Humanized ACE2 Mice for COVID-19 Research

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To aid researchers globally that are racing to develop antiviral therapies to treat COVID-19 and vaccines to prevent the disease, Applied StemCell has devoted our expertise and technology to the cause, and is proud to offer various mouse modes for the SARS-CoV-2’s spike (S) protein receptor, angiotensin converting enzyme 2 (ACE2): humanized ACE2 (hACE2), reporter tagged-hACE2 and Ace2 knockout (Ace2-KO) models. These mouse models are ideal to help understand the pathogenesis of COVID-19, and to evaluate the efficacy of antiviral drugs and vaccines.

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The coronavirus disease 2019 (COVID-19) is a viral infection that was declared a pandemic on March 11, 2020. The virus responsible for this pandemic is the severe acquired respiratory syndrome coronavirus 2 (SARS-CoV-2, also called 2019-nCoV, HCoV-19, hCoV-19), a novel virus in the Coronaviridae family of viruses.

The SARS-Cov-2 is a positive strand RNA virus that is said to have zoonotic origins. It invades the epithelial cells lining mucosal surfaces (such as the lungs and intestine) through the binding of the viral spike (S) protein layer (that forms the characteristic the “corona” of the virus) to the angiotensin converting enzyme 2 (ACE2) receptor and causes acute respiratory illness and infection. The SARS-CoV-2 virus though closely related to the first SARS virus strain, SARS-CoV which caused a global outbreak in 2003, binds to ACE2 with a much higher affinity than the original strain 1,2,3.

Understanding the pathology of the disease is crucial to developing antiviral therapy and vaccines to treat and prevent infection. Animal models that mimic the human course of the disease are very important for thorough testing of the developed therapies before approval for use in patients. Models that effectively mimic the tropism of the virus in the nasal mucosa and intestine, viral shedding, and the pathology of the severe respiratory illness will be able to successful in evaluating therapies and vaccines.

Research with mouse models of the first severe acquired respiratory syndrome revealed that the murine ACE2 (mACE2) was not as susceptible to the virus infection as the human ACE2 (hACE2) 4,5. Transgenic mouse models were then generated to express the hACE2 under different constitutive promoters such as the human cytokeratin 18 (K18) promoter (specific to airway, gastrointestinal, liver and kidney epithelium) 6,7, chicken beta-actin promotor with a cytomegalovirus IE enhancer (CAG) 8 and the murine ACE2 promoter 9. These mouse models were generated by random transgene insertion at an unspecified locus and both mACE2 and hACE2 were expressed together. In all these models, hACE2 was expressed in high levels in the lungs, intestinal epithelia, liver, colon, and kidney, and when challenged with a clinical strain of the SARS-CoV virus, the mice developed severe infections along with associated pathological findings that correlated with level of hACE2 expression 10.

However, in mice with mACE2 promoter driven expression of the hACE2, the mice showed less severe clinical illness and mortality for both the SARS-CoV and the SARS-CoV-2 11 viruses, that may be due to the lower expression of hACE2 driven by the mACE2 promoter 9,10.       

Recently, authors Sun and others generated a humanized ACE2 transgenic mouse model using CRISPR/Cas9, to study the SARS-CoV2. They inserted the full length hACE2 sequence into the endogenous murine ACE2 locus, along with a downstream TdTomato reporter gene. While the previous transgenic models retained the mACE2 expression along with hACE2 expression, in this model the mACE2 expression was disrupted and only the hACE2 was expressed 12. The hACE2-TdTomato transgenic mice did not show any clinical signs of infection or mortality and all the infected mice recovered. The pathological outcomes however recapitulated those from the COVID-19 patients thereby establishing another mouse model for a milder version of COVID-19 13.

Applied StemCell has two complementary technologies, CRISPR/Cas9 and TARGATT™ that can aid in the development of humanized ACE2 mouse models under the control of any promoter of choice. We can also engineer these mouse models as conditional or inducible expression models for better control of the humanized ACE2 expression.

In fact, we are developing an ACE2 mouse model that expresses only the hACE2 under the control of a tissue-specific promoter and with strong, consistent expression of the humanized gene. We predict this model will recapitulate the SARS-CoV-2 infection in humans better than the currently available models. We will update you very soon regarding our unique humanized ACE2 mouse model for COVID-19 and other research areas.

