A Multiepitope Mosaic DNA PRRSV Vaccine is Immunogenic in Pigs and Confers a Partial Level of Protection Against Challenge Virus

Abstract A Multiepitope Mosaic DNA vaccine was tested in pigs for immunogenicity and protection from PRRS virus challenge. Mosaic coding sequences were synthesized and cloned into pHCMV-1 and their expression was confirmed. Vaccination challenge trial in PRRSV-free piglets followed using Mosaic DNA in lipid nanoparticles. Group 1 received Empty/LNP and served as negative vehicle controls; Group 2 received pooled Mosaic DNA/LNP vaccine; Group 3 received a commercial MLV vaccine and served as positive controls. A virus challenge was implemented by 40 days after vaccination began and euthanasia was implemented 11 or 12 days later. Virus specific antibodies detected in Mosaic DNA/LNP vaccinated pigs by ELISA were significantly higher than those in Empty/LNP controls before and after challenge. Virus neutralizing antibodies were detected in Mosaic DNA/LNP vaccinated pigs but not in controls. IFN\(\:ᵧ\) expression was detected in Mosaic DNA/LNP vaccinated animals and Empty/LNP group remained unresponsive. Viral loads in serum of the Mosaic DNA/LPN group, while not statistically significant, were lower than Empty/LPN pigs. The viral levels remained high in sera of control animals. Lower, but not statistically significant, viral loads were detected in, bronchoalveolar lavage, and tissues in the Mosaic DNA/LNP vaccine group than in the controls confirming level of protection.