Cloned pigs represent organ factories for humans.

PPL Therapeutics Inc said it achieved the world's first successful cloning of pigs from adult cells on 5 March with the birth of five piglets. The US company, based in Blacksburg, Virginia, is a subsidiary of PPL Therapeutics plc, London, UK.

The cloning is an important milestone in the development of genetically engineered pigs to supply tissues and organs for transplant into humans, says PPL. This would create, in effect, an organ factory to serve the needs of humans.

Pigs share with humans relatively similar physiologies. It is for this reason the unfortunate animals are considered a potentially valuable source of transplant organs, such as hearts and kidneys, that are in short supply.

However, there are many obstacles before the utopia of organs on tap is achieved. One of the main technical barriers to such xenotransplants is rejection. The human immune system recognizes a particular sugar complex on the surface of pig cells as foreign. One particular pig gene is responsible for this tell-tale sugar. PPL received a 1999 award from the US National Institute of Science and Technology's Advanced Technology Program to develop the technology to clone pigs with that specific gene inactivated.

It is hoped that organs from a genetically engineered pig lacking this gene could be transplanted without triggering the human host's immune system. Also, more genes will have to be introduced into pig cells to prevent more delayed rejection responses.

PPL estimates the market for animal transplants will be worth around US$6.5 billion within ten years of launch. Other industries will also grow on the back of this technology.

(See also, Patent offers way round human rejection of pig-parts implants, p. 10, and back page for further discussion.)

For further information, contact: PPL Therapeutics Inc; Internet address: http://www.ppl-therapeutics.com; or Michael Baum, National Institute of Science and Technology, tel: +1-301- 975-2763; E-mail: michael.baum@nist.gov; Internet address: http://www.atp.nist.gov