Experimental West Nile vaccine shows promise in lab monkeys

WASHINGTON -- A vaccine that combines key parts of two viruses has been shown to protect monkeys from West Nile virus, a mosquito-borne illness that has killed 10 Americans this year.

Scientists at the National Institute of Allergy and Infectious Diseases, or NIAID, one of the National Institutes of Health, made the vaccine by placing West Nile virus proteins into a modified virus that causes dengue fever. This created a live but weakened virus.

When injected into monkeys, the hybrid virus protected the animals from injected doses of West Nile virus. The researchers said the combined viruses crippled the West Nile virus but still caused a strong immune response against it.

In a laboratory test, the researchers injected 12 monkeys with the combined virus vaccine and injected eight other monkeys with either the West Nile virus or the dengue virus.

Six weeks later, all 20 monkeys were injected with West Nile virus. The dozen that received the combined virus vaccine developed antibodies that successfully protected the animals from the West Nile virus.

Human clinical trials with the vaccine are to begin this year, said Dr. Brian Murphy, a researcher in NIAID's Laboratory of Infectious Diseases.

"We're optimistic that our engineered virus vaccine will provide long-term immunity to West Nile virus, but the human clinical trials will give us the definitive data," Murphy said in a statement.

West Nile is spread to people through the bite of an infected mosquito. Usually the disease produces only flu-like symptoms, but some patients develop an inflammation of the brain that can be lethal. The disease is most severe among the elderly.

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NIAID: www.niaid.nih.gov