Florence Dzierszinski in the world of parasites

By Nadine Fortin | Have you ever noticed the warning on a cat litter bag? It can be quite scary the first time you read it: “Please wash hands thoroughly after handling used cat litter. We want to remind pregnant women and people with immune deficiency that a parasite sometimes found in cat feces can cause toxoplasmosis.”

Although toxoplasmosis is usually benign in healthy adults, the food and waterborne intracellular parasite Toxoplasma gondii is a threat when transmitted through the placenta to the developing fetus, or in immune-suppressed individuals such as transplant, cancer and AIDS patients to whom it can lead to life-threatening encephalitis.

The world’s first outbreak of acute toxoplasmosis associated with a municipal water supply was recognized in 1995 in Victoria, BC, where feces from domestic cats or cougars are presumed to have contaminated the surface water.

Florence Dzierszinski in front of a rosette of Toxoplasma gondii, a a parasite that can cause encephalitis. The electronic microscopy was taken by J.F. Dubremetz.

Toxoplasma can infect any mammal, but it is only in cats that the parasite can form the infectious offspring that are released in the feces. Why? “Researchers are still looking for an answer,” said Florence Dzierszinski, the new Canadian Research Chair in Parasite Pathogenesis at the Institute of Parasitology located on the Macdonald Campus.

In other mammals (including humans) and in birds, chronic infection is localized mainly in the brain and in muscles, and parasite transmission from one host to another is ensured via consumption of undercooked meat.

“With the re-emergence of tuberculosis, malaria and opportunistic infections associated with AIDS, it is clear that infectious diseases mediated by intra-cellular pathogens constitute a contemporary problem of growing significance,” explained Dzierszinski.

Because Toxoplasma gondii is a pathogen that induces a strong and protective immune response in the host, Dzierszinski uses this parasite as a model to understand how to develop protective cellular vaccines to intracellular pathogens (against which antibodies are not useful) for animal and human purposes.

Dzierszinski is studying the host-parasite interactions that exist between Toxoplasma gondii and the infected host cell in order to understand how this parasite stimulates and interferes with the immune response of the host.

She developed transgenic parasite models to study different aspects of this question when she was a post-doctoral fellow at the University of Pennsylvania.

Using genetics, genomics, immunology and cell biology, she wants to isolate parasite molecules that interact with the host response.

She also studies how immunity develops in “immune privileged areas” like the brain, where the encysted form of this parasite resides.

Her work could have a major impact not only on human but also on animal health: Toxoplasma gondii leads to congenital birth defects in farm animals and therefore to major financial losses to farmers.

Dzierszinski, who just received a CFI Grant, an NSERC Discovery Grant and an NSERC Research Tools and Instruments Grant after six years as a postdoctoral fellow, is still setting up her lab at the Institute of Parasitology and will welcome her first students this summer.

This science has been at the heart of her work since her doctoral studies in Lille, France, where she’s from.

But she won’t really feel at home here until her transgenic parasite models will be allowed to cross the border from the University of Pennsylvania and grow in their new house.

That’ll just be a matter of days.