犬瘟热病毒小熊猫株的驯化致弱及其免疫研究

Attenuation and immunity of canine distemper virus LP strain from lesser panda

犬瘟热病毒 (CDV)小熊猫低代强毒 (LPV9)经MDCK、CRFK和Vero细胞分别传至 2 1、2 0、2 0代 ,并采用蚀斑技术对传代毒进行克隆。病毒每传 2 0代进行 1次致弱程度鉴定 ,结果表明LPV9随所传代数增加 ,对幼犬的致病性逐渐减弱 ,至第 70代 (LPV70 )时 ,对接种犬失去了致病性。 2个组犬按每只 1× 10 4 TCID50 ,分别接种LPV70 和疫苗弱毒复壮株R 2 0 /8,14d后前者刺激接种幼犬产生的中和抗体效价均大于 1∶10 0的完全保护价 ,而后者则有低于 1∶10 0的 (攻毒保护率分别为 5 /5和 4/5 ) ,故驯化致弱的LPV70 免疫原性要好于疫苗弱毒复壮株R 2 0 /8。将LPV70 分别在细胞上连续 2 0代、在幼犬连续传代 5代后 ,其细胞培养物及从动物体内回收的病毒免疫原性及安全性能够稳定遗传。

Low pssaege of virulent canine distemper virus (CDV) lesser panda (LP) strain (LPV 9) was continuously cultured in MDCK, CRFK and Vero cell lines for 21,20 and 20 passages, respectively, and cloned by a plaque screening in order to obtain a new attenuated strain of CDV. To examine pathogenicity of the strain, susceptible dogs were inoculated with the virus of passage 30,50 and 70, respectively. The test results indicated the pathogenicity of LP strain for puppies was gradually decreased with increasing passages of the strain in cells and virulence of the passage 70 of CDV LP strain for susceptible animals disappeared. In the test of animal infection with CDV, dogs of two groups were inoculated with LPV 70 or rejuvenated vaccine strain R 20/8 at a dose of 1×10 4 TCID 50 , respectively. On the day 14 after the inoculations, the neutralizing antibody titers of all of the inoculated dogs of the LPV 70 group were higher than 1∶100 (complete protective titer), but only part of the R 20/8 group were higher than 1∶100 , and the protective rate of the former was 5/5 and the latter 4/5 after challenging. So the immunogenicity of the LPV 70 was better than that of the R 20/8. The LPV 70 that had been continuously passaged in cells for 20 times and in young dogs for 5 times was indentified, which showed safety and immunogenicity of the LPV 70 was very stable.