Characterization of the P and G types and the VP4 and VP7 gene divergence among group A bovine rotaviruses

Group A rotavirus is one of the most important etiological agents associated with neonatal calf diarrhea. The surface proteins, VP4 and VP7, are responsible for the induction of neutralizing antibodies to the virus, and determination of viral serotypes and genotypes. Types based on VP4 and VP7 are referred to as P-types and G-types, respectively. A vaccine is commercially available but is not effective in many herds. We postulated that this may be due to the incorporation of a virus in the vaccine which differs from that prevalent in the field. In this particular study, we sought to determine the relative frequency of occurrence of P and G types associated with rotaviruses isolated from calves with diarrhea and the genetic variation associated with the VP4 and VP7 genes of bovine rotaviruses (BRV).;Initially, we characterized the VP4 and VP7 genes of the BRV strain VMRI, which showed antigenic differences with the strain incorporated in the vaccine. Our results indicated that the VP4 of VMRI was different from that of the vaccine strain.;The distribution of P and G types of rotaviruses associated with calf diarrhea was determined using multiplex reverse transcription-polymerase chain reaction. Our results confirm that P(5):G6 rotaviruses are the most predominant viruses associated with calf diarrhea in the field. This is the first comprehensive study on the distribution of P types among BRV in the U.S.;Nucleotide sequence analysis of the N-terminal trypsin cleavage fragment of VP4 (VP8;Finally, during our studies on genetic variation in the VP7 gene in BRV, we have detected an isolate designated VMRI-29 in the feces of a diarrheic calf. Sequence analysis of VP7 gene of VMRI-29 showed 82% nucleotide homology and 90% amino acid identity, and differences in the variable regions with that of G6 BRV reference strains. This is the first report of a genotypic subtype among G6 type BRV outside Japan.