COMPARISON OF THE P125 CODING REGION OF BOVINE VIRAL DIARRHEA VIRUSES

The p125 (p54/p80) coding region of two cytopathic (CP) strains (Orego n and Singer) and two noncytopathic (NCP) strains (NY-1 and Draper) of bovine viral diarrhea virus (BVDV) were amplified by the polymerase c hain reaction, cloned and sequenced. The sequence data confirmed that the two CP strains do not possess any insertion or deletion in their p 125 gene as observed in many other CP strains, In the p80, which showe d a high amino acid sequence homology among all strains, no amino acid substitution could be found which distinguished these CP strains from the NCP strains NY-1 and SD-1. Many amino acid substitutions were fou nd in p54 but their individual importance in the CP phenotype is not c lear since critical domains of p54 have not yet been experimentally de fined. The p54 protein is much less conserved than p80, and sequence h omology, as well as dendrogram analysis, permitted us to distinguish t wo genotypic groups of BVDV (Ia and Ib). The mean homology between str ains of these two groups was 77.3/80.4% for the nucleic acid/amino aci d sequences while it was 88.0/88.8% and 91.6/93.3% within groups Ia an d Ib, respectively. Furthermore, we found that the p125 sequence of ou r NY-1 strain showed only 92% sequence homology with the partial p80 g ene reported for NY-1 but 99.8% homology with another partial sequence of the p125 gene of NY-1 reported elsewhere. These observations under scored the difficulty of maintaining a specific BVDV strain, especiall y the NCP biotype, in cell cultures.