Comparison of Immunogenicity of HCV CD۸-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 CD۸+ epitopic-peptides (C۱,E۶,N,E۴) that were derived from HCV-antigens. A polytope-peptide (C۱E۶NE۴) spanning fusion of epitopes was designed based on immunoinformatics analyses for optimum proteasomal cleavage. BALB/c mice received three subcutaneous injections that contained ۱۰ µg of peptide (minimal epitopes, or mixture of four epitopes or long-polytope) formulated with CpG (۵۰ µg) and Montanide-ISA۷۲۰ (۷۰%) adjuvants in the tail-base at three-week intervals. Considering the H۲-Dd (BALB/c)-restriction of C۱ and E۴-epitopes, three weeks after the last injection splenocytes from vaccinated animals were subjected to IFNγ/IL۴ ELISpot assays in the presence of C۱ and E۴-peptides. Results: All vaccinated animals promoted Th۱-oriented responses as evidenced by detection of IFNγ-secreting cells and a low-level of IL۴ secretion. Mice injected with minimal CTL-epitopes provoked stronger responses, however, due to the higher affinity of E۴-epitope for H۲-Dd, frequency of E۴-specific cells was considerably higher than C۱-specific ones, showing some level of immunodominance. Interestingly, animals vaccinated with polytope-peptide developed high-quality balanced responses against both C۱and E۴-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.

کلیدواژه ها:

HCV ، peptide vaccine ، epitope ، immunodominance ، polytope ، ویروس هپاتیت C ، واکسن پپتیدی ، اپیتوپ ، غلبه ایمنولوژیکی ، پلیتوپ