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Hemagglutinin Receptor Binding Avidity Drives Influenza A Virus Antigenic Drift
Speaker: Chien‐Sin Chen
Advisor: Li‐Kwan Chang Ph.D.
Scott E. Hensley, Suman R. Das, Adam L. Bailey, Loren M. Schmidt, Heather D. Hickman, Akila Jayaraman, Karthik Viswanathan, Rahul Raman, Ram Sasisekharan, Jack R. Bennink, Jonathan W. Yewdell
Science 326: 734‐6, 2009
We might suffer from needle every year
http://www.flickr.com/photos/ifrc/2323786362/http://www.canada.com/health/plans+autumn+swine+vaccination+campaign/1774845/story.html
Flu: pandemic and seasonal
• Worldwide
• Several years or decades
http://www.who.int/csr/don/h1n1_20090706a_1100.png
http://www.ifpma.org/Influenza/index.aspx?005_Influenza_Vaccines/001a_Influenza_Vaccines.html
• Local
• Every year
Influenza virus
• A, B and C type
• “‐” ssRNA genome
• Diameter: 80 ~ 120 nm
http://www.infection-research.de/news/detail/pressrelease/comparing_swine_and_seasonal_flu_in_ferrets
http://www.ifpma.org/influenza/index.aspx?25
Nat Rev Microbiol 3: 591-600, 2005
• Infect respiratory tract
• HA and NA determine its antigenicity and infection specificity
HA and NA: gate between virus and host
• HA: binds sialic acid
• NA: cuts sialic acid
• Sialic acid: cell surface glycan
http://www.flutrackers.com/forum/showthread.php?p=338891
RBC precipitate
hemagglutinate
HA and NA: antigenic shift and drift
mildly and gradually abruptly
http://www.latebytes.nl/archives/informatie-en-design/
Avidity, the combined strength• For same substance, binding ability is proportional to binding avidity
http://rheuma.bham.ac.uk/teaching/immunity2/igg_classes.htm
Mutants (G1) escape from antibody by raising cell binding avidity
Polyclonal antibody (pAb) still binds mutated HA
Passaging mutant (G1) virus to naïve mice selects mutants (G2) with additional mutation on HA
decreasing cell binding avidity
W
1
2
E156KE246GE158K
Mutation on E156K of HA enhance cell binding avidity and simultaneously modulate antigenicity
E156K series
as bad as wild type
not too bad
Mutants (G3), re‐selected through vaccinated mice, have improved cell binding and pAb escape ability
W
1
2
3
G1
G2
G3
G1
G2
G3
Hypothesis:new model of antigenic drift
• Host immunity modulates cell binding avidity as primary evolutional response, and antigenicity change is by‐product
• Cell binding avidity fluctuates but antibody escape ability is steady raised
E156KE156KE158KE246G