04:24 PM ET 10/20/98
Dolly cloners make deal with U.S. company
By Maggie Fox, Health and Science Correspondent
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.
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.
``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.
``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.
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.
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.''
``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.
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.
^REUTERS@