Primary Studies On Biological Characterization Of Envelope Glycoprotein Gene Of Avian Paramyxovirus Type â… isolates

Six APMV桰 isolates, included three GPMV named HG97C3. YGg7F]1. YG~2C4 arid three CPMV named CNg8F8. T~F4. Y~F9, were selected to make a series of pathogenicity testTheMDTofthesixstrainswere56.7. 52.0. 53.2. 54.0. 53.4. 55.2, thelCPlwere 1.64. 1.69. 1.70. 1.89. 1.81. 1. 81, the IVPI were2. 62. 2.6. 2.6. 2.62. 2.62. 2.6. From the parameter determined we can concluded that the virulence of all the isolates were similar to velogenic strains of NDV. At the same time a series of virulence test were made on Geese抯 embryos and Geese with the isolates of GPMV, named HG97C5. YG97F11. YG9~2C4. The MDTof thirteen梔ay梠ld Geese抯 embryos were 68. 8. 67. 4. 70. 2, the ICPI in day梠ld Geese were 1. 52. 1. 64. 1. 66 , and the IVPI in 6梬eek梠ld Geese were 1. 56. 1. 65. 1. 675. Although there isn抰 a standard to assess the virulence of GPMV, the results indicated that the three strains all had a high pathogenicity for chickens and geese.Sixteen strains of APMV桰, isolated from cases during epidemic from 1994 to 2000 in different parts of China, main function segment of Fusion gene (from 47 to 581 bp) were amplified by RT桺CR. And further cloned into pGEM拁桾 vector. The sequence analysis showed that the length of the F gene segment were 535 bp. The amino acid sequence of the cleavage site region was ?2R桼桻/R桲/R桼桭117, matching to virulent NDV strains. A phylogenetic tree based on obtained sequences of reference NDV strains was constructed. The results revealed that thirteen isolates belonged to genotype VII, and it indicated the genotype VII NDV was the major pathogeny causing the epizootic of ND in recent years in China.The GPMV isolate YG97 and the CPMV isolate Y48 were propagated in 10梔ay梠ld chicken embryos. The allantonic fluids of the virus were purified and the viral genomic RNA were extracted. Each of the F gene from the two virus had been successfully amplified by RT桺CR , and further cloned into PGEMR~T vector, and each positive recombintant plasmid were screened by restriction enzyme analysis. The sequence analyses showed that the length of the nucleotide sequence of the F gene amplified were 1695 bp and encoding a protein of 553 amino acids. The amino acid sequence of the cleavage siteregion were 212R桼桻--K桼桭317, matching to virulent NDV strains, and at the same time it was consistent with the pathogenically test of the isolates. Sequence comparison between YG97 and Y~, the homology of the nucleotide was 99%. Sequence comparison with the published Chinese standard virulent strains F48E9, the homology of the nucleotide was 86%, and the homology of the nucleotide compared with LaSota was 83% and 84%. The results indicated the mutation of the two isolates had varied largely compared with classic NDV on the F gene.We amplified the haemagglutinin梟euraminidase (HN) gene of the isolates of YG97 and Y~. The sequence analyses showed that the nucleotide sequence of the HN gene amplified were 1981 bp and encoding a protein of 571 amino acids. Sequence comparison between YG97 and Y~, the homology of the nucleotide was 99%. Compared with the Taiwan/95 strains, the homology of the nucleotide was 93%, the homology of the amino acid was 96%, which indicated they probably had a common origin. The homology compared with LaSota were 79% . The results indicated the mutation of the two isolates had varied largely compared with classic NDV on the HN gene.