Heterologous prime–boost immunizations with different Salmonella serovars for enhanced antigen-specific CD8 T-cell induction

Summary Pre-existing anti-vector immunity can severely compromise the ability of Salmonella enterica serovar Typhimurium live vaccines to induce protective CD8 T-cell frequencies after type III secretion system-mediated heterologous protein translocation in orally immunized mice. In the present study, we demonstrate that heterologous prime–boost immunizations using attenuated serovar Typhimurium and serovar Dublin strains for foreign antigen delivery can be employed to bypass anti- Salmonella immunity resulting in enhanced antigen-specific CD8 T-cell induction. This desirable effect can be explained by the fact that, in contrast to homologous prime–boost immunizations, vaccination with different Salmonella serovars is characterized by long-lasting colonization of mice by both live carrier vaccines.