The current coronavirus disease (COVID-19) pandemic remains one of the most serious public health problems. Increasing evidence shows that infection by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes a very complex and multifaceted disease that requires detailed study. Nevertheless, experimental research on COVID-19 remains challenging due to the lack of appropriate animal models. Herein, we report novel humanized mice with Cre-dependent expression of hACE2, the main entry receptor of SARS-CoV-2. These mice carry hACE2 and GFP transgenes floxed by the STOP cassette, allowing them to be used as breeders for the creation of animals with tissue-specific coexpression of hACE2 and GFP. Moreover, inducible expression of hACE2 makes this line biosafe, whereas coexpression with GFP simplifies the detection of transgene-expressing cells. In our study, we tested our line by crossing with Ubi-Cre mice, characterized by tamoxifen-dependent ubiquitous activation of Cre recombinase. After tamoxifen administration, the copy number of the STOP cassette was decreased, and the offspring expressed hACE2 and GFP, confirming the efficiency of our system. We believe that our model can be a useful tool for studying COVID-19 pathogenesis because the selective expression of hACE2 can shed light on the roles of different tissues in SARS-CoV-2-associated complications. Obviously, it can also be used for preclinical trials of antiviral drugs and new vaccines.

Graphic abstract

中文翻译：

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具有 Cre 依赖性 GFP 和人 ACE2 共表达的新型转基因小鼠：研究 COVID-19 发病机制的安全工具

当前的冠状病毒病 (COVID-19) 大流行仍然是最严重的公共卫生问题之一。越来越多的证据表明，严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 感染会导致一种非常复杂和多方面的疾病，需要进行详细研究。尽管如此，由于缺乏合适的动物模型，对 COVID-19 的实验研究仍然具有挑战性。在此，我们报告了具有 Cre 依赖性表达 hACE2（SARS-CoV-2 的主要进入受体）的新型人源化小鼠。这些小鼠携带hACE2和GFPSTOP 盒中的转基因，使它们可以用作培育具有组织特异性 hACE2 和 GFP 共表达的动物的育种者。此外，hACE2 的诱导表达使这条线具有生物安全性，而与 GFP 的共表达简化了转基因表达细胞的检测。在我们的研究中，我们通过与 Ubi-Cre 小鼠杂交来测试我们的品系，其特征在于他莫昔芬依赖性的 Cre 重组酶的普遍激活。给予他莫昔芬后，STOP盒的拷贝数减少，后代表达hACE2和GFP，确认我们系统的效率。我们相信我们的模型可以成为研究 COVID-19 发病机制的有用工具，因为 hACE2 的选择性表达可以阐明不同组织在 SARS-CoV-2 相关并发症中的作用。显然，它也可以用于抗病毒药物和新疫苗的临床前试验。

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