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Kendall
Powell
Someday soon, measles immunity
may be administered in the form of vegetables, not needles, if Australian
researchers' successful experiments with mice prove pertinent to humans,
too.
The researchers modified tobacco
plants, and then lettuce and rice, with the same viral protein found in
the measles booster shots, and fed the juice of these plants to mice.
The results demonstrated levels of viral protein in their system similar
to levels when booster shots are administered; these viral proteins enable
the body to create antibodies against measles. The mice that received
the modified plant juice showed significantly greater levels of measles
immunity than those fed juice from ordinary plants. They also showed levels
of immunity even higher than necessary for humans to guard against measles.
While results in mice don't
always translate to the same results in humans, it establishes principles
that pave the way for subsequent phases. The Australian researchers will
focus on macaques or baboons next. If it is proved that the measles vaccine
can be administered in oral form to humans, the implications will be profound,
particularly in third world countries.
Measles is highly contagious,
killing 800,000 people per year, including a high population of African
infants. An oral vaccine, in the form of any number of plants, wouldn't
require highly trained medical personnel to deliver or the use of refrigeration
- both in very short supply in third world nations. What's more, the modified
plant containing the vaccine could be grown locally. This means vastly
lower costs and much wider availability of the vaccine - and significantly
less death from the disease.
Vaccines against other diseases
are similarly being tested in plants elsewhere. Clinical trials with humans
are underway, for instance, with a potato vaccine booster used in combination
with injections against hepatitis B. But while the potential for such
edible vaccines is immense, so are the potential hurdles: obtaining approval
for such genetically modified crops will require many dexterous leaps,
as will establishing agricultural and dosing guidelines.
Nature
Science Update 22 July 2002
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