Figure 6.

Efficacy of MVA-ZIKV in immunocompromised susceptible IFNAR^−/− mice. (a) Inoculation scheme. Groups of IFNAR^−/− mice (n = 10 mice/group) were immunized with 2 × 10⁷ PFUs of MVA-WT (one dose, at day 0) or MVA-ZIKV (one or two doses, at days 0 and 14, respectively) by the i.p. route. Twenty eight days after the first immunization, mice were challenged with 10⁴ PFUs of ZIKV (PA259459, strain Panama) via the i.p. route (see Methods). (b) ZIKV-neutralizing antibody titers (PRNT₉₀) detected at 13 and 27 days post-prime immunization in sera (n = 5) of animals immunized with one dose of MVA-WT or one or two doses of MVA-ZIKV. Titers of neutralizing antibodies against ZIKV PA259459 strain were determined by a PRNT assay and are expressed as the reciprocal of the serum dilution that inhibited plaque formation by 90% (PRNT₉₀), relative to samples incubated with negative control sera (from day 1 pre-prime). Dashed line indicates the limit of detection (LOD) of the neutralization assay (1/20 dilution). The statistically significant difference between the groups is indicated (****P < 0.0001). (c) ZIKV RNA viremia after challenge. Blood samples were collected at days 2 (n = 5) or 3 (n = 5) post-challenge, and ZIKV RNA viremia was analyzed by quantitative real-time PCR (PFU equivalents/ml). Graph shows mean with each point representing an individual mouse. P values indicate significantly higher responses between the different groups (*P < 0.05; **P < 0.005). (d) ZIKV infectious virus after challenge. Blood samples were collected at days 2 (n = 5) or 3 (n = 5) post-challenge, and ZIKV infectious virus was analyzed by a plaque assay (PFUs/ml). Graph shows mean with each point representing an individual mouse. P values indicate significantly higher responses between the different groups (***P < 0.001, ****P < 0.0001).