Immune Responses to the HLA-A*0201-Restricted Epitopes of Tyrosinase and Glycoprotein 100 Enable Control of Melanoma Outgrowth in HLA-A*0201-Transgenic Mice

Abstract

Many of the Ags recognized by human melanoma-reactive CTL are derived from proteins that are also expressed in melanocytes. The possibility of self-tolerance to these epitopes has led to questions about their utility for antitumor immunotherapy. To investigate the issue, we established a preclinical model based on transgenic mice expressing a recombinant HLA-A*0201 molecule and B16 melanoma transfected to express this molecule. HLA-A*0201-restricted epitopes from the melanocyte differentiation proteins (MDP) tyrosinase and gp100 are expressed in both tumor cells and melanocytes, and the former is associated with self-tolerance. However, adoptive transfer of tyrosinase or gp100-reactive CTL developed from tolerant mice delayed tumor outgrowth, as did immunization with MDP peptide-pulsed dendritic cells. Protection was enhanced by the use of peptide ligands containing conservative substitutions that were cross-reactive with the original Ags. These data establish that CTL populations reactive against MDP-derived self-Ags can be activated to mount effective antitumor immunity and strongly support their continued development for tumor immunotherapy in humans.

Incomplete Differentiation of Antigen-Specific CD8 T Cells in Tumor-Draining Lymph Nodes

“…In contrast, others have isolated activated Ag-specific CD8 T cells from B16 tumors (28,29). Similarly, we have shown previously that B16 is partially controlled by tyrosinase-specific CD8 T cells in mice lacking tyrosinase and in tyrosinase-expressing mice immunized against this Ag (30). Importantly, however, these robust responses were not sufficient to eliminate the tumor, and it eventually killed the animal.…”

“…OT-I RAG1 Ϫ/Ϫ mice and ␤ 2 -microglobulin (␤ 2 m) Ϫ/Ϫ mice were purchased from Taconic Farms. Tyrosinase Ϫ (albino) mice on the C57BL/6 background expressing a chimeric MHC class I molecule composed of the ␣1 and ␣2 domains of HLA-A*0201 and the ␣3 domain of H2-D d (AAD) have been described previously (30). FH TCR transgenic mice on a C57BL/6 background express a TCR specific for amino acids 369 -377 of tyrosinase (Tyr 369 ) in the context of AAD.…”

“…To study the presentation of B16 melanoma-derived Ag to CD8 T cells in vivo, we took advantage of two distinct models: B16-cOVA, in which B16-F1 melanoma was transfected with the cytoplasmic version of chicken OVA, allowing the OVA 257 epitope to serve as a model tumor Ag for recognition by OT-I TCR transgenic cells; and B16-AAD, in which the endogenous Tyr 369 epitope from the melanocyte differentiation protein tyrosinase is presented on B16-F1 melanoma cells transfected with the rAAD class I MHC molecule (30). In the latter case, we have generated transgenic mice (designated as FH mice) using a TCR specific for this epitope isolated from AAD ϩ albino mice.…”

“…B16-F1 transfected to express AAD (B16-AAD) has been described previously (30). B16-F1 expressing cytoplasmic chicken OVA (cOVA) (B16-cOVA) was produced using an expression vector provided by A. Lew (Walter & Eliza Hall Institute of Medical Research, Melbourne, Australia).…”

Dendritic Cell Immunization Route Determines Integrin Expression and Lymphoid and Nonlymphoid Tissue Distribution of CD8 T Cells

“…A ppropriately activated dendritic cells (DC) 4 are potent APC, and exogenously administered Ag-pulsed DC induce specific CD8 ϩ T cell responses against viral and tumor Ags (1)(2)(3)(4). However, the cellular nature and migration properties of exogenous DC limit their distribution in lymphoid compartments in an injection route-dependent manner (3,(5)(6)(7)(8)(9), leading to regionally constrained immune responses (3,5).…”