Induction of humoral immune response against Pseudomonas aeruginosa flagellin(1-161) using gold nanoparticles as an adjuvant

Flagellin of Pseudomonas aeruginosa is an important vaccine candidate. N-terminal domains are highly conserved in both type a and type b flagellins. The efficacy of gold nanoparticles (AuNPs) conjugated to N-terminal domains of P. aeruginosa flagellin (flagellin(1-161)), as an immunogen in mice, has been assessed. The nanoparticles were conjugated to the recombinant protein through direct interaction of thiol molecules of the cysteines with AuNPs and formation of AuS bond. Flagellin(1-161), AuNP-flagellin(1-161), and flagellin(1-161) emulsified in Freund's adjuvant (FA: complete/incomplete Freund's adjuvant formulation) were administered subcutaneously to BALB/c mice. Mice given AuNP-flagellin(1-161) elicited high titers of anti-flagellin(1-161) antibodies compared with non-immune group and/or mice which received flagellin(1-161) without adjuvant. In whole cell ELISA, these antibodies effectively recognized the native flagellin on the bacteria. Opsonophagocytosis assay demonstrated the functional activity and specificity of anti-flagellin(1-161) antibodies raised by AuNP-flagellin(1-161) against homologous strain. All of the results were comparable with those obtained by use of FA. Taken together, this is the first report of conjugation of AuNPs to flagellin and evaluating its immune response against P. aeruginosa.