Zika virus-like particle vaccine fusion loop mutation increases production yield but fails to protect AG129 mice against Zika virus challenge
Fig 7
Ab-dependent Enhancement in vitro assay.
(A-C) Fold enhancement of infection is represented for each serum dilution tested, ranging from 10-fold up to 2,430-fold. Fold-enhancement reflects the ratio of the percentage of cells infected with diluted serum-treated virus to medium only-treated virus. The calculated cutoff for ADE activity, shown by dot and dashed line, was calculated as the mean fold-enhancement values of the negative control groups (Alum-only, naïve, and uninfected) + 3 standard deviations (SD). Each symbol indicates the geometric mean of a dose group (5 mice), and error bars represent geometric SD. The three dose groups, 0.1μg (A), 1μg (B) and 10μg (C), were separated into different graphs in which lead and F108A VLP-immunized mice are compared. The Alum-only group is shown in each panel for comparative purposes. Statistical comparisons of enhancement data were performed at each dose using one-way ANOVA test followed by pairwise Sidak’s multiple comparisons between lead and F0108A groups at each serum dilution (*P<0.05; **P<0.01; ***P<0.001; ****P<0.0001; ns, not significant). (D) Fold-enhancement of infection of cells infected with the 10-fold serum dilution. Each symbol represents the geometric mean of two independent measurements for an individual animal. Horizontal bars represent the geometric mean titer of each group. The symbol † denotes a mouse that succumbed after challenge. Statistical comparisons were performed using ANOVA test followed by Dunnett’s multiple comparisons tests with significance levels denoted as in (A-C) above. All VLP groups were compared to the Alum-only group. Additional pairwise comparisons were performed between titers of lead and F108A groups at each dose with significance level for each comparison shown above each bar.