Figure 1: Inhibition of hRSV infection by CPM and jervine in vitro.

(a) Single dose inhibition of hRSV infection of HEp-2 cells by analogues of CPM tested at 3.5 μg/mL (cyclopamine: 8.5 μM, jervine: 8.2 μM, tomatidine: 7.7 μM, veratrine: 5.9 μM, veratridine: 5.2 μM, protoveratrine B: 4.3 μM, imperialine: 8.1 μM, veratramine: 8.5 μM). (b) Dose-dependent inhibition of hRSV replication in HEp-2 cells by CPM when present during viral adsorption stage, post-adsorption or at all stages of infection. Antiviral activities were measured by focus reduction assay. Foci numbers (adsorption stage) and sizes (post-adsorption and all stages) were measured automatically using the software FiJi⁵⁷, and were normalized as percentage of the untreated control. (c) Dose-dependent inhibition of hRSV replication in HEp-2 cells by CPM and jervine at post-adsorption stage, and cytotoxicity of CPM towards HEp-2 cells. All infections were carried out for 72 h. The cytotoxicity of CPM was measured over 72 h of incubation with cells, by cell viability assay. Each data point represents the mean of duplicate values, and the SEM is represented by the error bars. The graphs and the IC₅₀ and IC₉₅ values were created and calculated using the software GraphPad Prism v.5 (GraphPad Software, La Jolla California, USA), and are representative of 3 independent experiments.