The index influenza A virus subtype H5N1 isolated from a human in 1997 differs in its receptor-binding properties from a virulent avian influenza virus

¹ Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
² Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corporation, Saitama 332-0012, Japan
³ Laboratory of Veterinary Microbiology, Division of Veterinary Science, Graduate School of Agriculture and Biological Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan
⁴ Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, USA

Correspondence
Taisuke Horimoto
horimoto@ims.u-tokyo.ac.jp

To gain insight into the events that occur when avian influenza viruses are transmitted to humans, the receptor-binding properties of the index H5N1 influenza virus isolated from a human in 1997 and the A/turkey/Ontario/7732/66 (H5N9) virus were compared, by using a haemadsorption assay. Cells expressing the haemagglutinin (HA) of the human isolate were adsorbed by both chicken red blood cells (RBCs) and human RBCs; those expressing the avian virus HA were only adsorbed by chicken RBCs. These results indicate that human and avian influenza virus H5 HAs differ in their recognition of sialyloligosaccharides on the RBCs of different animal species. Mutational analyses indicated that differences in both the oligosaccharide chains and in the amino acid sequences around the HA receptor-binding site were responsible for this difference in receptor binding. These data further support the concept that alteration in receptor recognition is important for replication of avian viruses in humans.

A figure showing the haemadsorption of the wild-type and selected mutant HAs is available as supplementary data in JGV Online.