A 10-kDa structural protein of porcine reproductive and respiratory syndrome virus encoded by ORF2b

Wai Hong Wu, Ying Fang, Rachel Farwell, Melissa Steffen-Bien, Raymond R.R. Rowland, Jane Christopher-Hennings, Eric A. Nelson

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Pages (from-to)183-191
Number of pages9
Issue number1
StatePublished - Aug 15 2001
Externally publishedYes


  • Arteriviruses
  • Nidovirales
  • Open reading frame 2 (ORF2)
  • Porcine reproductive and respiratory syndrome virus (PRRSV)
  • Recombinant protein
  • Structural proteins

ASJC Scopus subject areas

  • Virology


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