经鸡胚感染的ALV-J对新城疫弱毒疫苗免疫的抑制作用及疫苗株对病毒载量的影响

In Ovo Administration of ALV-J on Immunosuppressive Action of Newcastle Disease Attenuated Vaccine in SPF Chicken and Effect of La Sota Strain on ALV-J Viral Load

为了解经鸡胚感染携带J亚群禽白血病病毒(ALV-J)的雏鸡体内ALV-J对新城疫(ND)弱毒疫苗(La Sota株)免疫的抑制作用以及疫苗免疫后增强ALV-J对雏鸡致病作用的可能性,随机选择50个SPF鸡胚经卵黄囊接种模拟ALV-J感染,同时选取等量SPF鸡胚以相同方式接种PBS作为对照。出雏后于接毒组和对照组各取20只SPF鸡在7日龄时免疫ND弱毒疫苗(La Sota株)。2~6周龄时,记录各组鸡的体重和免疫器官指数,并对雏鸡的NDV抗体水平和血液ALV-J病毒载量进行动态检测。结果显示,感染ALV-J的SPF鸡5、6周龄时体重显著低于PBS对照组(P<0.05),而感染ALV-J再免疫新城疫弱毒疫苗后SPF鸡体重进一步降低(P>0.05);与PBS对照组相比,6周龄时感染ALV-J的SPF雏鸡胸腺萎缩和脾脏肿大(P>0.05),免疫新城疫弱毒疫苗后胸腺和脾脏损伤加剧(P<0.05);3、4周龄时感染ALV-J再免疫ND弱毒疫苗组的雏鸡NDV抗体水平极显著低于仅免疫ND弱毒疫苗组(P<0.01);4周龄时免疫弱毒疫苗后的SPF鸡血液中ALV-J病毒载量高于未免疫组(P<0.01)。研究表明,感染ALV-J的雏鸡在免疫ND弱毒疫苗(La Sota株)后增强了ALV-J对SPF雏鸡的致病作用,提示净化种源的重要性。

In order to understand the inhibitory effect of avian leukosis virus subgroup J(ALV-J)infected by chicken embryo on the immunity of attenuated Newcastle disease(ND)vaccine(La Sota strain)and the possibility of vaccine immunity enhancing the pathogenicity of ALV-J in young chicks,50 SPF chicken embryos were randomly selected to be inoculated with yolk sac to simulate ALV-J infection,and the same amount of SPF chicken embryos were inoculated with PBS in the same way as the control.Twenty SPF chickens were collected from inoculated group and control group were inoculated with attenuated Newcastle disease virus vaccine(LaSota strain)at 7 days of age respectively after hatching.The body weight and immune organ index of chickens in each group were recorded from 2 to 6 weeks,and the NDV antibody level and the ALV-J virus load in blood of the chickens were dynamically detected.The results revealed the body weight of SPF chicks infected with ALV-J was significantly decreased compared with PBS control group at 5 and 6 weeks of age(P<0.05),but the body weight of infected chicks was further decreased after inoculcation of attenuated Newcastle disease virus vaccine(P>0.05).SPF chicks were infected with ALV-J induced thymic atrophy and splenomegaly compared with PBS control group at 6 weeks of age(P>0.05),and the thymus and spleen injury consistently increased after inculcation of attenuated Newcastle disease virus vaccine(P<0.05).Antibody levels against NDV were significantly lower in the ALV-J-infected SPF chicks than that in the control group at 3 and 4 weeks of age(P<0.01).ALV-J virus load in blood was higher in the SPF chicks after immunization than that in the unimmunized group at 4 weeks of age and a significant difference was found between two groups(P<0.01).The results showed that the ALV-J infected chicks vaccinated with attenuated NDV vaccine(La Sota strain)could enhance the pathogenicity of ALV-J against SPF chicks,suggesting the importance of eradication the provenance.