Molecular immunology lessons from therapeutic T-cell receptor gene transfer

Abstract

The T-cell receptor (TCR) is critical for T-cell lineage selection, antigen specificity, effector function and survival. Recently, TCR gene transfer has been developed as a reliable method to generate ex vivo large numbers of T cells of a given antigen-specificity and functional avidity. Such approaches have major applications for the adoptive cellular therapy of viral infectious diseases, virus-associated malignancies and cancer. TCR gene transfer utilizes retroviral or lentiviral constructs containing the gene sequences of the TCR-alpha and TCR-beta chains, which have been cloned from a clonal T-cell population of the desired antigen specificity. The TCR-encoding vector is then used to infect (transduce) primary T cells in vitro. To generate a transduced T cell with the desired functional specificity, the introduced TCR-alpha and TCR-beta chains must form a heterodimer and associate with the CD3 complex in order to be stably expressed at the T-cell surface. In order to optimize the function of TCR-transduced T cells, researchers in the field of TCR gene transfer have exploited many aspects of basic research in T-cell immunology relating to TCR structure, TCR-CD3 assembly, cell-surface TCR expression, TCR-peptide/major histocompatibility complex (MHC) affinity and TCR signalling. However, improving the introduction of exogenous TCRs into naturally occurring T cells has provided further insights into basic T-cell immunology. The aim of this review was to discuss the molecular immunology lessons learnt through therapeutic TCR transfer.

Figure 1

Schematic representation of critical processes in T-cell receptor (TCR) gene transfer. MHC, major histocompatibility complex.

Figure 2

Schematic representation of the T-cell receptor (TCR)-transduced T cell.

Figure 3

Heterodimer formation, CD3 association and cell-surface expression of modified T-cell receptor (TCR) constructs in TCR-αβ⁻ Jurkat cells. (a) Schematic representation of Wilms' tumour antigen 1 (WT1)-specific human leucocyte antigen-A2 (HLA-A2)-restricted TCR constructs. SS, disulphide bond. (b) Cell-surface expression of the WT1 TCR variants in CD3⁺ TCR-αβ⁻ Jurkat cells is shown. Mock and TCR-transduced Jurkat cells were stained with antibodies to the TCR and to the CD3 before fluorescence-activated cell sorter (FACS) analysis. CD3 association and cell-surface TCR expression was observed with the wild-type, Cysteine-1 and Hybrid TCR constructs. Biochemical analysis of Jurkat cells transduced with the Cysteine-2 TCR construct demonstrated no association of the Cysteine-2 β chain with either the Cysteine-2 α chain or CD3, resulting in no cell-surface CD3 expression or T-cell functional activity (the Cysteine-2 variant was identical to variant 1, except that the cysteine residues responsible for the formation of the natural disulphide bond between the TCR-α and TCR-β chains were removed).