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Thursday, 22 August, 2002, 16:39 GMT 17:39 UK
Cloned pigs raise transplant hopes
World's first "double-knockout" pigs

A British biotechnology company is claiming a breakthrough in the quest to create organs for transplant from pigs into humans.

PPL Therapeutics, based near Edinburgh in Scotland, says it has created the first so-called "double knock-out" pigs, genetically-engineered to lack both copies of a gene which causes rejection.

Scientists have given a mixed reaction to the claim.

Some experts say it represents a genuine advance, while others caution that it is one small step along a very long road.

PPL has also been criticised for publicising the news in a press release, rather than publishing its data in a scientific journal where the merits of its research could be more accurately judged.

Double knock-out

For many years now scientists have been trying to genetically modify pigs so that they could grow organs suitable for transplant into humans - the procedure known as xenotransplantation.

Some people spend years on dialysis
There is currently a great shortage of organs from human donors, which could be solved by having a reliable supply from pigs.

Many people who need a kidney transplant have to spend years on dialysis waiting for a suitable organ to becomee available.

However the human immune system swiftly rejects tissue from ordinary pigs, because pigs produce a special sugar called alpha 1,3 galactose, which immune cells target.

The key to preventing this rejection is to remove from the pigs' DNA a crucial gene which makes an enzyme that transfers this sugar to the surface of cells.

Earlier this year two biotechnology firms, PPL and its American rival Immerge BioTherapeutics, announced the creation of pigs missing one copy of the gene.

Now PPL has gone a step further by producing pigs lacking both copies.

Mixed reception

David Ayares of PPL said in a statement "This advance brings us closer to the promise of a potential solution to the world-wide shortage of organs and cells for transplantation."

Some leading scientists agreed. Professor Sheila MacLean of Glasgow University said "it is clearly a major step forward and if widely applicable would certainly reduce the practical problems associated with xenotransplantation."

However Chris Rudge, Medical Director of UK Transplant, part of the British National Health Service, was cautious.

"Although this is a very interesting development there is still a lot of research work to be done before anyone knows whether this is likely to be successful in humans," he said.

"There are very real concerns over the risks associated with the possible transfer to humans of infections from pigs."

The fear that pig viruses could enter the human population is one of the reasons why the experimental transplant of pig organs into humans is forbidden in many countries.

Share concern

Professor Patrick Bateson, who chairs the Royal Society's working group on genetically-modified animals, was scathing about PPL's decision to publicise its research by press release, rather than going down the more traditional and formal path of publishing its work in a scientific journal.

"The scientific community will be sceptical about this so-called breakthrough until the work has been subjected to rigorous peer review by other researchers in the field," he said.

"This announcement, which no doubt will boost the company's share price, could be considered premature before other scientists have had a chance to look at the claims."

Professor Bateson's comment on PPL's share price was only partially correct. By mid-afternoon on Thursday, several hours after the news came out, shares in London were up by 0.5 of a penny 7.25 pence.

Parallelling a general trend in the biotechnology sector, PPL's price has fallen markedly since its flotation in 1996.

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The BBC's Rachel Ellison
"If successful animal to human transplants will be next"
See also:

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