The Incredible Biotech Egg -- Protein Factory of the Future

Two biotech companies have created transgenic chickens that might become the next major producers of genetically engineered proteins, displacing bacteria, mammalian cells, and even transgenic mammals. Combining low overhead with highly efficient protein production and ease of purification, eggs provide a low cost alternative to costly cell culture and transgenic herds.

GeneWorks (Ann Arbor, MI) has a flock of between 50 and 60 genetically engineered birds, some carrying a gene directing the synthesis of human growth factor in their eggs, and others producing a human antibody. While the company is holding information on the exact proteins produced close to its chest, it says that both have great potential for treating disease. According to its chief operating officer Steve Sensoli, GeneWorks has deals to make 14 proteins for six drug companies around the world.

Meanwhile, AviGenics (Athens, GA) has produced a human interferon in its flock of birds, and has flocks that have passed on transgenes through three generations. With hens producing an average of 200 eggs each per year, and 100 milligrams or more of a drug in each egg, both companies believe the yields could be large and lucrative.

Both flocks of transgenics have been made using viral vectors. GeneWorks uses the reticulo-endotheliosis virus with a promoter that restricts production of the protein to the egg white.

"We put it in a one-day-old chicken embryo by microinjecting it into a cavity called the blastoderm," explains Sensoli, in the hopes that some virus reaches primordial cells which develop into sperm and eggs, ensuring that the gene will be passed down to future generations of chickens. But the company can already harvest the proteins from hens that have been injected, and next year plans to open a production plant capable of making "metric tons" of protein.

AviGenics, which uses the avian leukosis virus as a vector, already has transgenic cockerels producing new generations of GM birds. "They're very busy," says Carl Marhaver, the company's president. "We microinject it into the pronucleus in the egg yolk," says Marhaver. The gene is then expressed in all the chicken's cells. AviGenics plans to contract out production and protein purification to companies that already produce vaccines in chicken eggs—a long-established practice in the pharmaceuticals industry.

Sensoli says the work it too commercially sensitive to publish, and all but two of the proteins under development are unknown outside the companies that discovered them.

For more information: Carl Marhaver, President and CEO, AviGenics, 425 River Rd., Athens, GA 30602-2771. Tel: 706-227-1170. Fax: 706-227-2180. Email: information@avigenics.com.

Or: Steve Sensoli, Chief Operating Officer, GeneWorks LLC, 3950 Varsity Dr., Ann Arbor, MI 48108. Tel: 734-975-4000. Email: genework@provide.net.

Edited by Laura DeFrancesco