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 OVA323–339 TCR) or OT1 (>90% CD8+ OVA257–264 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-2KbOva257–264 CD8+ T cells into CD44highCD62Llow 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.

Tumor cell lysate-pulsed dendritic cells induce a T cell response against colon cancer in vitro and in vivo

“…However, vaccinating against a single antigen has disadvantages, as it is unknown which of the identified antigens have the potential to induce an effective antitumor immune response [22]. Tumor lysates contain multiple known as well as unknown antigens that can be presented to T cells by MHC class I and class II pathways [23]. Therefore, lysateloaded DCs are more likely to induce a polyclonal expansion of T cells.…”

Identification and functional studies of HLA-A0201 restricted CTL epitopes in the X protein of hepatitis B virus

“…Such errors include a proteasome degradation by mistake, failure to be transported by TAP, and a small number of specific T cell receptors to identify them (Rivett and Hearn, 2004;Gurnani et al, 2004). Therefore, even though the HBx1, HBx3, and HBx4 epitopes showed ideal T2 cells binding or T cell stimulation, the lower immunity responses they induced in our experiments reveal that they are not CTL epitopes with the appropriate immunogenicity.…”

Murine polyomavirus-like particles induce maturation of bone marrow-derived dendritic cells and proliferation of T cells

“…VP1-OVA 252-270 and VP1-OVA 320-343 ). The fact that the complete OVA protein failed to stimulate OT1 and only marginally OT2 cells could be attributed to the low antigen processing efficiency of soluble OVA by APCs in vitro and in vivo [12,21]. Interestingly, we found that OT1 and OT2 cells stimulated with high amounts of PLP also showed a low level of proliferation.…”