Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists reveal malaria parasites' tactics for outwitting our immune systems

01.12.2009
Malaria parasites are able to disguise themselves to avoid the host's immune system, according to research funded by the Wellcome Trust and published today in the journal Proceedings of the National Academy of Sciences.

Malaria is one of the world's biggest killers, responsible for over a million deaths every year, mainly in children and pregnant women in Africa and South-east Asia. It is caused by the malaria parasite, which is injected into the bloodstream from the salivary glands of infected mosquitoes. There are a number of different species of parasite, but the deadliest is the Plasmodium falciparum parasite, which accounts for 90 per cent of deaths from malaria.

The malaria parasite infects healthy red blood cells, where it reproduces. The P. falciparum parasite generates a family of molecules, known as PfEMP1, that are inserted into the surface of the infected red blood cells. The cells become sticky and adhere to the walls of blood vessels in tissues such as the brain. This prevents the cells being flushed through the spleen, where the parasites would be destroyed by the body's immune system, but also restricts blood supply to vital organs.

Symptoms can differ greatly between young and older children depending on previous exposure to the parasite. In young children, the disease can be extremely serious and potentially fatal if untreated; older children and adults who have grown up in endemic areas are resistant to severe malaria but rarely develop the ability to rid their bodies of the parasite.

Each parasite has 'recipes' for around sixty different types of PfEMP1 molecule written into its genes. However, the exact recipes differ from parasite to parasite, so every new infection may carry a set of molecules that the immune system has not previously encountered. This has meant that in the past, researchers have ruled out the molecules as vaccine candidates. However there appear to be at least two main classes of PfEMP1 types within every parasite, suggesting different broad tactical approaches to infecting the host. The most efficient tactic or combination of tactics to use may depend on the host's immunity.

Now, Dr George Warimwe and colleagues from the Kenya Medical Research Institute (KEMRI)-Wellcome Trust Programme and the Wellcome Trust Sanger Institute, have shown that the parasites adapt their molecules depending on which antibodies it encounters in the host's immune response. They have also found evidence to suggest that there may be a limit to the number of molecular types that are actually associated with severe disease.

"The malaria parasite is very complex, so our immune system mounts many different responses, some more effective than others and many not effective at all," explains Dr Peter Bull from the KEMRI-Wellcome Trust Programme and the University of Oxford, who led the research. "We know that our bodies have great difficulty in completely clearing infections, which begs the question: how does the parasite manage to outwit our immune response? We have shown that, as children begin to develop antibodies to parasites, the malaria parasite changes its tactics to adapt to our defences."

The researchers at the KEMRI-Wellcome Trust Programme studied malaria parasites in blood samples from 217 Kenyan children with malaria. They found that a group of genes coding for a particular class of PfEMP1 molecule called Cys-2 tended to be switched on when the children had a low immunity to the parasite; as immunity develops, the parasite switches on a different set of genes, effectively disguising it so that immune system cannot clear the infection

Dr Warimwe and colleagues also found an independent association between activity in Cys-2 genes and severe malaria in the children, suggesting that specific forms of the molecule may be more likely to trigger specific disease symptoms. This supports a previous study in Mali which suggested that the same class of PfEMP1 molecule was associated with cerebral malaria.

The findings could suggest a new approach to tackling malaria, in terms of both vaccine development and drug interventions, argues Dr Bull.

"If there exists a limited class of severe disease-causing variants that naturally-exposed children learn to recognise readily, this opens up the possibility of designing a vaccine against severe malaria that mimics an adult's immune response, making the infections less dangerous. But this would still be an enormous task.

"Similarly, if we can establish what the particular class of molecules are doing, then we may be able to develop a drug to modify this function and relieve symptoms of severe disease."

Craig Brierley | EurekAlert!
Further information:
http://www.wellcome.ac.uk

More articles from Health and Medicine:

nachricht The genes are not to blame
20.07.2018 | Technische Universität München

nachricht Targeting headaches and tumors with nano-submarines
20.07.2018 | Universitätsmedizin der Johannes Gutenberg-Universität Mainz

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>