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Genetic engineering, often slammed by
environmental and consumer groups for its role in altering
staple foods, may have found a indication.
By using biotechnology to incorporate
useful genes into an almost limitless variety of common plants,
from rapeseed and tobacco to potato, tomato and banana, scientists
aim to produce cheap and stable vaccines in an edible form
-- and beat disease.
Scourges such as cholera, tuberculosis
and hepatitis, all responsible for the deaths of millions
every year, including many children in developing countries,
have been targeted as candidates for vaccines that can be
engineered from plants.
So far, there
seems to be no obvious end to the sheer variety
of biotechnology's potential applications in the fight against
disease. Even the roots of the humble tobacco plant are being
used to mass-produce a vaccine against scorpion stings in
Brazil, which may eventually be incorporated into fruit.
Genetic modification (GM) involves exchanging
or splicing genes of unrelated species that cannot naturally
swap with each other. The species can be as different as chalk
and cheese.
Scientists have spliced spider venom
genes into maize and other food crops as a "natural pesticide"
to deter insects and birds from feeding on the plants, and
inserted fish antifreeze genes into tomatoes to extend their
growing season into winter.
Vaccines
in Variety of Common Foods
The first human clinical trial of an
edible vaccine took place in 1997 when volunteers ate raw
potatoes that were genetically engineered against the common
E. coli bacteria.
Since
then a whole range of plants, most often vegetables, has come
under the bioscientist's knife for adaptation as
a possible host for vaccines. Foods under study include bananas,
potatoes, tomatoes, lettuce, rice, wheat, soybeans and corn.
Last year, mice were fed with modified
potato containing an oral vaccine for hepatitis B that passed
through the animals' stomachs without being broken down and
stimulated the production of antibodies against the disease.
Scientists now say tomatoes and bananas
genetically modified to contain such a vaccine may be able
to eradicate the virus.
Clinical trials have been conducted on
pigs using an edible vaccine for transmissible gastroenteritis
in corn, while work is continuing on a vaccine using tomatoes
for RSV, a respiratory virus that can be fatal for infants
less than 6 months old.
Hope
in Fight Against Malaria?
So far, the most trumpeted success story
of biotechnology's use in medicine probably came last year
when an Anglo-German team of scientists inserted a foreign
marker gene into the mosquito genome, allowing the possibility
of genetic alteration.
While recognizing that the breakthrough
was not yet a cure for malaria, the team hailed the achievement
as their "holy grail" and a major advance in malaria
control -- after 15 years of efforts to create the world's
first transgenic mosquito.
At the time, the team said it might now
be possible to create a mosquito that was stable, safe and
physically unable to transmit the malaria-causing parasite,
maybe within 6 years.
Now, according to one of the team's leaders,
there may be reason to rejoice sooner as the battle against
malaria nears its end. This
tropical disease is responsible for more than a million deaths
every year, mainly among young children in Africa.
"Progress has been incredible in
this field and probably it may take less time," said
Andrea Crisanti at the Department of Biology at London's Imperial
College. "Progress has been very fast during the last
year, faster than anticipated.
"More release trials will be carried
out on islands where malaria is endemic. If this proves successful,
then a different and more sophisticated approach will be undertaken,"
he said. "The idea is to introduce a mosquito which is
then able to breed with indigenous mosquitoes and so spread
the resistance gene."
GM
Use in Medicine
The world biotech industry is no
stranger to controversy and comes under regular attack from
environmentalists and concerned consumers, mainly
on account of its work in modifying food crops for what its
critics see as purely commercial motives.
Although still in their infancy, edible
vaccines made by bioengineering are unlikely to avoid this
debate and will in any case be subjected to years of rigorous
testing before commercial licensing can be granted, experts
say.
Reuters
London, November 9, 2001
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