Preparation and immunological properties of a nanovaccine against Pseudomonas aeruginosa based on gold nanoparticles and detoxified lipopolysaccharide

Pseudomonas aeruginosa is one of the most important bacterial pathogens in immunocompromised patients, and the lipopolysaccharide (LPS) of this organism is a key factor in virulence and both innate and acquired host responses to infection. In this study, we prepared a nanoconjugate vaccine composed of P. aeruginosa detoxified lipopolysaccharide (D-LPS) and gold nanoparticles (Au NPs) and evaluated its potential as a vaccine candidate against P. aeruginosa infections. LPS from P. aeruginosa strain PAO1 was extracted by the hot phenol method with some modifications and then detoxified. Au NPs were synthesized by the reduction of hydrochloroauric acid trihydrate by sodium borohydride and then coupled to D-LPS via electrostatic interaction. Mice were subcutaneously injected in the tail base with 20 µg of D-LPS, D-LPS-Au NPs, Au NPs, and PBS. IgG titers were evaluated by ELISA and whole-cell ELISA methods. The immunized and control group mice were challenged with a 2×LD50 (7.5×107 CFU) of P. aeruginosa strain PAO1.   Mice vaccinated with D-LPS and D-LPS-Au NPs elicited a significant amount of IgG antibodies. Nanoconjugated LPS generated a significantly higher antibody titer compared with D-LPS alone. Also, immunization of mice with D-LPS-Au NPs increased survival times against challenge with 7.5×107 CFU (2×LD50) of P. aeruginosa strain PAO1.   Our results showed that the suggested vaccine composed of P. aeruginosa D-LPS and Au NPs had a significant potential to protect against P. aeruginosa infections.