Liposomes as Adjuvants for Vaccines

摘要

Numerous reviews of liposomes as carriers of antigens and adjuvants have beenpublished since 1990. Liposomes have the advantage of being biodegradable vehicles that mimic the lipid structure of natural lipid bilayer membranes. Because of this, insoluble membrane antigens can often be reconstituted in a form that exposes purified antigenic epitopes, such as purified viral antigens, in conformations that are presumed to be similar to those found in the original organism. Liposomes are also avidly ingested by phagocytes, cells then serving as antigen-presenting cells. In addition to these natural attributes, liposomes also have the convenient characteristic of encapsulating soluble antigens and then serving as permeability barriers for slow release of the antigens. Besides antigens, additional adjuvants, such as lipid A (the lipid moiety of gram-negative bacterial lipopolysaccharide) or lipophilic muramyl dipeptide (MDP) derivatives and analogs, can be incorporated either into the lipid bilayer or encapsulated (if soluble) in the aqueous regions.