[Receptor sialylsugar chains as determinants of host range of influenza viruses]

All types of the hemagglutinin(HA) of human, pig, horse and aq. bird influenza A viruses, recognize sialyl lacto-series type I and II sugar chains(Sialic acid(SA) alpha 2-3(6)Gal beta 1-3(4) GlcNAc beta 1-) in glycoproteins and glycolipids in the target cells as common receptor molecules. Avian and equine influenza viruses preferentially binds the terminal sialic acid alpha 2-3Gal(SA2-3Gal) linkage, while human influenza viruses preferentially bind the SA2-6Gal linkage. SA distribution in animal species influence influenza virus host range. Swine trachea has both receptors for avian influenza viruses (SA2-3Gal specific) and for human influenza viruses(SA2-6Gal specific). In the case of horses, a virus with an HA recognizing Neu5Ac2-6Gal, but not Neu5Ac2-3Gal, failed to replicate in horses, while one with an HA recognizing the Neu5Gc2-3Gal moiety replicated in horses. The abundance of the Neu5Gc2-3Gal moiety in epithelial cells of horse trachea supports that recognition of Neu5Gc2-3Gal moiety is critical for viral replication in horses. The Neu5Gc2-3Gal is also associated with viral replication in duck intestine, primarily in the crypt epitherial cells. Such recognition, together with biochemical evidence of Neu5Gc in crypt cells, correlated exactly with the ability of the virus to replicate in duck colon. These results indicate the evidence of biologic effect of different sialic acid species in different animals.