Figure 1

In vitro characterization of wt and ΔF2. A The mutation (C138A) introduced a stop codon to the PB1-F2 reading frame, while the PB1 frame remains intact. B HEK293T cells were transfected with plasmids of the polymerase complex (PB1, PB2, PA, NP) as well as Nanoluciferase and Firefly Luciferase (as transfection control). 48 hpi luminescence of lysed cells was analysed and normalized against transfection control. The data is shown as mean (SD), control (white), wt (blue), ΔF2 (red), statistical analysis was done by One-Way ANOVA with Tukey’s multiple comparisons test. The data is representative of one of three separate experiments. C Viral replication kinetics were performed using chicken fibroblasts (DF-1), chicken embryo kidney cells (CEK) and Madin-Darby canine kidney cells (MDCK-II). Cells were infected at a multiplicity of infection (MOI) of 0.001, collected and titrated by Plaque test. Pooled data from three separate experiments is depicted as mean (SD), statistics are calculated by two-way ANOVA. D To assess cell-to-cell spread at least 50 PFU per virus were measured. Results are depicted as mean (SD), statistical analysis was performed using the Mann Whitney test (p < 0.0001).