Lyophilized liposomes as shelf items for the preparation of immunogenic liposome-peptide conjugates

The conjugation of peptides to liposomes, while relatively simple, does represent a technical hurdle to some laboratories wishing to use such liposomes as vehicles to render peptides immunogenic. For such laboratories, having liposomes available as shelf items instead of having to prepare liposomes each time they are required may make liposomes more attractive. In this paper we report that small unilamellar liposomes bearing maleimide groups at their surface, and containing the adjuvant monophosphoryl lipid A, can be lyophilized and stored without loss of functionality or biological activity. On rehydration, peptides bearing cysteine residues are readily attached and the resulting conjugates exhibit the same immunogenicity as freshly prepared liposomes. These constructs avoid the use of protein carriers and also the use of Freund's adjuvant for raising antibodies against peptides.