Source of oseltamivir resistance due to single E276D, R292K, and double E276D/R292K mutations in H10N4 influenza neuraminidase

Influenza is a respiratory contagious disease infecting people all around the globe. The Center for Disease Control and Prevention had estimated that from 1 October 2018 to 4 May 2019, there have been about 40 million flu patients, in which about 50 thousand cases have died. Many subtypes of influenza have developed drug resistance due to high mutation rates. Neuraminidase (NA) is the glycoprotein on the virus particle surface. Its function is to cleave the glycosidic bond with the sialic acid, leading the new virus to be able to infect other uninfected cells. Therefore, it is a promising protein target for drug design and development. The E276D and R292K NA mutations in the H10N4 influenza virus have been reported to cause drug resistance. In this study, molecular dynamics simulations and free energy calculations were applied to study the source of oseltamivir resistance in E276D, R292K, and E276D/R292K NA strains. The obtained results suggested that all studied mutants reduced the number of contact atoms, interaction energies, H-bonds, per-residue interaction energies, and total binding free energies towards the oseltamivir binding, resulting in a lower susceptibility. Only the interactions at residues 118, 119, and 371 were maintained in stabilizing the oseltamivir. The opening at 150- and 430-loops in E276D and double mutations caused the drug unbinding from the active site, increasing water accessibility into the binding pocket of NA enzyme.