Gene study demystifies malarial parasite

Scientists have discovered the genetic basis of the hide and seek game played by the malarial parasite on the human immune system.

Scientists have discovered the genetic basis of the 'hide and seek' game played by the malarial parasite on the human immune system, opening doors to new drugs against Plasmodium falciparum.

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When the parasite enters human cells, one of its proteins appears on the outside of the cell. This would normally give the immune system a target to aim at in order to destroy infected cells.

But by the time the immune system has produced antibodies that recognise the malaria protein, the parasite is a step ahead, presenting a different form of the protein that the antibodies cannot recognise.

Now, a team led by Alan Cowman and Brendan Crabb at The Walter and Eliza Hall Institute of Medical Research in Melbourne, has shown that the parasite varies the protein by 'silencing' some of its genes, reports science portal Scidev.

Researchers have known for about a decade that a family of at least 50 malaria genes known as 'var' is responsible for the ability of the parasite to disguise itself, constantly changing its version of protein to avoid being detected.

They are activated one at a time to produce different forms of the protein. However, their mechanism the parasite uses has been elusive.

According to the new discovery, the 'silencing' of genes is done by producing other proteins that wrap tightly around the parasite's own DNA, blocking and deactivating var genes.

The researchers showed that one of the proteins involved is called SIR2. When they modified the parasite to stop making SIR2, more of its var genes remained active.

According to Cowman, forcing the parasite to turn all of the var genes on would allow the human immune system to 'see' all variations of the protein that the parasite produces on the surface of infected cells. This would enable the body to fight infection.

The research suggests that drugs targeting the method malaria uses to hide its var genes could make the parasite vulnerable to the immune system.

However, the researchers add that SIR2 is only part of the puzzle, and that more research will be needed to determine what other factors control how many var genes are active at one time.