Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers get to heart of tropical disease

23.06.2006
A new study found that mice lacking a gene crucial to the normal functioning of their immune systems didn't become ill when they were exposed to a pathogen that causes a horrendous infection in the liver and the spleen.

The pathogen, called Leishmania donovani, infects certain internal organs. The parasite causes visceral leishmaniasis which, if left untreated, is almost always fatal. Cases in the United States are extremely rare, but the disease, which is transmitted through the bite of a sand fly, is common in tropical and subtropical countries such as Iraq, Iran and Afghanistan.


Leishmania donovani in a bone marrow cell. Image credit: [CDC/Dr. L.L. Moore, Jr (PHIL #468), 1969. via Wikipedia.]

The finding may lend insight into creating new drugs to treat different diseases that affect the liver, said Abhay Satoskar, the study's lead author and an assistant professor of microbiology at Ohio State University.

The gene makes a protein called STAT1, and its production is triggered whenever the immune system senses a foreign bacterium, virus or other pathogen. STAT1 activation is a critical step in the immune system response, as this protein activates other key immune substances.

So it didn't make sense to the researchers that mice that couldn't produce STAT1 would remain healthy.

“It took us completely by surprise,” Satoskar said. “We knew from previous work that mice that lack the substances produced in response to STAT1 develop serious infections. We thought we'd see that in this study, too.”

The study appears as a Cutting Edge paper in the July 1 issue of the Journal of Immunology website.

The researchers infected groups of mice with L. donovani. Mice in one group lacked the gene that makes STAT1. Mice in another group lacked the gene that makes an immune system protein called T-bet. In a normal immune response to infection, STAT1 triggers the production of T-bet. Together, these proteins are responsible for the production of interferon gamma, an important protein that helps launch a full-blown immune system attack against foreign pathogens.

A group of mice with both STAT1 and T-bet genes intact served as a control.

About two weeks after infection, the researchers began measuring the number of L. donovani parasites in the animals' livers.

The pathogen went wild in the mice that lacked T-bet – the researchers found thousands upon thousands of the parasites in the livers of these animals.

Yet there were next to no parasites in the mice without STAT1.

“Two weeks after infection, the mice without STAT1 had 25-fold fewer parasites in their liver tissue than the normal mice, and about 100-fold fewer parasites than the mice without T-bet,” Satoskar said. “Visceral leishmaniasis never developed in the animals without STAT1 – the parasites weren't able to establish an infection in the animals' livers and spleens.”

The researchers also measured parasite levels in the livers two months after infection. Again, levels were quite high in the mice without T-bet, while normal mice and mice without STAT1 showed no sign of the disease.

While the normal mice weren't sick – they showed no physical signs of having leishmaniasis, such as inflammation of the liver and spleen – Satoskar said the parasite was still in their systems.

“Once infected, the parasite never goes away completely,” Satoskar said. “It's always hiding somewhere.”

Ironically, L. donovani thrives in the liver and spleen by infecting the very cells that the immune system uses to rid the parasite from the body. These cells are called macrophages – a kind of garbage collector for the immune system, as they clean out everything from red blood cells that have died to infectious pathogens. But enough L. donovani parasites can overtake a macrophage's ability to clean up.

“L. donovani infection failed to launch in mice without STAT1 because there weren't enough macrophages in the liver for the parasite to infect, and these are the very immune cells that are essential for successful survival and replication of Leishmania parasites in the host,” Satoskar said.

The researchers aren't suggesting that STAT1 activation should be stopped in order to prevent visceral leishmaniasis. However, they want to figure out how this protein's absence keeps macrophages from flooding into the liver during the early stages of infection.

If they can do that, it may be possible to create a drug to prevent L. donovani from infecting the liver and the spleen. Although there are medications available to treat the symptoms of visceral leishmaniasis, they can be toxic and sometimes expensive for the people who need them the most.

Satoskar conducted the study with colleagues from Ohio State, Montreal General Hospital in Montreal, Canada, and with the Harvard School of Public Health and Harvard Medical School.

This work was supported by grants from the National Institutes of Health, the National Institute of Dental and Cranial Research, the National Science Foundation and the Ellison Medical Foundation.

Abhay Satoskar | EurekAlert!
Further information:
http://www.osu.edu

More articles from Life Sciences:

nachricht Embryonic development: How do limbs develop from cells?
18.05.2018 | Humboldt-Universität zu Berlin

nachricht Reading histone modifications, an oncoprotein is modified in return
18.05.2018 | American Society for Biochemistry and Molecular Biology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

Im Focus: Computer-Designed Customized Regenerative Heart Valves

Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.

Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...

Im Focus: Light-induced superconductivity under high pressure

A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.

Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Supersonic waves may help electronics beat the heat

18.05.2018 | Power and Electrical Engineering

Keeping a Close Eye on Ice Loss

18.05.2018 | Information Technology

CrowdWater: An App for Flood Research

18.05.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>