Ultrastructural and Immunological Characterization of Hepatitis C Core Protein-DNA Plasmid Complexes

Recently, it has been shown that a truncated HCV core (HCcAg) variant, covering the first 120 aa (HCcAg.120), interacts with plasmid DNA vaccine (pIDKE2), encoding the HCV structural proteins (HCcAg, E1 and E2). In the present work, HCcAg.120-pIDKE2 complexes, forming heterogeneous packaged structures, were visualized using a negative stain/rotary shadow technique. Interestingly, 72 hours after intramuscular injection of HCcAg.120-pIDKE2 complexes in Balb/c mice, E2 protein was immunolabeled in muscle cells. In fact, HCcAg.120-pIDKE2 complexes induced anti-HCV humoral and cellular immune responses in mice when inoculated by both, parenteral or mucosal routes, although intranasal administration generally rendered weaker results. On the other hand, data demonstrated that Alum enhanced the HCV-specific IgG antibody production. However, the analysis of the HCV-specific cellular immune response showed that HCcAg.120-pIDKE2 delivered in PBS by the intramuscular route induced the strongest HCV-specific lymphoproliferative response, especially against E1 and induced viremia control in a vaccinia virus surrogate challenge model. These results support the use of HCcAg.120-pIDKE2 complexes in the rational design of therapeutic or preventive vaccine strategies against HCV infection.