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- Tomatoes and bananas genetically modified to contain
hepatitis B vaccine could rid the world of the virus, a leading American
scientist said in London yesterday.
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- The virus, which causes high fever and attacks the liver,
is a precursor of liver cancer, the biggest single cause of cancer deaths.
This new development will save hundreds of thousands of lives a year, said
Charles Arntzen, the scientist who developed the technology.
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- The breakthrough in producing a cheap, stable vaccine
by genetically modifying plants became biology's holy grail in the 1990s,
and is seen by the US bio-tech industry as its vindication and public relations
saviour. Plant vaccines will be a billion-dollar business, said Professor
Arntzen, who leads a team of the world's top plant scientists at Cornell
University in New York state.
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- Successful experiments show that the vaccine worked,
he added, and will cost less than one penny a dose to make. A single
gene transferred into a tomato or banana plant is reproduced as a protein
thousands of times inside the fruit. When eaten it passes into the intestine
and then into the blood stream producing antibodies against hepatitis B
- working the same way as a traditionally injected but much more expensive
vaccine.
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- A single dried banana chip or tomato paste sandwiched
in a wafer contains enough protein to act as a vaccine dose. Traditional
vaccines have to be refrigerated and cost £10 for a successful course,
making them too expensive for developing countries where hepatitis B kills
many people directly and causes the death of many more through subsequent
cancer.
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- Prof Arntzen, who is director of the Boyce Thompson institute
for plant research at Cornell, has been visiting his opposite numbers at
Britain's top plant research laboratory, the John Innis institute attached
to Norwich University.
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- Talking to scientists at the US embassy in London, he
said it was the most exciting area of biological science and that 40 new
vaccines being worked on worldwide opened the possibility of eradicating
some diseases altogether.
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- His institute was founded by a high-ranking Salvation
Army officer in the 1920s to expand human understanding of plants and to
enhance their benefits to humankind. It was for this altruistic reason
that its scientists had tried to produce cheap vaccines from plants that
would benefit millions of people in the developing world who could not
afford western medicine.
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- "We have rid the world of smallpox through vaccination,
we are close with polio. Now I believe we can do it with hepatitis B too,"
Prof Arntzen said.
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- His experimenting began in the 1990s with e-coli antibodies
being genetically introduced into potatoes and fed to mice. A small quantity
of uncooked potato was enough to produce antibodies in mice. Three clinical
trials on human volunteers produced the same results but it did not work
in cooked potatoes because the antibodies producing proteins were too unstable.
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- However, when the technology was used for hepatitis B
using tomatoes, the proteins remained stable, allowing the vaccine to work
even in processed or dried tomatoes. Thirty original plants, producing
15lb of tomatoes a week, were enough to produce thousands of doses of effective
vaccine at one cent per four doses.
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- The vaccine has been held back because the US department
of agriculture and the food and drug administration had no licensing mechanism
for plant vaccines. "They are working on it and hope to have something
up and running in two years," said Prof Arntzen.
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