Yale Researchers Develop First Vaccine for West Nile Virus Tested Successfully in Animal Model of the Disease

Yale scientists have successfully immunized mice against West Nile virus, raising the possibility of developing a vaccine for humans against the potentially fatal, mosquito-borne infection.

Although there have been about 10 virus-related deaths reported to date in the United States, West Nile virus is considered an emerging disease, according to Erol Fikrig, M.D., associate professor of medicine and in the Department of Epidemiology and Public Health at Yale School of Medicine, who directed the study. “Its seriousness as a public health threat is not fully known yet,” he said. “That should become apparent over the next two to three years. If the vaccine proves necessary, its development will be valuable.”

Results of the study were published online in the Journal of Immunology on October 23 and appeared in the November 1 print issue.

West Nile virus was first identified in Uganda in 1937 and has since infected people in many other parts of the world. It was seen for the first time in humans in the U.S. in the New York City area in 1999. Sporadic cases have since appeared around the Northeast and in the South and Midwest. The virus, which infects birds as well as humans, spreads through mosquito bites primarily in warm weather months.

There is currently no cure for West Nile virus, although infection does not generally cause serious consequences. Elderly patients, however, can develop fatal encephalitis, a central nervous system infection.

Fikrig, Tian Wang, a post-doctoral fellow in his laboratory, and other Yale colleagues worked with John F. Anderson and associates from the Connecticut Agricultural Experiment Station in New Haven to isolate the virus found in an infected bird. They genetically engineered a protein in the virus, which they then injected into uninfected mice. Immunization with the vaccine provided complete protection for the animals against West Nile virus.

Diagnosis of West Nile virus can be difficult using current methods. The protein used to make the vaccine could also potentially be employed to develop a diagnostic test.

Other participants in the study included Louis A. Magnarelli of the Conecticut Agricultural Experiment Station, Susan J. Wong of the New York State Department of Health, and Raymond A. Koski of L2 Diagnostics, Inc.

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Karen N. Peart: karen.peart@yale.edu, 203-432-1326