The protozoan parasite Trypanosoma cruzi is responsible for the zoonotic
Chagas disease, a chronic and systemic
infection in humans and warm-blooded animals typically leading to progressive
dilated cardiomyopathy and gastrointestinal manifestations. In the present study, we report that the
transcription factor STAT1 (
signal transducer and activator of transcription 1) reduces the susceptibility of human cells to
infection with T. cruzi. Our in vitro data demonstrate that
interferon -γ (IFNγ) pre-treatment causes T. cruzi-infected cells to enter an anti-parasitic state through the activation of the
transcription factor STAT1. Whereas stimulation of STAT1-expressing cells with IFNγ significantly impaired intracellular replication of parasites, no protective effect of IFNγ was observed in STAT1-deficient U3A cells. The gene encoding indoleamine 2, 3-dioxygenase (ido) was identified as a STAT1-regulated target gene engaged in parasite clearance. Exposure of cells to T. cruzi trypomastigotes in the absence of IFNγ resulted in both sustained
tyrosine and
serine phosphorylation of STAT1 and its increased
DNA binding. Furthermore, we found that in response to T. cruzi the total amount of intracellular STAT1 increased in an infectious dose-dependent manner, both at the
mRNA and
protein level. While STAT1 activation is a potent strategy of the host in the fight against the invading pathogen, amastigotes replicating intracellularly antagonize this pathway by specifically promoting the dephosphorylation of STAT1
serine 727, thereby partially circumventing its protective effects. These findings point to the crucial role of the IFNγ/STAT1 signal pathway in the evolutionary combat between T. cruzi parasites and their host.