Genetic analysis of pestiviruses at the 3' end of the genome

Specific PCR primers were selected for each pestivirus genotype which flanked the 3'-part of the NS5B gene and more than three quarters of the 3'-UTR. PCR products were sequenced in both directions using an automatic sequencing device and analyzed by computer package program DNASTAR. A comparative analysis of the 3' untranslated region (3'-UTR) of 82 viruses, representing the four genotypes of the Pestivirus genus, provided a similar phylogenetic grouping as other genomic regions. Intertypic recombination was not observed, but Border disease virus (BDV) and Bovine viral diarrhoea virus type I (BVDV I) showed great intragenotypic variability. In most pestiviruses the stop codon is TGA, but BDV isolates were found to have either a TAG or a TAA stop codon. Various deletions and insertions were observed in the 3'-UTR region. Viruses of the BVDV lb group contained a characteristic deletion of 41 nucleotides. Compared to the 5'-UTR, the 3'-UTR was less conserved. The first 50-60 nucleotides were particularly variable, whilst the most conserved part was found at the 3' end of the studied region. All 82 viruses contained AT-rich stretches, the positions and sizes of which differed between the genotypes.