Isolation, Identification, Genome Property Analysis And Pathogenicity Of Pigeon Paramyxovirus Type I (PPMV-1)

Pigeon Paramyxovirus type I (PPMV-1) is identified as Pigeon Newcastle Disease Virus, whichcould arouse the urgent and highly infectious disease in pigeons. The infectious agent belongs to thefamily Paramyxoviridae (genus Avulavirus). PPMV-1s were initially found in1970s in Middle East, andthe panzootic peak was during the early1980s.Firstly, in this study, the tissue samples at pigeons suspected to be infected with PPMV-1werecollected from four provinces–Guangdong, Liaoning, Jilin and Heilongjiang. Through the isolation of9-11-day old embryo egg, we obtained eight PPMV-1strains from these samples. Each of the virus hadbeen purified by plaque purification, and6clones were chosen from each strain and subjected to F genesequencing and comparing, which demonstrated that these strains were pure instead of heterozygous.Pathogenicity index showed that these eight isolates were mesogenic or lentogenic. Then the wholegenome of eight isolates were sequenced, which showed that the gene order of PPMV-1isolates was3’-NP-P-M-F-HN-L-5’, the length of genome was15,192nt, and the F protein cleavage motif were112RRQKRF117, similar to the virulent cleavage motif. The phylogenetic tree based on partial F gene(47nt-420nt) demonstrated that these isolates were classified as class II genotype VIb. Furthermore thephylogenetic trees based on whole F gene and whole viral genome indicated that the PPMV-1could beclassified as two groups–one represented the Chinses isolates and another stood for the overseas isolates.However there was an exception, pi/CH/LLN/110713, the strain was isolated in Liaoning province inChina, but showed high homology with the overseas strains. By the comparison and alignment of thegenome between the Chinese and oversea isolates, results showed the differences between two groupsfocused on the three regions (1632–2229,3023–3310and6103–6439). Ten nucleotide differences foundin this study might be genetic markers differentiating PPMV-1strains between Chinese and overseasisolates.Secondly, to further identify the pathogenicity of PPMV-1, we chose five PPMV-1isolates toinfect chickens, and one strain pi/CH/LHLJ/110822to infect pigeons. The results showed that these fivestrains were apathogenic, but could induce immune response to chickens. Thus we chose the mesogenicstrains pi/CH/LHLJ/110822to infect pigeons, which indicated that this strain was pathogenic to pigeons:the rate of mortality and morbidity were70%and80%, respectively. Meanwhile the apparent clinicalsigns, gross lesions and histopathologic changes could be found. The detection of virus RNA loads indead pigeons inferred that the kidney, lung, brain, trachea, harderian glands and glandular stomach maybe the target tissues or organs. In addition, the viral distribution in pigeons and chickens after3and7day post-inoculation (dpi) showed significant divergence on small intestine, duodenum, pancreas, largeintestine, harderian glands and glandular stomach on3dpi and on brain on7dpi. The serology testsshowed that the antibody titers on chickens were higher than on pigoens when infected withpi/CH/LHLJ/110822. Taken together, the results demonstrated that there were apparent differences onpigeons and chickens, when they were infected with PPMV-1, might be due to the differences oninfection process between different species of avian hosts, emphasizing the mechanism of this phenomenon need to be further studied.Lastly, the cross hemagglutination inhibition assay and cross virus neutralization assay were takento identify the antigenic difference between PPMV-1and NDV strains, indicating that there wassignificant difference between pi/CH/LHLJ/110822and vaccine strain La Sota, as well as strain F48E9.