Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), NMPA Key Laboratory for Research and Evaluation of Radiopharmaceuticals (National Medical Products Administration), Department of Nuclear Medicine, Peking University Cancer Hospital & Institute, Beijing, 100142, China.
Acta Pharmacol Sin. 2022 Jul;43(7):1749-1757. doi: 10.1038/s41401-021-00809-y. Epub 2021 Nov 23.
The spike protein of SARS-CoV-2 interacts with angiotensin-converting enzyme 2 (ACE2) of human respiratory epithelial cells, which leads to infection. Furthermore, low-dose radiation has been found to reduce inflammation and aid the curing of COVID-19. The receptor binding domain (RBD), a recombinant spike protein with a His tag at the C-terminus, binds to ACE2 in human body. We thus constructed a radioiodinated RBD as a molecule-targeted probe to non-invasively explore ACE2 expression in vivo, and to investigate radiotherapy pathway for inhibiting ACE2. RBD was labeled with [I]NaI using an N-bromosuccinimide (NBS)-mediated method, and I-RBD was obtained after purification with a specific activity of 28.9 GBq/nmol. Its radiochemical purity was (RCP) over 90% in saline for 5 days. The dissociation constant of I-RBD binding to hACE2 was 75.7 nM. The uptake of I-RBD by HeLa cells at 2 h was 2.96% ± 0.35%, which could be substantially blocked by an excessive amount of RBD, and drop to 1.71% ± 0.23%. In BALB/c mice, the biodistribution of I-RBD after intravenous injection showed a moderate metabolism rate, and its 24 h-post injection (p.i.) organ distribution was similar to the expression profile in body. Micro-PET imaging of mice after intrapulmonary injection showed high uptake of lung at 1, 4, 24 h p.i.. In conclusion, the experimental results demonstrate the potential of I-RBD as a novel targeted molecular probe for COVID-19. This probe may be used for non-invasive ACE2 mapping in mammals.
SARS-CoV-2 的刺突蛋白与人呼吸道上皮细胞的血管紧张素转换酶 2（ACE2）相互作用，导致感染。此外，已经发现低剂量辐射可以减少炎症并有助于治疗 COVID-19。受体结合域（RBD）是一种带有 C 末端 His 标签的重组刺突蛋白，与人体中的 ACE2 结合。因此，我们构建了放射性碘标记的 RBD 作为一种分子靶向探针，以非侵入性地探索体内 ACE2 的表达，并研究抑制 ACE2 的放射治疗途径。使用 N-溴代琥珀酰亚胺（NBS）介导的方法用 [I]NaI 标记 RBD，并用特异性为 28.9GBq/nmol 的方法纯化后获得 I-RBD。其在盐水中的放射化学纯度（RCP）在 5 天内超过 90%。I-RBD 与 hACE2 结合的解离常数为 75.7nM。HeLa 细胞在 2 小时时摄取 I-RBD 的摄取率为 2.96%±0.35%，过量的 RBD 可显著阻断摄取，摄取率降至 1.71%±0.23%。在 BALB/c 小鼠中，静脉注射 I-RBD 后的生物分布显示出中等的代谢率，其 24 小时后（p.i.）器官分布与体内表达谱相似。肺内注射后小鼠的 micro-PET 成像显示，肺在 1、4、24 小时 p.i.时摄取率高。总之，实验结果表明 I-RBD 作为 COVID-19 的新型靶向分子探针具有潜力。该探针可用于哺乳动物中 ACE2 的非侵入性成像。
