Genetic diversity the key to malaria's success
[MELBOURNE] Research identifying common genes between different populations of malaria parasites could lead to the development of a vaccine, say researchers.
Dr Alyssa Barry, from the Burnet Institute in Australia, announced the results of a genetic study of the malaria parasite at the 5th World Conference of Science Journalists (WCSJ) in Melbourne, Australia (19 April).
Developing a vaccine for malaria has proven difficult because the malaria parasite, Plasmodium falciparum, is able to outwit the human immune system while it multiplies in the body.
Barry, the lead researcher on the project, explained that when the malaria parasite infects a person's red blood cells, it produces molecules that the blood cells then exhibit on their surface. These molecules are what alert the immune system into launching an attack.
The parasite, however, can switch the version of the molecule on the surface of the cells by expressing one of up to 60 genes from a family of genes called var. This confuses the immune system and allows the parasite to hide.
"This improves the parasite's chances of being transmitted to another mosquito carrier," said Barry.
Var genes differ between malaria parasites in one region, as well as between geographically distinct populations, and this diversity is thought to be partly responsible for the parasite's success. Up until now, the extent of the diversity has been unclear.
Working with researchers from the Africa, Papua New Guinea, the United Kingdom and the United States, the group sequenced a segment of the var genes of individual malaria parasites from Papua New Guinea and other areas around the world.
They found a total of 895 different versions of the segment of the var gene in a sample of just 80 parasites, indicating that var gene diversity globally is immense.
But nearly 40 per cent of var gene types identified in Papua New Guinea were also found in samples from different countries.
The next step will be to identify shared genes which can be used as targets for malaria vaccines, said Barry. This information can also be used for surveillance of the malaria parasite.
There are about 300 million cases of malaria each year globally, resulting in more than a million deaths, according to the World Health Organization. Around 90 per cent of these deaths occur in Africa, mostly in young children.Link to full paper in PLoS Pathogens
Reference: PLoS Pathogens doi: 10.1371/journal.ppat.0030034. (2007)