Figure 2.

Engrafting the scFv on TCR chains. To take advantage of the superior T cell activation machinery, several strategies were reported for engrafting the scFv as binding domain to the TCR chains. By CRISPR-Cas9 genome editing the endogenous TCR chains were deleted and by AAV6 vector transfer a HLA-independent T cell (HIT) receptor was expressed that harbors the antibody VH and the VL chains linked to the TCR Cβ and Cα domain, respectively, giving rise to TCR chains with antibody derived VL and VH binding domains. Synthetic T cell and antigen receptor (STAR) is also a TCR chain-based receptor with the VH and VL chains fused to the constant regions of the TCR while the physiological TCR is still expressed. By attaching a scFv to the extracellular N-termini of the CD3ϵ chain, a synthetic TCR fusion construct (TRuC) is obtained which is effectively integrated into the physiological TCR complex. In contrast to HIT receptors, which are constructed by using genome editing to replace the variable domains of the T cell receptor by the scFv chains, STAR receptors and TRuCs are transferred to T cells by viral transduction.