Salmonella-mediated oral DNA vaccination using stabilized eukaryotic expression plasmids

Area of Science:

• Molecular Biology
• Immunology
• Vaccinology

Background:

• Salmonella vectors are promising for delivering plasmid-encoded antigens to host cells.
• Plasmid instability in Salmonella transformants limits their broad application.
• High copy number plasmids often exhibit poor stability in bacterial systems.

Purpose of the Study:

• To engineer more stable Salmonella-based expression systems.
• To evaluate the impact of low copy number plasmids on stability and immune responses.
• To assess the versatility of Salmonella for delivering multiple antigens.

Main Methods:

• Construction of novel low copy number expression plasmids using pMB1, p15A, and pSC101 replicons.
• Comparative analysis of plasmid stability (in vitro and in vivo) between high and low copy number plasmids.
• Assessment of antigen-specific CD4(+) and CD8(+) T-cell and antibody responses.
• Evaluation of protective immunity against Listeria monocytogenes using listeriolysin antigen.
• Testing Salmonella expressing two independent antigens on compatible low copy number plasmids.

Main Results:

• Low copy number plasmids (pMB1, p15A, pSC101) dramatically increased plasmid stability in Salmonella.
• Enhanced plasmid stability led to strong, reproducible induction of cellular and humoral immunity after single application.
• Protective immunity was achieved against Listeria monocytogenes.
• Salmonella transformed with compatible low copy number plasmids elicited robust responses to dual antigens.

Conclusions:

• Low copy number replicons significantly improve the stability of Salmonella-based expression vectors.
• Stable vectors enable robust and reproducible induction of immune responses, enhancing vaccine potential.
• This system offers a versatile platform for delivering single or multiple antigens for vaccine development.