comparison of immunogenicity of hcv cd8-epitopes as a single epitope, mixture of epitopes and polytope peptide

objective: animal studies show that vaccination with epitope-based peptides results in protective immunity. however, immunodominance should be regarded as a major challenge in this area. considering the advantages of epitopic-vaccines against hepatitis c virus (hcv) infection, herein, we compared the occurrence of immunodominance following mice immunization with three different hcv epitopic-peptide formulations. methods: we synthesized four cd8+ epitopic-peptides (c1,e6,n,e4) that were derived from hcv-antigens. a polytope-peptide (c1e6ne4) spanning fusion of epitopes was designed based on immunoinformatics analyses for optimum proteasomal cleavage. balb/c mice received three subcutaneous injections that contained 10 µg of peptide (minimal epitopes, or mixture of four epitopes or long-polytope) formulated with cpg (50 µg) and montanide-isa720 (70%) adjuvants in the tail-base at three-week intervals. considering the h2-dd (balb/c)-restriction of c1 and e4-epitopes, three weeks after the last injection splenocytes from vaccinated animals were subjected to ifnγ/il4 elispot assays in the presence of c1 and e4-peptides. results: all vaccinated animals promoted th1-oriented responses as evidenced by detection of ifnγ-secreting cells and a low-level of il4 secretion. mice injected with minimal ctl-epitopes provoked stronger responses, however, due to the higher affinity of e4-epitope for h2-dd, frequency of e4-specific cells was considerably higher than c1-specific ones, showing some level of immunodominance. interestingly, animals vaccinated with polytope-peptide developed high-quality balanced responses against both c1and e4-epitopes, however at a lower intensity. conclusion: these results supported the superiority of polytope-peptides over minimal epitopes, yet emphasized the key role of polytope design and optimization to avoid epitope dominancy.