ABSTRACT
Objective:To analyze phylogenetic structure and molecular characteristics of H5N6 avian influenza virus (AIVs) isolated from live poultry market (LPM).Methods:Oropharyngeal and cloacal swabs from poultry, and environmental samples were collected from LPM in Urumqi in December 2018, AIVs were isolated and identified by inoculation of chicken embryo, hemagglutination test and RT-PCR, the viral whole genome was amplified with the universal primers of influenza A virus, and then sequenced, pairwise sequence alignments, phylogenetic and molecular characteristics analysis were performed by BLAST, Clustal W, MEGA-X and DNAStar software.Results:Six strains of H5N6 AIVs were isolated from poultry samples, the identity between the viral genes was high (99.4%-100.0%), so the isolates were the same source. BLAST analysis revealed that the viral NP sequence had the highest identity (99.7%) with H5N6 AIVs isolated from poultry in Suzhou, while the sequence of the remaining 7 viral genes had the highest identity (99.0%-100.0%) with H5N6 AIVs isolated from environment in Guangdong during 2017 to 2018. Phylogenetic analysis showed that the viral HA belonged to Clade 2.3.4.4C, and the viral HA, NA, PB1, PA, NP, and MP were all clustered together with H5N6 AIVs isolated from mink in Eastern China in 2018, while the PB2 and NS were clustered together with H5N6 AIVs isolated from environment in Guangdong from 2017 to 2018. The HA cleavage site contained multiple basic amino acid residues, which was highly pathogenic AIVs (HPAIVs). S137A and T160A mutations of HA could increase binding to human-type receptor SAα2, 6-Gal. Additionally, the viral multiple mutations, including 59-69 deletion in NA, the L89V, G309D, R477G, I495V, I504V, D391E, and A661E in PB2, as well as the P42S, D92E, and 80-84 deletion in NS1, could enhance the viral virulence and pathogenicity to mammals. Conclusions:The 6 strains of H5N6 HPAIVs isolated from LPM have relatively close genetic relationship with H5N6 AIVs isolated from mink in Eastern China and environment in Guangdong during 2017 to 2018, the viral multiple mutations could increase its pathogenicity to mammals, which could pose a potential risk to public health.
ABSTRACT
Objective:To analyze the complete genome sequence and phylogenetic structure of a wild bird-derived H1N1 avian influenza virus (AIV) in the northern Tianshan Mountain.Methods:In November 2018, 320 samples of fresh wild bird feces were collected from several reservoirs in the middle part of northern Tianshan Mountain. Chicken embryo inoculation test, hemagglutination inhibition test and RT-PCR with PB1 universal primer were used to isolate and identify AIVs. Eight fragments of the viral genome were amplified with the universal primers of influenza A virus and the whole viral genome was sequenced. Pairwise sequence alignments and analysis of phylogenetic and molecular characteristics were performed by BLAST, Clustal W, MEGA7.0 and MegAlign software. Results:Influenza viruses were isolated and identified from six samples of wild bird feces with a positive rate of 1.88%. One of them was H1N1 AIV, named A/wild bird/Xinjiang/010/2018 (H1N1) (XJ-H1N1). The eight gene segments of XJ-H1N1 were all derived from AIVs isolated from wild ducks of Anseriformes. The surface genes of HA and NA were Eurasian lineages and derived from H1N1 isolated from Mongolian Anas platyrhynchos and H3N1 isolated from Bangladesh wild duck, respectively. The six internal genes were derived from H6N8 isolated from Anas strepera in Siberia, H7N3 isolated from Anas clypeata and teal in Egypt, and H7N5 isolated from wild birds such as Anas platyrhynchos in the Netherlands. The HA cleavage site of XJ-H1N1 contained only one basic amino acid, suggesting that it was a low pathogenic AIV. Amino acids at positions 190 and 225 of HA receptor binding sites were E and G (H3 count), which could bind both α2, 3 galactoside sialic acid (SAα2, 3Gal) and SAα2, 6Gal receptors. T200A and E227A mutations in HA amino acid sequences and P42S mutation in NS1 amino acid sequences could all enhance the replication ability and pathogenicity of the virus in mammalian cells. Conclusions:A low pathogenic H1N1 AIV, XJ-H1N1, was isolated from wild birds in the northern Tianshan Mountain, resulting from multiple reassortments of AIVs carried by migrating wild ducks. The replication capacity and pathogenicity of XJ-H1N1 in mammalian cells might be enhanced. Moreover, the virus could bind both SA 2-3gal and SA 2-6gal receptors.