Tuesday, October 03, 2006

New Approach Could Speed Creation of Flu Vaccines

(HealthDay News) -- Scientists are reporting a potentially better and faster method of producing flu vaccines both for the regular seasonal flu and, more immediately, for the much-discussed avian flu.
The technique, called reverse genetics, uses cultured kidney cells from monkeys to cultivate the proteins needed for the vaccine. The old system, which the study authors described as "cumbersome," grows the flu virus in eggs.
"It's the difference between a Cuisinart and chopping your own celery," said Dr. Donald J. Kennedy, professor of internal medicine and infectious diseases at St. Louis University. "It's today's computers versus 20 years ago. Will they both compute? Will one take forever and be huge? Yes."
Kennedy was not involved in the study, which appears in this week's issue of the Proceedings of the National Academy of Sciences.
The senior author of the study is Dr. Yoshihiro Kawaoka, a professor of virology at the University of Wisconsin-Madison School of Veterinary Medicine.
Many people believe the existing system for making flu vaccine is impossibly antiquated. That system grows the flu virus in fertilized chicken eggs. Technicians then take the virus from the eggs and make it inactive. The inactivated virus forms the basis of the flu shots millions of people receive each year.
"This is a process that takes quite some time and the yield of protein is not great," Kennedy explained.
Antigens destined for inclusion in the vaccine are selected around January and the vaccine is not ready until about August, in time for each approaching flu season.
Because the circulating regular flu virus changes every year, a new vaccine needs to be made every year. "Sometimes we get a very good match and the vaccine is very good and sometimes it's a less-than-ideal match," Kennedy said.
With the new reverse genetics method, the necessary proteins or antigens from the flu virus can be produced in tissue cell cultures.
"It's much more rapid, much more efficient," Kennedy said. "Instead of the old cumbersome way with a low yield and more expense, this technology can generate large amounts of these proteins much easier."
He likened the advance to one that took place with the hepatitis B vaccine. When that vaccine first came out in the mid 1970s, researchers had to find infected individuals, collect their blood, purify it and then make the vaccine.
In the 1980s, scientists discovered a way to insert the genetic material for the hepatitis B proteins into yeast cells and grow it as if they were making beer.
The new method for flu vaccine represents a similar quantum leap, Kennedy said.
The production system for influenza vaccine has lately become a much bigger issue on national agendas.
For one thing, it is vital to protect people against seasonal human influenza, which claims 36,000 or more lives each year in the United States alone.
Last year, supplies to the United States were cut in half when the Chiron Corp.'s production plant outside Liverpool, England, experienced contamination problems.
But the issue of vaccine production has taken on more urgency in recent months because of outbreaks of avian flu that have now spread beyond Southeast Asia. Although that virus has not yet acquired the ability to spread quickly from human to human, some 65 people have died, most often after exposure to poultry or other infected birds.
Experts worry that the avian virus, H5N1, could still gather the ability to skip easily from human to human, resulting in a pandemic that could claim millions, rather than thousands, of lives.
"If we get a new pandemic strain, the vaccine will be unmatched," Kennedy said. "That's the catastrophe. If there's a big shift, the flu shot won't be good for the new flu strain."
The new system might circumvent this problem. "Based on this technology, when somebody decides what flu antigen we need in a vaccine, it would be able to be produced much more rapidly and in higher quantities," Kennedy said.
People involved in the traditional method objected to the term "cumbersome," but acknowledged that reverse genetics was probably the only hope for a vaccine against the avian flu.
"It's more important for H5N1 because they had to get rid of the virulence," said Doris Bucher, associate professor of microbiology and immunology at New York Medical College in Valhalla, N.Y. By that, she meant the researchers would be able to create a bird flu vaccine using certain genetic material that would pose less of a health risk to people. In this case, reverse genetics might be the "only way," she added.
Bucher's lab produces the starting strain used by flu vaccine manufacturers worldwide. This year, it produced the H3N2 component of the vaccine, the only lab in the world to do so.
Bucher denied that the existing approach was outdated. "They [the designers of the new vaccine method] have simplified the approach," Bucher acknowledged. "But our approach is Darwinian while theirs is more Intelligent Design. They have one gene, we select the best of 64."
Yet the new technology could soon be ready for widespread use, raising the possibility that it would supplant the old system.
"This is using newer biologic technology in ways that it hasn't been utilized before, and obviously there are going to be discussions," Kennedy said. "Just like the car is safer today than it was 25 years ago, this is a better system. This is another biotech advancement in terms of producing the proteins that are necessary for the vaccine. It won't change the whole concept of the vaccination, but it will be an alternative method that would be faster and less expensive."
More information
The U.S. Centers for Disease Control and Prevention has more on the flu.

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