Even though we have demonstrated a vigorous immune response following i.v. infection the immune response to Listeria can vary considerably depending on the route of administration. Using the intraperitoneal route of infection, we obtained a similar result i.e. protection following pre-infection with the Lm and L. inn::vgc strains but not with mice pre-immunized with the L. inn strain (Fig. S2) . Thus despite a different route of infection Lm::vgc is able to induce protection in-vivo. The mouse is not a suitable and reproducible model for evaluating oral immunization protocols because of the specificity of the listerial InlA molecule [38] . Therefore experiments examining mucosal immunity will have to be carried out in the guinea pig model of listerial infection.