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Friday 28th October 2016

Bird flu mutations predictable?

11th September 2007

Scientists in the United States say they have developed a way to produce vaccines which may predict the mutation of a lethal influenza virus before it emerges.


The team, collaborating between the National Institutes of Health (NIH) and Emory University School of Medicine, published findings in the journal Science in August, showing how they had created mutations in the part of the H5N1 avian influenza virus that would direct it to infect bird or human hosts.

Led by vaccine specialist Gary Nabel of the NIH's National Institute of Allergy and Infectious Diseases (NIAID), the team may now be in a position to predict future strains of H5N1 before they emerge, including strains which may become easily transmissible between humans.

So far, the 328 humans who have been confirmed infected with H5N1 since 2003 have had some contact with sick poultry. Of these, 200 have died.

Experts fear the virus could mutate into a form easily transmissible between humans and spark a pandemic, killing millions globally.

NIAID director Anthony S. Fauci said the research was significant, because it could help to contain a pandemic in its early stages, as experts could begin to consider the design of potential new vaccines and therapeutic antibodies pre-emptively.

Usually, samples of existing influenza virus strains are needed to prepare a vaccine. Inactivated forms of the virus are delivered in immunisation programmes, and the person being immunised is able to make antibodies which will help repel the virus if they are later exposed to it.

However, viruses are always mutating, so updated forms of vaccine must be produced to keep up protection levels. This makes it difficult to predict how effective a vaccine made today will be against a virus that emerges tomorrow.

Nabel's team began by focusing only on the mutations that affect how H5N1 viruses recognize and enter human cells, which is different from how it latches on to bird cells, using clues from the virus that caused the devastating 1918 flu pandemic.

They succeeded in identifying some of the genetic changes that might have to happen for H5N1 to infect humans, and again for it to become easily transmissible between humans.

They produced artificially mutated viruses in the laboratory, and discovered a broadly reactive antibody in mice which could neutralise these artifical strains in both humans and birds.

Nabel said his team's research built on studies of influenza proteins by structural biologists, which enabled them to target a critical region of the virus that affected its mutations.

He said such a structure-based vaccine design might enable the team to respond to the future threat of a pandemic before the first outbreak occurred.

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