T Cells Expressing a TCR-Like Antibody Selected Against the Heteroclitic Variant of a Shared MAGE-A Epitope Do Not Recognise the Cognate Epitope.

Mesha Saeed,David K Cole,Mandy Van Brakel,Timo L M Ten Hagen,Reno Debets,Erik Schooten

doi:10.3390/cancers12051255

Mesha Saeed, David K Cole + Show 4 more

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https://doi.org/10.3390/cancers12051255

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Abstract

Antibodies-recognising peptides bound to the major histocompatibility complex (pMHC) represent potentially valuable and promising targets for chimeric antigen receptor (CAR) T cells to treat patients with cancer. Here, a human phage-Fab library has been selected using HLA-A2 complexed with a heteroclitic peptide variant from an epitope shared among multiple melanoma-associated antigens (MAGEs). DNA restriction analyses and phage ELISAs confirmed selection of unique antibody clones that specifically bind to HLA-A2 complexes or HLA-A2-positive target cells loaded with native or heteroclitic peptide. Antibodies selected against heteroclitic peptide, in contrast to native peptide, demonstrated significantly lower to even negligible binding towards native peptide or tumour cells that naturally expressed peptides. The binding to native peptide was not rescued by phage panning with antigen-positive tumour cells. Importantly, when antibodies directed against heteroclitic peptides were engineered into CARs and expressed by T cells, binding to native peptides and tumour cells was minimal to absent. In short, TCR-like antibodies, when isolated from a human Fab phage library using heteroclitic peptide, fail to recognise its native peptide. We therefore argue that peptide modifications to improve antibody selections should be performed with caution as resulting antibodies, either used directly or as CARs, may lose activity towards endogenously presented tumour epitopes.

Highlights

T cells are key players in the adaptive immune response, in cancer, and are equipped with T-cell receptors (TCRs) that recognise short peptide complexes presented by MHC molecules
We identified HLA-A2-positive tumour cells from various histological origins that express melanoma-associated antigens (MAGEs)-A3, A6, A10 and/or A12 to establish a panel of tumour cell lines with endogenous
We identified HLA-A2-positive tumour cells from various histological origins that express MAGE-A3, A6, A10 and/or A12 to establish a panel of tumour cell lines with endogenous expression of mMA (Figure 3A)

Summary

Introduction

T cells are key players in the adaptive immune response, in cancer, and are equipped with T-cell receptors (TCRs) that recognise short peptide complexes presented by MHC molecules. T lymphocytes (CTLs) play a critical role in the eradication of tumour cells and recognise peptides in the context of MHC class I molecules (MHCI). Adoptive T-cell therapy (AT), a well-tested and promising approach to treat cancer, relies on the infusion of autologous tumour-specific T cells. Besides the use of non-modified T cells, such as tumour-infiltrating lymphocytes (TILs) or peripheral T-cell clones, there is a clear shift toward the use of T cells that are gene-engineered to express chimeric antigen. These CAR-engineered T cells recognise a chosen tumour antigen, and are redirected to selectively destroy cells expressing this antigen.

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