- WASHINGTON (Reuters) - The scientific team that cloned Dolly the sheep has
joined forces with a U.S. company to try to use their cloning techniques
and genetic engineering to fight mad cow disease, the companies said Tuesday.
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- They said they also wanted to clone animals
whose organs could be used as transplants into humans. The U.S. company,
Newtown, Pennsylvania-based Kimeragen Inc., says the partnership will combine
its new approach to gene therapy, called chimeraplasty, with the cloning
technology developed by the Roslin Institute and PPL Therapeutics Plc to
create Dolly. The collaboration agreement is between Kimeragen and Roslin
Bio-Med Ltd., the biotechnology company set up by the Edinburgh-based Roslin
Institute.
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- ``It's a marriage between the nuclear
transfer (cloning) technology, which is a terrific technique for making
identical animals, and our technology, which is very specialized and precise
for altering genes,'' Dr. Gerald Messerschmidt, president and chief executive
officer of Kimeragen, said in a telephone interview.
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- ``What we are mostly looking at from
a commercial standpoint are herds that would be donating organs,'' he said.
The hope is to create herds of sheep, at least at first, that are free
of scrapie, their version of mad cow disease, and whose organs are similar
enough to human organs to be used for transplant. Kimeragen's chimeraplasty
technique allows scientists to make precise genetic modifications. Most
genetic engineering is hit-and-miss -- the scientists have no way of knowing
whether the targeted cells will take up and use the new gene, and they
cannot control where the gene goes in the cell.
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- With chimeraplasty, Messerschmidt believes,
this process can be controlled. It acts as kind of a chemical instruction
to the cell itself to alter the gene in the desired way. The method takes
the desirable stretch of DNA and combines it with RNA, which is the chemical
that translates DNA's genetic code into something the body can actually
use -- a protein. This combination is the chimeraplast. ``Once we know
the sequence of the gene, then we build the chimeraplast so it binds to
the exact location where we want to make a change,'' Messerschmidt said.
``Some people have described it as genetic white-out. Like many important
discoveries it's so simple you say 'why wasn't this discovered earlier?'''
The companies are taking two experimental gambles. First, they want to
breed sheep that completely lack prions -- the brain proteins that mutate
to cause bovine spongiform encephalopathy (BSE or mad cow disease), scrapie
in sheep and Creutzfeldt-Jakob disease (CJD) in humans.
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- Messerschmidt is betting that sheep can
get along fine without any prions at all, although when normal they are
quite common in the brain. If that does not work, he says, ``the refinements
can come in the second step.''
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- ``We think we can make herds of animals
that have that disease gene eliminated,'' Messerschmidt said. ``What we
are mostly looking at from a commercial standpoint are herds that would
be donating organs, organs that are obtained from animals that are free
of prions.'' Along those lines, Kimeragen also wants to make herds of cloned
animals that lack a surface sugar on their organs that makes them look
``foreign' to human immune systems.
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- Organ rejection is caused when the immune
system sees a foreign object in the body. It does this by sniffing the
sugars on the surface of the organs. But Messerschmidt thinks a simple
genetic change can make animal organs ``smell' human to the immune system.
The new research team will include Ian Wilmut, the Roslin Institute scientist
who led the Dolly team.
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