Vectors to achieve selective expression of vaccine antigens within eukaryotic cells using Salmonella spp. as carrier strains.

A set of expression vectors was constructed which allows the expression of recombinant antigens under the control of Salmonella typhi promoters that are selectively activated after infection of eukaryotic cells. The pUC18Not derivatives contain a promoter downstream of the early transcriptional terminator from phage T7 and followed by a multiple cloning site, whereas the pBluescript II S/K derivatives contain the ribosomal RNA T(1) transcriptional terminator and also the strong translation signals of the Escherichia coli atpE gene. The expression cassettes are flanked by NotI or PacI sites to simplify their subcloning where required. The resulting vectors were validated using the S1 subunit of pertussis toxin as a model antigen and Salmonella typhimurium aroA SL7207 as a carrier. The S1 subunit was efficiently expressed by recombinant Salmonella within Henle 407 cells.