- 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.
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- 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.
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- 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.
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- 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.
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- ``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.
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- 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.
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- 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.
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- 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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