Genetically Engineered Vaccine for West Nile Fever

A team of US government researchers has developed a hybrid vaccine that protects mice from West Nile virus (WNV) infection. Their work was reported in the March 5, 2002, issue of the Proceedings of the National Academy of Sciences.

The vaccine consists of a weakened, or attenuated, combination of two viruses formed by removing key genes from dengue virus and replacing them with WNV genes. Both WNV and dengue virus are flaviviruses, a group of tick- and mosquito-borne microbes that also includes the viruses that cause yellow fever, St. Louis encephalitis, and other illnesses.

The matrix for the vaccine is a genetically engineered dengue virus. This virus does not attack the central nervous system during natural infection, and the modified virus had been shown previously to be safe for humans. By adding selected WNV genes to this base the researchers created a hybrid virus that when injected into mice was able to stimulate strong anti-WNV immune responses, even following a single dose of the vaccine. All of the mice immunized with the hybrid vaccine were protected against subsequent challenge with virulent WNV.

Tests of the vaccine in monkeys will begin next month, with human trials expected in late 2002. The research team included scientists from the National Institute of Allergy and Infectious Diseases (NIAID, Washington, DC, USA; www.niaid.nih.gov) and Walter Reed Army Institute of Research (Silver Spring, MD, USA; http://wrair-www.army.mil)

"We must remain vigilant and act quickly if we are to keep ahead of emerging and re-emerging infectious agents such as West Nile virus,” said NIAID Director Anthony S. Fauci, M.D. "Disease-causing microbes will continue to adapt and continue to thrive, so we cannot let down our guard.”