Antiviral Activity of Quercetin Hydrate against Zika Virus

Abstract

Zika virus (ZIKV) has re-emerged in recent decades, leading to outbreaks of Zika fever in Africa, Asia, and Central and South America. Despite its drastic re-emergence and clinical impact, no vaccines or antiviral compounds are available to prevent or control ZIKV infection. This study evaluated the potential antiviral activity of quercetin hydrate against ZIKV infection and demonstrated that this substance inhibits virus particle production in A549 and Vero cells under different treatment conditions. In vitro antiviral activity was long-lasting (still observed 72 h post-infection), suggesting that quercetin hydrate affects multiple rounds of ZIKV replication. Molecular docking indicates that quercetin hydrate can efficiently interact with the specific allosteric binding site cavity of the NS2B-NS3 proteases and NS1-dimer. These results identify quercetin as a potential compound to combat ZIKV infection in vitro.

Keywords: Zika virus; antiviral activity; in silico analysis; inhibition; natural products.

Figure 1

Quercetin hydrate causes dose-dependent inhibition of ZIKV yields. Vero cells were treated with DMSO solvent control or 1000–15.625 μM of quercetin hydrate in indicated conditions prior to infection with ZIKV at MOI = 0.1. The supernatant was titrated at 48 h post-infection. Mean values with standard deviation from three independent experiments, measured in triplicate, are shown. (*, p < 0.05/**, p < 0.01).

Figure 2

Growth curves of ZIKV (MOI = 0.1) in A549 or Vero cells in the presence of 0.5% DMSO or 125 µM quercetin hydrate, showing impaired ZIKV progeny production after treatment with quercetin hydrate when applied in the (A) virucidal assay, (B) pre-treatment assay, (C) co-treatment assay, and (D) post-treatment assay. (*, p < 0.05/****, p < 0.0001/ ns, not significant).

Figure 3

Evaluation of antiviral effect by indirect immunofluorescence assay (IFA). ZIKV was cultured at MOI = 1 in A549 or Vero cells with 125 μM quercetin hydrate. Non-infected cells and ZIKV-infected cells without compound were used as controls. After 12 h of incubation with the treatments, cells were fixed, and the expression of ZIKV E protein (in green) was detected with anti-E protein 4G2 mouse primary antibodies, followed by Alexa Fluor 488 mouse secondary antibody. Cell nuclei were stained with DAPI (in blue).

Figure 4

Structures selected for quercetin hydrate docking in the NS1 protein are represented as a ribbon and a surface for cavity visualization. The cavity comprising the ß-roll is demarcated in the black dashed lines.

Figure 5

Binding mode of MI-2227 (A) and quercetin hydrate (B). Right panel: NS2B-NS3 is represented as a surface, while the ligands are shown as green (MI-2227) and gray (quercetin hydrate) stick structures. The NS2B and NS3 chains are presented as pink and orange, respectively. Center panel: protein is shown as a transparent ribbon, and residues interacting with the ligand are represented as stick structures. Left panel: 2D diagram of protein/ligand interaction. Residues that are part of the catalytic triad are marked with *.

Figure 6

Best docking poses of quercetin hydrate in NS1 protein replicates. The ADV score for replicate 1 (A) was −6.985 kcal/mol, for replicate 3 (B) was −6.899 kcal/mol, and for replicate 5 (C) was −8.347 kcal/mol. The protein is represented as a surface (left panel) and stick structure (middle panel), and quercetin hydrate is represented as a gray ball and stick structure. Oxygen and nitrogen atoms are shown in blue and red, respectively.