Testing of a novel liposomal anti-Pseudomonas vaccine based on outer-membrane protein F (OprF) of Pseudomonas aeruginosa

Abstract Pseudomonas aeruginosa is an opportunistic pathogen associated with an increased risk of morbidity and mortality among cystic fibrosis patients and immunocompromised individuals. Current antibiotics in the market are not successful against P. aeruginosa infections due to the pathogen’s ability to cause antibiotic resistance. Therefore, our prime objective is to formulate a liposomal-based anti-Pseudomonas vaccine that can produce long-lasting IgG antibodies and T cell memory. The vaccine we introduced accommodates several B cell epitopes of the outer-membrane protein F (OprF) of P. aeruginosa. The recombinant OprF antigen was conjugated with a Toll-like receptor 2/1 (TH1/TH2) agonist, Pam 3CysSK 4, and formulated into dipalmitoylphosphatidylcholine (DPPC)/cholesterol (Chol) liposomes. Our results show that the resulting vaccine conjugate can successfully produce high anti-OprF antibody titers in mice. These antibodies can also recognize intact P. aeruginosa bacteria and kill them with the support of rabbit complement and murine macrophage RAW264.7 cells. To further enhance the vaccine efficacy, the liposome was optimized with 2-dimyristoyl-sn-glycerol-3-phosphocholine (DMPC), 1,2-dimyristoyl-sn-glycerol-3-phospho-(1′-rac-glycerol) (DMPG), Chol, Pam 3CysSK 4and Quillaja Saponaria-derived saponin adjuvant QS21. The mice immunized with the modified vaccine elicit higher antibody titers and increased IgG 2a antibodies. Overall, our liposomal vaccines were found to be highly effective at generating a balanced and robust TH1/TH2 response. Supported by grants from NIH (R01AI148570)