Complete genome analysis of a novel norovirus GII.4 variant identified in China

The complete genome sequence of a novel norovirus strain GZ2010-L87 identified in Guangzhou was analyzed phylogenetically in this study. The RNA genome of the GZ2010-L87 strain is composed of 7,559 nucleotides. The phylogenetic analysis based on open reading frame (ORF) 2 revealed that the strain belongs to the GII.4 genotype, forming the new cluster GII.4-2009 which was also identified in Asia and the USA since 2009. Furthermore, phylogenetic analyses of the full genome and the different open reading frame sequences of GZ2010-L87 and other representative strains suggested that the novel strain did not undergo recombination. Comparative analysis with the consensus sequence of 31 completely sequenced norovirus GII.4-2009 genomes showed 86 mismatched nucleotides (56 in ORF1, 16 in ORF2, and 14 in ORF3), resulting in 19 amino acid changes (9 in ORF1, 3 in ORF2, and 7 in ORF3). Furthermore, 12 variable sites were found on the capsid protein of norovirus GII.4-2009, and most were located at the P2 domain. Meanwhile, based on comparison with other GII.4 clusters, 14 sites were shown specific to the novel cluster. In summary, the genome of the new GII.4-2009 variant GZ2010-L87, which was first identified in China, was extensively characterized with a large panel of genetically diverse noroviruses. The genomic information obtained from the novel variant can be used not only as a full-length norovirus sequence standard in China but also as reference data for future evolution research.