Immunization with the ferric iron-binding periplasmic protein HitA provides protection against Pseudomonas aeruginosa in the murine infection model.

Pseudomonas aeruginosa is a notorious pathogen with increasing multi-drug resistance. This situation makes it urgent to develop a prophylactic vaccine against this pathogen. Different virulence factors play a crucial role in P. aeruginosa infection. This study focused on evaluation of the iron acquisition protein HitA as a potential vaccine candidate against P. aeruginosa in a murine infection model. The recombinant ferric iron-binding periplasmic protein HitA was overexpressed in Escherichia coli and was purified using metal affinity chromatography. The purified antigen was administered to mice in combination with Bacillus Calmette-Guérin (BCG) as an adjuvant using different vaccination regimens. Serum samples were tested for IgG1, IgG2a and total IgG antibody responses which were extremely significant. Following challenge of mice with P. aeruginosa, there was a significant reduction in bacterial load in lungs of immunized mice compared to negative control mice. Opsonophagocytic assay supported the previous results. In addition, histopathological examination of livers of challenged mice showed a significant improvement difference between immunized mice and negative control mice in various histopathological parameters. Up to our knowledge, this is the first report that investigates HitA as a potential vaccine antigen. Overall, the results of this study demonstrate the protective effect of HitA recombinant protein and highlight its importance as a promising vaccine candidate against P. aeruginosa infection.