Increased Immunogenicity and Protective Efficacy of a P. aeruginosa Vaccine in Mice Using an Alum and De-O-Acylated Lipooligosaccharide Adjuvant System

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen that commonly causes fatal infections in cystic fibrosis and burn patients as well as in patients who are hospitalized or have impaired immune systems. P. aeruginosa infections are difficult to treat owing to the high resistance of the pathogen to conventional antibiotics. Despite several efforts, no effective prophylactic vaccines against P. aeruginosa are currently available. In this study, we investigated the activity of the CIA06 adjuvant system, which is composed of alum and de-O-acylated lipooligosaccharide, on a P. aeruginosa outer membrane protein (OMP) antigen vaccine in mice. The results indicated that CIA06 significantly increased the antigen-specific IgG titers and opsonophagocytic activity of immune sera against P. aeruginosa. In addition, the antibodies induced by the CIA06-adjuvanted vaccine exhibited higher cross-reactivity with heterologous P. aeruginosa strains. Finally, mice immunized with the CIA06-adjuvanted vaccine were effectively protected from lethal P. aeruginosa challenge. Based on these data, we suggest that the CIA06 adjuvant system might be used to promote the immunogenicity and protective efficacy of the P. aeruginosa OMP vaccine.