Discovery of Quercetin as a Potential Entry Inhibitor of Nipah Virus: A Path Toward Antiviral Therapy.

Nipah virus (NiV) is a zoonotic virus that causes severe encephalitis and respiratory disease with a mortality rate often exceeding 70%. Currently, there are no licensed vaccines or therapeutics for NiV disease. This study aimed to identify and experimentally evaluate small-molecule inhibitors targeting the NiV-G (attachment) glycoprotein using integrated in silico and in vitro approaches. A high-throughput virtual screening of >215,000 compounds was conducted against the NiV-G glycoprotein, using docking and molecular dynamics (MD) simulations. The next potential candidates were evaluated using an established, BSL-2-compatible recombinant Cedar virus (rCedV)-based green fluorescent protein (GFP) reporter virus expressing the NiV-F (fusion) and G glycoproteins (rCedV-NiV-B-GFP). During MD simulations, quercetin demonstrated the most stable binding, maintaining a consistent RMSD (3.25 ± 0.3 Å). In vitro testing showed dose-dependent inhibition of rCedV-NiV-B-GFP infection. Although quercetin alone was less potent (IC50 = 24 µM; 95% CI: 7.6-93.6 µM) than a reference NiV-neutralizing monoclonal antibody mAb-7B7 (IC50 = 0.027 μg/mL; approximately 0.00018 μM; 95% CI: 0.0108 to 0.0735), combination with ascorbic acid enhanced neutralization (IC50 = 4.4 µM; 95% CI: 2.9-6.8 µM). Quercetin demonstrated a high Selectivity Index of >20.8. The study identifies quercetin as a promising small-molecule inhibitor of NiV cellular infection, potentially through a stable interaction with NiV-G at the ephrin-B2/B3 binding interface identified computationally. These findings highlight the importance of combining computational screening with BSL-2 cell-based bioassays to accelerate NiV countermeasure discovery.