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Scientists seek new ways to counter the threat of a bird flu pandemic

CLEVELAND—Health scientists and engineers are racing to find new ways to produce a vaccine that will protect people from the threat of a worldwide bird-flu pandemic.

They're working with plants, insects and bacteria that they hope can churn out huge quantities of vaccine more efficiently than the present, agonizingly slow system of using millions of chicken eggs.

An adequate supply of vaccine for the lethal H5N1 flu virus won't be available for years, experts from seven countries, 44 universities and 60 biotechnology companies agreed at a conference this week in Cleveland sponsored by the National Academy of Sciences at Case Western Reserve University.

"We're not ready," said Bruce Gellin, the director of the National Vaccine Program Office at the Department of Health and Human Services. "If it happens tomorrow or next year, we're in trouble. It's a sobering picture."

Klaus Stohr, the head of the World Health Organization Influenza Team, said that one dose of a safe, effective vaccine for H5N1 was "going to be much more valuable than diamonds."

In the last three years, bird flu—also known as avian flu—has killed millions of birds, a small number of mammals and 109 humans in Asia, Europe and Africa. So far, it's overwhelmingly a bird disease, but it's mutating rapidly and might change into a form that could pass among humans.

The 2006 spring bird-migration season is just beginning, raising fears that the virus could reach the Western Hemisphere this year.

"It's routine for a virus to cross hemispheres from Russia to Canada via the Arctic," said Dr. Michael Callahan, the manager of avian influenza surveillance for the Department of State.

Ducks and other wild birds can carry a virus along an established "flyway" through Alaska to Washington state, Oregon, California, Arizona and Mexico. A sick or dead duck could be a warning signal.

About 30 potential vaccines are being tested for safety and effectiveness in the United States and Europe, but the results have been disappointing, Stohr said.

The tests show that very high doses of vaccine—and at least two shots—are needed to prevent infection, which means much greater quantities will be necessary, far more than can be produced by current technology.

There will be no breakthrough this year, Stohr said. "It will take six years to have enough vaccine for 20 percent of the world's population. It may take eight to 10 years to solve the problem."

Furthermore, the virus keeps changing, so a vaccine developed for one type of flu may not work against another variant. The H5N1 type that began in Asia already has split into two main branches.

"They are different enough that we may need two stockpiles of vaccine," said James Matthews, the senior science-policy director at Sanofi Pasteur, a vaccine manufacturer in Swiftwater, Pa.

To meet the challenge, scientists are trying to grow vaccines in various kinds of cells, which they multiply in giant vats, instead of in eggs. Yeast, tobacco leaf, soybeans and duckweed cell cultures avoid many of the problems encountered with eggs, but that still doesn't speed up the process much.

"You can't make cells divide any faster," said Dr. Patrick Scannon, the chief scientist at Xoma Ltd., a biotechnology firm in Berkeley, Calif.

Researchers also are seeking novel methods to deliver vaccine to patients without the necessity of refrigeration and sterile needles, which can pose serious obstacles in many parts of the world.

"Theoretically you could have a vaccine in a tomato," said Alan Shaw, the president of VacInnate, a biotechnology company in New Haven, Conn. Eating the tomato would provide additional protection after the first inoculation, like a booster shot, he said.

Another idea is to insert the genes for the virus in the DNA of a bacterial cell and then inject it into a human cell. Once there, the DNA generates the proteins that block infection.

"You make the vaccine all by yourself," Shaw said.

Given the lack of an adequate vaccine, experts at the conference stressed the importance of a strong surveillance system to detect a local flu outbreak promptly, before it can spread into a pandemic. Such a system helped limit the SARS epidemic, which killed 774 people in Canada and Asia in 2003.

"We need a computerized system to collect events and spot clusters," said Roy Anderson, an epidemiologist at London's Imperial College. "Two days is the critical threshold for a quarantine to control H5N1."

"The key to our survival in the next two or three years is good surveillance," Shaw said.

"We need to be on a wartime footing," Gellin told the conference. "Innovation comes out of crisis."



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(c) 2006, Knight Ridder/Tribune Information Services.

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