggest that a GRA15-dependent virulence mechanism antagonizes the IDO1-dependent host immune response in human brain cells.

Original languageEnglish
Article number00140
JournalFrontiers in Cellular and Infection Microbiology
Issue numberMAY
Publication statusPublished - 2019
Externally publishedYes


  • GRA15
  • Human
  • IDO1
  • IFN-γ
  • Neuron
  • Toxoplasma gondii
  • Toxoplasmosis

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Microbiology (medical)
  • Infectious Diseases


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