Biological Property Of Newcastle Disease Virus Isolated From Five Province In China And Study On Selection Of Candidate Vaccine Strains

The research is based on the experimental treatment of 8 strains of Newcastle disease virus (NDV) respectively isolated from the disease-infected poultry in different area China. After being cloned and purified by the method of limited-point dilution with egg embryos, Main function segment of F gene with the length of 1629bp the above 8 isolates of NDV were amplified by RT-PCR. Comparsion has been made on the nucleotides of the gene F and their deduced amino acid sequence with represent NDV strains. The genotypes of the 8 strains have been established by Phylogenetic tree. Result show that the genetic similarities 6 strains were 97.4%-99.6%, and with F48E9 strain were 85.8%-89.3%. Protein similarities the 6 strains were 96.7%-99.3%. The 6 strains of amino acid sequence in F protein gene cleavage site(112-117) of avirulents was 112R-R-Q-K-R-F117 which confumed that they were velogenic and belong to genotype VII. The other 2 strains, the genetic similarities were 99.5%, Protein similarities were 98.7%, and with LaSota were 98.8%, 99.2%, respectively. The other 2 strains of amino acid sequence in F protein gene cleavage site(112-117) of avirulents was 112G-R-Q-G-R-L117 which confumed that they were lentogenic and belong to genotypeâ…¡.Experiment the analytical foundation in the above biological characteristrics, included in this research were also 12 strains of NDV, among which were LaSota, I, Clone30, F48E9, together with the above mentioned 8 strains, whose cross-HI inhibition and cross-neutraliation experiment have been conducted. Result show that antigenic difference have been existed among these strains. HB38 strain and F1 strain have better antigenic with the other strainsThe genotype, the biological property and the immunogenicity were tested. HB38 strain and F1 strain were considered to be substitute vaccines accordingly.Pathogenicity test indicates that MDT, ICPI and IVPI of HB38 strain were 45.6h, 1.94,2.98 respectively;MDT, ICPI and IVPI of F1 strain were 55.2h,1.96,2.79 respectively which they were suppose to be a virulent strains.HN gene with the length of 1716bp HB38 strain and F1 strain were amplified by RT-PCR, including complete ORFs. Sequence analysis indicates that protein homologous with F48E9 strain were 89.7%,88.8%, respectively. Cross-protection test result show that HB38 strain and F1 strain could cross-protect by 3 strains of NDV challenge.