Genetic variation and phylogenetic relationships of 22 porcine reproductive and respiratory syndrome virus (PRRSV) field strains based on sequence analysis of open reading frame 5.

Porcine reproductive and respiratory syndrome virus (PRRSV) strains from 13 states in the United States, Guatemala and Canada were used to compare the envelope glycoprotein gene (ORF 5) nucleotide and deduced amino acid sequences. The gene was the same size, 603 nt, for all the 22 field strains. These strains had 89-94% amino acid identity compared to reference strain VR 2332. A putative signal sequence and cleavage site between residues 31 and 32 was identified and three potential glycosylation sites were present on all but two strains. Hydrophobicity/hydrophilicity and surface probability analyses reveal a primary structure for the envelope glycoprotein (E protein) with six potential surface regions that could be antigenic sites. Similar E protein structural features are conserved for the prototype European PRRSV-Lelystad virus.