Determination of 5 '-leader sequences from radically disparate strains of porcine reproductive and respiratory syndrome virus reveals the presence ofhighly conserved sequence motifs

We determined the untranslated 5'-leader sequence for three different isola tes of porcine reproductive and respiratory syndrome virus (PRRSV): pathoge nic European- and American-types, as well as an American-type vaccine strai n. 5'-leader from European- and American-type PRRSV differed in length (220 and 190 nt, respectively), and exhibited only approximately 50% nucleotide homology. Nevertheless, highly conserved areas were identified in the lead er of all 3 PRRSV isolates, which constitute candidate motifs for binding o f protein(s) involved in viral replication. These comparative data provide a priori knowledge for mutational identification of virulence determinants in the 5' nontranslated part of the PRRSV genome.