The Tissue Distribution of SARS-CoV-2 in Transgenic Mice With Inducible Ubiquitous Expression of hACE2

Abstract

The novel coronavirus disease COVID-19 has become one of the most socially significant infections. One of the main models for COVID-19 pathogenesis study and anti-COVID-19 drug development is laboratory animals sensitive to the virus. Herein, we report SARS-CoV-2 infection in novel transgenic mice conditionally expressing human ACE2 (hACE2), with a focus on viral distribution after intranasal inoculation. Transgenic mice carrying hACE2 under the floxed STOP cassette [(hACE2-LoxP(STOP)] were mated with two types of Cre-ERT2 strains (UBC-Cre and Rosa-Cre). The resulting offspring with temporal control of transgene expression were treated with tamoxifen to induce the removal of the floxed STOP cassette, which prevented hACE2 expression. Before and after intranasal inoculation, the mice were weighed and clinically examined. On Days 5 and 10, the mice were sacrificed for isolation of internal organs and the further assessment of SARS-CoV-2 distribution. Intranasal SARS-CoV-2 inoculation in hACE2-LoxP(STOP)×UBC-Cre offspring resulted in weight loss and death in 6 out of 8 mice. Immunostaining and focus formation assays revealed the most significant viral load in the lung, brain, heart and intestine samples. In contrast, hACE2-LoxP(STOP) × Rosa-Cre offspring easily tolerated the infection, and SARS-CoV-2 was detected only in the brain and lungs, whereas other studied tissues had null or negligible levels of the virus. Histological examination revealed severe alterations in the lungs, and mild changes were observed in the brain tissues. Notably, no changes were observed in mice without tamoxifen treatment. Thus, this novel murine model with the Cre-dependent activation of hACE2 provides a useful and safe tool for COVID-19 studies.

An engineered ACE2 decoy neutralizes the SARS-CoV-2 Omicron variant and confers protection against infection in vivo

“…5D). To confirm efficacy in a more severe model, we examined the effect of engineered ACE2 on survival of CAG–human ACE2 (hACE2) mice that overexpress hACE2 highly and ubiquitously and exhibit more severe SARS-CoV-2 transmission to the brain ( 13 ), as compared with K18-hACE2 mice directing epithelia-specific expression ( 14 – 16 ). The mice were challenged with 1 × 10 3 PFU of Omicron through the intranasal route, and engineered ACE2 was intravenously administered 2 hours after inoculation at a dose of 20 mg/kg.…”

Creation of transgenic mice susceptible to coronaviruses: a platform for studying viral pathogenesis and testing vaccines

“…It should be emphasized that erythrocyte aggregates were present in the lung tissue in abundance, which was indicative of clotting. In contrast to lung tissue samples, no aberrations were found in the histologi cal examination of the brain except for abundant erythrocyte aggregates as a sign of clotting (Dolskiy et al, 2022). All experimental transgenic mice died on day 5 to 10 after the intranasal inoculation.…”

“…In heterozygous ACE2-GFP and Cre-transgene mice, the transgene was ac tivated with tamoxifen, which activates Cre-UBC, which, in turn, cuts out the STOP cassette and activates the expression of ACE2 and the reporter gene (Bruter et al, 2021). Thus, heterozygous mice become susceptible to coronavirus infec tion (Dolskiy et al, 2022).…”

Advances in Modelling COVID-19 in Animals

“…Their results further suggested that severity and infection progress is dependent on the particular Cre driver, more specifically on its expression potency. Furthermore, relatively recent changes in renin-angiotensin system due to hACE2 overexpression can be another factor influencing response to the infection (Dolskiy et al, 2022).…”

“…et al, 2007;Yang XH. et al, 2007;McCray et al, 2007;Tseng et al, 2007;Menachery et al, 2016;Jiang et al, 2020;) Bruter et al, 2021Dolskiy et al, 2022).…”