The invention provides isolated
polynucleotide molecules, including plasmids; viral vectors; and transfected host cells that comprise
a DNA sequence encoding an infectious
RNA sequence encoding a North American PRRS
virus; and also North American PRRS viruses encoded thereby. The invention further provides isolated infectious
RNA molecules encoding a North American PRRS
virus. The invention also provides isolated
polynucleotide molecules, infectious
RNA molecules, viral vectors, and transfected host cells encoding genetically-modified North American PRRS viruses; and genetically-modified North American PRRS viruses encoded thereby. The invention also provides vaccines comprising such plasmids, RNA molecules, viral vectors, and North American PRRS viruses, and methods of using these vaccines in swine and in other animals. Also provided are isolated
polynucleotide molecules, viral vectors, and transfected host cells that comprise a
nucleotide sequence encoding
a peptide of a North American PRRS
virus. These viral vectors and transfected host
cell lines are useful in providing peptides to compensate for mutated
peptide coding sequences of
DNA sequences encoding genetically-modified North American PRRS viruses so that functional virions can be generated.