Isolation and characterization of a new species of kobuvirus associated with cattle

Abstract

A cytopathic agent was isolated using Vero cells from the culture medium of HeLa cells that had been used for more than 30 years in our laboratory. This agent, termed U-1 strain, was serially passed in Vero cells with distinct CPE. Particles of U-1 strain negatively stained with phosphotungstic acid exhibited a distinct surface that resembled Aichi virus. The RNA genome of U-1 strain comprises 8374 nt, with a genome organization analogous to that of picornaviruses. Possible cleavage sites of the large ORF, which encoded a leader protein prior to the capsid protein region, were assigned following amino acid alignment with Aichi virus. The virus sequence had 33 and 75 % amino acid identity with the Aichi virus VP1 and 3D regions, respectively, but no more than 23 and 36 % with those of the prototype strains of other Picornaviridae. The dendrogram based on the P1, P2 and P3 proteins indicated that U-1 strain is genetically included in the genus Kobuvirus but is distinct from Aichi virus. Of 72 cattle sera, 43 (59?7 %) were positive for neutralizing antibody against U-1 strain at a titre of 1 : 8 or more. However, sera from 190 humans, 242 monkeys, 139 pigs, 5 horses, 22 dogs and 9 cats did not neutralize U-1 strain at a 1 : 4 dilution. RNA corresponding to U-1 strain was detected in 12 (16?7 %) of 72 faecal samples from cattle by RT-PCR. These results indicated that U-1 strain, suspected to be a contaminant from calf sera, is a new species of the genus Kobuvirus, now termed bovine kobuvirus.

Bovine Kobuviruses from Cattle with Diarrhea

“…Of serum samples from 72 healthy cattle, 43 (59.7%) were positive for neutralizing antibody against bovine kobuvirus U-1 standard strain at a titer of >16. In addition, 12 (16.7%) of 72 stool samples collected from the cattle were positive for the bovine kobuvirus genome by reverse transcription-PCR (RT-PCR) (1). This fi nding suggested that bovine kobuvirus is common and that the virus particles could be detected in the stool samples of infected cattle.…”

“…To date, the genus Kobuvirus consists of 2 species, Aichi virus and bovine kobuvirus (2). The Aichi virus is associated with acute gastroenteritis in humans (3)(4)(5); bovine kobuvirus infection has been detected only in cattle (1). Only 1 report has described the discovery and epidemiologic features of bovine kobuvirus (1).…”

“…The Aichi virus is associated with acute gastroenteritis in humans (3)(4)(5); bovine kobuvirus infection has been detected only in cattle (1). Only 1 report has described the discovery and epidemiologic features of bovine kobuvirus (1). Of serum samples from 72 healthy cattle, 43 (59.7%) were positive for neutralizing antibody against bovine kobuvirus U-1 standard strain at a titer of >16.…”

“…To the Editor: A new species of kobuvirus, named U-1 strain, was fi rst recognized in 2003 as a cytopathic contaminant in a culture medium of HeLa cells that had been used for >30 years in the laboratory (1). The RNA genome of the U-1 strain comprises 8,374 nucleotides; the genome organization is analogous to that of picornaviruses.…”

“…Morphologically, the U-1 strain resembles the Aichi virus, but genetically it is distinct (1). Therefore, the U-1 strain is classifi ed as a new species of genus Kobuvirus in the family Picornaviridae, and it is called bovine kobuvirus (1). To date, the genus Kobuvirus consists of 2 species, Aichi virus and bovine kobuvirus (2).…”