Fusion protein is the main protective antigen of NDV and the primary structure of fusion protein determines the virulence of the virus.

蛋白不仅是NDV主要保护性抗原，而且F蛋白一级结构(氨基酸顺序)决定病毒毒力。

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Viruleut and 'antigen stability of passages CAV-2 showed that passage 53-73 viruses hod no pathogenicity for fox, but virulence was stable.

经对继代毒的毒力测定和抗原稳定性试验证明，53 - 73代毒对狐无致病性，而且毒力稳定。

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