Protective efficacy of recombinant exotoxin A--flagellin fusion protein against Pseudomonas aeruginosa infection.

Pseudomonas aeruginosa is an opportunistic bacterium that causes serious nosocomial infection in immunocompromised patients. The aim of this study was to prepare a fusion protein consisting of exotoxin A (ExoA) and flagellin (Fla) from P. aeruginosa and to evaluate its potential as a vaccine candidate against P. aeruginosa infection. The genes encoding for ExoA and Fla proteins were cloned in-frame and expressed in Escherichia coli. The recombinant ExoA-Fla fusion protein was purified by Ni-NTA affinity chromatography. Mice were immunized subcutaneously with ExoA, Fla, and ExoA-Fla fusion proteins, and the humoral immune response was evaluated by ELISA method. The immunized and control group mice were challenged with a 2× LD50 (7.5 × 10(7) CFU) of P. aeruginosa for the protection assay. The results indicated that vaccination with Fla, ExoA, and ExoA-Fla fusion proteins produced a significant amount of specific immunoglobulin G antibodies. Immunization of mice with ExoA-Fla fusion protein showed significant protection against intraperitoneal challenge with 7.5 × 10(7) CFU (2× LD50) P. aeruginosa. Results of this study suggest that recombinant ExoA-Fla fusion protein is a highly immunogenic protective protein showing promise as a vaccine candidate against P. aeruginosa.