Immune Efficacy Evaluation Of The Inactivated Vaccine Of Duck Tembusu Virus Disease

Objective:The objective of this paper is to detect HI antibody titer of du ck Tembusu virus inactivated vaccine(strain HB)and to research the growth and decline of antibody in vivo,the objective is to compare the difference in anti body levels between two different immune pathways and to test the quality of vaccines.The HI test provide basis for the vaccine efficacy test criteria,The o bjective of this paper is to evaluate the correlation of the HI test and challeng e test of duck Tembusu virus inactivated vaccine,First-Pass determining the pr otection criteria of HI antibody titer.Method:Three batches of vaccines were used to immunize the 18-day-old ducks by subcutaneous injection and intramuscular injection in 0.25 mL,respe ctively.Secondary immunization was proceeded in the same doses and route at 2 week after primary immunization.Ducks were regrouped according to the HI titer and challenged with 0.5 mL(100 DID50)DTMUV at week 2 after pri mary immunization and week 2,3,6,12,16 after primary immunization.Serum sa mples were collected at 2 days later for virus isolation.All the result were co unted to evaluate the immune potency of vaccines.The correlation of HI titer and immune protection rate was analyzed.Result:HI antibody GMT value(challenge protection rate)at week2,3,6,12,16 after primary immunization:Subcutaneous(BIO-201801 batch):1:9.27(20%),1:195.95(80%),1:102.52(100%),1:22.62(90%),1:28.21(100%);Intramuscular(BIO-201801 batch):1:36.62(40%),1:821.39(100%),1:182.58(100%),1:61.73(100%),1:63.54(100%).Subcutaneous(BIO-201802 batch):1:17.92(20%),1:289.81(100%),1:80.00(100%),1:35.13(100%),1:25.24(80%);Intramuscular(BIO-201802 batch):1:42.51(40%),1:868.21(100%),1:222.18(100%),1:61.32(88%),1:52.83(100%).S ubcutaneous(BIO-201803 batch):1:4.54(0%),1:143.85(80%),1:74.64(100%),1:26.96(67%),1:20.00(100%);Intramuscular(BIO-201803 batch):1:40.00(40%),1:475.52(100%),1:144.92(100%),1:44.21(100%),1:45.96(100%).At week 6 after pr imary immunization,HI antibody titer:1:20,1:40,1:80,1:160,1:320,the chall enge protection rate:100%(3/3),100%(3/3),100%(12/12),100%(6/6),100%(5/5),the control group morbidity was 100%(5/5).Conclusion:The vaccine quality was qualified and the protect effect was g ood,the vaccine has long duration of immunization.The HI antibody titer was bacically consistent with the challenge protection rate of duck Tembusu virus inactivated vaccine(strain HB).The HI antibody titer detection could be used to evaluate the efficacy of duck Tembusu virus inactivated vaccine(strain HB)instead of challenge test.The protection criteria of the HI antibody titer were determined to 1:20.