Arntzen added that he was pleasantly surprised that the vaccine apparently withstood the stomach's acids and enzymes. This was an indication that the potato tissue surrounding the vaccine was able to protect it as it journeyed through the stomach to the large and small intestine, where specialized cells initiate immune responses.
Carol Tacket is a professor of medicine at the University of Maryland School of Medicine's Center for Vaccine Development in Baltimore. Though not part of the research team, she is interested in novel approaches to vaccination via the body's mucous membranes, such as those that line the mouth and intestines, and has been involved with the field of plant-derived vaccines. "The whole concept is pretty amazing," she said.
"It seems hard to imagine the mucosal immune system in the intestine would be able to pluck out a bit of protein in a sea of foodstuff and process it in a way for an immune response to be generated," she said.
Thanavala and colleagues are now working to match or better the success of the syringe-and-needle hepatitis B vaccine with their potato-derived version. The traditional vaccine has a success rate of about 90 percent. About 10 percent of all people, for reasons not understood, fail to respond.
"What we've shown is proof of principle that a subunit antigen can be delivered orally and can provoke an immune response. That's the first step," Thanavala said. "Now, can we make improvements to better the overall rate of response to make it a true contender of the current licensed vaccine?"
If successful, the researchers envision a plant-derived hepatitis B vaccine that could serve to boost the immune response of previously vaccinated people in countries like the U.S. And for the 60 percent of the world's children who lack the vaccine, a plant-derived version may be the solution, Arntzen said.
But before people get carried away with visions of plates of genetically modified potatoes being passed around clinics, Arntzen cautioned that the field of plant-derived vaccines has matured over the past decade.
"Initially, plant vaccines were perceived in a way that today seems rather naïve: that is, as a kind of vaccine utopia, whereby people in developing countries would be able to eat antigen-producing fruits and vegetables and be passively immunized against one or more infectious disease," Arntzen said.
Concerns about the safety of the genetically modified crops interacting with other foods and the lack of dose control have since moved researchers to focus on food-processing technologies to package measured doses of vaccine.
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