Highly susceptible SARS-CoV-2 model in CAG promoter–driven hACE2-transgenic mice
Masamitsu N. Asaka, Daichi Utsumi, Haruhiko Kamada, Satoshi Nagata, Yutaka Nakachi, Tomokazu Yamaguchi, Yoshihiro Kawaoka, Keiji Kuba, Yasuhiro Yasutomi
Masamitsu N. Asaka, Daichi Utsumi, Haruhiko Kamada, Satoshi Nagata, Yutaka Nakachi, Tomokazu Yamaguchi, Yoshihiro Kawaoka, Keiji Kuba, Yasuhiro Yasutomi
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Resource and Technical Advance COVID-19

Highly susceptible SARS-CoV-2 model in CAG promoter–driven hACE2-transgenic mice

Abstract

COVID-19, caused by SARS-CoV-2, has spread worldwide with dire consequences. To urgently investigate the pathogenicity of COVID-19 and develop vaccines and therapeutics, animal models that are highly susceptible to SARS-CoV-2 infection are needed. In the present study, we established an animal model highly susceptible to SARS-CoV-2 via the intratracheal tract infection in CAG promoter–driven human angiotensin-converting enzyme 2–transgenic (CAG-hACE2) mice. The CAG-hACE2 mice showed several severe symptoms of SARS-CoV-2 infection, with definitive weight loss and subsequent death. Acute lung injury with elevated cytokine and chemokine levels was observed at an early stage of infection in CAG-hACE2 mice infected with SARS-CoV-2. Analysis of the hACE2 gene in CAG-hACE2 mice revealed that more than 15 copies of hACE2 genes were integrated in tandem into the mouse genome, supporting the high susceptibility to SARS-CoV-2. In the developed model, immunization with viral antigen or injection of plasma from immunized mice prevented body weight loss and lethality due to infection with SARS-CoV-2. These results indicate that a highly susceptible model of SARS-CoV-2 infection in CAG-hACE2 mice via the intratracheal tract is suitable for evaluating vaccines and therapeutic medicines.

Authors

Masamitsu N. Asaka, Daichi Utsumi, Haruhiko Kamada, Satoshi Nagata, Yutaka Nakachi, Tomokazu Yamaguchi, Yoshihiro Kawaoka, Keiji Kuba, Yasuhiro Yasutomi

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Figure 9

Protection against SARS-CoV-2 infection by the injection of RBD-Fc–immunized mouse plasma.

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Protection against SARS-CoV-2 infection by the injection of RBD-Fc–immun...
(A) Schematic showing the experimental schedule. Male and female CAG-hACE2 mice were intravenously injected with pooled plasma from RBD-mFc/AddaVax–immunized mice at doses of 15 μg/shot (n = 6), 50 μg/shot (n = 5), and 150 μg/shot (n = 6) 1 day before SARS-CoV-2 infection and were infected via respiratory tract with SARS-CoV-2 at a dose of 1 × 104 TCID50. CAG-hACE2 mice that were injected with PBS-treated pooled plasma were used as a control (n = 6). (B) The measurement of SARS-CoV-2–neutralizing antibodies in pooled plasma. Black circles and white, violet, and gray diamonds indicate the standard, pooled plasma from PBS/AddaVax–treated mice, pooled plasma from RBD-mFc/AddaVax–immunized mice, and mouse neutralizing antibody, respectively. (C and D) Percentage of initial body weight (C) and survival rate (D). Numbers in C represent the number of mice measured for body weight at each time. Black circles and orange, blue, and red triangles indicate plasma from PBS/AddaVax–immunized mice and RBD-mFc/AddaVax–immunized mice at doses of 150 ng/mL (n = 6), 500 ng/mL (n = 5), and 1500 ng/mL (n = 6), respectively. Data were presented as the mean (B) and the mean ± SEM (C). Statistical analyses were performed using log-rank (mantel-cox) test for survival rate (D). P < 0.05 for the comparison with PBS-treated pool plasma.