Thursday, November 03, 2005

Monkeys aid in a new method to speed avian flu vaccine production

The world's vaccine manufacturers will be in a race against time to forestall calamity in the event of an influenza pandemic.

But now, life-saving inoculations may be available more readily than before, thanks to a new technique to more efficiently produce the disarmed viruses that are the seed stock for making flu vaccine in large quantities.

The work is especially important as governments worldwide prepare for a predicted pandemic of avian influenza.

Writing in the online edition of the Proceedings of the National Academies of Science (PNAS) , a team of researchers from UW-Madison and the University of Tokyo report a new way to generate genetically altered influenza virus.

The lab-made virus — whose genes are manipulated to disarm its virulent nature — can be seeded into chicken eggs to generate the vaccine used in inoculations, which prepare the human immune system to recognise and defeat the wild viruses that spread among humans in an epidemic or pandemic.

In their report, a team led by UW-Madison virologists Yoshihiro Kawaoka and Gabriele Neumann, describes an improved `reverse genetics' technique that makes it easier to make a seed virus in monkey kidney cells, which, like tiny factories, churn out millions of copies of the disarmed virus to be used to make vaccines.

In nature, viruses commandeer a cell's reproductive machinery to make new virus particles, which go on to infect other cells and make yet more virus particles.

Non-virulent viruses that serve as the raw material for vaccines are made by vaccine makers using a monkey kidney cell line.

According to the University of Wisconsin-Madison press release, the technique reported by the team improves upon a previous reverse genetics method (developed by Kawaoka's group in 1999) by significantly reducing the number of plasmid vectors required to ferry viral genes into the monkey kidney cells used to produce the virus particles to make vaccines. "Compared with other types of cells, which are not approved for vaccine production, it is not always easy to introduce plasmids into the monkey kidney cells, which are approved for such use," says Kawaoka, an influenza expert and a professor of pathobiological sciences in UW-Madison's School of Veterinary Medicine.

Because they are not known to carry any unknown infectious agents and do not cause tumours, monkey kidney cells are used routinely for generation of seed strains for vaccine production.

Story here.

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