Replication-competent recombinant porcine reproductive and respiratory syndrome (PRRS) viruses expressing indicator proteins and antiviral cytokines

Viruses. 2012 Jan;4(1):102-16. doi: 10.3390/v4010102. Epub 2012 Jan 18.


Porcine reproductive and respiratory syndrome virus (PRRSV) can subvert early innate immunity, which leads to ineffective antimicrobial responses. Overcoming immune subversion is critical for developing vaccines and other measures to control this devastating swine virus. The overall goal of this work was to enhance innate and adaptive immunity following vaccination through the expression of interferon (IFN) genes by the PRRSV genome. We have constructed a series of recombinant PRRS viruses using an infectious PRRSV cDNA clone (pCMV-P129). Coding regions of exogenous genes, which included Renilla luciferase (Rluc), green and red fluorescent proteins (GFP and DsRed, respectively) and several interferons (IFNs), were constructed and expressed through a unique subgenomic mRNA placed between ORF1b and ORF2 of the PRRSV infectious clone. The constructs, which expressed Rluc, GFP, DsRed, efficiently produced progeny viruses and mimicked the parental virus in both MARC-145 cells and porcine macrophages. In contrast, replication of IFN-expressing viruses was attenuated, similar to the level of replication observed after the addition of exogenous IFN. Furthermore, the IFN expressing viruses inhibited the replication of a second PRRS virus co-transfected or co-infected. Inhibition by the different IFN subtypes corresponded to their anti-PRRSV activity, i.e., IFNω5 ° IFNα1 > IFN-β > IFNδ3. In summary, the indicator-expressing viruses provided an efficient means for real-time monitoring of viral replication thus allowing high‑throughput elucidation of the role of host factors in PRRSV infection. This was shown when they were used to clearly demonstrate the involvement of tumor susceptibility gene 101 (TSG101) in the early stage of PRRSV infection. In addition, replication‑competent IFN-expressing viruses may be good candidates for development of modified live virus (MLV) vaccines, which are capable of reversing subverted innate immune responses and may induce more effective adaptive immunity against PRRSV infection.

Keywords: host factors; indicator proteins; porcine arterivirus; tumor susceptibility gene 101; type I interferon; virus cDNA infectious clone.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cytokines / genetics
  • Cytokines / physiology*
  • DNA, Complementary / genetics
  • DNA, Viral / genetics
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / physiology
  • Endosomal Sorting Complexes Required for Transport / genetics
  • Endosomal Sorting Complexes Required for Transport / physiology
  • Genes, Reporter
  • Genes, Synthetic
  • Host-Pathogen Interactions
  • Immune Evasion
  • Interferons / biosynthesis
  • Interferons / genetics
  • Interferons / physiology
  • Porcine Reproductive and Respiratory Syndrome / immunology
  • Porcine Reproductive and Respiratory Syndrome / prevention & control
  • Porcine Reproductive and Respiratory Syndrome / virology
  • Porcine respiratory and reproductive syndrome virus / genetics
  • Porcine respiratory and reproductive syndrome virus / physiology*
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Fusion Proteins / physiology
  • Sus scrofa / immunology
  • Swine
  • Transcription Factors / genetics
  • Transcription Factors / physiology
  • Vaccination
  • Viral Proteins / physiology*
  • Viral Vaccines
  • Virus Replication*


  • Cytokines
  • DNA, Complementary
  • DNA, Viral
  • DNA-Binding Proteins
  • Endosomal Sorting Complexes Required for Transport
  • Recombinant Fusion Proteins
  • Transcription Factors
  • Tsg101 protein
  • Viral Proteins
  • Viral Vaccines
  • Interferons