Immunogenicity of Peptides Reproducing Conserved B-cell Epitopes of Hepatitis C Virus Antigens

Objective: Hepatitis C virus (HCV) is characterized by high genetic variability, which complicates the development of vaccines that protect against all viral genotypes and subtypes. Therefore, studying the immunogenicity of conserved B-cell epitopes is an important task. The aim of this study was to synthesize and analyze seven peptides reproducing conserved B-cell epitopes of HCV structural and nonstructural proteins: E1(313–327), E2(412–422), E2(434–446), E2(524–535), Core(1–17), NS4A(1689–1711), and NS4B(1722–1739). Methods: The selected peptides were obtained by solid-phase peptide synthesis using the Fmoc-strategy with high purity (>95%). To enhance peptide immunogenicity, liposomal formulations based on soybean phosphatidylcholine were constructed. To evaluate immunogenicity, BALB/c mice were immunized with the following preparations: peptides in saline, peptides with incomplete Freund's adjuvant (IFA), and liposomal formulations of the peptides. Antibodies against the peptides were detected by solid-phase enzyme-linked immunosorbent assay (ELISA). Results and Discussion: Liposomal nanoparticles containing the peptides were homogeneous, with an average size of 170–205 nm, high peptide entrapment efficiency (61–86%), and long-term stability. Analysis of mouse sera after immunization with peptides in saline revealed no humoral immune response. The use of IFA led to antibody production against only two peptides (E2(524–535) and NS4A(1689–1711)), with low titers (up to 1:56). In contrast, immunization with liposome-encapsulated peptides induced antibody production against five peptides (E2(434–446), E2(524–535), Core(1–17), NS4A(1689–1711), and NS4B(1722–1739)), with titers ranging from 1:24 to 1:448. Conclusions: These results demonstrate that liposomal peptide formulations are an effective strategy for enhancing the immunogenicity of HCV B-cell epitopes. This study provides a promising foundation for the development of a multi-epitope hepatitis C vaccine.