title: The significance of naturally occurring neuraminidase quasispecies of H5N1 avian influenza virus on resistance to oseltamivir: a point of concern.
abstract: Viral adaptability and survival arise due to the presence of quasispecies populations that are able to escape the immune response or produce drug-resistant variants. However, the presence of H5N1 virus with natural mutations acquired without any drug selection pressure poses a great threat. Cloacal samples collected from the 2004-2005 epidemics in Thailand from Asian open-billed storks revealed one major and several minor quasispecies populations with mutations on the oseltamivir (OTV)-binding site of the neuraminidase gene (NA) without prior exposure to a drug. Therefore, this study investigated the binding between the NA-containing novel mutations and OTV drug using molecular dynamic simulations and plaque inhibition assay. The results revealed that the mutant populations, S236F mutant, S236F/C278Y mutant, A250V/V266A/P271H/G285S mutant and C278Y mutant, had a lower binding affinity with OTV as compared with the WT virus due to rearrangement of amino acid residues and increased flexibility in the 150-loop. This result was further emphasized through the IC50 values obtained for the major population and WT virus, 104.74 nM and 18.30 nM, respectively. Taken together, these data suggest that H5N1 viruses isolated from wild birds have already acquired OTV-resistant point mutations without any exposure to a drug.
authors.affiliation: Department of Microbiology, Faculty of Science, Mahidol University, 272 Rama 6 Road, Ratchatewi, Bangkok 10400, Thailand.
authors.forename: Nalini
authors.initials: N
authors.lastname: Schaduangrat
authors.affiliation: Computational Chemistry Unit Cell, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Jiraphorn
authors.initials: J
authors.lastname: Phanich
authors.affiliation: Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.|Program in Bioinformatics and Computational Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Thanyada
authors.initials: T
authors.lastname: Rungrotmongkol
authors.affiliation: Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Hatairat
authors.initials: H
authors.lastname: Lerdsamran
authors.affiliation: Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Pilaipan
authors.initials: P
authors.lastname: Puthavathana
authors.affiliation: Department of Microbiology, Faculty of Science, Mahidol University, 272 Rama 6 Road, Ratchatewi, Bangkok 10400, Thailand.
authors.forename: Sukathida
authors.initials: S
authors.lastname: Ubol
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D001717:Birds; D024882:Drug Resistance, Viral; D014644:Genetic Variation; D053124:Influenza A Virus, H5N1 Subtype / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D005585:Influenza in Birds / Q000821:virology*; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D056004:Molecular Dynamics Simulation; D050505:Mutant Proteins / Q000235:genetics* / Q000378:metabolism; D009439:Neuraminidase / Q000235:genetics* / Q000378:metabolism; D053139:Oseltamivir / Q000494:pharmacology*; D011485:Protein Binding; D013785:Thailand; D010948:Viral Plaque Assay; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D000998:Antiviral Agents; D050505:Mutant Proteins; D014764:Viral Proteins; D053139:Oseltamivir; C487630:NA protein, influenza A virus; D009439:Neuraminidase