After just a couple of small changes to a single gene in a pandemic flu virus, it no longer passes efficiently between lab animals. That finding reveals a simple way in which avian-flu strains, such as the bird-flu strains now looming in Asia, could morph into strains that have pandemic-causing potential, say researchers.
The scientists, led by Terrence Tumpey of the Centers for Disease Control and Prevention in Atlanta, worked with a reconstructed version of the 1918-flu virus (SN: 10/8/05, p. 227: Killer Findings: Scientists piece together 1918-flu virus). The microbe caused a pandemic in 1918 and 1919. Researchers have concluded that the virus originated as an avian flu strain.
To learn how the virus might have switched from infecting birds to passing readily among people, Tumpey's team changed the components of a gene called hemagglutinin, which is known to affect flu transmission. These changes in turn altered the structure of just two of the amino acids making up the strain's hemagglutinin protein. The structural changes made the protein more like its counterpart in avian-flu strains.
When the researchers put the altered virus into ferrets, the animals got sick but didn't pass on the virus. In contrast, ferrets that got the unaltered 1918 virus readily transmitted the disease. The researchers report their findings in the Feb. 2 Science.
Tumpey says that the team will now study the same amino acids in H5N1 bird flu, the one currently considered a pandemic threat.
Terrence M. Tumpey
Division of Viral and Ricksettial Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
1600 Clifton Road, NE
Atlanta, GA 30333
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