Development of a Mouse-Adapted Reporter SARS-CoV-2 as a Tool for Two-Photon In Vivo Imaging

• Published in: Viruses Vol. 16; no. 4; p. 537
• Main Authors: Ueki, Hiroshi, Kiso, Maki, Furusawa, Yuri, Iida, Shun, Yamayoshi, Seiya, Nakajima, Noriko, Imai, Masaki, Suzuki, Tadaki, Kawaoka, Yoshihiro
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 29.03.2024; MDPI
• Subjects: Animal experimentation; Animal models; Animals; Antigens; Bacterial pneumonia; BALB/c; C57BL/6J; Coronaviruses; COVID-19; COVID-19 - virology; COVID-19 infection; Cytomegalovirus; Development and progression; Disease Models, Animal; E coli; Females; fluorescence; genes; Genes, Reporter; Genomes; Health aspects; histology; histopathology; Humans; Imaging systems; in vivo imaging; Infections; Infectious diseases; Inflammation; Laboratories; Light intensity; Lung - diagnostic imaging; Lung - pathology; Lung - virology; Lungs; Medical research; Methods; Mice; Mice, Inbred C57BL; microscopy; mouse model; Pathogenesis; Pathogenicity; Pneumonia; Proteins; SARS-CoV-2; SARS-CoV-2 - genetics; SARS-CoV-2 - pathogenicity; SARS-CoV-2 - physiology; Severe acute respiratory syndrome; Severe acute respiratory syndrome coronavirus 2; Testing; viral pneumonia; Virus Replication; Viruses; Japan; United States > US; COVID-19; SARS-CoV-2; in vivo imaging; mouse model; C57BL/6J; BALB/c; two-photon excitation microscopy
• DOI: 10.3390/v16040537
• ISSN: 1999-4915

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) often causes severe viral pneumonia. Although many studies using mouse models have examined the pathogenicity of SARS-CoV-2, COVID-19 pathogenesis remains poorly understood. In vivo imaging analysis using two-photon excitation microscopy (TPEM) is useful for elucidating the pathology of COVID-19, providing pathological insights that are not available from conventional histological analysis. However, there is no reporter SARS-CoV-2 that demonstrates pathogenicity in C57BL/6 mice and emits sufficient light intensity for two-photon in vivo imaging. Here, we generated a mouse-adapted strain of SARS-CoV-2 (named MASCV2-p25) and demonstrated its efficient replication in the lungs of C57BL/6 mice, causing fatal pneumonia. Histopathologic analysis revealed the severe inflammation and infiltration of immune cells in the lungs of MASCV2-p25-infected C57BL/6 mice, not unlike that observed in COVID-19 patients with severe pneumonia. Subsequently, we generated a mouse-adapted reporter SARS-CoV-2 (named MASCV-Venus-p9) by inserting the fluorescent protein-encoding gene Venus into MASCV2-p25 and sequential lung-to-lung passages in C57BL/6 mice. C57BL/6 mice infected with MASCV2-Venus-p9 exhibited severe pneumonia. In addition, the TPEM of the lungs of the infected C57BL/6J mice showed that the infected cells emitted sufficient levels of fluorescence for easy observation. These findings suggest that MASCV2-Venus-p9 will be useful for two-photon in vivo imaging studies of the pathogenesis of severe COVID-19 pneumonia.