Vaccine entrapment in liposomes

The use of liposomes as carriers of peptide, protein, and DNA vaccines requ ires simple, easy-to-scale-up technology capable of high-yield vaccine entr apment. Work from this laboratory has led to the development of techniques that can generate liposomes of various sizes, containing soluble antigens s uch as proteins and particulate antigens (e.g., killed or attenuated bacter ia or viruses), as well as antigen-encoding DNA vaccines, Entrapment of vac cines Is carried out by the dehydration-rehydration procedure which entails freeze-drying of a mixture of "empty" small unilamellar vesicles and free vaccines. On rehydration, the large multilamellar vesicles formed incorpora te up to 90% or more of the vaccine used. When such liposomes are microflui dized In the presence of nonentrapped material, their size is reduced to ab out 100 nm in diameter, with much of the originally entrapped vaccine still associated with the vesicles. A similar technique applied for the entrapme nt of particulate antigens (e.g., Bacillus subtilis spores) consists of fre eze-drying giant vesicles (4-5 mu m in diameter) in the presence of spores. On rehydration and sucrose gradient fractionation of the suspension, up to 30% or move of the spores used are associated with generated giant liposom es of similar mean size. (C) 1999 Academic Press.