Figure 4.

YFV cap1 2′O-Methyltransferase Prevents Immune Recognition

(A and B) Immune-competent A549 cells (A) or type I IFN gene-deficient Vero cells (B) were transfected with YFV replicon (YFVR) RNA or YFVR-E218A RNA-deficient for viral cap1 2′O-methyltransferase activity (see also Figure S4A). Replication was monitored by replicon-derived luciferase activity. Average of two experiments in technical duplicates is shown. Error bars indicate SD.

(C and D) A549 cells (C) or Vero cells (D) were infected with whole yellow fever virus particles YFV-WT or YFV-E218A (MOI 0.01). Virus production was quantified by plaque assay in BHK cells 24, 48, or 72 hr after infection. One representative of two experiments in technical duplicates is shown. Error bars indicate range.

(E) Wild-type, RIG-I-deficient (Ddx58^−/−), or STAT1-deficient A549 cells were infected with YFV-WT or YFV-E218A (MOI 0.01) and virus production was quantified as in (C) 72 hr after infection.

(F) Wild-type, RIG-I-deficient (Ddx58^−/−), or STAT1-deficient A549 cells were infected with YFV-WT or YFV-E218A (MOI 1) and IFIT1 mRNA was measured 8 hr after infection by RT-PCR.

(E and F) Average values of two experiments in technical duplicates are shown; error bars indicate SEM.

(G) Untransfected (no RIG-I, mock), RIG-I(WT)-, or RIG-I(H830A)-expressing HEK293^blue cells were transfected with YFVR-WT or YFVR(218) replicon RNA. The mean values of four experiments in technical duplicates is shown, error bars: SEM 100% = 895 ng/ml IP10 in average, linear range limit: 31 pg/ml.

(E–G) For statistics, two-way ANOVA and Bonferroni post-test were applied: ^∗∗p < 0.01, ^∗∗∗p < 0.001.