Abstract
Many new vaccine candidates comprising purified recombinant proteins or synthetic peptides offer substantial advantages over inactivated microorganism vaccines in terms of safety and ease of manufacturing. But protein/peptide-based vaccines in most cases have low immunogenicity and need adjuvant to elicit protective and long-lasting immune responses. Water-in-oil emulsions have been evaluated and achieved long-term protective immune responses. However, this type of emulsions are crowded in the oily phase and causing local reactions at the site of injection. On contrary, it is well documented that the oil-in-water emulsions like MF59 can quickly induce and create immunocompetent environment at the site of injection. In this study, we prepared different emulsion formulations using non-ionic surfactants (PEG-b-PLACL, Tween®80 and Span®85) with various hydrophilic-lipophilic balance values of the surfactant systems under the optimized manufacturing procedure. Furthermore, we attempted to examine the effects of the surfactant components and manufacturing process of the prepared emulsion formulations on the physicochemical characteristics (including stability, electrolytic conductivity, microscopic aspects, size distribution, in vitro release and in vivo distribution) and adjuvant activity (including B-cell immunoassays and T-cell immunoassays). After the optimization of emulsification procedure, the homogeneous nanoparticles were obtained in the emulsions and we also found that the physicochemical properties and the immunogenicity of formulated vaccines are strongly influenced by the compositions and manufacture process. These results were obtained in this study with potential features provide experiment evidences and suggest strategies for the design of effective antigen delivery and vaccine development.