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Live Imaging and Quantification of Viral Infection in K18 hACE2 Transgenic Mice Using Reporter-Expressing Recombinant SARS-CoV-2
Published on: November 5, 2021
Essential role of TMPRSS2 in SARS-CoV-2 infection in murine airways
Naoko Iwata-Yoshikawa1, Masatoshi Kakizaki2, Nozomi Shiwa-Sudo1
1Department of Pathology, National Institute of Infectious Diseases, Tokyo, Japan.
Abstract:
In cultured cells, SARS-CoV-2 infects cells via multiple pathways using different host proteases. Recent studies have shown that the furin and TMPRSS2 (furin/TMPRSS2)-dependent pathway plays a minor role in infection of the Omicron variant. Here, we confirm that Omicron uses the furin/TMPRSS2-dependent pathway inefficiently and enters cells mainly using the cathepsin-dependent endocytosis pathway in TMPRSS2-expressing VeroE6/TMPRSS2 and Calu-3 cells. This is the case despite efficient cleavage of the spike protein of Omicron. However, in the airways of TMPRSS2-knockout mice, Omicron infection is significantly reduced. We furthermore show that propagation of the mouse-adapted SARS-CoV-2 QHmusX strain and human clinical isolates of Beta and Gamma is reduced in TMPRSS2-knockout mice. Therefore, the Omicron variant isn't an exception in using TMPRSS2 in vivo, and analysis with TMPRSS2-knockout mice is important when evaluating SARS-CoV-2 variants. In conclusion, this study shows that TMPRSS2 is critically important for SARS-CoV-2 infection of murine airways, including the Omicron variant.
Insights
The Omicron variant inefficiently uses the furin/TMPRSS2 pathway but relies on TMPRSS2 for SARS-CoV-2 infection in mouse airways, including in vivo propagation.
Area of Science:
- Virology
- Molecular Biology
- Infectious Diseases
Background:
- Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) utilizes various host proteases for cell entry.
- The role of the furin and Transmembrane Serine Protease 2 (TMPRSS2) pathway in Omicron variant infection is debated.
- Omicron variant's reliance on specific host proteases for cell entry requires further investigation.
Purpose of the Study:
- To investigate the cell entry pathways of the SARS-CoV-2 Omicron variant.
- To determine the role of TMPRSS2 in Omicron variant infection in vitro and in vivo.
- To evaluate the importance of TMPRSS2-knockout mouse models for SARS-CoV-2 variant analysis.
Main Methods:
- In vitro cell culture experiments using VeroE6/TMPRSS2 and Calu-3 cells.
- Analysis of spike protein cleavage efficiency.
- In vivo infection studies using TMPRSS2-knockout mice.
- Propagation assessment of SARS-CoV-2 variants (Omicron, mouse-adapted QHmusX, Beta, Gamma).
Main Results:
- Omicron variant inefficiently uses the furin/TMPRSS2 pathway in cultured cells, favoring cathepsin-dependent endocytosis.
- Despite efficient spike protein cleavage, Omicron infection is significantly reduced in the airways of TMPRSS2-knockout mice.
- Propagation of Omicron, Beta, Gamma, and mouse-adapted SARS-CoV-2 strains is reduced in TMPRSS2-knockout mice.
Conclusions:
- TMPRSS2 is critically important for SARS-CoV-2 infection in murine airways, including the Omicron variant.
- The Omicron variant, while showing distinct in vitro entry mechanisms, still requires TMPRSS2 for efficient in vivo infection.
- TMPRSS2-knockout mouse models are essential for evaluating the in vivo infectivity of emerging SARS-CoV-2 variants.
