Italian and African researchers have found the most conclusive evidence so far that a mutation in the gene for red blood cells protects against malaria. They have found the mutation to be common in West Africa, where it apparently saves countless people from death. The investigators hope the finding could lead to new drugs or a vaccine for the disease.
The malaria parasite, like us, has to eat. When it enters the bloodstream by a mosquito bite, its diet consists of hemoglobin, the red blood cell pigment that carries oxygen to all parts of the body.
Scientists have long known that a mutant form of hemoglobin known as hemoglobin S protects Africans against malaria. Unfortunately, people who carry two copies of the hemoglobin S gene, one from each parent, tend to die young from the painful blood disease, sickle cell anemia.
In the past few years, researchers have realized that another, safer version of the hemoglobin, known as hemoglobin C, also protects against malaria. But efforts to determine how well it does the job have yielded conflicting results.
A new study conducted in Burkina Faso finds the protection significant.
"Our study represents a solid demonstration of the protective role against malaria of hemoglobin C, which is frequent in West Africa," explains Dr. David Modiano of the University of Rome "La Sapienza." His study finds that one in every 10 people in Burkina Faso has the C mutation. He led a study of 4300 Burkinabe people and discovered that the level of protection it confers depends on whether a person has one or two copies of the gene.
"If you have one copy of the mutated gene, there is a 29 percent reduction in risk of clinical malaria,"he says, "whereas if you have two copies, you have a 93 percent reduction in risk."
This is similar to the malaria protection that hemoglobin S offers, but without the deadly threat of sickle cell anemia.
U.S. National Institutes of Health researcher Thomas Wellems has also found hemoglobin C protective against malaria. His finding came in a study last year in Mali. He calls the latest research important.
"Before the explorations in Mali and now Burkina Faso, the feeling in the field was that maybe hemoglobin C does protect, but there was no evidence for it. This paper really clinches the evidence," says Mr. Wellems.
The Burkina Faso study actually shows a much stronger protective role for hemoglobin C against malaria than Mr. Wellem's study did. His work in Mali showed that the mutation did not prevent infection, but did fend off the severe form of the disease. In contrast, the Burkina Faso study shows that the gene mutation prevents all malaria.
Mr. Wellems believes the difference in outcome could be the result of differences in the immune systems of the two populations.
"Perhaps the protection depends on the individual, depends on their innate level of immunity. Is somehow the C hemoglobin giving protection, say, by giving a boost to the immunity? This is one major hypothesis for the protection by sickle hemoglobin. It is that hypothesis we want to pursue," he explains.
Thomas Wellems and David Modiano in Rome say that when scientists determine exactly how the hemoglobin variations protect against malaria, the lesson can be applied to treating and preventing the disease.
"At present, there is no direct implication of these results in the control of the disease. But when the mechanism of protection will be described, it is possible that it can help in the development of vaccines and/or drugs," says Dr. Modiano.
His work involved co-investigators from Burkina Faso's Health Ministry, the Saint Camille Medical Center, and the Yalgado Ouedraogo National Hospital Center in Ouagadougou. It appears in the journal Nature.