| Summary: | 碩士 === 國立中興大學 === 獸醫微生物學研究所 === 85 === There were three major outbreaks of Newcastle disease in
Taiwan. Sixteen Taiwanese isolates from these outbreaks,
together with 5 vaccine strains, 3 Saudi Arabian isolates and
the Sato strain, were subject to RT-PCR (reverse transcription-
polymerase chain reaction) amplification and direct DNA
sequencing. The sequences obtained were then compiled by GCG
software and analyzed by PAUP (phylogenetic analysis using
parsimony) to construct the phylogenetic tree of these viruses.
The tree was found to contain six main groups. The first three
groups are composed of Taiwanese isolates in three different
groups exhibited extensive sequence variations, which might be
due to the accumulation of mutations during the replication of
RNA viruses. Moreover, amino-acid sequences predicted from the
nucleotide sequences by the GCG software revealed that all
Taiwanese isolates, except one, have two pairs of basic amino
acids in their F0 cleavage site. In addition, the residue in
the position 117 of F0 protein fromall Taiwanese isolates was
found to be phenylalanine, indicating that all these isolates
are virulent viruses. For the vaccine strains analyzed, the
residue in the position 117 was leucine, the overall sequences
revealed that they are avirulent strains. Finally, three Saudi
Arabian isolates, and the Sato strain all showed typical amino-
acid sequences of virulent viruses.
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