Zika virus infection in human placental tissue explants is enhanced in the presence of dengue virus antibodies in-vitro

Figures & data

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

Fig. 2 ZIKV replication in different placental tissue explants and ADE by DENV antibodies.

Placental villus (a), maternal decidua (b), and amnion (c) explants were infected in triplicates with ZIKV (1.5 × 10⁵ PFU/mL) with or without prior incubation with human sera that either contained antibodies against one of three different DENV serotypes as indicated, YFV or CHIKV, or a control serum. The virus concentration of the inoculum 0 dpi and viral replication 1, 2, 4, 6, and 8 dpi were determined by quantitative real-time RT-PCR. Explants were obtained from four donors as indicated by black, blue, red, and yellow dots. Medians with interquartile ranges are presented for each treatment. The dashed line shows the threshold for successful infection used for the infection rate calculation in Table 1. The continuous line represents the detection limit of the real-time RT-PCR. Statistical analysis was performed with the Kruskal–Wallis test combined with Dunn’s multiple comparison test. Significant differences are indicated in red (Z + D1), blue (Z + D2), and green (Z + D4) (*P < 0.05, **P < 0.01, ***P < 0.001). Z + D1 ZIKV + DENV-1-immune serum, Z + D2 ZIKV + DENV-2-immune serum, Z + D4 ZIKV + DENV-4-immune serum, Z + YF ZIKV + YFV-immune serum, Z + CH ZIKV + CHIKV-immune serum, Z + S− ZIKV + flavi- and alphavirus-naïve serum

ZIKV infection rates and ADE in different placental tissue explants

	Successfully infected explants										Relative risk (Fisher’s exact test)
	ZIKV	Z + S −	Z + CH	Z + YF	Z + D1	Z + D2	Z + D4	Z + C^1	Z + nD^2	Z + D^3	Z + D/ Z + C	Z + D/ Z + nD
Amnion	3/12 (25%)	4/12 (33%)	3/12 (25%)	1/12 (8%)	7/12 (58%)	6/12 (50%)	9/12 (75%)	7/24 (29%)	11/48 (23%)	22/36 (61%)	2.1 (0.0193)	2.67 (0.0006)
Decidua	6/12 (50%)	6/12 (50%)	9/12 (75%)	11/12 (92%)	12/12 (100%)	10/12 (83%)	12/12 (100%)	12/24 (50%)	32/48 (67%)	34/36 (94%)	1.89 (0.0001)	1.42 (0.0025)
Villus	5/12 (42%)	5/12 (42%)	11/12 (92%)	4/12 (33%)	12/12 (100%)	11/12 (92%)	11/12 (92%)	10/24 (42%)	25/48 (52%)	34/36 (94%)	2.27 ( < 0.0001)	1.81 ( < 0.0001)

¹Sum of ZIKV and Z + S −; ²Sum of all settings without DENV serum; ³Sum of all settings containing DENV sera. Z + D1 ZIKV + DENV-1-immune serum, Z + D2 ZIKV + DENV-2-immune serum, Z + D4 ZIKV + DENV-4-immune serum, Z + YF ZIKV + YFV-immune serum, Z + CH ZIKV + CHIKV-immune serum, Z + S − ZIKV + flavi- and alphavirus-naive serum.