In addition, please browse through our repository for other research-ready ACE2 mouse models.

Don’t see a particular COVID-19 mouse model in our repository? We can custom engineer a mouse model-of-choice using our 11+ years of expertise in genetically engineered mouse model (GEMM) generation using the CRISPR/Cas9 and our proprietary TARGATT™ technologies.

Why Choose Applied StemCell?

  • 12+ years of expertise in mouse model genetic engineering
  • Most up-to-date CRISPR protocols for efficiency and affordability
  • Germline transmission included
  • Facilities operated under the strict AAALAC, SPF and IACUC guidelines
  • We ship globally
  • We also offer downstream validation of your models and drug screening services available

1. "Novel coronavirus structure reveals targets for vaccines and treatments"National Institutes of Health (NIH). 2 March 2020. Archived from the original on 1 April 2020. Retrieved 3 April 2020.

2. Hoffmann, M., Kleine-Weber, H., Schroeder, S., Krüger, N., Herrler, T., Erichsen, S., ... & Müller, M. A. (2020). SARS-CoV-2 cell entry depends on ACE2 and TMPRSS2 and is blocked by a clinically proven protease inhibitor. Cell.

3. Shang, J., Ye, G., Shi, K., Wan, Y., Luo, C., Aihara, H., ... & Li, F. (2020). Structural basis of receptor recognition by SARS-CoV-2. Nature581(7807), 221-224.

4. Glass, W. G., Subbarao, K., Murphy, B., & Murphy, P. M. (2004). Mechanisms of host defense following severe acute respiratory syndrome-coronavirus (SARS-CoV) pulmonary infection of mice. The Journal of Immunology173(6), 4030-4039.

5. Li, W., Greenough, T. C., Moore, M. J., Vasilieva, N., Somasundaran, M., Sullivan, J. L., ... & Choe, H. (2004). Efficient replication of severe acute respiratory syndrome coronavirus in mouse cells is limited by murine angiotensin-converting enzyme 2. Journal of virology, 78(20), 11429-11433.

6. Chow, Y. H., O’Brodovich, H., Plumb, J., Wen, Y., Sohn, K. J., Lu, Z., ... & Buchwald, M. (1997). Development of an epithelium-specific expression cassette with human DNA regulatory elements for transgene expression in lung airways. Proceedings of the National Academy of Sciences94(26), 14695-14700.

7. McCray, P. B., Pewe, L., Wohlford-Lenane, C., Hickey, M., Manzel, L., Shi, L., ... & Meyerholz, D. K. (2007). Lethal infection of K18-hACE2 mice infected with severe acute respiratory syndrome coronavirus. Journal of virology81(2), 813-821.

8. Tseng, C. T. K., Huang, C., Newman, P., Wang, N., Narayanan, K., Watts, D. M., ... & Peters, C. J. (2007). Severe acute respiratory syndrome coronavirus infection of mice transgenic for the human Angiotensin-converting enzyme 2 virus receptor. Journal of virology, 81(3), 1162-1173.

9. Yang, X. H., Deng, W., Tong, Z., Liu, Y. X., Zhang, L. F., Zhu, H., ... & Xu, Y. F. (2007). Mice transgenic for human angiotensin-converting enzyme 2 provide a model for SARS coronavirus infection. Comparative medicine, 57(5), 450-459.

10. Sutton, T. C., & Subbarao, K. (2015). Development of animal models against emerging coronaviruses: From SARS to MERS coronavirus. Virology479, 247-258.

11. Bao, L., Deng, W., Huang, B., Gao, H., Liu, J., Ren, L., ... & Qu, Y. (2020). The pathogenicity of SARS-CoV-2 in hACE2 transgenic mice. BioRxiv.

12. Sun, S. H., Chen, Q., Gu, H. J., Yang, G., Wang, Y. X., Huang, X. Y., ... & Guo, Y. (2020). A mouse model of SARS-CoV-2 infection and pathogenesis. Cell Host & Microbe.

13. Cockrell, A. S., Leist, S. R., Douglas, M. G., & Baric, R. S. (2018). Modeling pathogenesis of emergent and pre-emergent human coronaviruses in mice. Mammalian Genome, 29(7-8), 367-383.

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