STANFORD, Calif. - Toxoplasma is arguably the most successful animal parasite on earth: It infects hundreds of species of warm-blooded animals, most notably half of humanity. Its unusual ability to overcome the numerous challenges of infecting and reproducing inside such a wide range of creatures has long intrigued scientists, and now researchers at the Stanford University School of Medicine have identified two of the proteins critical to its ability to thrive.
The findings will be published in the Dec. 15 issue of Science by a team led by John Boothroyd, PhD, professor of microbiology and immunology. Working with mice, the researchers identified two genes that produce two proteins that Toxoplasma introduces into the cells of the host it infects. What's more, the researchers showed for the first time that certain changes in either of the proteins - called kinases - ramped up 10,000-fold the damage that Toxoplasma inflicted on the lab mice.
"This was a totally unknown phenomenon," said Boothroyd.
Although the majority of people infected by Toxoplasma have no symptoms, it can cause severe infections in individuals with compromised immune systems. In addition, women infected for the first time while pregnant can pass the organism to their fetuses, potentially resulting in sight and hearing problems as well as learning disabilities. The new findings have implications for determining how to treat these and other infected people: More aggressive therapy may be warranted if a strain that contains the proteins that increase virulence is the cause of the infection.
Humans can become infected by the parasite by accidentally consuming
or inhaling the cysts from infected cat feces, by eating meat from an
infected animal - especially pork, lamb or venison - or by drinking
contaminated water. Cats are the primary carriers of Toxoplasma,
though they rarely exhibit
Contact: Mitzi Baker
Stanford University Medical Center