Progress made on West Nile

Medicine & Science

October 11, 2004|By Esther Landhuis | Esther Landhuis,KNIGHT RIDDER/TRIBUNE

Researchers are making headway developing West Nile virus treatments and vaccines. The question is whether remedies will be effective enough to get to market while demand exists.

At least one vaccine and two treatments are undergoing human clinical trials, but none will be available until 2007 at the earliest. Meanwhile, the seasonal epidemics cost the United States at least $140 million annually, said a recent Centers for Disease Control and Prevention study that tracked medical costs, productivity losses and government-agency expenses from the mosquito-borne virus.

Infected individuals are thought to be immune for life, said Carol Glaser, a viral disease expert with the Department of Health Services in California, which was hit hard this year.

A horse vaccine for West Nile virus has been available for several years, but developers of a human version face a number of additional requirements to earn approval by the Food and Drug Administration.

To date, the only vaccine candidate in human trials is produced by Acambis, a British company with its U.S. headquarters in Cambridge, Mass. A single shot of this vaccine - created by swapping parts of the closely related yellow fever vaccine with proteins from the West Nile virus - seems to offer long-term protection in monkeys, mice and hamsters.

In human trials completed this spring, the vaccine induced West Nile-specific antibodies in all 15 patients. Scientists believe it will match the 10-year immunity of the yellow fever vaccine.

Government researchers are also designing a vaccine, using another related pathogen - the dengue virus - as a backbone to carry West Nile virus genes. Human testing is expected to begin before the year's end.

Acambis vaccine

The Acambis vaccine could gain FDA approval by 2008 if remaining trials go smoothly, said chief scientific officer Thomas Monath.

But some worry that this might be too late. Shortly before GlaxoSmithKline released the nation's only vaccine for Lyme disease in 1999, CDC officials predicted it would be a lucrative therapeutic. But in 2002 - when the deer-tick-borne disease sickened more than 23,000 nationwide - the vaccine was pulled off the market after poor sales.

Some attribute the failure to the disease's waning novelty, while others suspect consumers also were put off by the Lyme disease vaccine's numerous caveats. It was only 80 percent effective, wasn't approved for children and required three shots.

Since West Nile activity is sporadic and geographically unpredictable, some think treatments are a more practical solution than vaccines.

After an outbreak in the Middle East in the late 1990s, Omrix, an Israeli company, designed a treatment based on antibodies from patients who had been exposed to the virus.

The drug, which purportedly locks onto the virus and inactivates it, has been used to treat three or four Israeli patients and one in Washington. But scientists aren't sure whether the treatment worked, since West Nile symptoms can subside on their own. So the National Institutes of Health is conducting clinical trials at 68 U.S. sites.

NIH trials

If these pass muster, the FDA would demand a larger study involving hundreds of patients at hundreds of sites.

"It could be three or four years before we have a licensed therapeutic," said Dr. Rich Whitley, an infectious-disease specialist at the University of Alabama at Birmingham and head of the Omrix study.

Scientists at Portland, Ore.-based AVI BioPharma have a different strategy for treating West Nile disease. It uses a synthetic compound that binds to key viral genetic sequences, preventing their translation into proteins.

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