Fig. 4: Evaluation of in vivo antiviral activity of prophylactic and therapeutic Y180 in the lethal K18-hACE2 transgenic mouse model for COVID-19.
a, Schematic illustration of experiment design. K18-hACE2 transgenic mice were challenged with either 250 PFU B.1.1.7 or 1 × 105 PFU B.1.617.1. Oral administration of either 150 mg kg−1 dose−1 Y180 or vehicle solution was performed twice daily (bis in die; b.i.d.) for 8 d or until death, whichever was earlier. For mice with prophylactic treatment, Y180 treatment was initiated at 1 h before virus challenge, whereas administration of Y180 was postponed until 6 h.p.i. for mice receiving therapeutic treatment. b,c, Mice infected with B.1.1.7 were killed at 2 d.p.i. and 4 d.p.i. for detection of viral RdRp gene copies in nasal turbinate (b) and lung (c) by RT–qPCR (n = 5 at 2 d.p.i.; n = 6 at 4 d.p.i.). d,e, Mice infected with B.1.1.7 were killed at 2 d.p.i. and 4 d.p.i. for detection of infectious viral titre in nasal turbinate (d) and lung (e) by plaque assay (n = 5 at 2 d.p.i.; n = 6 at 4 d.p.i.). f, Gene expression of IFNγ and IP10 in the lung of mice infected with B.1.1.7 at 4 d.p.i. were determined with RT–qPCR (n = 5 at 2 d.p.i.; n = 6 at 4 d.p.i.). g, Immunohistochemistry staining visualizing the nucleocapsid protein (brown, indicated by black arrows) in the lung and nasal turbinate of mice infected with B.1.1.7 at 2 d.p.i. Scale bar, 100 µm. h, Histology analysis visualizing the virus-induced pathology in the lung and nasal turbinate of mice infected with B.1.1.7 at 2 d.p.i. Representative images of alveoli, bronchioles and blood vessels of the lung are indicated by yellow dotted circles with numbers, and enlarged in images 1, 2 and 3, respectively. Yellow arrowheads indicate inflammatory infiltrations in the alveoli, dead cell debris in the bronchioles and mononuclear cell infiltrations in the blood vessels in the enlarged images 1–3. Black arrowheads, haemorrhage; black arrows, epithelium detachment; #, dead cell debris. Scale bar, 100 µm for enlarged images 1–3, 200 µm for nasal turbinate image. Three mice were sampled in each group and 4–6 sections from each animal were used for histology analysis. i,j, Mice challenged with 1 × 105 PFU B.1.617.1 were treated with either 150 mg kg−1 dose−1 Y180 or vehicle solution twice daily (n = 8–9). Survival (i) and body weight (j) of mice were monitored daily until 14 d.p.i. Data were obtained from two independent experiments. All data are shown as mean ± s.d. Statistical differences were determined by two-way ANOVA in b–e and j, one-way ANOVA in f or log-rank (Mantel-Cox) test in i. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.
