2006-05-22-Combo Vaccines Developed Against Bird FluUnderstanding Avian Influenza
2006-05-22-Combo Vaccines Developed Against Bird Flu
Scientists are reporting an effective and inexpensive way to vaccinate poultry against avian flu and, hopefully, prevent its spread to humans.
Researchers in Germany and New York City have independently attached the gene for avian flu virus onto an existing, widely used vaccine against a virus that causes another bird infection called Newcastle disease.
"This is a very cheap vaccine that can be added to water or even sprayed," said Peter Palese, chairman of the department of microbiology at Mount Sinai School of Medicine in New York City, and lead author of one report. "We have grafted onto that a flu virus, using genetic engineering. Thereby one can now use the same vaccine for Newcastle disease that also has protection against [avian] influenza."
The same technique was reported by a group of researchers at the Federal Research Institute for Animal Health in Riems, Germany.
"We have tried our vaccine in chickens, and it works very well," Palese said, adding that Mount Sinai is negotiating with drug companies about mass production of the vaccine.
The Newcastle disease virus that now is in use costs less than a penny a bird, and the genetically engineered version to protect against avian flu should not cost much more, Palese said.
"This is a major breakthrough in terms of protecting chickens," he said.
The newly reported achievement is part of a major international effort to avoid a pandemic of bird flu in humans. Several hundred human cases -- including an estimated 115 deaths -- have been reported, and all the victims had been in close contact with infected birds. The fear is that the bird flu virus might mutate so it could spread easily from person to person.
Dutch researchers demonstrated last year a vaccine's ability to prevent the spread of infection in birds. They reported in November that two different vaccines were each able to block transmission of the virus. But their vaccines were designed for the H7N7 strain, not the H5N1 strain that is thought to pose the risk to humans.
The two new genetically engineered vaccines protect against the H5N1 strain.
Joseph Giambrone, a professor of poultry science at Auburn University, called the new vaccines "a solution, but not the whole solution."
"It's a good one, because you also get protection against Newcastle disease," he said. "But you probably would have to vaccinate the birds more than once, because you only get partial protection the first time."
The reason for the partial response is that the immune systems of young birds carry antibodies from their mothers that reduce the response to the vaccine, Giambrone said.
One encouraging development in the campaign to thwart an avian flu pandemic in humans is that studies of birds in the wild show they aren't spreading the virus, as has been feared, Giambrone said. International health officials reported this month that migratory birds that flew south to Africa and then back to Europe did not spread the virus during their annual journey.