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For several years, scientists have been
trying to develop vaccines
that are delivered through foods such as potatoes
and tomatoes rather than needles.
The hope is that edible vaccines may
be more practical for use in developing countries, since
the foods do not need to be refrigerated as ordinary vaccines
must, and the edible vaccines do not require syringes and
other medical equipment.
So far,
plant-based vaccines have met with limited success.
One problem has been figuring out a
way to get edible vaccines into gut tissues without being
destroyed by digestive juices.
Researchers got past this obstacle by
designing a vaccine around the cholera toxin, which can
latch onto the lining of the gut without being destroyed
by digestive juices. Normally the ability of the toxin to
survive in the gut has harmful consequences, leading to
cholera, but the researchers were able to use the toxin
without causing disease.
Investigators took bits of the cholera
toxin and joined them with proteins, or antigens, from two
other infectious pathogens that invade the gastrointestinal
tract -- rotavirus and a strain of E. coli bacteria. They
then developed a genetically
modified potato that contained the triple combination.
The approach seems to work as the investigators
found that female mice that ate the genetically modified
potatoes developed antibodies to all three microbes.
Nature Biotechnology
June 2001;19:548-552
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