No Advantage of Cell-Penetrating Peptides over Receptor-Specific Antibodies in Targeting Antigen to Human Dendritic Cells for Cross-Presentation

Abstract

Induction of CTL responses by dendritic cell (DC)-based vaccines requires efficient DC-loading strategies for class I Ags. Coupling Ags to cell-penetrating peptides (CPPs) or receptor-specific Abs improves Ag loading of DCs. In contrast to CPPs, receptor-specific Abs deliver conjugated Ags to DCs with high specificity, which is advantageous for in vivo strategies. It has, however, been speculated that CPPs facilitate uptake and endosomal escape of conjugated Ags, which would potently enhance cross-presentation. In this study, we directly compare the in vitro targeting efficiency of a humanized D1 Ab directed against the human DC surface receptor DC-SIGN hD1 to that of three CPPs. The three CPPs colocalized within endosomes when targeted to human monocyte-derived DCs simultaneously, whereas hD1 was present in a different set of endosomes. However, within 75 min after uptake CPPs and hD1 colocalized extensively within the lysosomal compartment. Ab-mediated targeting of class I-restricted peptides to DC-SIGN enhanced cross-presentation of the peptides, while only one of the CPPs enhanced peptide presentation. This CPP and hD1 enhanced cross-presentation with equal efficiencies. Thus, we found no evidence of CPP specifically favoring the delivery of conjugated Ag to the DC class I presentation pathway. Given the specificity with which Abs recognize their targets, this favors the use of DC receptor-specific Abs for in vivo vaccination strategies.

Targeting DC-SIGN via its neck region leads to prolonged antigen residence in early endosomes, delayed lysosomal degradation, and cross-presentation

“…Notwithstanding, it has been shown before by our group as well as others that antigens targeted to the CRD of DC-SIGN can also be cross-presented, despite the fact that they are routed to lysosomal compartments. 8,10 Possibly, targeting the CRD-domain routes part of the antigen toward a recently defined antigen storage compartment distinct from early endosomal and MHC class II loading compartments. This storage compartment stains positive for the lysosomal marker LAMP1, negative for MHC classes I and II, and (green) at 4°C, washed, and shifted at 37°C for the indicated time points.…”

“…5,6 By analogy, vaccination strategies targeting antigens to the CRD of DC-SIGN resulted in antigen presentation via MHC classes I and II. [7][8][9][10] In vivo, targeted delivery of antigens to the CRD of DC-SIGN in Rag2 Ϫ/Ϫ ␥C Ϫ/Ϫ mice reconstituted with human immune cells also induced antigen-specific T-cell responses. 11 Thus far, both antibodies and sugar ligands have been exploited to target antigens to the CRD of DC-SIGN.…”

An Anti-Nucleic Acid Antibody Delivers Antigen to the Cross-Presentation Pathway in Dendritic Cells and Potentiates Therapeutic Antitumor Effects

“…Draining lymph node CD11c + DCs from mice cross presented OVA 48 h after injection of 3D8-OVA [250][251][252][253][254][255][256][257][258][259][260][261][262][263][264] . Ag targeting to the cross-presentation pathway in DCs has been studied using Ags coupled to carriers such as cell-penetrating peptides (CPPs) (27)(28)(29), endocytosed Hsps (9,30), and Abs against DC-specific endocytic receptors, including DC-SIGN and DEC205 (26). In particular, Ag targeting to the cross-presentation pathway in both murine and human DCs has been extensively studied by Steinman's group, using an anti-DEC205 Ab (31,32).…”

Novel Cell-Penetrating Peptide-Based Vaccine Induces Robust CD4+ and CD8+ T Cell–Mediated Antitumor Immunity

“…Alternatively, they are also called protein transduction domain (PTD) reflecting their origin as occurring in natural proteins. Recently, a study comparing three different CPPs (including TAT and polyR) with the antibody against the DC receptor SIGN demonstrated that polyR is more potent than TAT to deliver protein to DCs and that similar antigen presentation was achieved by DCs loaded with either polyR or the anti-DC-SIGN antibody, at least in vitro (14). Therefore, the interest remains very high to identify a CPP allowing efficient multi-epitopic antigen delivery for cancer immunotherapies.…”