More haste less speed for Imugene bird flu vaccine, but project still alive

A development glitch may be responsible for the failure of a prototype vaccine against deadly avian influenza, developed by Sydney veterinary vaccine company Imugene (ASX:IMU).

The vaccine against the H5N1 strain of the bird flu that ravaged poultry farms in Vietnam and Thailand early this year, did not elicit a sufficiently strong antibody response to protect chickens infected with the deadly virus, according to Imugene's Executive Chairman, Mr Graham Dowland.

Although researchers were still analysing the problem, Dowland said it appeared to lie in the construction of the antigen-coding gene inserted into Imugene's proprietary adenoviral delivery vector system.

The unique, CSIRO-developed vector system has previously been used successfully in developing a strongly protective prototype vaccine against the virus disease Porcine Reproductive and Respiratory Syndrome.

For this reason, the company believes the problem lies in the gene construct, not the delivery system, or any inherent problem with the deadly influenza virus strain responsible for bird 'flu.

Efforts to develop a conventional vaccine against the H5N1 strain have been frustrated because the virus is so lethal that it kills the embryonated eggs traditionally been used to brew attenuated-virus influenza vaccines.

Imugene remained optimistic that its technology would deliver an effective vaccine. "We're going to go back and do it again, but this time we'll add a few extra steps to ensure it works," said Dowland. "It was a bit of a rush to get the trial done - we were under pressure from the Australian government, and governments overseas."

Dowland said Asian governments were anxious to procure a new vaccine to protect their poultry industries against any new outbreak of the virus, and the Australian Government was keen to protect the nation's own poultry industry if it entered Australia.

It was likely that Asian governments would legislate to build up stockpiles of any successful avian influenza vaccine, against the possibility of future outbreaks.

He said a new prototype vaccine would probably not be ready for testing before the first quarter of 2005.

Of the failure of the first prototype, Dowland said, "It's a disappointing result, but the project is still very much alive. It's actually good to get a clear-cut result that says it's not working, so we can move on."