Improving anti-tumor immunity by engineering T cell receptors to prevent mispairing (VAC7P.1033)

Abstract

Abstract T cells transduced with the genes encoding the α and β chains of a tumor-specific T cell receptor (TCR) can mediate anti-tumor immunity in patients. Such TCR-transduced T cells co-express both the therapeutic and an endogenous TCR. As each receptor is an αβ heterodimer, the endogenous α chain can mispair with the therapeutic β chain and vice versa. Such mispairing - which is observed in transduced human T cells - reduces export of the therapeutic TCR and produces potentially self-reactive TCRs. The latter can precipitate graft-vs-host disease, a lethal complication reported in mice following TCR gene transfer. We have developed a general strategy for preventing TCR mispairing. Select constant domains are swapped between the α and β chains of a tumor-specific T cell receptor, creating a domain-swapped (ds)TCR. When correctly paired, these dsTCR chains retain all domains necessary to recruit CD3 proteins, to express on the T cell surface, and to mediate functional T cell responses upon engaging a target antigen. By contrast, mispaired TCRs containing one dsTCR chain and one wild-type TCR chain lack key domains necessary for CD3 recruitment, export, and signaling, and thus are unable to mediate deleterious autoimmunity. We validate the potential of this approach in cell-based assays, as well as in a mouse model of TCR gene transfer-induced graft-vs-host disease. Thus, this work will enable the design of safer, more effective TCR gene therapy candidates for cancer immunotherapy.