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Figuring out a parasite's secrets – insights from studying Toxoplasma gondii

Welcome to Biomed Bites, a weekly feature that highlights some of Stanford’s most innovative research and introduces Scope readers to innovators in a variety of disciplines. 

You've probably heard that pregnant women shouldn't get near the litter box. The reason is that many kitties carry a parasite called Toxoplasma gondii, which is transmitted through their feces. The parasite infects about 2 billion people worldwide, according to Stanford microbiologist John Boothroyd, PhD.

Boothroyd, who also serves as the associate vice provost for graduate education, directs a lab that has uncovered some of the basic biology of this single-celled protozoan parasite. Here's Boothroyd in the video above:

Most of the time, this causes no significant disease, very few symptoms and probably something that most of these people will never know they were infected with. Occasionally, however, this parasite can cause devastating disease. It can affect the brain of the unborn child, it can cause severe neurological problems, it can even kill the developing fetus.

Toxoplasmosis, or infection with the parasite, can also cause serious complications in immunocompromised individuals. Boothroyd said he was drawn to the study of the T. gondii because it is clinically significant — he has the opportunity to help millions of people: "I wanted something where I felt the work we were doing was worth the many, many hours that I and the people I worked with put in to the daily effort." T. gondii is also related to the Plasmodium parasites that cause malaria and some of the work from Boothroyd's lab has been translated into insights into malaria.

Boothroyd's team also identified the T. gondii protein that triggers the immune response in humans. With that knowledge, the investigators were able to insert the gene coding for that protein into yeast, letting the yeast produce the protein, "instead of having to grow the parasite in literally hundreds of thousands of mice a year and then killing those mice to get the parasite," Boothroyd said. He went on to explain:

The situation in which Toxoplasma presents the most significant problem for the doctor and for the patient is in the pregnant woman. The challenge becomes first, is she infected, and if so, has the parasite crossed the placenta and reached the fetus. And third, what is the consequence of the infection in the fetus? All three of those we have addressed through our work.

Although much about the parasitic diseases remains unknown, Boothroyd is glad he picked T. gondii to focus on: "I think we've been able to do some real good with this work."

Learn more about Stanford Medicine’s Biomedical Innovation Initiative and about other faculty leaders who are driving biomedical innovation here.

Previously: Stanford microbiologist's secret sauce for disease detection, Cat guts, car crashes and warp-speed Toxoplasma infections and Patrick House discusses Toxoplasma gondii, parasitic mind control and zombies

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