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Killer Flu Recreated to Thwart Bird Strain

Posted on: Friday, 7 October 2005, 06:01 CDT

By Charles Piller

Working with scraps of DNA preserved for nearly 80 years in the Alaskan permafrost, scientists have resurrected the virus behind one of the deadliest pandemics in human history -- the 1918 Spanish flu -- and identified key similarities with the current bird flu in Asia.

Two teams reported Wednesday that the 1918 virus had 25 to 30 separate mutations that, cumulatively, allowed it to infect humans, eventually killing as many as 50 million worldwide.

Some of those same mutations are present in the bird flu virus now circulating in Asia, the teams said, bolstering fears that a few more mutations could trigger a similar pandemic.

"Given a few molecular changes in an avian virus, it has the potential to go into a human host and raise havoc," said biologist Terrence M. Tumpey of the Centers for Disease Control and Prevention.

One important similarity between the two viruses is that both migrated to humans directly from birds, unlike other flu viruses that first require a passage through pigs or other animals, according to two studies released Wednesday by the journals Science and Nature.

Now that researchers know what kinds of changes to look for, they are better equipped to monitor the evolution of the bird-flu virus and catch a potential outbreak before it spreads, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, and CDC director Dr. Julie Gerberding at a news conference Wednesday.

If threatening genetic changes were detected in a bird-flu virus, experts said, it might be possible to block an outbreak by culling infected birds and treating patients with antiviral agents.

Fauci called the research "a milestone in the scientific approach" to combat bird flu.

Some scientists, though, have questioned the wisdom of publishing the genetic blueprint for such a deadly virus, especially since science is quickly gaining the ability to create such viruses in the laboratory from scratch.

Dr. Jeffrey K. Taubenberger of the Armed Forces Institute of Pathology in Washington pieced together the complete genetic blueprint of the 1918 virus using DNA fragments isolated from young soldiers and an Alaskan woman who died during the pandemic. Over a 10-year period, he painstakingly assembled the fragments and sent them to Tumpey, who then grew the virus and tested it in mice and cultured human tissues.

The virus has eight genes, but two of them proved to be most crucial. One, identified last year by virologist Yoshihiro Kawaoka of the University of Wisconsin, is the blueprint for hemagglutinin, the protein that allows the virus to latch onto human cells before invading them. The second is polymerase, which helps the virus replicate.

Normal flu viruses rely on enzymes in the lung cells they invade to cleave and activate the protein, allowing it to enter cells. The mutations in the 1918 gene eliminate this requirement, so that the virus can enter virtually any cell it encounters.

The current bird flu differs from the 1918 virus in that it passes from human to human only with great difficulty.

Source: Cincinnati Post

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