Enhancement by an in vivo activated Promoter of Immunogenicity of Recombinant Attenuated Salmonella typhimurium Expressing Hepatitis C Virus Core Antigen

( Department of
Microbiology, Second Military Medical University, Shanghai 200433, China;

¹Institute of Basic Medicine, General Hospital of PLA, Beijing 100853, China;

²Department of Etiological Biology, Second Military Medical University, Shanghai
200433， China )

Abstract
The promoter of phoP activated gene C (PpagC) of Salmonella
typhimurium was cloned and used as transcriptionally regulating element for
a plasmid that expresses hepatitis C virus core antigen. The resultant plasmid
was transformed into attenuated Salmonella typhimurium SL7207 and its expression
activity in vitro was determined. Mg²⁺ inhibited the recombinant
bacteria to express HCV core antigen in a dose-dependent manner. This recombinant
strain, and another bacterial strain that constitutively expresses HCV core
antigen were orally inoculated BALB/c mice respectively. The stability of
the plasmid in the bacteria and the immune responses was analyzed. The results
showed that the in vivo activated PpagC promoter
could stabilize the plasmid in the bacteria and enhance the humoral and cellular
immune responses greatly, showing a novel way to produce effective, cheap
oral vaccine against hepatitis C.