Location: Virus and Prion Research2013 Annual Report
1a. Objectives (from AD-416):
The objective of this cooperative research project is to characterize selected laboratory and field mammalian virus isolates for the purpose of utilizing this knowledge to develop novel improved prevention and control programs of swine diseases.
1b. Approach (from AD-416):
Delivery of vaccines through the mucosal route offers several practical and clinical advantages over the parenteral route including ease and cost of administration through oral or aerosol delivery, as well as the capacity to induce widely protective mucosal and systemic immunity. However, mucosal vaccines must be able to overcome several obstacles in order to be effective including the ability to survive enzymatic degradation and low pH during delivery, the capacity to be targeted to sites of immune function, and the ability to elicit a strong immune response. Mammalian orthoreovirus (MRV) is a clinically benign member of the Reoviridae family of dsRNA viruses. MRV is specifically targeted to mucosal sites of immune function through binding of the viral attachment protein to epithelial M cells. Following binding, the virus moves into the subepithelial cells of the mucosa, where it infects cells, eliciting a strong mucosal and systemic immune response. Recently, a reverse genetics technique was developed for MRV, which for the first time allows for the in vitro construction of MRV particles that are able to express non-viral RNA during infection. We hypothesize that based on its natural properties, MRV will make an ideal vector for the development of orally administered mucosal vaccines which are naturally targeted to sites of immune function to express immunogenic proteins from a variety of infectious agents and elicit a strong mucosal and systemic immune response. In this project, we will utilize the newly described MRV reverse genetics technique to create a universal MRV vaccine vector system, and provide a proof of concept for the vector system using the swine influenza virus HA protein. This cooperative agreement between the ARS's National Animal Disease Center (NADC) and Iowa State University, College of Veterinary Medicine, is to collaborate on in vivo and in vitro characterization of laboratory and field orthoreovirus isolates. The research will focus on studies that will 1) characterize viruses at a genetic level, 2) develop a reverse genetics system, and 3) use this reverse genetics system to study the efficacy of this vector to induce protective immunity against disease caused by swine viruses such as swine influenza viruses (SIV), porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2).
3. Progress Report:
This project is in support of Subobjective 2.3A "Novel viral vectors expressing HA genes will induce protection against experimental challenge in the host." Developing a novel viral vector is a multi-step process beginning with constructing a clone of the viral vector, followed by the introduction of a foreign gene into the vector, the stable expression of the foreign gene, and the final step is a proof of concept study to demonstrate vaccine protection. Although a clone of a mammalian reovirus has been constructed and used to produce infectious virus with a reverse genetics system, we have not been able to introduce a stable foreign gene (hemaggluntinin gene from swine influenza virus) into the clone. Different approaches are being attempted to work around this difficulty. Once the foreign gene is expressed in the viral vector, proof-of-concept vaccine study will be completed.