Combined immunization of DNA vaccine and replication-defective recombinant adenovirus bearing rabies glycoprotein gene induces immune response against rabies virus
Objective To investigate the immune response of mice primed by DNA particle bombing and boosted by immunization with replication-defective adenoviral recombinant bearing rabies glycoprotein gene. Methods The full-length glycoprotein gene of rabies virus CVS-N2c was inserted into plasmid pcDNA3.1. COS-7 cells were transfected with the recombinant plasmid pcDNA3.1/CVS-N2c GP and the expression of GP was determined by indirect immune fluorescent test. Mice were immunized with a heterogeneous prime-booster regime: First, DNA particle bombing vaccination was conducted twice by helium gas drived gene gun at a interval of two weeks. Then, replication defective adenoviral recombinant was used for booster at fifteenth weeks. The level of rabies virus specific antibody was measured by ELISA and the neutralizing antibody was titrated by a rapid fluorescent focus inhibition test (RFFIT). Results Indirect immune fluorescent test indicated that the glycoprotein was successfully expressed on the surface of COS-7 cells. Low level titre of specific antibody was induced by DNA immunization. RFFIT results showed that the neutralizing antibody reached 0.66 IU/ml after secondary DNA immunization and dramatic rising of neutralizing antibody was observed when the mice was boosted with 2×10 6 PFU recombinant replication defective adenovirus, the mean titre reached 90 IU/ml at seventeenth weeks. Conclusion Combined immunization of DNA vaccine and replication-defective recombinant adenovirus bearing rabies CVS-N2c glycoprotein gene induced potential immune response against rabies virus.