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Why did the chicken cross the DNA?

Advances in transgenics and drug production are foreseen using chicken eggs, says the Roslin Institute. But why chickens?

By | December 6, 2000

EDINBURGH The Roslin Institute held a special news conference today, delighting scientists with the idea of producing drugs in chicken eggs but disappointing the media when 'Britney' the hen failed to make an appearance.

The Roslin Institute reached celebrity status when it gave birth to Dolly the sheep in 1997. Its latest project is in collaboration with Viragen, Inc., a US biotech company based in Plantation, Florida and Edinburgh. "The essence of this project is to create chickens which produce eggs containing new drugs to treat many serious diseases, including cancer," said Dr Helen Sang, lead scientist on avian transgenic technology at the Roslin Institute.

Dr Sang was the first person to produce a trangenic chicken by direct injection. First generation transgenics has had a low success rate, however, because the process is very difficult to control. DNA is directly injected into the germinal disk of a hen's egg, where the fertilised zygote is found, but this is a hit and miss process.

In a collaboration that will combine the Roslin Institute's expertise in cloning with Viragen's development of antibodies as anti-cancer agents, the two organisations now propose to work together to produce (among other products) monoclonal antibodies in eggs through a more efficient process: nuclear transfer. According to Professor Grahame Bulfield, the Director of the Roslin Institute: "Nuclear transfer allows much more precise control over where and how genes are inserted into hens."

Avian technology has many advantages over the genetic modification of cows, sheep and goats, which are being developed to produce drugs in their milk. Chicken eggs can be produced much faster, with lower costs and longer term production thanks to the chicken's prolific egg laying capabilities. In the words of Professor Bulfield: "Laying hens have the advantage of short generation time, allowing production flocks to be created from founder animals within a year."

Viragen's CEO and chairman Gerald Smith said that the collaborative project will enable the production of a wide variety of drugs in greater volume and at a fraction of the cost when compared to manufacturing methods. "Only a nominal outlay would be required to produce the special chicken flocks thereby eliminating the huge capital expenditures now required for buying reactors and building related facilities," he said.

The financial and medical implications for the research are considerable. In traditional cell culture it costs $100 per milligram of drug produced in contrast to the 10-25 cents that it would cost per milligram in eggs. And researchers think they could get this cost even lower.

There are still many technical difficulties to be overcome, such as not being able to see the maternal nucleus. "So far, no-one has produced a transgenic hen in this way," said Viragen's Karen Brown, adding for the benefit of misinformed readers of the Mail on Sunday: "Britney is an invention." On 3 December the weekly newspaper announced that Britney the hen would be centre stage at the Edinburgh news conference today. As the collaboration between the Roslin Institute and Viragen did not even begin until 4 December, the newspaper has come out with egg on its face.

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