Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Parasites persuade immune cells to invite them in for dinner

24.08.2009
The parasites that cause leishmaniasis use a quirky trick to convince the immune system to effectively invite them into cells for dinner, according to a new study published today in PLoS Pathogens.

The researchers, from Imperial College London, say their findings improve understanding of the way Leishmania parasites establish an infection and could aid the search for a vaccine against this neglected tropical disease.

Leishmania parasites are transmitted by sand flies. After the parasites infect a sand fly, they make a sticky gel so that when the fly bites a human, it regurgitates this gel into the body. Today's research, which was funded by the Wellcome Trust, shows that the gel persuades immune cells known as macrophages to feed the parasites, rather than killing them.

Leishmaniasis is an infection caused by Leishmania parasites that affects around 12 million people per year, mainly in tropical and sub-tropical countries. Symptoms include disfiguring and painful skin ulcers and in severe cases the infection can also spread to the internal organs. Patients with the infection often suffer from social exclusion because of their disfigurement. There is currently no vaccine to protect against infection and although treatments are available, they are not always effective and access to drugs is limited in many areas.

Leishmania-infected sand flies carry the parasites in their midgut. The parasites produce a gel that turns into a plug, stopping anything from passing in or out of the fly's gut. The fly must regurgitate the gel plug before it can feed on human blood. When the fly bites a person, its barbed mouth parts tear the skin so when it regurgitates parasites along with the gel plug, the skin becomes infected.

Today's study shows that the gel's work doesn't stop there - it also helps the parasites to establish an infection by enticing macrophages to the bite site. Macrophages usually kill invading pathogens by eating and digesting them. However, according to the new research, the gel persuades macrophages to engulf the parasites and feed them rather than digest them. This happens within the first few days following infection, enabling the parasites to establish themselves and infect the skin.

Previous research suggested that the sand fly's saliva could be involved in manipulating the immune system. Today's study suggests that the gel has an even bigger effect than the saliva on establishing infection.

Dr Matthew Rogers, lead author of the study from the Division of Investigative Science at Imperial College London, said: "Leishmaniasis is a very debilitating disease, yet we know comparatively little about the way the parasites are transmitted by sand flies. This is because when scientists study the disease they usually inject the parasite into tissues without including the gel or the sand fly's saliva. Our new research shows that we must consider the way the parasites enter the body - along with the gel and saliva - if we are to recreate infection and get an accurate picture of what is going on.

"Our new research shows that Leishmania parasites are very cunning - they make their own gel to control the human immune system so they can establish a skin infection. There is more work to be done here - our previous work in mice has suggested that injecting a synthetic version of the gel into people might provide them with some protection against infection and we would like to explore this further," added Dr Rogers.

The researchers looked at Leishmania infection in mice and found that the gel, called promastigote secretory gel (PSG) enticed macrophages to the site of entry. They compared the effect of PSG with the effects of saline and sand fly saliva on the number of macrophages recruited to a bite site, 4-72 hours after the bite. In the experiment, PSG recruited 108 times more macrophages to the bite than saline and five times more than sand fly saliva.

The researchers also found that PSG persuaded macrophages to feed, rather than kill, the parasites. When macrophages want to kill a pathogen, they produce nitric oxide. However, the researchers' experiments showed that PSG influences the immune cells to produce food, in the form of polyamines, for the parasites instead.

Finally, the researchers looked at the effect of PSG on parasite survival in vitro. They infected macrophage cells with Leishmania parasites with and without PSG. They found that more parasites survived in the first 48 hours following infection when PSG was added; both the proportion of infected cells and the number of parasites in the cells increased by up to 8-fold with PSG. The parasite infection declined after 48 hours in cells both with and without PSG, suggesting an early window of time in which PSG helps the parasites establish an infection.

This research was a collaboration between Imperial College London, Liverpool School of Tropical Medicine and the London School of Hygiene and Tropical Medicine, led by Imperial.

Lucy Goodchild | EurekAlert!
Further information:
http://www.imperial.ac.uk

More articles from Life Sciences:

nachricht Rutgers scientists discover 'Legos of life'
23.01.2018 | Rutgers University

nachricht Researchers identify a protein that keeps metastatic breast cancer cells dormant
23.01.2018 | Institute for Research in Biomedicine (IRB Barcelona)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Optical Nanoscope Allows Imaging of Quantum Dots

Physicists have developed a technique based on optical microscopy that can be used to create images of atoms on the nanoscale. In particular, the new method allows the imaging of quantum dots in a semiconductor chip. Together with colleagues from the University of Bochum, scientists from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute reported the findings in the journal Nature Photonics.

Microscopes allow us to see structures that are otherwise invisible to the human eye. However, conventional optical microscopes cannot be used to image...

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Rutgers scientists discover 'Legos of life'

23.01.2018 | Life Sciences

Seabed mining could destroy ecosystems

23.01.2018 | Earth Sciences

Transportable laser

23.01.2018 | Physics and Astronomy

VideoLinks Science & Research
Overview of more VideoLinks >>>