A TCR mimic monoclonal antibody reactive with the “public” phospho-neoantigen pIRS2/HLA-A*02:01 complex
Tao Dao, … , Richard J. O’Reilly, David A. Scheinberg
Tao Dao, … , Richard J. O’Reilly, David A. Scheinberg
Published March 8, 2022
Citation Information: JCI Insight. 2022;7(5):e151624. https://doi.org/10.1172/jci.insight.151624.
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Research Article Immunology Oncology

A TCR mimic monoclonal antibody reactive with the “public” phospho-neoantigen pIRS2/HLA-A*02:01 complex

Abstract

Phosphopeptides derived from dysregulated protein phosphorylation in cancer cells can be processed and presented by MHC class I and class II molecules and, therefore, represent an untapped class of tumor-specific antigens that could be used as widely expressed “public” cancer neoantigens (NeoAgs). We generated a TCR mimic (TCRm) mAb, 6B1, specific for a phosphopeptide derived from insulin receptor substrate 2 (pIRS2) presented by HLA-A*02:01. The pIRS2 epitope’s presentation by HLA-A*02:01 was confirmed by mass spectrometry. The TCRm 6B1 specifically bound to pIRS2/HLA-A2 complex on tumor cell lines that expressed pIRS2 in the context of HLA-A*02:01. Bispecific mAbs engaging CD3 of T cells were able to kill tumor cell lines in a pIRS2- and HLA-A*02:01–restricted manner. Structure modeling shows a prerequisite for an arginine or lysine at the first position to bind mAb. Therefore, 6B1 could recognize phosphopeptides derived from various phosphorylated proteins with similar amino acid compositions. This raised the possibility that a TCRm specific for the pIRS2/HLA-A2 complex could target a range of phosphopeptides presented by HLA-A*02:01 in various tumor cells. This is the first TCRm mAb to our knowledge targeting a phosphopeptide/MHC class I complex; the potential of this class of agents for clinical applications warrants further investigation.

Authors

Tao Dao, Sung Soo Mun, Zaki Molvi, Tatyana Korontsvit, Martin G. Klatt, Abdul G. Khan, Elisabeth K. Nyakatura, Mary Ann Pohl, Thomas E. White, Paul J. Balderes, Ivo C. Lorenz, Richard J. O’Reilly, David A. Scheinberg

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Figure 2

Specific recognition of tumor cells.

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Specific recognition of tumor cells. (A–F) Recognition of the naturally ...
(A–F) Recognition of the naturally presented pIRS2/A2 complex on the tumor cell surface by 6B1 in a pIRS2/HLA-A2–restricted manner was determined by flow cytometric analysis. Human leukemia cell lines BV173, SET2, ovarian cancer cell line SKOV-3 and Burkitt’s lymphoma cell line Jeko, and HLA-A2– T leukemia cell line Jurkat were stained with 6B1 conjugated to APC at 10 μg/mL, followed by flow cytometric analysis. T2 cells pulse with pIRS2 was used as a positive control. Unstained cells and isotype hIgG1 were used as negative controls. Data are representative of 3 experiments. (G–J) Similarly, normal human cardiomyocytes, cardiac fibroblasts and thymic fibroblasts (H–J) and AML cell line AML-14 (G) were stained with 6B1 or isotype control (3 μg/mL) and followed by goat anti–human IgG Fab2 conjugated to FITC. (K–M) HLA-A2 expression (K) was simultaneously measured by anti HLA-A2 mAb (clone BB7.2) conjugated to APC. (L and M) Whole blood from HLA-A2+ (L) or HLA-A2– (M) healthy donor was stained with the 6B1 or isotype control (3 µg/mL) and mAbs to CD15, CD33, and CD45RA; red blood cells were lysed; washed; and run on flow cytometry. The data represent staining from 5 separated experiments with multiple donors.