PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Biologists find clues to a parasite's inconsistency

2013-12-20
(Press-News.org) Contact information: Sarah McDonnell
s_mcd@mit.edu
617-253-8923
Massachusetts Institute of Technology
Biologists find clues to a parasite's inconsistency CAMBRIDGE, MA -- Toxoplasma gondii, a parasite related to the one that causes malaria, infects about 30 percent of the world's population. Most of those people don't even know they are infected, but a small percentage develop encephalitis or ocular toxoplasmosis, which can lead to blindness.

MIT biologist Jeroen Saeij and his colleagues are trying to figure out why some forms of the disease are so innocuous, while others ravage their victims. In their latest paper, they analyzed 29 strains of the parasite and found that some of those endemic to South America or atypical in North America provoke very strong inflammation in the cells they infect, which can severely damage tissue.

"You have a lot of strains that are silent, and then you have these exotic strains that can cause very severe disease," says Saeij, the Robert A. Swanson Career Development Associate Professor of Life Sciences. "The goal of the project was to see how different are these South American strains compared to strains that are really prevalent in North America and Europe."

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. 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.

The strains that circulate most commonly in North America and Europe usually cause problems only in people with suppressed immune systems, such as AIDS patients or transplant recipients, although some atypical North American and European strains have been associated with severe ocular toxoplasmosis. It can also be dangerous for a woman to become infected while pregnant, as the parasite can cause birth defects.

In South America, there is a much higher incidence of severe symptoms in otherwise healthy people. Scientists are still unsure what makes some South American strains so virulent, in part because most studies have focused on the North American and European varieties.

Hyperinflammatory response

In the new study, which appears this week in the journal PLOS Pathogens, Saeij and colleagues infected mouse immune cells known as macrophages with each of the 29 strains they had collected, representing global diversity. Macrophages are one of the parasite's major targets and also a critical part of the host's immune response.

After infecting the cells, the researchers sequenced all of the messenger RNA molecules in the host cells. This reveals which genes — both parasite and host — are most active during infection.

Most strikingly, some South American and some atypical North American strains induced a type of immune reaction usually only seen during viral infection, known as the type 1 interferon response. This generates very strong inflammation in the host cells, which the researchers suspect may be causing the severe effects produced by those strains.

Paradoxically, the parasite only sets off this immune response after the host cell has killed it, spilling the parasite's DNA and RNA into the cell.

"It's often not the parasite that causes all the damage, but it's actually the host immune response that's causing most of the damage," Saeij says. "We think that maybe what's happening is these parasites come in and they trigger a hyperinflammatory host immune response that might cause damage to the eyes."

Toxoplasma is one of the few parasites that can infect any warm-blooded animal, says Mariane Melo, an MIT postdoc and the paper's lead author. "For an organism to be able to infect any host and any cell, it needs to be able to have a very big arsenal of molecules that can function in the different hosts and the different cells," Melo says. "However, we believe that different strains may have evolved to be able to maintain and reproduce optimally in a specific niche in nature, which may explain why different strains of Toxoplasma have such varying effects in different organisms."

She notes that a strain adapted to long-term survival in rats may cause a fatal infection in mice, or vice versa, because it might modulate host immune responses too much or not enough in hosts it is not optimally adapted to.

The MIT researchers are now investigating why host cells kill certain South American strains so much more effectively, and why that killing provokes the interferon response. They have put their data, which includes gene expression profiles for all 29 strains, into a publicly available database for other researchers to use and add to. "There's a lot of data, and we still understand very little of it," Saeij says. "We hope that other people will now start studying more of these South American strains."

###

The research was funded by the New England Regional Center of Excellence, the Pew Scholars Program in the Biomedical Sciences, a Robert A. Swanson Career Development Award, the Knights Templar Eye Foundation, the Wellcome Trust Foundation, and the National Institutes of Health.

END



ELSE PRESS RELEASES FROM THIS DATE:

Electron 'antenna' tunes in to physics beyond Higgs

2013-12-20
Electron 'antenna' tunes in to physics beyond Higgs Though it was hailed as a triumph for the "Standard Model" of physics – the reigning model of fundamental forces and particles – physicists were quick to emphasize that last year's discovery of the Higgs boson still ...

Opposing phenomena possible key to high-efficiency electricity delivery

2013-12-20
Opposing phenomena possible key to high-efficiency electricity delivery The coexistence of two opposing phenomena might be the secret to understanding the enduring mystery in physics of how materials heralded as the future of powering our homes and communities ...

