Abstract
The sequences of ORFs 2 to 5 of five United States (US) porcine reproductive and respiratory syndrome virus (PRRSV) isolates with differing virulence were determined. The nucleotide and deduced amino acid sequences of these isolates were compared with those of other known PRRSV isolates. The amino acid sequence identity between seven US PRRSV isolates was 9199% in ORF 2, 8698% in ORF 3, 9299% in ORF 4 and 8897% in ORF 5. The low virulence US isolate had highest sequence variation in ORFs 2 to 4 compared to the other US isolates. A hypervariable region with antigenic potential was identified within the major envelope glycoprotein. Phylogenetic analysis of ORFs 2 to 7 indicated the existence of at least three minor genotypes within the major US genotype. The low virulence US isolate formed a branch distinct from the other US isolates. The results of this study have implications for both the taxonomy of PRRSV and vaccine development.
* Author for correspondence. Fax +1 515 294 1401. e-mail pspaul@iastate.edu
† Present address: Hepatitis Viruses Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.