犬细小病毒2a型致弱疫苗株的培育与免疫效力试验

Establishment of the attenuated vaccine strain of canine parvovirus type 2a and immune efficacy experiments

为了获得犬细小病毒(CPV)变异株的致弱疫苗株,将CPV-2a野毒株(YZ10-5)在FK81细胞上连续传代,评价不同代次毒种对易感幼犬的毒力。用高代次传代毒种免疫高母源抗体(MDA)幼犬,经CPV-2a和CPV-2b强毒攻毒,评价致弱株的免疫保护效力。结果表明,CPV-2a毒株(YZ10-5株)在FK81细胞上连续传至31代,毒力明显减弱,传至61代无明显毒力。用61代致弱毒种(YZ10-5/F61),2×10^3TCID50/剂,间隔3周,2次皮下注射接种高母源抗体幼犬,第2次免疫后3周用CPV-2a和2b变异株口鼻攻毒,所有免疫犬无明显临床症状,且粪便无排毒,而未免疫犬全部发病和粪便排毒。初步研究表明, CPV-2a传代致弱毒株(YZ10-5/F61)有希望用于开发CPV防控的新型疫苗。

In order to obtain attenuated vaccine strain of canine parvovirus(CPV) variants,a CPV-2 a wild strain(YZ10-5 strain) was serially passed on FK81 cells to evaluate the virulence of different passages of the virus to susceptible puppies.The immune protection efficacy of the highly-attenuated strain were evaluated by inoculating puppies with high maternal antibody(MDA) followed by challenge with virulent canine parvovirus type 2 a and 2 b variants.The results showed that the virulence of the 31 st passage virus were significantly reduced,and the 61 st passage virus had no significant virulence.Dogs with high maternal antibody were inoculated twice subcutaneous at intervals of 3 weeks with the 61 st passage attenuated strain(YZ10-5/F61) at 2×10^3 TCID50/dose.Three weeks after the second immunization,all dogs were challenged oronasally with the combination of virulent CPV-2 a and 2 b strains.All immunized dogs showed no specific clinical signs of infection or virus shedding in their feces,while control animals displayed pronounced clinical symptoms and shed challenge virus in the feces.Preliminary studies showed that the YZ10-5/F61 CPV-2 a strain has the potential to be used in the development of novel vaccines for the prevention of CPV disease.