title: Enhancing the immunogenicity of liposomal hepatitis B surface antigen (HBsAg) by controlling its delivery from polymeric microspheres.
abstract: Microencapsulated liposome systems (MELs) were investigated as a potential immunization carrier for a recombinant 22-nm hepatitis B surface antigen (HBsAg) particle. MELs were prepared by first entrapping the HBsAg particles within liposomes composed of phosphatidylcholine:cholesterol (1:1 molar ratio), which were then encapsulated within alginate-poly(L-lysine) (PLL) hydrogel microspheres. The entrapped HBsAg particles retained immunoreactivity, as judged by an enzyme-linked immunosorbent assay (ELISA). Direct imaging of HBsAg particles and HBsAg incorporated into liposomes by cryo-transmission electron microscopy (cryo-TEM) indicated that HBsAg is embedded in the liposomal membrane. The antigenic particles were released from MELs mainly within the context of liposomes. The release rates in vitro and in vivo depended on the molecular weight of PLL used for MEL coating; MELs-214, coated with 214 kDa PLL, released the liposomal HBsAg at much higher rates than MELs-25, which was coated with 25 kDa PLL. Concomitantly, the specific anti-HBsAg titers in mice receiving HBsAg in MELs-214 were higher than those induced by MELs-25. MELs-214 were more efficient than conventional liposomes or alum in eliciting higher and prolonged antibody levels in mice. The ability of MELs to provide an HBsAg depot as well as a sustained release of liposomal HBsAg suggests that these carriers may be an ideal immunoadjuvant.
authors.affiliation: Department of Biotechnology Engineering, Sherman Building, Room 217, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel.
authors.forename: M
authors.initials: M
authors.lastname: Machluf
authors.forename: R N
authors.initials: RN
authors.lastname: Apte
authors.forename: O
authors.initials: O
authors.lastname: Regev
authors.forename: S
authors.initials: S
authors.lastname: Cohen
mesh_terms: D000534:Alum Compounds; D000818:Animals; D000917:Antibody Formation / Q000276:immunology; D016466:CHO Cells; D006224:Cricetinae; D004337:Drug Carriers; D006514:Hepatitis B Surface Antigens / Q000008:administration & dosage* / Q000737:chemistry / Q000276:immunology*; D007114:Immunization; D008081:Liposomes; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D008863:Microspheres
chemical_list: D000534:Alum Compounds; D004337:Drug Carriers; D006514:Hepatitis B Surface Antigens; D008081:Liposomes; C041524:aluminum sulfate