Cooperation of human tumor-reactive CD4⁺ and CD8⁺ T cells after redirection of their specificity by a high-affinity p53A2.1-specific TCR

Efficient immune attack of malignant disease requires the concerted action of both CD8⁺ CTL and CD4⁺ Th cells. We used human leukocyte antigen (HLA)-A*0201 (A2.1) transgenic mice, in which the mouse CD8 molecule cannot efficiently interact with the α3 domain of A2.1, to generate a high-affinity, CD8-independent T cell receptor (TCR) specific for a commonly expressed, tumor-associated cytotoxic T lymphocyte (CTL) epitope derived from the human p53 tumor suppressor protein. Retroviral expression of this CD8-independent, p53-specific TCR into human T cells imparted the CD8 ⁺ T lymphocytes with broad tumor-specific CTL activity and turned CD4⁺ T cells into potent tumor-reactive, p53A2.1-specific Th cells. Both T cell subsets were cooperative and interacted synergistically with dendritic cell intermediates and tumor targets. The intentional redirection of both CD4⁺ Th cells and CD8⁺ CTL by the same high-affinity, CD8-independent, tumor-specific TCR could provide the basis for novel broad-spectrum cancer immunotherapeutics.