Conjugation to gold nanoparticles improves antigen immunogenicity

The effectiveness efficacy of a gold nanoparticle delivery system for the the rF1 plague antigen was assessed by immunising mice with a coupled vaccine formulation. In this study, we describe a method for conjugating a capsular protein (F1-antigen) from Yersinia pestis onto gold nanoparticles as a potential delivery vehicle for subunit vaccines. The gold nanoparticles used in the experiment were 15 nm citrate-reduced particles and were decorated with the antigen using Nhydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide coupling chemistry and characterised. The immunogenicity was assessed in BALB/c mice showing that F1-antigen conjugated 15 nm gold nanoparticles produced an enhanced specific IgG response compared with the unconjugated nanoparticle control, The IgG-specific antibody titre was further elevated when the F1functionalised nanoparticles were co-administered with an alhydrogel adjuvant. The antisera raised competiatively displaced antibodies from an rF1 previously identified protective Macaque serum?. When delived in in PBS without an adjuvant, the F1 conjugated gold nanoparticles induced a significantly increased IgG2a response compared with unconjugated F1 in PBS (p<0.05). The conjugation of F1 to gold nanoparticles altered the IgG1: IgG2a ratio from 14.04 for F1/PBS to 6.72 for F1 conjugated to gold nanoparticles and administered in PBS (p<0.01). All treatment groups developed a cellular memory response to F1, the polarity of which was inflenced by formulation in alhydrogel.