Complete genomic sequence analysis of norovirus isolated from South Korea

The complete nucleotide and deduced amino acid sequences of the RNA genome of a recently isolated norovirus (NoV) from Korea, designated Hu/GII-4/CBNU2/2007/KR (CBNU2), were determined and characterized by phylogenetic comparison with several genetically diverse NoV sequences. The RNA genome of CBNU2 is 7,560 nucleotides in length, excluding the 3' poly (A) tract. It includes three open reading frames (ORFs): ORF1, which encodes the nonstructural polyprotein (5-5,104); ORF2, which encodes VP1 (5,085-6,707); and ORF3, which encodes VP2 (6,707-7,513). ORF2-based phylogenetic analysis revealed that CBNU2 belonged to the GII.4 genotype, the most prevalent genotype, and formed a cluster with NoVs isolated from Asian regions, between 2006 and 2008. Comparative analysis with the consensus sequence of 207 completely sequenced NoV genomes showed 47 mismatched nucleotides: 26 in ORF1, 14 in ORF2, and 7 in ORF3, resulting in 8 amino acid changes: 3 in ORF1, 2 in ORF2, and 3 in ORF3. Phylogenetic analysis with full genome ORF1, ORF2, and ORF3 nucleotide sequences obtained from CBNU2 and each of the other representative NoV genomes suggested that CBNU2 had not undergone recombination with any of the other NoVs. A SimPlot analysis further supported this finding.