[Construction and characterization of Salmonella typhimurium SL7207 SifA- mutant strain]

One characteristic of Salmonella typhimurium SifA- mutant strain is to enter the cytosol of eukaryotic cells. The SifA- mutation of S. typhimurium P3H6 was transferred into S. typhimurium vaccine vector SL7207 by P22 phage transduction and the new strain was named as SL7207*. SL7207* had similar growth curve in LB medium and similar invasiveness for eukaryotic cells. It was found that SL7207* replicates within MDCK cells at a higher rate than SL7207, but is defective for replication in macrophage cell line RAW264.7. SL7207* was more attenuated than SL7207 in BALB/c mice when innoculated intraperitoneally or intravenously. SL7207*, but not SL7207, could transfer eukaryotic expression plasmid into RAW264.7 cells. These results showed that SL7207* could be a promising candidate vaccine vector to express foreign antigen or act as a eukaryotic expression plasmid carrier.