| Twenty strains of Newcastle disease virus (NDV) were isolated from outbreaks in chickens during 1985 and 2001 in East China and Xinjiang. Pathotype of these isolates was determined by pathogenicity tests according to the standard procedures proposed by Office International des Epizootics (OIE). The tests involved NDV inoculation of embryonated eggs to determine mean death time of the embryos (MDT) and inoculation of chickens to determine the intracerebral pathogenicity index (ICPI). The parameters of MDT and ICPI revealed that all the isolates were highly pathogenic (velogenic). 1700-nucleotides (nt) sequence from the 5'-terminal effusion protein gene (F) of eighteen isolates were amplified by RT-PCR and sequenced. 374-nt sequence analysis between nt 47-420 and restriction enzyme (RE) clevage site mapping of F gene between nt 34-1682 were used to compare the 18 isolates for genetic analysis. A phylogenic tree was constructed based on the 374-nt-sequence data of eighteen isolates in the study and 37 NDV reference strains from Genbank and published resources. Both methods revealed that these isolates belonged to three genetic groups, one designed as genotype IX was unique in China and the isolates of this genetic group were located on the newly emerged main branch in the phylogenic tree. The genetic distance between this group and genotype III /genotype I was 8.0-8.6% and 16.5-17.6% respectively. Genotype IX strains were also characterised by the presence of RE Rsa I site at nt 540 and by the simultaneous absence of Hinf I site at nt 1198, BstO I site at nt 1478 and Rsa I site at nt1625. The strains classified into genotype VI as reported were located on two novel clusters, one was designed as genotype VI f, the other was genotype VI g. The absence of Rsa I site at nt 872 distinguished the genetic subgroups VI f, and VI g from other members of the genotype VI. The isolates of genotype VII could be classified into three genetic subgroups, isolates JS-2/98, and JX-2/99 belonged to a new subgenotype VII e, which were located on a new cluster. All the isolates in the study of genotype VII could be recoganized by the new cutting site at nt 872 by RE Hinf I which is absent in the genetic supgroups VIIa, VIIb, and group VI. The amino acid sequences of the coding region of the F gene were deduced. Substitutions of specific amino acid residues of the three genetic groups encompassing evolutionary variations were described as follows: Ile9→Val9, and Val106→Ala106 for genotype DC; Ser5→Pro5 for genotype VIa-VIe but not for VIf, and VIg. More importantly, all the strains isolated after 1998 belonged to genotype Vfl and 8 out of 15 strains isolated after 1990s were in this group. The results showed that genotype VII viruses were the predominant ND viruses responsible for field outbreaks in China in recent years.22 strains of NDV of four genotypes( II, VI, VII, and VIII) of chicken, goose, and pigeon origin, were studied by the means of seven molecular antibodies prepared against the NDV F protein. Weak antigenic heterogeneity was found among these strains and the difference beared no relation to different genotypes. According to the resources lately reported, six antigenic epitopes of the F protein were located at the three-dimensional structure of the protein. The amino acids responsible for the epitopes of the strains in the study were compared and the result revealed that all these amino acid sites were highly conserved. The weak variations were found only among four strains not related to different genotypes. The result further proposed that different genotypes of NDV had not directed the antigenic changes of F protein, the most important protein of NDV in the protective immune response of the fowls. Protective efficacy difference among various genotype NDV vaccines ofdifferent origin was studied. Except the vaccine strain LaSota (genotype II ), the challenge strain F48E8 in China, the NDV strains tested were isolated from ND outbreaks in chickens, gooses, and pigeons. HI antibodies were assayed...
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