Nano-structured Vaccine Delivery

The nano-structured vaccine delivery system, containing tomatine, n-octyl-β-Dglucopyranoside (OGP), phosphatidylethanolamine (PE), cholesterol, and ovalbumin (OVA), was examined in the present study. Transmission electron microscopy (TEM) and fluorescence microscopy were carried out to examine the nano-structures of this complex vaccine delivery system and its interactions with the antigen-presenting cells (APCs). The adjuvant was prepared and separated by isopycnic ultracentrifugation. Examination by transmission electron microscopy revealed the heterogeneity characteristics, containing several microand nanostructures with the major fraction containing needleand rod-shaped nanoparticles of approximately 80-160 nm in width and 2-4 μm in length. Tomatine alone in 0.9% NaCl, on the other hand, was shown to be cylindrical crystals of hundreds of nanometers up to a few micrometers in length. The nano-gel structures were speculated to correlate with the immunostimulating effect of the adjuvant. To examine the roles of the adjuvant in antigen delivery, dendritic cells (DCs) were isolated from bone marrows of mice and cocultured with tomatine adjuvant containing the fluorochrome-labeled antigens (Ags). Confocal fluorescence microscopic examination demonstrated the uptake of tomatine-antigen complexes by the DCs, suggesting the roles of the nano-structured vaccine adjuvant in antigen delivery.