Enhancement of the immune response by codelivery of hepatitis C virus recombinant DNA and proteins of the replicative complex

The plasmids encoding amino acid sequences corresponding to the hepatitis C virus (HCV) are regarded as promising candidates for anti-HCV vaccines. However, the optimal composition of these vaccines has not been determined. The goal of this work was to evaluate the immune response after immunization of mice with the DNA construct pcNS3-NS5B encoding proteins that constitute the viral replicative complex combined with the recombinant nonstructural proteins NS3 and NS5B using various adjuvants. DBA mice were immunized with the DNA construct and/or recombinant proteins three times. The antibody response was evaluated using ELISA. The cell immunity was determined using a lymphocyte proliferation test in vitro and by production and secretion of IFNγ and IL-2 measured by ELISpot and ELISA. It was found that the pcNS3-NS5B plasmid induced predominantly T-cell response, whereas the recombinant NS3 and NS5B proteins stimulated a potent humoral immune response. This made it possible for us to show for the first time statistically significant stimulation of both humoral and cell immunity after immunization with the pcNS3-NS5B plasmid in combination with the NS3 and NS5B HCV proteins. It was noteworthy that the animals developed the immune response not only to the NS3 and NS5B proteins, but also to other antigens encoded by the pcNS3-NS5B plasmid (NS4, NS5A). The most pronounced immune response was observed in mice subjected to triple immunization with the pcNS3-NS5B plasmid in combination with the gene adjuvant pcGM-CSF and recombinant proteins (NS3 and NS5B), which were injected together with IFNα. The adjuvant activity of the recombinant protein IFNα, which was shown in a model of the HCV genes and proteins for the first time, may be a prerequisite for including it in a candidate vaccine.