Whole-genome analysis of two bovine rotavirus C strains: Shintoku and Toyama

Rotavirus C (RVC) has been detected frequently in epidemic cases and/or outbreaks of diarrhoea in humans and animals worldwide. Because it is difficult to cultivate RVCs serially in cell culture, the sequence data available for RVCs are limited, despite their potential economical and epidemiological impact. Although whole-genome sequences of one porcine RVC and seven human RVC strains have been analysed, this has not yet been done for a bovine RVC strain. In the present study, we first determined the nucleotide sequences for five as-yet under-researched genes, including the NSP4 gene, from a cultivable bovine RVC, the Shintoku strain, identified in Hokkaido Prefecture, Japan, in 1991. In addition, we elucidated the ORF sequences of all segments from another bovine RVC, the Toyama strain, detected in Toyama Prefecture, Japan, in 2010, in order to investigate genetic divergence among bovine RVCs. Comparison of segmental nucleotide and deduced amino acid sequences among RVCs indicates high identity among bovine RVCs and low identity between human and porcine RVCs. Phylogenetic analysis of each gene showed that the two bovine RVCs belong to a cluster distinct from human and porcine RVCs. These data demonstrate that RVCs can be classified into different genotypes according to host species. Moreover, RVC NSP1, NSP2 and VP1 amino acid sequences contain a unique motif that is highly conserved among rotavirus A (RVA) strains and, hence, several proteins from bovine RVCs are suggested to play important roles that are similar to those of RVAs.