Abstracts (complete list) - Wissenschaft Online

Anne Endmann, Dirk Bumann, Susanne zur Lage, Marcin Lyszkiewicz, Siegfried Weiss,
Holger Lößner
Novel Salmonella vaccine strains with in vivo amplifiable
antigen expression plasmids
Live attenuated Salmonella enterica serovars are explored as mucosal vectors for the
delivery of heterologous antigens or DNA vaccines. Conventional expression systems
are based on maintenance of the expression plasmids at multi-copy numbers
representing a high metabolic burden for the bacteria. We have developed a novel
Salmonella vaccine strain with amplifiable expression plasmids bearing two replication
origins. The first replicon derived from the F factor or plasmid pSC101 ensures the
minimal-copy number state. A second medium-copy replicon derived from plasmid RK2
is responsible for conditional amplification of the expression plasmids under control of
Salmonella-specific in vivo inducible promoters. This replicon mediated strong
amplification of the plasmid copy number up to 50-100 copies. Consequently, enhanced
expression of plasmid-encoded antigen was observed in vitro and in vivo. Furthermore,
the expression level of the antigen could be further increased and tightly controlled in
vivo by regulating its transcription via in vivo inducible promoters at the same time. The
novel Salmonella vaccine strains were assessed regarding their colonization properties
after oral administration and their immunogenicity in an adoptive transfer model.
Intravenous immunization with such novel strains resulted in substantial ovalbuminspecific
CD4+ T cell responses.