Zika virus-like particle vaccine fusion loop mutation increases production yield but fails to protect AG129 mice against Zika virus challenge
Fig 3
Vaccination and induction of lead and F108A VLP binding Abs.
(A) Vaccination and bleeding schedule of AG129 mice are shown. Mice (5 per group) were immunized IM on day 0 and day 28 with doses of 0.1, 1, or 10μg VLP and alum adjuvant. Mice were subsequently SC challenged with ZIKV (Nica 2–16 strain) on day 52. Bleeding was performed on Days 21 and 49 of the study prior to viral challenge. Day 49 sera were tested by sandwich ELISA using captured lead (B) or F108A (C) VLPs, and endpoint titers were calculated. Each symbol represents the mean endpoint dilution of two independent measurements for an individual animal, and the geometric mean titer is depicted by a horizontal bar. The dotted line is the limit of detection (LOD) of the assay, and sera with undetectable binding were assigned a value of one-half LOD (25). Anti-E ZIKV mouse serum (Zoonogen, cat#pa10049) was used as a positive control and to demonstrate binding availability of E for the VLP types. For each capture antigen, endpoint titers of the VLP groups were compared by one-way ANOVA. The symbol † denotes a mouse that succumbed after viral challenge. (D) Relative Binding is the ratio of the lead VLP ELISA endpoint titer divided by the F108A VLP ELISA endpoint titer for each individual sample. Group geometric mean ratios are shown on top, and an equivalence line was placed at y = 1. One-way ANOVA followed by Sidak’s multiple comparison tests for each of the three doses were performed. (E) Comparison of Relative Binding Antibody (bAb) for combined lead vs combined F108A VLP groups is shown. Combined group geometric mean ratios and significance level by unpaired t test are shown on top. Dose group of F108A VLP-immunized mice that succumbed later to viral challenge is indicated. Comparison of the combined groups was by Mann-Whitney U test (ns, not significant, *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001).