Open reading frame 2 of porcine circovirus type 2 encodes a major capsid protein

• Published in: Journal of general virology 2000-09, Vol.81 (9), p.2281-2287
• Main Authors: Nawagitgul, Porntippa, Morozov, Igor, Bolin, Steven R, Harms, Perry A, Sorden, Steven D, Paul, Prem S
• Format: Article
• Language: English
• Subjects: Animals; Baculoviridae; Baculovirus; Capsid - genetics; Cells, Cultured; Circovirus - genetics; Cloning, Molecular; DNA Helicases - genetics; DNA Replication; DNA-Binding Proteins; Electrophoresis, Polyacrylamide Gel; Molecular Weight; multisystemic wasting syndrome; Open Reading Frames - genetics; ORF1 protein; ORF2 protein; Porcine circovirus 2; Spodoptera; Swine; Trans-Activators - genetics; Viral Proteins - genetics; Viral Structural Proteins - genetics
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/0022-1317-81-9-2281

Department of Veterinary Microbiology and Preventive Medicine 1 , Department of Veterinary Diagnostic and Production Animal Medicine 2 , and Veterinary Medical Research Institute (VMRI) 3 , Iowa State University, 1802 Elwood Drive, Bldg 6, Ames, IA 50011-1240, USA Viral and Prion Diseases of Livestock Research Unit, National Animal Disease Center, ARS, USDA, Ames, Iowa, USA 4 Author for correspondence: Prem Paul. Fax [phone]. e-mail pspaul{at}iastate.edu Porcine circovirus 2 (PCV2), a single-stranded DNA virus associated with post-weaning multisystemic wasting syndrome of swine, has two potential open reading frames, ORF1 and ORF2, greater than 600 nucleotides in length. ORF1 is predicted to encode a replication-associated protein (Rep) essential for replication of viral DNA, while ORF2 contains a conserved basic amino acid sequence at the N terminus resembling that of the major structural protein of chicken anaemia virus. Thus far, the structural protein(s) of PCV2 have not been identified. In this study, a viral structural protein of 30 kDa was identified in purified PCV2 particles. ORF2 of PCV2 was cloned into a baculovirus expression vector and the gene product was expressed in insect cells. The expressed ORF2 gene product had a molecular mass of 30 kDa, similar to that detected in purified virus particles. The recombinant ORF2 protein self-assembled to form capsid-like particles when viewed by electron microscopy. Antibodies against the ORF2 protein were detected in samples of sera obtained from pigs as early as 3 weeks after experimental infection with PCV2. These results show that the major structural protein of PCV2 is encoded by ORF2 and has a molecular mass of 30 kDa.