Figure 2: rSARS-CoV-2Nluc expression in infected K18 hACE2 transgenic mice.
(A-B) Four-to-six-week-old female K18 hACE2 transgenic mice were mock-infected (N = 4) or infected with rSARS-CoV-2/WT (N = 4) or rSARS-CoV-2/Nluc (N = 4) using 105 PFU per animal. The mice were anesthetized at 1-, 2-, 4- and 6-days post-infection, after being retroorbital injected with the Nluc substrate. (A) Nluc expression was determined under an in vivo imaging system, and lungs from mock-infected and infected mice were excised and photographed at 1-, 2-, 4- and 6-days post-infection. (B) Nluc intensity was quantitively analyzed by the image analysis software and (C) gross lesions on the lung surface were quantitively analyzed by ImageJ (C) **P < 0.01. (D) Viral titers in the nasal turbinate (left), lungs (middle), and brain (right) from mice infected with rSARS-CoV-2/WT and rSARS-CoV-2/Nluc were determined by plaque assay. (E) Nluc activity in the nasal turbinate (left), lungs (middle) and brain (right) were measured under a luciferase multi-plate reader. ns, not significant.Mock- and virus-infected mice were monitored for 12 days for changes in (F) body weight and (G) survival. All data are presented as mean ± SD for each group and analyzed by SPSS13.0 (IBM). A P value of less than 0.05 (P < 0.05) was considered statistically significant. This figure has been modified from Ye C. et al.41.