conveying protection against HIV boosts West Nile risks

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)

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