尽管免疫检查点阻断(ICB)和养成性T细胞转移(ACT)疗法已取得显著的临床疗效，但大多数患者并未对免疫疗法作出反应。肿瘤浸润性T细胞是免疫疗法的关键因素，具有动态变化。因此，对于肿瘤浸润性T细胞而言，可靠的实时体内成像系统比免疫组化分析更有价值，可用于预测治疗反应和指导免疫疗法。在此研究中，我们开发了一种新的SPECT / CT成像探针99mTc-sum IL-2，靶向肿瘤浸润性T细胞上的IL-2Rβ / IL-2Rγ（CD122 / CD132）受体，并评估其在预测抗PD-L1（αPD-L1）疗法的免疫反应以及跟踪ACT疗法中输注的T细胞方面的应用。在不同T细胞亚型中测定了超级突变IL-2（sum IL-2）的结合亲和力，随后通过Sortase-A介导的位点特异性转肽作用将Sum IL-2标记为99mTc。在MC38小鼠模型中进行了99mTc-sum IL-2的SPECT / CT成像和生物分布研究。在上述研究中，采用野生型IL-2（IL-2）作为对照组。最后，我们评估了99mTc-sum IL-2 SPECT / CT在αPD-L1免疫疗法和ACT疗法背景下检测肿瘤浸润性T细胞的能力。Sum IL-2优先结合到CD8 + T细胞，尤其是激活的CD8 + T细胞，而IL-2则偏向于结合Treg细胞。因此，99mTc-sum IL-2可以检测到肿瘤浸润性T细胞。在MC38肿瘤模型中，SPECT / CT成像显示αPD-L1治疗后99mTc-sum IL-2的肿瘤摄取量增加，表明该治疗显著增加了肿瘤浸润性T细胞，从而产生了相应的治疗效果。此外，99mTc-sum IL-2 SPECT / CT还可以跟踪ACT疗法期间特异性抗原细胞毒性CD8 + T细胞的浸润。99mTc-sum IL-2具有非侵入性和特异性SPECT / CT成像肿瘤浸润性T细胞的巨大临床潜力，可以及时预测和评估ICB和ACT疗法的治疗效果。 © 作者（或他们的雇主）2023年。在CC BY-NC下允许重用。没有商业再利用。由BMJ发表。

Although immune checkpoint blockade (ICB) and adoptive T cell transfer (ACT) therapy have achieved impressive clinical outcomes, majority of patients do not respond to immunotherapy. Tumor-infiltrating T cells, a critical factor to immunotherapy, is dynamically changing. Therefore, a reliable real-time in vivo imaging system for tumor-infiltrating T cells, but not immunohistochemical analyses, will be more valuable to predict response and guide immunotherapy. In this study, we developed a new SPECT/CT imaging probe 99mTc-sum IL-2 targeting the IL-2Rβ/IL-2Rγ (CD122/CD132) receptor on tumor-infiltrating T cells, and evaluated its application in predicting the immune response to anti-PD-L1 (αPD-L1) therapy as well as tracking infused T cells in ACT therapy.The binding affinity of the super mutated IL-2 (sum IL-2) in various T cell subtypes was measured. Sum IL-2 was subsequently labeled with 99mTc through Sortase-A mediated site-specific transpeptidation. SPECT/CT imaging and biodistribution studies of 99mTc-sum IL-2 were performed in a MC38 mouse model. Wild type IL-2 (IL-2) was used as control in the above studies. Finally, we evaluated 99mTc-sum IL-2 SPECT/CT for the detection of tumor-infiltrating T cells in the context of αPD-L1 immunotherapy and ACT therapy.Sum IL-2 preferentially bound to CD8+ T cells, especially activated CD8+ T cells, while IL-2 showed biased binding to Treg cells. As a result, 99mTc-sum IL-2 could detect tumor-infiltrating T cells. In the MC38 tumor model, SPECT/CT imaging showed the increased tumor uptake of 99mTc-sum IL-2 after αPD-L1 treatment, suggesting that the treatment significantly increased tumor-infiltrating T cells, resulting in a correspondingly significant curative effect. In addition, 99mTc-sum IL-2 SPECT/CT could also track the infiltration of antigen-specific cytotoxic CD8+ T cells during ACT therapy.99mTc-sum IL-2 has great clinical potential for non-invasive and specific SPECT/CT imaging of tumor-infiltrating T cells as well as for timely prediction and evaluation of the therapeutic efficacy of ICB and ACT therapy.© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.