Induction of Protective Immunity to Listeria monocytogenes by Immunization with Plasmid DNA Expressing a Helper T-Cell Epitope That Replaces the Class II-Associated Invariant Chain Peptide of the Invariant Chain

Listeria epitope-specific helper T (Th) cells were able to be primed and induced in vivo by immunization with a plasmid carrying an invariant chain (Ii) gene whose class II-associated invariant chain peptide (CLIP) region was replaced by a Listeria Th epitope. Immunization of C3H/He mice with an Ii-LLO 215-226 plasmid induced specific interferon-γ- and interleukin 2-producing Th cells and conferred significant protective immunity against listerial infection.