Vaccine In A French Fry?
Researcher Thinks So
By Maggie Fox
Health and Science Correspondent

WASHINGTON (Reuters) - U.S. researchers said Thursday they had genetically engineered potatoes to carry a vaccine against cholera, creating the possibility people could be inoculated by eating french fries. ``We anticipate that this system will be very useful in economically developing areas where cholera is endemic and where (other) vaccines don't work very well,'' said William Langridge of Loma Linda University in California, who led the study.
Langridge and colleagues genetically engineered potatoes to produce non-toxic cholera toxin B (CTB), a protein that sparks an immune response in mice and humans. The resulting potatoes are transgenic -- containing both potato and foreign genes. ``Humans, unlike mice, eat only cooked potatoes,'' they wrote in a report in the journal Nature Biotechnology. So they boiled their transgenic potatoes. ``We did cook the potatoes and were able to retrieve about 50 percent of the vaccine in the form that we know will (work),'' Langridge said in a telephone interview.
He does not know why his compound is more stable than earlier efforts and is not sure how much cooking it can take. ``I wouldn't cook it for an hour, say,'' he said, adding: ''We are going to get some protection even if we french fry.'' They have only tested mice so far. One day a week for five weeks the mice ate nothing but raw potato -- up to 10 percent of their body weight.
This would translate to a lot of potatoes for people but Langridge said there was evidence the vaccine worked more efficiently in humans, and people might be able to eat just one or two of the engineered potatoes a week. Langridge's team found antibodies to cholera in blood and feces from the mice and then did tests using intestines from inoculated mice.
``We open the mouse, take out a loop of the intestine, amd then tie it off with string so we have a kind of sausage,'' he said. ``Then we inject it with cholera toxin. If we get a diarrheal response then we know it's not working.'' The potatoes reduced the amount of diarrheal fluid in the intestines by 60 percent. Langridge said he has not tested his new potatoes on people, and has not tried the cooked potatoes in mice. That might come later. Adding the gene did not seem to harm the potatoes, which grew normally. ``I've tasted the potato and it doesn't taste any different to me,'' he said.
Langridge's team is also working on multiple vaccines for the U.S. Army. These would combine vaccines against cholera, rotavirus --- a common cause of diarrhea -- and the E. coli bacteria that cause food poisoning. Five million people get cholera every year and 200,000 die from it. Cholera, spread in bacteria-infected water, causes severe diarrhea and dehydration.
Many groups are working on vaccine foods, such as Axis Genetics in Cambridge, England, which is researching bananas. The Boyce Thompson Institute for Plant Research at Cornell University in New York has grown potatoes carrying vaccines against cholera. Theirs only works if the potatoes are eaten raw.
In 1995 Texas A&M University said it had grown transgenic potatoes carrying a gene for hepatitis B and said it stimulated antibodies to the virus.

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