Researchers have made genetically modified chickens that can't infect other birds with bird flu. The H5N1 strain of influenza — which raged through southeast Asia a decade ago and has killed hundreds of people to date — remains a problem in some developing countries, where it is endemic.

The birds carry a genetic tweak that diverts an enzyme crucial for transmitting the H5N1 strain. Although they die of the disease within days, the molecular decoy somehow impedes the virus from infecting others.

The researchers said that although large-scale distribution of the genetically modified (GM) birds will one day be feasible, their study is meant only to show proof-of-concept of the technique.

"We have more ambitious objectives in terms of getting full flu resistance before we would propose to put these chickens into true production," said Laurence Tiley, a molecular virologist at the University of Cambridge, UK, and lead investigator for the study. His team is now working on further genetic tweaks that would inhibit the virus in different ways. "It would be a bit like combination drug therapy for HIV," he said.

Other experts pointed out that even if the GM chickens carried full resistance to influenza, there are political and economic hurdles to their widespread commercial use — not least the public's aversion to GM food.

"It's the beginning of something which will require a certain number of years to see whether it is accepted by the public," said Ilaria Capua, head of virology at the Experimental Animal Health Care Institute of Venice in Legnaro, Italy.

Helen Sang, a geneticist at the Roslin Institute of the University of Edinburgh, UK, said that using their methods, it costs approximately £50,000 (CAD$79,000) to produce "a small number of stable transgenic birds you can characterize and breed from". She and Tiley argued that getting similar transgenic birds into global production would be possible because there are only a handful of companies providing purebred chicken lines.

But this approach would not be feasible in poorer countries. "This will only become affordable for the people who are well off," said Marc Van Ranst, a virologist at the Dutch-speaking Catholic University of Leuven in Belgium.

(Source: Transgenic chickens curb bird flu transmission [Nature])