Figure 1.
Development of Mice Sensitized to SARS-CoV-2 Infection
(A and B) To assess hACE2 expression and surface localization, 17CL-1 cells were transduced with Ad5-hACE2 or Ad5-Empty at MOI of 100 at 37°C for 4 h. hACE2 expression was monitored by western blot assay (A) or flow cytometry (B).
(C) Ad5-hACE2 transduced 17CL-1 cells were infected with SARS-CoV-2 at MOI of 0.5 at 48 h post transduction, and virus titers were determined by foci forming assay (FFA) at 24, 48, and 72 hours post infection (h.p.i.).
(D) Five days after transduction with 2.5 × 108 FFU of Ad5-hACE2 or Ad5-Empty in 75 μL of DMEM intranasally, lungs were harvested from BALB/c mice, fixed in zinc formalin, and embedded in paraffin. Sections were stained with an anti-hACE2 antibody (brown color). hACE2 protein (brown color) was detected only in Ad-hACE2-treated mice and was predominantly localized to alveolar epithelial cells. Scale bars, 467 and 94 μm, top and bottom panels, respectively.
(E and F) Ad5-hACE2- or Ad5-Empty-transduced BALB/c or C57BL/6 mice were intranasally infected with 1 × 105 PFU of SARS-CoV-2 in 50 μL of DMEM. Weight changes in 6-to-8-week old BALB/c (E) and C57BL/6 (F) mice were monitored daily (n = 5 mice per group). To obtain virus kinetics in BALB/c (E) and C57BL/6 (F) mice, lungs were harvested and homogenized at the indicated time points, and virus was titered by plaque assay. Titers are expressed as PFU/g lung tissue (n = 3 mice per group per time point). Data are representative of two independent experiments.
(G) 2 d.p.i., lungs were harvested from BALB/c mice, fixed in zinc formalin, and embedded in paraffin. Sections were stained with anti-SARS-CoV-2 N protein. Scale bar, 476 μm.
(H) Representative Hematoxylin-eosin (HE) staining of lungs from BALB/c and C57BL/6 mice harvested at the indicated time points p.i. Scale bars, 443 and 88 μm, top and bottom panels, respectively. Asterisk, edema.
(I) Summary histology scores determined at the indicated time points (n = 4 to 5 mice per group). PMN, neutrophils.
(J) Photographs of lung specimens isolated from infected mice at indicated time points are shown. Arrowheads indicate regions with vascular congestion and hemorrhage.