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© St. Petersburg Times, published January 3, 2002
Five cloned pigs born in Virginia on Dec. 25 are being called a major step toward production of animal organs and cells for use in human bodies.
"This is the first step in overcoming the rejection of pig organs in humans," said David L. Ayares, vice president of research for PPL Therapeutics of Edinburgh, Scotland.
"The promise of (cross species) transplantation is now a reality," said Alan Colman, research director at PPL, "with the potential to revolutionize the transplant industry."
As an example, Ayares said the testing of insulin-producing pig cells in primates could begin within two years, and clinical trials in humans could begin in four years "or less."
The work was carried out by PPL's U.S. subsidiary located in Blacksburg, Va. PPL is the commercial offshot of the Roslin Institute in Scotland, well known for cloning the first adult mammal, Dolly the sheep, in 1996.
Wednesday's announcement was not purely scientific, however.
PPL's statement to the media boasted not only of the cloned pigs, but also of the economic opportunity they present.
"The birth of these pigs ... should spark renewed vigor from both the scientific and investment communities," Ayares said. "This advance provides a near-term solution for overcoming the shortage of human organs for transplants as well as insulin-producing cells to cure diabetes."
In an interview Ayares acknowledged that the U.S. subsidiary is looking for a partner to help spin off from its overseas parent company, which is feeling investor pressure to use its money to get another product to market as quickly as possible.
"It's a fact that the company, while generating data (on the cloned pigs), also discovered limitations with its financial resources," Ayares said. "We were getting pressure to get (an emphysema product) into Stage 3 clinical trials, so we could launch by 2005."
He bristled at a suggestion that PPL's search for an investing partner might have prompted Wednesday's announcement as much as the scientific advance.
"We are not unethical; we do not fudge data," he said. "We have a good record in the field."
He acknowledged that PPL's work on the pigs has not yet been submitted for publication in a scientific journal, however, and therefore has not been subjected to peer review. It will be, he said.
"We are submitting to journals now. We are finishing off the manuscript."
The five female piglets -- Noel, Angel, Star, Joy and Mary -- are expected to serve as the primary stock from which researchers will create 10 to 20 families. A group of in utero males is expected to be born within a few months.
The pigs are called "knockouts," meaning that a specific gene has been deactivated, or knocked out of their DNA.
The gene is the one that causes the human immune system to speedily reject pig organs or cells. It is responsible for making an enzyme that adds a sugar to the surface of pig cells. The human immune system recognizes this sugar as foreign and triggers a response -- within minutes -- called "early hyperacute rejection."
John Cannon, an expert on knockout genes at the University of South Florida and All Children's Hospital, called PPL's work "very interesting and definitely an essential first step toward xenotransplantation (cross-species transplantation) using pig organs."
He warned, however, that problems might lie ahead and that "any further claims by the company of revolutionizing this field should be considered very premature."
Knocking out the gene that causes early hyperacute rejection may not end the human body's effort to reject the foreign cells, he said.
"There are likely a very large number of proteins on the pig cells that, in aggregate, might cause trouble in long-term grafts -- you just can't tell upfront," he said.
"The main point is that xenotransplantation, while very plausible even within the next five to 10 years, is a very complex process that is going to have a large number of barriers to overcome. Only some of these barriers can be predicted at the outset."