The black genie

Monday 31 December 2001

Gene encoding a mutant form of haemoglobin provides Africans protection from malaria

Africans may be deprived of a lot many things, but some of them are gifted with a gene that provides protection against malaria. A survey done by an international team of researchers recently revealed that every tenth person in Burkina Faso has a gene that provides defence against malaria. The gene encodes a mutant form of haemoglobin called hbc. People with hbc get infected with malaria, but somehow the mutations stop the infection from causing severe symptoms such as anaemia and coma (www.nature.com , November 21, 2001). People with one copy of the gene have 26 per cent less chance to get sick with malaria. And for those who have two copies -- one from the father and the other from the mother -- the risk gets reduced by an unprecedented 93 per cent!

"The mutation is very protective against severe malaria," says David Modiano, a parasitologist at the University of Rome, who led the research. "Haemoglobin mutations have arisen under selective pressure from malaria," says Thomas Wellems of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, usa. "It's nature's way of telling us which factors protect against the disease." Researchers have for long known that many other forms of haemoglobin hinder malaria. A good example is a mutation called hbs, which is common throughout Africa. But unlike hbc, people with two copies of hbs die young from sickle-cell anaemia.

Researchers opine that hbc has protective affects for about 50 years. However, Modiano believes that two copies of the gene are needed for full protection. Wellems disagrees. He thinks the level of protection hbc or hbs provide depends more on a person's other genes.

However, for now, the finding of the hbc mutation has not much to offer to researchers, as they were unable to crack the mystery of why and how the mutant wins its battle against malaria. They just know that the hbs and hbc mutations occur in exactly the same place in the haemoglobin molecule, suggesting the mechanism could well be universal -- a tantalising prospect for developing effective vaccines and other anti-malarial drugs. "If we can nail the protective mechanism, maybe we can come up with that target," says Wellems.

Moreover, hbc is not found throughout sub-Saharan Africa where malaria is endemic. The reason behind this phenomenon, Modiano speculates, is that unlike hbs, the mutation will take a long time to spread and establish itself throughout Africa because it is rare outside the Mossi ethnic group.

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