WEDNESDAY, April 11, 2007 (HealthDay News) -- Using genetically engineered plants as a factory, scientists say they have produced a protein that could help them create an effective and safe smallpox vaccine.
The findings are preliminary, since the protein has only been tested against smallpox in mice. But plants show plenty of promise as a manufacturing center for drugs, said study co-author Dr. Hilary Koprowski, the developer of the live polio vaccine.
"In 10 years time, the (smallpox) vaccine should all be made in plants," said Koprowski, head of the Center for Neurovirology at Thomas Jefferson University in Philadelphia. "There really is no downside so far."
Armed with a vaccine, doctors and scientists eliminated smallpox from the world's population more than three decades ago. But the virus remains in research laboratories, and smallpox is considered a major bioterrorism threat.
The smallpox vaccine is far from perfect, however. It contains a weakened form of a germ related to the smallpox virus; as a result, some people -- especially those with weakened immune systems -- fall ill and die after they're vaccinated.
"The current vaccine is from the 1800s, and is one of the most dangerous vaccines ever used for mass population use," said Dr. Brian L. Strom, director of the Center for Clinical Epidemiology and Biostatistics at the University of Pennsylvania Health System.
"Its risks were easily acceptable compared to those of a disease which had a 30 percent fatality rate," Strom said. "Its risks are much more problematic in a world which has not seen a case of smallpox since around 1970. If we are to consider vaccinating people against this disease, we need a new vaccine using modern technology."
In their study, published in this week's issue of the Proceedings of the National Academy of Sciences, Koprowski and his colleagues report that they were able to coax tobacco and collard plants to create a protein that could be used in a vaccine. When tested in mice, the protein produced from collard greens appeared to protect the animals from smallpox infection.
Genetically engineered plants have been used before to develop drugs. According to Koprowski, plants have an "enormous advantage" compared to other types of vaccine production. For one, he said, the vaccines can be eaten or taken through the nose instead of injected.
But not everyone agrees on the need for a new smallpox vaccine. Dr. Thomas Mack, professor of preventive medicine at the University of Southern California, said that while the existing vaccine does cause complications, "it only has a significant number if you're going to do mass vaccinations. That, in my opinion, would be unwarranted in any circumstance I'm aware of."
As for the development of vaccines in plants, Mack said any new smallpox vaccine could not be fully tested in humans because of the ethical problems of exposing people to the disease.
To learn more about the smallpox vaccine, visit the U.S. Centers for Disease Control and Prevention.