Unlucky. a new study suggests that a random twist in the genetic code can protect against malaria.
Every year about a million people are killed by malaria. But even in countries where the disease takes a heavy toll, new research finds, the risk may vary: A subtle difference in a single gene can reduce the risk of developing a fatal case of malaria to nearly 0% in people who have already been infected.
Mutation of the gene causes people to ratchet up the production of nitric oxide (NO) gas, which plays a role in a variety of physiological processes. Previous studies with rodents have found that NO can guard against malaria and other diseases, but nobody knew if it had the same protective effect in humans.
Looking for an answer, a team led by hematologist Brice Weinberg of Veterans Affairs and Duke University Medical Centers in Durham, North Carolina, sampled DNA from 185 Tanzanian children. All had been exposed to malaria, and 47 had remained healthy. The researchers studied mutations in and around the gene encoding inducible nitric oxide synthase (NOS2), the enzyme that makes NO. A subtle mutation in the promoter region of the gene NOS2 - its DNA-switch - turned up most often in healthy children than sick. Children with the mutation had higher than normal levels of NO in blood and urine, suggesting that the gas could be protected.
The team then analyzed DNA samples and clinical data from a Centre 5 years for Disease Control and Prevention study of 1106 children in Kenya. They again found that the mutation in the NOS2 promoter was protective. "Overall, the mutation reduces the risk of severe malaria by 88% in Tanzania and 75% in Kenya," says molecular geneticist Maurine Hobbs of the University of Utah in Salt Lake City, a co-author of the study, which appears in the November issue 9 of the Lancet . Exactly how nO protects is not yet clear.
"the story told in this study is very attractive and logic, "said Brian Greenwood clinical immunologist at the London School of Hygiene & Tropical Medicine in the UK. This is not the first mutation thought to protect against malaria (sickle cell anemia is also, for example), he said, but "this study is one of the more compelling because they have demonstrated a link between genetics , NO production, and clinical status. "
related sites
Weinberg's website
Greenwood website
information against malaria Centers for Disease Control and Prevention
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