Project Number: 3625-32000-108-14
Project Type: Reimbursable

Start Date: Oct 01, 2012
End Date: Oct 01, 2013

Objective:
Determine the effectiveness of utilizing subgenomic replicating PRRSV heteroclite RNAs to vector the expression of immunomodulatory cytokines as a component of a modified live vaccine preparation, as a means to increase protection from natural infection.

Approach:
We will use the infectious clone of PRRSV strain Inglevac PRRSV MLV as modified to contain DIVA epitope tags within the nsp2 coding region. In addition, cDNA clones of heteroclite RNAs (a specific type of PRRSV RNAs that are packaged within the virus and expressed when virus infects cells) will be individually modified to contain coding sequences for the immunomodulatory cytokines IL-12, IL-15 and IL-18. From these constructs, RNA transcripts will be generated and transfected into PRRSV permissible cell lines. Both full-length and heteroclite RNAs will be packaged, and the resultant virus preparation will be examined for genetic stability over multiple passages, stable expression of the vectored cytokine, as well as induction of cytokine response from primary alveolar macrophages. Upon completion of initial testing in cell culture, virus preparations will be assessed for their ability to serve as an effective vaccine as compared to the currently used IngleVac MLV strain alone. This will be done by vaccinating pigs using either the above prepared MLV/heteroclite mixture, a matched dose of IngleVac MLV or a sham innoculum, followed by a viral challenge using homologous or heterologous PRRSV strains. Protection will be assessed by monitoring weight, body temperature, viral load in serum and lung lesion scores of experimentally infected animals.