Background: Considering the immunosuppressive effects and prevalent mutations in some HCV antigens, induction of CD8+ T cell responses is focused on conserved and critical epitopes which as a multi-epitope vaccine can prevent the chronic nature of the disease.

Materials and Methods: Two immunodominant HLA-A2-restricted human epitopes (E2614-622 and NS31406-1415) and two H-2d-restricted mouse epitopes (core132-142 and E2405-414) were designed in a sequential tandem, predicted by immunoinformatic analyses. Following the synthesis, related nucleotide sequence was cloned into the pcDNA3.1 vector with and without the fusion of hepatitis B surface antigen (HBsAg). Two constructed plasmids (pcDNA3.1.HPOL and pcDNA3.1.POL, respectively) were evaluated for the protein expression and secretion in Cos-7 cell line. After the vaccination of BALB/c mice (n=6 in each group) with different DNA and peptide immunization regimens, CD8+ T cell activity as well as the type and protective potency of the induced responses were evaluated.

Results: Despite the induction of epitope-specific responses in pcDNA3.1.POL injected mice, the group immunized with pcDNA3.1.HPOL indicated a significant increase in the number and activity of CD8+ T cells (P<0.05). Peptide boosting of this group (formulated in two human-compatible adjuvant) still led to the more activation of CD8+ cells, induction of Th1 response and the inhibition of tumor model growth (P<0.05).

Conclusion: Fusion of HBsAg as a particle-forming sequence and the source of helper epitopes along the DNA-prime/peptide-boosting immunization regimen are proposed as two promising strategies to improve the CTL multi-epitope vaccines against HCV.