title: A 10-kDa structural protein of porcine reproductive and respiratory syndrome virus encoded by ORF2b.
abstract: The major structural proteins of porcine reproductive and respiratory syndrome virus (PRRSV) are derived from ORFs 5, 6, and 7. Western blots of sucrose gradient-purified virions and PRRSV-infected MARC-145 cells, probed with immune pig serum, showed the presence of an additional 10-kDa protein. Nucleotide sequence analysis of North American PRRSV isolate SDSU-23983 revealed a small ORF within ORF2, named ORF2b, which, when translated, produced a 73-amino-acid nonglycosylated protein. Recombinant 2b protein expressed by a baculovirus clone, AcVR2, comigrated with the 10-kDa virus-associated protein. The loss of 10-kDa protein immunoreactivity after absorption of immune sera with lysates from AcVR2-infected insect cells demonstrated that the 2b and 10-kDa proteins are immunologically similar. Immunoblots were also used for the detection of anti-2b activity in serum samples from experimentally infected adult pigs. Antibodies against PRRSV were apparent by 14 days postinfection, followed by anti-2b activity and serum neutralizing activity. The putative ORF2b start codon is only 6 nucleotides downstream of the adenine of the ORF2a start codon. The expression of ORF2a and 2b as enhanced green fluorescent fusion proteins showed that both proteins were translated; however, the ORF2b was preferentially expressed. These results suggest that the 2b protein is virion associated and the principal product of ORF2.
authors.affiliation: Department of Veterinary Science, South Dakota State University, Brookings, South Dakota 57007, USA.
authors.forename: W H
authors.initials: WH
authors.lastname: Wu
authors.forename: Y
authors.initials: Y
authors.lastname: Fang
authors.forename: R
authors.initials: R
authors.lastname: Farwell
authors.forename: M
authors.initials: M
authors.lastname: Steffen-Bien
authors.forename: R R
authors.initials: RR
authors.lastname: Rowland
authors.forename: J
authors.initials: J
authors.lastname: Christopher-Hennings
authors.forename: E A
authors.initials: EA
authors.lastname: Nelson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae; D001483:Base Sequence; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016366:Open Reading Frames; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics*; D011994:Recombinant Proteins / Q000737:chemistry; D018411:Spodoptera; D014162:Transfection; D015678:Viral Structural Proteins / Q000235:genetics*
chemical_list: D011994:Recombinant Proteins; D015678:Viral Structural Proteins