Effective Induction of Type 1 Cytotoxic T Cell Responses in Mice with DNA Vaccine Encoding Two Hepatitis C Virus Cytotoxic T Lymphocyte Epitopes

The aims of this study were to explain whether a multiple cytotoxic T lymphocyte (CTL) epitope-based anti-hepatitis C virus (HCV) DNA vaccine can induce specific CTL responses to each HCV CTL epitope independently and long-term CD8⁺ T cell memory responses, and to determine the cytokine secretion pattern and subtype of epitope-specific cytotoxic T cells. A multi-CTL epitope gene, which consists of two epitopes of HCV (H-2^d-restricted HCV core_133–142 and E1_315–322), was cloned into the eukaryotic expression vector pcDNA3.1. BALB/c mice (H-2^d restricted) were vaccinated intramuscularly with this multi-CTL epitope-based DNA vaccine. The epitope-specific CTLs against target cells (P815,H-2^d restricted) pulsed with various CTL epitope peptides were detected by lactate dehydrogenase release assay, and the precursor frequency of epitope-specific CTLs was determined by limiting dilution analysis. Cytokines (interleukin [IL]-2, IL-4, and interferon-) in culture supernatants were determined by enzyme-linked immunosorbent assay. The multi-CTL epitope-based DNA vaccine directed against two HCV CTL epitopes could induce specific CTL responses to each of the two CTL epitopes independently and long-term CD8⁺ T cell memory responses. The epitope-specific cytotoxic T cells produced helper T cell type 1 cytokines. This work demonstrated that multiepitope DNA vaccination is a potential strategy to control HCV infection.