title: Cytosolic Delivery of Liposomal Vaccines by Means of the Concomitant Photosensitization of Phagosomes.
abstract: One of the greatest pharmaceutical challenges in vaccinology is the delivery of antigens to the cytosol of antigen-presenting cells (APCs) in order to allow for the stimulation of major histocompatibility complex (MHC) class I-restricted CD8(+) T-cell responses, which may act on intracellular infections or cancer. Recently, we described a novel method for cytotoxic T-lymphocyte (CTL) vaccination by combining antigens with a photosensitizer and light for cytosolic antigen delivery. The goal of the current project was to test this immunization method with particle-based formulations. Liposomes were prepared from dipalmitoylphosphatidylcholine and cholesterol, and the antigen ovalbumin (OVA) or the photosensitizer tetraphenyl chlorine disulfonate (TPCS2a) was separately encapsulated. C57BL/6 mice were immunized intradermally with OVA liposomes or a combination of OVA and TPCS2a liposomes, and light was applied the next day for activation of the photosensitizer resulting in cytosolic release of antigen from phagosomes. Immune responses were tested both after a prime only regime and after a prime-boost scheme with a repeat immunization 2 weeks post priming. Antigen-specific CD8(+) T-cell responses and antibody responses were analyzed ex vivo by flow cytometry and ELISA methods. The physicochemical stability of liposomes upon storage and light exposure was analyzed in vitro. Immunization with both TPCS2a- and OVA-containing liposomes greatly improved CD8(+) T-cell responses as compared to immunization without TPCS2a and as measured by proliferation in vivo and cytokine secretion ex vivo. In contrast, OVA-specific antibody responses (IgG1 and IgG2c) were reduced after immunization with TPCS2a-containing liposomes. The liposomal formulation protected the photosensitizer from light-induced inactivation during storage. In conclusion, the photosensitizer TPCS2a was successfully formulated in liposomes and enabled a shift from MHC class II to MHC class I antigen processing and presentation for stimulation of strong CD8(+) T-cell responses. Therefore, photosensitive particulate vaccines may have the potential to add to current vaccine practice a new method of vaccination that, as opposed to current vaccines, can stimulate strong CD8(+) T-cell responses.
authors.affiliation: Department of Dermatology, University of Zurich , Gloriastrasse 31, 8091 Zurich, Switzerland.
authors.forename: Ásdís
authors.initials: Á
authors.lastname: Hjálmsdóttir
authors.affiliation: Institute of Pharmaceutical Sciences, ETH Zurich , Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland.
authors.forename: Céline
authors.initials: C
authors.lastname: Bühler
authors.affiliation: Institute of Pharmaceutical Sciences, ETH Zurich , Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland.
authors.forename: Vera
authors.initials: V
authors.lastname: Vonwil
authors.affiliation: Institute of Pharmaceutical Sciences, ETH Zurich , Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Roveri
authors.affiliation: Department of Dermatology, University of Zurich , Gloriastrasse 31, 8091 Zurich, Switzerland.|Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital , Montebello, 0310 Oslo, Norway.
authors.forename: Monika
authors.initials: M
authors.lastname: Håkerud
authors.affiliation: Department of Dermatology, University of Zurich , Gloriastrasse 31, 8091 Zurich, Switzerland.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wäckerle-Men
authors.affiliation: Institute of Pharmaceutical Sciences, ETH Zurich , Vladimir-Prelog-Weg 1-5/10, 8093 Zurich, Switzerland.
authors.forename: Bruno
authors.initials: B
authors.lastname: Gander
authors.affiliation: Department of Dermatology, University of Zurich , Gloriastrasse 31, 8091 Zurich, Switzerland.
authors.forename: Pål
authors.initials: P
authors.lastname: Johansen
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D000938:Antigen-Presenting Cells / Q000276:immunology; D003600:Cytosol / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D015395:Histocompatibility Antigens Class I; D007114:Immunization; D007271:Injections, Intradermal; D008081:Liposomes / Q000008:administration & dosage* / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D010047:Ovalbumin / Q000008:administration & dosage / Q000276:immunology; D010588:Phagosomes / Q000187:drug effects / Q000276:immunology* / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000008:administration & dosage; D011166:Porphyrins / Q000008:administration & dosage*; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism / Q000528:radiation effects; D014612:Vaccines / Q000008:administration & dosage*
chemical_list: D015395:Histocompatibility Antigens Class I; D008081:Liposomes; D017319:Photosensitizing Agents; D011166:Porphyrins; D014612:Vaccines; C559366:meso-tetraphenyl chlorin disulphonate; D010047:Ovalbumin
keywords: antigen delivery; cytosol targeting; liposomes; photochemical internalization (PCI)