An airborne transmissible avian influenza H5 hemagglutinin seen at the atomic level.

Abstract

Recent studies have identified several mutations in the hemagglutinin (HA) protein that allow the highly pathogenic avian H5N1 influenza A virus to transmit between mammals by airborne route. Here, we determined the complex structures of wild-type and mutant HAs derived from an Indonesia H5N1 virus bound to either avian or human receptor sialic acid analogs. A cis/trans conformational change in the glycosidic linkage of the receptor analog was observed, which explains how the H5N1 virus alters its receptor-binding preference. Furthermore, the mutant HA possessed low affinities for both avian and human receptors. Our findings provide a structural and biophysical basis for the H5N1 adaptation to acquire human, but maintain avian, receptor-binding properties.