ARS | Publication request: Virion packaging of multiple cleavage isoforms of porcine reproductive and respiratory syndrome virus nonstructural protein 2

Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 14, 2012
Publication Date: July 25, 2012
Citation: Kappes, M.A., Faaberg, K.S. 2012. Virion packaging of multiple cleavage isoforms of porcine reproductive and respiratory syndrome virus nonstructural protein 2 [abstract]. American Society for Virology 31st Annual Meeting. p. 161-162.

Technical Abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) is the cause of a complex disease often resulting in significant morbidity and mortality. Recently, highly pathogenic isolates have emerged which have proven to be devastatingly effective pathogens, resulting in rapid systemic deterioration of the host. PRRSV exhibits a profound ability to evolve in response to immunological pressures by both mutation and recombination events. Due to the substantial genetic heterogeneity between strains, identifying the underlying molecular mechanisms utilized by PRRSV to support infection has been challenging. The replicase nonstructural protein 2 (nsp2) is both the largest and the most genetically diverse viral protein. Nsp2 is a multidomain protein, with a recognized Ovarian Tumor (OTU)-domain protease (PLP2) near its N-terminus, a long stretch of hypervariable amino acids, a transmembrane region and a relatively conserved C-terminal domain. The function(s) of nsp2 have not been well defined but are believed to include proteolytically cleaving the nsp2-nsp3 junction, a suspected deubiquitinating activity, a role as a scaffolding protein supporting the replication machinery, as well as antagonistic immunomodulatory properties targeting the innate immune system. Our investigation of highly purified PRRSV revealed the identification of nsp2 within the virion of multiple diverse strains by both immunoelectron microscopy (IEM) and western blot analysis. Western blot analysis identified cleavage isoforms between approximately 120kDa to 50kDa packaged into the virion of multiple strains. IEM and western blot results were consistent across genetically diverse strains including European Type 1 and the North American Type 2 prototype strains Lelystad and VR-2332 respectively, as well as highly pathogenic Asian strains JXwn06 and SRV-07. The strong antigenicity of nsp2 has been shown to result in the generation of significant a-nsp2 antibody titers in vivo. The identification of nsp2 incorporation into the virion may partially explain the selective pressure underlying the robust plasticity of nsp2. This represents the first report of the incorporation of nsp2 within the PRRSV virion.