Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan - “Porcine adenovirus 3 based vaccine for porcine respiratory and reproductive syndrome (PRRS)”

Project Summary
Vaccination of animals is one of the ways to reduce the losses from infectious diseases. One of the impediments to developing better vaccines is Delivery. Subunit vaccines require strong adjuvants (a few are licensed), often do not induce the breadth of immunity required (cell mediated, mucosal immunity etc.) and are not economical to produce for use in Veterinary Medicine. As compared to sub-unit vaccines, live vaccines are the better inducers of mucosal immunity when administered orally or intranasally. In addition, production of live vaccines is cost effective. However, use of live vaccines produced by conventional means ensures that the live organism is always present in the animals, which presents the possibility of it reverting back to a virulent form (in vivo recombination) and cause fatal disease. Thus, new approaches have to be developed for the safe and cost effective production of viral vaccines. One way to achieve this is to develop live vectored vaccines. Such live vectors can be engineered to carry genes for the antigens of other pathogens thus making it possible to immunize swine and produce protective immunity at the mucosal surface to several disease organisms at one time. This will not only improve vaccination, but will also reduce the cost of producing vaccines. This research will evaluate porcine adenovirus-3 (PAV-3) as a vector for the development of live vectored vaccines for pigs.

Project Objective
This project will entail construction of synthetic PRRSV genes capable of being expressed in a recombinant PAV-3 vector. This vector will then be administered to pigs and assessed for its ability to induce a protective immune response.

Relevance to NPB PRRS Initiative Research Objectives
PRRS virus, a positive strand RNA virus related to members of the of Arteriviridae family, is the causative agent of devastating disease of swine causing severe respiratory distress in young pigs and abortions in the last term of gestation. Six putative structural proteins have been identified and named ORF 2 to ORF 7. Of these, ORF 5 glycoprotein contains PRRS virus neutralizing epitopes. Both ORF 3 and ORF 5 have been suggested to be candidates for a recombinant-type vaccine. Current modified live and killed vaccines have some success, although differentiation between vaccinated and infected animals has been a problem. It is believed that mucosal immunity plays role in protection against PRRSV infection, virus persistence and shedding. One way to induce better mucosal immunity is by developing viral vectored vaccines.