title: Induction of humoral and cellular immune responses by antigen-expressing immunostimulatory liposomes.
abstract: Recently we have shown that liposomes can be used as artificial microbes for the production and delivery of DNA-encoded antigens. These so-called antigen-expressing immunostimulatory liposomes (AnExILs) were superior in inducing antigen-specific antibodies compared to conventional liposomal protein or DNA vaccines when tested in mice after i.m. immunization. In this study, we investigated the capacity of AnExILs to induce T-cell responses. By using a plasmid vector encoding a model antigen under control of both the prokaryotic T7 and the eukaryotic CMV promoter we hypothesized that antigen production could lead to CTL activation via two distinct routes: i. production of antigens inside the AnExILs with subsequent cross-presentation after processing by APCs and ii. endogenous production of antigens after AnExIL-mediated transfection of the pDNA. Although we were not able to demonstrate transfection-mediated expression of luc-NP in mice, i.m. injection of AnExILs producing luc-NP resulted in T-cell responses against the encoded NP epitope, as determined by tetramer staining. T-cell responses were comparable to the responses obtained after i.m. injection of naked pDNA. In order to find out whether CTL activation was caused by cross-presentation of the exogenous antigens produced inside AnExILs or by endogenous antigen production from transfection with the same pDNA source a second study was initiated in which the contribution of each of these effects could be separately determined. These results demonstrate that the observed T-cell responses were not exclusively caused by cross-presentation of the AnExIL-produced antigens alone, but were rather a combination of dose-dependent antigen cross-presentation and low levels of endogenous antigen production.
authors.affiliation: Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Maryam
authors.initials: M
authors.lastname: Amidi
authors.forename: Mary J G
authors.initials: MJ
authors.lastname: van Helden
authors.forename: Neda Rafiei
authors.initials: NR
authors.lastname: Tabataei
authors.forename: Anna L
authors.initials: AL
authors.lastname: de Goede
authors.forename: Marijn
authors.initials: M
authors.lastname: Schouten
authors.forename: Volkert
authors.initials: V
authors.lastname: de Bot
authors.forename: Anastasia
authors.initials: A
authors.lastname: Lanzi
authors.forename: Rob A
authors.initials: RA
authors.lastname: Gruters
authors.forename: Guus F
authors.initials: GF
authors.lastname: Rimmelzwaan
authors.forename: Alice J A M
authors.initials: AJ
authors.lastname: Sijts
authors.forename: Enrico
authors.initials: E
authors.lastname: Mastrobattista
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000818:Animals; D000941:Antigens / Q000235:genetics* / Q000276:immunology; D005260:Female; D007111:Immunity, Cellular / Q000276:immunology*; D056724:Immunity, Humoral / Q000276:immunology*; D008081:Liposomes; D008156:Luciferases / Q000235:genetics / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D010957:Plasmids; D013601:T-Lymphocytes / Q000276:immunology; D019444:Vaccines, DNA / Q000008:administration & dosage* / Q000276:immunology; D001616:beta-Galactosidase / Q000235:genetics / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D000941:Antigens; D008081:Liposomes; D019444:Vaccines, DNA; D008156:Luciferases; D001616:beta-Galactosidase