Oral immunization with HCV-NS3-transformed Salmonella: Induction of HCV-specific CTL in a transgenic mouse model

Background & Aims: The ability to induce cytotoxic T cells is considered an important feature of a candidate hepatitis C virus (HCV) vaccine. We used an oral immunization strategy with attenuated HCV-NS3-transformed Salmonell a typhimurium to deliver DNA directly to the gut-associated lymphoid tissue . Methods: HLA-A2.1 transgenic mice were immunized once with transformed at tenuated Salmonella. HCV-specific CD8(+) T cells were analyzed in vitro as well as in vivo by challenge of mice with recombinant HCV-NS3 vaccinia viru s. Results. Salmonella (10(8) colony-forming units; 20 mug plasmid DNA) ind uced cytotoxic and IFN-gamma -producing CD8+ T cells specific for the immun odominant epitope NS3-1073 in 26 of 30 mice (86%) that persisted for at lea st 10 months. A second epitope (NS3-1169) was also recognized by cytotoxic and IFN-gamma -producing T cells, whereas a third. one (NS3-1406) stimulate d IFN-gamma production without cytotoxicity. The minimal amount of: plasmid DNA required to induce CTLs was 2 ng. Upon challenge with recombinant HCV- NS3- expressing vaccinia virus, vaccinia titers were significantly lower in mice immunized with Salmonella-NS3 than in mice immunized with control Sal monella, demonstrating the in vivo function of CTLs. Conclusions:, Oral imm unization with attenuated Salmonella typhimurium as a carrier for HCV DNA i nduces long-lasting T-cell responses.