Abstract
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 [124I]NaI using an N-bromosuccinimide (NBS)-mediated method, and 124I-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 124I-RBD binding to hACE2 was 75.7 nM. The uptake of 124I-RBD by HeLaACE+ 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 124I-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 124I-RBD as a novel targeted molecular probe for COVID-19. This probe may be used for non-invasive ACE2 mapping in mammals.
【초록키워드】 COVID-19, SARS-CoV-2, Inflammation, ACE2, Infection, lung, angiotensin-converting enzyme 2, metabolism, Spike protein, hACE2, Receptor binding domain, Radiotherapy, mice, RBD, low-dose, pathway, molecular, in vivo, distribution, ACE2 expression, moderate, binding, biodistribution, Recombinant spike protein, Radiation, Non-invasive, Intravenous injection, injection, mammals, BALB/c mice, purification, C-terminus, respiratory epithelial cells, organ, probe, Cell, high uptake, expression profile, bind, blocked, interact, reduce, inhibiting, was obtained, intrapulmonary, 【제목키워드】 angiotensin-converting enzyme 2, SARS-CoV-2 receptor, mice, Non-invasive, binding domain, approach,