Mutation
conveying protection against HIV boosts West Nile risks

Researchers recently discovered that a genetic mutation conferring resistance to HIV infection may carry with it an increased susceptibility to West Nile virus. WNV is transmitted to humans through mosquitoes that carry the virus.

The genetic mutation causing blood cells to lack the CCR5 receptor, one molecular doorway HIV uses to latch onto and infect cells, causes people to be less easily infected with HIV. About 1% of North American Caucasians carry two copies of the mutated gene and do not produce CCR5.

However, mice genetically engineered to lack CCR5 were especially prone to become sick and die from West Nile infection, observed Philip Murphy and colleagues at the National Institute of Allergy and Infectious Diseases.

"We wanted to know if humans lacking CCR5 might be at greater risk of the more serious complications of WNV infection," Murphy said in a statement.

In tests of blood and spinal fluid from 395 WNV-infected people in Arizona and Colorado in 2003 and 2004, researchers found 4.5% of Arizona samples and 4% of Colorado samples were from patients with two copies of the CCR5 mutation. That is four times the 1% average that should be seen in the general population. Among WNV-infected Colorado residents identifying as white, 8% had the CCR5 mutation.

This is the first genetic risk factor identified for WNV, said Elias Zerhouni, director of the National Institutes of Health. "While infection does not always lead to illness, the virus can sometimes cause serious problems, and, according to the Centers for Disease Control and Prevention, there were 102 deaths in the United States from West Nile virus infection in 2005," he said. (Reuters)