Researchers scrambling to combat a virulent form of bird flu that could mutate into a form easily spread among humans should consider developing vaccines based on DNA, according to British biochemical engineers. DNA vaccines, they say, can be produced more rapidly than conventional vaccines and could possibly save thousands of lives if a global influenza outbreak occurs.
A DNA-based vaccine could be a potent weapon against this emerging threat, particularly if enough conventional vaccine isn't available, according to Peter Dunnill, DSc., and his colleagues at University College London. However, they caution that any DNA vaccine should only be used as needed to slow the spread of the disease because the technique is largely untested in humans. The analysis appears in the November-December issue of the journal Biotechnology Progress, a co-publication of the American Chemical Society and the American Institutes of Chemical Engineers.
The avian virus, H5N1, has spread among birds throughout Southeast Asia and has been recently detected in Eastern Europe. The virus has killed more than 60 people in Asia since 2003 and forced the slaughter of millions of birds. There are no confirmed cases of human-to-human transmission of this flu, but that could change as the virus continues to mutate, Dunnill says.
If that occurs, current production facilities are unlikely to meet global demands for conventional vaccines in time to avert a pandemic, Dunnill says. But it might be possible to quickly produce a DNA vaccine by adapting the manufacturing processes of selected biopharmaceutical and antibiotic plants in countries such as the United States, China and India.
Current vaccine production facilities not only couldn't meet demand fast enough avert a pandemic. If a pandemic happens current production capacity will not be able to make enough vaccine for the industrialized countries for a year or two. For the whole world production of suffcient vaccine might take much longer. Just how big a hole we'd be in would depend on the size of the antigen doses needed in a vaccine against a pandemic influenza strain. But the egg-based method currently used for making influenza vaccine probably couldn't yield enough vaccine for the whole world for 2 or 3 years. Hence the need for faster and more easily scalable methods for making vaccine.
"A DNA vaccine is not a panacea, however it could be useful if the situation gets out of hand," Dunnill says. "But if we're going to try it, we need to move. You can't expect to walk into a production facility, hand over the instructions, and expect them to make it on the spot. It's going to take some weeks, and we really don't know how much time we have."
A DNA vaccine could be produced in as little as two or three weeks, Dunnill says. To do it, scientists would create a "loop" of DNA that contains the construction plans for a protein on the outer surface of the H5N1 virus. When that DNA is injected into cells, it would quickly reproduce the protein and trigger immunization in much the same way as a conventional vaccine.
In contrast, producing conventional vaccines from viruses incubated in fertilized eggs can take up to six months, which is too long to effectively prevent an influenza pandemic, Dunnill says.
Although no commercial influenza DNA vaccine is currently available, these vaccines have worked well in animals. However, human trials are still in the early stages so the safety and efficacy of these vaccines isn't fully established in people. But these trials could be accelerated, Dunnill says, particularly if the H5N1 virus eventually causes large numbers of human deaths and out paces the supply of conventional vaccine. In the worst case scenario, he suggests, using a DNA vaccine could be a "stop-gap" measure until enough conventional vaccine is available to corral the pandemic.
Researchers at Cardiff University have discovered a means of delivering DNA directly into skin cells, allowing it to be spread efficiently throughout the body.
The breakthrough could lead to mass immunisation campaigns being carried out by post. Patients would be able to administer the vaccine themselves by pressing a silicon chip embedded with 400 microscopic needles onto the back of their hand for a few seconds.
The new micro-needles are long enough to penetrate the skin but not to reach pain receptors.
They were designed to introduce a DNA vaccination directly into skin cells.
SAN DIEGO, Sept. 22 /PRNewswire-FirstCall/ -- Vical Incorporated (Nasdaq: VICL) today announced that it has been awarded funding for a one-year, $0.5 million project for the Defense Advanced Research Projects Agency (DARPA), of the U.S. Department of Defense. The award will fund feasibility studies of a new approach for rapidly manufacturing large quantities of DNA vaccines.
Conventional vaccine development and manufacturing methods require years of effort after the emergence of a new pathogen for production of even a single dose for testing. Current DNA vaccine development and manufacturing processes allow initial production of vaccines in as little as three months after selection of a gene sequence associated with a pathogen, but quantities are limited by the batch-processing capacity of available manufacturing equipment. Vical intends to use the funding to evaluate new methods that would dramatically reduce the manufacturing time and increase yields, allowing production of millions of doses in a matter of weeks.
French vaccine maker Sanofi-Aventis received a $97 million dollar contract from the US Department of Health and Human Services in April 2005 to develop a non-egg cell-based method of making vaccine in infected cells in large stainless steel vats. A number of other companies are also pursuing cell-based and DNA-based methods for rapidly scaling up vaccine production.
Sanofi is the first company to be awarded a U.S. government contract for developing a new method of vaccine production, but it is not the only drug maker experimenting with alternate methods. Crucell, which works on cell-based and DNA-based methods of vaccine production, has also licensed its technology to British drug maker GlaxoSmithKline (down $0.51 to $50.02, Research) and Swiss drug maker Roche (up $0.22 to $144.18, Research), according to Bernstein analyst Gbola Amusa, who projected that a non-egg production method could be on the market by 2008. PowderMed, a privately-held British company, is also developing DNA-based methods for vaccine production, while Philadelphia-based Hemispherx Biopharma (down $0.11 to $2.21, Research) is working on a cell-based method.
Acceleration of research and development of more easily scalable and rapid methods for making vaccine ought to be the top priority for preparations against an H5N1 avian flu pandemic. The technology developed will be useful for any flu pandemic and also for producing vaccines against a large range of other diseases.
By Randall Parker at 2005 October 22 12:46 AM Pandemic Vaccines | TrackBackIt would be embarrassing if the FDA prevented use of experimental vaccines in the USA, leading the millions of deaths, while someone like China went full speed ahead and protected themselves.
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