Genetic variability of European porcine reproductive and respiratory syndrome virus (PRRSV) isolates by RT-PCR and restriction fragment length polymorphism of ORF5 gene

The objective of the present study was to evaluate the ORF5 gene genetic va riability of 11 European PRRSV field strains in comparison with the Europea n prototype Lelystad virus (LV) and the U.S. ATCC reference strain VR2332. For this purpose, we modified the method of WESLEY et al. [19, 20] based on reverse transcriptase-polymerase chain reaction (RT-PCR) and restriction f ragment length polymorphism (RFLP). The 662 bp amplified segment was cloned and sequenced from 4 European field isolates. RFLP and sequencing showed that the nucleotide sequence variability between the European field strains and Lelystad virus ranged between 87.9 and 99.8 % whereas the nucleotide sequence variability between the European field s trains and the U.S. strain VR2332 varied from 61.3 to 62.5 %. In the same w ay, the amino acid identities between the European strains field and LV, an d between the European field strains and U.S. strain VR2332 ranged between 87.6 and 100 %, and 52.4 and 54 % respectively.