Protective efficacy of Pseudomonas aeruginosa type-A flagellin in the murine burn wound model of infection

The main goal of this study was to develop a vaccination strategy that would enhance the protective response against the recombinant type A flagellin (r-fla-A) of Pseudomonas aeruginosa in the burn wound sepsis model. Inbred mice were immunized with r-fla-A with or without alum adjuvant. The vaccinated mice were burned and challenged with P. aeruginosa. To evaluate the type of induced immune response, sera were analyzed by ELISA for total IgG, IgG1, and IgG2a isotypes. To determine the functional activity of anti r-fla IgG, opsonophagocytic killing and motility inhibition assay was performed. In vivo administration of r-fla-A afforded a remarkable improvement in survival of mice (83.3%) challenged with homologous strain (PAK) in the burn wound infection. The antibodies generated against the r-fla-A achieved 25% survival in immunized mice that had been infected with heterologous strain PAO1. Flagellin also induced high level humoral immune response via high titers of serum IgG1 in the burn and challenged mice. Anti r-fla-A antibody promoted phagocytosis of the PAK strain, and the number of viable bacterial cells decreased over 53.1%; In contrast, low opsonophagocytic killing activity (17.4%) was observed when the antiserum to r-fla-A was treated with the PAO1 strain. The anti r-fla-A antisera was able to inhibit the motility of the homologous strains; however, they did not inhibit the heterologous strains. We concluded that active immunization with recombinant type A-flagellin could protect burn mice against lethal P. aeruginosa challenge via immobilization of the pathogen which promoted the phagocytic activity.