Electronic Thesis and Dissertation Repository

Thesis Format



Master of Science




Menassa, Rima


Agriculture and Agri-Food Canada

2nd Supervisor

Hill, Kathleen



Commercially available vaccines for porcine reproductive and respiratory syndrome virus (PRRSV) provide some control over the virus but none are ideal since they either are not completely safe for use, lack efficacy in promoting long-lasting immunity or provide no protection from heterologous PRRSV strains. Innovative approaches to designing vaccines are being pursued to overcome these drawbacks. One example is the use of nanoparticles to present a dense array of antigenic epitopes to the immune system which can effectively stimulate antibody producing cells (B cells) and T cells, resulting in long-lasting immunity. Here, I genetically fused antigenic epitopes from PRRSV to multiple self-assembling protein nanoparticles and assessed their ability to be produced recombinantly in E. coli. The most successful candidate was purified to homogeneity and demonstrated via multiple biochemical and biophysical techniques to assemble like the native nanoparticle. Immunological testing will reveal the candidate’s efficacy as a vaccine against PRRSV.

Summary for Lay Audience

The goal of my project is to produce a safe and effective vaccine for porcine reproductive and respiratory syndrome virus (PRRSV), a devastating disease in pigs that accounts for over $600 M in losses per year in the US. Commercially available vaccines for PRRSV provide some control over the virus but none are ideal since some contain damaged but living viruses that in time may cause disease in the pigs, some contain killed viruses or pieces of the virus that lack efficacy in promoting protection against the native virus both short-term and long-term, and some provide no protection against multiple strains of the virus. Vaccines containing whole viruses may be less safe but are generally more effective than vaccines containing free pieces of the virus. My approach to designing a new PRRSV vaccine that is safe and effective involves presenting specific protein sequences from the PRRS virus to the pig’s immune system in a virus-like fashion, without the virus. I will be using stable protein nanostructures as carriers for the chosen peptides from PRRSV; these nanostructures can effectively mimic the architecture of the virus while having no potential for replication. In my work, I genetically fused peptides from PRRSV that are known to stimulate the pig immune system to multiple protein nanostructures and determined their ability to be produced in and purified from a bacterial expression host. The most promising nanostructure was purified and studied using techniques that allow us to determine whether the attachment of the chosen PRRSV peptide to the nanostructure affected its assembly and stability. I demonstrated that I can successfully attach an immunoreactive peptide from PRRSV on to a very stable nanostructure and this product has the potential of being both safe as it cannot cause disease, and effective as it may stimulate a strong protective immune response against PRRSV.