Recombinant protein vaccine PcrV-OprI prevents mice against Pseudomonas aeruginosa infection after intramedullary nailing

To establish a model of Pseudomonas aeruginosa（PA）infection in mice with open fractures after the femur with intramedullary nailing and to explore the immunoprotective effects of recombinant PcrV-OprI.

PcrV-OprI protein was expressed in E. coli, and then the target protein was purified by affinity chromatography and hydrophobic interaction chromatography. The C57BL/6J mice were immunized with PcrV-OprI protein on Day 0, 14 and 21. After that, the titers of specific IgGs and their subtypes were determined by ELISA. In 14 d after the final vaccination, open femur fractures and intramedullary nailing were performed in mice, which was followed by a challenge with PAO1 strain. The protection of PcrV-OprI was assessed with bacterial colonization, body weight, histology, and X-ray imaging.

The levels of specific antibodies were significantly higher in PcrV-OprI-immunized sera than that of the control group（P<0.05）, and the obtained IgG1 was the predominating subtype. The loss of body weight of the immunized mice was significantly lower than that of the control group（P<0.05）. In addition, a similiar trend was observed in the amount of colonized bacteria in the tissues, bones, and implants（P<0.05）. Moreover, the histological observation suggested that bacteria caused less damage in the PcrV-OprI-immunized mice. At the end of the observation period, the fracture line in immunized mice was clear, indicating gradual healing.

Vaccination of PcrV-OprI is efficient in causing a humoral immune response and shows significant protective effect on PA infection model in mice after open fractures of the femur with intramedullary nailing.