Navigation Links
MIT researchers study the danger of toxoplasma parasites
Date:1/4/2011

CAMBRIDGE, Mass. -- About one-third of the human population is infected with a parasite called Toxoplasma gondii, but most of them don't know it. Though Toxoplasma causes no symptoms in most people, it can be harmful to individuals with suppressed immune systems, and to fetuses whose mothers become infected during pregnancy. Toxoplasma spores are found in dirt and easily infect farm animals such as cows, sheep, pigs and chickens. Humans can be infected by eating undercooked meat or unwashed vegetables.

Jeroen Saeij, an assistant professor of biology at MIT is investigating a key question: why certain strains of the Toxoplasma parasite (there are at least a dozen) are more dangerous to humans than others. He and his colleagues have focused their attention on the type II strain, which is the most common in the United States and Europe, and is also the most likely to produce symptoms. In a paper appearing in the Jan. 3 online edition of the Journal of Experimental Medicine, the researchers report the discovery of a new Toxoplasma protein that may help explain why type II is more virulent than others.

Toxoplasma infection rates vary around the world. In the United States, it's about 10 to 15 percent, while rates in Europe and Brazil are much higher, around 50 to 80 percent. However, these are only estimates it is difficult to calculate precise rates because most infected people don't have any symptoms.

After an infection is established, the parasite forms cysts, which contain many slowly reproducing parasites, in muscle tissue and the brain. If the cysts rupture, immune cells called T cells will usually kill the parasites before they spread further. However, people with suppressed immune systems, such as AIDS patients or people undergoing chemotherapy, can't mount an effective defense.

"In AIDS patients, T cells are essentially gone, so once a cyst ruptures, it can infect more brain cells, which eventually causes real damage to the brain," says Saeij.

The infection can also cause birth defects, if the mother is infected for the first time while pregnant. (If she is already infected before becoming pregnant, there is usually no danger to the fetus.)

There are drugs that can kill the parasite when it first infects someone, but once cysts are formed, it is very difficult to eradicate them.

A few years ago, Saeij and colleagues showed that the Toxoplasma parasite secretes two proteins called rhoptry18 and rhoptry16 into the host cell. Those proteins allow the parasite to take over many host-cell functions.

In the new study, the MIT team showed that the parasite also secretes a protein called GRA15, which triggers inflammation in the host. All Toxoplasma strains have this protein, but only the version found in type II causes inflammation, an immune reaction that is meant to destroy invaders but can also damage the host's own tissues if unchecked. In the brain, inflammation can lead to encephalitis. This ability to cause inflammation likely explains why the type II strain is so much more hazardous for humans, says Saeij.

Saeij and his team, which included MIT Department of Biology graduate students Emily Rosowski and Diana Lu, showed that type II GRA15 leads to the activation of the transcription factor known as NF-kB, which eventually stimulates production of proteins that cause inflammation. The team is now trying to figure out how that interaction between GRA15 and NF-kB occurs, and why it is advantageous to the parasite.

Ultimately, Saeij hopes to figure out how the parasite is able to evade the immune system and establish a chronic infection. Such work could eventually lead to new drugs that block the parasite from establishing such an infection, or a vaccine that consists of a de-activated form of the parasite.


'/>"/>

Contact: Jessica Holmes
holmesj@mit.edu
617-253-2702
Massachusetts Institute of Technology
Source:Eurekalert

Related biology news :

1. NC State researchers get to root of parasite genome
2. Researchers find animal with ability to survive climate change
3. Researchers find an essential gene for forming ears of corn
4. Researchers note differences between people and animals on calorie restriction
5. Researchers study acoustic communication in deep-sea fish
6. Researchers discover that growing up too fast may mean dying young in honey bees
7. Researchers study how pistachios may improve heart health
8. UI researchers find potentially toxic substance present in Chicago air
9. Researchers develop new self-training gene prediction program for fungi
10. Case Western Reserve University researchers track Chernobyl fallout
11. Childrens National researchers develop novel anti-tumor vaccine
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/23/2017)... , March 23, 2017 The report "Gesture Recognition ... Biometric), Industry, and Geography - Global Forecast to 2022", published by MarketsandMarkets, the ... a CAGR of 29.63% between 2017 and 2022. ... ... ...
(Date:3/22/2017)... , March 21, 2017 Vigilant Solutions ... serving law enforcement agencies, announced today the appointment of ... director of public safety business development. Mr. ... enforcement experience, including a focus on the aviation transportation ... most recent position, Mr. Sheridan served as the Aviation ...
(Date:3/13/2017)... of security: Biometric Face Matching software  Continue Reading ... ... match face pictures against each other or against large databases. The recognition of ... ... for biometric Face Matching on the market. The speed is at 100 million ...
Breaking Biology News(10 mins):
(Date:3/23/2017)... ALBANY, New York , March 23, 2017 ... animal blood plasma products and derivatives market is fragmented due to the ... large players, such as Proliant, Thermo Fisher , and Sigma-Aldrich, ... clear leader, these three companies, collectively, held more than 76% of ... ...
(Date:3/22/2017)... TARRYTOWN, N.Y. , March 22, 2017 Regeneron ... among the Regeneron Genetics Center (RGC), U.K. Biobank and GSK ... in the U.K. Biobank resource. The initiative will enable researchers ... of new medicines for a wide range of serious and ... ...
(Date:3/22/2017)... 22, 2017 Good Start Genetics, a leading ... the 130 million covered lives mark through its most ... Texas . With newly signed contracts nationally ... enjoy strong payor acceptance based on the quality of ... genetic counseling, its industry-leading customer care and support and ...
(Date:3/22/2017)... BEACH, Florida , March 22, 2017 ... ... for various cancer conditions are being pressured as of late ... therapy for cancer pain management has a dramatic impact on ... up research and development activities for identifying new forms of ...
Breaking Biology Technology: