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The door to growing vaccine proteins in plants is officially opened with a USDA-approved veterinary product. Is the FDA prepared for human vaccines grown in plants?
In what is likely the first approval of its kind, the Department of Agriculture gave the thumbs up to a plant-derived vaccine that inoculates chickens against the lethal Newcastle disease. Dow AgroSciences, the vaccine’s manufacturer, said it was the first plant-derived vaccine approved in the world.
The USDA confirmed that this was the first plant-made vaccine approved by the department.
The Dow vaccine contains a protein from the Newcastle disease, which is grown and harvested in a plant cell culture. This process is similar to the way recombinant proteins are grown in bacterial cell lines, explained Butch Mercer, global business leader for the Animal Health division of Dow AgroSciences.
Growing the protein in a plant cell line, according to Mercer, eliminates fear of contamination from animal pathogens. Instead of introducing the Newcastle virus into the system, the vaccine contains only the protein necessary to activate a chicken’s immune system and cause it to produce antibodies against the Newcastle virus.
The cell culture could theoretically grow a plant pathogen, Mercer said. So to win approval from the USDA, Dow had to demonstrate that its production system is free of plant contaminants in order to win USDA approval.
As part of the approval process, USDA verified that the protein produced is equivalent to other Newcastle vaccines using the same protein, said spokeswoman Suzan Holl. The agency also had to expand its testing in order to evaluate the plant-cell media and culture techniques.
Growing the protein in a plant cell line, rather than whole plants, eliminates the possibility that recombinant genetic material will travel into other plants via pollen, Mercer said.
This is one of the major regulatory concerns associated with plant-made vaccines. FDA guidance requires manufacturers using bioengineered plants to demonstrate that their procedures prevent recombinant plant material from mixing with food crops, according to Paul Richards, an FDA spokesman.
“All applicable regulatory and good manufacturing practice (GMP) requirements are in place for this type of product,” Richards said.
The importance of avoiding contamination was also discussed at an informal meeting about plant-derived vaccines organized by the World Health Organization in Geneva in January 2005. The meeting concluded that existing guidelines for the developing and evaluating traditional vaccines are applicable to plant-derived vaccines, according to a WHO report.
The development may pave the way for more plant-derived vaccines for animal and eventually human diseases, according to Mercer. He predicted that the availability of plant-made vaccines would usher in a new era of immunity within the next 20 years. The company is already working on other plant-made products for birds, horses, and dogs.
The World Health Organization believes plant-made vaccines hold great promise for protecting people who live in developing countries.