猪流行性腹泻弱毒株的培育

用ＰＥＤＶＣＶ７７７株强毒适应Ｖｅｒｏ细胞系并传至１４７代。以ＰＥＤＶ沪株做效检用强毒。传代毒８３代之后适应了仔猪肾原代细胞。自９０代起进行了５次克隆纯化，克隆是在２次群斑（由５～７个单斑组成）的基础上，再进行３次单斑挑选（均是１ｍｍ以内小空斑）。以８３７斑５株继续传代并做系列试验。传代毒的毒价为１０７．０～１０７．５ＴＣＩＤ５０／０３ｍｌ。免疫接种途径为后海穴位。克隆后５代（总代次１０４代）～２５代的５批次主动免疫试验的总保护率为９５９２％（４７／４９），对照组８８８％（１６／１８）发病。克隆后１７代～４０代的８批次被动免疫试验的总保护率为９６２％（７６／７９），对照组１００％（１０／１０）发病。以克隆后２５代（总代次１２５代）进行稳定性试验，经６代次返祖传代毒力未返强，仍是稳定的，已符合弱毒株的标准。在与ＴＧＥ弱毒株组合制备的二联弱毒苗的初步田间试验中取得良好效果。

Development of Porcine Epidemic Diarrhoea Attenuated Virus

PEDV CV777 strain was adapted to grow in Vero cell lines and passed for 147th passage.PEDV S strain was used as challenge.CV777 strain was adapeted to grow in porcine kidey primary cell after 83th passage.The cloning and screening had been done from 90 th passage for 5 times.group plaques had been done for 2 times,and then single plaque for 3 times.(palque dimeter less then 1 mm).83 7 plaque 5 strain was passed and then serial tests were performed with the passing virus.Virus titer of cloning strain were 10 7.0-7.5 TCID 50 /0.3ml.The immune route was Hou Hai point. 5 experiments for active immunization were done with 5ht(total 104th passage) 25th passages of cloning virus,total protective rate was 95 92%(47/47),whereas the morbidity was 88.8%(16/18) in control group. 8 experiments for passive immunization were done with 17th 40th passages of cloning virus,total protective rate was 96.2%(76/79),whereas 100%(10/10) piglets in control group occured disease,The virlence was stabile by passing 6 passages through piglets with 25 th passage,it show that PEDV CV777 strain had been attenuated.The bicombind attenuated vaccine against TGEV and PEDV had obtained good results in field trail..