Identification of Functional HLA-A*01 :01-Restricted EBV-LMP2-Specific T-cell Receptors

BACKGROUND

Adoptive transfer of genetically engineered T cells expressing antigen-specific T-cell receptors (TCRs), is an appealing therapeutic approach for Epstein-Barr virus (EBV)-associated malignancies of latency type II/III that express EBV-antigens (LMP1/2). Patients who are HLA-A*01:01pos could benefit from such products, since no T cells recognizing any EBV-derived peptide in this common HLA allele have been found thus far.

METHODS

HLA-A*01:01-restricted EBV-(LMP2)-specific T-cells were isolated using peptide-MHC-tetramers. Functionality was assessed by production of IFNγ and cytotoxicity when stimulated with EBV-LMP2-expressing cell-lines. Functionality of primary T cells transduced with HLA-A*01:01-restricted EBV-LMP2-specific TCRs was optimized by knocking out the endogenous TCR of primary T cells (ΔTCR) using CRISPR-Cas9 technology.

RESULTS

EBV-LMP2-specific T cells were successfully isolated and their TCRs were characterized. TCR gene-transfer in primary T cells resulted in specific peptide-MHC-tetramer binding and reactivity against EBV-LMP2-expressing cell-lines. The mean-fluorescence intensity of peptide-MHC-tetramer binding was increased 1.5-2 fold when the endogenous TCR of CD8pos T cells was knocked out. CD8pos/ΔTCR T cells modified to express EBV-LMP2-specific TCRs showed IFNγ secretion and cytotoxicity towards EBV-LMP2-expressing malignant cell-lines.

DISCUSSION

We isolated the first functional HLA-A*01:01-restricted EBV-LMP2-specific T-cell populations and TCRs, which can potentially be used in future TCR gene-therapy to treat EBV-associated latency type II/III malignancies.

Efficient and Non-genotoxic RNA-Based Engineering of Human T Cells Using Tumor-Specific T Cell Receptors With Minimal TCR Mispairing

Genetic engineering of T cells with tumor specific T-cell receptors (TCR) is a promising strategy to redirect their specificity against cancer cells in adoptive T cell therapy protocols. Most studies are exploiting integrating retro- or lentiviral vectors to permanently introduce the therapeutic TCR, which can pose serious safety issues when treatment-related toxicities would occur. Therefore, we developed a versatile, non-genotoxic transfection method for human unstimulated CD8⁺ T cells. We describe an optimized double sequential electroporation platform whereby Dicer-substrate small interfering RNAs (DsiRNA) are first introduced to suppress endogenous TCR α and β expression, followed by electroporation with DsiRNA-resistant tumor-specific TCR mRNA. We demonstrate that double sequential electroporation of human primary unstimulated T cells with DsiRNA and TCR mRNA leads to unprecedented levels of transgene TCR expression due to a strongly reduced degree of TCR mispairing. Importantly, superior transgenic TCR expression boosts epitope-specific CD8⁺ T cell activation and killing activity. Altogether, DsiRNA and TCR mRNA double sequential electroporation is a rapid, non-integrating and highly efficient approach with an enhanced biosafety profile to engineer T cells with antigen-specific TCRs for use in early phase clinical trials.

How (specific) would like your T-cells today? Generating T-cell therapeutic function through TCR-gene transfer

T-cells are central players in the immune response against both pathogens and cancer. Their specificity is solely dictated by the T-cell receptor (TCR) they clonally express. As such, the genetic modification of T lymphocytes using pathogen- or cancer-specific TCRs represents an appealing strategy to generate a desired immune response from peripheral blood lymphocytes. Moreover, notable objective clinical responses were observed in terminally ill cancer patients treated with TCR-gene modified cells in several clinical trials conducted recently. Nevertheless, several key aspects of this approach are the object of intensive research aimed at improving the reliability and efficacy of this strategy. Herein, we will survey recent studies in the field of TCR-gene transfer dealing with the improvement of this approach and its application for the treatment of malignant, autoimmune, and infectious diseases.