Fast type I interferon response protects astrocytes from flavivirus infection and virus-induced cytopathic effects

Lindqvist, Richard; Mundt, Filip; Gilthorpe, Jonathan D.; Wölfel, Silke; Gekara, Nelson O.; Kröger, Andrea; Överby, Anna K.

Comparison of the differently expressed genes among WT, IFNAR −/− astrocytes, supernatant or IFNαB/D-treated WT astrocytes showed an overlap of 112 transcripts, and these transcripts might be of particular importance as most Fig. 8 Type I IFN response in astrocytes protects against viral spread of TBEV and cell death. Primary astrocytes isolated from WT and IFNAR −/− mice were infected with TBEV MOI of 0.1 and viral growth was determined at indicated time points. Two hours before infection, cells were treated with anti-IFNAR antibody or control IgG (IgC). Number of infected cells were measured by immunofluorescent staining of TBEV E antigen and DAPI (a, n = 8). Quantification of virus RNA determined by qPCR analysis (b, n = 6). Viral titers in cell culture supernatants determined by focus forming assay (c, n = 6). Cell viability after infection was measured using a resazurine viability assay (d, n = 8). Supernatants from TBEV-infected astrocytes were collected at the indicated time points and inactivated. Primary neurons were pretreated with the supernatants followed by TBEV infection, and viral infection was determined 48 h post infection by immunofluorescent staining of TBEV E antigen and DAPI (e, n = 6). Mean values and standard deviations from three independent experiments are shown. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001 of them were downregulated in IFNAR −/− astrocytes, which were highly susceptible to TBEV infection, whereas they were upregulated in supernatant-and IFNαB/D-treated cells, which were resistant to the infection. Several antiviral ISGs were identified among the overlap such as viperin and TRIM79α, which have been identified as inhibitors of TBEV [50, 61] . ISG15, viperin, and Oas1b, which were found to be downregulated in IFNAR −/− astrocytes and upregulated after treatment with IFNαB/D and supernatant, have previously been identified as inhibitors of WNV and could thus contribute to antiviral response against WNV in astrocytes [19, 62, 80, 81] .