Species specificity and interspecies relatedness of NSP4 genetic groups by comparative NSP4 sequence analyses of animal rotaviruses

Previous sequence analyses of the rotavirus nonstructural NSP4 from human and some animal rotavirus strains revealed the presence of three distinct NSP4 alleles or genetic groups. To examine the species of origin relatedness and diversity of NSP4, the nucleotide and deduced amino acid sequences of the gene encoding the NSP4 from 15 animal rotavirus strains of porcine, equine, bovine, lapine and canine origin were determined and compared to human and other animal strains sequenced previously. Lapine and equine strains were shown to belong to the NSP4 genotype A. Murine NSP4 sequences formed a previously unrecognized fourth distinct NSP4 genotype (genotype D) that was more divergent compared to NSP4 genotype A, B, and C than the latter three are among each other. Within NSP4 genotypes, strains isolated from rabbits, horses, cows (genotype A) and pigs (genotype B) clustered according to species of origin, suggesting a conserved pattern of evolution within species. NSP4 sequence comparison among one wildtype and two tissue culture-adapted lapine strains, known to cause disease in neonatal rabbits, failed to identify amino acid changes within the variable region spanning amino acids 130 to 141, suggesting that disease in rabbits is the result of the lapine virus infection and replication, including production of the NSP4 enterotoxin.