Replication kinetics of TBEV/DEN4Δ30, its mutants, LGT, DEN4, or LGT/DEN4 in (A) simian Vero or (B) mosquito C6/36 cells infected at a multiplicity of infection of 1. Each time point represents the mean viral titer (±standard error) from three replicates. The significance of viral replication was defined as a difference of ≥15-fold in mean virus titer at the indicated time point. Asterisks indicate that the replication of DEN4 virus is significantly different from that of the TBEV/DEN4Δ30 mutants, LGT, or LGT/DEN4 viruses, whereas § indicates that LGT virus is significantly different in replication from all remaining viruses on the indicated days. The limit of detection was 2.0 log10 PFU/mL. DEN4, dengue 4; LGT, Langat; TBEV, tick-borne encephalitis virus.