Use of liposomes as an immunopotentiating delivery system: in perspective of vaccine development

Liposomes have been widely used to deliver antigens to the antigen-presenti ng cells (APCs) and also to modify their immunological behaviour in model a nimals. We recently demonstrated the potential of yeast lipid liposomes to undergo membrane-membrane fusion with cytoplasmic membrane of the target ce lls. Interestingly, studies in the present report revealed that antigen enc apsulated in yeast lipid Liposomes could be successfully delivered simultan eously into the cytosolic as well as endosomal processing pathways of APCs, leading to the generation of both CD4(+) T helper and CD8(+) cytotoxic T c ells. In contrast, encapsulation of same antigen in egg phosphatidyl-cholin e (PC) liposomes, just like its free form, has inefficient access to the cy tosolic pathway of major histocompatibility complex (MHC) I dependent antig en presentation and failed to generate antigen specific CD8(+) cytotoxic T- cell response. However, both egg PC as well as yeast lipid liposomes have e licited strong antigen specific antibody responses in immunized animals. Th ese results imply usage of liposome encapsulated antigen as potential candi date vaccine capable of eliciting both cell mediated as well as humoral imm une responses.