Salmonella vaccine vectors displaying delayed antigen synthesis in vivo to enhance immunogenicity

Shifeng Wang, Yuhua Li, Giorgio Scarpellini, Wei Kong, HuoYing Shi, Chang Ho Baek, Bronwyn Gunn, Soo Young Wanda, Kenneth L. Roland, Xin Zhang, Patti Senechal-Willis, Roy Curtiss

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


We have developed a regulated delayed antigen synthesis (RDAS) system for use in recombinant attenuated Salmonella vaccine (RASV) strains to enhance immune responses by reducing the adverse effects of high-level antigen synthesis. This system includes a chromosomal repressor gene, lacI, expressed from the arabinose-regulated araC PBAD promoter. LacI serves to regulate expression from a plasmid promoter, Ptrc, that directs antigen synthesis. In the presence of arabinose LacI is produced, which binds to Ptrc, blocking antigen synthesis. In vivo, an arabinose-poor environment, the concentration of LacI decreases with each cell division, allowing increased antigen synthesis. To optimize the system and for comparison, we altered the lacI ribosome-binding site, start codon, and/or codon content to construct RDAS strains χ9095, χ9959, and χ9241, synthesizing from low to high levels of LacI, respectively, and non-RDAS strain χ9555 as a control. We evaluated this system with two test antigens, the green fluorescent protein for initial in vitro assessment and the Streptococcus pneumoniae PspA protein for validation of our system in mice. All RASV strains expressing PspA generated high antilipopolysaccharide antibody titers, indicating that expression of lacI did not interfere with the capacity to induce an immune response. Strain χ9241 induced significantly higher anti-PspA IgG and IgA antibody titers than strain χ9555, which expressed PspA constitutively. Anti-PspA antibody titers were inversely correlated to the level of LacI synthesis. Strain χ9241 also induced significantly greater protective efficacy against challenge with virulent S. pneumoniae. These results suggest that regulated delayed antigen synthesis is useful for improving immunogenicity of RASV strains.

Original languageEnglish (US)
Pages (from-to)3969-3980
Number of pages12
JournalInfection and immunity
Issue number9
StatePublished - Sep 2010

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases


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