title: Spatial separation of the processing and MHC class I loading compartments for cross-presentation of the tumor-associated antigen HER2/neuby human dendritic cells.
abstract: Cross-presentation is the process by which professional antigen presenting cells (APCs) (B cells, dendritic cells (DCs) and macrophages) present endocytosed antigens (Ags) via MHC-I to CD8+T cells. This process is crucial for induction of adaptive immune responses against tumors and infected cells. The pathways and cellular compartments involved in cross-presentation are unresolved and controversial. Among the cells with cross-presenting capacity, DCs are the most efficient, which was proposed to depend on prevention of endosomal acidification to block degradation of the epitopes. Contrary to this view, we show in this report that some cargoes induce strong endosomal acidification following uptake by human DCs, while others not. Moreover, processing of the tumor-associated antigen HER2/neudelivered in nanoparticles (NP) for cross-presentation of the epitope HER2/neu369-377on HLA-A2 depended on endosomal acidification and cathepsin activity as well as proteasomes, and newly synthesized HLA class I. However, the HLA-A*0201/HER2/neu369-377complexes were not found in the endoplasmic reticulum (ER) nor in endolysosomes but in hitherto not described vesicles. The data thus indicate spatial separation of antigen processing and loading of MHC-I for cross-presentation: antigen processing occurs in the uptake compartment and the cytosol whereas MHC-I loading with peptide takes place in a distinct subcellular compartment. The findings further elucidate the cellular pathways involved in the cross-presentation of a full-length, clinically relevant tumor-associated antigen by human DCs, and the impact of the vaccine formulation on antigen processing and CD8+T cell induction.
authors.affiliation: Department of Dermatology; Venerology and Allergology; Charité - Universitätsmedizin Berlin ; Berlin, Germany.
authors.forename: Renato B
authors.initials: RB
authors.lastname: Baleeiro
authors.affiliation: Helmholtz Institute for Pharmaceutical Research Saarland (HIPS); Helmholtz Centre for Infection Research; Saarland University ; Saarbrücken, Germany.
authors.forename: René
authors.initials: R
authors.lastname: Rietscher
authors.affiliation: Department of Pharmaceutics and Biopharmaceutics; Kiel University ; Kiel, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Diedrich
authors.affiliation: Laboratory of Organic and Macromolecular Chemistry (IOMC); Friedrich Schiller University Jena; Jena, Germany; Jena Center for Soft Matter (JCSM); Friedrich Schiller University Jena; Jena, Germany.
authors.forename: Justyna A
authors.initials: JA
authors.lastname: Czaplewska
authors.affiliation: Helmholtz Institute for Pharmaceutical Research Saarland (HIPS); Helmholtz Centre for Infection Research; Saarland University; Saarbrücken, Germany; Biopharmaceutics and Pharmaceutical Technology; Saarland University; Saarbrücken, Germany.
authors.forename: Claus-Michael
authors.initials: CM
authors.lastname: Lehr
authors.affiliation: Department of Pharmaceutics and Biopharmaceutics; Kiel University ; Kiel, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Scherließ
authors.affiliation: Open Innovation Management; Merck KGaA ; Darmstadt, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Hanefeld
authors.affiliation: Laboratory of Organic and Macromolecular Chemistry (IOMC); Friedrich Schiller University Jena; Jena, Germany; Jena Center for Soft Matter (JCSM); Friedrich Schiller University Jena; Jena, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Gottschaldt
authors.affiliation: Department of Dermatology; Venerology and Allergology; Charité - Universitätsmedizin Berlin ; Berlin, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Walden
keywords: HER2/neu; cancer; cross-presentation; dendritic cells; nanoparticles; tumor-associated antigens; vaccine 