Figure 4.

Liposomal vaccine uptake mechanisms. (A) Endocytosis: uptake of vaccine carrier by cell; (B) membrane fusion: fusion of vaccine carrier and cell membranes and release of vaccine particles into cytoplasm; (C) extra cellular content release: (C.1); active targeting: releasing vaccine particles near cell membrane after targeting via ligand-receptor connection. (C.2); passive targeting: release of vaccine particles near cell membrane; (D) lipophilic components transferation: transfer of lipophilic vaccine particles through cell membrane after carrier ligand-receptor binding.