Mice with induced pulmonary morbidities display severe lung inflammation and mortality following exposure to SARS-CoV-2
Reut Falach, Liat Bar-On, Shlomi Lazar, Tamar Kadar, Ohad Mazor, Moshe Aftalion, David Gur, Yentl Evgy, Ohad Shifman, Tamar Aminov, Ofir Israeli, Inbar Cohen-Gihon, Galia Zaide, Hila Gutman, Yaron Vagima, Efi Makdasi, Dana Stein, Ronit Rosenfeld, Ron Alcalay, Eran Zahavy, Haim Levy, Itai Glinert, Amir Ben-Shmuel, Tomer Israely, Sharon Melamed, Boaz Politi, Hagit Achdout, Shmuel Yitzhaki, Chanoch Kronman, Tamar Sabo
Reut Falach, Liat Bar-On, Shlomi Lazar, Tamar Kadar, Ohad Mazor, Moshe Aftalion, David Gur, Yentl Evgy, Ohad Shifman, Tamar Aminov, Ofir Israeli, Inbar Cohen-Gihon, Galia Zaide, Hila Gutman, Yaron Vagima, Efi Makdasi, Dana Stein, Ronit Rosenfeld, Ron Alcalay, Eran Zahavy, Haim Levy, Itai Glinert, Amir Ben-Shmuel, Tomer Israely, Sharon Melamed, Boaz Politi, Hagit Achdout, Shmuel Yitzhaki, Chanoch Kronman, Tamar Sabo
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Research Article COVID-19

Mice with induced pulmonary morbidities display severe lung inflammation and mortality following exposure to SARS-CoV-2

Abstract

Mice are normally unaffected by SARS coronavirus 2 (SARS-CoV-2) infection since the virus does not bind effectively to the murine version of the angiotensin-converting enzyme 2 (ACE2) receptor molecule. Here, we report that induced mild pulmonary morbidities rendered SARS-CoV-2–refractive CD-1 mice susceptible to this virus. Specifically, SARS-CoV-2 infection after application of low doses of the acute lung injury stimulants bleomycin or ricin caused severe disease in CD-1 mice, manifested by sustained body weight loss and mortality rates greater than 50%. Further studies revealed markedly higher levels of viral RNA in the lungs, heart, and serum of low-dose ricin–pretreated mice compared with non-pretreated mice. Furthermore, lung extracts prepared 2–3 days after viral infection contained subgenomic mRNA and virus particles capable of replication only when derived from the pretreated mice. The deleterious effects of SARS-CoV-2 infection were effectively alleviated by passive transfer of polyclonal or monoclonal antibodies generated against the SARS-CoV-2 receptor binding domain (RBD). Thus, viral cell entry in the sensitized mice seems to depend on viral RBD binding, albeit by a mechanism other than the canonical ACE2-mediated uptake route. This unique mode of viral entry, observed over a mildly injured tissue background, may contribute to the exacerbation of coronavirus disease 2019 (COVID-19) pathologies in patients with preexisting morbidities.

Authors

Reut Falach, Liat Bar-On, Shlomi Lazar, Tamar Kadar, Ohad Mazor, Moshe Aftalion, David Gur, Yentl Evgy, Ohad Shifman, Tamar Aminov, Ofir Israeli, Inbar Cohen-Gihon, Galia Zaide, Hila Gutman, Yaron Vagima, Efi Makdasi, Dana Stein, Ronit Rosenfeld, Ron Alcalay, Eran Zahavy, Haim Levy, Itai Glinert, Amir Ben-Shmuel, Tomer Israely, Sharon Melamed, Boaz Politi, Hagit Achdout, Shmuel Yitzhaki, Chanoch Kronman, Tamar Sabo

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Figure 5

Viral RNA levels and viability.

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Viral RNA levels and viability. (A–C) Viral RNA levels in various tissue...
(A–C) Viral RNA levels in various tissues. RT-PCR was performed on tissue homogenates prepared from SARS-CoV-2 mice (empty circles) and LDR–SARS-CoV-2 mice (filled squares) at 2 days after infection (A and B) or at 3, 5, and 7 days after infection (C). A PFU calibration curve tested in parallel was utilized to express Ct values as calculated PFUs. (D) Viral growth kinetics. Lung homogenates prepared from SARS-CoV-2, LDR–SARS-CoV-2, and bleomycin–SARS-CoV-2 mice at 1–3 days after infection were monitored for the presence of viable virus in an in vitro Vero E6 cell culture–based growth kinetics assay (see Methods). Decreasing Ct values over time determined by RT-PCR of cell growth medium samples collected at 0, 24, and 48 hours indicate viral replication in the Vero cells. Asterisks represent statistical significance between adjacent time points of sampling (24 hours compared with t = 0, 48 hours compared with 24 hours) (E) Subgenomic mRNA analysis. Quantitative RT-PCR of E gene sgmRNA was performed on sham-treated (empty circles), LDR-treated (filled circles), and bleomycin-treated (empty triangles) mice lung homogenates prepared 1–3 days after infection with SARS-CoV-2 (5 × 106 PFU/mouse) Asterisks represent statistical significance in comparison to sham-treated mice (empty circles). Data represent mean ± SEM, n = 3–4 per group, analyzed using 2-way ANOVA followed by Bonferroni’s posttests, *P < 0.05, **P < 0.01, ***P < 0.001.