title: The effect of cholesterol in a liposomal Muc1 vaccine.
abstract: A liposomal Muc1 mucin vaccine for treatment of adenocarcinomas was formulated by incorporating a synthetic Muc1 mucin-based lipopeptide and Lipid A into a DPPC/cholesterol bilayer. Vaccination of mice with the liposomal formulation produced a peptide-specific immune response dependent on the cholesterol content. The response occurred at a threshold of 20-23 mol% cholesterol, and was optimal at cholesterol levels of > or =30 mol%. To understand this cholesterol dependency, we studied the effect of cholesterol on the liposomal bilayer and surface properties. Freeze-fracture electron microscopy showed a unique surface texture that was codependent upon cholesterol (> or =20 mol%) and lipopeptide content. Fluorescence anisotropy measurements exhibited a significant decrease in the rotational motion of 1,6-diphenyl-1,3,5-hexatriene in formulations containing >20 mol% cholesterol and only in the presence of the lipopeptide. At 20 mol% cholesterol and with lipopeptide, DSC showed a significant increase in the main phase transition of the DPPC bilayers, while Raman spectroscopy indicated a more ordered arrangement of DPPC molecules compared to control liposomes containing DPPC/cholesterol alone. Taken together, the data suggest the presence of lipopeptide-rich microdomains at and above a threshold of 20 mol% cholesterol that may play a role in the induction of a peptide-specific immunological response.
authors.affiliation: Biomira USA, Inc., 1002 Eastpark Boulevard, Cranbury, NJ 08512, USA. mbatenjany@biomira.com
authors.forename: M M
authors.initials: MM
authors.lastname: Batenjany
authors.forename: L T
authors.initials: LT
authors.lastname: Boni
authors.forename: Y
authors.initials: Y
authors.lastname: Guo
authors.forename: M E
authors.initials: ME
authors.lastname: Neville
authors.forename: S
authors.initials: S
authors.lastname: Bansal
authors.forename: R J
authors.initials: RJ
authors.lastname: Robb
authors.forename: M C
authors.initials: MC
authors.lastname: Popescu
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D016880:Anisotropy; D002152:Calorimetry, Differential Scanning; D019496:Cancer Vaccines / Q000008:administration & dosage / Q000737:chemistry* / Q000276:immunology; D002784:Cholesterol / Q000032:analysis / Q000737:chemistry*; D004337:Drug Carriers; D005454:Fluorescence Polarization; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000032:analysis; D008050:Lipid A / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry*; D008198:Lymph Nodes / Q000276:immunology; D008214:Lymphocytes / Q000276:immunology; D051379:Mice; D008969:Molecular Sequence Data; D018396:Mucin-1 / Q000008:administration & dosage / Q000737:chemistry* / Q000276:immunology; D010446:Peptide Fragments / Q000008:administration & dosage / Q000737:chemistry* / Q000276:immunology; D013154:Spleen / Q000276:immunology; D014611:Vaccination
chemical_list: D019496:Cancer Vaccines; D004337:Drug Carriers; D008050:Lipid A; D008081:Liposomes; C116055:MUC1 tandem repeat peptide; D018396:Mucin-1; D010446:Peptide Fragments; D015060:1,2-Dipalmitoylphosphatidylcholine; D007371:Interferon-gamma; D002784:Cholesterol