US scientists have discovered how to make hens lay eggs that contain proteins for use as drugs for humans. Reporting in the April issue of the journal Nature Biotechnology, the scientists, from the company AviGenics, said they inserted a new gene into the DNA of American white leghorn chicken embryos.
When the chickens matured, the eggs that they laid contained the protein that the inserted gene had given the code for. The level of the protein remained consistent in all eggs, and in eggs laid by a subsequent generation of hens.
The technique could be used to produce a large number of proteins used in human medicine. The proteins would be extracted from the white of the eggs and converted into 'a more conventional form'. Each egg is expected to yield approximately 17 milligrams of a protein, which is potentially enough for several doses.
Although other animals have been genetically altered to produce proteins useful for humans in their milk, the scientists believe that the egg proteins have several advantages. Alex Harvey from AviGenics says that because the species of hen used can produce up to 330 eggs per year, as well as the fact that chickens mature faster than, for example, cows, goats or sheep, they can be used to produce 'high-dose, low-potency drugs'. It is also thought to be easier to extract the proteins from eggs.