Fig. 4. Pathogenicity of African and Asian ZIKV strains in immunocompromised adult mice.

In a first experiment (a, b), male AG129 mice were inoculated with 10³ PFU of ZIKV. Each virus strain was represented by n = 10 mice, with the exception of the F_Polynesia_2013 and Philippines_2012 strains that were represented by n = 8 mice. a Mouse weight over time is shown as the percentage of body weight prior to infection (mean ± standard error). b Mouse survival over time is shown as the percentage of mice alive. Mice were euthanized when reaching humane endpoints (weight loss >20% or/and severe symptom onset). In a second experiment (c–e), male AG129 mice were inoculated with 1 PFU of ZIKV (n = 8 mice per strain). c Time course of mouse viremia is shown in log₁₀-transformed viral genome copies per ml of plasma (mean ± standard error). Three extreme outliers were excluded for the Senegal_2015 strain. d Viral loads in organs collected on day 7 post infection are shown in log₁₀-transformed viral genome copies per mg of tissue. Statistical significance of differences was determined by one-way ANOVA followed by Tukey’s post hoc test for brain, heart and testis, by Brown–Forsythe and Welch ANOVA followed by Games-Howell’s post hoc test (two sided) for epididymis and spinal cord, and by Kruskal–Wallis rank-sum test followed by Dunn’s post hoc test (two sided) for kidney. Viral loads were significantly higher for African than for Asian ZIKV strains in the brain (p < 0.0001), spinal cord (p < 0.0001), testis (p < 0.0001), kidney (p < 0.0001), and heart (p < 0.0001). e Infectious virus in brain and testis collected on day 7 post infection are shown in log₁₀-transformed 50% tissue-culture infectious dose (TCID₅₀) per mg of tissue. The horizontal dotted line indicates the lower limit of detection of the assay (310 TCID₅₀ units per mg of tissue). Statistical significance of differences was determined by Kruskal–Wallis rank-sum test followed by Steel-Dwass’s post hoc test for brain and by one-way ANOVA followed by Tukey’s post hoc test for testis. Infectious titers were significantly higher for African than for Asian ZIKV strains in the brain (p < 0.0001) and testis (p < 0.0001). In (d, e), data are presented as mean ± standard deviation and ZIKV strains not sharing a letter above the graph are statistically significantly different (p < 0.05). Source data are provided as a Source Data file.