The Bovine Newbury Agent-2 Is Genetically More Closely Related to Human SRSVs Than to Animal Caliciviruses

Abstract

The hypothesis that the enteric bovine calici-like virus Newbury agent (NA-2) belongs to the familyCaliciviridaewas examined by genome sequence analysis. Use of solid-phase immune electron microscopy allowed samples with good levels of virus to be identified and amplification of the genome was achieved by reverse transcription–polymerase chain reaction. Examination of a 216-amino-acid sequence in the RNA-dependent RNA polymerase gene and a 116-amino-acid sequence in the capsid gene showed that NA-2 had the closest deduced amino acid identity (77 to 80% for the polymerase region and 67 to 73% for the capsid region) to the morphologically indistinguishable human SRSVs (small round structured viruses) of genogroup 1, which are classified as members of theCaliciviridae.It had a weak relationship (<34.5% deduced amino acid identity) in both the polymerase and the capsid regions to animal caliciviruses, all of which have classical morphology. This is the first genomic data from a nonhuman virus with SRSV morphology. It confirms the hypothesis that the bovine enteric calici-like virus NA-2 is a member of the familyCaliciviridaeand endorses the observation to date that viruses with SRSV morphology are genomically distinct.