New method to test vaccines against flu strains

March 18th, 2009 - 2:03 pm ICT by IANS  

Washington, March 18 (IANS) A computerised method could more accurately and speedily test efficacy of proposed flu vaccines against multiple strains of the disease.
Avian flu or bird flu is a particularly deadly type of flu that is transmitted from birds to humans. It hasn’t yet evolved into a form that can be transmitted readily between humans, but scientists and health authorities are trying to prepare for a potential outbreak.

Because the virus mutates continually, creating a vaccine in advance is problematic. For example, scientists have already found that a vaccine designed for the 1997 strain of bird flu does not work against a 2003 strain.

Influenza viruses are like chameleons. They constantly change the patterns on their outer surface to avoid being targeted by antibodies. This rapid mutation rate is the reason flu vaccines must be changed annually.

Rice University’s Michael Deem, the scientist who led the project, said “current vaccines contain only a single version of a given flu subtype. We wanted to gauge the effectiveness of a vaccine that contained multiple versions of a given subtype”.

World health authorities currently test the efficacy of proposed flu vaccines using either ferrets, which can contract the same forms of flu as people, or genetic assays. Rice’s new computerised method could be a cheaper and faster alternative.

With the new method, flu virus mutations are assigned numerical scores. Deem, professor of bioengineering, physics and astronomy, and colleagues developed the method so they could assign a number that captured the amount of difference or similarity between strains.

The method can also be used to test how effective a vaccine will be against divergent strains. To verify this, the team checked their results against flu vaccine data collected by the World Health Organisation from 1971 to 2004.

“For seasonal influenza, we validated our model against observational data compiled by the World Health Organization’s Global Influenza Surveillance Network,” Deem said, according to a Rice release.

“We also ran tests against bird flu data. We found that multiple-component bird flu vaccines appeared to be helpful in controlling the simultaneous multiple introduction of bird flu strains.”

The results are also slated to appear in the forthcoming book Influenza: Molecular Virology.

Deem will present the group’s results on Thursday at the American Physical Society’s 2009 meeting in Pittsburgh.

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