title: Microencapsulation of inorganic nanocrystals into PLGA microsphere vaccines enables their intracellular localization in dendritic cells by electron and fluorescence microscopy.
abstract: Biodegradable poly-(D,L-lactide-co-glycolide) microspheres (PLGA-MS) are approved as a drug delivery system in humans and represent a promising antigen delivery device for immunotherapy against cancer. Immune responses following PLGA-MS vaccination require cross-presentation of encapsulated antigen by professional antigen presenting cells (APCs). While the potential of PLGA-MS as vaccine formulations is well established, the intracellular pathway of cross-presentation following phagocytosis of PLGA-MS is still under debate. A part of the controversy stems from the difficulty in unambiguously identifying PLGA-MS within cells. Here we show a novel strategy for the efficient encapsulation of inorganic nanocrystals (NCs) into PLGA-MS as a tool to study their intracellular localization. We microencapsulated NCs as an electron dense marker to study the intracellular localization of PLGA-MS by transmission electron microscopy (TEM) and as fluorescent labels for confocal laser scanning microscopy. Using this method, we found PLGA-MS to be rapidly taken up by dendritic cells and macrophages. Co-localization with the lysosomal marker LAMP1 showed a lysosomal storage of PLGA-MS for over two days after uptake, long after the initiation of cross-presentation had occurred. Our data argue against an escape of PLGA-MS from the endosome as has previously been suggested as a mechanism to facilitate cross-presentation of PLGA-MS encapsulated antigen.
authors.affiliation: Division of Immunology, Department of Biology, Constance University, 78457 Konstanz, Germany.
authors.forename: Christopher
authors.initials: C
authors.lastname: Schliehe
authors.forename: Constanze
authors.initials: C
authors.lastname: Schliehe
authors.forename: Marc
authors.initials: M
authors.lastname: Thiry
authors.forename: Ulrich I
authors.initials: UI
authors.lastname: Tromsdorf
authors.forename: Joachim
authors.initials: J
authors.lastname: Hentschel
authors.forename: Horst
authors.initials: H
authors.lastname: Weller
authors.forename: Marcus
authors.initials: M
authors.lastname: Groettrup
mesh_terms: D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D045142:Cross-Priming / Q000276:immunology; D003713:Dendritic Cells / Q000378:metabolism* / Q000648:ultrastructure; D004337:Drug Carriers / Q000737:chemistry*; D004339:Drug Compounding; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D019344:Lactic Acid / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008863:Microspheres; D053758:Nanoparticles / Q000737:chemistry*; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D045663:Quantum Dots; D013440:Sulfides / Q000737:chemistry*; D014612:Vaccines / Q000008:administration & dosage* / Q000493:pharmacokinetics
chemical_list: D004337:Drug Carriers; D013440:Sulfides; D014612:Vaccines; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; C018391:lead sulfide; D011100:Polyglycolic Acid; D007854:Lead; D019344:Lactic Acid