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

Abstract

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 × 107 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 × 107 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.