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| The Sequence Analysis and Pathogenicity for a Virulent Newcastle disease virus Strain from Wildfowl |
| 2, 2, 2, 2 |
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Abstract Newcastle diseases (ND) is one of the two serious diseases of poultry, Newcastle diseases virus (NDV) is the pathogen of the disease. To understand the molecular properties, pathogenicity of wildfowl NDV and its relationship with poultry NDV, a NDV strain, NDV2, was isolated from wildfowl in 2011 and confirmed virulent using standard biological virulence tests. Nine pairs of specific primers were designed from sequence of NDV deposited in GenBank, and the complete genomic sequence of NDV2 strain was 15 192 nt(GenBank accession No. KF306265) and its genome comprised six ORFs, namely, encoded nucleocapsid protein(NP), phosphoprotein(P), matrix protein(M), fusion protein(F), haemagglutinin-neuraminidase(HN) and large protein(L). The lengths of each gene were respectively 1 753, 1 451, 1 241, 1 792, 2 004 and 6 703 nt. NDV2 was classifid as ClassⅡ, genotype Ⅶ. Comparison of the homologies of each protein showed that NDV2 was highly homologous to several domestic genotype Ⅶ strains, such as Egret.GX.11, Duck.WF.00 and Goose.GD450.11 in recent years, which was far higher than strains of other regions and other genotypes.These results suggested that NDV2 had high affinity to domestic strains. The JS10 strain of ClassⅠ was the least homologous to NDV2. Sequence analysis of the F gene showed that 15 192 nt strains (including NDV2 strain) had a common motif for RRQKRF or KRQKRF which was consistent with highly pathogenic NDVs. F and HN genotyping showed consistency between NDV2 and the majority of the reference strains. However, the Indian. NDV4 strain from chicken, it belonged to genotypeⅡfor F gene, but for HN gene it belonged to genotype Ⅶ. Because NDV2 had start sequences identical to those of other reference strains, its start sequences were also highly conserved. The NP, P, M and L termination sequences of NDV2 were consistent with those of the reference strains but differed from those of the F and HN genes. NDV2 had termination sequences identical to those of La Sota and Sweden95 but different from those of other field strains. To better understand the pathogenicity of NDV2 in different hosts, we used NDV2 to attack specific pathogenfree(SPF) chicken(Gallus gallus), duck(Anas platyrhynchos platyrhynchos Linnaeus.) and pigeon(Rupestris Pallas); each attack group included a cohabitation infection group. After attack, the three hosts developed clinical symptoms at different times. Dissection of the infected hosts showed intestinal or tracheal bleeding and glandular stomach congestion. The pathogenicity of NDV2 in SPF chicken and pigeon was higher than that in duck; the strain further caused 50% and 20% cohabitation rates in infected chicken and pigeon. This research provides theoretical data for genetic variation characteristics and pathogenic rule of NDV.
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Received: 14 August 2013
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