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Pilin-based anti-Pseudomonas vaccines: latest developments and perspectives
H Hahn1, P M Lane-Bell, L M Glasier
1Department of Biological Sciences, University of Alberta, Edmonton, Canada.
Abstract:
Among the several adhesins produced by Pseudomonas aeruginosa (Pa), the type-4 pilus promotes the majority of the adherence capability of the bacterium to epithelial cells and it is a major virulence factor in an AB.Y/SnJ mouse infection model. Vaccines targeting the disulfide loop (DSL) adherence binding domain of the pilin protein should therefore provide an effective protection against initial colonization and infection with Pa. To selectively elicit adherence blocking antibodies, the pilin DSL domain was chosen as peptide antigen for the construction of recombinant protein and live vaccines. While synthetic peptide-carrier protein conjugates provided some strain-specific protection, chimeric proteins with N- or C-terminally fused pilin DSL peptides did not engender protective IgG titers mice. Integral fusions of the pilin DSL peptide with the minor coat protein of filamentous phage or surface exposed regions of an outer membrane protein resulted in a display of the peptide on the surface of the phage particles and bacterial cells respectively. However, in immunization studies neither of these live vaccines were effective immunogens. The paracrystalline S-layer of Caulobacter crescentus combines several advantages of an effective antigen surface display system. Recombinant S-layer proteins with singlecopy insertions of a pilin peptide did not engender significant IgG titers, whereas multiple tandem insertions of the same peptide increased the serum IgG response in mice a thousand times. Multiple insertions of DSL peptides from different frequent pilin prototypes may be an interesting alternative for a recombinant cross-protective anti-Pseudomonas vaccine.
Insights
Developing a Pseudomonas aeruginosa (Pa) vaccine is crucial. Targeting the pilin disulfide loop (DSL) showed promise, with multiple tandem insertions in Caulobacter crescentus S-layer proteins significantly boosting protective IgG titers in mice.
Area of Science:
- Microbiology
- Immunology
- Vaccine Development
Background:
- Pseudomonas aeruginosa (Pa) utilizes type-4 pilus adhesins for epithelial cell adherence, making it a significant virulence factor.
- The disulfide loop (DSL) adherence binding domain of pilin protein is a key target for blocking Pa colonization and infection.
Purpose of the Study:
- To evaluate the immunogenicity of pilin DSL peptides presented through various vaccine platforms.
- To develop an effective vaccine strategy against Pseudomonas aeruginosa by targeting its adherence mechanisms.
Main Methods:
- Constructed chimeric and integral fusion proteins, live vaccines (phage and bacterial display), and recombinant Caulobacter crescentus S-layer proteins displaying pilin DSL peptides.
- Immunized AB.Y/SnJ mice with these constructs and assessed serum IgG titers and protective immunity.
Main Results:
- Synthetic peptide conjugates offered limited strain-specific protection.
- Chimeric proteins and live vaccines (phage/bacterial display) failed to elicit significant protective IgG titers.
- Recombinant S-layer proteins with multiple tandem insertions of pilin DSL peptides resulted in a thousand-fold increase in serum IgG response.
Conclusions:
- Multiple tandem insertions of pilin DSL peptides, particularly within the Caulobacter crescentus S-layer, represent a promising strategy for a recombinant, cross-protective anti-Pseudomonas vaccine.
- Further development of S-layer based vaccines incorporating diverse pilin prototypes could enhance broad-spectrum protection against Pa infections.