title: Viable porcine arteriviruses with deletions proximal to the 3' end of the genome.
abstract: In order to obtain attenuated live vaccine candidates of porcine reproductive and respiratory syndrome virus (PRRSV), a series of deletions was introduced at the 3' end of the viral genome using an infectious cDNA clone of the Lelystad virus isolate. RNA transcripts from the full-length cDNA clones were transfected into BHK-21 cells. The culture supernatant of these cells was subsequently used to infect porcine alveolar macrophages to detect the production of progeny virus. It is shown that C-terminal truncation of the nucleocapsid (N) protein, encoded by ORF7, was tolerated for up to six amino acids without blocking the production of infectious virus. Mutants containing larger deletions produced neither virus nor virus-like particles containing viral RNA. Deletion analysis of the 3' UTR immediately downstream of ORF7 showed that infectious virus was still produced after removal of seven nucleotides behind the stop codon of ORF7. Deletion of 32 nucleotides in this region abolished RNA replication and, consequently, no infectious virus was formed. Serial passage on porcine alveolar macrophages demonstrated that the viable deletion mutants were genetically stable at the site of mutation. In addition, the deletions did not affect the growth properties of the recombinant viruses in vitro, while their antigenic profiles were similar to that of wild-type virus. Immunoprecipitation experiments with the six-residue N protein-deletion mutant confirmed that the truncated protein was indeed smaller than the wild-type N protein. The deletion mutants produced in this study are interesting candidate vaccines to prevent PRRS disease in pigs.
authors.affiliation: Department of Infectious Diseases and Food Chain Quality, Institute for Animal Science and Health, Lelystad, The Netherlands1.
authors.forename: M H
authors.initials: MH
authors.lastname: Verheije
authors.affiliation: Department of Infectious Diseases and Food Chain Quality, Institute for Animal Science and Health, Lelystad, The Netherlands1.
authors.forename: M V
authors.initials: MV
authors.lastname: Kroese
authors.affiliation: Virology Division, Department of Infectious Diseases and Immunology, Veterinary Faculty, Utrecht University, Utrecht, The Netherlands2.
authors.forename: P J M
authors.initials: PJM
authors.lastname: Rottier
authors.affiliation: Department of Infectious Diseases and Food Chain Quality, Institute for Animal Science and Health, Lelystad, The Netherlands1.
authors.forename: J J M
authors.initials: JJM
authors.lastname: Meulenberg
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D016679:Genome, Viral; D016676:Macrophages, Alveolar / Q000821:virology; D008969:Molecular Sequence Data; D019590:Nucleocapsid Proteins / Q000737:chemistry / Q000235:genetics; D016366:Open Reading Frames; D019318:Porcine Reproductive and Respiratory Syndrome / Q000821:virology; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics* / Q000254:growth & development* / Q000472:pathogenicity; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D013552:Swine; D014162:Transfection
chemical_list: D020413:3' Untranslated Regions; D018076:DNA, Complementary; D019590:Nucleocapsid Proteins