NIAID Begins Clinical Trial of West Nile Virus Vaccine

A small trial testing the safety of an experimental vaccine targeting West Nile virus (WNV) has opened at the NIH's Clinical Center in Bethesda, Md.

The vaccine, which will be tested first in 15 healthy adult volunteers, was developed for human clinical studies by researchers at the National Institute of Allergy and Infectious Diseases' Vaccine Research Center and Vical, San Diego, based on an animal vaccine tested at the Centers for Disease Control and Prevention. Vical also manufactures the experimental vaccine.

The experimental vaccine is composed of a small, circular piece of DNA - called a DNA plasmid - that contains genes that code for two key surface proteins of the West Nile virus. When the vaccine is injected into the muscle, the inner machinery of the muscle cells "reads" the DNA and converts it into two WNV proteins. Recognizing that the proteins are foreign, the muscle cells display them on their surface to alert the body's immune system - both helper T cells, which spur the production of antibodies to block the WNV from gaining entry into cells, and killer T cells, which kill WNV-infected cells outright.

Fifteen healthy volunteers between the ages of 18 and 50 will receive three injections of the DNA vaccine into the upper arm: one at the start of the trial, a second approximately four weeks later, and a third approximately four weeks after that. To help force the DNA plasmid into muscle cells, the vaccine will be administered by a needle-free injector rather than a conventional needle syringe. Volunteers will be monitored for possible symptoms or side effects as well as the body's ability to generate WNV-specific antibodies and T cells.