title: Reduced susceptibility to all neuraminidase inhibitors of influenza H1N1 viruses with haemagglutinin mutations and mutations in non-conserved residues of the neuraminidase.
abstract: OBJECTIVE
  We characterized human H1N1 influenza isolate A/Hokkaido/15/02, which has haemagglutinin and neuraminidase mutations that reduce drug susceptibility to oseltamivir, zanamivir and peramivir.
  
  
  METHODS
  One wild-type and three mutant viruses were isolated by plaque purification. Viruses were tested in MUNANA-based enzyme assays, cell culture and receptor binding assays.
  
  
  RESULTS
  Two viruses had a neuraminidase Y155H mutation that reduced susceptibility in the enzyme inhibition assay to all inhibitors by 30-fold to >100-fold. The Y155H mutation reduced plaque size and affected the stability, Km and pH activity profile of the enzyme. In contrast to previous mutants, this neuraminidase demonstrated a slower rate of inhibitor binding in the IC50 kinetics assay. One virus had both the Y155H mutation and a haemagglutinin D225G mutation that rescued the small-plaque phenotype of the Y155H virus and affected receptor binding and drug susceptibility in cell culture and binding assays. We also isolated a third mutant virus, with both neuraminidase V114I and haemagglutinin D225N mutations, which affected susceptibility in the enzyme inhibition assay and receptor binding, respectively, but to lesser extents than the Y155H and D225G mutations.
  
  
  CONCLUSIONS
  Neither Y155 nor V114 is conserved across neuraminidase subtypes. Furthermore, Y155 is not conserved even among avian and swine N1 viruses. Structurally, both residues reside far from the neuraminidase active site. D225 forms part of the receptor binding site of the haemagglutinin. We believe this is the first demonstration of a specific haemagglutinin mutation correlating with reduced drug susceptibility in plaque assays in both Madin Darby Canine Kidney and SIAT cells.
authors.affiliation: CSIRO Materials Science and Engineering, 343 Royal Parade Parkville, 3052 Australia.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: McKimm-Breschkin
authors.forename: Janelle
authors.initials: J
authors.lastname: Williams
authors.forename: Susan
authors.initials: S
authors.lastname: Barrett
authors.forename: Kim
authors.initials: K
authors.lastname: Jachno
authors.forename: Mandy
authors.initials: M
authors.lastname: McDonald
authors.forename: Peter G
authors.initials: PG
authors.lastname: Mohr
authors.forename: Takehiko
authors.initials: T
authors.lastname: Saito
authors.forename: Masato
authors.initials: M
authors.lastname: Tashiro
mesh_terms: D000146:Acids, Carbocyclic; D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D002460:Cell Line; D003517:Cyclopentanes / Q000494:pharmacology; D004252:DNA Mutational Analysis; D024882:Drug Resistance, Viral; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D020125:Mutation, Missense; D009439:Neuraminidase / Q000235:genetics*; D053139:Oseltamivir / Q000494:pharmacology; D014764:Viral Proteins / Q000235:genetics*; D053243:Zanamivir / Q000494:pharmacology
chemical_list: D000146:Acids, Carbocyclic; D000998:Antiviral Agents; D003517:Cyclopentanes; D004791:Enzyme Inhibitors; D006146:Guanidines; D014764:Viral Proteins; D053139:Oseltamivir; C487630:NA protein, influenza A virus; D009439:Neuraminidase; D053243:Zanamivir; C414210:peramivir
keywords: oseltamivir; peramivir; zanamivir