Sequence analysis of two porcine rotaviruses differing in growth in vitro and in pathogenicity: distinct VP4 sequences and conservation of NS53, VP6 and VP7 genes

The VP4, VP7, NS53 and VP6 genes of two porcine rotavirus variants which differ in their in vitro growth properties and pathogenicity have been cloned and sequenced. The VP4 genes show only 67.2% nucleic acid and 70.6% amino acid identity. The VP4 gene of one variant (4S) is closely related to that of the bovine UK rotavirus strain, whereas the VP4 gene of the other variant (4F) is only distantly related to known VP4 genes and is likely to represent a new P serotype. In contrast the NS53 (VP5), VP6 and VP7 genes of the 4F and 4S variants show greater than 99% nucleotide and amino acid identity, indicating that the two viruses are genetically related by a reassortment event. The implications for the role of VP4 in the determination of in vitro growth characteristics and pathogenicity are discussed.