Open AccessSalmonellaVaccine Vectors Displaying Delayed Antigen SynthesisInVivoTo Enhance Immunogenicity
Author(s) -
Shifeng Wang,
Yuhua Li,
Giorgio Scarpellini,
Wei Kong,
Huang Shi,
Chang Ho Baek,
Bronwyn M. Gunn,
Soo Young Wanda,
Kenneth L. Roland,
Xin Zhang,
Patti Senechal-Willis,
Roy Curtiss
Publication year - 2010
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.00444-10
Subject(s) - immunogenicity , biology , antigen , immune system , lac repressor , microbiology and biotechnology , virology , titer , antibody , plasmid , lac operon , gene , biochemistry , immunology
We have developed a regulated delayed antigen synthesis (RDAS) system for use in recombinant attenuatedSalmonella 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-regulatedaraC 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 thelacI 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 initialin vitro assessment and theStreptococcus pneumoniae PspA protein for validation of our system in mice. All RASV strains expressing PspA generated high antilipopolysaccharide antibody titers, indicating that expression oflacI 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 virulentS. pneumoniae . These results suggest that regulated delayed antigen synthesis is useful for improving immunogenicity of RASV strains.