Toxoplasmosis: how does the parasite transform in humans?

Cats are the main targets of the parasite Toxoplasma gondii, but when a human consumes food soiled by feline droppings, he can in turn ingest the infectious agent. In humans, toxoplasmosis can take different cellular forms: tachyzoite, which leads to acute infections, and bradyzoite, responsible for chronic infections. In the review CellAmerican researchers show how the parasite changes shape in the cellular organism thanks to a protein called BFD1.

Multiple transformations of the parasite

The scientific community has already found that stressful conditions, such as thermal shock or basic pH, can lead to a change in Toxoplasma gondii : it changes from a tachyzoite to a bradyzoite form. To understand the molecular phenomena associated with these transformations, the researchers analyzed the gene expression profiles of the tachyzoite pathogen, then of the tachyzoite transformed into bradyzoite. With the “DNA scissors”, CRISPR-Cas9, the research team inactivated several genes in order to determine which one or which ones were linked to the transformation of the parasite. They found that a single gene is responsible for this: BFD1.

Sometimes serious complications

These discoveries will certainly make it possible to better manage the complications linked to the parasite. This is transformed several times during its life cycle, when it is ingested by a human, the parasite releases tachyzoites, capable of infiltrating tissues such as the retina or the brain. Then they turn into bradyzoites and remain permanently in these parts of the body without any medication being able to act on them. They can remain inactive for long periods and then be reactivated in case of immune deficiency. Some patients may develop a serious brain infection called encephalitis. These cases remain rare, according to the site health insurance, toxoplasmosis is generally mild and asymptomatic. 80% of people affected experience no symptoms.