The invention provides a method of activating hepatitis C virus (HCV)-specific T cells, including CD4.sup.+ and CD8.sup.+ T cells. HCV-specific T cells are activated using fusion proteins comprising HCV NS3, NS4, NS5a, and NS5b polypeptides, polynucleotides encoding such fusion proteins, or polypeptide or polynucleotide compositions containing the individual components of these fusions. The method can be used in model systems to develop HCV-specific immunogenic compositions, as well as to immunize a mammal against HCV.