Mansilla-Soto et al. generated TRAC-HIT T (HIT) cells with TRAC KO and specificity for CD19 conferred to the TCR–CD3 complex by changing the peptide:MHC-binding portion of the TCR to match the VH/VL domains of CD19 CAR T cells. Cells expressing CD19 at levels too low to be lysed by CAR cells were lysed by HIT cells. HIT cells had more phosphorylated peptides and degranulated faster than CAR cells when incubated with cells with very low CD19 expression. HIT cells outperform CAR T cells in controlling low-antigen tumor cells in vivo. Prolonged tumor control by HIT CD19, BCMA, or CD70 cells was achieved by providing cell-intrinsic costimulatory ligands for CD28 and 4-1BB.
Contributed by Margot O’Toole
ABSTRACT: Chimeric antigen receptors (CARs) are receptors for antigen that direct potent immune responses. Tumor escape associated with low target antigen expression is emerging as one potential limitation of their efficacy. Here we edit the TRAC locus in human peripheral blood T cells to engage cell-surface targets through their T cell receptor-CD3 complex reconfigured to utilize the same immunoglobulin heavy and light chains as a matched CAR. We demonstrate that these HLA-independent T cell receptors (HIT receptors) consistently afford high antigen sensitivity and mediate tumor recognition beyond what CD28-based CARs, the most sensitive design to date, can provide. We demonstrate that the functional persistence of HIT T cells can be augmented by constitutive coexpression of CD80 and 4-1BBL. Finally, we validate the increased antigen sensitivity afforded by HIT receptors in xenograft mouse models of B cell leukemia and acute myeloid leukemia, targeting CD19 and CD70, respectively. Overall, HIT receptors are well suited for targeting cell surface antigens of low abundance.