Abstract: The immunogenicity of the recombinant rabbit hemorrhagic disease virus (RHDV) capsid protein (VP60) expressed in E. coli was investigated. Thirty-four clean rabbits were randomly divided into 3 groups and respective subcutaneously injected twice, with 7 days interval, using adjuvant (8 rabbits), the recombinant VP60 (8 rabbits) and VP60 mixed with adjuvant (18 rabbits). The dosage of VP60 protein was 400μg per injection. Titer of the antibody raised by VP60 protein combined adjuvant was much higher than that of VP60 protein only at the 7th day after second injection (ELISA 1∶64 000 vs 1∶4 000 / HI 1∶128 vs 1∶16). The result indicated that adjuvant could accelerate the production of antibody. The immunized animals were challenged with highly virulent NJ85 isolate of RHDV. The mortality rates were 100% (8/8) for the adjuvant control and recombinant VP60 groups. In the meanwhile, the protective rate was 100% (18/18) for VP60 combined with adjuvant group. The death caused by RHDV infection was confirmed by the evidences that HA titer of liver tissue in dead rabbits was over 1∶512 while less than 1∶2 in surviving rabbits, and no bacteria staining in liver tissues smear as well as no bacteria growth in culture. Eight hundred domestic rabbits in rabbit farm immunized with the recombinant subunit vaccine to RHD and the occurrence of RHD and harmful effects due to the vaccination were not observed. Additionally, it was also confirmed that the recombinant E. coli could keep stability in the process of storing, restoring, culture, induced expression and digestion of recombinant plasmid.

Key words: Rabbit hemorrhagic disease virus (RHDV), Recombinant capsid protein (VP60), Immunization