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. 2020 Dec;9(1):1793-1803.
doi: 10.1080/22221751.2020.1797542.

Evolution and extensive reassortment of H5 influenza viruses isolated from wild birds in China over the past decade

Yanfang Cui  1 , Yulei Li  1 , Minghui Li  1 , Lu Zhao  1 , Deli Wang  1 , Jingman Tian  1 , Xiaoli Bai  1 , Yanpeng Ci  1 , Shanshan Wu  1 , Fei Wang  1 , Xiaomei Chen  1 , Shujie Ma  1 , Zhiyuan Qu  1 , Cen Yang  1 , Liling Liu  1 , Jianzhong Shi  1 , Yuntao Guan  1 , Xianying Zeng  1 , Guobin Tian  1 , Pengfei Cui  1 , Guohua Deng  1 , Yongping Jiang  1 , Pucheng Chen  1 , Jinxiong Liu  1 , Xiurong Wang  1 , Hongmei Bao  1 , Li Jiang  1 , Yasuo Suzuki  2   3 , Chengjun Li  1 , Yanbing Li  1 , Hualan Chen  1
Affiliations

Evolution and extensive reassortment of H5 influenza viruses isolated from wild birds in China over the past decade

Yanfang Cui et al. Emerg Microbes Infect. 2020 Dec.

Abstract

Lethal infection of wild birds with different subtypes of H5 viruses continuously occur. To investigate the genetic evolution and pathogenicity of H5 viruses in wild birds, we performed a detailed genetic and biologic analysis of 27 viruses, including H5N1, H5N2, H5N6, and H5N8 subtypes, that were responsible for avian influenza outbreaks in wild birds in China over the past decade. We found that these 27 viruses, bearing different clades/subclades of HA, were complicated reassortants and formed 12 different genotypes. Ten of the viruses tested were highly pathogenic in chickens, but showed distinct pathotypes in ducks and mice. Five of these 10 viruses, which were all from clade2.3.4.4, could bind human-type receptors. Our findings reveal the diversity of the genetic and biologic properties of H5 viruses circulating in wild birds and highlight the need to carefully monitor and evaluate the risks these viruses pose to animal and public health.

Keywords: H5 subtype; Influenza A virus; reassortant; virulence; wild birds.

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Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

Figure 1.
Figure 1.
Geographical locations and bird species involved in the wild bird outbreaks caused by different genotypes of H5 viruses.
Figure 2.
Figure 2.
Phylogenetic analysis of H5 wild bird viruses and genotypes. The Maximum Clade Credibility (MCC) tree of the HA gene was constructed by using the package BEAST (v1.8.4). The clades shown in different colours in the tree were annotated by using FigTree (v1.4.4) (a), and the origins of each gene segment are indicated by different coloured bars (b). Phylogenetic trees with complete information are provided as Supporting Figures S1 and S2.
Figure 3.
Figure 3.
Diagrammatic representation of the formation of different H5 reassortants. Viral particles are represented by coloured ovals containing horizontal bars representing the 8 gene segments (from top to bottom: PB2, PB1, PA, HA, NP, NA, M, and NS). Segments in descendant viruses are coloured according to their corresponding source virus (top) to illustrate gene ancestry through reassortment events. Possible donor viruses are adjacent to arrow tails; arrowheads point to the resulting reassortants. The timeline in the middle indicates the possible time of virus emergence or reassortment events. The tMRCA was estimated by using the Bayesian Markov chain Monte Carlo method in the BEAST v1.8.4 software package.
Figure 4.
Figure 4.
Receptor binding properties of H5 wild bird viruses. Binding properties were analyzed by using two types of receptors, α-2,6-linked SAs (human-type receptors) and α-2,3-linked SAs (avian-type receptors).
Figure 5.
Figure 5.
Replication and virulence of H5 wild bird viruses in mice. (a) Viral titres in organs of mice that were euthanized on day 3 post-inoculation with 106EID50 of the test virus. (b) MLD50 of each test virus.
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