ABSTRACT
Forty-two H9N2 subtype AIV strains were isolated from vaccinated commercial chickens in China from 2012 to 2015. Their HA genes had nucleotide sequence homology from 86.7% to 99.7%, and similarity to the classic vaccine strain was 88.6%-92.6%. A comparison was carried out with published HA genes (410 H9 strains) and whole genomes (306 strains) isolated in China during 2012-2015. Interestingly, 99.1% (448/452) of Chinese H9N2 AIV belonged to lineage h9.4.2, and 98.5% (445/452) of the viruses belonged to h9.4.2.5. Meanwhile, 99.6% (443/445) of lineage 9.4.2.5 viruses had PSRSSR↓GLF instead of PARSSR↓GLF motifs in the HA cleavage sites; 98.2% (444/452) of HA genes showed human receptor binding associated mutation Q226L. A total of 96.8% (337/348) of the viruses had three amino-acid deletions at 63-65 in the NA stalk, associated with enhanced virulence in chickens and mice; 97.1% (338/348) of M2 proteins had the S31N mutation associated with adamantane resistance in humans. Two H9 viruses isolated in this study were highly homologous to the human-origin H9N2 virus reported in 2013. The isolates were divided into four different genotypes (U, S, V, and W). Genotype S was the major one, accounting for 94.8% (330/348). Genotypes V and W were new reassortment genotypes, with genotype W recombined with the PB2 gene originating from the new wild waterfowl-like lineage. According to the cross-HI antibody titer data, HA gene evolution, and isolation history, the isolates were divided into A, B, and C antigenic groups successively. All the antigenic group viruses were found to circulate throughout China. This study emphasizes the importance of updated vaccine and strengthened veterinary biosecurity on poultry farms and trade markets.
Subject(s)
Genetic Variation , Influenza A Virus, H9N2 Subtype/genetics , Influenza in Birds/virology , Poultry Diseases/virology , Animals , Antigens, Viral/genetics , Antigens, Viral/immunology , Chickens , China/epidemiology , Evolution, Molecular , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Hemagglutinin Glycoproteins, Influenza Virus/immunology , Influenza A Virus, H9N2 Subtype/classification , Influenza A Virus, H9N2 Subtype/isolation & purification , Influenza in Birds/epidemiology , Phylogeny , Poultry Diseases/epidemiologyABSTRACT
Genetic variation and phylogenetic relationships of H9 avian influenza viruses (AIVs) were analyzed based on hemagglutinin (HA) gene sequences of 84 Chinese H9 reference viruses recently available in GenBank, 3 widely used vaccine strains and 29 novel isolates. The novel isolates were obtained from vaccinated poultry flocks in 11 provinces of China during 2010 to 2012. The nucleotide homologies of HA genes of these isolates ranged from 87.8-99.8%, and from 89.8-93.2% as compared with the vaccine strains. Among the 29 novel isolates and the 84 reference viruses, 69.9% of the them belonged to the lineage h9.4.2.5 and had the dominant PSRSSR↓GLF motifs in the HA cleavage sites, while 27.4% of the them belonged to the newly emerging lineage h9.4.2.6 and had the dominant PARSSR↓GLF motifs, no consecutive basic amino acids insertion, showing the characteristic feature of low-pathogenic AIV. All the lineage h9.4.2.5 viruses and 75% of the lineage h9.4.2.6 viruses had the substitution Q226L (in H3 numbering). Additional potential glycosylation site at residues 313-315 (NCS) were found merely in all the lineage h9.4.2.5 viruses. Our results demonstrated that lineage h9.4.2.5 was more dominant than other lineages as it harbored more viruses that widely distributed in China in recent years. New lineage h9.4.2.6 previously existed mainly in South China had emerged in North China. Updated vaccine and increased veterinary biosecurity on poultry farms and trade markets are needed to prevent and control avian influenza.
Subject(s)
Genetic Variation , Hemagglutinins/genetics , Influenza A virus/classification , Influenza A virus/genetics , Influenza in Birds/virology , Phylogeny , Poultry Diseases/virology , Animals , China , Influenza A virus/isolation & purification , Molecular Sequence Data , Poultry/virology , Sequence Homology, Nucleic AcidABSTRACT
Subgroup J avian leukosis virus (ALV-J), first isolated in 1989, mainly induces tumours of myeloid leukosis (ML) in meat-type chickens. In 2006, ALV-J strain SCAU-HN06 was isolated from commercial layer hens with spontaneous haemangiomas in China. To confirm its role in the induction of haemangioma, we constructed a full-length copy of the proviral genome from SCAU-HN06, recovered virus from DF-1 cells detected by enzyme-linked immunosorbent assay, characterized its growth property and investigated its pathogenicity. The recovered virus appeared to be identical to SCAU-HN06 analysed by both blast gene sequences and indirect immunofluorescence assay. It also showed similarities in growth to the parental wild-type virus in vitro. The pathogenicity of the rescued and parental virus in specific-pathogen-free White Leghorn chickens was investigated. Both SCAU-HN06 and rSCAU-HN06 could induce haemangioma, with incidence of 52% and 42.8% respectively. Overall, our findings indicated that the ALV-J strain SCAU-HN06 was the causal agent inducing haemangiomas rather than ML in certain layer chickens.
