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Updated: Jul 3, 2025
Live Imaging and Quantification of Viral Infection in K18 hACE2 Transgenic Mice Using Reporter-Expressing Recombinant SARS-CoV-2
Published on: November 5, 2021
Bioluminescence imaging reveals enhanced SARS-CoV-2 clearance in mice with combinatorial regimens
Irfan Ullah1, Fanny Escudie2, Ivan Scandale2
1Department of Internal Medicine, Section of Infectious Diseases, Yale University School of Medicine, New Haven, CT 06520, USA.
Abstract:
Direct acting antivirals (DAAs) represent critical tools for combating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) that have escaped vaccine-elicited spike-based immunity and future coronaviruses with pandemic potential. Here, we used bioluminescence imaging to evaluate therapeutic efficacy of DAAs that target SARS-CoV-2 RNA-dependent RNA polymerase (favipiravir, molnupiravir) or main protease (nirmatrelvir) against Delta or Omicron VOCs in K18-hACE2 mice. Nirmatrelvir displayed the best efficacy followed by molnupiravir and favipiravir in suppressing viral loads in the lung. Unlike neutralizing antibody treatment, DAA monotherapy regimens did not eradicate SARS-CoV-2 in mice, but combining molnupiravir with nirmatrelvir exhibited superior additive efficacy and led to virus clearance. Furthermore, combining molnupiravir with caspase-1/4 inhibitor mitigated inflammation and lung pathology whereas combining molnupiravir with COVID-19 convalescent plasma demonstrated synergy, rapid virus clearance, and 100% survival. Thus, our study provides insights into in vivo treatment efficacies of DAAs and other effective combinations to bolster COVID-19 therapeutic arsenal.
Insights
Direct acting antivirals (DAAs) effectively suppressed SARS-CoV-2 variants in mice. Combining molnupiravir with nirmatrelvir, or with convalescent plasma, achieved virus clearance and improved survival.
Area of Science:
- Virology
- Immunology
- Pharmacology
Background:
- Direct acting antivirals (DAAs) are crucial for combating SARS-CoV-2 variants and future pandemic coronaviruses.
- Vaccine-induced immunity may be insufficient against emerging variants of concern (VOCs).
Purpose of the Study:
- To evaluate the in vivo therapeutic efficacy of DAAs targeting SARS-CoV-2 RNA-dependent RNA polymerase and main protease.
- To assess the efficacy of DAA combinations and other therapeutics against SARS-CoV-2 VOCs in a mouse model.
Main Methods:
- Bioluminescence imaging was used to assess viral loads in K18-hACE2 mice infected with SARS-CoV-2 Delta or Omicron variants.
- Therapeutic efficacy of favipiravir, molnupiravir, nirmatrelvir, and their combinations was evaluated.
Main Results:
- Nirmatrelvir showed the highest efficacy in suppressing lung viral loads, followed by molnupiravir and favipiravir.
- DAA monotherapy did not eradicate SARS-CoV-2, but combining molnupiravir with nirmatrelvir led to virus clearance.
- Combining molnupiravir with caspase-1/4 inhibitor reduced inflammation, while combining it with convalescent plasma showed synergy, rapid clearance, and 100% survival.
Conclusions:
- DAAs offer viable therapeutic options against SARS-CoV-2 VOCs.
- Combination therapies, particularly molnupiravir with nirmatrelvir or convalescent plasma, demonstrate superior efficacy and potential for virus clearance and improved survival.
