Repeated administration of hepatitis C virus core-encoding plasmid to micedoes not necessarily increase the immune response generated against this antigen

DNA immunization is a promising approach in generating immune responses to infectious pathogens in many different animal models. In an effort to augme nt the anti-[hepatitis C virus (HCV) core] immune response, generated after DNA immunization, the importance of vaccination regimen regarding dose and boosting was investigated in the present study. Balb/c mice were intramusc ularly injected with an expression plasmid encoding a truncated variant com prising amino acids 1-176 of the HCV core protein. The highest anti-core an tibody titres (1:3700) were detected in mice inoculated with 50-100 mug of core-encoding plasmid. Additionally, we demonstrated that antibody levels i nduced by a single injection of DNA could be further increased by boosting with a second injection of DNA three weeks after primary immunization. Howe ver, administration of additional doses or lengthening of the resting perio d between inoculations resulted in similar or even weaker anti-core antibod y responses. A similar anti-(HCV core) lymphoproliferative response was als o detected in animals that had the highest level of anti-core antibodies. T hese results indicate that, in clinical trials, vaccination regimen might b e a critical factor in generating optimal anti-(HCV core) immune responses after genetic immunization.