Figure 1.

Immunization and challenge schedule. Mice were immunized intramuscularly (i.m.) with PBS (background control) or with ZIKV EDIII without an adjuvant, or with aluminum salts (Alum), monophosphoryl lipid A (MPL), Alum + MPL, or MF59 adjuvant and boosted at day 21 after the initial dose. Sera were collected at seven days after the boost (day 28) and used to determine ZIKV E or EDIII-specific antibody, and neutralizing antibody levels. Mice were injected with an anti-interferon-α/β receptor 1 (Ifnar1) antibody (in order to become susceptible to subsequent ZIKV infection) [36,37] at nine days after the boost (day 30) and subsequently challenged with ZIKV (strain R103451, 6 × 10⁵ plaque-forming unit (PFU)) the following day (day 31). Sera and tissue samples were collected three days post-challenge (day 34) and used to determine ZIKV titers and viral load (RNA copies). Splenocytes were also tested for the ZIKV EDIII-specific cellular immune response.