Protection of interferon-gamma knockout mice against Listeria monocytogenes challenge following intramuscular immunization with DNA vaccines encoding listeriolysin O.

In this study we evaluated the efficacy of DNA vaccination of IFN-gamma knockout (GKO) mice against Listeria monocytogenes, as these immunodeficient mice are highly susceptible to infection with low numbers of this intracellular bacterial pathogen. Following intramuscular immunization of BALB/c GKO mice with plasmid DNA constructs encoding recombinant forms of the L. monocytogenes hemolysin, listeriolysin O (LLO), we detected the in vivo induction of a LLO(91-99) peptide-specific, protective immune CTL response equivalent to that observed following similar DNA vaccination of normal BALB/c mice. The observed protection represented greatly enhanced immunity for the GKO host, suggesting that DNA vaccination may provide a useful vaccine alternative for certain immunocompromised host populations.