Is vaccine finally in the offing?

• Position: West Nile Virus

West Nile virus evades the body's defenses by blocking immune signaling by a protein receptor, a finding that could pave the way for a vaccine to protect against North American strains of the disease, report researchers from the University of Texas Southwestern Medical Center, Dallas.

Scientists discovered the receptor's key role in controlling West Nile infection by conducting a study that compares the genetics of an illnesscausing Texas strain of the virus to a harmless African strain. The Texas strain can inflict illness because it blocks the signaling activity of a protein receptor called the interferon alpha/beta receptor (IFNAR), disrupting a cell's ability to direct the immune system to fight off the virus. The benign African strain does not block IFNAR activity, so the immune system renders it harmless.

"We now hope to harness the African strain as the basis for West Nile vaccine studies," indicates Michael Gale, associate professor of microbiology. "The virus has spread across the country and infected more than 2,100 U.S. residents [last] year alone, so we have to learn how to deal with it."

West Nile virus, which is transmitted by mosquito bite, arrived in the U.S. in 1999 and has become an epidemic that flares in the summer and lasts into fall. Infection causes mild flu-like symptoms in most...