Cloning, expression and characterization of recombinant exotoxin A-flagellin fusion protein as a new vaccine candidate against Pseudomonas aeruginosa infections.

Infections due to Pseudomonas aeruginosa are among the leading causes of morbidity and mortality in patients who suffer from impaired immune responses and chronic diseases such as cystic fibrosis. At present, aggressive antibiotic therapy is the only choice for management of P. aeruginosa infections, but emergence of highly resistant strains necessitated the development of novel alternative therapeutics including an effective vaccine. Several P. aeruginosa antigens have been tested for vaccine development, including lipopolysaccharide alone, polysaccharides alginate, extracellular proteins, exotoxin A (exo A) and killed whole cell. However, none of them are currently available clinically. In this research, recombinant exoA-flagellin (fliC) fusion protein as a cocktail antigen was expressed and purified and its antigenic characteristics were evaluated. Expression of recombinant fusion protein by E. coli using pET22b vector resulted in production of exoA-fliC fusion protein in high concentration. Based on Western-blotting results, recombinant fusion protein showed a good antigenic interaction with sera from patients with various P. aeruginosa infections. These results suggested that recombinant exoA-fliC fusion protein can be produced in the laboratory, and tested as a candidate vaccine in P. aeruginosa infections.