Cloned Pigs May Aid Organ Transplants

Five special piglets born on Christmas Day in the US could be used in future animal organ transplant operations for humans.

Scottish-based firm PPL Therapeutics, which was behind the cloning of Dolly the sheep, produced the healthy quintet and said it thought they were the world's first cloned "knockout" pigs born.

A "knockout" pig has the alpha 1,3 galactosyl transferase gene inactivated which prevents the human immune system rejecting pig organs.

The body's defence mechanism leaps into action when it detects the presence of a "foreign" organ.

The gene produces an enzyme that adds a sugar to the surface of pig cells. It is this that is recognised as "foreign" by the human immune system. Without it, the body finds the pig organ far less of a threat.

PPL said the births of Noel, Angel, Star, Joy and Mary were a major step towards successfully producing animal organs and cells for use in the procedure.

They were born as a result of using cloning and PPL's patented gene technology, and have been confirmed through DNA tests to have one of their two copies of the gene inactivated.

Cloning of the animals took place in the lab, following which the fertilised eggs were put back inside the mother pig, who gave birth, a spokesman said.

The work was carried out by PPL's US subsidiary in Virginia, and was partly supported by a grant from the US Government.

PPL said pigs were the preferred species for xenotransplantation - the transfer of cells or organs from one species to another - on both scientific and ethical grounds.

lan Colman, research director at PPL, said: "With one of the major technical hurdles and scientific risks overcome, the promise of xenotransplantation is now a reality, with the potential to revolutionise the transplant industry."

Since 1905, a total of 82 people have received whole organs from chimpanzees, baboons, pigs, goats and other animals but none of the operations have been successful.

At the end of November 2001, a total of 4835 patients in the UK were waiting for kidneys, 158 for livers, and 98 for hearts.

The first application of the technology is expected to be the transplantation of insulin-producing pancreas cells from pigs to humans. PPL says clinical trials could start in as little as four years.

From there it could be a relatively short step towards transplanting kidneys, hearts and other organs.

But, Dr David Ayares, from PPL's US division, said: "The birth of these pigs is a critical milestone in our xenograft programme and should spark renewed vigour from both the scientific and investment communities.

"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."

However, opponents of xenotransplantation said the development did not make the transfer of organs from pigs to humans any safer.

One very important obstacle yet to be overcome is the danger of transferring pig viruses to humans as pigs possess a family of Aids-like viruses called Porcine Endogenous Retroviruses, or PERVS.

These viruses are harmless to pigs, but no one knows what effect they might have in the human population.

Dr Andre Menache, president of Doctors and Lawyers for Responsible Medicine, said xenotransplantation still presented a "Frankenstein scenario".

"There are about 600 genes responsible for tissue matching. You don't have to get all 600, but I would have thought you have to get quite a lot more than one right.

"I am by no means convinced. It belies common sense. The issue is a lot more complex than these people make it out to be," he said.

"It seems that all this money and time is being invested in animal experimentation when more and more successes are being made in more viable alternatives, such as stem cell production.

"We are opposed to xenotransplantation from a public health point of view, from a moral point of view and from an animal cruelty point of view.

"The strongest argument is still the threat of transmission of known and unknown viruses.

"It only needs one successful transmission of a disease-causing virus from an animal to man to start an epidemic.

"Viruses which are not dangerous in pigs can become dangerous in humans.

"One of the triggers for mutation of viruses is a change of environment, so xenotransplantation provides the ideal conditions for that. It is a Frankenstein scenario."

The British Union for the Abolition of Vivisection said clinical trials for xenotransplantation were still not a viable proposition.

Sarah Kite, BUAV's Research and Information Director, said: "Xenotransplantation research causes unacceptable suffering to sentient animals.

"Not only do we question the right to genetically engineer animals to use as spare-parts, we also believe that the science of xeno is so poorly developed that clinical trials cannot be reasonably be considered.

"In the meantime we should be doing all we can to improve the shortage of available human donor organs without resorting to animals."

Copyright © 2002 ITV Network Limited.

This article posted November 23, 2003.