Functional and Phylogenetic Analysis of the F and HN Genes of Newcastle Disease Virus Isolates from Taiwan

• Main Authors: Sung-Hua Yeh, 葉松樺
• Other Authors: Hung-Jen Liu
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/52583051769743285856

碩士 === 國立屏東科技大學 === 生物科技研究所 === 96 === Newcastle disease caused by Newcastle disease virus (NDV), causes respiratory distress, diarrhea, circulatory disturbances and impairment of the central nervous system. NDV is a highly lethal and highly contagious disease of avian species, which leads to substantial economic losses in the poultry industry. NDV possesses two envelope spike glycoproteins: the haemagglutinin–neuraminidase (HN) protein and the fusion (F) protein. These two proteins play an important role in NDV infection. This study collected recent Taiwanese strains of Newcastle disease virus from 2006 to 2007. All of the isolated strains have been classified as velogenic NDV based on mean death time in eggs (MDT) assay. Initially 861 and 732 bp segments of fusion (F) protein and haemagglutinin-neuraminidase (HN) genes respectively, were amplified by reverse transcription-polymerase chain reaction (RT-PCR). Then 562 and 616 bp of the above F and HN gene RT-PCR fragments were further amplified by nested PCR. All the Taiwanese isolates in this study, carry the motif112RRQ(K/R)R116 and have the amino acid F117, which is characteristic of velogenic NDV type at the F protein cleavage site that has more than four alkaline amino acids. A phylogenetic tree analysis based on the nucleotide sequences of the F gene revealed that the Taiwanese NDV isolates responsible for recent outbreaks belonged the VII genotype category. Since recent Taiwanese NDV isolates exhibited low level of hemagglutinin activity, a real-time PCR was established to determine the copy number of NDV isolates tested in HA assay. From sequence analysis of HN protein of recent Taiwanese NDV isolates it was discovered that they carried a substitution at the amino acid residue 81 (I/V to M) in the heptad repeat region A, which may be related to the decrease in the hemagglutinin activity.