Though the swine flu scare of 2009 may have bumped the avian variety of flu from of the popular imagination, biomedical researchers certainly haven't forgotten the potential danger it poses. But researchers are constantly forced to play catch-up by following bird flu's path through the avian population and trying to track its shifting genetics. The way to finally get the jump on bird flu would be to create a weapon that works against the whole family of avian flu viruses, whatever their slight genetic quirks. And researchers led by Laurence Tiley say in Science this week that they might have found that kind of comprehensive trick: a genetic modification that seems to prevent flu from spreading in chickens. It's a decoy.
The birds carry a genetic tweak that diverts an enzyme crucial for transmitting the H5N1 strain. Although they die of the disease within days, the molecular decoy somehow impedes the virus from infecting others. [Nature]
Specifically, this genetic tweak allows the birds to create an RNA impostor. It matches up to the polymerase
enzyme the flu virus would use to replicate its genetic material, so that enzyme is attracted to the decoy, which throws off viral replication. Though the modified chickens that were infected with avian flu
died, the fact that they didn't spread the virus is a potentially huge find—once avian flu enters a chicken population it typically spreads like wildfire. Why didn't they spread the virus? The researchers write: "These data show that the TG-D5 chickens did not efficiently transmit infection to birds housed with them, but the specific mechanism underlying this effect is not known. Polymerase decoys may disrupt replication by direct binding to polymerase or indirectly by influencing the level of expression of the recently discovered, putative regulatory small viral RNA molecules." But it's also possible that the decoy somehow interferes with the packaging of the virus. But what about researchers' ubiquitous nemesis in combating flu—the viruses
' speedy evolution?
"The decoy mimics an essential part of the flu virus genome that is identical for all strains of influenza A," said Tiley, who co-authored the new study. The RNA that the gene generates is so general that it should work against all forms of the flu—year after year—rather than needing to be reconfigured like the influenza vaccines currently administered to chicken flocks, the researchers concluded. [Scientific American]
While a virus could overcome vaccination with relatively few genetic changes, it would have to turn over all eight sections of its genome to avoid the decoy approach.
That's exciting news for chicken farmers who are trying to protect their flocks from a deadly virus, but it could also open the door to genetically engineering disease resistance into a host of other animals. "Genetic modification could be more effective than vaccination," says Helen Sang, a geneticist at the Roslin Institute at the University of Edinburgh and a co-author of the Science paper. "You wouldn't need to change the way you tackle each disease." [TIME]
You won't see this technology tomorrow, though—in addition to being tested and refined for commercial development (and becoming affordable), it would also need to clear the political and research hurdles set up for genetically modified organisms. Related Content: DISCOVER: The Evolution of Swine Flu (Video)
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Image: flickr / StevenW.