title: Genetic characterisation of influenza B viruses detected in Singapore, 2004 to 2009.
abstract: BACKGROUND
  Influenza B viruses are classified into two main lineages: Yamagata-like and Victoria-like, which differ antigenically and phylogenetically. To understand the evolution of influenza B viruses in South East Asia as well as to determine the vaccine efficacy, we genetically characterised gene segments 4, 6 and 8 from non-tissue culture adapted influenza B viruses detected in Singapore from 2004 to 2009.
  
  
  METHODS
  vRNA were extracted from the nasopharyngeal swabs or nasal washes of SAF servicemen displaying febrile and respiratory symptoms, and subjected to PCR assay to test for the presence of influenza B virus. The PCR-positive specimens were next subjected to sequencing of the full gene segments 4 (HA), 6 (NA/NB) and 8 (NS1/NEP). The nucleotide sequences were aligned together with that of other specimens isolated from South East Asia as well as the vaccine strains. Phylogenetic trees of each gene segment were constructed and the amino acid alignments were analysed.
  
  
  RESULTS
  A majority of the Singaporean specimens analysed in this study, from 2004-2009, had gene segment 4 from the Victoria-like lineage and gene segment 6 from Yamagata-like lineage. Some of these specimens had both gene segments from the Yamagata lineage and this resulted in several vaccine mismatches. Gene segment 8 from majority of these specimens clustered separately from both the Yamagata and Victoria strains. The HA protein of most of the Singaporean specimens isolated post 2000 contained a glycosylation site at position 211, which was not dominant prior to 2000. No amino acid substitution conferring drug-resistance was found in either the HA or NA proteins.
  
  
  CONCLUSIONS
  The presence of both lineages co-circulating post 2000, suggests that a trivalent vaccine is not enough to confer immunity to the general public, strongly endorsing the inclusion of both lineages in the vaccine. Several amino acid substitutions were observed, prompting in depth functional analyses.
authors.forename: Muhammad Raihan
authors.initials: MR
authors.lastname: Jumat
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Sugrue
authors.affiliation: Detection and Diagnostics Laboratory, Defence Medical and Environmental Institute, DSO National Laboratories, 27 Medical Drive, Singapore 117510, Republic of Singapore. ephtbh@nus.edu.sg.
authors.forename: Boon-Huan
authors.initials: BH
authors.lastname: Tan
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D005814:Genes, Viral; D006801:Humans; D009981:Influenza B virus / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012846:Singapore; D014764:Viral Proteins / Q000737:chemistry
chemical_list: D014764:Viral Proteins