Abstract: Objective　To investigate the efficacy of the inactivated Duck Tembusu Virus vaccine (HB strain) on the immune organs of ducklings infected with Duck Tembusu virus (DTMUV).Methods Fourteen-day-old Peking ducks were randomly divided into three groups: immunized group, non immunized control group, and negative control group. The immunized group was inoculated with the inactivated DTMUV vaccine at a dose of 0.3 mL per duck, and a booster immunization after 14 days. The challenge test was conducted at 21 days after the second immunization. Two days post-challenge, vaccine efficacy was evaluated via virus isolation. At five- and seven-days post-challenge, spleens, thymuses, and bursa of ducklings in each group were collected for viral load quantification and histopathological examination to assess the protective effects of the vaccine on immune organs of ducklings. Results　Virus isolation result showed that all 10 ducks in the immunized group were protected, whereas all 10 ducks in the non-immunized control group were infected. The result of virus load determination indicated that, on day 5 post-challenge, the viral load in the immune organs of the non-immunized control group was significantly higher than that of the immunized group. The result of histopathological observation revealed that on day 5 and 7 post-challenge, a large number of lymphocyte depletion and an increase in reticular cells in the immune organs of the non-immunized control group were observed. In the immunized group, aside from mild fatty degeneration in the liver, no significant pathological changes were observed in other tissues. Immunohistochemical analysis showed that on day 5 post-challenge, numerous positive antigen particles were detected in the immune organs of the non immunized control group, whereas no significant positive particles were found in the immunized group. The transcriptional level analysis of cytokines and granzyme A revealed that the immunized group of ducks maintained low expression levels of TNF-α, IL-6, IL-10, and granzyme A throughout the entire post challenge period.Conclusion　The inactivated Duck Tembusu virus vaccine effectively protects the immune organs of ducklings against DTMUV, maintaining their normal immune function.

Key words: duck Tembusu virus, inactivated vaccine, ducklings, immune protection, viral load, histopathology

摘要： 目的　研究鸭坦布苏病毒病灭活疫苗(HB株)对鸭坦布苏病毒(DTMUV)感染雏鸭免疫器官的保护作用。 方法　将14日龄北京鸭随机分为免疫组、未免疫组和空白对照组。免疫组以0.3 mL/只剂量接种鸭坦布苏病毒病 灭活疫苗,14 d后加强免疫。两次免疫后21 d进行攻毒实验。攻毒后2 d,通过病毒分离进行疫苗免疫效力评价;攻 毒后5、7 d采集各组鸭脾、胸腺和法氏囊进行病毒载量测定和组织病理学观察,以评价疫苗对雏鸭免疫器官的保护效 果。结果　病毒分离结果显示,疫苗免疫组鸭10/10保护,未免疫组鸭10/10发病。病毒载量测定结果表明,攻毒后 5 d,未免疫组免疫器官病毒载量显著高于免疫组。组织病理学观察结果表明,攻毒后5 d和7 d,未免疫组鸭的免疫 器官可见淋巴细胞大量减少和网状细胞增多,免疫组除肝有轻微的脂肪变性外,其他组织无明显组织病理学变化。 免疫组化结果表明,攻毒后5 d未免疫组鸭的免疫器官可见大量病毒阳性抗原颗粒。细胞因子及颗粒酶A转录水平 检测结果表明,免疫组鸭在攻毒后全程维持TNF-α、IL-6和IL-10等细胞因子和颗粒酶A(GzmA)的低水平表达。 结论　鸭坦布苏病毒灭活疫苗可有效保护雏鸭免疫器官免受DTMUV感染引起的损伤,维持正常免疫功能。

关键词: 鸭坦布苏病毒病, 灭活疫苗, 雏鸭, 免疫保护, 病毒载量, 组织病理学