bioRxiv Science⌕ Search

Biology subjects

Salzer, B.

Publications and source records attributed to Salzer, B..

2 recordsLinked to original sources

TCR/CD3-based synthetic antigen receptors (TCC) convey superior antigen sensitivity combined with high fidelity of activation

Low antigen sensitivity and a gradual loss of effector functions limit the clinical applicability of chimeric antigen receptor (CAR)-modified T-cells and call for alternative antigen receptor designs for effective T-cell-based cancer immunotherapy. Here we applied advanced microscopy to demonstrate that TCR/CD3-based synthetic constructs (TCC) outperform second-generation CAR formats with regard to conveyed antigen sensitivities by up to a thousand-fold. TCC-based antigen recognition occurred without adverse non-specific signaling, which is typically observed in CAR-T-cells, and did not depend - unlike sensitized peptide/MHC detection by conventional T-cells - on CD4- or CD8- coreceptor engagement. TCC-endowed signaling properties may prove critical when targeting antigens in low abundance and aiming for a durable anti-cancer response.

immunology↗

Inefficient exploitation of accessory receptors reduces the sensitivity of chimeric antigen receptors.

Chimeric antigen receptors (CARs) can re-direct T cells to target abnormal cells but their activity is limited by a profound defect in antigen sensitivity, the source of which remains unclear. Here we show that, while CARs have a >100-fold lower antigen sensitivity compared to the T cell receptor (TCR) when antigen is presented on antigen-presenting-cells (APCs), they have nearly identical sensitivity when antigen is presented as purified protein on artificial surfaces. We next measured the impact of engaging accessory receptors (CD2, LFA-1, CD28, CD27, 4-1BB) on antigen sensitivity by adding their purified ligands. Unexpectedly, we found that engaging CD2 or LFA-1 improved TCR antigen sensitivity by 125 and 22-fold, respectively, but only improved CAR sensitivity by <5-fold. This differential effect of CD2 and LFA-1 engagement on TCR versus CAR sensitivity was confirmed using APCs. We found that sensitivity to antigen can be partially restored by fusing the CAR variable domains to the TCR CD3{varepsilon} subunit (also known as a TRuC), and fully restored by exchanging the CAR variable domains with the TCR{beta} variable domains (also known as STAR or HIT). Importantly, these improvements in TRuC and STAR/HIT sensitivity can be predicted by their enhanced ability to exploit CD2 and LFA-1. These findings demonstrate that the CAR sensitivity defect is a result of their inefficient exploitation of accessory receptors, and suggest approaches to increase sensitivity.

immunology↗