Evolutionary dynamics of the H7N9 avian influenza virus based on large-scale sequence analysis

PLoS One. 2019 Aug 12;14(8):e0220249. doi: 10.1371/journal.pone.0220249. eCollection 2019.

Abstract

Since 2013, epidemics caused by novel H7N9 avian influenza A viruses (AIVs) have become a considerable public health issue. This study investigated the evolution of these viruses at the population level. Compared to H7 and N9 before 2013, there were 18 and 24 substitutions in the majority of novel H7N9 AIVs, respectively. Nine of these in HA and six in NA were rare before 2013, and four of these in HA and two in NA displayed host tropism. S136(128)N and A143(135)V are located on the receptor binding sites of the HA1 subunit and might be important factors in determining the host species of novel H7N9 AIV. On an overall scale, the evolution of H7 and N9, both in terms of time distribution and host species, is under negative selection. However, both in HA and NA, several sites were under positive selection. In both the overall epidemics and the human-derived H7N9 AIVs, eight positive selection sites were identified in HA1, with some located within the known antigen epitopes or the receptor binding site(RBS) domain. This may induce variations in H7N9 AIV with positive selection. It is necessary to strengthen the surveillance of novel H7N9 AIVs, both in human and bird population to determine whether a new virus has emerged through selection pressure and to prevent future epidemics from occurring.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Evolution*
  • Birds / virology*
  • Hemagglutinin Glycoproteins, Influenza Virus / genetics*
  • High-Throughput Nucleotide Sequencing / methods*
  • Influenza A Virus, H7N9 Subtype / classification
  • Influenza A Virus, H7N9 Subtype / genetics*
  • Influenza A Virus, H7N9 Subtype / isolation & purification
  • Influenza in Birds / virology*
  • Orthomyxoviridae Infections / virology*

Substances

  • Hemagglutinin Glycoproteins, Influenza Virus

Grants and funding

This research was funded by the National Natural Science Foundation of China (grant No. 81872673), the National Key Research and Development Program of China (grant No. 2017YFC1200203), the Original Research Support Project of Fudan University (grant No. IDF201011) to LJ. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.