Posted by KenC on February 22, 1999 at 13:23:16:
You can find this article at WWW.intellihealth.com
Pigs Grown With Human Genes
February 22, 1999
NEW HAVEN, Conn. (AP) — At a top-secret
farm hidden in the Northeast, scientists are
growing pigs whose DNA has been altered
with human genes.
It sounds like the stuff of science fiction, yet
officials at Alexion Pharmaceuticals Inc. say
they are close to figuring out how these pigs
can figure in the treatment of human organ
failures, spinal cord injuries and illnesses such
as Parkinson's disease.
The idea of transplanting animal parts to
humans, called xenotransplantation, isn't new.
But, until recently, nobody knew how to keep
the human body from rejecting the organs.
About 18,000 organ transplants are performed
in the United States each year and more than
40,000 patients are waiting for donor organs,
according to the United Network for Organ
Sharing. About 10 Americans die each day
waiting for transplants, network officials say.
Alexion's first altered pigs, created with the
help of researchers at Virginia Tech in the
early 1990s, contained a human gene called
CD-59. Scientists hoped the grafted gene
would trick the human body's immune system
into believing that the pig parts were human.
While transplanted organs from those pigs
were able to survive for a couple of days in
their new host, the body eventually rejected
the parts.
A major breakthrough came last year when the
small biotechnology firm, working with
scientists in Australia, figured out a way to
alter a sugar-like molecule in pig cells so that
human antibodies would not recognize it as
foreign.
The molecule had been acting as a magnet for
human antibodies, betraying the fact that the
transplanted tissue was not human. Alexion
quickly patented the process.
"If you now take cells from those animals and
challenge them with human serum, they are
almost indestructible in the lab," said Stephen
P. Squinto, the chief technology officer at
Alexion.
Scientists at Alexion have already transplanted
brain cells from their transgenic pigs into
rodents with a syndrome similar to
Parkinson's, a degenerative nerve condition
that affects motor function.
The transplanted cells not only survived, they
became neurotransmitters in the animals'
brains and helped correct the tremors, Squinto
said.
The same experiments are now being
conducted in baboons. If those experiments
work, Alexion hopes to begin human trials by
the end of the year. Researchers hope that
within 15 years humans will be able to receive
permanent organ transplants from swine.
The company also has seen remarkable results
by transplanting cells from a pig's snout into
the damaged spinal columns of rodents,
Squinto said. The cells replace the damaged
protective sheath around the spine and allow
nerve cells to regenerate.
"Would we expect that we will be able to take
a person who is a paraplegic and have them
walking or running in the Olympics?" Squinto
said. "No, I don't think that's the case. But
restoring some function to that person is
certainly a goal."
Xenotransplantation faces stiff opposition from
some in the medical community and from
animal-rights activists. Alexion was unwilling
to allow a reporter or photographer to visit
their facilities, in part because they could be
targeted by animal rights protesters.
Among the medical concerns: the fear that
transplanted organs could bring with them new
diseases caused by viruses now living only in
pigs. A virus originally transmitted from
chimpanzees to humans is believed to have
caused AIDS.
Because a transplant patient's immune system
is suppressed with drugs, xenotransplantation
provides an ideal environment for pig viruses
to mutate, said Dr. Thomas Murray, director
of the Center for Biomedical Ethics at Case
Western Reserve University.
"There are risks to third parties here," he said.
"If you get an organ from a cadaver, you
decide whether to accept that risk for yourself.
But if you get an organ from a pig, many more
people are put at an unknown risk."
The FDA had temporarily banned
animal-to-human transplant experiments
because of pig viruses, but dropped the ban
late in 1997. Scientists now believe they have
identified all the so-called retroviruses that are
unique to pigs and can screen for them,
Squinto said.
Dr. David Hull, director of the clinical
transplant program at Hartford Hospital, is
excited by the idea of farms filled with
transplantable organs.
The technology could dramatically improve
the lives of thousands of people, many of
whom can no longer even get out of bed
because their own hearts or livers are failing,
he said.
"You'd be able to meet the needs of
everybody," he said. "You would save a
tremendous amount of money and lives."
But animal rights activists say they whole
process is unnecessary. Rather than killing
animals for organs, they suggest everyone be
considered an organ donor unless they
specifically request an exemption, the opposite
of the current policy.
"That is the way to save a lot of money, and it
would save a lot of suffering," said Sandra
Larson, with the New England
Anti-Vivisection Society.