Mannosylated liposomes appear to be a promising and potential carrier system for delivery of proteins, peptides, or nucleic acids. The present chapter describes novel mannosylated liposomes, which increase the intracellular targeting of immunogen to dendritic cells and macrophages possessing the specific receptors. The liposomes used in the present investigation were prepared by hand-shaken method and characterized for size, shape, surface charge, encapsulation efficiency, ligand binding, and specificity and uptake studies. The immune-stimulating activity of the liposomes was studied by measuring antigen-specific antibody titer following subcutaneous administration of different liposomal formulations in BALB/c mice. It was found that O-palmitoyl mannan (OPM)-coated liposomes showed better uptake efficiency. In vivo studies revealed that the OPM-coated liposomes exhibited significant higher serum antibody response and stronger TH1/TH2-based cellular responses. In conclusion, novel vesicular constructs are useful nanosized carriers having superior surface characteristics--for active interaction with the antigen-presenting cells and subsequent processing and presentation of antigen.