Molecular characteristic of the hemagglutinin of highly pathogenic avian influenza A H5N6 viruses in live-poultry market, 2017–2019, Southern China

Abstract:

[Background] Since 2014, H5N6 avian influenza virus has continued to evolve in domestic poultry and live-poultry markets, becoming a major threat to human and animal health. [Objective] To analyze the molecular characteristic of hemagglutinin (HA) and neuraminidase (NA) proteins of highly pathogenic avian influenza H5N6 viruses from 19 human cases. [Methods] Whole-genome sequences of original specimen and virus isolates were obtained by next-generation sequencing technology. Pairwise sequence alignments and phylogenetic analysis were performed by Blast, Mega 6.1 and ClustalX softwares. [Results] In 2017–2019, 43 viruses were isolated from 189 H5 subtype poultry/environmental samples and 1 H5N6 patient throat swab samples, and 33 H5N6 viruses were sequenced. Based on the sequence of H5N6 virus collected on the internet, the HA gene of 93 H5N6 viruses was analyzed. Among 93 H5N6 strains, 78 belong to 2.3.4.4h, 9 belong to 2.3.4.4e, 4 belong to 2.3.4.4b, 1 belong to 2.3.4.4f, 1 belong to 2.3.4.4g. The cleavage sites of HA proteins of all 93 strains contain several basic amino acids, indicating that they are highly pathogenic avian influenza viruses. Q222 and G224 amino acids of HA protein of all 93 viruses did not mutate, which retained the binding characteristics of avian receptor α2-3 galactoside sialic acid (SAα2-3Gal); 158 sites lost glycosylation, and 124 sites showed a new potential glycosylation site. [Conclusion] From 2017 to 2019, the evolution of H5N6 virus infection in China is active, and there is obvious genetic diversity. It is necessary to strengthen the monitoring of the evolution of H5N6 viruses in China.

Key words:avian influenza virus, H5N6 subtype, hemagglutinin, molecular evolution