Evaluation of cellular responses for a chimeric HBsAg-HCV core DNA vaccine in BALB/c mice

Fusion of Hepatitis B virus surface antigen (HBsAg) to a DNA construct might be considered as a strategy to enhance cellular and cytotoxic T-lymphocytes (CTL) responses of a Hepatitis C Virus core protein (HCVcp)-based DNA vaccine comparable to that of adjuvanted protein (subunit) immunization. pCHCORE vector harboring coding sequence of HBsAg and HCVcp (amino acids 2-120) in tandem within the pCDNA3.1 backbone was constructed. The corresponding recombinant HCVcp was also expressed and purified in Escherichia coli. Mice were immunized either by adjuvanted HCVcp (pluronic acid + protein) or by pCHCORE vector primed/protein boosted immunization regimen. The cellular immune responses (proliferation, In vivo CTL assay and IFN-γ/IL-4 ELISpot) against a strong and dominant H2-d restricted, CD8(+)-epitopic peptide (C39) (core 39-48; RRGPRLGVRA) of HCVcp were compared in immunized animals. Proper expression of the fused protein by pCHCORE in transiently transfected HEK 293T cells and in the expected size (around 50 kDa) was confirmed by western blotting. The immunization results indicated that the pCHCORE shifted the immune responses pathway to Th1 by enhancing the IFN-γ cytokine level much higher than protein immunization while the proliferative and CTL responses were comparable (or slightly in favor of DNA immunization). Fusion of HBsAg to HCVcp in the context of a DNA vaccine modality could augment Th1-oriented cellular and CTL responses toward a protective epitope, comparable to that of HCVcp (subunit HCV vaccine) immunization.