Identification And Pathogenic Study Of Neurotropic Paramyxovirus Type-1(PPMV-1) Virus

Newcastle disease(ND), Asian Fowl pest, is one of the most highly pathogenic viral diseases of avian species. ND is caused by NDV, which is also known as avian paramyxovirus type 1(APMV-1); this virus belongs to the genus Avulavirus and subfamily Paramyxovirnae(family Paramyxivirinae, order Mononegavirales). ND is an acute and highly contacting infectious disease;it has a wide host range and it has been demonstrated in at least 250 species in most orders of birds, which mainly infected chicken. It can cause classical symptoms of infected birds, such as dyspnea, spirit atrophy, diarrhea, serosa and mucosa and hemorrhage, which has a considerable impact on the poultry indusry worldwide, causing significant economic loses. Pigeon paramyxovirus type-1(PPMV-1) characterized using monoclonal antibodies(m Abs) and by analysis of F gene, is an antigenic and host variant of APMV-1, and responsible for ND-like infectious disease to pigeons. We conducted this study to study the epidemic condition and the pathological characteristic of this isolate. The mainly results of the research study as follows:1. In March 2015, tissue samples, including liver, lung, heart, spleen, and kidney of some infected ostrich birds were collected from some pigeon breeding bases of Yangling town, Shaanxi Province, northwest of China. A pigeon-origin NDV isolate, which was abbreviated as PPMV-1/ YL-01/Ch/15, obtained by HA, HI, and RT-PCR.2. The pathogenicity index of PPMV-1/YL-01/Ch/15 isolate exhibited an mean death time(MDT) of 62.4h and intracerebral pathogenicity index(ICPI) of 1.13. What’s more, the cleavage site of fusion protein of this isolate was 112R-R-Q-K-R-F117. According to the assessment criteria of viral virulence of OIE, this isolate was a mesogenic PPMV-1 strain. Meanwhile, the comparative pathogenic study of this isolate indicated that the morbidity and mortality of the inoculated pigeons were 100% and 90% during 2 weeks observation period of artificial infection. Meanwhile, the rate of neural symptoms dead pigeon was 100%. However, the morbidity and mortality of inoculated 2-week chicken were 60% and 30% and the rate of neural symptoms dead chicken was 50%. The morbidity and mortality of 2-week SPF chicken inoculated F48E9 strain were 100%. However, the dead 2-week SPF chickens have no neural symptoms. The results of necropsy of them show a classical ND pathological changes. This study show that this isolate was a neurotropic PPMV-1 isolate, which can cause infected birds a classical neural symptoms.3. The complete genome sequences of F gene of PPMV-1/ YL-01/Ch/15 was amplified by RT-PCR. The results of deduced amino acids and nucleotide acids of F of PPMV-1/ YL-01/Ch/15 shown that 6 amino acid substitutions were identified in the functional domains of F, which were compared with mostly other Class II NDV isolates. There was no amino acid subsititution in neuralising epitopes of F. A phylogenetic tree was constructed based on the complete sequences of the F gene by using MEGA(7.02). This NDV isolate was classified into genotype VIi in Class II, which have highly evolutionay relationship with Shaanxi 10(Accession number: KC853020), a isolated from crested ibis(Nipponia Nippon) in 2010. Furthermore, PPMV-1/ YL-01/Ch/15 in this study showed 99.9% nucleotide homology with it. This study firstly obtained PPMV-1 isolate in VIi sub-genotype.