Molecular characterization of border disease virus, a pestivirus from sheep.

Three serologically different pestivirus strains isolated from sheep were selected for molecular analysis. cDNA and deduced amino acid sequences of the genomic regions encoding glycoproteins E1 and E2 were obtained from the three strains. A comparison with amino acid sequences of bovine viral diarrhea virus (BVDV) and classical swine fever virus (CSFV) revealed that one of the three ovine pestivirus strains can be grouped together with BVDV. The other two strains, however, were clearly different from both BVDV and CSFV. Surprisingly, the amino acid sequences from these two viruses were more similar to CSFV than to BVDV. The identity between so-called "true" BDV strains at the amino acid level is about 95% for E1 and 86% for E2 and thus similar to homologies found between CSFV strains. For one "true" BDV strain the genomic region encompassing the nonstructural protein p125 was also cloned and sequenced. The respective comparative analysis led to results which are similar to the ones obtained for the two structural glycoproteins. Taken together the data demonstrate that "true" border disease virus strains represent a separate group within the genus pestivirus.