HAVING two copies of a mutant gene for haemoglobin almost eliminates your
risk of developing malaria, say Italian researchers. One in five people they
studied in the West African country of Burkina Faso has at least one copy, which
they predict will spread through the population.
David Modiano and his colleagues at the University of Rome examined 4348
people鈥�835 with the disease and 3513 without. They found that those who
were free of the disease were much more likely to carry the HbC variant
of the gene for haemoglobin, the oxygen-carrying protein that gives blood its
red colour. The results suggest that having one copy of the HbC gene
makes you 29 per cent less likely to get malaria, while receiving a copy from
both parents cuts your risk by a whopping 93 per cent.
The mutation doesn鈥檛 stop you being infected with plasmodium, the
single-celled parasite that causes malaria. Rather, HbC stops the
parasite from gaining enough of a hold to cause any symptoms. 鈥淧reviously,
people had looked at how HbC affects infection, but not at the
development of clinical malaria,鈥� says Modiano.
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As yet, how HbC blocks the symptoms isn鈥檛 clear. But the researchers
hope that if they can work out the molecular basis for the protection the
HbC gene provides, it will lead to new treatments or even a vaccine.
Malaria still afflicts half a billion people each year and causes a million
deaths, and it is becoming resistant to many drugs.
The study shows that the mutation confers major protection against malaria,
says Geoffrey Pasvol at the Wellcome Centre for Clinical Tropical Medicine at
Imperial College, London. He predicts that in areas infested with malaria, the
gene is likely to spread rapidly through the human population over the next
couple of generations.
The mutation will remind many people of the classroom favourite, sickle-cell
anaemia, which is also caused by a mutation in the haemoglobin gene. Having one
mutated copy confers some immunity to the malarial parasite. However, having two
mutated copies causes life-threatening disease. 鈥淚n contrast, we see a very mild
anaemia in people with two copies of the HbC gene,鈥� says Modiano.