Figure 1.

The molecular formula of erythromycin estolate (Ery-Est) and Ery and their inhibitory activity against Zika virus (ZIKV) in different cell types. (A) The molecular formula of Ery-Est and Ery. (B) BHK21 cells (2 × 10⁶) were infected by ZIKV strain SZ01 that were treated with serial concentrations of Ery-Est and Ery, the infected cells were then covered with an overlay of Dulbecco’s modified Eagle’s medium (DMEM) containing 2% fetal bovine serum (FBS) and 1% low meliting-point (LMP) agarose. After incubation for about 5 days, infected cells were stained with 1% crystal violet for plaque visualization and (C) the inhibitions of infection were calculated. The experiment was tested in triplicate and data are represented as means ± SD. (D) U-251 MG cells (2 × 10⁵) were infected by ZIKV treated with different concentrations of Ery-Est and Ery. The percentage of infected cells at 48 h post infection was determined by flow cytometry and normalized to untreated infected cells and the inhibitory percentages were calculated. The experiment was tested in triplicate and data are represented as means ± SD. (E) BHK21 and Vero cells (2 × 10⁵) were infected with ZIKV strain SZ01 and treated by Ery-Est and Ery, then the ZIKV infection was evaluated by immunofluorescence staining after 4 days. ZIKV E protein were stained by mAb 4G2 (green); nuclei were stained by 4,6-diamidino-2-phenylindole (blue), scale bar: 50 µm. Each experiment was repeated at least twice and similar results were obtained. Statistical analysis: Two-way ANOVA with Sidak’s multiple comparisons for (C) and (D). * p < 0.05; **** p < 0.0001.