Bioinformatics analysis and expression of a truncated form of Proteus mirabilis Pta protein as a novel vaccine target against urinary tract infection

Introduction: Pathogenic strains of Proteus mirabilis have important roles in urinary tract infection. Proteus toxic agglutinin (Pta) is amongst the most important virulence factors of P. mirabilis. This protein has a conserved sequence present in all the strains which could be evaluated as a novel vaccine target against them. The aims of the current study were the expression, purification and characterization of a truncated Pta protein of P. mirabilis strain HI4320 as well as the bioinformatics analysis of the truncated protein. Methods: The passenger domain of pta genes in P. mirabilis was evaluated by bioinformatics studies. The selected domain (residues 207-730) was amplified by PCR and cloned into pET28a expression vector. The Pta was expressed in BL21 (DE3) host and purified by Ni-NTA resin. The analyses of the purified protein were performed by SDS-PAGE and Western blotting. Results: The bioinformatics studies predicted the appropriateness of the passenger domain of Pta protein in terms of conservation, stability and cell-surface exposure. The length of PCR fragment of truncated form of pta gene was ~1500 bp. The cloning and expression of the truncated pta gene was successfully performed using pET28a-BL21 (DE3) system. Analyses of the purified Pta by SDS-PAGE and Western blotting confirmed the purification of a ~60 kDa His-tagged polypeptide. Conclusion: The high frequency of P. mirabilis infection, especially in patients with abnormalities in their urinary tracts and also the rising of antibiotic resistance among the strains of this pathogen point to the need for effective controlling measures against them. In this regard, the passenger domain of Pta could be considered as a vaccine target. The efficacy and in-vivo immunogenicity of this purified protein is currently under study.