title: Molecular evolution of GII-4 Norovirus strains.
abstract: BACKGROUND
  Human Noroviruses (NoV) are the major cause of acute nonbacterial gastroenteritis and the leading cause of outbreaks of gastroenteritis worldwide. Genotype II-4 (GII-4) NoV has been shown to spread rapidly and is the most commonly detected strain worldwide, particularly in association with outbreaks. Previously, we have shown that circulating GII-4 NoV strains exist as populations of selectively neutral variants, and that the emergence of epidemic GII-4 NoV strains correlated with mutations in at least two key sites (Sites A and B) within the P2 domain of the surface exposed major capsid protein (VP1).
  
  
  METHODS
  We developed a rapid pyrosequencing method for screening of the two Sites A and B and a homology based modelling system was used to predict the effects of amino acid substitutions at these sites on the antigenic properties of the virus (defined as surface motif types).
  Here, we describe the characterisation of amino acid diversity at Sites A and B for 1062 GII-4 NoV strains from clinical specimen associated with outbreak of gastroenteritis (2000-2011) and 250 GII-4 NoV sequences from Genbank. Our data identified a high diversity of different Site A and B site combinations at amino acid level and amino acid diversity was higher at Site B than Site A. Site A motifs could be grouped into 3 clusters based on similar surface motif types. We predict that Site A is a major epitope on the virus surface, responsible for defining the antigenic profile, and a more subtle role for Site B, maintaining minor antigenic variation within the virus population.
authors: Virus Reference Department, Health Protection Agency Microbiology Services, London, United Kingdom.
authors: Katherina
authors: K
authors: Zakikhany
authors: David J
authors: DJ
authors: Allen
authors: David
authors: D
authors: Brown
authors: Miren
authors: M
authors: Iturriza-Gómara
mesh_terms: D019943:Amino Acid Substitution; D000956:Antigens, Viral / Q000276:immunology; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D014644:Genetic Variation; D006801:Humans; D029322:Norovirus / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid
chemical_list: D000956:Antigens, Viral; D036022:Capsid Proteins