Pathotypical characterization and molecular epidemiology of Newcastle disease virus isolates from different hosts in China from 1996 to 2005.

Thirty Newcastle disease virus (NDV) strains isolated from outbreaks in China during 1996 to 2005 were characterized pathotypically and genotypically. All strains except one were velogenic. An analysis of the variable region (nucleotides 47 to 420) of the F gene indicated that 6 isolates belonged to genotype II, 3 to genotype III, 1 (isolated from a pigeon) to genotype VI, and 20 to genotype VII. Isolates belonging to genotype VII were further divided into five subtypes, VIIa, VIIb, VIIc, VIId, and VIIe, and subtype VIId was made up of VIId1 to VIId5. These results showed that genotype VII isolates might have been the most prevalent in China during the past two decades. Genotype VII isolates shared high homology, but the homology was less than that between genotype VII viruses and the vaccine virus LaSota. Among these NDV isolates, 25 isolates had the velogenic motif (112)R/K-R-Q-K/R-R-F(117) that is consistent with results of the biological tests. However, four of five LaSota-type isolates that contained the lentogenic motif (112)G-R-Q-G-R-L(117) were velogenic, except SY/03, in the view of the biological test. The majority of genotype VII isolates had lost one or two N-glycosylation sites. Finally, a cross-protection experiment in which specific-pathogen-free chickens vaccinated with LaSota were challenged by six NDV isolates showed that more than three isolates were antigenic variants that could be responsible for recent outbreaks of Newcastle disease.

[Genetic characterization and correlation among fragments of HN gene of the field Newcastle disease viruses].

Twenty-four isolates of Newcastle disease virus (NDV) prevailing during 1997 -- 2005 in China were collected. These isolates were purified by CEF plaque assay and replicated in SPF chicken embryos. The hemagglutinin-neuraminidase (HN) genes of these viruses were cloned and sequenced. The HN gene sequences of thirty-six NDV reference strains in GenBank were also used in this study. The amino acid homologing of these viruses were compared and analyzed. The correlations among different fragments of HN gene were also analyzed. The results indicated that the homology of Chinese field NDV strains was 94.4%-99.4%, but 86.9%-89% compared with LaSota and Clone30, 87.9%-89.9% to F48E9, and 87.2%-96.2% to foreign NDV strains. There had the nearest distances among Chinese NDV isolates as compared with that of the LaSota, Clone30 and F48E9 by the phylogenetic tree. However, the distances of seven foreign NDV isolates were very close to Chinese NDV isolates as compared with these of the other foreign NDV isolates. We also found that all the Chinese field isolates were devoid of glycosylation site in position 538 -- 540. There were good correlations between different length amino acid fragments and the genomes of HN, especially the 5'-terminus first 80aa.

[Newcastle disease virus heredity mutation and correlation of HN and F gene].

Prevailed Newcastle disease virus isolates were collected during 1999-2005 in China. These isolates were purified by CEF plaque assay and replicated in SPF embryos. The fusion protein (F) gene and hemagglutinin-neuraminidase (HN) gene of these isolated viruses were cloned and sequenced. Some of the F gene and HN gene sequences from GenBank were also used in this study. The homologies of nucleotide and amino acids were compared and correlations were analyzed by SPSS8.0 software among different length sequences of the F gene or HN gene. The nucleotide homologies and correlation among the F gene and HN gene were also analyzed. The results indicated there are good correlation among different length sequences of the F gene or HN gene and the F genome or HN genome (r > or = 0.973). There was also good correlations among different length amino acids of NDV F protein or HN protein (0.911< or = r < or = 0.968). But, there was only a less correlation between the whole F gene and HN gene (r = 0.312). The heredity mutation of HN genes had the character of geographical areas. The sequences of HN gene in Chinese isolates had an identity of more than 97%. But there was only 79.2% - 80.7% in HN nucleotide homology among the Chinese isolates and La Sota (vaccine).

[Molecular characterization of a genotype II virulent Newcastle disease virus isolate from chicken].

Newcastle disease virus (NDV) field strain SQZ04 was isolated from a broiler flock with typical symptoms and lesions, and cloned by plaque-purification three times. NDV SQZ04 was determined as a virulent strain with MDT of 50.5h and 51.2h, ICPI of 2.0 and 1.92, IVPI of 2.8 and 2.68 respectively before and after plaque-purification. Analysis of F gene indicated that SQZO4 was determined as a virulent gene type II , and its protein amino acid sequence has homologies of 99.3% , 98.7% and 96.9% with published gene type II vaccine strains LaSota, B1, virulent strain Taxas48,much higher than homologies of 88.3% - 88.6% or 91.3% - 92.1% with published gene types VI and IX. This is the first virulent field strain of gene type UI reported in China. Further more, the amino acid sequence 111 GGRQGRL117 in the F protein cleavage site in SQZ04 strain is identical to lentogenic strains of NDV, such as vaccine strains LaSota, B1. This is the first report that virulent NDV could have lentogenic amino acid sequence in the cleavage site of F protein, where HN genes was compared SQZ04 has a higher homologies of 95.3%- 97.3% with known velogenic strains, but lower homologies of 87.8% - 89.5% with published lentogenic strains.