Fig. 5

Type I IFNs present in conditioned medium from ZIKV-infected neurons activate non-infected microglial cells. ZIKV does not infect primary cultured microglial cells as determined by a immunofluorescence of MEFs and microglial cells from B6 mice exposed ZIKV at a MOI of 5 and labeled 24 h p.i. with an anti-NS2B antibody (red) along with staining of filamentous actin (F-actin) with phalloidin (green). Scale bars = 10 µm. Conditioned medium from ZIKV-infected PCNs induced the activation of the expression level of genes coding for IFNB (Ifnb1), ISGs (Irf7, Isg15, Eif2ak2) and factors associated with the pro-inflammatory “on” state of microglia cells (Cxcl10, Tnf, Il1b, Ccl2, Ccl5, C3, C4) through IFNs-I signaling. b–e Primary cultured microglial cells from B6 mice were treated with conditioned media recovered at 64 h p.i. from n = 3 B6 PCNs either non-infected (CM_NI) or ZIKV-infected (CM_ZIKV) as in Fig. 1, in the presence or absence of anti-IFNAR antibodies (α-IFNAR). As a control, microglial cells were treated with the same amount of ZIKV as the one present in CM_ZIKV. Results correspond to those obtained from three independent primary culture of microglia (with symbols corresponding to each independent culture shown in different colors) each one treated with CM from one of the three independent PCNs. RNA levels were determined by RT-qPCR with respect to Rplp0 used as reference gene. The levels of ZIKV and IFNB RNA present in the three ZIKV-infected PCNs from which the CMs used here were collected (grey bars) are shown in d and e respectively. Bars represent means without s.d. with significance assessed by ratio paired t-test. P-value < 0.01 (**), < 0.05 (*) and ns not significant; p-values near significance are indicated