Efficacy test of novel PRRSV live vaccine candidates

WGV0917(KCTC 12783BP), WGV1014(KCTC 12784BP), and WGV1107(KCTC 12785BP) were originally isolated from neonatal piglets that were shown typical PRRSV infected symptoms. These strains had genetically characterized the NA (WGV0917 and WGV1014) and EU (WGV1107) strains and culturally passaged on PAM cells for adaptation and MARC-145 cells for attenuation. This study was to compare their immunogenicity of attenuated virulent PRRSV NA and EU strains with Ingelvac MLV vaccine in guinea pigs.

Animal. A total of 12 CrlOri:HA VFA guinea pigs, 4 weeks of age. All groups of guinea pigs were inoculated by IM route. Group 1 (n=3), 2 (n=3) and 3 (n=3) were inoculated with 10^4.5 TCID₅₀ of strain WGV0917, WGV1014 and WGV1107. Group 4 (n=3) was inoculated with 10^4.9 TCID₅₀ Ingelvac MLV vaccine. Group 5 (n=3) was injected with PBS as controls. Blood was taken on 0, 7, 14, 21 and 28 days after vaccination. Serum samples were collected and stored at -70℃ before testing with VN.

PRRSV VN titer assay. VN titers were determined by SN test on MARC-145 cells. A 2-fold diluted serum sample was prepared, and an equal volume of virus solution with a titer of 200 TCID₅₀/mL was added to each dilution and incubated for 1 h at 37°C. The CPEs on the cells were analyzed for 7 days after inoculation. The VN antibody titer was defined as the reciprocal of the highest dilution that inhibited CPE in 50% of the inoculated wells.

Our results showed that WGV0917, WGV1014 and WGV1107 began to develop VN titers at DPI 7 and the titers were significantly higher as compared to those in Ingelvac MLV vaccine group.

This study indicated that all of 3 novel PRRSV vaccine candidates raised enough SN titer to protect PRRSV infection.

Disclosure of Interest: None Declared.