Artificial Antigen-Presenting Cells Transduced with Telomerase Efficiently Expand Epitope-Specific, Human Leukocyte Antigen–Restricted Cytotoxic T Cells

Abstract

Human telomerase reverse transcriptase (hTERT) is overexpressed in most human tumors, making it a potential target for cancer immunotherapy. hTERT-derived CTL epitopes have been identified previously, including p865 (RLVDDFLLV) and p540 (ILAKFLHWL), which are restricted by the human leukocyte antigen (HLA) class I A*0201 allele. However, it remains a major challenge to efficiently and consistently expand hTERT-specific CTLs from donor peripheral blood T lymphocytes. To bypass the need for generating conventional antigen-presenting cells (APCs) on an autologous basis, we investigated the potential ability of fibroblast-derived artificial APCs (AAPCs) to activate and expand HLA-A*0201-restricted CTLs. We show here that AAPCs stably expressing HLA-A*0201, human B 2 -microglobulin, B7.1, intercellular adhesion molecule-1, and LFA-3, together with either p540 and p865 minigenes or the full-length hTERT, effectively stimulate tumoricidal, hTERT-specific CTLs. hTERT-expressing AAPCs stimulated both p540 and p865 CTLs as shown by peptide-specific cytolysis and tetramer staining, indicating that hTERT is processed by the AAPCs and that the two peptides are presented as codominant epitopes. The level of cytotoxic activity against a panel of tumors comprising hematologic and epithelial malignancies varied, correlating overall with the level of HLA-A2 and hTERT expression by the target cell. Starting from 100 mL blood, f100 million hTERTspecific CTLs could be generated over the course of five sequential stimulations, representing an expansion of f1 Â 10 5 . Our data show that AAPCs process hTERT antigen and efficiently stimulate hTERT-specific CTLs from human peripheral blood T lymphocytes and suggest that sufficient expansion could be achieved to be clinically useful for adoptive cell therapy. (Cancer Res 2005; 65(12): 5417-27)

Establishment and Characterization of a Cell Based Artificial Antigen-Presenting Cell for Expansion and Activation of CD8+ T Cells Ex Vivo

“…However, the self-limitation of insect cells at 37 o C (the viable temperature for D. melanogaster cells is 27 o C) could lead to massive release of D. melanogaster antigens and limit the duration of the contact between the T cell and the aAPC (16,17). Mouse fibroblasts yielded on average 30 × 10 6 specific CTLs, however much higher T-cell doses may be required in the clinic (18)(19)(20). The bead-based systems also have some drawbacks, including high cost of the beads, the labor-intensive process of removing the beads from the culture before infusion, and the inability of these beads to expand CD8 + T cells (21)(22)(23)(24).…”

The HLA A*0201–restricted hTERT540–548 peptide is not detected on tumor cells by a CTL clone or a high-affinity T-cell receptor

“…Tetramer-positive T cells specific for the hTERT 540 -548 peptide have been detected in the peripheral blood of cancer patients (44), and this putative epitope has become the main focus for T-cell therapies. Several groups have grown polyclonal T-cell lines which have been reported to kill HLA A2 + , telomerase + tumor cell lines and primary tumors (16,24,25). However, two other groups have reported that T-cell clones to this epitope do not kill tumor cells (26,27).…”

“…Three groups (16,24,25) reported that polyclonal CTL lines specific for this pMHC can lyse tumor cells exhibiting telomerase activity. However, two subsequent studies using monoclonal CTL populations could not reproduce these observations (26,27).…”

The only proposed T-cell epitope derived from the TEL-AML1 translocation is not naturally processed

“…Murine NIH/3T3 fibroblasts were used for generation of HHD-restricted APCs because they were shown to be capable of processing and presenting the same viral and tumor HLA-A*0201 restricted epitopes, which were immunogenic in humans. 28,29 Both the TEL-AML1 fusion region and Melan-A/MART-1 were cloned into the retroviral vector pMP71 16 in identical fashion, as a single ORF with EGFP and Ub moiety ( Figure 4A), according to the Ub/protein/ reference (UPR) technique. 18 The tripartite fusion comprising the test antigen (TEL-AML1), or the control tumor antigen To show that the generated NIH-HHD cells can efficiently present peptide antigens to CD8 ϩ T cells, we loaded the cells with the nonamer peptides used for the immunization (TEL-AML1-9V or Melan-A/MART-1) and cocultured them with the pooled spleen and LN cells from the immunized mice.…”