Adjuvants are materials that can enhance the immune response of a specific antigen and prolong the immune effects induced by the antigen. The addition of an adjuvant to vaccines can enhance, sustain and direct the immunogenicity of antigens, and so reduce the amount of antigen and/or number of immunizations required....[ Read more ]

Adjuvants are materials that can enhance the immune response of a specific antigen and prolong the immune effects induced by the antigen. The addition of an adjuvant to vaccines can enhance, sustain and direct the immunogenicity of antigens, and so reduce the amount of antigen and/or number of immunizations required.

In this study, a modified swine Foot and Mouse Disease (FMD) antigen was used as a test antigen in an animal model. Two types of nanoparticles, silver nanoparticles and lipid nanoparticles, were designed and synthesized for the adjuvant testing. A novel, green method was developed in synthesizing silver nanoparticles using biopolymers, such as carboxymethylated-curdlan or fucoidan; whereas the lipid nanoparticles were derived from microbial cell wall components of Salmonella typhimurium, named monophosphoryl lipid A (MPL-ST).

In animal trials, we investigated different formulations of nanoparticles, including silver nanoparticles alone, MPL-ST alone or combined with Al(OH)₃ as adjuvants for the FMD vaccine. Our ELISA results indicated that silver nanoparticles only show a slightly enhanced effect on the vaccine functions. In contrast, MPL-ST was found to be very effective; the serum FMD-specific IgG, IgG1, IgG 2a antibody titers in the immunized mice were significantly enhanced by MPL-ST. Al(OH)₃ combined with MPL-ST induced even higher immune responses. Al(OH)₃ elicited a strong biased Th2 immune response, as evaluated by an increase in the IgG1:IgG2a ratio, while MPL-ST showed a more balanced response. Moreover, amongst all the different formulations, the use of the MPL-ST and Al(OH)₃ combination led to the induction of the highest IgG levels. This result implies that MPL-ST and Al(OH)₃ act synergistically as a potent vaccine formulation.