title: Genetic microheterogeneity of emerging H275Y influenza virus A (H1N1) in Toronto, Ontario, Canada from the 2007-2008 respiratory season.
abstract: BACKGROUND
  The H275Y mutation (H274Y in N2 numbering) in the neuraminidase (NA) gene (segment 6) of the influenza virus A (H1N1) genome is linked to oseltamivir resistance.
  
  
  OBJECTIVE
  To determine the percentage of influenza virus A (H1N1) isolates that carry the H275Y mutation in the NA gene in Toronto, Ontario, Canada and to characterize select oseltamivir resistant and susceptible isolates using sequence analysis.
  
  
  METHODS
  Sanger sequencing was used to determine strain type and H275Y mutations based on partial sequencing of the hemagglutinin (HA) (segment 4) and NA genes. Mutations in the NS1 gene (segment 8) were determined by Sanger sequencing and pyrosequencing. Statistical analysis of demographics and proportions of H275 and H275Y isolates with mutations was carried out using chi(2) analyses.
  
  
  RESULTS
  The HA gene of influenza virus A (H1N1) isolates collected during the 2007-2008 respiratory season was most like influenza A/Brisbane/59/2007, Clade 2, subclade B. Seventeen percent of these isolates possessed the H275Y NA mutation associated with oseltamivir resistance. H275Y isolates were more likely than H275 isolates to have the mutations A209T and R224G in NS1 (chi(2)=284.9, df=2, p<0.0001).
  
  
  CONCLUSIONS
  During the 2007-2008 influenza season in Toronto, Ontario, Canada, 17% of influenza virus A (H1N1) isolates carried the H275Y mutation associated with oseltamivir resistance. These H275Y isolates were more likely than H275 isolates to exhibit unique microheterogeneity in the gene encoding the NS1 protein.
authors.affiliation: Ontario Public Health Laboratories, 81 Resources Road, Toronto, Ontario, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Eshaghi
authors.forename: S
authors.initials: S
authors.lastname: Bolotin
authors.forename: L
authors.initials: L
authors.lastname: Burton
authors.forename: D E
authors.initials: DE
authors.lastname: Low
authors.forename: T
authors.initials: T
authors.lastname: Mazzulli
authors.forename: S J
authors.initials: SJ
authors.lastname: Drews
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019943:Amino Acid Substitution / Q000235:genetics; D000998:Antiviral Agents / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D024882:Drug Resistance, Viral; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics* / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009439:Neuraminidase / Q000235:genetics*; D009864:Ontario / Q000453:epidemiology; D053139:Oseltamivir / Q000494:pharmacology; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D014764:Viral Proteins / Q000235:genetics*; D055815:Young Adult
chemical_list: D000998:Antiviral Agents; D014764:Viral Proteins; D053139:Oseltamivir; C487630:NA protein, influenza A virus; D009439:Neuraminidase