DNA vaccination protects mice against challenge with Listeria monocytogenes expressing the hepatitis C virus NS3 protein

The goal of this study was to develop a new surrogate challenge model for use in evaluating protective cell-mediated immune responses against hepatitis C virus (HCV) antigens. The use of recombinant Listeria monocytogenes organisms which express HCV antigens provides novel tools with which to assay such in vivo protection, as expression of immunity against this hepatotropic bacterial pathogen is dependent on antigen-specific CD8(+) T lymphocytes. A plasmid DNA vaccine encoding a ubiquitin-NS3 fusion protein was generated, and its efficacy was confirmed by in vivo induction of NS3-specific, gamma interferon-secreting T cells following vaccination of BALB/c mice. These immunized mice also exhibited specific in vivo protection against subsequent challenge with a recombinant L. monocytogenes strain (TC-LNS3) expressing the NS3 protein. Notably, sublethal infection of naive mice with strain TC-LNS3 induced similar NS3-specific T-cell responses. These findings suggest that recombinant strains of L. monocytogenes expressing HCV antigens should prove useful for evaluating, or even inducing, protective immune responses against HCV antigens.