CD4⁺CD25⁻ T Cells Transduced to Express MHC Class I-Restricted Epitope-Specific TCR Synthesize Th1 Cytokines and Exhibit MHC Class I-Restricted Cytolytic Effector Function in a Human Melanoma Model

Abstract

Cytolytic T cell-centric active specific and adoptive immunotherapeutic approaches might benefit from the simultaneous engagement of CD4⁺ T cells. Considering the difficulties in simultaneously engagingCD4⁺ and CD8⁺ T cells in tumor immunotherapy, especially in an Ag-specific manner, redirecting CD4⁺ T cells to MHC class I-restricted epitopes through engineered expression of MHC class I-restricted epitope-specific TCRs in CD4⁺ T cells has emerged as a strategic consideration. Such TCR-engineered CD4⁺ T cells have been shown to be capable of synthesizing cytokines as well as lysing target cells. We have conducted a critical examination of functional characteristics of CD4⁺ T cells engineered to express the α- and β-chains of a high functional avidity TCR specific for the melanoma epitope, MART-1, as a prototypic human tumor Ag system. We found that unpolarized CD4⁺CD25⁻ T cells engineered to express the MART-1 TCR selectively synthesize Th1 cytokines and exhibit a potent Ag-specific lytic granule exocytosis-mediated cytolytic effector function of comparable efficacy to that of CD8⁺ CTL. Such TCR engineered CD4⁺ T cells, therefore, might be useful in clinical immunotherapy.