Fig. 4.

Antibody responses elicited by ZIKV VLPs or control vaccinations. A A–a BALB/c mice (n = 6) were immunized with three doses of ZIKV VLPs (VLP), purified inactivated ZIKV vaccine (PIV), vAc-hsp70-egfp-infected Sf9 cell lysates (negative control, NC) or PBS at weeks 0, 2 and 4. Blood samples were collected at weeks 0 (pre-immune serum), 2, 4 and 6 (2 weeks after each antigen injection). A–b The purified inactivated ZIKV and VLPs used in a dose (5 μg PIV and 50 μg ZIKV VLPs) were analyzed by Western blot analysis and quantified by densitometry, the level of E (left panel) and prM (right panel) proteins in PIV relative to VLP were 1.11: 1 and 1.21: 1. B Neutralization titers of the immunized mice determined by a microneutralization assay. C ZIKV-specific IgG titers and D VLP-specific IgG titers were measured via ELISA using two coating antigens: purified inactivated ZIKV or ZIKV VLPs. The values represent the mean ± SD of the reciprocal of the highest serial dilution (with an OD450 value 2σ above the mean of the negative control) of six mice per group. The results of three independent experiments (with technical triplicates for each sample) are presented.