Polly, the first "designer" sheep who is also a clone, has been genetically engineered to produce milk containing a protein that should help hemophiliacs, her creators said this week.
They said Polly, whose birth was announced in July, carried a human gene for the production of Factor IX, a blood product used to treat hemophiliacs.Polly is an advance on Dolly, the sheep whose birth stunned the world in 1996 when she was cloned using an adult cell from the sheep's mammary gland.
Factor IX is important for blood clotting. People with hemophilia B, also known as Christmas disease, are deficient in Factor IX. There are about 7,000 patients in North America, Europe and Japan.
Currently, such hemophiliacs are treated with Factor IX taken from human blood donations or with protein taken from cell cultures, some of which are genetically engineered.
Scotland's Roslin Institute and its commercial partner, PPL Therapeutics Inc., announced details of Polly's creation in this week's issue of the journal Science.
PPL hopes Factor IX from sheep's milk will be a cheaper source, and one free of any possible infection. Many hemophiliacs given infected human blood have developed HIV infection, hepatitis and other blood-borne diseases.