Research reveals twist in the fight against malaria

New research published in the prestigious journal Science has challenged previous notions about how the body fights against malaria infection. Scientists have discovered that platelets, normally known for their role in preventing bleeding, can actually target and kill the parasite that causes malaria as it grows inside red blood cells.

The key to these latest findings is the discovery that a molecule on the red cell - called Duffy - is essential for platelet-mediated killing of the P. falciparum malaria parasite. This research is significant because most people living in Africa lack Duffy, and it could provide an explanation for why malaria is more common and more lethal in Africa than elsewhere in the world.

“We know that platelets defend infected people by killing the malaria parasites that infect the blood cells but the weapons used by the platelet were unknown. What we found was that platelets release a molecule called PF4 that kills the parasite, but what was really interesting is that PF4 needs to bind to the red cell Duffy molecule for this to occur,” explained lead author Associate Professor Brendan McMorran, Australian School of Advanced Medicine, Macquarie University.

The lack of Duffy on the red cell occurs through a genetic change, known as ‘Duffy-negativity’, and is a separate blood group. Other studies have estimated that 98-100% of individuals living in the equatorial regions of Africa are Duffy-negative.

“We know that Duffy-negativity gives them resilience against another malarial parasite, P. vivax, but as a consequence has produced a chink in the protective armour in these people and suggests another reason why falciparum malaria is a major problem in Africa,” said Associate Professor McMorran.

The WHO World Malaria Report 2011 estimated 216 million episodes of malaria in 2010 with 81% of these occurring in Africa. Over half a million deaths in 2010 were due to malaria; 91% of these occurred in Africa. The majority of those killed are children aged less than five years. This equates to a child dying of malaria every 60 seconds.

The WHO also notes that reducing the burden of malaria remains a greater problem in Africa than the rest of world. Over the past 10 years, incidence and death rates have declined only 1 and 10% respectively in Africa, compared to 17 and 26% in the rest of the world.

“This finding adds to the ongoing challenges to control this disease. Recently reported findings in The New England Journal of Medicine show that our most advanced malaria vaccine candidate is having only marginal success in large-scale trials conducted in Africa,” said Professor Simon Foote, also of the Australian School of Advanced Medicine.