This little piggy...

A litter of five cloned piglets was born on Christmas Day in Virginia, US. Named Noel, Angel, Star, Joy and Mary, the piglets had also been genetically altered so as to make their organs more compatible for transplant into humans.

PPL Therapeutics, the commercial arm of the Roslin Institute which cloned Dolly the sheep, used a 'knock-out' technique to inactivate a gene in the pigs that produces an enzyme called alpha 1-3 galactosyl transferase. This enzyme causes pig organs to be coated with a sugar that the human immune system recognises as foreign. Knocking out the gene therefore reduces the likelihood of the pig organs being rejected if transplanted into humans.

It is hoped that the technique will make the possibility of xenotransplantation a reality, consequently providing some solution to the shortage of human organs and tissues available for transplant. Alan Colman, research director at PPL, said that experimental trials on monkeys may take place within four years and later experiments may take place on humans once the safety of the transplants has been determined.

The announcement of PPL's success in cloning the genetically altered pigs came days before a similar announcement by Immerge Bio Therapeutics, an American company which produced its 'knock-out piglets' three months ago.