The bovine Newbury agent-2 is genetically more closely related to human SRSVs than to animal caliciviruses

The hypothesis that the enteric bovine calici-like virus Newbury agent (NA- 2) belongs to the family Caliciviridae was examined by genome sequence anal ysis. Use of solid phase immune electron microscopy allowed samples with go od levels of virus to be identified and amplification of the genome was ach ieved 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 ded uced amino acid identity (77 to 80% for the polymerase region and 67 to 73% for the capsid region) to the morphologically indistinguishable human SRSV s (small round structured viruses) of genogroup 1, which are classified as members of the Caliciviridae. It had a weak relationship (<34.5% deduced am ino acid identity) in both the polymerase and the capsid regions to animal caliciviruses, all of which have classical morphology. This is the first ge nomic data from a nonhuman virus with SRSV morphology. It confirms the hypo thesis that the bovine enteric calici-like virus NA-2 is a member of the fa mily Calioiviridae and endorses the observation to date that viruses with S RSV morphology are genomically distinct.