Proteinquakes in the Evolution of Influenza Virus Hemagglutinin (A/H1N1) under Opposing Migration and Vaccination Pressures

Figure 1

HA (1–565) is structurally separated into head HA1 (18–342) and stalk HA2 (344–565) parts, the latter being attached to the membrane. The head hydroprofiles of the two historic HA strains, Fort Dix 1976 (Genbank ACU80014) and Puerto Rico 1934 (P03452), are compared with a modern (vaccination moderated) strain, New York ACQ84467. The origin of the severity of the 1976 Fort Dix strain is explained by its strongly hydrophobic head amino acid content, especially near site 110. The advent of swine flu (2001–2007) and the response (2009–2011) to its vaccination program flattened (smoothed) current strains (like New York 2009) and reduced their virulence.