Structural basis for preferential avian receptor binding by the human-infecting H10N8 avian influenza virus.

Since December 2013, at least three cases of human infections with H10N8 avian influenza virus have been reported in China, two of them being fatal. To investigate the epidemic potential of H10N8 viruses, we examined the receptor binding property of the first human isolate, A/Jiangxi-Donghu/346/2013 (JD-H10N8), and determined the structures of its haemagglutinin (HA) in complex with both avian and human receptor analogues. Our results suggest that JD-H10N8 preferentially binds the avian receptor and that residue R137-localized within the receptor-binding site of HA-plays a key role in this preferential binding. Compared with the H7N9 avian influenza viruses, JD-H10N8 did not exhibit the enhanced binding to human receptors observed with the prevalent H7N9 virus isolate Anhui-1, but resembled the receptor binding activity of the early-outbreak H7N9 isolate (Shanghai-1). We conclude that the H10N8 virus is a typical avian influenza virus.