Capsid protein diversity among Norwalk-like viruses

We have determined the complete capsid gene sequence of 20 Norwalk-like vir uses (NLVs) collected predominantly from outbreaks in the UK between 1989 a nd 1996. These comprised nine genogroup I and eleven genogroup II strains. Phylogenetic analysis of these and 15 published sequences suggest seven gen omic sub-groups within genogroup I, including three previously described. I n genogroup II, eight sub-groups were apparent, of which four were novel. A mino acid identities between strains of distinct genogroups ranged from 37 to 44% while varying between 61 and 100% for strains within a genogroup. Se parate phylogenetic analyses of the N-terminus and central variable region of the capsid showed good correlation. Sequence divergence between strains was greatest within the central variable region, with amino acid sequence i dentities as low as 28% within a genogroup. These 15 genomic sub-groups pro vide a framework for further investigations of genetic and antigenic relati onships within this calicivirus clade.