Novel Structural Protein in Porcine Reproductive and Respiratory Syndrome Virus Encoded in an Alternative Open Reading Frame 5 Present in All Arteriviruses

February 16, 2011 — 

Porcine reproductive and respiratory syndrome virus (PRRSV) is an arterivirus that emerged in the late 1980's in both Europe and North America as the causative agent of PRRS, now the most important disease of swine worldwide. Despite extensive characterization of PRRSV proteins by direct analysis and comparison to other arteriviruses, determinants of virulence, pathogenesis and protective immune recognition remain poorly understood. Thus, we hypothesized that additional open reading frames (ORFs) are present in the PRRSV genome that may contribute to its biological properties, and so screened highly purified virions of the strain VR2332, the prototype type 2 PRRSV, for evidence of novel polypeptides. A 51 amino acid polypeptide was discovered that is encoded in an alternative ORF of the subgenomic mRNA encoding the major envelope glycoprotein, GP5, and is incorporated into virions. The protein, referred to as ORF5a protein, is expressed in infected cells and pigs infected with PRRSV express anti-ORF5a protein antibodies. A similar ORF is present as an alternative reading frame in all PRRSV sgmRNA5 and in all other arteriviruses, suggesting that this ORF5a protein plays a significant role in arterivirology. Its discovery also provides a new potential target for immunological and pharmacological intervention in PRRS.

Johnson CR, Griggs TF, Gnanandarajah JS, Murtaugh MP; Novel Structural Protein in Porcine Reproductive and Respiratory Syndrome Virus Encoded in an Alternative Open Reading Frame 5 Present in All Arteriviruses ; J Gen Virol. 2011 Feb 9. [Epub ahead of print] doi:10.1099/vir.0.030213-0