title: Apolipoprotein B binding domains: evidence that they are cell-penetrating peptides that efficiently deliver antigenic peptide for cross-presentation of cytotoxic T cells.
abstract: Low-density lipoproteins (LDLs) are a good source of cholesterol, which is important in cellular homeostasis and production of steroids. Apolipoprotein B-100 (ApoB-100), the sole protein component of LDL, is known to bind to cell surface LDL receptor (LDLR) or cell surface-bound proteoglycans and to be internalized into cells. We found that APCs, consisting of macrophages and dendritic cells, upregulate LDLR on culture in vitro without obvious stimulation. In contrast, T cell populations only upregulate LDLR on activation. Thus, we strategized that tagging immunogens to ApoB-100 might be a useful means to target Ag to APCs. We generated fusion proteins consisting of receptor binding sites in ApoB-100, coupled to OVA peptide (ApoB-OVA), as Ag delivery vehicles and demonstrated that this novel delivery method successfully cross-presented OVA peptides in eliciting CTL responses. Surprisingly, internalization of ApoB-OVA peptide occurred via cell surface proteoglycans rather than LDLRs, consistent with evidence that structural elements of ApoB-100 indicate it to have cell-penetrating peptide properties. Finally, we used this strategy to assess therapeutic vaccination in a tumor setting. OVA-expressing EL-4 tumors grew progressively in mice immunized with ApoB-100 alone but regressed in mice immunized with ApoB-OVA fusion protein, coinciding with development of OVA-specific CTLs. Thus, to our knowledge, this is the first article to describe the cell-penetrating properties of a conserved human origin cell penetrating peptide that may be harnessed as a novel vaccination strategy as well as a therapeutics delivery device.
authors.affiliation: Division of Therapeutic Proteins, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Bethesda, MD 20892, USA. norihisa.sakamoto@fda.hhs.gov
authors.forename: Norihisa
authors.initials: N
authors.lastname: Sakamoto
authors.forename: Amy S
authors.initials: AS
authors.lastname: Rosenberg
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology*; D053299:Apolipoprotein B-100 / Q000276:immunology* / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D039521:CD11c Antigen / Q000276:immunology / Q000378:metabolism; D045744:Cell Line, Tumor; D057846:Cell-Penetrating Peptides / Q000276:immunology* / Q000378:metabolism; D045142:Cross-Priming / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009374:Neoplasms, Experimental / Q000235:genetics / Q000276:immunology / Q000473:pathology; D010047:Ovalbumin / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding; D011509:Proteoglycans / Q000276:immunology / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism
chemical_list: D000941:Antigens; D053299:Apolipoprotein B-100; D039521:CD11c Antigen; D057846:Cell-Penetrating Peptides; C110366:OVA-8; D010446:Peptide Fragments; D011509:Proteoglycans; D011973:Receptors, LDL; D011993:Recombinant Fusion Proteins; D010047:Ovalbumin