Fig. 1. Replication and DENV-specific ADE in cell cultures and placental explants.
a ZIKV replication in placental cell lines. Cells were infected with ZIKV at MOI of 0.1. ZIKV genome RNA concentrations were measured by real-time RT-PCR for 3 days after infection. Each datum point represents the mean of triplicates with SD. b ZIKV replication kinetics in different placental tissue explants and ADE by DENV antibodies. Placental villus, maternal decidua, and amnion explants from three donors were infected with ZIKV (1.5 × 105 PFU/mL) with or without prior incubation with human sera containing antibodies against DENV-1, DENV-2, or DENV-4. Four dpi ZIKV concentrations were quantified by real-time RT-PCR. Each column represents the median of 9 (ZIKV) or 27 explants (ZIKV + D) with interquartile range. Statistical analysis was performed with the Mann–Whitney test (*P < 0.05). c–e ZIKV infection kinetics in presence or absence of DENV-, YFV-, or CHIKV-immune sera, or naïve human serum. Placental villus (c), maternal decidua (d), and amnion (e) explants from four donors were infected with ZIKV (1.5 ×105 PFU/mL) with or without prior incubation with human sera containing either antibodies against three different DENV serotypes, YFV or CHIKV, or a control serum. Virus concentrations of inocula 0 dpi and viral progeny 1, 2, 4, 6, and 8 dpi were quantified by real-time RT-PCR. All infections were done in triplicates for each placenta. Data points represent the mean of 12 explants per setting with SEM. Inocula were measured once per placenta and setting. ZIKV + D1 ZIKV + DENV-1-immune serum, ZIKV + D2 ZIKV + DENV-2-immune serum, ZIKV + D4 ZIKV + DENV-4-immune serum, ZIKV + YF ZIKV + YFV-immune serum, ZIKV + CH ZIKV + CHIKV-immune serum, ZIKV + S− ZIKV + flavi- and alphavirus-naïve serum