- A genetically modified potato containing a vaccine for
hepatitis B has been successfully tested on animals, scientists reported
yesterday.
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- The breakthrough by researchers at Cornell University
in New York raises the prospect of cheap and effective oral vaccines in
fruit and vegetables, which could revolutionise healthcare in the Third
World.
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- In a study reported in Nature Biotechnology, scientists
modified potatoes with a gene for HBsAg, an antigen found on the surface
of the hepatitis B virus that stimulates the body to produce antibodies
but does not cause infection. HBsAg is the basis of existing vaccines for
the disease, administered by injection.
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- Mice fed three times a week with the GM potatoes began
to produce antibodies to hepatitis B, which would protect them from infection
with the virus, the study found.
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- The experiment is the first to prove that an oral vaccine
gives rise to antibodies in the blood to a disease that is not transmitted
orally. The only such vaccine presently available is for polio, which infects
its victims orally. Hepatitis is transmitted by sexual or blood contact.
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- More than two billion people - about a third of the world's
population - have been infected with hepatitis B. Of these, up to 500 million
are chronic carriers, who are at risk of developing the acute form of the
disease.
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- Symptoms of the virus include poor appetite, nausea,
vomiting, headaches, general malaise and jaundice. Its effects can include
long-term liver damage and liver cancer.
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- An injectable vaccine developed in 1978 has largely limited
the spread of the disease in the developed world. The traditional vaccine,
however, must be kept refrigerated and at £10 a dose is often too
expensive to be used in the Third World.
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