Fig. 1: LDL-R is a cofactor of CCHFV infectivity.

a WT CCHFV, manipulated in BSL4, was produced in Huh-7.5 cells, whereas CCHF tecVLPs were produced in Huh-7.5 or HEK-293T cells. Infection or transduction assays were performed with serial dilutions. The level of infection was determined by RNA measurement in infected cells lysates. For tecVLP-GFP, target cells were pre-transfected with CCHFV NP and L expression vectors to amplify the GFP signal by minigenome replication and the level of transduction was assessed by flow cytometry. For tecVLP-NanoLuc, the level of transduction was assessed by measurement of nanoLuc levels. Created with Biorender.com. b Western blot analysis of cell lysates from Huh-7.5 cells transduced with lentiviral vectors allowing expression of control shRNA or shRNA targeting Lrp1 or LDL-R or SR-B1 (top). Representative image of 3 experiments. Quantification of the abundance of corresponding receptors (bottom). c Cells described in (b) were transduced with CCHF tecVLP-NanoLuc. Independent experiments: N = 5 SR-BI; N = 6 Lrp1; N = 7 LDL-R. Kruskal-Wallis test with Dunn’s multiple comparisons (ctrl vs. Lrp1: p = 0.0278, ctrl vs. LDL-R: p = 0.0498, ctrl vs. SR-BI: p > 0.9999). d Huh-7.5 cells were incubated with different concentration of LDL-R antibody (open bars) or control isotype (IgG goat, dashed bars) for 1 h at 37 °C before transduction with CCHF tecVLP-GFP (pink), MLVpp (green), and VSVpp (yellow) or infection with HAZV (blue). Independent experiments: N = 3 MLVpp; N = 5 CCHFV tecVLPs and VSVpp; N = 4 HAZV (0.25μg/mL and 4μg/mL) and N = 2 HAZV (1μg/mL). Two-way ANOVA test with Sidak’s multiple comparisons (αLDL-R vs. IgG: CCHF tecVLPs, 0.25μg/mL p = 0.0091, 1μg/mL p < 0.0001, 4μg/mL p < 0.0001; HAZV, 0.25μg/mL p > 0.9999, 1μg/mL p = 0.8951, 4μg/mL p > 0.9999; MLVpp, 0.25μg/mL p > 0.9999, 1μg/mL p = 0.8343, 4μg/mL p > 0.9999; VSVpp, 0.25μg/mL p = 0.0028, 1μg/mL p < 0.0001, 4μg/mL p < 0.0001). e Same experiment using WT CCHFV. N = 4 (1μg/mL) or N = 5 (4μg/mL) independent experiments. Two-way ANOVA test with Sidak’s multiple comparisons (αLDL-R vs. IgG: 1μg/mL p = 0.0042, 4μg/mL p = 0.0004). f Huh-7.5 cells stably expressing FLuc cells were transduced with a lentiviral vector allowing expression of VLDL-R. Surface expression of VLDL-R assessed by flow cytometry (left). Cells were then transduced with CCHF tecVLP-NanoLuc. N = 6 independent experiments. One sample t-test (two-tailed) p = 0.0467. Data are represented as means ± SEM.