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Haemagglutinin mutations responsible for the binding of H5N1 influenza A viruses to human-type receptors



H5N1 influenza A viruses have spread to numerous countries in Asia, Europe and Africa, infecting not only large numbers of poultry, but also an increasing number of humans, often with lethal effects1,2. Human and avian influenza A viruses differ in their recognition of host cell receptors: the former preferentially recognize receptors with saccharides terminating in sialic acid-α2,6-galactose (SAα2,6Gal), whereas the latter prefer those ending in SAα2,3Gal (refs 3–6). A conversion from SAα2,3Gal to SAα2,6Gal recognition is thought to be one of the changes that must occur before avian influenza viruses can replicate efficiently in humans and acquire the potential to cause a pandemic. By identifying mutations in the receptor-binding haemagglutinin (HA) molecule that would enable avian H5N1 viruses to recognize human-type host cell receptors, it may be possible to predict (and thus to increase preparedness for) the emergence of pandemic viruses. Here we show that some H5N1 viruses isolated from humans can bind to both human and avian receptors, in contrast to those isolated from chickens and ducks, which recognize the avian receptors exclusively. Mutations at positions 182 and 192 independently convert the HAs of H5N1 viruses known to recognize the avian receptor to ones that recognize the human receptor. Analysis of the crystal structure of the HA from an H5N1 virus used in our genetic experiments shows that the locations of these amino acids in the HA molecule are compatible with an effect on receptor binding. The amino acid changes that we identify might serve as molecular markers for assessing the pandemic potential of H5N1 field isolates.

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We thank K. Wells for technical assistance, and J. Gilbert for editing the manuscript. The NIMR contributors were responsible for the structural studies and for HA sequencing. This work was supported by CREST (Japan Science and Technology Agency); by grants-in-aid from the Ministry of Education, Culture, Sports, Science and Technology, Japan; by the Ministry of Health, Labour and Welfare, Japan; and by grants from the NIH, NIAID. Structural studies were supported by the UK MRC and by an International Partnership Research Award in Veterinary Epidemiology of the Wellcome Trust. Author Contributions S.Y., Y.S., T.S., M.Q.L., C.A.N., Y.S.T., Y.M., T.H., T.S., M.K, T.U., T.M., Y.L., A.H. and Y.K. were responsible for the virological studies. L.F.H., D.J.S., R.J.R., S.J.G. and J.J.S. were responsible for the structural studies.

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Competing interests

Coordinates for the H5 structure have been deposited in the Protein Data Bank under accession code 2IBX. Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

Correspondence to Yoshihiro Kawaoka.

Supplementary information

  1. Supplementary Figures

    This file contains Supplementary Figures 1–4. Supplementary Figure 1: Phylogenetic relationships of HA genes from H5N1 influenza viruses. Supplementary Figure 2: Receptor specificity of H5N1 viruses. Supplementary Figure 3: Specificity of the receptor assay. Supplementary Figure 4: Effect of HA mutations on SAα2,6Gal recognition. (PPT 6961 kb)

  2. Supplementary Tables

    Supplementary Table 1: H5N1 viruses used in this study. Supplementary Table 2: Data collection and refinement statistics (DOC 82 kb)

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Further reading

Figure 1: Receptor-binding activity of H5N1 viruses.
Figure 2: Effect of HA mutations on the host cell receptor preference of the VN1194HA.
Figure 3: Effect of mutations responsible for SAα2,6Gal recognition by clade-1 HAs on a clade-2 HA.
Figure 4: Crystal structure of VN1194 H5 HA and the location of mutations conferring SAα2,6Gal-binding capacity.


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