Immunogenicity and protective efficacy of Pseudomonas aeruginosa type a and b flagellin vaccines in a burned mouse model

• The first report of protection against P. aeruginosa infection by flagellins.
• P. aeruginosa flagellins induces antigen-specific immune responses.
• Flagellins elicits opsono-phagocytic antibodies that inhibit of P. aeruginosa motility.
• Immunization with flagellins increased production of IL-12 and suppressed IL-10.
• Flagellins immunization can improve survival rate of mice with wound infection.

Immunogenicity and efficacy of Pseudomonas aeruginosa type a and b flagellins (hereafter, flagellins) as candidate vaccines were evaluated using an experimental burned mouse model. The protection afforded and the reduction in bacterial burden achieved by these vaccine candidates were determined. Primary immunization with flagellins followed by two booster shots generated a robust immune response. Cytokine analysis demonstrated the secretion of interleukin-4 more than interferon-γ from immunized T-cells in response to in vitro antigen stimulation. IgG response was of Th2 type, predominantly with IgG1 and lower IgG2a levels before and after challenge. In vitro opsonophagocytosis assays confirmed protective potential of immune sera via enhanced bacterial cell killing. Immune sera also inhibited P. aeruginosa motility. Serum cytokine analysis demonstrated high IL-12 and low IL-10 levels in flagellin-immunized mouse sera. Reduced systemic bacterial spread from original infection site into liver and spleen was associated with increased survival. Immunization of mice with flagellins increased the humoral immune response and protection against P. aeruginosa infection in our mouse model.