Fig. 3.

In vivo efficacy of VV116, nirmatrelvir, and the VV116 plus nirmatrelvir combination in 5-day-old suckling mice infected with HCoV-OC43. a Schematic of the experimental design for therapeutic treatment in suckling mice. Mice were intranasally challenged with 10⁴ TCID50 of HCoV-OC43. Mice were divided into 9 groups (n = 5 for each group): the vehicle group, the group receiving VV116 10 mpk, the group receiving VV116 25 mpk, the group receiving VV116 50 mpk, the group receiving nirmatrelvir 10 mpk with ritonavir 50 mpk, the group receiving nirmatrelvir 25 mpk with ritonavir 50 mpk, the group receiving drug combination of VV116 10 mpk and nirmatrelvir 10 mpk with ritonavir 50 mpk (Combo 1), the group receiving drug combination of VV116 25 mpk and nirmatrelvir 25 mpk with ritonavir 50 mpk (Combo 2), or the group receiving EIDD-2801 200 mpk. Vehicle or drug was administered at 2 h post-infection, and then quaque die (q.d.) from day 1 to day 4. Lung tissues were collected at 5 days post-infection (n = 5). b Determination of viral RNA copies targeting nucleoprotein genes in the brains, spinal cords, lungs, and kidneys collected on day 5 by real-time fluorescence quantitative PCR. c Determination of viral titers in the brains, spinal cords, lungs, and kidneys collected on day 5 by immunoplaque assay. d Cytokine gene expression was measured in the brain, spinal cord, lungs, and kidneys at day 5. The relative gene expression of IL-1β, IL-6, IFNAR, TNF-α, CCL2, CXCL10, and ISG15 was compared to that of unchallenged mice. e–v Immunofluorescence staining of brains and spinal cords to detect the SARS-CoV-2 antigen. e, n Vehicle, f, o EIDD2801-200 mpk, g, p VV116-50 mpk, h, q VV116-10 mpk, i, r nirmatrelvir-10 mpk + rito-50 mpk, j, s Combo 1, k, t VV116-25 mpk, l, u nirmatrelvir-25 mpk with ritonavir-50 mpk, and m, v Combo 2. The scale bars on the pictures of tissue slides indicate 1000 µm. The data on viral copies and viral titers were statistically analyzed with Student’s t-test. *P < 0.05; **P < 0.01; ***P < 0.001; and ns, not significant