Highly conserved domains in hemagglutinin of influenza viruses characterizing dual receptor binding

The hemagglutinin (HA) of influenza viruses in itiates virus infection by binding receptors on host cells. Human influenza viruses preferenti ally bind to receptors with α2,6 linkages to gala ctose, avian viruses prefer receptors with α2,3 linkages to galactose, and swine viruses favor both types of receptors. The pandemic H1N1 2009 remains a global health concern in 2010. The novel 2009 H1N1 influenza virus has its ge netic components from avian, human, and sw ine viruses. Its pandemic nature is characterized clearly by its dual binding to the α2,3 as well as α2,6 receptors, because the seasonal human H1N1 virus only binds to the α2,6 receptor. In pr evious studies, the informational spectrum me thod (ISM), a bioinformatics method, was appli ed to uncover highly conserved regions in the HA protein associated with the primary receptor binding preference in various subtypes. In the present study, we extended the previous work by discovering multiple domains in HA associa ted with the secondary receptor binding prefer ence in various subtypes, thus characterizing the distinct dual binding nature of these viruses. The domains discovered in the HA proteins were mapped to the 3D homology model of HA, which could be utilized as therapeutic and diag nostic targets for the prevention and treatment of influenza infection.