Brussels, 03 Oct 2006
Scientists at Sweden's Karolinska Institute have developed a new malaria drug which could help to treat the most serious forms of the disease. Malaria is caused by a parasite called Plasmodium falciparum, which is transmitted by mosquitoes of the genus Anopheles. After a brief spell in the host's liver, the parasites infect the body's red blood cells.
Normally, the red blood cells would be swept along in the bloodstream to the spleen, where they would be destroyed. The parasites stop this happening by causing the cells to stick to both other red blood cells and the walls of blood vessels. They do this by producing proteins which protrude from the surface of the cell and bind with receptors on other blood cells and blood vessel walls. Soon, clumps of red blood cells build up and block the blood vessels, restricting the flow of blood into the brain and other organs.
It is this blocking of the blood vessels which leads to the classical symptoms of severe malaria, which include anaemia, respiratory problems, and encephalopathy. Researchers have spent many years looking for ways to 'unstick' the infected blood cells so that they can go on to be destroyed by the spleen.
In the past, an anti-coagulatory medicine called heparin was used to treat severe cases of malaria. However, while it was largely successful at releasing the blood cells, heparin also caused a number of serious side-effects such as internal bleeding, and its use as a malaria treatment came to an end.
Now, researchers at the Karolinska Institute have modified heparin to create a new drug, called a dGAG (depolymerised glycosaminoglycan). Tests in rats and primates show that dGAG both prevents infected red blood cells from becoming 'sticky' and breaks up existing clumps of cells. Unlike heparin, it has no effect on normal blood coagulation.
'There's often a lack of ability to treat people suffering from severe malaria,' said Professor Mats Wahlgren, who leads the research group. 'We've developed a substance that might be able to help these patients.'
The team now hopes that the new drug will prove as effective in humans as it was in animals.
According to figures from the World Health Organisation, malaria kills over a million people a year, many of them children.Karolinska Institutet: