Wang X M, Zeng X W, Gao H L, Fu C Y, Wei P
National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Science, 427 Maduan Street, 150001, Harbin, P. R. China.
Avian Dis. 2004 Jan-Mar;48(1):77-83. doi: 10.1637/7061.
Very virulent (vv) infectious bursal disease virus (IBDV) Gx strain with high pathogenicity was attenuated through replication in specific-pathogen-free (SPF) chicken embryos and in chicken embryo fibroblast (CEF) cell cultures. The changes in VP2 nucleotide and the deduced amino acid sequences were obtained during attenuation of vvIBDV in CEF culture. Sequence analysis of selected passages from numbers 0 to 20 in CEFs (designated here Gx to CEF-20) showed that no changes were detectable in the VP2 gene before CEF-7. There were a few changes in the nucleotide sequence of the VP2 gene but no amino acid substitutions at CEF-8. The virus of CEF-9 was an intermediate with some amino acid changes that possibly were related to virulence. CEF-10 virus had become similar to CU-1 strain. The VP2 gene sequence remained the same from CEF-10 to CEF-20. The results of pathogenicity tests showed that the mortalities of Gx, CEF-5, CEF-8, and CEF-9 in 4-wk-old SPF chickens were 64%, 60%, 60%, and 32%, respectively; whereas CEF-10, CEF-15, and CEF-20 were nonpathogenic. Virus neutralization tests with Gx strain showed that the antigenicities are similar from Gx to CEF-20.
高致病性的超强毒（vv）传染性法氏囊病病毒（IBDV）Gx株通过在无特定病原体（SPF）鸡胚和鸡胚成纤维细胞（CEF）培养物中传代而致弱。在CEF培养物中vvIBDV致弱过程中获得了VP2核苷酸及推导的氨基酸序列的变化。对CEF中第0至20代（此处命名为Gx至CEF - 20）的选定传代病毒进行序列分析表明，在CEF - 7之前VP2基因未检测到变化。在CEF - 8时VP2基因的核苷酸序列有一些变化，但无氨基酸替换。CEF - 9的病毒是一种中间型，有一些可能与毒力相关的氨基酸变化。CEF - 10病毒已变得与CU - 1株相似。从CEF - 10到CEF - 20，VP2基因序列保持不变。致病性试验结果表明，Gx、CEF - 5、CEF - 8和CEF - 9在4周龄SPF鸡中的死亡率分别为64%、60%、60%和32%；而CEF - 10、CEF - 15和CEF - 20无致病性。用Gx株进行的病毒中和试验表明，从Gx到CEF - 20抗原性相似。
