July 5, 2000
For first time scientists trigger human immunity to a virus using a plant-based, edible vaccine
ITHACA, N.Y. -- Human immunity to a virus has been triggered for the first time by a vaccine genetically engineered into a potato. The specific virus involved is the pervasive Norwalk virus -- the leading cause of food-borne illness in the United States and much of the developed world.
Scientists from the Boyce Thompson Institute (BTI) for Plant Research at Cornell University and the University of Maryland School of Medicine at Baltimore report on the success of the first human clinical trials of the plant-based vaccine in the latest issue (July 2000) of the Journal of Infectious Diseases.
"This plant-based vaccine could be the first one readily accepted in the developed world. It's very exciting," says Charles Arntzen, president and chief executive of BTI. "It's likely that in the United States, this Norwalk virus vaccine could easily be the first licensed product based on our plant biology research."
Arntzen and his colleagues previously conducted a successful clinical trial in triggering immune response in humans to the bacterium Escherichia coli through a transgenic potato vaccine. The result were published in Nature Medicine in 1998.
The first of three stages of human clinical trials for the Norwalk virus plant-based vaccine began in April 1999 and was conducted at the Center for Vaccine Development at the University of Maryland. Volunteers ate two or three doses of BTI-developed transgenic, raw potato containing the viral antigen. Overall, 19 of the 20 volunteers (95 percent) who ate the transgenic potatoes developed an immune response to the Norwalk virus. Before eating the potatoes, the volunteers were tested for Norwalk antibodies, and all indicated previous exposure to the virus.
The Centers for Disease Control and Prevention in Atlanta estimates that more than 23 million people in the United States are infected annually by the Norwalk virus, or by Norwalk-like viruses. That compares to 79,000 cases resulting from E. coli contamination, 2,500 cases of listeriosis and 1.4 million cases of illness from salmonella.
Norwalk virus received its name in 1968 when nearly 100 students in a Norwalk, Ohio, school simultaneously came down with nausea, vomiting, stomach cramps and diarrhea. It was not until four years later that scientists realized the pathogen was a virus.
Until 1990, scientists and doctors routinely blamed common food-borne disease symptoms on bacterial pathogens. Microbiologist Mary K. Estes and others at the Baylor College of Medicine in Houston cracked the Norwalk virus's genetic code 10 years ago, and scientists routinely began testing for it.
The BTI/University of Maryland report, "Human Immune Responses to a Novel Norwalk Virus Vaccine Delivered in Transgenic Potatoes," was authored by Arntzen; Estes;; Hugh S. Mason, a senior scientist at BTI; and by Drs. Genevieve Losonsky, Carol O. Tacket, and Myron M. Levine, of University of Maryland School of Medicine.
The research was funded in part by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.