Immunopotentiating properties of chimeric OprF-OprI-PopB protein against Pseudomonas aeruginosa PAO1 in the infected burned rat model

OBJECTIVE(S): Pseudomonas aeruginosa, as an opportunistic pathogen, is known to cause nosocomial infections among patients suffering from burn injuries and also cystic fibrosis patients. The objective of our research was to develop a novel vaccine against P. aeruginosa. MATERIALS AND METHODS: A recombinant P. aeruginosa subunit vaccine based on the outer membrane proteins, including the OprF-OprI region and its major protein in the type III secretion system, PopB (called FIB protein) was formulated. To induce a robust immune response, our preferred regions were conjugated to a carrier protein, GMCSF (Granulocyte-macrophage colony-stimulating factor). FIB protein’s immunogenicity with and without adjuvant was evaluated in vaccinated rats and also burned rat models, which were subcutaneously challenged by the PAO1 strain of P. aeruginosa. RESULTS: Antibody levels were increased in sera of rats in this study. Assessment of the resident memory CD4+ T cells in splenocytes from vaccinated rats demonstrated that the FIB conjugated with GMCSF could cause higher responses in comparison with other groups. Moreover, immunization with the FIB plus adjuvant protein could improve interferon-gamma (IFN-γ) production, interleukin 17A (IL-17A), and IL-4, contributing to elicit humoral and cellular immune responses and decreased post-infection bacterial loads after PA challenge, pathology, and inflammatory cell infiltration. CONCLUSION: These observations demonstrated that FIB conjugated with GMCSF can be a putative vaccine candidate against P. aeruginosa in burnt rat models.