MS2 Phage-mediated Preparation and Immunogenicity of Chimeric Nanoparticles with Linear Epitope of Reproductive and Respiratory Syndrome Virus

  Objective   Using the protein on coat of MS2 bacteriophage as a carrier, chimeric nanoparticles with a linear epitope of porcine reproductive and respiratory syndrome virus, GP5, were constructed, and their immunogenicity determined.

  Method  The dominant neutralizing epitope gene sequence on GP5 was inserted into the MS2 protein by overlapping extension PCR. The recombinant vector was to express the chimeric protein through a prokaryotic expression system. The target protein was purified by ammonium sulfate precipitation and gel filtration chromatography followed by characterization with dynamic light scattering and electron microscopy. The immunogenicity of the constructed chimeric nanoparticles was determined by Western blot and animal immunoassay.

  Result   The linear epitope was successfully inserted into the target sequence, and the recombinant vector reached a purity greater than 85%. The purified target protein self-assembled in vitro to form uniform chimeric nanoparticles with a diameter of 25–31 nm. After immunizing animals, the chimeric particles produced a high-level of antibodies that reacted with inactivated viruses showing significant immunogenicity.

  Conclusion  The MS2 phage coat protein allowed the insertion of 9 exogenous polypeptides (the linear epitope on GP5) and self-assembled in vitro to form the chimeric virus-like particles. Each particle carried the exogenous polypeptides on the surface generating high immunogenicity. The current technology provided a new venue for building other epitopes of porcine reproductive and respiratory syndrome virus or epitopes with longer tandem.