(p-BthTX-I)2K inhibits CHIKV and ZIKVBR infection. (A) BHK-21 cells were incubated with (p-BthTX-I)2K at the MNTC (12.5 µM) or (B) at concentrations of 3.1, 6.3, 12.5, 25, and 50 µM, and infected with CHIKV-NLuc at an MOI of 0.1. CHIKV replication was analyzed via the measurement of the NLuc activity 16 h.p.i. Mean values ± standard deviations (SDs) were calculated with data obtained from a minimum of three independent experiments that were each performed in quadruplicate. (C) Vero cells were incubated with (p-BthTX-I)2K at 25 µM (the MCNT) or (D) at concentrations of 6.3, 12.5, 25, 50, and 100 µM and infected with ZIKVBR at an MOI of 0.1. The RNA levels of ZIKVBR in the cell culture supernatant 48 h.p.i. were quantified via qRT–PCR. Mean values ± SDs represent data from three independent experiments, each of which was performed in duplicate. * p ≤ 0.05; ** p ≤ 0.01; *** p ≤ 0.001; **** p ≤ 0.0001. VC: vehicle control (sterile water). A schematic representation of the respective experiment is shown above each graph.