Sir William Dunn School of Pathology, University of Oxford, OX1 3RE Oxford, UK.
Proc Natl Acad Sci U S A. 2023 Jan 10;120(2):e2216352120. doi: 10.1073/pnas.2216352120. Epub 2023 Jan 4.
Chimeric antigen receptors (CARs) can redirect 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 CARs have a > 100-fold lower antigen sensitivity compared to the T cell receptor (TCR) when antigen is presented on antigen-presenting cells (APCs) but nearly identical sensitivity when antigen is presented as purified protein. We next systematically measured the impact of engaging important T cell accessory receptors (CD2, LFA-1, CD28, CD27, and 4-1BB) on antigen sensitivity by adding their purified ligands. Unexpectedly, we found that engaging CD2 or LFA-1 improved the antigen sensitivity of the TCR by 125- and 22-fold, respectively, but improved CAR sensitivity by only < 5-fold. This differential effect of CD2 and LFA-1 engagement on the TCR vs. CAR was confirmed using APCs. We found that sensitivity to antigen can be partially restored by fusing the CAR variable domains to the TCR CD3 subunit (also known as a TRuC) and fully restored by exchanging the TCR variable domains for those of the CAR (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.
嵌合抗原受体 (CAR) 可将 T 细胞重定向以靶向异常细胞，但它们的活性受到抗原敏感性的严重缺陷的限制，其来源仍不清楚。在这里，我们表明，当抗原在抗原呈递细胞 (APC) 上呈递时，CAR 的抗原敏感性比 T 细胞受体 (TCR) 低> 100 倍，但当抗原作为纯化蛋白呈递时，其敏感性几乎相同。接下来，我们通过添加其纯化配体，系统地测量了结合重要 T 细胞辅助受体（CD2、LFA-1、CD28、CD27 和 4-1BB）对抗原敏感性的影响。出乎意料的是，我们发现，结合 CD2 或 LFA-1 分别将 TCR 的抗原敏感性提高了 125 倍和 22 倍，但仅将 CAR 敏感性提高了< 5 倍。使用 APC 证实了 CD2 和 LFA-1 对 TCR 与 CAR 的这种不同效应的结合。我们发现，通过将 CAR 可变结构域融合到 TCR CD3 亚基（也称为 TRuC）中，可以部分恢复对抗原的敏感性，而通过将 TCR 可变结构域替换为 CAR 的可变结构域（也称为 STAR 或 HIT）可以完全恢复敏感性。重要的是，TRuC 和 STAR/HIT 敏感性的这些改善可以通过其增强的利用 CD2 和 LFA-1 的能力来预测。这些发现表明，CAR 敏感性缺陷是其对辅助受体利用效率低下的结果，并提出了提高敏感性的方法。
