[Cloning and functional analysis of promoter pagC from attenuated Salmonella typhimurium]

This study describes the cloning and function of promoter pagC (P(pagC)) from Salmonella typhimurium. The expression plasmid containing the in vivo-inducible promoter pagC and HGV-NS3 gene was introduced into the attenuated Salmonella typhimurium SL7207 to investigate the function of P(pagC). The expressed HGV-NS3 protein was detectable by SDS-PAGE and Western blotting in the recombinant bacteria in the presence of low concentration of Mg2+ (<50 mmol/L). When the concentration of Mg2+ reached to 50 mmol/L, the amount of expressed HGV-NS3 was decreased significantly. The recombinant bacteria were multiplied in LB medium containing 50 mmol/L of Mg2+ and used as a DNA vaccine to orally inoculate C57 mice for three times. The results of serum antibodies, T lymphocyte proliferative response and cytotoxic T lymphocyte response of immunized mice showed that the oral vaccine could iuduce strong humoral and cellular immune responses in mice, which indicates that the P(pagC) is a strong in vivo-inducible promoter and can be used in attenuated Salmonella typhimurium to construct an effective oral vaccine.