Study shows how Toxoplasma parasite successfully spreads in the body

The parasite Toxoplasma is carried by a large portion of the global human population. Now a study led by researchers at Stockholm University shows how this microscopic parasite so successfully spreads in the body, for example to the brain. The parasite infects immune cells and hijacks their identity. The study is published in the scientific journal Cell Host & Microbe.

In order to fight infections, the various roles of immune cells in the body are very strictly regulated. Scientists have long wondered how Toxoplasma manages to infect so many people and animal species and spread so efficiently.

We have now discovered a protein that the parasite uses to reprogram the immune system."

Arne ten Hoeve, Researcher, Department of Molecular Biosciences, Wenner-Gren Institute at Stockholm University

The study shows that the parasite injects the protein into the nucleus of the immune cell and thus changes the cell's identity. The parasite tricks the immune cell into thinking it is another type of cell. This changes the gene expression and behavior of the immune cell. Toxoplasma causes infected cells which normally should not travel in the body to move very quickly and in this way the parasite spreads to different organs.

The phenomenon has been described as Toxoplasma turning immune cells into Trojan horses or wandering "zombies" that spread the parasite. The newly published study provides a molecular explanation for the phenomenon, and also shows that the parasite is much more targeted in its spread than previously thought.

"It is astonishing that the parasite succeeds in hijacking the identity of the immune cells in such a clever way. We believe that the findings can explain why Toxoplasma spreads so efficiently in the body when it infects humans and animals," says Professor Antonio Barragan, who led the study, which was carried out in collaboration with researchers from France and the USA.