Immunogenicity of recombinant VP2 protein of infectious bursal disease virus expressed in recombinant baculoviruses

Recombinant transfer vector pFVP2 was constructed by cloning vvIBDV vp2 gene of the Gx isolate into pFastBac HTA.The transfer vector was transformed into E,coli DH10Bac cells that contain a baculovirus shuttle vector(bacmid)with a mini- attTn7 target site and a helper plasmid.The recombinant BacmidVP2 was generated by transposing themini-Tn7 element located in pFVP2 to the mini-attTn7 attachment site on the Bacmid and then transfected into the Sf9 insect cells by lipofectin to produce recom- binant baculovirus(rBacVP2).Expression of IBDV VP2 in Sf9 cells infected with the recombinant virus was detected by Western blot and indirect immunofluorescence assay(IFA).The lysates of rBacVP2 infected cells were used to immune 3-week-old SPF chickens. Antibodies to IBDV were detected by ELISA after 7 d post-immunization and by AGP after 14 d post-immunization.The protection rate against vvIBDV Gx infection was 75% at 14 d post-immunization and 100 % at 14 d after the boosting immunization.