Cationic polymers were previously shown to assemble with negatively charged proteins yielding nanoparticles (NPs). Poly-diallyl-dimethyl-ammonium chloride (PDDA) is a cationic polymer able to combine with ovalbumin (OVA) yielding a stable colloidal dispersion of OVA/PDDA NPs eliciting significant anti-OVA immune response. Dendritic Cells (DC), as sentinels of foreign antigens, exert a crucial role in the induction of antigen-specific T cell activation and consequent adaptive immune response. Objective: The present study aimed at evaluating the involvement of DCs in the adaptive immune response induced by OVA/PDDA. Methods/Results: Confirming the potent induction of adaptive immune response against OVA/PDDA, the data showed increased CD19+CD138+ plasma cells and CD19+CD38+CD27+ memory cells in spleens of mice immunized with OVA/PDDA-NPs 28 days before. OVA/PDDA-NPs also induced the migration and maturation of DCs to draining lymph nodes on days 3 and 4 of mice immunization. The in vitro results with bone-marrow differentiated DCs (iBM-DCs) showed an increase of the binding and uptake of OVA/PDDA NPs by these cells compared with soluble OVA. In addition, OVA/PDDA NPs were able to induce DC maturation and upregulation of costimulatory and MHC-II molecules, TNF- and IL-12 production. iBM-DCs incubated with OVA/PDDA NPs promoted high OVA-specific T cell proliferative response. Conclusion: Altogether, the data demonstrated the central role of DCs in the induction of antigen-specific immune response by OVA-PDDA-NPs, thus proving these NPs as potent adjuvants for subunit vaccine design.
