Evolutionary Targeted Discovery of Influenza A Virus Replication Inhibitors
Influenza A is one of the most prevalent and significant viral infections worldwide, resulting in annual epidemics and occasional pandemics. Upon infection, antiviral drugs targeting the neuraminidase protein and M2 protein are the only treatment options available. However, the emergence of antiviral drug resistance is concerning, therefore the aim of this work was to identify inhibitor molecules that may bind to highly conserved regions of selected internal influenza A proteins. Sequences of the non-structural protein 1 (NS1), nuclear export protein (NEP) and polymerase basic protein 2 (PB2) from all hosts and subtypes were aligned and the degree of amino acid conservation was calculated based on Valdar’s scoring method. Missing parts of the experimental structures were predicted using the I-TASSER server and ligand binding hot spots were identified with computational solvent mapping. Selected binding sites in conserved regions were subjected to virtual screening against two compound libraries using AutoDock Vina and AutoDock 4. Two out of twelve top hit compounds predicted to target the NS1 protein showed capability of reducing influenza A H1N1 replication in plaque reduction assays at concentrations below 100 µM, although the target protein and mechanism of action could not be confirmed. For the NEP, conservation analysis was based on 3000 sequences and binding hot spots were located in common areas amongst three structures. Docking results revealed predicted binding affinities of up to -8.95 kcal/mol, and conserved amino acid residues interacting with top compounds include Arg42, Asp43, Lys39, Ile80, Gln101, Leu105, and Val109. For the PB2 protein, conservation analysis was based on ~12,000 sequences and fifteen potential binding hot spots were identified. Docking results revealed predicted binding affinities of up to -10.3 kcal/mol, with top molecules interacting with the highly conserved residues Gln138, Gly222, Ile539, Asn540, Gly541, Tyr531 and Thr530. The findings from this research could provide starting points for in vitro experiments, as well as the development of antiviral drugs that function to inhibit influenza A replication without leading to resistance.