Ag‐bearing liposomes engrafted with peptides that interact with CD11c/CD18 induce potent Ag‐specific and antitumor immunity

Abstract

Dendritic cells (DCs) play key role in eliciting antigen (Ag)-specific immune responses, and crucial to this is the uptake of Ag via surface receptors including the heterodimeric integrin CD11c/CD18. Here we report that CD11c/CD18-interacting peptides can be used as targeting moieties to deliver liposomal Ag to antigen presenting cells (APCs) and elicit Ag-specific and antitumor immunity. Two peptides of sequence related to human ICAM-4 and previously reported to bind CD11c/CD18, and a 12-mer cyclic peptide previously identified by phage display to bind CD11c/CD18, were produced synthetically, and tested for their ability to target liposomal Ag. The three peptides were designed to contain a shorter spacer to reduce steric hindrance, and a His-tag to enable engraftment onto liposomes incorporated with chelator lipid. Our results show that the three peptides, denoted as p17, p18 and p30, promote strong binding of liposomes to CD11c 1 and CD11b 1 cells in vitro and in vivo. Vaccination of mice with Ag-bearing liposomes engrafted with the peptides, particularly p18 and p30, induced Agspecific T cell priming and antibody production. Importantly, the vaccination of C57BL/6 mice with syngeneic B16-OVA-derived plasma membrane vesicles (PMVs) engrafted with p18 and p30 peptide showed dramatic antitumor responses, inhibiting tumor growth/metastasis in both the lung and subcutaneous tumor models, with a high proportion of the mice apparently being ''cured'' of their tumors. The engraftment of p18 and p30 peptides onto liposomes and PMVs, thus provides an effective means to target Ags to DCs in vivo, for the development of effective cancer vaccines and immunotherapies.The use of antigen-pulsed dendritic cells (DCs) has shown promise for developing cell-based cancer vaccines and immunotherapies. 1 DCs play a key role in eliciting Ag-specific immune responses, and crucial to this is the uptake of antigen (Ag) via a number of DC surface receptors such as Fc-receptors, C-type lectins, Toll-like receptors (TLRs) and integrin receptor CD11c/CD18. [2][3][4][5][6] The unique ability of DCs to prime naïve T cells makes them ideal targets for Ag-delivery and vaccine development. 7 To better exploit this potential, techniques have been used to target protein-Ag to DCs in vivo, potentially circumventing the need to manipulate DCs ex vivo for cancer immunotherapy. 8,9 Typical strategies involve conjugation of Ag to mAbs, ScFv or Fab fragments specific for a DC surface marker or Ag-uptake receptor. 4,6,10,11 To facilitate the delivery of multiple Ags simultaneously, we previously attached recombinant co-stimulatory molecules and ScFv to Ag-containing delivery vehicles such as liposomes and membrane vesicles. 8,12 The vaccination of mice with such constructs can elicit potent immune responses and inhibit tumor growth in tumor models. 12 However, mAbs, ScFvs, and recombinant proteins for use as DC-targeted conjugates, or as targeting moieties for liposomes, can be time-consuming and expensive to produce for clinical applications.The use of...

VLPs and particle strategies for cancer vaccines

“…First attempts were made with Ig-G coated liposomes containing T-cell specific hen egg lysozyme, allowing a 1000-10,000-fold increase of antigen presentation by DCs compared with free antigen or non-targeted liposomes [173]. In a more and CD11b(+) cells in vitro and in vivo Inhibition of tumor growth and metastasis [204,178] g-PGA nanoparticles…”

“…CD11c/ CD18-interacting peptides were used as targeting moieties of antigen-loaded stealth liposomes and demonstrated to elicit dramatic antitumor responses in vivo, inhibiting tumor growth/ metastasis in the subcutaneous tumor model and the lung, respectively [178].…”

Combinatorial Peptide Libraries: Mining for Cell-Binding Peptides

“…One such peptide, the CGRWSGWPADLC peptide, was isolated against the dendritic-cell-specific marker CD11c/CD18 390 and was later used for vaccination. 391 A TNF-α-competing (TNF-α = tumor necrosis factor-α) peptide, CYTYQGKLC, was isolated by in vitro panning against the murine dendritic cell line JAWSII, using TNF-α to elute bound phage. 392 The peptide was shown to specifically deliver genes to dendritic cells (details later).…”

“…Faham and Altin used the previously isolated dendritic-cell-binding peptide CGRWSGWPADLC 390 to specifically target dendritic cells in mice in vivo. 391 The peptide was first attached to a liposome carrying OVA as a model antigen. Mice vaccinated with peptide–OVA–liposomes by intravenous injection produced OVA-specific antibodies unlike mice vaccinated with control OVA–liposomes.…”

Integrin CD11c/CD18 α-Chain Phosphorylation Is Functionally Important

“…Recently, it has been shown to have an important role in antigen uptake and presentation, generating CD4 and CD8 T cell-mediated responses and providing a useful approach for antitumor vaccine development (19). Targeting CD11c has proven successful using either anti-CD11c Fab fragments (19) or peptides against CD11c/CD18 derived from ICAM-4 and ICAM-1-extracellular CD11c/CD18 binding domains (20). CD11c/CD18 has also been shown to have a role in the transendothelial migration of macrophages to atherosclerotic plaques in hypercholesterolemic mice (13,21,22).…”