These three genetically modified sheep have recently begun producing milk
containing alpha-1-antitrypsin, a protein that is used to treat the lung
disease hereditary emphysema. Pharmaceutical Proteins, in Edinburgh, first
produced sheep carrying a human gene for making antitrypsin three years ago.
Four of the initial five were females, and the 鈥榮tar鈥� performer, called
Tracy, produced 35 grams of antitrypsin per litre of milk. Only one of the
sheep was a ram, and the three animals above belong to his first set of
seven daughters. The seven are all producing commercially useful amounts of
antitrypsin.
Here, three of the half-sisters share a milking platform which is too small
to accommodate all seven of the 鈥榤ini-flock鈥� at once. 鈥榃e do three first,
then the other four,鈥� says Ron James, managing director of the company. The
company is preparing to apply for permission to start clinical trials of the
drug, but says that it must first build a high-grade dairy and purification
unit to generate the required amounts to a high enough standard of purity.
