Mannose Receptor Targeting of Tumor Antigen pmel17 to Human Dendritic Cells Directs Anti-Melanoma T Cell Responses via Multiple HLA Molecules

Abstract

Targeting recycling endocytic receptors with specific Abs provides a means for introducing a variety of tumor-associated Ags into human dendritic cells (DCs), culminating in their efficient presentation to T cells. We have generated a human mAb (B11) against the mannose receptor that is rapidly internalized by DCs through receptor-mediated endocytosis. By genetically linking the melanoma Ag, pmel17, to Ab B11, we obtained the fully human fusion protein, B11-pmel17. Treatment of DCs with B11-pmel17 resulted in the presentation of pmel17 in the context of HLA class I and class II molecules. Thus, potent pmel17-specific T cells were cytotoxic toward gp100+ HLA-matched melanoma targets, but not HLA-mismatched melanoma or gp100− nonmelanoma tumor lines. Importantly, competitive inhibition of lysis of an otherwise susceptible melanoma cell line by cold targets pulsed with known gp100 CD8 T cell epitopes as well as a dose-dependent proliferative response to Th epitopes demonstrates that DCs can process targeted Ag for activation of cytotoxic as well as helper arms of the immune response. Thus, the specific targeting of soluble exogenous tumor Ag to the DC mannose receptor directly contributes to the generation of multiple HLA-restricted Ag-specific T cell responses.

Antibody-targeted vaccines

“…Studies by our laboratory have demonstrated that targeting of tumor antigens to the MR on monocytederived DCs using a human MR-specific mAb can efficiently sensitize antigen-specific T cells which display MHC class I-and class II-restricted activity (He et al, 2004;Ramakrishna et al, 2004). Importantly, the MRtargeted vaccines elicited CTL responses to multiple epitopes, which resulted in specific lysis of histocompatibility leukocyte antigen-matched tumor cells naturally expressing the antigen.…”

Effective induction of naive and recall T-cell responses by targeting antigen to human dendritic cells via a humanized anti–DC-SIGN antibody

“…Potential candidate receptors highly expressed by DCs include Fc receptors [3][4][5] and members of the C-type lectin family. 6,7 Whereas Fc receptors are expressed by many different cell types, the expression of some members of the C-type lectin family are more DC restricted. 8 C-type lectins bind sugar residues in a calcium-dependent manner via a highly conserved carbohydrate recognition domain.…”

“…9 However, these ligands lack specificity for the MR, and may target multiple lectins with overlapping binding specificities, including soluble lectins and lectin receptors expressed by cells that are not specialized in antigen presentation. More specific receptor targeting can be obtained by the use of antibodies directed against specific C-type lectins, a strategy that has been successfully applied in MR 7,12 and DEC-205 6,10,11 targeting studies. Antibody-mediated targeting of antigen to the MR on human DCs results in antigen presentation and activation of naive T cells in vitro.…”

“…Antibody-mediated targeting of antigen to the MR on human DCs results in antigen presentation and activation of naive T cells in vitro. 7,12 Moreover, in vivo studies on antibody-mediated targeting of DEC-205 in mice demonstrate presentation of the antigen to naive CD4 ϩ and CD8 ϩ T cells. 6,10 DC-specific intercellular adhesion molecule 3 (ICAM-3)-grabbing nonintegrin (DC-SIGN) represents a member of the 14,15 Targeting constructs that are to be used in humans should consist of antibodies that do not elicit immune responses directed against the antibody itself.…”

Preferential Induction of CD4+ T Cell Responses through In Vivo Targeting of Antigen to Dendritic Cell-Associated C-Type Lectin-1

“…This can be done by using Abs specific for DC-expressed molecules as in vivo Ag carriers; using such an approach, a lowered requirement for Ag dose in stimulating immune responses in mice has been observed after targeting a variety of molecules, including MHC class II, CD11c, CD205, CD80/86, F4/80-like receptor (FIRE), CIRE, and the undefined Ag recognized by the mAb 33D1 (1)(2)(3)(4)(5)(6)(7)(8)(9). In addition, in vitro studies have shown that Abs specific for the mannose receptor or DC-SIGN can effectively deliver Ag to human DCs, indicating that this strategy will also be applicable to human vaccination (10,11). Although these reports have illustrated the general effectiveness of DC targeting as a strategy for vaccination, there is currently limited information on whether immune responses may be triggered differently through distinct targeting receptors.…”