title: Phosphatidylserine receptor-mediated recognition of archaeosome adjuvant promotes endocytosis and MHC class I cross-presentation of the entrapped antigen by phagosome-to-cytosol transport and classical processing.
abstract: Archaeal isopranoid glycerolipid vesicles (archaeosomes) serve as strong adjuvants for cell-mediated responses to entrapped Ag. We analyzed the processing pathway of OVA entrapped in archaeosomes composed of Methanobrevibacter smithii lipids, high in archaetidylserine (OVA-archaeosomes). In vitro, OVA-archaeosomes stimulated spleen cells from OVA-TCR-transgenic mice, D011.10 (CD4(+) cells expressing OVA(323-339) TCR) or OT1 (>90% CD8(+) OVA(257-264) cells), indicating both MHC class I and II presentations. In vivo, when naive (Thy1.2(+)) CFSE-labeled OT1 cells were transferred into OVA-archaeosome-immunized Thy 1.1(+) recipient mice, there was profound accumulation and cycling of donor-specific cells, and differentiation of H-2K(b)Ova(257-264) CD8(+) T cells into CD44(high)CD62L(low) effectors. Both macrophages and dendritic cells (DCs) efficiently cross-presented OVA-archaeosomes on MHC class I. Blocking phagocytosis by phosphatidylserine-specific receptor agonists strongly inhibited MHC class I presentation of OVA-archaeosomes, whereas blocking mannose receptors or FcRs lacked effect, indicating specific recognition of the archaetidylserine head group of M. smithii lipids by APCs. In addition, inhibitors of endosomal acidification blocked MHC class I processing of OVA-archaeosomes, whereas endosomal protease inhibitors lacked effect, suggesting acidification-dependent phagosome-to-cytosol diversion. Proteasomal inhibitors blocked OVA-archaeosome MHC class I presentation, confirming cytosolic processing. Both in vitro and in vivo, OVA-archaeosome MHC class I presentation required TAP. Ag-free archaeosomes also activated DC costimulation and cytokine production, without overt inflammation. Phosphatidylserine-specific receptor-mediated endocytosis is a mechanism of apoptotic cell clearance and DCs cross-present Ags sampled from apoptotic cells. Our results reveal the novel ability of archaeosomes to exploit this mechanism for cytosolic MHC class I Ag processing, and provide an effective particulate vaccination strategy.
authors.affiliation: Institute for Biological Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario, Canada K1A 0R6.
authors.forename: Komal
authors.initials: K
authors.lastname: Gurnani
authors.forename: Jessica
authors.initials: J
authors.lastname: Kennedy
authors.forename: Subash
authors.initials: S
authors.lastname: Sad
authors.forename: G Dennis
authors.initials: GD
authors.lastname: Sprott
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Krishnan
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D017951:Antigen Presentation; D001105:Archaea / Q000276:immunology*; D003546:Cysteine Endopeptidases / Q000502:physiology; D003600:Cytosol / Q000378:metabolism*; D003713:Dendritic Cells / Q000502:physiology; D004705:Endocytosis / Q000187:drug effects*; D011992:Endosomes / Q000378:metabolism; D005260:Female; D006017:Glycolipids / Q000494:pharmacology*; D015395:Histocompatibility Antigens Class I / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009097:Multienzyme Complexes / Q000502:physiology; D010047:Ovalbumin / Q000378:metabolism; D010588:Phagosomes / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011956:Receptors, Cell Surface / Q000502:physiology*; D014617:Vacuoles / Q000378:metabolism
chemical_list: D000276:Adjuvants, Immunologic; D006017:Glycolipids; D015395:Histocompatibility Antigens Class I; D009097:Multienzyme Complexes; C498708:Ptdsr protein, mouse; D011956:Receptors, Cell Surface; C408123:phosphatidylserine receptor; D010047:Ovalbumin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex