Transgenic chickens lay drugs in eggs
Pastor Dale Morgan
*Transgenic chickens lay drugs in eggs*
By Karla Gale in New York
January 24, 2007 11:49am
Article from: Reuters
BRITISH scientists have succeeded in producing multiple generations of
genetically modified hens that produce pharmaceutical proteins in the
whites of their eggs.
To transfer drug-making genes into chickens, Dr Helen M. Sang, from the
Roslin Institute in Midlothian, UK, and her associates used a lentivirus
carrier from which all viral coding sequences were deleted.
The genetic material was replaced with the gene-regulating ovalbumin
production combined with genes for making human interferon or an
antibody targeting malignant melanoma.
"This construct is used to incorporate new protein genes into the
chicken chromosome," Dr Sang said.
This was accomplished by injecting the lentiviral vector containing the
coding sequences for the desired pharmaceutical protein into the
fertilised embryo of a newly laid egg.
When the resulting chick is old enough, it is then bred and the
offspring examined.
"If the offspring are transgenic, we will see the new genes in every
cell of their body, but only expressed in the oviduct," Dr Sang said.
In their paper in the early edition of the Proceedings of the National
Academy of Sciences, the researchers explain how a single transgenic
cockerel was crossed to normal hens.
Of 463 chicks they examined, 19 (4 percent) were transgenic.
When transgenic hens lay eggs, the foreign protein is expressed in the
oviduct where the egg white is made.
In the case of interferon produced in egg white, the researchers were
able to confirm that the compound was functional by showing that it was
active against a test virus.
Dr Sang hoped using transgenic chickens to produce therapeutic proteins
would "bring down the costs of drugs that currently are prohibitively
expensive".
The Roslin Institute, renowned for its creation of Dolly the cloned
sheep 10 years ago, is working in collaboration with gene therapy
company Oxford BioMedica and biotech company Viragen to develop their
transgenic chicken system as a large-scale biomanufacturing alternative
for a variety of proteins.
"But it is still early days yet," said Dr Sang. "We've made significant
steps in developing a process that we hope will be an alternative
production platform for protein drugs."