MAIN METHODS: A pull-down assay was performed to identify the binding partner of the L-SP40 peptide. Co-immunoprecipitation and co-localization assays with the L-SP40 peptide were employed to confirm the receptor partner in RD cells. The outcomes were validated using receptor knockdown and antibody blocking assays. The L-SP40 peptide was further evaluated for the protection of neonatal mice against lethal challenge by mouse-adapted EV-A71.
KEY FINDINGS: The L-SP40 peptide was found to interact and co-localize with nucleolin, the key attachment receptor of Enteroviruses A species, as demonstrated in the pull-down, co-immunoprecipitation and co-localization assays. Knockdown of nucleolin from RD cells led to a significant reduction of 3.5 logs of viral titer of EV-A71. The L-SP40 peptide demonstrated 80% protection of neonatal mice against lethal challenge by the mouse-adapted virus with a drastic reduction in the viral loads in the blood (~4.5 logs), skeletal muscles (1.5 logs) and brain stem (1.5 logs).
SIGNIFICANCE: L-SP40 peptide prevented severe hind limb paralysis and death in suckling mice and could serve as a potential broad-spectrum antiviral candidate to be further evaluated for safety and potency in future clinical trials against EV-A71.
METHODS: In our study we used structural-based drug designing, molecular simulation, and binding free energy approaches to identify the potent phytocompounds from various natural product databases (>100,000 compounds) able to inhibit the binding of NS1 with the TRIM25.
RESULTS: The molecular screening identified EA-8411902 and EA-19951545 from East African Natural Products Database, NA-390261 and NA-71 from North African Natural Products Database, SA-65230 and SA- 4477104 from South African Natural Compounds Database, NEA- 361 and NEA- 4524784 from North-East African Natural Products Database, TCM-4444713 and TCM-6056 from Traditional Chinese Medicines Database as top hits. The molecular docking and binding free energies results revealed that these compounds have high affinity with the specific active site residues (Leu95, Ser99, and Tyr89) involved in the interaction with TRIM25. Additionally, analysis of structural dynamics, binding free energy, and dissociation constants demonstrates a notably stronger binding affinity of these compounds with the NS1 protein. Moreover, all selected compounds exhibit exceptional ADMET properties, including high water solubility, gastrointestinal absorption, and an absence of hepatotoxicity, while adhering to Lipinski's rule.
CONCLUSION: Our molecular simulation findings highlight that the identified compounds demonstrate high affinity for specific active site residues involved in the NS1-TRIM25 interaction, exhibit exceptional ADMET properties, and adhere to drug-likeness criteria, thus presenting promising candidates for further development as antiviral agents against influenza A virus infections.
RESULTS: Using in silico methods, we studied the predicted interactions between bromelain and key proteins involved in NPC oncogenesis, specifically β-catenin, PIK3CA, mTOR, EGFR, and BCL2. Molecular docking strategies were performed using a myriad of computational tools. A 3D model of bromelain was constructed using SWISS-MODEL, followed by molecular docking simulations performed with ClusPro. The binding affinities of the docked complexes were evaluated using HawkDock, and the interactions were analysed with LigPlot+. The docking scores indicated potential spontaneous interactions, with binding affinities based on being - 103.89 kcal/mol (PIK3CA), -73.16 kcal/mol (EGFR), -71.18 kcal/mol (mTOR), -65.22 kcal/mol (β-catenin), and - 57.48 kcal/mol (BCL2). LigPlot + analysis revealed the presence of hydrogen bonds, hydrophobic interactions, and salt bridges, indicating stable predicted interactions.
CONCLUSION: Our findings suggest that bromelain can target key proteins involved in NPC oncogenesis, with the strongest affinity towards PIK3CA. This suggests a hypothetical insight into bromelain's anticancer effects on NPC through the modulation of the PI3K/Akt signaling pathway.