Scientists are to create transgenic chickens that lay eggs crammed with disease-fighting human antibodies, writes Steve Farrar.
A team of experts from Origen Therapeutics, a United States biotech company set up to exploit commercially the genetic modification of chickens, has tested key steps of the technique. They expect to produce their first therapies in five years, giving new hope to those with Aids, transplant patients and other people whose immune systems have broken down.
Robert Etches, Origen's vice-president of research, who led efforts to create transgenic chickens at the University of Guelph, Canada, told the recent Plant and Animal Genome conference in the US that the method should yield human polyclonal antibodies far more efficiently than any other proposed technique.
At present, human polyclonal antibodies, which combat invading pathogens, can be extracted only from human serum. The new technique opens up the possibility of a cheap and plentiful source of the antibodies, which could be used to make medicines to fend off illnesses in people whose own immune systems do not work properly.
Dr Etches said: "These new lines of transgenic chickens will allow us to
create large amounts of human polyclonal antibodies at a very reasonable cost and help many people with an immuno-compromised state."
To create the disease-fighting eggs, the scientists first need to alter the chicken's DNA. To do this they will use embryonic stem cells, which make up the newly formed chicken embryo and go on to develop into the whole array of specialist cells found in an adult animal. These cells are extracted from a living embryo. The genes that control the creation of the chicken's own immune system are destroyed and replaced with sequences of human DNA that code for the production of human antibodies.
The modified cells are then put back into the chicken embryo. This embryo grows into a chicken that produces human polyclonal antibodies when it is exposed to the relevant pathogen. The chicken then lays eggs filled with the antibodies that could be used to make pharmaceuticals.
Chicken eggs are a particularly good source of protein and will contain high levels of antibodies. The rapid succession of generations compared with larger animals is another advantage to the technique, while chicken farms worldwide could easily be adapted for medicine production.