VP6 genetic diversity, reassortment, intragenic recombination and classification of rotavirus B in American and Japanese pigs.

Rotavirus B (RVB) has been identified as a causative agent of diarrhea in rats, humans, cattle, lambs, and swine. Recently, 20 RVB VP7 genotypes were determined based on an 80% nucleotide percent cut-off value. In this study, we sequenced the RVB VP6 gene segment from 80 RVB positive swine samples from the United States and Japan. Phylogenetic analyses, using the 30 available RVB VP6 sequences from GenBank and our 80 novel RVB VP6 sequences, revealed a large genetic diversity of RVB strains, mainly in pigs. For classification purposes, pairwise identity frequency analyses suggested an 81% nucleotide percent cut-off value, resulting in 13 RVB VP6 (I) genotypes. In addition, an intragenic recombinant RVB VP6 segment was identified from Japan. Furthermore, the data indicates frequent reassortment events occurred between the porcine RVB VP7 and VP6 gene segments.