What makes H5N1 Avian influenza

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What makes H5N1 Avian influenza Avian?(why not
H5N1 Tiger influenza?)

• Finding mutations that limit the transmission of
  avian influenza to other speciesespecially
  humans
• (But also tigers).

Tad Davenport CSE140 March 18,2013
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H5N1 Influenza Background
H5N1 Avian Influenza Bird flu Extremely
prevalent in birds But it is rarely transmitted
to humans However, upon transmission it has a
High mortality rate (60) http//en.wikipedia.o
rg/wiki/Influenza_A_virus_subtype_H5N1
From gridpp.ac.uk
Seasonal Influenza H1N1 and H3N2 3,000 50,000
deaths/year (US) http//www.cdc.gov/flu/about/dise
ase/us_flu-related_deaths.htm
Pandemic Influenza e.g. The Spanish Flu 10-20
of those infected died 50-100 Million
deaths http//en.wikipedia.org/wiki/1918_flu_pande
mic
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Research Question
Why is bird flu poorly transmitted to humans?
Are H5N1 viruses that infect humans (and other
mammals) different from H5N1 viruses that infect
birds?
If so where do these differences occur?
Approach Focus on Hemagglutinin (HA) sequences
(because the virus uses this protein to enter
host cells) Find the most common HA sequence for
each species, a.k.a. the consensus
sequence Compare the consensus sequences for all
available species, find the amino acid changes
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Program Output Mutations At HA Receptor Binding
Site
Changes in Human H5N1 relative to Avian H5N1
isolates ('N', 170, 'S'), ('A', 171, 'T')
Amino Acid Number
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Interpretation and Conclusions
These naturally-occurring mutations occur at a
site (N158D) that has been previously shown to be
important for adaptation of H5N1 to be
transmissible between ferrets in laboratory
experiments. (Imai, M. et al. Nature 2012).
Because these mutations occur in multiple
species, this suggests that they have been
selected for in multiple, independent
transmission events
They occur at the receptor binding site!
All of these suggest that they are functionally
important mutations that may limit transmission
between birds and mammals.
http//www.virology.ws/2012/06/21/influenza-h5n1-v
irus-versus-ferrets-round-two/