Preparation And Application Of Infectious Bronchitis Virus(M41) HI Antigen

At present, the potency test of the Avian infectious bronchitis inactivated vaccine is hemagglutination inhibition (HI) test, but there is no commercial IBV-HI antigen in China. For this reason, we engage in the preparation of IBV-HI antigen and the research of potency evaluation of infectious bronchitis inactivated vaccine.Avian infectious bronchitis virus M41 strain was inoculated into 10-days embryos. After incubation for 36 hours at 37℃, allantoic fluid was harvested and was centrifugated at 5, 000g for 40min and then 30, 000g for 2h. Infectious bronchitis HI antigen was prepared by treating 100-fold concentrated virus with 10%~20% clostridium welchii culture supernatant at 37℃for 2-2.5h. According to the method, three batches IBV-HI antigen were prepared and lyophilized. The HA titer of three bathes HI antigen ranged between 8log2 and 10log2. Three batches self-made HI antigen and HI antigen of the Netherlands GD company were respectively applied to test Newcastle Disease, Avian influenza, Egg drop syndrome positive sera and negative sera. The HI titers were below 3log2 and the self-made antigen showed good specificity. Based on quality standard of potency test, three bathes self-made HI antigen and HI antigen of the Netherlands GD company were respectively applied to the potency test of 10 batches ND-IB-AIV inactivated vaccine and 4 batches ND-IB-EDS inactivated vaccine. The ratios of HI titer geometric average of sera from boosted layers with inactivated vaccine to that of live vaccine are 9.4 (2007001), 8.5 (2007002), 9.8 (2007003), and 10.5(GD), respectively. The 3 batches HI antigen were stable at 4℃for one year.According to the potency test standard of the IBV inactivated vaccine in serology to design the project as follow: all of the layers were divided into group A, B and C. The group A was vaccinated with IBV live vaccine, and then vaccinated with IBV inactivated vaccine before laying peak. The IBV inactivated vaccine was qualified when tested with IBV-HI antigen (2007003). The group B was vaccinated only with IBV live vaccine. The group C was used as non-immune control. All of the layers were challenged with IBV-M41 at laying peak. Record and analyse the changes of serology and laying at diffident time points. The result showed that the laying capacity of the group B dropped 17% in 4 weeks after challenged with IBV-M41, and the laying capacity of group C dropped 34%. The laying rate of the group A did not change after challenged with IBV-M41. The result demonstrate that the qualified production of IB inactivated vaccine tested in accordance with serology standard can protect the layers from IB in laying period, and the potency test standard of inactivated vaccine in serology is available.