An experiment to reconstruct
the deadly 1918 flu virus has given a new
insight into how the infection took hold.
Scientists discovered a severe
immune system reaction was triggered when
mice were infected with the recreated virus.
The US team believe the extreme
immune response could have provoked the body
to begin killing its own cells, making the
flu even deadlier.
The study, published in Nature,
may aid the hunt for new treatments. The 1918
pandemic took about 50 million lives.
The devastating infection,
which is thought to have originated in birds,
left young adults worst hit.
Scientists in the US have
reconstructed the H1N1 virus in a bid to better
understand how it became such an effective
killer - and to also bolster knowledge in
the face of current H5N1 bird flu threat.
The researchers infected
mice with the recreated influenza virus.
Through functional genomic
analysis they discovered that the mice's immune
systems responded fiercely to the infection
and remained active until the animals' deaths
several days later.
At the same time, the animals
also suffered the severe lung disease that
is characteristic of the virus.
Understanding H5N1
Dr John Kash, lead author
of the study and assistant professor of microbiology
at the University of Washington, said: "What
we think is happening is that the host's inflammatory
response is being highly activated by the
virus, and that response is making the virus
much more damaging to the host.
"The host's immune system
may be overreacting and killing off too many
cells, and that may be a key contributor to
what makes this virus more pathogenic."
Dr Christopher Basler, a
co-author from Mount Sinai School of Medicine,
New York, said: "Our next step is to repeat
these experiments, but deconstruct what the
immune system is doing so that we can understand
why it is reacting so strongly, yet failing
to fight the infection."
The researchers said understanding
how the virus works would help in fight against
influenza.
Dr Basler said: "This could
help us develop more targeted therapies to
combat pathogenic infections, including different
types of influenzas or perhaps avian influenza."
Paul Hunter, professor of
health protection from the University of East
Anglia, said: "People who have died from the
current form of bird flu have died in the
same sort of fashion as the people who died
during the 1918 pandemic. It is an extraordinarily
unpleasant death.
"Clearly the difference between
the virus now and the one around in 1918 is
that the current one has yet to develop the
ability to spread swiftly from person to person.
"It is very important to
study the 1918 flu to understand the current
avian flu virus."
