Chickens modified to produce human proteins

Scottish researchers have genetically modified chickens to produce human proteins in their eggs, which, they say, could offer a cost-effective way to produce certain types of drugs.

During their study, which is reported in the journal BMC Biotechnology, they found that the drugs workd at least as well as the same proteins produced using existing methods.

“We are not yet producing medicines for people, but this study shows that chickens are commercially viable for producing proteins suitable for drug discovery studies and other applications in biotechnology,” says Helen Sang, from the University of Edinburgh’s Roslin Institute.

Eggs are already used for growing viruses that are used as vaccines, such as the flu jab. Sang and colleagues say their approach is different because the therapeutic proteins are encoded in the chicken’s DNA and produced as part of the egg white.

Large quantities of the proteins can be recovered from each egg using a simple purification system, they say, and there are no adverse effects on the chickens themselves, which lay eggs as normal.

The work has initially focused on two proteins that are essential to the immune system and have therapeutic potential: the human protein IFNalpha2a, which has powerful antiviral and anti-cancer effects, and the human and pig versions of a protein called macrophage-CSF, which is being developed as a therapy that stimulates damaged tissues to repair themselves.

The researchers found just three eggs were enough to produce a clinically relevant dose of the drug. As chickens can lay up to 300 eggs per year, they say their approach could be more cost-effective than other production methods for some important drugs.

Protein-based drugs, which include antibody therapies such as Avastin and Herceptin, are widely used for treating cancer and other diseases.

For some of these proteins, the only way to produce them with sufficient quality involves mammalian cell culture techniques, which are expensive and have low yields. Other methods require complex purification systems and additional processing techniques, which lifts the cost.

Scientists have previously shown that genetically modified goats, rabbits and chickens can be used to produce protein therapies in their milk or eggs.

The researchers say their new approach is more efficient, produces better yields and is more cost-effective than these previous attempts.

“We have validated the transgenic chicken system for the cost-effective production of pure, high-quality, biologically active proteins for therapeutics and other applications,” they write in their paper.