Step Toward Universal Flu Vaccine Shows Promise In Animal Tests

Date: May-23-2013A new approach for creating immunity against the flu virus that produces a stronger immune reaction and protects against more strains
than the current vaccines, has shown promising results in animal tests. The result is a step forward in the development of a universal flu vaccine
say the researchers behind it.

Every year, flu vaccine developers race against time to produce vaccines that match circulating viruses. The challenges they face include the fact the
data they are working with is out of date almost as soon as it reaches them, and the chance that unexpected strains of flu virus will emerge after
the decision has been made as to which strains to base the next vaccine on.

A universal flu vaccine would protect against most if not all strains of flu without the need to have annual jabs.

The idea for the new vaccine approach is the work of scientists at the National Institute of Allergy and Infectious Diseases (NIAID) in the US, who
write about it and the results of the tests in mice and ferrets, in a study published online this week in the journal Nature.

For their study, lead author Masaru Kanekiyo and colleagues, tested a new type of vaccine based on the protein ferritin which can self-assemble
into nanoparticles, tiny sub-microscopic pieces that are some 200 times smaller than the thickness of human hair.

They genetically fused the ferritin with hemagglutinin (HA), the protein found on the surface of the influenza virus to produce a nanoparticle with
eight viral spikes protruding from it.

They then used this structure as the basis for the antigen (the bit that the host immune system responds to in making antibodies) for making an
experimental vaccine that used HA from a 1999 strain of H1N1 flu virus.

When they tested the new vaccine in mice, they found that a single dose produced an immune reaction that
was equivalent to that of two doses of current seasonal flu vaccine.

The new vaccine was also effective at producing immunity against a wider range of H1N1 flu virus strains than the current seasonal flu
vaccine.

In another set of tests, this time with ferrets, the researchers found the new vaccine protected the animals from infection with a 2007 strain of
H1N1 flu virus. This was an interesting result because the new vaccine was not designed to protect specifically against this
strain.

And, compared to controls that had not received the new vaccine, immunized ferrets had significantly lower levels of flu virus one day after being
exposed to it.

The researchers suggest the new vaccine works because it causes the host immune system to make antibodies to those parts of the flu virus that
don't change from strain to strain.

They say while further tests should now be done, it looks like the new approach could lead to a universal vaccine that protects more broadly
against different strains of flu. It could also work for developing vaccines against other infectious diseases, they note.

Last year, another group of scientists also took a step closer to a universal flu vaccine when they solved the co-crystal structure of a human antibody that can neutralize influenza
viruses in a unique way.

Written by Catharine Paddock PhD

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