Electron's shapeliness throws a curve at supersymmetry

2013-12-20
Electron's shapeliness throws a curve at supersymmetry A small band of particle-seeking scientists at Yale and Harvard has established a new benchmark for the electron's almost perfect roundness, raising doubts about certain theories that predict what lies beyond physics' ...

Salt under pressure is not NaCl

2013-12-20
Salt under pressure is not NaCl In the very beginning of the school chemistry course, we are told of NaCl as an archetypal ionic compound. Being less electronegative, sodium loses its electron to chlorine, which, following the "octet rule", thus acquires the ...

Amino acid's increase is suspected in diabetes

2013-12-20
Amino acid's increase is suspected in diabetes Research examines effects of lower and higher tyrosine levels SAN ANTONIO (Dec. 19, 2013) — Elevated levels of an amino acid, tyrosine, alter development and longevity in animals and may ...

'Universal ripple' could hold the secret to high-temperature superconductivity

2013-12-20
'Universal ripple' could hold the secret to high-temperature superconductivity UBC researchers have discovered a universal electronic state that controls the behavior of high-temperature superconducting copper-oxide ceramics. The work, published ...

Protein links liver cancer with obesity, alcoholism, and hepatitis

2013-12-20
Protein links liver cancer with obesity, alcoholism, and hepatitis A new study identifies an unexpected molecular link between liver cancer, cellular stress, and risk factors for developing this cancer – obesity, alcoholism, and viral hepatitis. In the study by University ...

Inadequate pregnancy weight gain a risk factor for infant mortality

2013-12-20
Inadequate pregnancy weight gain a risk factor for infant mortality One-quarter of US women gain an inadequate amount of weight during pregnancy, University of Maryland School of Public Health study shows Women who do not gain enough weight during pregnancy are at increased ...

Lactation consultant visits spur breastfeeding among women who usually resist it

2013-12-20
Lactation consultant visits spur breastfeeding among women who usually resist it December 19, 2013—(BRONX, NY)—In two separate clinical trials, researchers at Albert Einstein College of Medicine of Yeshiva University have found that periodic meetings ...

Researchers show the power of mirror neuron system in learning and language understanding

2013-12-20
Researchers show the power of mirror neuron system in learning and language understanding TEMPE, Ariz. – Anyone who has tried to learn a second language knows how difficult it is to absorb new words and use them to accurately express ideas in a completely new cultural ...

LAST 30 PRESS RELEASES:

Strain “trick” improves perovskite solar cells’ efficiency

How GPS helps older drivers stay on the roads

Estrogen and progesterone stimulate the body to make opioids

Dancing with the cells – how acoustically levitating a diamond led to a breakthrough in biotech automation

Machine learning helps construct an evolutionary timeline of bacteria

Cellular regulator of mRNA vaccine revealed... offering new therapeutic options

Animal behavioral diversity at risk in the face of declining biodiversity

Finding their way: GPS ignites independence in older adult drivers

Antibiotic resistance among key bacterial species plateaus over time

‘Some insects are declining but what’s happening to the other 99%?’

Powerful new software platform could reshape biomedical research by making data analysis more accessible

Revealing capillaries and cells in living organs with ultrasound

American College of Physicians awards $260,000 in grants to address equity challenges in obesity care

Researchers from MARE ULisboa discover that the European catfish, an invasive species in Portugal, has a prolonged breeding season, enhancing its invasive potential

Rakesh K. Jain, PhD, FAACR, honored with the 2025 AACR Award for Lifetime Achievement in Cancer Research

Solar cells made of moon dust could power future space exploration

Deporting immigrants may further shrink the health care workforce

Border region emergency medical services in migrant emergency care

Resident physician intentions regarding unionization

Healthy nutrition and physical lifestyle choices lower cancer mortality risk for survivors, new ACS study finds

Mass General Brigham researchers reveal 17 modifiable risk factors shared by stroke, dementia, and late-life depression

Promising drug discovery research gets funding boost from Ontario Institute for Cancer Research

Carbon capture could become practical with scalable, affordable materials

USC Norris Comprehensive Cancer Center opens state-of-the-art Newport Beach Radiation Oncology and Imaging Center

Chan Zuckerberg Biohub New York announces new investigators for immune system research to improve human health

New research suggests White Americans in areas with higher Black poverty are more likely to blame racial inequality on lack of effort

Solar wave squeezed Jupiter’s magnetic shield to unleash heat

Cognitive decline comes sooner for people with heart failure

SMEs’ ability to innovate is strongly tied to the learning and decision-making skills of managers

Researchers recycle wind turbine blade materials to make improved plastics

[Press-News.org] Biologists find clues to a parasite's inconsistency