| Avian infectious bronchitis is prevalent in all countries with an intensive poultry industry.The virus is belong to group 3 coronavirus.Avian infectious bronchitis attenuated vaccines play an important role in the control of IBV all over the world. Many commercial attenuated vaccines derived from local IBV field isolates have been used to control IBV in China besides Massachusetts serotype vaccines H120 and H52 that were imported.But because of different genotypes, IB outbreaks frequently in China in vaccined flocks.lt is suggested that fowl pox virus as a vector is safty and efficient.We have constructed rFPV-S1-IFN γ and rFPV-S1 successfully.In this study the experiment is about Immunological Efficacy ,containing Minimum immune dose ,safty,genetic stability and storage condition.rFPV-S1-IFNγ and rFPV-S1 were successive passaged 30 in chicken embryo fibroblast. The S gene and IFNγ gene from passage 15 , 20 , 25 and30 were amplified by polymerase chain reaction (PCR) and sequenced.Protein S1 and IFNγ expressed by rFPV-S1-IFNγand rFPV-S1 were identified by Indirect-immunofluorescence assay. The results show that there were no changes in the amino acid sequences.The 15th, 20th, 25th, 30th of recombinant fowl pox virus expressed overtly by Indirect-immunofluorescence assay. rFPV-S1-IFNγ and rFPV-S1 has good genetical stability. 1-week-old SPF chickens were inoculated with rFPV-S1-IFN YrFPV-S1(1.0× 10~5PFU/chicken),the results show that the recombinant fowlpox vaccines were safty.One hundred 4-week-old SPF chickens were randomly divided into 4 groups,and inoculated with rFPV-S1-IFN γ ,rFPV-S1 ,H120 and PBS(control).Four weeks post-vaccination, all chickens were challenged with IBV LX4 strain.The results showed that 13 out of 22 chickens immunized with rFPV-S1-IFN γ were protected,and the protection rates in groups immunized with rFPV-S1 or live IB vaccine alone were 18/24 and 17/22.After challenge,chickens of rFPV-S1-IFN γ had a shorter time period of virus shedding from respiratory tract and the viral antigen persiting in kidney,in comparison with rFPV-S1 and H120 group.Slight pathological findings could be seen in liver,spleen,kidney,lung and tracheal in H120 and rFPV-S1.and rFPV-S1-IFN γ performed even better than others , pathological changes could only be seen at 16 days post-chanllenge,which was 4 days shorter than that of other groups.All chickens developed antibody against IBV at 3 weeks post-immunization,and the antibody titer of rFPV-S1-IFN γ was lower than other groups. CD4+T cell population decreased and TCR γ δ+and CD8+T cell population increased which were vaccinated with rFPV-Sl-IFN Y ,other groups remained no significant change.The results demonstrated that rFPV-Sl-IFN Y can promote CD8+T cell maturation and improve immunity,and depress the amount of CD4+T cell in PBMCs.which may limit activation of B lymphocytes for soecific antibody production.lt also demonstrated that rFPV-Sl-IFN Y can suppress the side effect caused by inoculating with vaccine.There was no effect on the body weight gain of chickens immunized with vaccine containing IFN y ,it is significantly different from those chickens immunized with rFPV-Sl or HI20.135 White Leghorn 4-week-old SPF chickens were randomly divided into 9 groups respectively. 1 to 4 were inoculated with rFPV-Sl-IFN Y (l.OX 104PFU/chicken, l.OX 103PFU/chicken> l.OX 102PFU/ chicken, l.OX lOPFU/chicken), 5 to 8 were inoculated with rFPV-Sl (l.OX 104PFU/chicken, l.OX 103PFU/chicken, l.OX 102PFU/chicken, l.OX 10PFU/chicken),respectively. Group 9 served as negative control. Four weeks post-vaccination, all chickens were challenged with IBV LX4 strain.The results show that the protection ratio of rFPV-Sl-IFN y groups were above 72%, even to 91.7%. the protection ratio of rFPV-Sl groups were between 60%-70%. the minimum immune dose of the recombinant fowlpox virus rFPV-Sl-IFN Y vaccine were 1.0 X 103PFU/chicken. Meanwhile the recombinant fowlpox virus vaccines were storaged at -20°C,4°Cand room temperature,it is showed that the best temperature for storage is -20°C,it can be storaged at 4°C for a short time.The results demonstrated that the recombinant viruses can be as candidate vaccine agaist IBV.
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