Fig. 4: Neurovirulence of the K101R virus in the neonatal mouse model.

a Neurovirulence of viruses in suckling CD-1 P1 mice. One-day-old mice were i.c. inoculated with indicated doses of viruses, The LD₅₀ values were calculated by the Reed–Muench method⁵². The pups were monitored for mortality for 21 days. b, c Viral loads in brains of WT-, K101R- or MR766-infected CD-1 mice. Viral RNA and infectious virus particles in mouse brains were quantified by RT-qPCR and plaque assay, respectively. The data are shown as mean ± SD. Statistical significance was determined using Two-tailed unpaired t test (*p < 0.05, **p < 0.01, ***p < 0.001). The exact p values are (b) MR766, p = 0.0346. K101R, p = 0.0385; (c) MR766, p = 0.0004 (day 7), p = 0.0002 (day 9). K101R, p = 0.0044 (day 7), p = 0.0264 (day 9). d Representative images of coronal plane of brain tissue at day 9 post-inoculation. Top panels show tissues stained with Hematoxylin and Eosin (H&E). Scale bar: 1000 μm. Middle panels show tissues stained with ZIKV E antibody (green) and DAPI (blue). Scale bar: 1000 μm. Down panels represent enlarged areas from red box in the middle of the cortex. Scale bar: 100 μm. e The E protein expression of viruses was detected by IFA with ZIKV-E-specific mAbs at 48 h post-infection. The infection rate was determined by counting the ZIKV-E-positive cell foci as a percentage of cells. The data are shown as mean ± SD. Statistical significance was determined using Two-tailed unpaired t test (**p < 0.01). The exact p value is 0.0084. Source data are provided as a Source Data file.